Epidemiology

Although the incidence of tuberculous spondylitis has decreased dramatically in recent years, the incidence of pyogenic vertebral osteomyelitis appears to have increased.^15,16 Various reports have stated that vertebral osteomyelitis represents 2% to 7% of all cases of osteomyelitis.^17–20 The disease may occur from infancy to old age but has a predilection for the elderly.^{15,19,21–30} Approximately one half of the patients with spine infections are more than 50 years old and two thirds are male.²⁹ The incidence may be higher in younger patients who are intravenous (IV) drug abusers.²

Etiology

Any condition that causes a bacteremia may lead to hematogenous vertebral osteomyelitis. The most frequent sources are urinary tract infections and the transient bacteremia caused by genitourinary procedures.^{16,22,24,28,31–33} Of 198 cases in the literature in which the probable source of infection was noted, it was the genitourinary tract in 29%, soft tissue infections in 13%, and respiratory tract infections in 11%; 1.5% of the infections occurred in IV drug abusers,²⁹ but this association is being reported with increasing frequency.^29,34–39 Vertebral osteomyelitis may also be caused by direct inoculation of bacteria into the spine by penetrating wounds, spine surgery, chemonucleolysis, or discography.^29,40–49 The source of infection could not be identified in 37% of cases.²⁹ Immunocompromised hosts appear to be particularly susceptible to spine infections.^22,29,31,33 In particular, diabetics have a high incidence of vertebral osteomyelitis.^16,21,31,50 Those who are human immunodeficiency virus (HIV) positive are also predisposed to develop spinal infections even when IV drug users are eliminated from the study group.⁵¹ In a recent series of 253 patients from the Cleveland area, 33% of infections were acquired in the hospital. In total, 51% of patients had predisposing extravertebral infections with most due to hematogenous spread from urinary tract, skin and subcutaneous tissues, infected vascular access sites, endocarditis, and bursitis of septic arthritis.⁵² Kulowski thought that trauma was a predisposing factor in pyogenic vertebral osteomyelitis.²⁷ More recent studies have not supported that association.^2,28,31 In Sapico and Montgomerie’s²⁹ review of 207 literature cases in which the presence or absence of blunt trauma was discussed, in only 5% was there a history of trauma.

Bacteriology

In 1931 Hatch reviewed the literature and reported that the causative organism was almost exclusively Staphylococcus aureus.⁵³ There has been an increase in the number of gram-negative bacillary infections.²⁴ In the series from Cleveland, gram-negative bacilli accounted for 23% of infections.⁵² From data reported in the postantibiotic era, Sapico and Montgomerie²⁹ found that 67% of 222 patients were infected with gram-positive aerobic cocci; S. aureus constituted 55% of the total. The emergence of tolerant S. aureus is a concern, and such strains may become more prevalent with the widespread use of antibiotics.⁵⁴ The most frequently isolated gram-negative organisms are Escherichia coli, Pseudomonas species, and Proteus species. These are frequently found in association with genitourinary tract infection.^{24,31,32,55–57} Pseudomonas aeruginosa is frequently isolated from heroin abusers.^{34,36,38,58–60} In a review of 67 reported cases, gram-negative aerobic bacilli were isolated in 82% of the cases and Pseudomonas was the pathogen in 66%.³⁸ However, one series included 15 IV drug abusers with pyogenic vertebral osteomyelitis and all 11 with positive cultures were infected with S. aureus.²² The likelihood of isolating an organism in the blood is most likely when fever is present. In the absence of a fever, bacteremia can only be detected in 21% of patients.⁵²

Salmonella osteomyelitis is uncommon. It generally occurs after an acute intestinal infection, but the interval between the gastroenteritis and the onset of osteomyelitis may be quite long⁶¹; in some cases, no previous infection can be identified.⁶² Salmonella has a strong tendency to localize in tissues where there is preexisting disease.^61,63 Infection with anaerobic bacteria is unusual and is generally associated with foreign bodies, open fractures, infected wounds, diabetes, or human bites.^29,64

Infection caused by multiple organisms is encountered in up to 8% of cases.^29,65 Infection with Haemophilus species has been reported but is extremely rare in adults.^66,67 Low-virulence organisms such as diphtheroids and coagulase-negative staphylococci may cause indolent infections with delayed diagnosis.⁶⁸ These organisms may grow slowly and cultures should be held for 10 days before they are considered to be negative. Low-virulence organisms should not be dismissed as contaminants in patients suspected clinically to have vertebral osteomyelitis.⁶⁸ In one series of 111 cases of pyogenic vertebral osteomyelitis, low-virulence organisms caused 48% of the infections in the 61 patients who were 60 years of age or older and 55% of the 44 patients who had an impaired immune system.²²

Pathogenesis/Pathology

Although the nucleus pulposus is an avascular tissue, it is relatively active metabolically.⁶⁹ It receives its nutrition via diffusion across the endplates and from blood vessels at the periphery of the annulus fibrosus.⁶⁹ In the developing spine, orderly arranged cartilage canals within the endplate contain vascular organs resembling glomeruli.^70,71 Earlier studies suggested that blood vessels penetrate the nucleus pulposus in human fetuses and neonates.⁷² However, elegant studies by Whalen and colleagues⁷¹ demonstrated that the nucleus pulposus is always avascular. Coventry and colleagues⁷³ demonstrated that, after birth, the cartilage endplates become progressively thinner and the vessels within the cartilage canals become obliterated. Some persist up to age 30 years, but by adulthood most of the vessels within the endplate itself have disappeared.⁷³

Wiley and Trueta⁷⁴ demonstrated the rich arterial anastomosis within the vertebral body, with end arterioles in the metaphyseal region. Spinal arteries enter the canal through the intervertebral foramen at the level of the disc. Branches ascend and descend, supplying the vertebral bodies above and below. Through their injection studies, Wiley and Trueta demonstrated how bacteria could easily spread hematogenously to the metaphyseal region of adjacent vertebrae. The infection may also start in the metaphyseal region of one vertebra and either spread across the avascular disc by lysosomal destruction of the nucleus pulposus or through vessels anastomosing on the periphery of the annulus fibrosus.⁷⁴

It has been suggested that Batson’s plexus may be the route of hematogenous spread of infection. Batson demonstrated, in injection studies, that dye flows into the valveless vertebral venous plexus when pressure is applied to the lower abdominal wall.⁷⁵ The distribution of veins within the vertebral body is an arborization of vessels. Minute tributaries draining the metaphyseal region empty into large, valveless, venous channels that drain into the loose plexus lining the canal. Wiley and Trueta demonstrated that it takes considerable force to fill the small metaphyseal vessels in a retrograde fashion, compared with the ease of injection of the metaphyseal arterioles; this suggests that the former is an unlikely route of hematogenous seeding.⁷⁴

Once microorganisms lodge in the low-flow vascular arcades in the metaphysis, infection spreads. The disc is destroyed by bacterial enzymes in a manner similar to the destruction of cartilage in septic arthritis. This is in contrast to tuberculous infections (described later), in which the endplates and bone are destroyed but the disc is frequently better preserved.⁷⁶ In children, the cartilage canals allow microorganisms nearly direct access to the disc, which probably explains the clinical differences between spine infections in children and adults. In adults, disc space infection may occur by direct inoculation of the disc as a result of surgery, chemonucleolysis, or discography but is unlikely to occur spontaneously.^77,78

Some authors have suggested that discitis in adults is a separate entity from vertebral osteomyelitis.^26,79 Ghormley and colleagues^26,79 stressed the benign nature of this variation, but in Kemp and colleagues’²⁶ series the disease was quite severe with a high rate of irreversible paralysis. It is conceivable that adult discs could receive blood directly through persistent vascular channels in the endplate, degenerative defects in the endplate, or vessels anastomosing on the peripheral annulus fibrosus and perhaps gaining access through rents in the annulus. If adult discitis occurs at all, it appears that hematogenous involvement of the metaphysis is far and away the most common mechanism and, whether the infection begins in the metaphysis and spreads across the disc or vice versa, the clinical manifestations and treatment are the same.

The upper cervical spine has a peculiar blood supply. Parke and colleagues⁸⁰ have demonstrated a venous plexus around the odontoid, called the “pharyngeal vertebral vein,” which frequently has lymphovenous anastomoses. This venous plexus may be responsible for hematogenous spread to the upper cervical spine.^80,81 Abscesses may drain into the soft tissues surrounding the spine or into the spinal canal itself. In the cervical spine, a retropharyngeal abscess may invade the mediastinum.^27,82 In the thoracic spine, an abscess may be paraspinous or retromediastinal.²⁷ Infection in the lumbar spine may cause a psoas abscess or, less commonly, an abscess pointing through Petit triangle.²⁷ Occasionally, an abscess may create a tract through the greater sciatic foramen and appear in the buttock beneath the piriformis fascia, in the perirectal region, or even in the popliteal fossa.²⁷ The more virulent organisms may not follow fascial planes and may extend into visceral structures. They also are more likely to produce spinal deformity. An abscess that enters the spinal canal is considered to be an epidural abscess and is discussed later. Infection may cross the dura, causing a subdural or intradural abscess or meningitis.^27,83

The pathogenesis of neural compromise may be related to direct compression by epidural pus, granulation tissue, or bone and disc from the development of spinal deformity and instability. In addition, the cord or nerve roots may suffer ischemic damage from septic thrombosis or may be damaged by inflammatory infiltration of the dura (Figs. 86-1 and 86-2).^26,27,29

FIGURE 86–1 This patient with a T7-T8 disc space infection with associated vertebral osteomyelitis developed progressive paraplegia and died as a result of overwhelming sepsis associated with antibiotic-induced neutropenia. A, Lateral radiograph showing marked narrowing and sclerosis at the T7-T8 interspace. B, Artist’s rendition of the pathology shows the collapse centered at the T7-T8 interspace and associated paraspinal abscess. C, Two months later, infection spread down to the T9-T10 interspace, with marked narrowing at that level. Gross destruction of the disc can be seen on this gross pathology specimen at the T7-T8, T8-T9, and T9-T10 levels. D, This microscopic section of the spinal cord has been taken at 11.5× normal magnification. The dorsal aspect of the spinal cord is at the top of this figure. The patient was completely paraplegic. This is consistent with the changes seen within the spinal cord

(Courtesy of Dr. H.H. Bohlman, Cleveland, Ohio.)

FIGURE 86–2 This patient died with thoracic vertebral osteomyelitis secondary to overwhelming meningitis associated with the spine infection. A, The patient developed a T7-T8 disc space infection with associated vertebral osteomyelitis following a urologic operation with associated postoperative sepsis. He was treated initially with oral antibiotics. B, One month later, there is an obvious increasing kyphosis secondary to the spine infection. The patient is still being mobilized despite this deformity. C, This anteroposterior roentgenogram at the time of transfer to our institution reveals a large paraspinous abscess (arrowheads). At this time the patient had an incomplete paraplegia. D, This lateral intraoperative roentgenogram demonstrates gross instability of the thoracic spine with the T7 vertebra 50% retrolisthesed on the T8 vertebra. At this time the patient still had an incomplete paraplegia. Surgery was undertaken in order to drain the paraspinal abscess. E, This drawing shows the extent of destruction at the T7-T8 interspace. The retrolisthesis of T7 on T8 is well demonstrated. The paraspinous abscess is also clearly shown. F, The gross destruction of the anterior vertebral column is well demonstrated in this pathology specimen. G, This transverse section of the spinal cord has been magnified 11.5 times. Although there are significant changes within the neural tissue, this patient had an incomplete paraplegia at the time of death.

(Courtesy of Dr. H.H. Bohlman, Cleveland, Ohio.)

An unusual association between vertebral osteomyelitis and compression fractures secondary to osteoporosis has been described. It is theorized that the osteomyelitis may develop as a complication of the fracture because the fracture creates a favorable environment for the hematogenous infection. Alternatively, the osteomyelitis may develop within the central portion of an osteoporotic vertebral body, perhaps because the bone is more hyperemic or because of vascular stasis. Infection may then lead to a pathologic fracture of the vertebra without the usual involvement of the disc space.⁸⁴

Clinical Presentation

The clinical manifestations of spine infection are determined by the virulence of the organism and the resistance of the host. The presentation may be acute, subacute, or chronic.^26,27 Before the antibiotic era, most patients had acute osteomyelitis, and in 68% of the cases the disease was fulminant with severe toxemia.⁵³ The mortality rate ranged from 25% to 71%.^27,53 A literature review in 1979 found that only 20% of the patients had symptoms for less than 3 weeks before presentation, 30% had them for 3 weeks to 3 months, and 50% had them for longer than 3 months.²⁹ Greater awareness of the disease and improved diagnostic modalities (especially magnetic resonance imaging [MRI]) have shortened the delay in diagnosis. In one series reported in 1997, 68 of 111 patients were diagnosed within 28 days of the onset of their symptoms and only 8 patients were diagnosed more than 3 months after their symptoms began.²² In an urban setting, the infection is discovered within 1 month in only 28% and the median time to diagnosis is 1.8 months.⁵²

Fever is present in only 52% of the patients overall; pain in the back or neck is a much more common finding, occurring in approximately 90% of patients.²⁹ Patients with acute infection present with fever, local spine pain, severe muscle spasm, and limitation of motion of the spine. With lumbar spine involvement, there may be a positive straight-leg raise test, reluctance to bear weight, and hip flexion contracture due to psoas irritation. Hamstring tightness and loss of lumbar lordosis may be noted. Torticollis and fever may be the only presenting signs with cervical osteomyelitis.^81,85

Subacute and chronic infections may be much more insidious, and these patients have a vague history. Pain may be the only symptom, especially with an occult infection by a low-virulence organism.⁶⁸ Approximately 15% of the patients have atypical symptoms such as chest pain, abdominal pain, hip pain, radicular symptoms, or meningeal irritation.^16,29,86 These unusual and often vague complaints have led to unnecessary exploratory laparotomies before the diagnosis has been made.^29,86 A significant delay in diagnosis is common with chronic infections.^{16,21,23–25,29,87,88}

Vertebral osteomyelitis is more common in the lumbar region. In Sapico and Montgomerie’s²⁹ literature review, in 48% of 294 cases the involvement was lumbar, in 35% thoracic, in 6.5% cervical, and in approximately 5% thoracolumbar and lumbosacral. Vertebral osteomyelitis at noncontiguous levels is uncommon (Fig. 86–3). With the advent of antibiotics, significant spine deformity is not as common as it was in the past, but significant kyphosis still may occur.^24,27

FIGURE 86–3 Although this is uncommon, some patients present with vertebral osteomyelitis at noncontiguous levels. This diabetic patient had an infection of the cervical spine, as well as the lumbar spine secondary to Staphylococcus aureus. A, The patient has an obvious disc space infection at L2-L3, with an associated vertebral osteomyelitis. B, This lateral roentgenogram of the cervical spine demonstrates a disc space infection at C5-C6 with destruction of the adjacent bone. The patient had a quadriparesis as a result of this infection.

