An Approach for Treatment of Complex Adult Spinal Deformity

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Chapter 98 An Approach for Treatment of Complex Adult Spinal Deformity

Complex spinal deformities arise from numerous pathologies. In some cases, they manifest as large-magnitude curves associated with idiopathic scoliosis or kyphosis. Such deformities may be the result of secondary deformity from neuromuscular disease, congenital anomalies, infection, or trauma. The two major groups in terms of volume are decompensated deformities that are due to degenerative change in the preexisting curve and iatrogenic deformities.

The range of normal for cervical lordosis, thoracic kyphosis, and lumbar lordosis is quite variable.¹^–³ Varying degrees of scoliosis can be tolerated depending on many other factors. As a result, spinal balance apparently is more important in terms of symptoms and progression than the magnitude of scoliosis or kyphosis. A review by Kuntz et al.¹ showed that there is only a narrow range of spinal balance and that this is highly conserved.

Clinically, spinal balance can be assessed by examining the head position of a standing patient in relation to the pelvis. In the lateral view, a plumb line from the ear canal should pass through or behind the greater trochanter. In the anteroposterior view, a plumb line from the inion should pass between the posterior superior iliac spines. Radiographically on a long cassette film, one can use either the C7 vertebral body or the odontoid as the starting point for a plumb line. Use of the odontoid as a marker allows assessment of cervical deformity in overall spinal balance. A plumb line from the odontoid should pass dorsal to the center of rotation of the hip in the lateral plane and should fall between the medial borders of the S1 pedicle in the anteroposterior plane. A plumb line from the C7 vertebral body should pass through the L5-S1 disc space. Figure 98-1 shows preoperative anteroposterior (see Fig. 98-1A) and lateral (see Fig. 98-1B) views of a patient with decompensated kyphoscoliosis with loss of both sagittal and coronal balance. Postoperative views of the same patient show restoration of balance (see Figs. 98-1C and D).

FIGURE 98-1 A, Preoperative anteroposterior view of a 58-year-old woman with decompensated kyphoscoliosis. There is a lateral trunk shift. B, Preoperative lateral view. The C7 vertebra is significantly in front of the L5-S1 disc space. C and D, Postoperative anteroposterior (C) and lateral (D) films. A plumb line from C7 would not pass through the L5-S1 disc space in both planes.

In many patients with spinal deformity, in particular, in adults, the clinical picture can be complex, and the decision-making process can seem daunting. When a patient with a complex deformity presents for evaluation, it is often difficult to know where to start. Having a systematic approach to assessment and planning of treatment makes treatment easier. A complex problem can be made easier to understand if it is broken down into its component parts. The author uses a four-part process to do this, and this chapter uses this framework to discuss the treatment of complex spinal deformity. The four components are problems, goals, options, and plans.

Define the Problem

Although it may seem simplistic, it is important to begin the process by defining the problem. In contrast to idiopathic adolescent scoliosis, in which the predominant focus is on the magnitude and progression of the deformity, there are more factors to consider in adult deformity. One key clinical difference in adult deformity is that adults generally seek treatment for the symptoms of the deformity rather than the deformity itself.⁴ As a result, the deformity is viewed within the context of the symptoms it produces. In addition, comorbidities need to be considered. In many cases, the patient will already have had other spine procedures.

The first step is a detailed history. What is the main presenting problem? How does it affect the quality of life? How has it changed over time? If the effect on quality of life is relatively minimal, what is the likelihood of the problem progressing? In many patients, nonoperative treatment may be a viable option even in the presence of significant deformities. It is also important to understand the patient’s perception of the problem. In the author’s experience, some patients present with few symptoms but desire aggressive treatment because of fear that progression of the problem will lead to paralysis or death. Other patients present seeking information or to establish a relationship with a practitioner in case symptoms worsen.

Comorbidities are an important part of the history if one is considering surgery. In addition to cardiovascular and pulmonary conditions, nutritional status and risk factors for osteoporosis should be considered. If the patient has had prior surgery, it is important to know what was done. It is also important to know why the surgery was performed and what the short-term and longer-term outcome of the surgery was. Prior investigations and operative reports are very valuable in the assessment if they can be obtained. In some cases, the deformity may be iatrogenic.

