EXPERIENCE AT THE MAYO CLINIC

We are currently in the process of analyzing our experience with infected total elbow arthroplasty and the use of DMARDs. The difficulty of our and all such studies is knowing whether medications behave the same in different patients. To what extent is the drugs effect dose dependent, as appears to be the case in some instances? A study from the Mayo Clinic did demonstrate that the dose itself can be a very significant variable that influences the development of an infection with TNF antibody therapy.⁷

AUTHOR’S RECOMMENDATION

Based on our review of the literature and our clinical experience, there is little question in our mind that the anti-TNF agents are associated with increased orthopedic infections. For this reason, we do withhold treatment for at least a month before and a month after our surgical intervention. Although we believe that the increased incidence of sepsis is becoming well documented, what is less well known is whether or not all agents have the same adverse impact and whether withholding these agents is of value. What is the “safe period” both before and after surgery? It is hoped that this issue will be resolved over the next several years, but as mentioned earlier, because of the numerous variables that pertain to the issue, it is likely to be debated for many years to come.

HEMATOGENOUS INFECTION

Hematogenous infection is the most common type of osteomyelitis and has been reported to occur at the elbow in about 4% of such cases.⁷⁷ In the growing child, the end-arterial loop of the metaphyseal bone causes sluggish bone blood flow. The lack of phagocytic activity in these loops allows maturation of a septic thrombus at the arterial site.³⁷ The abscess spreads through the haversian system into the subperiosteal space. If the metaphysis is intra-articular, as at the hip or shoulder, a septic joint will then result,⁷⁵ but this is not the case at the elbow. As at other sites, acute hematogenous osteomyelitis is most common in children younger than 3 and older than 7 years of age. The first group is vulnerable owing to the lack of acquired host immunity; the second age group corresponds to the time of rapid growth.⁵¹ Our recent study reported 85% septic joints in children were of the knee, hip and ankle; only 8% involved the elbow.¹¹

Presentation and Diagnosis

The clinical presentation is typical and includes local pain, warmth, and swelling. The patient may be afebrile but is not necessarily systemically ill. In children, a predisposing, traumatic event is common,^50,83 but identity of a remote focus is less frequent. The elbow is held in flexion and pseudoparalysis, or reflex inhibition may be present. The physical examination includes the following:

1. The specific point of maximal tenderness should be determined by gentle palpation. The focus of the septic process can often be accurately localized in this way, even before radiographic changes are apparent.

2. Gentle passive motion of the joint should be done. With joint infections, all motion is resisted; with metaphyseal osteomyelitis, gentle, supported passive motion is possible.

Except in the very acute stages, an elevated leukocyte count is variably present,^15,53 and the differential count tends to demonstrate a shift to the left in two thirds of the cases. The erythrocyte sedimentation rate has been the most sensitive blood test; it is elevated in the early stages of infection in about 80 percent of persons.^15,52 Therefore, it is very sensitive, but not specific. Interestingly, the rate is statistically higher in joint infections than in bone infections and is a valuable means of following the treatment and resolution of the infection.^15,41,50 Early radiographs are not helpful. After 7 to 14 days, osteoporosis may be present, followed by periosteal elevation or erosions.

The classic appearance of osteomyelitis by bone scan is a well-defined focal area of increased uptake at the site of active infection (Fig. 77-1). The ^99mTc scan may be positive as early as 24 hours after the onset of symptoms in a patient with osteomyelitis.²⁴ The increased activity of equal intensity on both sides of the joint indicates joint disease, arthritis, or synovitis but is not a reliable indicator in the neonate. Nonspecific inflammatory arthritides of rheumatoid arthritis or gout limits the value of the Ga scan.³⁴ False-negative results are also common.⁷² At the present time, we recommend first a ^99mTc scan as a low-cost screening test to provide immediate results and localization. The ¹¹¹In-labeled leukocyte scan may be useful primarily for more acute suppurative infection. More recently, Erdman states that magnetic resonance imaging (MRI) has 100% sensitivity and 0% specificity in a mixed group of acute and chronic osteomyelitis.¹⁷

FIGURE 77-1 Technetium bone scan of a rheumatoid patient (note uptake in the shoulder) with an infected total elbow arthroplasty. Notice the increased uptake on the humeral side of the joint.

With the continuing advances being made with imaging techniques, it is currently believed that the MRI and nuclear medicine are the most sensitive and specific modalities for detection of the septic process. MRI is most helpful to determine the extent of damage, and ultrasound is an effective, noninvasive method to assess soft tissue involvement. Computed tomography (CT) helps document sequestra. The newer positron emission tomography (PET) and single photon emission computed tomography (SPECT) are emerging as useful to evaluate chronic conditions.^59,71 The T1-weighted images of the MRI are also very useful to detect concurrent osteomyelitis in the presence of the septic joint.³⁸ Ongoing efforts to refine short time inversion recovery (STIR) and T1 spin echo (T1 SE) imaging techniques reveal enhanced sensitivity, specifically for osteomyelitis.⁴⁵ Joint aspiration remains the most simple and reliable means of making the diagnosis of elbow joint sepsis, but even this is positive in only about 85% of cases.⁷⁸

DIRECT INOCULATION

Direct inoculation is a relatively common cause of infection of the elbow joint. The thin soft tissue coverage predisposes to compound fractures that may become secondarily infected. Elective nonprosthetic surgery of the elbow region has been associated with an infection rate of about 2% to 4%, significantly greater than the commonly quoted 1% for elective orthopedic procedures.