Abscesses are not encountered as frequently now as they were before the antibiotic era but should still be sought, in the paraspinous region, psoas region, and in remote areas.²⁷ A tender or pulsatile abdominal mass may be caused by a mycotic aneurysm, a dilatation of the wall of an artery resulting from an infection.⁸⁹ In the lumbar spine, abscesses in the psoas muscle are common and help to distinguish spinal infections from other lesions such as tumors or trauma (Fig. 86–4).

FIGURE 86–4 T1 contrast-enhanced magnetic resonance axial image through lumber spine. Increased signal intensity can be seen diffusely in the psoas muscle bilaterally with low signal intensity abscess pockets (white arrowheads).

Approximately 17% of the patients present with a neurologic deficit secondary to nerve root or spinal cord involvement.²⁹ Eismont and colleagues identified several factors that predisposed patients to paralysis including diabetes,^16,27,50,90 rheumatoid arthritis,⁹⁰ increased age,^90,91 and a more cephalad level of infection.^37,90 Patients on systemic steroid therapy are more likely to be paralyzed, and those infected with S. aureus seem to have the most severe degree of paralysis.⁹⁰ Some authors have noted that neurologic involvement is uncommon in patients infected with Pseudomonas.^58,60

Infants and IV drug abusers are two subsets of patients who have slightly different presentations. Infants generally present acutely with high temperature, septicemia, and generalized signs of systemic illness.^91,92 The radiographic findings of vertebral osteomyelitis in infants is striking, with almost complete dissolution of the involved vertebral bodies and nearly normal adjacent endplates. The late radiographic appearance may be identical to that of congenital kyphosis (Fig. 86–5). Heroin abusers also present earlier than most patients. In a review of the literature, 81% of heroin abusers presented within 3 months after the onset of their symptoms, compared with 50% in the general population with vertebral osteomyelitis.^29,38,91,92 The authors postulated that the earlier presentation may be related to infection with more virulent organisms or the fact that their patients have less tolerance to pain or may be using their back pain as an excuse to receive more narcotics (Fig. 86–6).³⁸

FIGURE 86–5 This infant developed a vertebral osteomyelitis and life-threatening sepsis. Unlike the relatively benign disc space infection of childhood, this infection of infancy follows a much more destructive course. A, At the time the infant became septic, the T6 vertebral body could be clearly visualized (arrow). B, Two months later, despite aggressive antibiotic treatment, there is gross destruction of the T6 vertebral body (arrow). C, This lateral roentgenogram taken 2.5 years after the spine infection reveals that the patient has a kyphotic deformity from T5-T7. This deformity behaves much like an anterior failure of formation of the T6 vertebral body.

(From Eismont FJ, Bohman, HH, Soni PL, et al: Vertebral osteomyelitis in infants. J Bone Joint Surg Br 64:32-35, 1982.)

FIGURE 86–6 Computed tomography scan with sagittal (A) and axial (B) images of the lumbar spine of an active intravenous drug abuser. Severe destruction of L5 can be seen. The patient presented with severe back pain, bilateral dorsiflexor weakness, and fever. The L5 vertebral body and the inferior portion of L4 has been destroyed by infection. Cultures revealed Staphylococcus aureus.

Diagnostic Evaluation

Imaging Studies

The findings on plain radiographs are characteristic but do not appear for at least 2 to 4 weeks.^{23,28,30,31,56,76} The earliest and most constant radiographic finding, narrowing of the disc space, is present in 74% of patients at presentation.²⁹ Tomograms show abnormalities earlier than plain radiographs (Fig. 86–7) and may show local osteopenia of the endplates at 10 to 14 days, but tomography has largely been supplanted by computed tomography (CT).³¹ Widening of the retropharyngeal space in the cervical spine, enlargement of the paravertebral shadow in the thoracic spine, or changes in the psoas shadow in the lumbar spine may indicate either abscess or granulation tissue surrounding the infection. After 3 to 6 weeks, destructive changes in the body can be noted, usually beginning as a lytic area in the anterior aspect of the body adjacent to the disc and diffusely in the endplate.

FIGURE 86–7 This patient presented with an idiopathic disc space infection at L5-S1 with an associated vertebral osteomyelitis. His main complaint was low back pain. A, This lateral roentgenogram demonstrates marked narrowing of the disc space at L5-S1; however, nothing is seen on this radiograph that would clearly demonstrate this to be a spine infection. B, This lateral tomogram better demonstrates the destruction of the endplates at L5-S1 and the rarefaction of the adjacent bone. The only diagnosis consistent with these findings is a disc space infection with associated vertebral osteomyelitis.

Reactive bone formation and sclerosis are present in 11% of patients on presentation, and most patients will have sclerosis when the disease heals.²⁹ Depending on the virulence of the organism and the response to treatment, progressive bony destruction, collapse, and kyphosis may develop. The radiographic findings generally lag behind the clinical response by 1 to 2 months. With healing, new bone formation and hypertrophic changes at the vertebral margins eventually may produce spontaneous fusion. Fusion occurs in just over 50% of the cases^29,103 but may take up to 5 years.¹⁰⁴ If a solid fusion does not occur, a fibrous ankylosis may be achieved.^24,103

Although the radiographic findings are characteristic, they are not specific and a definite diagnosis is possible only by biopsy.¹⁰³ An unusual radiographic finding that may help with the diagnosis is gas in the disc space; this may represent infection with a gas-forming organism (Fig. 86–8).⁶⁵ However, the most common cause of gas in the disc space in adults is due to degenerative disease.

FIGURE 86–8 This patient presented with a significant paraparesis and associated sepsis. A, This lateral roentgenogram demonstrates marked diminution in the height of the L2 vertebral body. It is surprising that the disc heights at L1-L2 and L2-L3 appear to be relatively normal. B, Tomograms of the lumbar spine reveal gas shadows (arrows) within the disc spaces at L1-L2 and L2-L3. At the time of surgical débridement, Escherichia coli was cultured.

An atypical presentation of vertebral osteomyelitis was reported by McHenry and colleagues.⁸⁴ They described a series of six patients with osteomyelitis in an osteoporotic vertebral compression fracture. The vertebral endplates were intact on the initial plain radiographs.⁸⁴ This presentation occurred in 13% of all hospitalized patients with vertebral osteomyelitis and 2.4% of inpatients with osteoporotic compression fractures at one institution over a 5-year period.¹⁰⁵ Chest radiographs may reveal atelectasis, pleural effusion, and soft tissue masses that may be confused with a tumor.⁸⁷

Radionuclide studies are useful for early detection and localization of infection, before plain films become positive.^{24,26,30,88,97,106–108} Clinical studies have suggested that gallium scans become positive before technetium scans do,¹⁰⁶ and this has been confirmed in experimental studies.¹⁰⁹ Technetium scans show increased uptake diffusely in the region of the infection, whereas gallium scans may show increased uptake in a butterfly area around the infected spine.¹¹⁰ Gallium scanning has been found to have a sensitivity of 89%, a specificity of 85%, and an accuracy of 86% in the diagnosis of disc space infections.¹⁰⁶ In a separate study,¹⁰⁷ technetium scans were found to have a sensitivity of 90%, a specificity of 78%, and an accuracy of 86%. The accuracy of combined technetium and gallium scans was 94%.¹⁰⁷ These two scans combined are currently the authors’ preferred nuclear medicine studies.

In experimental disc space infection, bone scans were positive in 23% at 3 to 5 days, in 29% at 6 to 8 days, and in 71% at 13 to 15 days.¹¹¹ The probability of technetium bone scans becoming abnormal increases with the duration of symptoms, to almost 100%, but false-negative scans have been reported in young children and also in the elderly. This has been postulated to be the result of regional ischemia.⁶⁸

The major mechanism of gallium localization is thought to be neutrophil labeling followed by migration to the inflammatory focus. False-negative gallium scans have been reported in leukopenic patients.¹⁰⁸ Both technetium and gallium scans may be negative with occult infection by low-virulence organisms.⁶⁸ Two cases have been reported in which the technetium scan was negative but the gallium scan was positive, and the authors postulated that this represented pyogenic discitis without vertebral osteomyelitis.¹¹² Technetium scans remain positive for a long time after resolution of the disease, whereas gallium scans become normal during healing and, therefore, may be useful in following the response to treatment.¹¹³

Indium-111-labeled leukocyte imaging has been found to be helpful in the evaluation of sepsis in the appendicular skeleton.¹¹⁴ Unfortunately, it is not sensitive in the spine.^115–117 This may be related to the fact that most cases of vertebral osteomyelitis are chronic by the time the patients are studied, and the inflammatory response may have fewer leukocytes. The overall sensitivity of indium scanning for infections of the spine is 17%, the specificity is 100%, and the accuracy is only 31%.¹¹⁶ A correlation was found between prior antibiotic therapy and false-negative indium scans and photon-deficient indium uptake.¹¹⁶ Photon-deficient lesions may be detected by indium-111-labeled leukocyte imaging in many other conditions including previous surgery, radiation therapy, or metastatic disease.¹¹⁸ Palestro and colleagues¹¹⁹ reported that the specificity was 52% and the sensitivity was 54% when decreased activity was the criteria for osteomyelitis with indium-111 scanning. Single-photon emission computed tomography (SPECT) is a sensitive bone scintigraphic modality for early detection of spondylitis. It is more sensitive than planar scintigraphy and has the advantage of increased contrast resolution and the capability of three-dimensional localization.¹²⁰ Scintigraphy with technetium and gallium are now often performed with SPECT. Love and colleagues¹²¹ compared three-phase bone technetium SPECT, with gallium SPECT, and MRI in 11 patients with spinal infections. Gallium SPECT and MRI were comparable in accuracy and superior to technetium SPECT. Thus gallium SPECT may be useful in patients in whom MRI is contraindicated or in cases where the diagnosis is uncertain. A positive technetium SPECT, in the setting of a negative gallium scan, points toward noninfectious cases of back pain such as degeneration disease or pseudarthrosis.¹²²

CT may show cystic changes in the bone, as well as soft tissue masses, gas in the soft tissues or within the bone and disc, and, later, lytic destruction of the body.^123–125 The prevertebral soft tissue involvement seen on CT usually completely surrounds the spine anteriorly, and the destruction of the vertebra is generally an osteolytic process around the disc space (see Fig. 86–6). This is in contrast to neoplasms, which are characterized by no or only partial paravertebral soft tissue swelling and by changes that may be osteoblastic and more likely to involve the posterior elements than in infection.¹²⁶

CT is valuable in differentiating pyogenic spondylitis from a tuberculous or fungal infection; in the latter, the soft tissue components tend to be more prominent.¹²⁷ The finding of disc hypodensity on CT is relatively specific for infection in the lumbar spine but is less useful in the thoracic and cervical region.¹²⁵ A relatively unique feature of tuberculous infection is vertebral fragmentation and paraspinal calcifications.^128,129 The destruction tends to extend into the pedicle, which is uncommon in pyogenic infections. CT with contrast medium is helpful to delineate the boundary between abscesses and swollen paravertebral muscles.^123–125 CT after intrathecal administration of metrizamide provides exquisite detail for the spinal canal.¹²⁷ CT-guided biopsies of the spine have been shown to be safe and can be done at all levels of the spine (Fig. 86–9).^{123,130–132} Myelography and postmyelography CT are indicated in cases of neurologic deficit and radicular pain to rule out epidural and subdural abscesses. Cerebrospinal fluid (CSF) should also be examined to rule out meningitis.⁸³

FIGURE 86–9 The technique of Craig needle biopsy in the thoracic spine. A, The course of the needle is determined by the measurements obtained on the scout computed tomography (CT) scan. The distance from midline, as well as the angle from the vertical position, can be accurately determined. B, The lateral scout film from the CT scan should be used to determine the exact level to be sampled.