The physical examination should include a detailed neurologic examination. Examination of spinal alignment and balance is important. Loss of sagittal and coronal balance is associated with increased symptoms and seems to have a higher risk of progression.⁵^–⁷

Imaging studies are an integral part of defining the problem. Conventional radiographs in the standing position including the entire spine and pelvis are the standard method of assessing deformity. Lateral bending films can assess the flexibility of the coronal deformity. Supine films (often done with a bolster under the apex of the deformity) can help assess the flexibility of sagittal plane deformities. MRI is the investigation of choice for assessing the status of the discs and the neural axis. CT provides excellent assessment of the bony anatomy, and the use of sagittal and coronal reformatting allows a more detailed assessment of the bony architecture. If a patient has had prior surgeries, CT is a sensitive and specific method of assessing fusion status. Myelography with or without CT may make assessment of the neural axis easier in large deformities. Bone scan has historically been used for assessment of pseudarthrosis but has been largely supplanted by CT in the author’s practice.

In patients in whom surgery is being considered and comorbidities are present, general and specialty medical consultation for preoperative optimization should be used.⁸ Nutritional and bone health status are often overlooked in the workup and can have significant effects on outcome.⁹^–¹² Bone mineral density testing can help to assess bone health, although the presence of degenerative changes in the spine may artificially increase bone mineral density of the spine.^13,¹⁴ Vitamin D testing and supplementation in the preoperative period should be considered, especially in regions or cultures where there is little direct sun exposure.^15,¹⁶ In large-magnitude thoracic deformities, pulmonary function testing should be done for risk assessment.¹⁷

Goals

After the problem has been defined, the next step is to decide on the goals of treatment. It is important to assess the patient’s goals for treatment as well as the practitioner’s goals. Are these goals achievable and at what risk? Patients with minimal symptoms in daily life who have limits with high-level activities may desire a level of function that is not achievable. Alternatively, for a patient with low demands and expectations, simpler nonoperative treatments may provide an appropriate quality of life without the risks associated with addressing the deformity.

Prevention of progression is a common goal in treatment of deformity. In adult deformity, progression is unpredictable for many conditions, and progression of symptoms may or may not correlate with progression of deformity.¹⁸^–²⁰ As a result, prevention of progression is an uncommon indication for treatment after skeletal maturity.²¹^–²³

Generally, the goals of surgical treatment are to relieve compression of neural elements, stabilize instabilities, and correct and maintain the correction of the deformity. These goals need to be accomplished while minimizing risk in the short term and the long term. A primary end result of deformity treatment should be the restoration of sagittal and coronal balance. Outcome studies have shown weak, if any, correlation between correction of the Cobb angle and outcome but have shown clear correlation with spinal balance and outcome.^6,^7,²⁴^–²⁷

Osteoporosis

Osteoporosis is common in patients with spinal deformity. It may be associated with vertebral fractures leading to increased deformity.^21,²⁸ It also may have an effect on outcome of surgery.^11,²⁹ Although osteoporosis does not affect bone healing, it does affect the holding power of spine instrumentation.³⁰^–³² For this reason, assessment of osteoporosis is an important step when considering surgery. Although there is no quoted level of bone density beyond which surgery is not an option, the risks of failure increase with higher degrees of bone loss. Preoperative optimization of bone health with vitamin D testing and supplementation as required and pretreatment with teriparatide have been advocated,¹⁶ but no studies have looked at outcomes of these interventions. Animal studies have suggested that teriparatide may improve healing of fusions.^33,³⁴

Options

Decompression Alone

In patients with a stable balanced spine with isolated radiculopathy, one option may be to consider an isolated decompression. Generally, compressive pathology occurs on the concavity of the deformity.³⁵ If a single level can be identified either on the basis of clinical symptoms or with nerve root blocks, an isolated decompression may be a reasonable option. There is a risk that decompression may exacerbate deformity in these patients. Previous studies showed that the results of decompression alone in the presence of scoliosis may not be as good as decompression in a normally aligned spine.³⁶^–³⁸ Many of these studies were done with more extensive decompression than would be done at the present time. Decompression alone is not an option in the presence of a rotatory subluxation or spondylolisthesis at the apex of the deformity. Anecdotally, decompressions of a keyhole or laminotomy type are associated with a lower risk of progression of deformity.^39,⁴⁰ This option may be particularly good in elderly patients with an isolated radiculopathy and relatively minimal axial back pain.

