Scoliosis in Adults

Introduction

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The adult patient with spinal deformity represents one of the most challenging problems for the spinal surgeon. The scope of this problem appears to be increasing as the result of prolonged life expectancy and increased reader awareness in the lay and medical press. A recent survey of members of the Scoliosis Research Society revealed that more than one in three operations for scoliosis are performed on adults.

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Adult spinal deformities fall into one of several categories. Scoliosis, idiopathic, is the deformity requiring surgical treatment in the adult. Kyphotic deformities of various etiologies and spinal deformities secondary to previous surgery are also frequently seen.

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Treatment of these patients is complicated by a lack of clear-cut surgical indications in the adult, a higher complication rate, and coexisting medical problems such as diabetes, heart disease, and lung disease, secondary to a long history of cigarette smoking.

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It is imperative to adequately assess these patients from a medical viewpoint before undertaking major spinal reconstructive surgery in this population. An internist or pulmonary medicine expert may prove invaluable.

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The adolescent with scoliosis is usually a passive participant in the referral process, while the adult is a more active one. It is important to determine whether the presenting complaint is pain, cosmesis, pulmonary problems, or progression of the curve. Curve progression may be interpreted by the patient as a sensation that the body of losing height. On the other hand the patient may have been told, on the basis of serial radiographs, that the curve is indeed progressing.

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The etiology of scoliosis seen in the adult population is similar to that in the adolescent. Idiopathic scoliosis is by far the most common, with paralytic, congenital, and other known causes presenting with a frequency similar to that seen in the adolescent.
In attempting to achieve long-lasting patient satisfaction, determining the patient for whom surgical treatment is appropriate is as important as choosing the surgical technique. The most common indication for treating the adult patient is pain. Although the relationship of scoliosis in the adult to back pain is controversial, most authors agree that pain is more common in lumbar curves and curves of larger magnitude. Documented recent curve progression is also believed by most to represent a clear-cut indication for surgery. Progressive pulmonary insufficiency, the patient's concern over cosmesis, or functional decompensation may also be indications for surgery.

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Nonoperative treatment is the mainstay or certainly should be considered the initial mode of therapy in adult patients with scoliosis and back pain. After ruling out other more common causes of back pain, treatment, for the most part, consists of the standard care for back pain; heat, analgesics, nonsteroidal antiinflammatory medications, instructions in proper back care and mechanics, exercises supervised by a competent therapist, and occasionally external neuroaugmentive devices. Other treatment modalities include local facet injections and a semi rigid, well-lined underarm body brace.

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The surgical treatment of an adult with spine deformity may prove a complex undertaking. The approach to the adult differs from the adolescent in several specific areas. While curve correction is of major importance in the surgical treatment of the adolescent, pain relief with curve in the adult. Osteopenia is a common finding in the adult population with spinal deformity and may jeopardize attempts at rigid spinal fixation. A greater distribution of corrective forces must be considered. This can be achieved with the use of compression rods, multiple distraction rods, the use of sublaminar or spinous process wiring, or the use of the Cotrel-Dubousset implant. The lack of satisfactory or sufficient bone for grafting, the possible need to supplement fusion with allograft bone, and the importance of sagittal plane alignment are additional areas that add complexity to any surgical management scheme.
 

Surgical Treatment

Single Thoracic Curve

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Patients requiring treatment who present with thoracic curvatures may be managed by one of several different techniques, which vary depending on the severity of the curve and its flexibility. Curvatures of approximately 70 degrees or less and which are more flexible, with correction on side-bending of 40% to 50%, may be managed quite satisfactorily with a single-stage posterior spinal fusion and instrumentation by anyone of several constructs. Instrumentation options include Harrington, Luque, or the use of the Cotrel-Dubousset instrumentation. Stability of the Harrington implant may be augmented by using two or three distraction rods in the concavity of the curve, two proximal hooks with the distraction rod, a Harrington distraction rod with sublaminar wires, or a distraction rod in the concavity of the curve with a compression rod on the convexity.

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The Cotrel-Dubousset (C-D) system has been used extensively in adults. While the fixation furnished by this implant appears superior to other available constructs, it also has several disadvantages. The use of C-D in correcting rigid three-plane deformities of the thoracic or lumbar spine is less effective in adults than in adolescents and children. Derotation by rotating the rod 90 degrees is often not feasible and may result in dislodgement or hook pullout of the concave intermediate hooks. On the other hand, the fixation furnished by this implant appears superior to other available constructs.