The imaging modality of choice for the evaluation of spine infections is MRI. MRI permits early diagnosis of infection and recognition of paravertebral or intraspinal abscesses without the risk associated with myelography.^133,134 In a prospective study of 37 patients suspected clinically of having vertebral osteomyelitis, MRI was found to be at least as accurate and as sensitive as gallium and bone scanning combined: MRI had a sensitivity of 96%, a specificity of 93%, and an accuracy of 94%.¹⁰⁷ MRI has the advantage of providing more anatomic information than radionuclide studies and is capable of differentiating degenerative and neoplastic disease from vertebral osteomyelitis.¹³⁵ The changes on MRI occur at about the same time as the changes on gallium scans.¹⁰⁷

Disadvantages of MRI are that it is more sensitive to motion degradation, and there are problems with patient positioning and claustrophobia. MRI has a limited field of view, whereas radionuclide scans can image the entire skeleton. MRI may be falsely negative in cases of epidural abscess without involvement of the adjacent bone because the signal intensity of the inflammatory exudate is similar to that of CSF.^107,136

The MRI changes in vertebral osteomyelitis are characteristic (Fig. 86–10). On T1-weighted sequences, there is a confluent decreased signal intensity of the vertebral bodies and adjacent disc, making the margin between the two structures indistinct. On T2-weighted sequences, the signal intensity of the vertebral bodies and the involved disc is higher than normal, and there is generally an absence of the intranuclear cleft normally seen within the adult disc.^107,133 The extent of the infection is best seen, however, using gadolinium contrast enhancement. The disc and the involved portions of the vertebral bodies reveal a marked increased signal intensity that delineates the margins of the infection (see Fig. 86–10C).¹³⁷ The typical T1 changes in the vertebral body and endplates and the T2 changes in the disc space were seen in 95% of the 37 cases of vertebral osteomyelitis described by Dagirmanjian and colleagues.¹³⁸ Only 56% of their cases had typical T2 vertebral body changes. Isointense or decreased signal in the vertebral body on T2-weighted images is consistent with infection if the other typical findings are present. In a more recent study by Ledermann and colleagues,¹³⁹ 46 patients with culture or histologic-positive spinal infections were systematically evaluated with gadolinium-enhanced MR imaging. The most sensitive MRI criteria was the presence of paraspinal or epidural inflammation (97.7% sensitivity), followed by disc enhancement (95.4% sensitivity). Hyperintensity or fluid-equivalent disc signal intensity on T2-weighted MRI was 93.2% sensitive, erosion or destruction of at least one vertebral endplate was 84.1% sensitive, and effacement of the nuclear cleft was 83.3% sensitive. When the infection is confined to a single vertebral body, spread of infection occurs in a subligamentous path.¹⁴⁰ Interestingly, the spread of infection tends to be more commonly in a cephalad direction, affecting the superior disc space more commonly than the inferior disc space. The cause of the signal intensity changes seen in vertebral osteomyelitis is uncertain but is thought to parallel the pathogenesis of the disease. The earliest changes are thought to be related to ischemia and the increased water content of the inflammatory process. As the infection crosses the endplate, a confluent signal intensity occurs on MRI. The normal finding of an intranuclear cleft within adult discs is thought to be related to fibrous tissue within the nucleus pulposus. This cleft is lost at the time of inflammatory involvement of the disc.¹⁰⁷

FIGURE 86–10 Preoperative imaging studies show L3-4 disc height loss and irregular endplate sclerosis on lateral radiographs (A). Contrast-enhanced MRI shows involvement of the L2-3 disc space along with increased signal of the L3 and L4 vertebral bodies (B). Axial images show enhancement of the anterior soft tissues (C, white arrowheads).

In an elegant study comparing MRI findings of pyogenic vertebral osteomyelitis with tuberculous osteomyelitis, Chang and colleagues¹⁴¹ identified five key distinguishing features that help to differentiate between the two disease entities. A retrospective study of 33 patients with confirmed tuberculous spondylitis were compared with 33 randomly selected patients with known pyogenic osteomyelitis. The key distinguishing features were (1) degree of bone destruction; (2) degree of disc preservation; (3) paraspinal abscess appearance; (4) abscess with postcontrast rim enhancement; and (5) postcontrast enhancement pattern of the vertebral body. As expected, the degree of vertebral body and disc destruction were the two most distinguishing differences found. Most patients in the tuberculous (TB) group (82%) had near complete destruction of at least one vertebral body, whereas less than one third (30%) in the pyogenic group had severe vertebral body destruction. Conversely, the disc was preserved in more than one half (57%) of TB group, whereas only 3% of the pyogenic group had a preserved disc space. Thus the credo that TB spondylitis “skips the disc space” is relatively well supported. However, a more accurate distinguishing feature would be better stated that pyogenic vertebral osteomyelitis differs from TB spondylitis by severe disc space destruction with relative preservation of the vertebral body.

Chang and colleagues went to further show that there were marked differences in the imaging pattern of the vertebral body itself.¹⁴¹ In the TB group, the enhancement pattern of the vertebral body was always focal and heterogeneous, with rim-enhancing abscesses. In contrast, the enhancement pattern of the vertebral body in the pyogenic group was nearly always (94%) diffuse and homogeneous. A discreet rim enhancement intraosseous abscess was never observed in the pyogenic group. The paraspinal soft tissue imaging patterns provide further distinguishing features. In the TB group, the paraspinal soft tissues revealed well-defined rim-enhancing lesions. In contrast, the pyogenic infections tended to show more diffuse, ill-defined areas of enhancement.

In a comparison of MRI, bone scans, and plain radiographic evaluations in an animal model of disc space infection, MRI was found to have a sensitivity of 93%, a specificity of 97%, and an accuracy of 95%, corresponding well to results of clinical studies in humans.^107,111 The findings are time related. In one study, scans of rabbits made 3 to 5 days after injection of bacteria all showed a decreased signal from the nucleus pulposus on both T1-weighted and STIR (short T1-inversion recovery) sequences. Scans at 6 to 8 days also showed increased signal from the adjacent endplates on the STIR sequence and blurring of the disc margins on the T1 image. Scans at 13 to 18 days showed more florid endplate changes, and in several scans at 21 days there was increased signal from the vertebral endplates and the disc on STIR sequences.¹¹¹ The MRI findings slowly return to normal after successful treatment of vertebral osteomyelitis.¹⁰⁷ Gallium scans revert to normal much more rapidly and are better indications of appropriate therapy. Post and colleagues¹³⁷ noted that abnormal gadolinium enhancement of the disc, vertebral bodies, and paraspinal soft tissues progressively decreases with successful treatment of the infection. Gillams and colleagues^142,143 described some patients who were improving clinically and had stable or increasing enhancement patterns and concluded that such findings should not be interpreted as treatment failure.

Unfortunately, even MRI may be negative in surgically documented occult infections by low-virulence organisms.⁶⁸ Despite the accuracy of MRI, an absolute diagnosis must be based on bacteriologic or microscopic examination of the tissue.^27,144,145 The only situation in which the diagnosis can be made without a tissue biopsy is when a positive blood culture is obtained from a patient with signs and symptoms of spondylitis. Blood cultures are positive in 24% to 59% of patients with pyogenic spine infections.^22,29 Urine cultures are less reliable because patients with vertebral osteomyelitis may have a coexistent urinary tract infection with a different organism.^22,24

Management

Before the advent of antibiotic therapy, treatment of pyogenic vertebral osteomyelitis involved drainage of abscesses, rest on a frame or plaster bed, and attention to nutrition and general hygiene. The mortality rate with this approach was between 25% and 70%.^27,53 The use of antibiotics has drastically changed the prognosis with this disease, but attention to good general medical care is still a vital part of the treatment. Associated conditions that compromise wound healing or immune response should be managed aggressively. Attention to proper nutrition and the reversal of metabolic deficits and hypoxia are essential. Diabetes and other systemic illnesses should be brought under control.⁹⁰ Any underlying focus of infection in the urinary tract, lungs, skin, or elsewhere must be treated concurrently with the spine infection.¹⁵⁸

The goals of treatment are to establish tissue and bacteriologic diagnoses, prevent or reverse neurologic deficits, relieve pain, establish spinal stability, correct symptomatic spinal deformity, eradicate the infection, and prevent relapses. Biopsy, by either a closed or an open method, is mandatory in any case of spine infection before the institution of antibiotic therapy. The only exceptions to this rule are straightforward cases of pediatric discitis and cases with positive blood cultures in association with strong clinical evidence of spine infection.

Changes in patterns of pathogenic organisms and antimicrobial agents necessitate an accurate bacteriologic diagnosis. If possible, treatment should be withheld until an organism is identified, in case a second biopsy is necessary. However, patients who are systemically toxic should be treated with maximal doses of broad-spectrum antibiotics as soon as the biopsy has been completed. Most patients with vertebral osteomyelitis are not septic and will not be harmed by a delay in treatment for several days. Conversely, if the biopsy is non-diagnostic and antibiotic therapy has been started, a second biopsy may not yield the organism. Patients with clinical evidence of vertebral osteomyelitis but negative cultures from open biopsy should be treated with a full course of broad-spectrum antibiotics. When possible, the choice of antibiotics should be based on the culture and sensitivity test results so that more specific and less toxic agents can be used.

Daly and colleagues^159,160 have demonstrated that antibiotic penetration of osteomyelitic bone parallels serum concentrations for all classes of antibiotics. The penetration of antibiotics into inflammatory exudates and the intervertebral disc is less certain.^161–166 Vancomycin, gentamycin, tobramycin, clindamycin, and teicoplanin all penetrate the nucleus pulposus reasonably well.^161,167 The data regarding cephalosporins are inconclusive, but if penetration does occur, it appears to be at a relatively low level.^162,165,166 The penetration of cephalosporins into inflammatory exudates appears to be inversely proportional to the degree of serum protein binding.¹⁶³ Riley and colleagues¹⁶⁸ have shown that the penetration and distribution of antibiotics into the nucleus pulposus is significantly influenced by the charge of the antibiotic with positively charged molecules penetrating the best.

The route of administration of the antibiotics and the duration of therapy are somewhat empiric because little research has been done to clarify these topics. At present, it is recommended that parenteral antibiotic therapy be used in maximal dosage for 6 weeks and followed with an oral course of antibiotics until resolution of the disease. It may be reasonable to switch from parenteral to oral therapy at 4 weeks.²⁴ Parenteral therapy for less than 4 weeks results in a higher rate of failure.²⁹ Oral ciprofloxacin therapy has been used successfully in the management of patients with chronic osteomyelitis of the tibia or femur.¹⁶⁹ It is possible that ciprofloxacin and other new agents for oral use may supplant parenteral treatment of vertebral osteomyelitis in the future, but general use of these agents should await evidence of their effectiveness.

The erythrocyte sedimentation rate has been found to be a reasonable guide to the response to therapy^{15,23,24,26,29,96,97} and can be expected to decrease to half to two thirds of pretherapy levels by the completion of successful treatment.²⁹ If the sedimentation rate does not decrease with treatment, consideration should be given to a repeat biopsy. CRP is a more useful laboratory test to follow resolution of the infection, as described earlier. However, it is still unclear at what point to discontinue antibiotics on the basis of CRP levels. Further studies are necessary to correlate CRP levels with the duration of antibiotic treatment. Currently, at least 6 weeks of parenteral antibiotics is used empirically. Antibiotic administration must be carefully monitored to avoid toxicity, especially in diabetics and other who might have impaired renal function.⁵⁰

Patients should be immobilized for pain control and prevention of deformity or neurologic deterioration. The length of time a patient should remain at bed rest, the type of orthosis, and the duration of its use all depend on the location of the infection in the spine, the degree of bone destruction and deformity, and the response to treatment. Thoracic and thoracolumbar lesions may require bed rest on a RotoRest or similar device if there is undue pain. Rigid bracing with a thoracolumbosacral orthosis (TLSO) suffices in most cases to allow mobilization of the patient. Thoracic and thoracolumbar lesions are more likely to cause deformity and, if neurologic deficits occur, the prognosis is worse with these lesions than with lumbar spine involvement.^24,90

Cervical and cervicothoracic lesions may be immobilized with a halo device if there is significant instability or deformity. In most cases external bracing is sufficient, and often better tolerated by the patient. Upper thoracic lesions are best immobilized in a TLSO device with a chin piece, and lower thoracic and lumbar lesions should be immobilized in a TLSO device without a chin piece. Frederickson and colleagues²⁴ found that immobilization was most important in those patients with destruction of greater than 50% of a vertebra and recommended immobilization for the first 3 months. In 5 of their 17 cases, significant deformity developed in the first 6 to 8 weeks, all at the thoracolumbar junction or above; those patients with the greatest deformity had 50% or more vertebral body destruction at presentation.¹⁰⁶ Most authors recommend bracing for at least 3 to 4 months. Garcia and Grantham³¹ recommended that the duration of immobilization should be individualized and based on the response to treatment.

Surgical Treatment

Surgery is indicated in the following circumstances: (1) to obtain a bacteriologic diagnosis when closed biopsy is negative or deemed unsafe; (2) when a clinically significant abscess is present (spiking temperatures and septic course); (3) in cases refractory to prolonged nonoperative treatment, where the ESR and/or CRP remain high or pain persists; (4) in cases with spinal cord compression causing a neurologic deficit; and (5) in cases with significant deformity or with significant vertebral body destruction, especially in the cervical spine.^90,170,171 Upper cervical osteomyelitis is rare but generally requires fusion because of the associated instability.⁸¹

In cases of lumbar lesions with root deficits, the final outcome is satisfactory with or without surgical treatment, but patients with spinal cord compression have a better prognosis with surgery.⁹⁰ Surgery should be carried out as soon as possible in these cases, but when doubt exists regarding the chances of a reversible spinal cord lesion, decompression should be carried out because recovery has been noted in patients with paralysis who underwent decompression as late as 5 months after the onset of weakness.⁹⁰

In most cases the spine should be approached anteriorly because this allows direct access to the infected tissues and adequate débridement. Anterior exposure allows stabilization of the spine by bone grafting, which promotes rapid healing without collapse and assists rehabilitation (Fig. 86–11).^90,172–176 Laminectomy without anterior débridement and reconstruction is contraindicated in most cases because it may lead to neurologic deterioration and increased instability.^90,173,177 The situation is similar to that in acute trauma.¹⁷⁸ Laminectomy may be performed in the lumbar spine below the level of the conus, provided there is no psoas abscess or extensive anterior destruction of the bodies that would require débridement.