Fusion without Instrumentation

In patients with severe osteoporosis, use of pedicle screw instrumentation may be contraindicated. In these patients, an option may be fusion without instrumentation. This procedure is reserved for patients with stable balanced deformities. Generally, fusion without instrumentation is used in patients who are much older, more frail, and less able to tolerate extensive procedures. There is little or no literature on this procedure, and consequently it is difficult to compare it with other techniques.

Limited Fusion

In many patients, symptoms can be isolated to a single level of pathology. An example would be a degenerative spondylolisthesis and a degenerative scoliosis. In these patients, it may be reasonable to treat only the symptomatic level. This is a controversial treatment. In a more recent study, reasonably good results were obtained with single-level fusion for degenerative spondylolisthesis in degenerative scoliosis. A few patients needed further surgery, and few if any had progression of deformity.⁴¹ Some authors have criticized this technique as having an unacceptably high rate of failure.⁴² However, there are no controlled trials comparing it with more extensive fusion; the literature contains few articles.^43,⁴⁴

One more recent trial ⁴⁵ looked at surgeons whose practice contained more than 50% deformity cases and showed that these surgeons were more likely to perform fusion of more levels than surgeons whose practice contained less than 50% deformity cases. The authors implied that the surgeons with more deformity cases were more likely to select a correct course; however, there was no clinical correlation in this study. It is perhaps equally valid to suggest that the surgeons with more deformity cases were more likely to perform fusion of excess levels.

Instrumented Correction and Fusion

In most patients with complex deformity, some form of instrumented correction and fusion is performed. Multiple options are available, and each option has advantages and disadvantages. The end result should be a stable balanced spine with a solid biologic fusion. Any technique that achieves this goal is a reasonable option.

In most cases, pedicle screw instrumentation is the mainstay of instrumented fusion. Pedicle screws allow better correction of most deformities.⁴⁶^–⁵⁰ Pedicle screws are extremely versatile and have excellent holding power. They can exert or resist forces in multiple planes. Pedicle screws tend to be weakest in pull-out.⁵¹ As a result of their versatility, pedicle screws have become the main type of instrumentation used. Hooks and wires are less commonly used because they are more technically demanding and less versatile. Hooks and wires are relatively strong in pull-out but need intact posterior elements.

Obtaining solid biologic fusion is of utmost importance in the long-term. Fusion can be achieved through interbody, dorsal, or dorsolateral fusion. Interbody techniques generally have a higher fusion rate.⁵²^–⁵⁴ In the lumbar spine, dorsolateral fusion is biomechanically superior and more effective than laminar onlay fusion.⁵⁵ In the thoracic spine, dorsal fusion is more typically performed. The biology of fusion, choice of bone graft or bone graft substitute, and use of extenders are discussed elsewhere. In complex surgery with the high risk of fusion failure, the choice of bone graft and bone graft substitutes is of great importance. The use of bone morphogenetic protein in deformity seems to lead to significantly higher fusion rates. Limited evidence suggests that it is cost-effective in this indication.⁵⁶^–⁵⁸

Selection of rostral and caudal levels is the first step in determining an operative plan. Generally, the construct should begin and end at a neutral vertebra in both the sagittal and the coronal planes. In complex or degenerative deformities, it is often more difficult to determine these levels than in an idiopathic scoliosis. The presence significant disc degeneration or instability below a neutral vertebra would generally necessitate extension of the fusion beyond this.^59,⁶⁰ Perhaps the most controversial question is whether or not to end a fusion at the L5 vertebra. Numerous studies have been performed and reached conflicting results.⁶¹^–⁶⁵

A series of studies by Lenke et al.^61,⁶² looked at this question and concluded that if the L5-S1 disc is relatively normal on MRI and the L5 vertebral body does not have an oblique takeoff, preserving the L5-S1 motion segment is a reasonable option. In these patients, the incidence of repeat surgery to fuse the 5/1 level was lower than the incidence of repeat surgery for pseudarthrosis. In the presence of significant L5-S1 disc degeneration or oblique takeoff or instability at L5-S1, the incidence of repeat surgery to fuse the 5/1 level was higher than the incidence of surgery for pseudarthrosis.