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Thoracic curves greater than 70 degrees, particularly the more rigid curves, represent a more difficult problem. Single-stage posterior surgery in these curves has led to less than optimal results with a high rate of pseudoarthrosis, inadequate curve correction, and/or loss of curve correction postoperatively. A review reported superior results in these larger, more rigid curves with the use of a staged anterior fusion without instrumentation followed by a posterior spinal fusion with instrumentation.

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The first stage consists of a transthoracic anterior discectomy and osteotomy as necessary at each level; all the intervertebral disc material and osteophytes are removed back to the posterior longitudinal ligament. After removal of the bony endplates with an osteotome, a periosteal or osteoperiosteal flap is reflected off the anterolateral aspect of each vertebral body and a trough is cut into each vertebra. Harvesting cancellous bone graft from each vertebral centrum provides grafting material to be used in addition to the morselized rib. An interbody trough-type fusion is then done at each level using cancellous and cortical bone chips.

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One week later, a second-stage procedure is carried out that consists of total facetectomies and posterior osteotomies as necessary, along with instrumentation as previously described. Facet fusion, consisting of excision of the inferior articular facet and removal of all cartilage on the underlying superior facet, followed by cancellous bone grafting, is essential in achieving a solid fusion in the adult. Decortication is performed out to the tips of the transverse processes in both the thoracic and lumbar spine.

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In the lumbar spine, decortication and bone grafting are not performed in the midline or over the lamina to avoid the development of post fusion stenosis. The use of more complex implants subtracts noticeably from the area available posteriorly for bone grafting; this underscores the importance of performing a thorough facet fusion. The ideal material for bone grafting is autogenous corticocancellous and cancellous bone from the iliac crest. Other autogenous sources such as local bone from the spinous processes, and, when available, rib graft, are also used. Unfortunately adult patients, particularly women, frequently have a significant degree of osteopenia limiting the amount of autogenous bone available. In this situation, allograft is mixed with the harvested autograft. Fresh or frozen bone, such as femoral head or tibial plateau, would appear to be the optimal source of allograft.

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In the instrumentation of these more rigid curves, the use of stacked C-D rods in the concavity has proven helpful. In this technique a short distraction rod is placed between the intermediate vertebrae, frequently from T7 to T10, and a longer distraction rod placed between the end vertebrae. The apex of the curve is then pulled toward the midline with the use of two DTT (Device for Transverse Traction) devices between the two rods, tightened in compression. The convex rod is applied in the usual fashion, and standard upper and lower DTTs are used. The use of this two-stage technique on larger, more rigid curves has resulted in a decrease in the pseudoarthrosis rate as well as an increase in correction with less loss of correction postoperatively.

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In curves exceeding 90 degrees and demonstrating rigid ankylosis, a greater degree of correction can be obtained by vertebrectomy or a technique of vertebral column resection. If a total vertebrectomy is performed, a posterior distraction implant is ill advised. In this situation, L-rods with sublaminar wires or the C-D system is used to realign the spine by correcting at least two of the three plane deformities.

Thoracoplasty

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For many patients, the most cosmetically displeasing aspect of their scoliosis is the prominent rotational rib deformity, referred to as the rib hump. When this is the case, usually with rib prominences greater than 3.5 cm, a thoracoplasty through the same incision should be considered. If derotation with the C-D implant is possible, the need for a thoracoplasty is usually obviated, but in the adult a full 90 of derotation is frequently not possible.

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Rib resection is performed through the same midline incision used to expose the spine, and may precede or follow the spinal fusion with instrumentation. The trapezius muscle is detached from the midline fascia, and dissection proceeds dorsal to the paraspinal musculature to the rib prominence. The number of ribs resected depends on the appearance of the deformity. A common mistake is to remove too few ribs or to leave residual rib prominences proximally or distally; usually, six to eight ribs are removed. A wide exposure is achieved allowing visualization of the ribs to the posterior axillary line, and the periosteum overlying the prominent ribs to be excised is incised in a longitudinal fashion. The rib is subperiosteally exposed and detached, first at the posterior axillary line and then, using a Cobb elevator, from the transverse process and the vertebral body disc junction. The ribs should be removed intact, and prominent transverse processes on the convex side should also be removed to maximize the cosmetic result. A chest tube is inserted if any air leaks are apparent on wound irrigation; if not, a hemovac drain is placed and brought up to the skin laterally. The trapezius muscle is reattached to the midline. The bone obtained serves as a valuable source of bone graft.