SPREAD FROM A CONTIGUOUS FOCUS

Infection by spread from a contiguous focus occurs at the elbow from a septic joint or from an infected olecranon bursa. A recent survey of a 10-year experience with septic bursae from Spain documented that three of 69 patients (7.7%) developed osteomyelitis.²¹ These circumstances are most commonly noted in a patient with rheumatoid arthritis, and the management is the same as that for a septic joint. Because a sympathetic sterile effusion may occur with metaphyseal osteomyelitis, even though the metaphysis is extra-articular, the joint should be aspirated to exclude septic arthritis in the presence of an effusion.

MICROORGANISMS

The most common pathogen causing acute hematogenous osteomyelitis is Staphylococcus aureus. Opportunistic organisms are isolated in the debilitated patient, and Pseudomonas aeruginosa is most commonly associated with drug addiction or chronic, draining wounds. Organisms not generally considered pathogenic must be viewed as such when isolated on several occasions, particularly in patients with compromised resistance. In one report, two of the three cases of diphtheroid osteomyelitis involved the elbow, and both patients had altered local immunocompetency.⁵² Serratia infection of open fractures has also been reported in the humerus and forearm in about one third of such cases.⁴⁰ The infected prosthesis is discussed in Chapter 62.

TREATMENT

For the elbow, there are no unique management features of acute hematogenous osteomyelitis, except that prolonged immobilization is to be strictly avoided. In cases that are diagnosed early, antibiotics alone may be adequate.^6,53 Surgery is indicated when there is no response to parenteral antibiotic therapy after 36 to 48 hours. It has been our experience that acute hematogenous osteomyelitis in which symptoms have been present for less than 10 days may be treated with specific intravenous antibiotics for 2 to 3 weeks. If symptoms have been present for more than 10 days, a discrete soft tissue or bone abscess may have developed and must be surgically decompressed. Subperiosteal needle aspiration is sometimes helpful in accurately defining metaphyseal infection. Today we rely on the MRI to assist in the early diagnosis of bone involvement.²⁰

Intravenous antibiotics should be continued for about 3 weeks. Oral agents can be used for an additional 4 weeks, but bactericidal levels should be attained and monitored.⁴³ Infection involving bone may become subacute or chronic, and in this instance, incision and drainage with limited bone débridement and secondary soft tissue healing may be necessary. An extensive débridement of bone severely impairs function because the joint becomes dysfunctionally unstable and is difficult to fuse (Fig. 77-2). Burkhalter and colleagues⁶⁰ have discussed the upper extremity restrictions of function created by elbow fusion and the common complications of failure of union and secondary fracture (see Chapter 70). They recommended a posterior compression plate and pointed out that often the hardware is exposed during the process of healing of the fusion. They also accurately emphasize the limited indications for and the occurrence of forearm motion loss after arthrodesis.⁶⁰ Occasionally, spontaneous arthrodesis occurs after débridement, but extensive removal of bone causes gross instability (Fig. 77-3). If soft tissue coverage is a problem, the flexor carpi ulnaris muscle pedicle flap may be used for coverage of the proximal ulna and elbow. Fourteen centimeters of muscle is available from the pedicle entering 5 cm distal to the elbow joint line. Such a flap brings improved blood supply as well as soft tissue coverage.⁴⁹

FIGURE 77-2 For chronic infection, although both resection (A) and fusion (B) are definitive treatments, both result in a dysfunctional elbow.

(From Morrey, B. F., Fitzgerald, R. H., Kelly, P. J., Dohyns, J. H., and Washington, J. A., III: Diphtheroid osteomyelitis. J. Bone Joint Surg. 59A:527, 1977.)

FIGURE 77-3 Sepsis occurred in fracture dislocation of the elbow leading to spontaneous arthrodesis (A). In some, the débridement and resorptive process causes gross destruction and dysfunctional instability (B).

In the acute phase of treatment, the joint should be splinted, elevated, and put to rest. As the process resolves, gentle active motion is encouraged as soon as possible. Continuous passive motion may prove to be beneficial in some patients to avoid ankylosis or adhesions.⁶⁴

RESULTS

In the preantibiotic area, Wilensky⁸⁰ reported that three of 18 patients developed spontaneous ankylosed elbows owing to immobilization for osteomyelitis of the elbow region. Other long-term residual effects include sinus tract formation, recurrent infection, pathologic fracture, growth disturbances, and development of chronic osteomyelitis. West and associates⁷⁹ observed that chronic osteomyelitis of the humerus appears to have a better prognosis than chronic infection of the tibia or femur. The duration of the septic process is the most important prognostic feature.^53,57 Today, it is anticipated that better function will be realized with better techniques for early detection.