Numerous factors must be looked at in considering the upper stop point of the construct. The thoracolumbar junction represents a transition from the mobile lumbar spine to the stiffer thoracic spine. Constructs extending up from the sacrum to the lumbosacral junction can create a stress riser if stopped at the junction. Typically, it has been considered acceptable to stop such a construct at L2, but constructs longer than this should extend to T10 ^59,^60,^66,⁶⁷; however, a more recent study has called this into question. In this study, there seemed to be no clearly defined level at which the risk of subsequent surgery was lessened.⁶⁶ In deciding to stop in the lower thoracic spine, one must also consider whether this stop point is at the apex of the thoracic kyphosis. In patients in whom a fusion stops at the apex of the thoracic kyphosis, there is significant risk of proximal junctional kyphosis. It may be preferable in these patients to extend the construct up into the upper thoracic spine, typically T4 or T5.^59,⁶⁰

Long fusion constructs to the sacrum have a high incidence of failure because of pseudarthrosis at L5-S1. This pseudarthrosis is due to numerous biomechanical and anatomic factors. The S1 pedicle is more cancellous and has a short anteroposterior diameter, and the holding power of S1 pedicle screws is less than at other levels. In addition, forces at this level are magnified because of the relatively large lever arm exerted by the pelvis.^65,⁶⁹ Many strategies have been suggested to increase the fusion right at L5-S1. Primary among these strategies is the use of interbody fusion through either a ventral or a dorsal approach.⁶⁵ This strategy has been shown to decrease pseudarthrosis.

More recent studies have assessed anterior lumbar interbody fusion and compared it with posterior lumbar interbody fusion or transforaminal lumbar interbody fusion. None of these techniques showed clear superiority in these studies.⁶⁸^–⁷¹ McCord et al.⁷² analyzed alternative fixation techniques at the lumbosacral junction; this study led to the concept of the pivot point, which is the region of the dorsal aspect of the anulus fibrosus at L5-S1. Fixation at the lumbosacral junction should extend ventral to this pivot point to provide increased stability. Sacral alar screws, S2 screws, iliac bars and screws, and iliosacral screws have been suggested for this procedure. Biomechanical studies showed increased rigidity with the use of iliac or sacroiliac screws, and clinical studies suggested that these two fixation types are superior to sacral alar or S2 screws.⁷⁰^–⁷⁷ In a longitudinal series by Kostuik and Musha,⁶⁵ pseudarthrosis rates were decreased from 83% to 3% by the use of interbody fusion and iliac fixation.

Many authors have advocated increasing deformity correction through the use of anterior releases and fusions.^78,⁷⁹ It is believed that this approach increases correction and increases the fusion rate. However, more recent studies have called this into question.⁸⁰^–⁸² With the use of segmental pedicle screw fixation and alternative release techniques, equivalent deformity correction can be obtained through purely dorsal procedures without the morbidity⁸³ of an anterior release. These studies compared more traditional open anterior release techniques. With the advent of new or less invasive procedures and the use of interbody fusions through a direct lateral approach, the morbidity of anterior releases may be significantly less. Such minimal access lateral approaches and fusion techniques have been shown to give good correction, high fusion rates, and reasonably good clinical results.⁸⁴^–⁸⁶ In the author’s practice, these techniques have replaced traditional open releases and fusions. The use of these techniques at the L4-5 level should be considered cautiously. The anatomic corridor is small,^87,⁸⁸ and there is a relatively high rate of L3 neurapraxia.⁸⁶ The author no longer uses minimal access lateral techniques for the L4-5 level.

Instrumentation in Osteoporosis

The presence of osteoporosis increases the failure rate of instrumented constructs in deformity surgery. Osteoporosis compromises the holding power of the implants leading to this increased failure rate. Numerous strategies have been mediated to lessen this failure risk, and Hu ²⁹ summarized them well in a review article. Essentially, these strategies all are methods of dispersing or decreasing forces across the construct. Increasing the number of fixation points decreases the stress on each element of the construct. Cement augmentation of pedicle screws has been shown to increase their pull-out resistance. Generally, it is unnecessary to perform cement augmentation of all fixation points; only the points at the ends of the construct need to be reinforced with cement. There is relatively more loss of cancellous than cortical bone in osteoporosis, and fixation that uses cortical bone is relatively stronger. As a result, laminar hooks may be a good option in a kyphosis construct, which is likely to fail in pull-out. If correction can be obtained through osteotomies or releases, loads on the hardware are more likely to be neutral, and the construct is less susceptible to hardware failure.^12,^29,^89,⁹⁰