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Postoperatively, the patients may have some transient decreased pulmonary function, which should resolve within 3 months after surgery. Long-term diminution in pulmonary function after thoracoplasty is unusual. The major complication of the procedure is a development of a pleural leak, which is treated intraoperatively or postoperatively with placement of a chest tube.

Thoracolumbar or Lumbar Curve

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Patients with thoracolumbar or lumbar curvatures can be treated surgically with either a single-stage anterior fusion with Zielke instrumentation or a posterior fusion with instrumentation. For flexible curves less than 80 and without significant lumbosacral pathology or a significant thoracic curve, the authors' preferred technique is the anterior approach with Zielke instrumentation. The advantages of this technique are the shorter fusion that is required, optimal correction, and low incidences of pseudoarthrosis. Some flattening or partial loss of lumbar lordosis is common with this implant system. Therefore, attention to detail is of paramount importance.

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The fusion levels are selected by instrumenting all vertebrae adjacent to the intervertebral discs that are wedged open to the convexity of the curve or that are significantly translated (greater than 0.5 cm) from the subjacent vertebrae. A portion of the concave outer annulus is left in place to act as a tether to prevent overcorrection. Loss of lumbar lordosis can be minimized by the placement of a screw posteriorly, in a posterior-to-anterior direction, into the apical vertebral body. Placement of anterior interbody bone blocks has also been beneficial in preventing the development of implant kyphosis.

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Although a single-stage posterior approach with instrumentation is a viable option, use of a distraction implant across the lumbar spine can lead to significant loss of lordosis. Square-ended Harrington rods prebent into lordosis, Luque instrumentation, or the C-D system may be used with this approach.

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The C-D system provides greater stability and improved fixation in the area of the spine, which is at significant risk of pseudoarthrosis. Lumbar lordosis can be maintained with the C-D implant, using the technique described by Cotrel. Generous facetectomies are performed to improve mobility of the curve and to allow posterior approximation into lordosis. Typically, there are two apical vertebrae into which are placed open hooks on the convexity. Hooks are only placed into the end vertebrae on the concavity of the curve. A mild distraction force may be provisionally applied across the concavity, although this is not always necessary, and the convex rod applied. Compression is then applied across all four hooks and held with C-rings, and the convex rod is rotated within the four rings toward the convexity. This rotation produces lumbar lordosis and corrects the scoliosis at the same time. The convex rod is then locked into the hooks in the usual fashion; further distraction, although not excessive, is applied across the concave rod and this too is locked.

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It is essential, with the use of posterior instrumentation and fusion in the lumbar spine, to address the sagittal contour. The upper end of the instrumentation cannot end at the apex of a significant thoracolumbar or thoracic kyphosis. It is occasionally necessary to instrument well up into the thoracic spine to prevent the development of a junctional kyphosis.

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A history of neurogenic claudication with radiculopathy is uncommon but may be seen with lumbar scoliosis. Nerve root compression is seen at the apex of the lumbar curve in the concavity or in the concavity of a lumbosacral fractional curve and may be caused by hypertrophic facets, a descended pedicle, or uncinate spurs. When surgery is necessary, treatment options include instrumentation and fusion, decompression, or a combination of the two. In milder cases, correction of the curve with instrumentation will usually afford adequate decompression. More severe nerve root compression may need formal decompression, and it is the surgeons experience that this should be combined with spinal fusion. Decompression alone requires significant bony resection and commonly leads to progression of the curve, increased back pain, and recurrence of radicular pain from pedicular kinking and nerve root entrapment.

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If there is a significant lumbar curvature associated with radicular stenotic pain (more than 30-40 degrees) anterior interbody fusion followed by posterior decompression with instrumentation has been used. Flexible lumbar curvatures of less than 40 may be seen, which arise de novo in the elderly population, associated with osteoporosis or degenerative disc disease. In this situation, and in the presence of reasonable bone stock, a posterior approach alone with decompression and instrumentation with a transpedicular implant may be sufficient. At 6 months after surgery, any evidence of delayed healing may be managed by either posterior augmentation of the bone graft or anterior interbody fusion.