FIGURE 86–11 T8-9 discitis with osteomyelitis. Magnetic resonance imaging showing enhancement with gadolinium (A) and corresponding T2-weighted image (B) showing bony destruction. Preoperative lateral radiograph (C) shows focal kyphosis, which is treated with anterior miniopen direct lateral thoracotomy with T8 and T9 corpectomies and strut fusion with a titanium expandable cage (D). Posterior stabilization was achieved by percutaneous pedicle screw fixation at the same stage.

Anterior approaches to the spine have been described elsewhere^174,179 and are reviewed in Chapters 17, 18, and 19. For lesions in the thoracic or thoracolumbar spine, the transthoracic approach has the advantage of better exposure, allowing more extensive débridement and better decompression of the cord and more effective bone grafting.^{172,176,180,181} The disadvantage is the potential increased morbidity after a thoracotomy in the presence of a purulent infection. After débridement of the infected focus, anterior strut grafting can be performed during the same procedure. The graft should extend from healthy bone above to healthy bone below.^{172,176,180,181} Autogenous bone grafting after vertebral body resection in the presence of active infection was first reported by Wiltberger in 1952 and has since been demonstrated to be safe and effective regardless of the causative organism.^30,182 Grafting with iliac crest is generally better than grafting with rib.^172,175,183 If a good-quality rib is excised in the process of a transthoracic approach, however, it is often adequate as long as a large segment does not need to be spanned and there is no significant kyphotic deformity.¹⁸³ Revascularization of a cortical graft may not be complete even after 1 year.¹⁸⁴ Vascularized rib grafts have been used with good success for the stabilization of kyphosis.¹⁸⁵ Louw has reported successful fusions in 95% of cases at 6 months and 100% at 1 year when vascularized rib grafts were used for TB kyphosis.¹⁸⁶ Fibular grafts have been shown to be effective for reconstruction of multiple-level anterior decompressions of the cervical spine¹⁸⁷; however, the large amount of cortical bone in fibular grafts makes them less ideal in the presence of infection. In cases with significant kyphotic deformity, anterior reconstruction with autogenous bone grafts after débridement should be carried out as a first stage.^172,176,183 Posterior stabilization and fusion can be performed in a second-stage procedure if necessary (see Fig. 86–11D).^{172,173,183,184,188} Posterior instrumentation has been shown to be safe and effective after anterior débridement and fusion.^22,189 The use of titanium mesh cages may provide better anterior column support because their structural integrity is not affected by degradative enzymes present in an infected environment.¹⁹⁰ The addition of posterior instrumentation provides even better deformity correction and faster rates of fusion.¹⁹⁰ The addition of posterior instrumentation does not appear to increase the risk of infection.¹⁹¹ The anterior and posterior surgeries can be performed on the same day with good results. Safran and colleagues¹⁹² reported on 10 consecutive patients with lumbar osteomyelitis treated with same day anterior decompression and strut fusion with posterior instrumented fusion. All 10 patients achieved solid fusion with eradication of infection. Single-stage anterior and posterior surgery has been shown to be safe and effective using titanium implants. Interestingly, bacteria have a lower propensity to adhere to titanium compared with stainless steel.^{193,194–197} Kuklo and colleagues¹⁹⁸ retrospectively reviewed 21 consecutive patients with pyogenic vertebral osteomyelitis treated with anterior and posterior surgery on a single day with titanium mesh cages. Most patients (16 of 21) had a significant reduction of pain. Radiographically, they averaged 12 degrees of improvement in segmental kyphosis (preoperatively 11.5 degrees to 0.8 degrees postoperatively) with an average of 2.2-mm cage settling (range, 0 to 5 mm) on latest follow-up. There were no instrumentation failures, signs of chronic infection, or rejection, but two patients required a second surgery during the same admission for persistent wound drainage at the posterior wound. Both patients were successfully treated with irrigation and débridement. These findings are supported by previous studies showing the safety and efficacy of single-stage surgical débridement and reconstruction.^192,199,200

In the past, cervical spine vertebral osteomyelitis was managed effectively without bone grafting by drainage, antibiotics, and skull traction for 6 to 12 weeks.³⁷ Prolonged hospitalization can be avoided by débridement, bone grafting, halo immobilization, and outpatient antibiotics. Posterior stabilization performed as a second stage may be reasonable in order to avoid a halo. Today, most cervical spine infections refractory to nonoperative treatment are treated with anterior plate fixation at the time of débridement and strut grafting.²⁰¹

When vertebral osteomyelitis occurs in a patient who has undergone a surgical procedure on the spine or sustained a penetrating trauma of the spine, a fistula should be suspected. Depending on the level of the spine infection, the appropriate imaging study (barium swallow or gastrointestinal series) or endoscopic examination should be ordered to rule out a fistula. If a fistula is identified, it must be repaired along with treatment of the spine infection (Fig. 86–12).

FIGURE 86–12 Miniopen posterior transpedicular corpectomy and reconstruction of L5 vertebral osteomyelitis. A, Preoperative radiographs of a 57-year-old gentleman with a history of multiple previous operations and progressively worsening back pain showing destruction of the L5 vertebral body. White square outlines the expected location of L5. B, Saggital computed tomography images show complete destruction of L5 and partial destruction of L4 and S1. A posterior, miniopen corpectomy was performed through a paramedian approach with insertion of an expandable titanium cage. C, Anteroposterior view of the retractor system used. D, Removal of instrumentation was achieved through separate miniopen approaches using tubular retractors. E and F, Posterior stabilization was achieved with reinsertion of pedicle screws into L2 and L4 with insertion of iliac screws through the miniopen, paramedian exposure.

Costotransversectomy or the slightly more extensive lateral rachiotomy described by Capener is recommended when a spine biopsy or minimal decompression with limited grafting is necessary or when gross purulence is expected.²⁰² This approach is being used more frequently with the advent of improved spinal reconstruction devices such as expandable cages. Lu and colleagues²⁰³ reported on 36 patients with known vertebral osteomyelitis treated with anterior débridement and reconstruction with an expandable titanium cage. In four of those cases, a transpedicular approach was used to perform débridement anteriorly followed by insertion of an expandable cage from the same posterior exposure. All four patients had an excellent clinical result. The transpedicular approach has several advantages. First, the entire surgery can be completed in a single stage. In the treatment of burst fractures, single-stage surgery leads to shortened total operative time and decreased total blood loss.²⁰⁴ Mochida and colleagues²⁰⁵ described the treatment of osteoporotic compression fractures through a transpedicular approach. This strategy is better described in the treatment of metastatic spinal tumors.²⁰⁶ Senel and colleagues²⁰⁷ described good results with transpedicular tumor resection in seven patients with spinal metastases from breast, prostate, and thyroid cancer. Similarly, Bilsky and colleagues²⁰⁸ described 25 patients who underwent posterior-only transpedicular procedures when comorbidities precluded an anterior approach or when the tumor was likely inaccessible entirely from an anterior approach. More recently, this technique has been used by Lee and colleagues²⁰⁹ for the correction of late traumatic thoracic and thoracolumbar kyphotic spinal deformities in 28 patients. In light of the advantages of single-stage surgery, it appears that anterior-only single-stage surgery may be less advantageous. In the study by Lu and colleagues,²⁰³ there was a difference in terms of postoperative pain among various procedures. Only 60% of the patients who underwent an anterior-only approach reported being pain free, as compared with 81% of patients who had anterior-posterior surgery and 100% of the patients who had a transpedicular approach. Furthermore, one of two recurrent infections at the site of previous débridement occurred in the anterior-only patient.²⁰³ Historically, much concern for the fate of the hardware has prompted removal of the retained instrumentation once a fusion is obtained. However, in the authors’ experience, the need for instrumentation removal due to recurrent infection at the original site of infection is uncommon. Routine removal of retained spinal instrumentation placed for vertebral osteomyelitis is not recommended.

Recent advances in minimally invasive spine (MIS) techniques offer alternative methods of surgical treatment. Staatz and colleagues²¹⁰ reported on 21 patients treated with catheters inserted into abscess cavities adjacent to the vertebral body via CT-guidance. Two patients went on to surgery; however, the remainder were successfully treated with catheter drainage and parenteral antibiotics. Percutaneous suction-irrigation systems combined with posterior external fixation have also been shown as effective, minimally invasive treatment.²¹¹ However, the use of external fixators in the spine has not gained wide acceptance. Percutaneous débridement of the infected disc such as via automated percutaneous lumbar discectomy²¹² or endoscopic discectomy^213–215 holds promise as a means of hastening antibiotic treatment when infection is identified before significant bony collapse, abscess formation, and deformity develops. Such techniques would be used when antibiotic treatment alone is likely to be insufficient, but the infection is not severe enough to warrant major spinal surgery. Korovessis and colleagues²¹⁶ showed in a small number of patients that anterior débridement and reconstruction with titanium mesh cages followed by posterior MIS screw fixation led to decreased blood loss and shortened operative time. In a series of 24 consecutive patients, the last 8 cases were treated with posterior fixation and intertransverse fusion using bilateral paramedian intermuscular approaches. Intraoperative blood loss for their initial open posterior surgeries was 540 mL (range, 350 to 750 mL). With the MIS technique, blood loss averaged only 70 mL (range, 50 to 100 mL). This difference was statistically significantly (P < 0.001).

The combined used of expandable titanium cages and a minimally invasive posterior transpedicular approach provides another method of surgical treatment. Kim and colleagues²¹⁷ have described a unilateral paramedian (Wiltse-type) approach to expose the posterior aspect of the involved vertebral body. A subtotal vertebrectomy can then be performed using the transpedicular technique, followed by insertion of an expandable cage that can be placed in a smaller collapsed form and thereafter expanded to the proper size in situ (see Fig. 86–12). Similarly, the use of MIS direct lateral interbody fusion (DLIF/XLIF) techniques shows promise for the treatment of frail patients with vertebral osteomyelitis (Fig. 86–13).

FIGURE 86–13 Miniopen direct lateral lumbar corpectomy and reconstruction with expandable cages. A, A 67-year-old man presented with an infected pacemaker, sepsis, and severe intractable low back pain. A, Gadolinium-enhanced magnetic resonance imaging shows disc space destruction and increased signal intensity at L3 and L4. B, Direct lateral, miniopen, transpsoas exposure for L3 and L4 corpectomies, with insertion of expandable titanium cage filled with BMP-2. C, AP and D, lateral radiographs following posterior percutaneous pedicle screw fixation.

The recent advent and commercialization of bone morphogenetic proteins (BMPs) provides another adjunctive treatment. In both human and animal studies of infected long bone defects, the use of BMP led to improved bone healing in the presence of active infection.^218,219 Several studies in humans shows similar efficacy in the treatment of vertebral osteomyelitis. Garfin and colleagues²²⁰ reported on 14 patients treated by anterior reconstruction using structural allograft or titanium cages filled with BMP-2. Despite the presence of active infection, all 14 patients went on to solid fusion and eradication of infection. In 8 of the 14 cases, treatment was successful even when the anterior and posterior surgeries were performed on the same day. Similar results have been reported by other groups. O’Shaughnessy and colleagues²²¹ reported on the successful treatment of 20 patients with at least 2-year follow-up. Aryan and colleagues²²² showed successful treatment in 15 patients. On the basis of the mechanism of action and histologic studies of BMP in animal models, it is hypothesized that BMP increases vascular ingrowth and recruitment of immunologic cells to the site of infection.²²⁰ BMP has not been proven to be safe or effective in large-scale studies of infection, and its use in this setting would be considered to be a physician-directed (off-label) use by the Food and Drug Administration.

Prognosis

Relapse of infection is uncommon if antibiotics are administered for more than 28 days.^29,90 Nonoperative treatment has a higher failure rate in patients with an impaired immune system.²² The mortality rate is less than 5% to 16% depending on the average age and comorbidities of patients in the series. Death is much more likely in the elderly and in those with an underlying disease.^22,29,31,90 In one series, S. aureus infection was associated with a higher mortality rate than infection with other pathogens.²²

Factors that have been found to predispose a patient to paralysis include increased age, a more cephalic level of infection, and a history of diabetes mellitus or rheumatoid arthritis.⁹⁰ In one series, a neurologic deficit occurred in 45% of the 44 patients who had an impaired immune system, whereas only 19% of the remaining 67 patients developed a deficit.²² Less than 7% to 15% of patients overall have residual neurologic deficits.^22,29 Diabetics are more likely to have permanent neurologic deficits, and patients with thoracic involvement are the least likely to recover.^29,90 Eismont and colleagues⁹⁰ described the results of operation in 14 patients with spinal cord paralysis. Three of the seven patients who underwent a laminectomy deteriorated, and four remained unchanged. In contrast, half of the patients treated by an anterior procedure recovered normal or nearly normal function, and no patient was made worse by the procedure. The patients with root lesions alone had an excellent outcome with or without operation.