Osteoporosis has been considered a relative contraindication to the use of interbody fusions. Biomechanical studies by Cunningham and Polly ⁹¹ showed that use of interbody fusion increases the strength and rigidity of constructs. Interbody grafts or cages placed asymmetrically can be used to obtain correction, allowing the hardware to be in neutral and decreasing the risk of hardware failure.⁹²

Interspinous Spacers

Interspinous spacers such as the X-Stop (Medtronic, Memphis, TN) are indicated for treatment of spinal stenosis in the absence of deformity. In the U.S. Food and Drug Administration (FDA) studies, scoliosis was an exclusion criterion. It has been suggested that these spacers may be used in an off-label manner for the treatment of stenotic symptoms in the presence of deformity.⁹³ The author has used interspinous spacers in rare cases of patients with severe medical comorbidities and significant deformity who would not tolerate traditional surgery. The results have been mixed, but there have been few complications. Further studies are warranted.

Osteotomies

Osteotomies are powerful tools in the treatment of complex deformity. Many of these deformities are very rigid, and in patients who have undergone previous surgery, the deformity may be fixed owing to fusions. Osteotomies are generally used to correct sagittal plane deformities but may also be used to correct coronal and biplanar deformities. They can be very technically demanding but can give excellent clinical results.

The simplest osteotomies to perform are facet resection osteotomies as described by Ponte or Smith-Petersen. There is confusion as to nomenclature of these osteotomies. Smith-Petersen et al.⁹⁴ described a procedure where the facet was resected and the disc released leading to a pivot at the dorsal corner of the vertebral body, causing closure of the osteotomy dorsally and extension through the disc space ventrally. This procedure was originally described in ankylosing spondylitis. The more common facet resection and closure through a mobile disc was first described by Wilson and Turkell⁹⁵ but has been widely attributed to Ponte.⁹⁶ For clarity, the author uses facet resection osteotomy.

These osteotomies can be used anywhere there is a mobile disc. Correction of 5 to 10 degrees of kyphosis can readily be obtained, and multiple levels can be used.^97,⁹⁸ Some coronal correction can be obtained as well. Facet resections can also be used to increase the correction of the coronal deformity. A facet resection osteotomy augmented by an interbody fusion can increase the amount of correction obtained through this technique. An example is shown in Figure 98-2.

FIGURE 98-2 A, Preoperative lateral view of focal kyphosis above a previous fusion. B, Postoperative lateral view shows approximately 20 degrees of correction with facet resection osteotomy and interbody implant.

If larger degrees of correction are required, a pedicle subtraction osteotomy can be considered. This is a closing wedge osteotomy performed by removing the posterior elements of the pedicle and a portion of the vertebral body. First described by Scudese and Colabro,⁹⁹ this is a very powerful technique that allows routine correction of 30 degrees or more.^97,⁹⁸ It has typically been performed at lumbar levels¹⁰⁰^–¹⁰² but can be performed safely in the thoracic spine as well.^103,¹⁰⁴ These procedures are technically demanding and associated with significant complications.¹⁰⁵^–¹⁰⁷ Clinical results are very good. Biplanar correction can also be achieved allowing correction of deformity in more than one plane.¹⁰⁰^–¹⁰²

Two basic types of pedicle subtraction osteotomy have been described. In the first type, osteotomes are used to create a wedge, which is then removed. The alternative procedure is a decancellation osteotomy. In this procedure, the vertebra is decancellized, the dorsal wall is reduced into the cavity, the lateral wall is osteotomized, and the osteotomy is closed.¹⁰⁸ No comparison studies of these two techniques exist. Figure 98-3 shows the preoperative and postoperative radiographs of a patient with a posttraumatic kyphosis treated with a pedicle subtraction osteotomy to restore lumbar lordosis.

FIGURE 98-3 A, Preoperative lateral view of a 38-year-old woman 20 years after operative treatment of L5 burst fracture shows significant lumbar kyphosis in a fused spine. B, Postoperative film shows correction through L3 pedicle subtraction osteotomy.