Double Thoracic and Lumbar Curves

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A thoracic and lumbar double-curve pattern in which the lumbar curve is smaller in magnitude and more flexible than the upper curve may be managed by a selective thoracic fusion. While these guidelines have proven quite useful in adolescents, their applicability to adults is not as clear cut. Adult lumbar curves tend to be more rigid, and will not spontaneously correct as reliably as those in the adolescent. Furthermore, the presence of a junctional kyphosis between the two curves, which is commonly seen in the adult, eliminate the possibility of instrumenting only the upper curve. In the adult therefore, the performance of a selective thoracic fusion is the exception rather than the rule.

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Adults presenting with double-curve patterns requiring fusion of both curves pose a difficult problem. Balanced curves of lesser magnitude (less than 50) and with good flexibility may be managed satisfactorily with Single-stage posterior spinal fusion and instrumentation. Choices of instrumentation include a single Harrington distraction rod, distraction and compression rod, a double distraction dollar sign rod, distraction rods plus sublaminar wires, the L-rod system, or the C-D system. Balanced correction with maintenance of sagittal plane contours must be achieved.

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In larger, more rigid curves, or in patients with imbalanced deformity where the lumbar curvature is greater and more rigid, combined procedures should be considered. A first-stage procedure consisting of an anterior thoracoabdominal approach with fusion of the thoracolumbar and lumbar spine without instrumentation is followed after one week by a posterior fusion with instrumentation. The anterior discectomy and fusion are used to increase curve correction and to lessen the incidence of pseudoarthrosis. The use of the C- D system in this situation has proved to be most beneficial. Several different implant configurations may be used for instrumenting double curves. In less severe curves, a single rod on either side of the spine may be used with the placement of apical hooks into the convex apical vertebrae but without the use of intermediate hooks on the concave side of either curve. Rotation of these prebent rods permits simultaneous correction of the scoliosis with maintenance of sagittal plane curvature, although in the adult this rotation is technically difficult. More severe curves can be instrumented with a three or four-rod construct, with the use of double-barreled hooks above and below the junctional vertebrae. The corresponding concave rod goes into the enclosed inner channel while the lateral opening of the double hook accepts the convex rod. Insertion of the lumbar convex rod may be facilitated by a moderate amount of provisional distraction across the curve with the concave rod, but the convex rod across the lumbar spine should be compressed before final distraction of the opposite rod to prevent the development of an implant kyphosis at this level.

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A three-rod construct has proven useful in this situation. In this technique a distraction rod across the concavity of the thoracic curve, using standard intermediate hooks and ending in a double-barreled supralaminar hook, is placed first; tension is then applied with C-rings, which are rotated if possible. A provisional distraction rod is then placed across the concavity of the lumbar curve to facilitate correction of this curve. followed by a placement of a convex rod across the lumbar curve, utilizing the double-barreled hook, which is tightened into compression to maintain lumbar lordosis. The initial lumbar rod is then removed and a single long rod is placed in compression over the thoracic curve and in a moderate degree of distraction across the lumbar curve. Three DTTs are used in this construct. It is of utmost importance that any implant used not produce a thoracolumbar or lumbar kyphosis.

Fusion to the Sacrum

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Rarely is fusion to the sacrum necessary in the adult with idiopathic scoliosis. Indications for this most difficult spinal fusion include severe lumbar curves with continuation into the sacrum producing an "oblique take-off," severe degenerative disc disease below a lumbar curve, or a rigid lumbosacral fractional curve that does not correct on side-bending. Evaluation of lumbosacral pathology before attempting arthrodesis to the sacrum may include discography to assess disc status and the production of symptomatic pain and/or the use of facet blocks.

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The use of a single-stage posterior spinal fusion of a long curve to the sacrum has produced uniformly poor results. The incidence of pseudoarthrosis, loss of lumbar lordosis, and implant failure continues to be high with any form of treatment, but has been seen to be diminished with the use of a staged anterior and posterior approach. The first stage consists of an anterior thoracoabdominal approach with fusion of the lumbar curvature to the sacrum without instrumentation. The second stage consists of instrumentation with a posterior spinal fusion. The use of L-rods with segmental instrumentation and transiliac fixation with the Galveston technique, or the use of the C-D system with transpedicular fixation, has led to improved results when attempting to instrument down to the sacrum. Any rods used must be contoured to maintain lumbar lordosis and must be extended up into the thoracic spine if there is significant thoracic deformity.

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Complications of transpedicular fixation include the possibility of nerve root injury, dural laceration, and loss of fixation in osteopenic bone. The use of two or three screws on either side optimizes fixation. To facilitate this procedure technically, the surgeon may place a short rod through the transpedicular sacral screws with linkage between this rod and a rod through the rest of the curvature with the use of a domino. It should be noted however that the use of two rods and a domino results in a somewhat less rigid construct than is achieved with the use of a single rod. Also, L-rod fixation across the pelvis occasionally results in sacroiliac pain which may necessitate rod removal.