In selected patients who require surgical treatment for pyogenic osteomyelitis, the prognosis is very good after the anterior débridement and primary bone grafting in conjunction with a full course of antibiotics. In a series of 21 patients, of whom 6 had neurologic deficits, there were no deaths and no relapses and all of the patients with neurologic deficit recovered. All but one of the patients who underwent fusion had a solid fusion, and one of the two patients who did not have a graft had spontaneous fusion. The mean increase in kyphosis was 3 degrees.¹⁷⁰

Garcia and Grantham³¹ found that spontaneous interbody fusion was the rule and occurred in less than 1 year in most patients and in 2 years in almost all other cases. Some studies have found that the chance of spontaneous fusion in patients treated nonoperatively is 50% or less.^24,29,103 Fortunately, those who do not develop a bony union achieve a fibrous ankylosis, which is generally painless.^{24,31,103,104} Occasionally, a patient complains of persistent back pain from localized degenerative changes at the site of previous infection.^24,31,103

The more cephalad the level of infection, the higher the rate of spontaneous fusion; almost all cases of cervical infection will fuse spontaneously.^15,37 In one series, 6 of 6 cervical lesions went on to solid interbody fusion, compared with 22 of 29 thoracic lesions and 5 of 21 lumbar lesions.¹⁵ One of the patients with cervical infection and one with thoracic involvement had undergone posterior fusion. Fifteen of the patients with thoracic disease underwent costotransversectomy, and five patients with lumbar involvement had anterior débridement without fusion.¹⁵

Although deformities are much less common with pyogenic infection than with TB infection, they still may occur.^24,223 Deformities have been reported to occur in the cervical spine²²³ but are more common in the thoracic and thoracolumbar areas and in those cases with involvement of more than 50% of one or more vertebral bodies.²⁴ Interestingly, IV drug abusers have an excellent prognosis. Ninety-two percent responded to parenteral antibiotic therapy for 4 weeks or more, and relapses responded to a second course. In 67 cases reported in the literature, there were no deaths or permanent neurologic sequelae.³⁸

Overall, the long-term outcome of patients with vertebral osteomyelitis is relatively poor compared with the normal population. O’Daly and colleagues assessed the long-term functional outcome of patients with pyogenic spinal infection using the Oswestry disability index (ODI) and the SF-36 survey to measure health-related quality of life (HRQOL).¹⁰² Twenty-nine patients with a median follow-up of 61 months (range 37 to 104 months) were examined. IV drug use was not reported in the study population. Eight patients (28%) underwent operative treatment and 21 (72%) were managed nonoperatively with antibiotics alone. “Recovery” was classified as survival and disappearance of all signs and symptoms of active infection with no residual disability. “Adverse outcome” was classified as survival and disappearance of all signs and symptoms of infection, but persistence of clinically significant residual disability or pain, or death caused by or associated with persistent infection at any time before follow-up. Nineteen patients (66%) had an “adverse outcome” as defined by this study. As expected, there were marked differences in SF-36 between these patients and the normative population. However, the “recovery” group patients had SF-36 physical function scores and ODI scores that were comparable with the normative values. There was no correlation between SF-36 bodily pain and general health measures and the ODI. Forty-eight percent of patients reported being pain free. Due to the small number of patients, no statistically significant difference was found between patients who underwent surgery compared with patients treated nonoperatively. Delay in diagnosis (>8 weeks) and neurologic deficit at diagnosis were independent risk factors for an “adverse outcome.” Advanced age was a risk factor for acute death, and previous surgery at the site of initial infection was a risk factor for recurrent infection.

Woertgen and colleagues²²⁴ compared the outcome of operative and nonoperative treatment using the 36-item short form health survey (SF-36). The authors retrospectively investigated 62 patients suffering from pyogenic spinal infections: 28 patients (45%) underwent nonoperative treatment and 34 (55%) underwent surgery. As seen in the study by O’Daly and colleagues,^102,224 most patients continued to suffer some sort of pain and various SF-36 measures did not reach normative levels. Despite different indications, the surgically treated patients experienced a slightly better QOL, self-reported satisfaction levels, and better clinical outcomes than patients treated nonoperatively. These results support the current recommendations that surgery should be pursued in those patients with progressive neurologic deficits, in those with obvious spinal instability, and in cases in which medical therapy has failed.

Nonoperative Treatment in the Neurologically Intact Patient

With increased use of MRI and a heightened awareness of this disorder, more patients are diagnosed early in the course of the disease. Recent reports show many patients present with no neurologic deficits. In this subset of patients, nonoperative treatment appears to be efficacious. In a retrospective review of 30 cases, Sorensen showed that all 8 patients without neurologic deficit were successfully treated with antibiotic therapy alone.²⁵⁴ Liem and colleagues²⁶⁸ reported on 21 patients with thoracic epidural abscesses. Three patients had no neurologic deficit. These patients were treated with antibiotics alone with good results. Mampalam and colleagues²⁶⁷ showed good results in six patients without neurologic deficit treated with 4 to 6 weeks of IV antibiotics. The causative organism was identified by blood cultures. All patients became afebrile within 48 hours after initiation of antibiotic therapy. Most patients also noticed a marked diminution in pain. In most series, antibiotic therapy lasted at least 4 weeks and up to 12 weeks.

Recently, Siddiq and colleagues²⁶⁹ compared the outcomes of patients treated with antibiotics alone (25 patients), antibiotics with percutaneous CT-guided drainage (7 patients), or surgery (28 patients). Nearly half of the nonsurgical group had neurologic deficits. Despite this, the overall treatment outcome was comparable with the surgical group. The only predictor of outcome was neurologic abnormality at the time of hospital admission. This is consistent with previous findings where patients with little or no neurologic deficit had good overall results with nonoperative treatment.²⁶⁵ To date, no randomized study directly comparing prophylactic surgery and medical therapy has been performed. However, it is clear that once neurologic deficits appear, surgical decompression and débridement must be timely. When surgery is performed within 24 hours after the onset of neurologic symptoms, overall good results can be obtained in 53% to 80% of cases.^239,268 If surgery is performed after 24 hours, the success rate is 10%.

Thus nonoperative treatment should be pursued with extreme caution. If an epidural abscess is discovered before the onset of neurologic symptoms, the patient should be hospitalized for close clinical follow-up. Identification of the organism is a critical step in the treatment regimen. Often this can be done through blood cultures. If the infection begins in the disc space or vertebral body, a percutaneous biopsy in that area can be performed along with drainage. Once cultures are obtained, IV antibiotics should be initiated promptly and serial physical examination and daily CRP values should be assessed.²⁷⁰ The fever curve and CRP levels should trend downward within 24 to 48 hours. Pain may decrease to some extent. If the baseline leukocyte count was elevated, a downward trend will also be appreciated. In approximately 5 to 10 days, the CRP should be dramatically decreased and is often near normal ranges. Antibiotic therapy should be started immediately on the basis of the Gram stain results and the known bacteriologic basis of the disease. Gram-negative organisms should be suspected if there is a history of a spinal procedure or in IV drug abusers. S. epidermidis should also be considered after spinal procedures.²²⁵ The definitive antibiotic therapy should be based on the culture and sensitivity results. Antibiotics should be given in maximal dosages for at least 2 weeks, and most authors recommend 3 to 4 weeks of parenteral therapy.^225,227 Antibiotics must be administered parenterally for at least 6 to 8 weeks for coexistent vertebral osteomyelitis.^225,227

If the patient remains neurologically intact and afebrile, outpatient treatment can be instituted in the reliable patient. Initially, weekly follow-up examinations and laboratory studies should be performed. Such outpatient therapy is reserved for patients who can reliably return to appointments and can readily respond to changes in their symptoms. In our institution, we typically treat with IV antibiotics for at least 6 weeks. Surgical treatment in this patient population is pursued for the following indications: (1) lack of response to medical treatment, (2) onset of systemic infection (sepsis), and/or (3) development of neurologic signs and symptoms. A lack of response to medical treatment often follows a relatively slow course. There is a lack of decline in the fever curve and CRP levels. Pain may persist or increase. Often this is evident after 5 to 10 days of medical treatment.²⁷⁰ When systemic infection (sepsis) or neurologic deficits emerge, surgical treatment becomes urgent.

Surgical Treatment

It is clear that in a small proportion of patients, a rapid neurologic decline can occur despite the initiation of appropriate antibiotics.²⁶⁵ This can be a devastating event and for this reason, surgical decompression and débridement remain the treatment of choice in nearly all patients. The surgical approach depends on the location of the abscess. Because the abscess is posterior in most cases, laminectomy is generally the treatment of choice.^227,232 The facet joints should be left intact for spinal stability. Intraoperative ultrasonography after laminectomy allows localization of epidural masses and differentiation of them from the adjacent spinal cord.¹³⁴ When the abscess is secondary to vertebral osteomyelitis, it may be necessary to perform both anterior and posterior decompression. Instrumentation and fusion may be necessary in those cases in which spinal stability has been compromised by the decompression. Such extensive reconstruction can be staged at a time subsequent to an initial decompression and débridement in patients who have active comorbidities.

The wound may be closed over drains.^225,227,232 Garrido and Rosenwasser²⁷¹ recommended closure of the wound and continuous suction-irrigation for 5 days after decompressive laminectomy. Baker and colleagues²²⁷ recommended open wound treatment in cases with gross purulence followed by closure of the wound only when granulation tissue is identified. If the wound is left open, delayed closure may be carried out when the leukocyte count, sedimentation rate, and temperature return to normal and the wound shows good granulation tissue.²³² Closure with wound vacuum-assisted closure therapy (V.A.C., Kinetic Concepts Inc.) may be considered, although no series have been reported to our knowledge on the safety or efficacy of the technique.

In children, an extensive laminectomy is undesirable because of the risk of postoperative spinal deformity.^159,249 Hulme and Dott²⁴⁹ suggested two limited procedures for children. They recommended first a laminoplasty type of en bloc removal of the lamina and ligaments with replacement after drainage. Alternatively, they advised exploration of the canal through a small fenestration made by removing ligamentum flavum and portions of adjacent lamina and insertion of thin rubber catheters. They thought that this technique was appropriate when gross purulence was encountered but recommended laminectomy if granulation tissue was found to be compressing the dura.²⁴⁹ Devilers reported on four children successfully managed by a modification of Hulme’s second technique. A single-level laminectomy was performed, catheters were passed cranially and caudally, and the epidural space was irrigated with antibiotic solution. None of the children required reoperation, and no sinus tract developed with this technique.²⁴³

A variation of Hulme’s technique was reported by Cardan and Nanulescu in 1987.²⁷² A -year-old boy with an extensive epidural abscess was treated by epidural lavage using Mancao needles. Three hundred milliliters of isotonic saline was flushed through the epidural space over a 30-minute period while the patient was under general anesthesia. A multiple-hole catheter was then inserted from the sacral hiatus to the midthoracic spine, and a gentamycin isotonic saline solution was administered. The patient improved clinically and, at 18 months postoperatively, was neurologically intact without any sequelae.

A modification of this technique has been employed in adults with good initial outcome. Schultz and colleagues²⁷³ reported on two patients with extensive epidural abscesses. Both patients had abscesses extending from the cervical to the lumbar spine. Rather than performing full-length laminectomies, limited approaches above and below the levels of involvement were used to pass Fogarty catheters through the areas of the abscesses. Once the catheters reached to the opposite opening, the balloon was inflated and carefully pulled back through the canal, effectively “milking” the purulent material out of the canal. Usually, two passes were required. Both patients had resolution of the infection. One patient had near full recovery of motor function, and the other patient had moderate improvement of motor function. This technique is promising as an alternative to complete laminectomies, particularly when there is extensive involvement over many levels or when a minimally invasive approach is warranted due to a fragile medical condition of the patient.

Etiology

Spinal tuberculosis may occur from hematogenous spread from well-established foci outside the spine. The pulmonary and genitourinary systems are the most frequent sources, but spinal tuberculosis may also arise from other skeletal lesions.^76,288 At presentation, the primary focus of infection may be quiescent. Spinal involvement may develop from visceral lesions by direct extension.⁷⁶

Bacteriology

Infection is most commonly caused by Mycobacterium tuberculosis, but any species of Mycobacterium may be responsible.³⁰⁵

Pathogenesis/Pathology

The pathogenesis of the early stages of spinal tuberculosis is similar to that of pyogenic infections of the spine and may result from hematogenous spread or from direct extension of disease.⁷⁶ One study has suggested that the venous or lymphatic routes may be more important than the arterial system for dissemination of this disease. Blacklock was unable to produce spinal disease by injection of mycobacteria into a vertebra or into the left ventricle of experimental animals.³⁰⁶

There are three major types of spinal involvement: paradiscal, central, and anterior.³⁰⁷ In one series of 914 cases, the disease was paradiscal in 33%, central in 11.6%, and anterior in 2.1%; in 52.8%, the disease was too widespread at presentation for identification of the primary focus.²⁹⁰ Atypical forms of spinal tuberculosis include those with neural arch involvement only and rare cases in which granulomas occur in the spinal canal without bony involvement.^290,308,309 A similar classification system along with specific MRI findings have recently been described by Moorthy and Prabhu.³¹⁰ The actual incidence of tuberculosis primarily involving the posterior elements is unknown but is probably between 2% and 10%.^308,309,311 MRI shows homogeneous hyperintense T2-weight signal in the posterior elements and associated paraspinal abscess.³¹⁰

With paradiscal disease, the infection begins in the metaphyseal area and spreads under the anterior longitudinal ligament to involve the adjacent bodies. In contrast to pyogenic infections, the disc is relatively resistant to infection and may be preserved, even with extensive bone loss.⁷⁶ Disc space narrowing has been postulated to occur either as a result of extension of disease or from dehydration of the disc secondary to the altered functional capacities of the endplate. MRI shows low signal on T1-weighted images and high signal on T2-weighted images in the endplate, with disc space narrowing, and large paraspinal and occasional epidural abscesses.³¹⁰