Vertebral Column Resection

In some very complex high-magnitude deformities, complete resection of one or more vertebral segments may be required to correct deformity. This procedure is called a vertebal column resection. It can be done through a combined anteroposterior or a dorsal-only approach.^97,^102,^109,¹¹⁰ This technique may be used in an apical kyphectomy for spina bifida.¹¹¹ This procedure can be used for both kyphosis and scoliosis and may be used to obtain biplanar correction. In some cases, the anterior column is reconstructed with a graft or cage implant; in other cases, the spinal column is shortened. These procedures are also associated with significant risks. Reasonably good clinical results have been reported.^97,^101,^109,¹¹²^–¹¹⁵

Plans

After the specific problem has been defined and the goals of surgery established, the operation should be planned. Careful preoperative planning and communication of the plan to the operative team make the procedure more efficient and safer.

In the preoperative period, steps should be taken to ensure the patient is optimally prepared for surgery. The author considers smoking cessation to be mandatory for all such procedures. Preoperative consultation with a hematologist for blood management may help optimize hemoglobin before surgery.¹¹⁶ Studies have suggested an increased risk of thrombotic complications with the use of erythropoietin analogues, so the risks and benefits must be balanced.^117,¹¹⁸ Preoperative medical cardiology and pulmonology consultations should be obtained as indicated.^8,¹⁷

If a combined anteroposterior approach is being considered, one must decide whether to use a single-day or staged multiday approach. Single-day procedures have the advantage of only a single anesthetic and recovery period but can result in very long procedures with excessive blood loss. Single-day procedures may also be more demanding on the surgeon. Staged procedures may be less physically demanding for the patient and the surgeon. Studies that have compared single-day and multiday approaches showed no clear benefit of one over the other.¹¹⁹^–¹²⁴ It is the author’s practice to do most of these procedures as a single-day surgery but to stage them if the procedure is particularly complex or complications arise.

Complex surgeries often require large inventories of implants. It is important to coordinate with equipment suppliers to ensure an adequate supply of appropriate implants is available. The plan should include determining whether any special implants or instruments are required for the procedure. These sets should be present before beginning the procedure. If an access surgeon is being used for the approach, the appropriate sets for this surgeon should be obtained as well.

Neurologic monitoring should be considered for all of these procedures. At the author’s institution, somatosensory-evoked and motor-evoked potentials are used for all spinal deformity cases. Stimulated electromyographic monitoring is used for minimal access lateral lumbar approaches. Neurologic monitoring has been shown to decrease the risk of neurologic injury.^125,¹²⁶ If motor-evoked potentials are to be used, this should be communicated to the anesthesiologist to ensure that neuromuscular blockade is not used during the procedure.

Intraoperative red blood cell salvage is routinely used in complex surgery to reduce the use of autologous blood donation.¹²⁷^–¹²⁹

Intraoperative imaging is facilitated by the use of a radiolucent table. Radiographs obtained intraoperatively in both sagittal and coronal planes allow an estimate of correction obtained and implant placement. Intraoperative fluoroscopy may be used to guide implant placement. CT-based navigation systems have been shown to increase accuracy of screw placement, particularly in significant deformities.^130,¹³¹ Clinically, however, freehand placement of pedicle screws has been shown to be safe and effective.¹³²^–¹³⁴ The author prefers to use freehand techniques for placement of pedicle screws in most primary cases and to use fluoroscopy or navigation in complex or revision instrumentation.

Numerous techniques have been described for determining the magnitude of angle needed to be corrected in the sagittal plane to restore balance. Perhaps the simplest way to do this is to cut a 3-foot film at the level of the planned osteotomy, balance the head over the pelvis, and measure the subtended angle. With the advent of digital radiography, printed 3-foot films are becoming rare, and this is no longer as good an option. A second option is to measure the angle subtended between a vertical line at the pivot point of the planned osteotomy and either the C7 or the C1 vertebral body. An osteotomy higher in the lumbar spine requires a greater angle of correction for a given amount of linear translation of the head.¹³⁵ Ondra et al.¹³⁵^–¹³⁷ described two mathematical models for determining osteotomy correction. Although these models are effective, the author finds them cumbersome to use in clinical practice.