Results and Complications

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A high percentage of satisfactory long-term results can be obtained in the surgical stabilization of adult scoliosis, but the variable results obtained in terms of pain relief, curve correction, and reversal of pulmonary dysfunction have discouraged some authors. Pain relief is often incomplete after surgical correction of adult scoliosis, a point meriting serious consideration when undertaking such surgery with pain as the primary indication. Despite the lack of complete pain relief after surgery, the experience of most authors has been that an acceptable reduction in pain with a high level of patient satisfaction is obtained.

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Curve correction is less in the adult than in the adolescent with idiopathic scoliosis. While curve correction of more than 60%-70% is obtained with the use of newer implants in the flexible adolescent spine, the average correction in most adult series has ranged from 30%-40%. In addition, all authors report a significant loss of correction postoperatively. Improvement in pulmonary function after surgical correction of adult scoliosis has been unpredictable, with most patients returning to their baseline pulmonary status.

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Surgical complications in the adult are similar to those in the adolescent patient treated for scoliosis, but appear to occur with much greater frequency. Pseudoarthrosis is the most common major complication in adults, occurring in 7%-17% of patients. In one review of patients with adult idiopathic scoliosis, a 15% rate of pseudoarthrosis was seen with single-stage posterior fusion with Harrington instrumentation. By comparison, a review of patients treated by staged anterior and posterior approaches revealed no failures of fusion in most patients after an average of 4 years. Wound and urinary tract infections, cardiopulmonary problems, neurological damage, thrombophlebitis, and loss of lumbar lordosis are all complications of scoliosis surgery in the adult.

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Finally, in the evaluation of the adult treated surgically for adult scoliosis, it is evident that the age of the patient plays a significant part in the expected outcome of surgery. The approach to spinal deformities in the elderly represents a major undertaking. The results are significantly less satisfactory than in the young adult. Kostuik reported his results in patients over the age of 50, and related an extremely high complication rate including a 27% pseudoarthrosis rate, a loss of lumbar lordosis in 13 of 73 patients, kyphosis above the fusion secondary to osteoporosis in 9 cases, and in general a 25% chance of poor results. This underscores the importance of approaching these elderly patients with extreme caution.

Salvage Surgery

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Repeat surgery on an adult who has undergone previous spinal fusion for spinal deformity is one of the most difficult undertakings facing the spinal surgeon. The patient's most common presenting complaint is pain. Increasing deformity, commonly in the sagittal plane, respiratory failure, and occasionally neurologic dysfunction are also seen. One or more pseudoarthrosis are frequently present in this situation, but loss of curve correction either through bending of a solid fusion mass or adding on above or below previously fused segments may occur in the case of a solid fusion.

Pseudoarthrosis

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In all series failure of fusion is highest in the thoracolumbar and lumbar spine, particularly when single-stage posterior fusion is performed. The etiology of the deformity includes idiopathic, paralytic, and congenital scoliosis, as well as kyphotic and post traumatic deformities.

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Successful repair of a pseudoarthrosis requires even more rigid adherence to technique than primary spinal fusion. Meticulous resection of any fibrous tissue at the pseudoarthrosis site is essential. While no statistics exist documenting the superiority of rigid internal fixation in this setting, it is certainly the preferred technique at this time. The C-D implant, used in compression, affords stabilization and the capability for correction where indicated. Decortication of the preexisting fusion mass down to bleeding bone and the addition of autologous iliac crest graft enhance the chances of achieving successful fusion. Even under these ideal circumstances the successful repair of pseudoarthrosis in adults, particularly in the lumbar spine, is by no means assured, and consideration should be given to an anterior spinal fusion to enhance the results.

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More than one pseudoarthrosis is found when any single pseudoarthrosis exists. It is therefore essential to explore the entire fusion mass carefully. A lamellated outer cortical shell of bone may be suspended from one level to the next appearing to signify a solid fusion, but when this thin shell of bone is removed, gross motion is frequently found. It is not uncommon to surgically document a pseudoarthrosis at a level that has been believed, on the basis of a previous exploration, to be solidly fused.