In cases with primarily anterior involvement, the infection spreads beneath the anterior longitudinal ligament and may extend over several segments. The radiographic features include scalloped anterior erosion of several vertebral bodies. This pattern is said to result from aortic pulsations transmitted via a prevertebral abscess beneath the anterior longitudinal ligament.³¹² However, similar changes have been seen in the cervical spine, and another hypothesis is that the scalloping may be due to changes in local vertebral body blood supply.¹⁸⁸ A combination of pressure and ischemia caused by this pus may produce anterior scalloping. MRI reveals subligamentous abscesses, preservation of disc space, and abnormal signal of multiple vertebral bodies.³¹⁰

In cases classified as central involvement, the disease begins within the middle of the vertebral body and remains isolated to one vertebra. These lesions are frequently mistaken for a tumor. They tend to lead to vertebral collapse and therefore are the most likely type to produce significant spinal deformity.³⁰⁷ Such pathologic fractures may mimic the more common osteoporotic compression fracture.³¹³ MRI in central lesions shows signal abnormality of the vertebral body with preservation of the disc space and may also mimic lymphoma or metastases.³¹⁰ The pathologic features of TB spondylitis may be altered by secondary pyogenic infection, which may occur through sinus tracts or after débridement procedures.⁷⁶

The pathologic findings in TB spondylitis differ in several ways from those in pyogenic infections. The disc is relatively resistant to TB infection. The pathologic changes generally take longer to develop and are frequently associated with greater deformity. Large paraspinal abscesses are more common with TB infections.^23,28,76,295

There are numerous mechanisms by which a neurologic deficit may develop in a patient with TB spondylitis. The focus of disease may be within the bone or, occasionally, within the spinal canal without osseous involvement.^{298,308,309,314–317} Seddon recognized that neurologic deficits may occur either acutely or chronically.² He classified acute disease as “paraplegia of active disease” and recognized that this was due to either external pressure or invasion of the dura. Pressure on the spinal cord may arise from an epidural granuloma or abscess, from sequestered bone and disc, or from pathologic subluxation or dislocation of the vertebra. The paraplegia in chronic cases is related to pressure on the cord from epidural granulomas or fibrosis or from a ridge of bone anteriorly caused by a progressive kyphotic deformity. Several other authors have confirmed these patho-genetic mechanisms at operation or postmortem examination.^{10,188,284,317–320}

An epidural granuloma is analogous to a pyogenic epidural abscess. Most frequently, the granuloma arises by spread from the adjacent bone. Because the primary bony lesion is anterior in the majority of cases, spinal cord compression occurs anteriorly. With posterior arch involvement, however, the cord may be compressed from behind.^309,311,321 Although isolated involvement of the neural arch is uncommon, posterior compression from arch involvement occurs in approximately 10% of cases associated with paralysis.¹²

Rarely, an epidural granuloma may occur directly by hematogenous seeding without any bony involvement.* Other lesions that may cause a neurologic deficit without bony involvement are intradural tuberculomas and TB arachnoiditis.^298,314,316 Paraplegia from extraosseous disease occurs in no more than 5% of cases.²⁹⁸

Transdural extension of TB inflammation was first described by Michod in 1871.³¹⁹ Since then, it has been described by other authors.^{188,295,316,317,319} Presumably, transdural extension can occur regardless of whether or not the process originates within the bone. Tuberculosis meningitis is characterized by a granulomatous reaction in the subarachnoid space.³²² Intradural extramedullary mycobacterial disease is the least common presentation of spinal tuberculosis. In 2005 Roca reviewed 22 cases in the literature over the past 25 years. Only 3 (14%) were HIV positive and had CD4 counts of 137 to 228.³²² Roca reported that the majority of patients (82%) with intradural extramedullary tuberculomas required operative intervention. At surgery, pathologic tissue revealed granulomatous reaction secondary to a persistent inflammatory reaction.³²² Although organisms may be absent in the specimen, immunohistochemical staining reveals tuberculosis antigen (Fig. 86–15).

FIGURE 86–15 A, Sagittal T2-weighted magnetic resonance imaging (MRI) scan demonstrating a diffuse posterior mass, displacing the spinal cord anteriorly. B, Axial T2-weighted MRI scan demonstrating a diffuse posterior mass, displacing the spinal cord anteriorly. C, Hematoxylin and eosin stained tissue of the pathologic specimen removed at surgery. This 10× magnification view demonstrates a poorly formed granuloma. D, Antituberculosis immunohistochemical stain at 40× magnification. The immunohistochemical stain is directed against tuberculosis antigen and is brown in the pathologic specimen. This brown staining indicates the presence of tuberculosis antigen.

Clinical Presentation

The clinical presentation of TB spondylitis is variable and depends on many factors. In the classic presentation, the patient complains of spine pain and exhibits manifestations of chronic illness such as weight loss, malaise, and intermittent fever. The physical findings include local tenderness, muscle spasm, and restricted motion. The patient may also have a spinal deformity and neurologic deficit. The duration of symptoms before a definitive diagnosis is made varies from months to years; most cases are diagnosed in less than 2 years.¹⁸⁸ In affluent countries, presentation is generally early, whereas in underdeveloped countries the complications of neglected disease such as paraplegia, kyphosis, and draining sinuses may be the presenting complaints.^295,302,323

The location of the pain corresponds to the site of the disease, which is most frequent in the thoracic region, less common in the lumbar region, and rare in the cervical spine and sacrum.^188,290,293 Patients may present with an abscess in any one of many locations including the groin and buttocks.³⁰⁷ In 10% to 47% of patients, neurologic deficits develop during the course of their disease.^{5,188,286–288,290–295} The incidence of paraplegia is higher with spondylitis in the thoracic and the cervical spine.^290,324

The manifestations of cervical spine involvement vary with the age of the patient. Children younger than age 10 years usually have extensive disease, with large abscesses and a relatively low (17%) incidence of paralysis. In patients older than this, the disease is more localized with less pus, but the incidence of paraplegia is 81%.³²⁴ A distinct syndrome has been reported in heroin addicts with TB spondylitis. All five patients in one series had an acute toxic reaction with fever, back pain, weight loss, night sweats, and rapidly evolving neurologic deficits. All patients had disseminated tuberculosis with involvement of extravertebral sites.³²⁵

Diagnostic Evaluation

The sedimentation rate is generally increased with TB spondylitis, but this is nonspecific. The tuberculin purified protein derivative (PPD) skin test is usually positive and indicates either past or present exposure to Mycobacterium.²⁹⁸ Cultures of early morning urine samples may be helpful in cases of renal involvement, and sputum specimens and gastric washings may be positive with active pulmonary disease. These laboratory findings are helpful in the diagnosis, but an absolute diagnosis can be made only by biopsy of the spine lesion.¹⁷⁶ Aspiration of a subcutaneous abscess on occasion may reveal the organism and obviate the need for spine biopsy.

Isolation of Mycobacterium from clinical specimens takes 6 to 8 weeks, and the sensitivity of culture may be as low as 50%.³²⁶ In the past, the most rapid method of detecting mycobacteria was the staining and smear microscopy of acid-fast bacilli (AFB). However, the AFB smear technique requires 5000 to 10,000 bacilli per milliliter of sputum for detection with only 50% to 80% of specimens testing positive.³²⁷ Polymerase chain reaction (PCR) has been used to rapidly identify the presence of mycobacterium in formaldehyde solution–fixed, paraffin-embedded tissue specimens.³²⁸ Over the past several years, a number of commercially available molecular detection systems have been introduced. All of these systems use detection of mycobacterium DNA or RNA, using the publication of the M. tuberculosis genome.³²⁷ These extremely sensitive detection systems require great care in minimizing contaminants in the sample specimens and thus are relatively expensive. Molecular detection systems are also able to test for genes known to be associated with drug resistance including rifampin, isoniazid, pyrazinamide, ethambutol, and streptomycin. The specificity of molecular detection techniques is approximately 98%, the sensitivity 85%, the positive predictive value 95%, and the negative predictive value 93%.³²⁹

The findings on plain radiographs of the spine will vary depending on the pathologic type and chronicity of the infection. The earliest finding may be bone rarefaction, regardless of type. With peridiscal involvement, disc space narrowing is followed by bone destruction, similar to pyogenic infections. With anterior multilevel spine involvement, the anterior aspect of several adjacent vertebrae may be eroded in a scalloped fashion. Central body involvement resembles a tumor, with central rarefaction and bone destruction followed by collapse. The initial radiographs often show far advanced bony changes, in contrast to pyogenic infections in which radiographs may be normal on first presentation. The central type is more common in the thoracic area, and the peridiscal variant is more common in the lumbar region. The central type causes greater and earlier bone collapse than the peridiscal type.³⁰⁷ Although these radiographic changes are characteristic, a diagnosis based on radiologic changes alone is inadequate in 10% of cases.³³⁰

Chest radiographs are helpful in demonstrating pulmonary involvement and may show a paraspinal abscess. It is not possible to differentiate fibrosis and paravertebral edema from abscess formation on the basis of plain radiographs.¹⁸⁸ Occasionally, lumbar spine radiographs will demonstrate calcification in the psoas muscle in cases with a long-standing abscess.¹⁸⁸ Sclerotic reactive bone formation occurs with healing of TB infection but is seen much later and is less marked than with pyogenic infection.⁸⁶ Heroin addicts with Pott disease may have atypical radiographs. In one study, four of five patients had atypical radiographs including two with an ivory vertebra.³²⁵ Radionuclide scanning with technetium or gallium may help to define the extent of disease.³³¹ Gallium scanning has been recommended for diagnosing extrapulmonary tuberculosis and also to monitor the response to treatment.³³¹ Unfortunately, radionuclide scans are not sensitive for TB infection; technetium bone scans are negative in 35% of cases, and gallium scans are negative in 70%.²⁹⁸ CT is useful to delineate soft tissue changes around the spine and in the canal but is not capable of differentiating an abscess from granulation tissue.

MRI is the imaging modality of choice because it demonstrates both bony and soft tissue involvement. The MRI findings in TB spondylitis may be indistinguishable from pyogenic infections, but there are some differences that are characteristic of tuberculosis and reflect the different pathologic types described earlier.³³² The intervertebral disc may have normal height and a normal signal on MRI, reflecting the resistance of the disc to TB infection (Fig. 86–16). Involvement of the anterior aspect of several contiguous vertebral bodies or involvement of posterior elements suggests a diagnosis of TB spondylitis. Paraspinal masses tend to be longer in TB spondylitis than in pyogenic infections and can be imaged well with plain or gadolinium-enhanced MRIs. Enhanced scans can distinguish abscesses from granulation tissue (Fig. 86–17). A mass with near-total enhancement is generally granulation tissue, whereas a mass with enhancement only at the periphery is generally an abscess.³³³ As the infection resolves, the T1-weighted images of the vertebral body characteristically have progressively greater signal intensity.¹⁰⁵ Even the MRI findings are not completely characteristic, and a biopsy is necessary in all cases. Central body tuberculosis closely resembles a neoplasm^332,334; an epidural TB granuloma without osseous involvement cannot be differentiated from an epidural neoplastic metastatic lesion. The distinction between these conditions can be made only at operation.³⁰⁸

FIGURE 86–16 Tuberculous vertebral osteomyelitis. In contrast to pyogenic infections, the disc tends to be spared relative to the vertebral body. A, Computed tomography scan showing tuberculous infection of the vertebral body and relative preservation of the disc spaces above and below. B, Anterior corpectomy and strut fusion with posterior instrumented fusion.

FIGURE 86–17 Abscess in the left psoas muscle in association with L3 and L4 tuberculous vertebral osteomyelitis. The periphery of the abscess enhances after administration of gadolinium, suggesting that the mass is an abscess rather than granulation tissue. The psoas abscess was found to be a sterile loculation of pus. A, Axial image. B, Coronal image.