It is generally recommended to overcorrect sagittal deformity by 5 to 10 degrees to compensate for loss of hip extension that occurs with aging. This recommendation applies to constructs extending to the sacrum. Aging patients with a normal lumbar spine are able to compensate for the loss of hip extension by rotating the pelvis through the lumbar spine. Patients who have fusions extending to the sacrum have lost this compensation. The loss of hip extension prevents normal stride through with gait; when this occurs, a patient who is able to stand in neutral sagittal balance is forced to walk in positive sagittal balance to have a normal gait. Preoperative examination of these patients should include careful assessment of the range of motion of the hip. Treating hip flexion contractures through either physical therapy or surgical releases may need to be considered before osteotomies.

Even with an extensive preoperative workup, it is sometimes difficult to predict how much correction of the deformity will be obtained at the time of surgery and with successive stages of the surgery. Consequently, operative plans are often flexible. Anterior interbody fusions with lordotic graft or cages may provide significant correction in patients with collapsed discs. Positioning on a four-post frame in the prone position often provides significant correction of a deformity that did not seem flexible. If one is planning a pedicle subtraction osteotomy through a level with mobile discs, it may be advisable to obtain an intraoperative lateral radiograph after the facet resection to determine if sufficient correction has been obtained through these methods to eliminate the need for pedicle subtraction osteotomy.

Outcomes of Complex Surgery for Adult Deformity

It is difficult to use the literature to assess the outcomes of complex deformity surgery and make generalizations. The wide range of presenting symptoms, deformity magnitude and flexibility, previous surgery, and comorbidities make it impossible to identify a homogeneous patient population. In addition, a wide variety of surgical techniques may be used to address similar problems. Randomized controlled surgical trials are essentially nonexistent. Most studies are retrospective case reviews.

Yadla et al.¹³⁸ performed a systematic review of outcomes of surgery for lumbar scoliosis. They showed that at a minimum 2-year follow-up there was consistent improvement in radiographic and clinical outcomes. The Oswestry Disability Index (ODI) showed an average 15.7 decrease. The Scoliosis Research Society (SRS)-30 showed a mean postoperative decrease of 23.1. These authors showed a relatively high (40%) complication rate.

Using a prospectively collected database, Daubs et al.¹³⁹ analyzed 46 patients older than 60 years who underwent a procedure in the thoracic or lumbar spine with more than five levels. Average ODI scores improved from 49 to 25 for a 49% improvement. The overall complication rate was 37%, with 20% of complications being defined as major.

In a prospective cohort study, Alpert et al.¹⁴⁰ used the 36-item Short Form Health Survey (SF-36) to assess 68 adults undergoing surgery for spinal deformity. These authors showed significant increases in physical function, social function, bodily pain, and perceived health change. They did not show a difference comparing patients older than 40 years with younger patients, and there was no difference in outcome observed in patients with complications.

In a matched cohort analysis, Glassman et al.¹⁴¹ compared patients with major complications, minor complications, and no complications. They noted no difference in scores on the SRS, SF-36, ODI, or visual analogue scale. There was a decrease in general health (12-item Short Form Health Survey [SF-12]) at 1 year for the group with major complications.

Li et al.¹⁴² performed a retrospective case-control study of 83 patients older than 65 years with scoliosis. Of these patients, 34 underwent surgery, and 49 were managed nonoperatively. The patients managed operatively were noted to have significantly less pain, better health-related quality of life, and better self-image and were more satisfied with treatment compared with conservatively treated patients. There was no difference in ODI or the physical and mental components of SF-12. The magnitude of preoperative deformity was not predictive of whether operative or nonoperative treatment was performed.

Two further studies have looked at operative versus nonoperative care. In a retrospective analysis of 55 patients, Kluba and Dikmenli ¹⁴³ showed that 24 patients who underwent operation had more significant pathology and symptoms preoperatively. At an average of 4 years postoperatively, surgical patients had better activity levels and less analgesic use but no difference in axial back pain. Two articles from the Spinal Deformity Study Group used prospectively collected data on nonmatched cohorts to look at leg pain and disability¹⁴⁴ and quality of life¹⁴⁵ and showed that at 2 years the operative patients were better off than the nonoperative patients despite having more disability, leg pain, and lower quality of life preoperatively.

Smith et al.¹⁴⁶ performed a risk benefit analysis based on patient age for surgical treatment of adult scoliosis. They showed that although the risks were higher for older patients, these patients had a disproportionately greater improvement in pain and function.