The differential diagnosis should include other bacterial and fungal infections, as well as sarcoidosis and neuropathic spine disease. Sarcoidosis rarely involves the spine but may produce paraspinal masses and circumscribed lytic spine lesions with or without a sclerotic rim. Purely sclerotic lesions occur less frequently.⁷⁷ Neuropathic disease of the spine is usually limited to one to three contiguous vertebrae and is characterized by marked reactive sclerosis or destruction. Sclerosis associated with neuropathic disease of the spine parallels the base of the vertebral body and commonly involves the posterior arch. It is associated with paraspinal debris but not masses.⁷⁷

Management

The goals of management are to eradicate the infection and to prevent or treat neurologic deficits and spinal deformity. The modern era in the treatment of spinal tuberculosis began in 1943 with the discovery of streptomycin by Waxmin, and the first major description on the use of streptomycin in TB bone and joint lesions was published by Bosworth and colleagues³³⁵ in 1950. The drug had a tremendous influence on the mortality rate from tuberculosis. Between the 5 years before streptomycin was used and the 5 years after its introduction, the mortality rate at Sea View Hospital in New York decreased by 72.5%.²⁵⁸ Kondo and Yamada³³⁶ reported a decrease in the mortality rate from 42.9% to 9.3% with the addition of streptomycin to the regimen for patients treated nonoperatively. In patients undergoing Albee’s fusion, the mortality rate was 32% without streptomycin and none with streptomycin. In patients undergoing focal débridement, the mortality rate decreased from 71.4% without streptomycin to 2.1% with streptomycin.³³⁶

In 1952 Bosworth and associates published a preliminary report showing encouraging results with the use of isoniazid.³³⁷ These drugs and others eliminated the risk of dissemination of disease and the development of chronic sinuses after surgical débridement and allowed radical procedures to be performed in relative safety.^338,339 Both drugs were found to be effective without surgery when the patients were kept immobilized in the hospital for long periods.³⁴⁰

In Nigeria, a shortage of medical beds and poor medical facilities forced Konstam and Konstam^10,11 to use chemotherapy on an ambulatory basis. Although many patients in their study were lost to follow-up, 96% of those returning were thought to be healed and free of disease. Spinal deformity was found to be a problem with this form of treatment; only 75% developed a bony fusion, 49% had between 0 and 10 degrees of increased kyphosis, and 18% had 30 degrees or more of kyphosis.¹⁰ Other authors found reasonably good results with chemotherapy alone.^9,288,341

Hodgson and Stock^338,342 had excellent results with their procedure of radical débridement and anterior strut graft fusion in association with chemotherapy (the Hong Kong operation). In 1963 the Medical Research Council Committee for Research on Tuberculosis in the Tropics began to investigate these widely divergent forms of treatment. A subcommittee was established that later became known as the Working Party on Tuberculosis of the Spine. This group initiated a number of large-scale controlled prospective trials of treatment methods. The design of each study was based on the available resources in areas where tuberculosis was endemic. The first studies, carried out in Korea and Rhodesia, established that chemotherapy is highly effective in ambulatory patients.^301,323,343 These investigations showed that there was no advantage to an initial period of bed rest in the hospital,³⁰¹ application of a plaster of Paris jacket,³⁴³ or addition of streptomycin to the chemotherapy regimen.^301,323,343 These results were maintained after 5 years³⁴⁴ and 10 years³⁴⁵ of follow-up. Other studies comparing the effectiveness of débridement with that of more radical resection and bone grafting were carried out at three different centers. In Hong Kong, where the radical procedure was popularized, resection and fusion were found to have advantages in terms of less deformity and earlier bony fusion.³⁴⁶ Patients with extensive disease and neurologic deficit were excluded from that study. In two concurrent studies in Africa in which patients with more severe disease were included, there was no significant difference between the two surgical approaches.³⁰² Most of the patients in the three centers were doing well by the 3-year follow-up, and these results were maintained with up to 5 years of follow-up.³⁰³ No changes were found at 10 years in the Hong Kong series.³⁴⁷ The Medical Research Council then set out to determine whether short courses of chemotherapy would be as effective as the standard 18-month regimen (used in all previous studies). In Hong Kong, patients underwent the radical operation and either a 6-month or 9-month chemotherapy regimen of isoniazid and rifampin supplemented with streptomycin for 6 months. The 6-month and 9-month courses were equally effective and at least as successful as the standard 18-month regimen when assessed at 3 years.³⁴⁸ In South India, ambulatory chemotherapy alone with 6- or 9-month regimens was compared with radical surgery plus 6 months of chemotherapy.³⁴⁹ Ninety-seven percent of the patients treated by the 9-month regimen achieved a favorable status at 3 years compared with 93% for the patients in the 6-month ambulatory group. Surprisingly, only 85% of the patients in the surgical series achieved a favorable status. The conclusion of the Research Council was that the treatment of choice for spinal tuberculosis in developing countries is ambulatory chemotherapy with 6- or 9-month regimens of isoniazid and rifampin. Surgery should be considered only for biopsy or the management of myelopathy, abscesses, and sinuses. Even in technically advanced countries they advised against surgery in all cases. When surgery is felt to be necessary, the Hong Kong operation was recommended.^347,348 Although the results of the studies in Hong Kong and Africa on radical débridement and fusion versus débridement alone were at variance, the overall conclusion was that the Hong Kong operation allows anterior bony fusion to occur earlier and in a higher percentage of patients. Kyphotic deformity was less common and not progressive in those patients undergoing the more radical procedure.³⁴⁷ Other independent studies have demonstrated the effectiveness of débridement and fusion and support the recommendation of the Medical Research Council.^{172,176,350–353} The group in Hong Kong has written extensively on this approach and is responsible for its popularity.* Another advantage of anterior decompression and fusion compared with nonoperative treatment that has been demonstrated by a number of authors is the higher recovery rate in patients with neurologic deficit.^{188,292,294,298}

Refinements in antituberculosis chemotherapy have permitted a more selective approach to the surgical management of spinal tuberculosis. Rather than operate in every case, Tuli described a “middle-path” regimen of operating only when medical management failed.^12,285 The first line of treatment was drug therapy; operation was considered for the following: decompression in patients with neurologic deficit who failed to respond to conservative therapy, posterior spinal lesions, failure of response after 3 to 6 months of nonoperative treatment, doubtful diagnosis, instability after healing, or recurrence of disease or of neurologic complications. In cases without neurologic involvement, healing occurred in 94% with antibiotics alone. In 200 cases with neurologic involvement, 38% of the patients recovered with drugs alone; of those patients requiring operation, 69% recovered completely. The overall success rate in patients with neurologic complications treated by this regimen was 78.5%.¹²

The indications for operation outlined by Tuli are similar to our current recommendations, except that patients with a neurologic deficit would be operated on urgently rather than after a delay to see if drug therapy alone would be effective. In general, the indications for operation are the same as with pyogenic infection. Lifeso and colleagues²⁹⁸ think that patients with mild neurologic deficits should not undergo operation because medical therapy alone with close observation is safe. Two of their 23 patients became worse with conservative treatment; both recovered completely after anterior decompression and fusion. They also thought that patients with slight kyphosis could be treated with medical therapy alone because the increase in kyphosis and in the number of affected vertebral bodies reported in children was not found in adults treated medically.²⁹⁸

When an operation is indicated, it is easier to do it early because abscesses tend to dissect along tissue planes. If operation is delayed, fibrosis makes the procedure technically much more difficult. Hodgson and Stock¹⁷⁵ found a direct correlation between the duration of neurologic symptoms before the operation and the time for recovery from paraplegia. Others have confirmed this finding.²⁹² Operation also is advised in late-onset paralysis associated with cord compression by a hard bony ridge in association with kyphosis. Hsu and colleagues³¹⁸ think that, in patients with mild or moderate paraplegia, stabilization alone may be indicated, with decompression reserved for those patients with severe paralysis.

Regardless of whether an operation is performed or not, chemotherapy is an integral part of the management of spinal tuberculosis. The only cases in which chemotherapy is not indicated are those in which late-onset paraplegia from progressive deformity has occurred in a patient with healed inactive disease. Drug therapy is usually started preoperatively but may be started after operation if a biopsy is necessary. The first line of drugs currently in use include isoniazid (INH), rifampin (RMP), pyrazinamide (PZA), streptomycin (STM), and ethambutol (EMB). A number of second-line agents that occasionally are used in special circumstances include ethionamide, cycloserine, kanamycin, capreomycin, prothionamide, and para-aminosalicylic (PAS).³⁵⁵ The choice of agents, dosages, and duration of therapy should be directed by an infectious disease expert.

Multiple drugs are used because of the potential for resistance to a single agent. Selection of rational combinations of drugs is based on the mechanism of action and toxicity of the agents.³⁵⁵ The organisms may be in several different environments and therefore not accessible to all agents. They may reside in the extracellular space, either in the hyperoxic neutral environment of the pulmonary cavity or in the hypoxic acidic environment of caseous material in the spine. They also may exist in the highly suppressive acidic environment inside the activated macrophage. INH and RMP are bactericidal against both intracellular and extracellular organisms.³⁵⁶ RMP may have an advantage against bacilli with low metabolic activity, as are present in caseous material. PZA is bactericidal only in an acidic environment and therefore is effective against intracellular organisms or within caseous lesions. Conversely, STM is active only in the extracellular space and therefore is often used to complement PZA. EMB is bacteriostatic against both intracellular and extracellular organisms and often is used in multiple-drug regimens in place of the once-popular PAS. All the above agents have the potential for significant toxicity. Hepatitis may be caused by both INH and RMP and is four times more common in patients receiving both agents than in those receiving INH alone. INH can also cause dose-dependent peripheral neuritis. The major toxicity of STM is nerve VIII damage; that of EMB is optic neuritis.

Antimicrobial resistance may occur from the multiplication of resistant mutants under the selective pressure of single-drug therapy. Resistance developing during the course of treatment in a patient with an initially drug-sensitive infection is termed “secondary resistance.” “Primary resistance,” defined as infection with drug-resistant organisms in a previously untreated patient, may be transmitted to other patients. The prevalence of primary resistance rose from less than 3% in the United States during the 1970s to approximately 9% by 1986.³⁵⁷ Resistance is much more common in certain urban areas and in patients who are homeless, drug abusers, or infected with HIV. The patterns of drug resistance are variable throughout the world, reemphasizing the need for close follow-up during treatment.^{10,175,298,348} Resistance is generally not a problem with multiple-drug regimens as long as the patient is in compliance.

A 6-month three-drug regimen including INH, RMP, and PZA is used for most cases of drug-sensitive infection in Western nations. Atypical mycobacterial species are often resistant to standard drug regimens.³⁰⁵ Because spinal tuberculosis carries a significant risk, maximal chemotherapy should be used. In a study of lumbar and lumbosacral spine involvement, triple antibiotic therapy with INH, EMB, and RMP yielded excellent results.³⁵⁸ All patients healed the original site of infection with little change in spinal alignment. At 36 months’ follow-up, kyphosis angle improved slightly by 2.2 degrees and the Cobb angle increased slightly by 5.4 degrees.³⁵⁸ Spontaneous bony union occurred in 87.5% of patients. Purtuiset and colleagues³⁵⁹ reported on their experience of 103 cases of spinal TB occurring in a developed country. Most of their patients (74%) were treated with medical therapy alone and the remainder with surgery. Overall, there were two TB-related deaths. Their mean duration of medical treatment was 14 months. These results are similar to those observed in less developed countries such as India.³⁶⁰

Surgical Treatment

An operation may be performed to drain abscesses, to débride sequestered bone and disc, to decompress the spinal cord, or to stabilize the spine for the prevention or correction of deformity. In 1779 Pott described the drainage of a TB abscess: “The remedy for this most dreadful disease consists merely in procuring a large discharge of matter, by suppuration from underneath the membrana adiposa on each side of the curvature, and in maintaining such discharge until the patient shall have perfectly recovered the use of his legs.”¹ His statement was rather optimistic—many patients did not recover neurologic function after this procedure, and many others died of secondary pyogenic infection. In general, abscess drainage is indicated only if the patient is septic from the abscess or has a neurologic deficit from an epidural abscess or when the abscess is extremely extensive. After drainage of an abscess, the tissues may be closed in layers or the wound may be packed open. Paravertebral abscesses in the thoracic spine can be drained effectively by a costotransversectomy.²⁰² Large psoas abscesses may be drained by a retroperitoneal approach.³⁶¹

Simple débridement of the spine without fusion is advocated by some surgeons.^302,336 However, most authors agree with the conclusions of the Medical Research Council that the Hong Kong procedure of anterior radical débridement and strut graft fusion is superior.* Surgery performed when the disease is active is safer, and the response is faster and better than that performed in patients with healed disease.³¹⁸

In the Hong Kong procedure, the spine is approached anteriorly so that the affected area may be dealt with most directly. The sequestered bone and caseous material must be débrided back to bleeding bone above and below and back to the posterior longitudinal ligament. The decompression should go back to the dura in cases of neurologic deficit when spinal cord decompression is necessary.³⁰³ The angular deformity is corrected by insertion of a strut graft. Autogenous bone grafting at the time of the primary débridement is reliable in both adults and children.^† The incidence of fusion with a bone graft is 97% at 10 years, compared with 90% with débridement alone. Medical management with chemotherapy alone may yield a solid fusion in 65% to 79% of cases.^9,10,103

^†References 172, 175, 176, 181, 188, 292, 295, 299, 342, 347, 351, 353, 363–365.

The choice of graft material is based on considerations of graft incorporation and structural support. The grafts used most frequently are iliac crest and ribs. Fibular grafts provide good structural support, but the large amount of cortical bone is undesirable in cases of infection. In addition, long segments of fibula are likely to fracture. In a study of 4-cm-long canine fibular grafts, the grafts were markedly weakened between 6 weeks and 6 months after implantation. The total incorporation may take several years; at 48 weeks, approximately 60% of the necrotic matrix had been remodeled. Despite that, the strength of the graft is nearly normal at 1 year.¹⁸⁴ Bradford and Daher¹⁸⁵ described the use of vascularized rib grafts for stabilization of kyphosis. Incorporation of the grafts occurred between 4 and 16 weeks (mean, 8.5 weeks). They described three patients in whom the graft was placed 4 cm or more anterior to the apical vertebra for mechanical advantage, and none of these grafts fractured.¹⁸⁵ High fusion rates have been reported when vascularized rib grafts are used in the treatment of TB kyphosis.¹⁸⁶

Kemp and colleagues¹⁷² found that rib grafting was inadequate in adults. They reported a 32% incidence of graft fracture and a mean increase in kyphosis of 20 degrees. Partial collapse occurred in some cases because the ribs penetrated the endplate. The overall fusion rate was 62% with rib grafts and 94.5% when autogenous, full-thickness iliac crest grafts were inserted, as long as they crossed the coronal diameter of the vertebra.¹⁷² Iliac crest may be preferable to rib, especially in patients with large defects.^172,175,183

McCuen described the first case of TB spondylitis treated by laminectomy in 1882. In the early part of this century it had become a common procedure for patients with Pott paraplegia. In 1935 Seddon condemned the procedure, claiming that “laminectomy is futile” because it removes the integrity of the posterior arch and may lead to instability and further neurologic damage.¹⁷⁷ The opinion that laminectomy is contraindicated is shared by many authors.^{173,291,292,295,317,339,351,366} Patients actually may improve considerably immediately after laminectomy, but, as Bosworth and colleagues³³⁵ noted, paraplegia inevitably recurs unless fusion is performed both anteriorly and posteriorly. They described 14 patients who had had laminectomies: all died except 4 who had “circumduction” fusions.³³⁵ Currently, the only indication for laminectomy in the treatment of Pott paraplegia is atypical disease involving the neural arch and causing posterior spinal cord compression.^{145,173,177,309,317} It is also reasonable in rare circumstances with posterior epidural tuberculoma without bony involvement.³⁰⁸

Débridement, decompression, and fusion in the thoracic spine may be performed through a transthoracic approach, through a costotransversectomy, or by an extrapleural anterolateral approach. The last has the theoretic benefit of avoiding the TB empyema.³⁵¹ However, no studies have demonstrated any actual advantage of an extrapleural approach over a standard thoracotomy. Kirkaldy-Willis and Thomas¹⁷⁶ demonstrated that the transthoracic approach is more successful than lateral rachiotomy (modified costotransversectomy). The fusion rate was 95% in the former and 78% in the latter; the mortality was 3% and 8%, respectively.¹⁷⁶ They recommended thoracotomy in cases of early tuberculosis, with lateral rachiotomy reserved for late-onset paraplegia associated with a large kyphotic deformity requiring lateral exposure of the dura.¹⁷⁶ Kemp and colleagues¹⁷² support this concept.

With tuberculosis, the periosteum is generally thicker and frequently adherent to the pleura. Therefore it is often necessary to dissect in a subperiosteal plane for exposure. If a lung abscess is found at the time of thoracotomy, the abscess may be débrided by scooping out the necrotic material. Yau and Hodgson³⁶⁷ rarely found an air leak in this situation and had good success by insufflating the cavity with streptomycin and suturing the visceral pleura. Because of the potential for wound dehiscence in these patients, who are frequently immunocompromised and have poor wound-healing potential, the wounds should be closed in layers with interrupted nonabsorbable sutures. In patients with lesions involving more than two vertebral bodies, a period of bed rest followed by external support in a TLSO is recommended until the fusion becomes consolidated if instrumentation is not used.¹⁸³

Posterior fusion alone, without instrumentation, does not control progressive kyphosis,³⁶⁸ but it may be performed in addition to anterior strut grafting for added stability (Fig. 86–18).^183,188 (If a laminectomy is performed for posterior neural compression, a fusion should also be performed if any of the facets are removed.¹⁷³ Progressive kyphosis may occur in the immature spine in spite of a solid anterior fusion. Some authors recommend that a posterior fusion should be performed in addition to an anterior fusion in order to eliminate the risk of increasing deformity.^173,341 Fountain and colleagues³⁶² found that progressive kyphosis developed in only 3 of 31 children with solid anterior fusions. They recommended performing a supplementary posterior fusion only if progressive deformity is noted.

FIGURE 86–18 This patient presented with intermittent fevers and spine deformity. He complained only of relatively minor spine pain. He was neurologically intact. Tuberculosis was suspected and confirmed by culture. A, This lateral roentgenogram shows a 27-degree kyphosis from the inferior portion of T12 to the superior endplate of L5. The intervening vertebrae are grossly destroyed. B, An anteroposterior chest roentgenogram reveals chronic changes in the right lung and an effusion, which are also consistent with tuberculosis. C, This computed tomography (CT) scan of the lumbar spine reveals bilateral psoas abscesses (arrows). There is also a significant paraspinal mass, which is most likely granulation tissue. This was later verified at surgery. D, This postoperative lateral roentgenogram reveals that the kyphosis at the thoracolumbar spine has been reduced to 12 degrees. The intervening neural elements have been decompressed with complete corpectomies from T12 through L4. The patient’s fibula was used for an autogenous bone graft and supplemented with autogenous cancellous iliac bone graft. The patient remained neurologically intact. At the time of surgery, gross purulence was found, which corresponded with the psoas abscesses identified on the CT scan.

Anterior grafts may not provide stable fixation, especially in cases in which the graft spans more than two disc spaces.¹⁸³ To prevent loss of correction, some authors recommend a two-stage procedure with an instrumented posterior fusion followed by anterior débridement and fusion.^333,369,370 Moon and colleagues³⁶⁹ reported on 39 adults undergoing the two-stage procedure in the same operative setting or in a delayed fashion. The infection was cured in all cases, and they achieved excellent deformity correction without a prior anterior release. The loss of correction did not exceed 3 degrees. Similarly good results have been reported by other groups from various countries such as Taiwan, South Africa, India, Kuwait, and Turkey.^371–375

Güven and colleagues³⁷⁶ recommend a single-stage posterior approach without any anterior procedure in cases without paralysis, multisegmental involvement, or large abscesses. They reported on 10 patients who underwent the procedure. All patients had resolution of the infection and the mean loss of correction was only 3.4 degrees. Mehta and Bhojraj³⁷⁷ have proposed a reasonable classification system for surgical treatment of patients with thoracic spine infection. They propose four treatment groups on the basis of the location of the infection. Group A patients, who had paradiscal or central involvement with no deformity, were treated with transthoracic débridement and strut fusion with no further instrumentation. Group B patients, who had paradiscal or central involvement along with deformity, were treated with transthoracic débridement and strut fusion with posterior instrumentation. Group C patients were similar to group A patients but were too ill to tolerate a transthoracic approach. These patients were treated via a posterior transpedicular decompression and posterior instrumentation. Group D patients, who had only posterior element involvement but no deformity were treated with posterior decompression alone with no fusion or instrumentation. With these treatment guidelines, all their patients did well.³⁷⁷

Oga and colleagues³⁷⁸ studied the risk of using spinal instrumentation despite active TB infection. All 11 of their patients had resolution of the infection and none developed a kyphotic deformity after operation. They also evaluated the adherence properties of Mycobacterium tuberculosis and S. epidermidis to stainless steel. The Staphylococcus heavily colonized the rods and was covered with a thick biofilm, whereas only a few biofilm covered colonies of Mycobacterium tuberculosis were seen. These findings have prompted the use of anterior instrumentation at the time of initial anterior débridement. Three recent reports reveal that this single-stage technique is efficacious. Benli and colleagues³⁷⁹ reported on 63 patients from Turkey with involvement of the thoracic and lumbar spines. All patients underwent anterior débridement and decompression with autogenous iliac crest strut grafting. In the same setting, a lateral plate was applied. Kyphosis was corrected by 89% and maintained at an average follow-up of 51 months. Of the patients who had neurologic deficit, 80% had full recovery and 16% with partial recovery. No recurrence of infection was found. Govender reported on 41 patients from South Africa.³⁸⁰ In these patients the anterior strut was fresh frozen allograft. Compared with autogenous rib graft, the fusion rate was slower with allograft. Fusion and remodeling was seen in 33 of 41 patients and partial remodeling with fusion in 8 patients at a mean follow-up of 6.4 years. There were no cases of fracture or late sepsis. Yilmaz and colleagues³⁸¹ reported on 22 patients from Turkey with similar results.

The incidence of cord compression with cervical TB spondylitis is more than 40% overall and much higher in adults³²⁴; therefore an infection in this region requires aggressive treatment. Hsu and Leong³²⁴ reported excellent results from using the Hong Kong procedure via a Southwick-Robinson approach in conjunction with medical management. With C1-C2 involvement, drainage may be performed by the transoral route with or without a supplementary posterior occiput-to-C2 fusion.²⁶¹ Isolated involvement of the arch of the atlas has been treated successfully in one case by chemotherapy, needle aspiration of an abscess, and halo-brace immobilization.³⁸² Lesions at the craniocervical junction are rare, occurring in only 0.3% to 1% of patients with TB spondylitis.³⁸³ Behari and colleagues³⁸³ reported on 25 patients treated variably for craniocervical infection. They classified patients as grade I, defined by neck pain only and no pyramidal signs; grade II, defined by a neurologic status of independent but with minor disability; grade III, defined by partial disability requiring assistance with activities of daily living; and grade IV, defined by severe disability including respiratory compromise. Grade I and II patients were treated with brace immobilization and medical therapy. Grade III and IV patients underwent anterior decompression followed by posterior fusion. Significant improvements in all grades were seen with this strategy.

Lesions between C3 and C7 may be approached through either the anterior triangle¹⁷⁴ or the posterior triangle. The latter may be preferable in some cases because pus often tracks and points in the posterior triangle, making dissection easier.³⁸⁴ When cervical disease is complicated by kyphosis, staged procedures may be necessary. Strut grafting may be performed at the time of débridement if the deformity can be reduced. If the deformity is too great, traction may be necessary before final anterior grafting. Anterior reconstruction should be followed by posterior stabilization and fusion.³⁵⁴ Laminectomies are contraindicated in the cervical spine because subluxation and further neurologic deficits may occur.³²⁴

Complications of surgical treatment are frequent. The operative risk is greatest in elderly patients with extensive disease. In one series, the operative mortality was 2.9% and an additional 1% of the patients died of the disease later.³⁴² Early complications include wound sepsis, pleural effusion, pulmonary embolism, CSF fistula into the pleural cavity, ileus, progressive neurologic deficit, damage to the ureter, loss of graft fixation or graft fracture, atelectasis, pneumonia, air leak, Horner syndrome, and injury to one of the great vessels.¹⁸¹ When streptomycin is placed directly on exposed dura, convulsions may occur.¹⁸¹ Late complications include graft resorption, graft fracture, nonunion, and progressive kyphosis.^172,183,385 Adrenal insufficiency may occur secondary to TB involvement of the adrenal glands. Adrenal suppression should be suspected, especially if calcification is noted on radiographic studies.²⁹²

Prognosis

With TB spondylitis, the prognosis depends on the age and general health of the patient, the severity and duration of the neurologic deficit, and the treatment selected.

Kyphosis

Progressive kyphosis is a significant cosmetic deformity, but more important is the fact that it may cause a neurologic deficit or respiratory and cardiac failure due to restriction of pulmonary function (Fig. 86–19). Rajasekaran and Soundarapandian reported the results of a prospective controlled study performed in collaboration with the Medical Research Council.¹⁸³ The treatment groups included chemotherapy alone for either 6 or 9 months or radical surgery in combination with 6 months of chemotherapy. Ninety patients (98% of the study group) were followed for a minimum of 6 years. Those who underwent nonoperative treatment had a statistically significant higher rate of kyphotic deformity than those treated surgically. There was a direct correlation between the final angle of the deformity and the amount of initial loss of vertebral body. The angle increased severely in 10% of the surgical group and in 32% of the nonsurgical group. Severe deformity in the surgical group was related to graft failure.

FIGURE 86–19 This young adult patient was known to have had tuberculosis of the spine as a child. At this time, she presented with a history of spine pain that was relieved with bed rest and aggravated by increasing activities. A, At the time of first presentation, the patient was seen to have a kyphosis of 110 degrees. It is apparent that she has had extreme shortening of the trunk due to the combination of kyphosis and vertebral body destruction. B, Over a period of 5 years, it can be seen that the patient has had an increase in the kyphosis from 110 degrees to 125 degrees. At this point, she remained neurologically normal. C, This anteroposterior roentgenogram of the thoracic and lumbar spine is consistent with the gross deformity seen on the lateral roentgenograms and obvious on clinical inspection. This is the type of deformity that is best prevented with surgical intervention.

To predict the angle of deformity expected, the researchers devised a formula³⁸⁵; Y = a + bX in which Y is the final angle of the deformity, X is the amount of initial loss of vertebral body, and a and b are constants (5.5 and 30.5, respectively). With their formula, the final angle of the gibbus was predictable, with 90% accuracy in the patients treated nonsurgically.³⁸⁵ If the predicted angle is excessive, early operation should be considered.

Rajasekaran and Soundarapandian¹⁸³ provided additional information on 81 patients treated by the Hong Kong operation and followed for a minimum of 8 years; 19% of these patients had an increase in the gibbous angle of up to 20 degrees, and in 22% it was more than 20 degrees. The major risk factor for increasing deformity was extensive involvement of the vertebral bodies, which resulted in a large defect after débridement and necessitated a graft spanning more than two disc spaces. Patients with lesions of the thoracic vertebrae and those with marked kyphosis preoperatively were also more likely to have progression. These authors concluded that when the length of the graft exceeds two disc spaces, surgical treatment should be augmented by prolonged bed rest, bracing, or posterior arthrodesis. Rib strut grafts were used in many of the patients with progressive deformities, and it was proposed that iliac crest graft may be preferable in patients with large defects.¹⁸³ Iliac crest grafts were used exclusively by Hodgson and Stock¹⁷⁵ and may explain the low incidence of progressive kyphosis in their series. Others also have recommended the use of iliac crest grafts rather than rib struts.¹⁷² In patients with small defects, however, the availability of rib graft and avoidance of additional donor site problems make rib grafts a more attractive alternative.

In addition to graft failure, children are at risk of progressive deformity after anterior débridement and fusion because of persistent growth posteriorly and growth retardation anteriorly. Close follow-up is necessary and a supplementary posterior fusion should be performed if progressive kyphosis occurs.^188,362 A study comparing the radiographs of 117 children operated on for spinal tuberculosis at the age of 2 to 6 years showed that anterior fusion alone leads to greater kyphotic angulation than a posterior fusion, a combined anterior and posterior fusion, or anterior débridement alone.³⁸⁶