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Loss of curve correction may occur secondary to a pseudoarthrosis or in the face of a solid fusion. When the magnitude of the deformity and its rigidity are such that adequate correction cannot be obtained with standard instrumentation techniques, an osteotomy may be performed. The osteotomy technique is useful in the presence of ankylosed facets; it may be performed at the level of the pseudoarthrosis or through a solid fusion. The fusion mass is exposed to its most lateral extent or to the tips of the transverse processes bilaterally. The transverse processes are usually identifiable even under the most solid of fusions. The osteotomy will proceed from the midline across the facet joint midway between the pedicles above and below, and out between, the corresponding transverse processes. A gouge or osteotome is used to remove the outer cortical shell of the fusion mass and then a gouge, osteotome, or high-speed air drill is used to carefully thin out the cancellous bone down to the level of the inner cortex. The inner cortex is carefully broached using either an air drill or curette. This may be easiest in the midline where the inner cortex is the thinnest. Once the dura is adequately visualized the osteotomy can be extended to either side using a Kerrison rongeur, passing between the pedicles and the transverse processes. Adequate bone should be resected to ensure that with compression no bony impingement on the neural elements occurs. It is most important to generously undercut the osteotomy site to ensure that no damage to the neural elements occurs.

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Depending on the number and levels of osteotomies, correction may be achieved in two planes. The nature of the deformity will dictate the instrumentation chosen. Bilateral compression implants are used with kyphotic deformities, and distraction coupled with compression implants are used for a frontal plane curvature.

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More severe deformities, which cannot be corrected with simple posterior osteotomy and instrumentation, can be addressed in one of two ways. Staged posterior exploration and osteotomy with interval halo femoral traction to obtain correction followed by posterior instrumentation, is a viable treatment option. Another approach in these severe problems is the use of vertebral resection. This may consist of either a posterior, transpedicular decancellation or open vertebral decancellation performed through an anterior approach.

Flat Back Syndrome

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Symptomatic loss of lumbar lordosis has been noted to occur, most commonly after the use of distraction instrumentation across the lumbar spine, although this symptom complex may be seen occasionally in patients who have had lumbar spine fusion without instrumentation. The patients present most commonly with the inability to stand erect and with back pain. Loss of lumbar lordosis or the presence of thoracolumbar kyphosis is seen on standing lateral radiographs, and the patient's forward list is noted by dropping a vertical line from the body of C7 that falls anterior to the sacral promontory.

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The treatment of this syndrome is extremely difficult. One or more posterior closing wedge osteotomies and fixed with compression instrumentation using either the C-D system or heavy Harrington compression rods, are performed. An average of 20 of correction can be obtained per osteotomy level.

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The ability to maintain correction obtained at surgery relates to the initial ability to center the body of C7 over the sacrum on standing. Postoperative loss of correction, particularly when such sagittal plane imbalance is present, is a significant problem but it occurs less commonly when an anterior interbody fusion is performed. Most patients benefited from their corrective osteotomies. However, more than 50% of patients continued to lean forward, and many patients continued to have moderate to severe back pain. As in any of the foregoing salvage techniques, pseudoarthrosis, dural tears, failure of fixation devices and neuropraxia are associated complications.

Kyphosis

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Kyphosis in the adult may arise from a number of causes including untreated Scheuermann's kyphosis, congenital deformity, neuromuscular disease, osteopenia, and spondylitis. A variety of surgical approaches may be considered. Preoperative medical evaluation and treatment of the patient are imperative, particularly in the older patient with progressive kyphotic collapse secondary to osteopenia.

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The curve should be evaluated to determine the relative rigidity, measuring maximal correction on supine lateral extension radiographs. The possibility of neurological involvement, which has been reported in all these entities, should be appreciated; the use of magnetic resonance imaging (MRI) to assess cord compression of the thoracic spine has been extremely helpful. Finally, the adequacy of bone stock should be assessed.
Supple curves correcting to less than 55, without anterior cord compression, or curves of less than 55 in which correction is not necessary, may be treated by a single-stage posterior fusion with instrumentation. Dual heavy Harrington compression rods, L-rods, and the C-D implant used in compression bilaterally are implant options. Use of the L-rod technique in these kyphotic deformities has been associated with a high incidence of progressive kyphosis above or below the fusion with less than an optimal result, and is therefore not favoured in the treatment of most kyphotic deformities.

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If significant cord compression exists anteriorly, decompression is necessary before any attempt at correction.

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Preoperative traction is contraindicated in the treatment of kyphotic deformities with cord compression. Decompression may be performed through an anterior transthoracic or thoracoabdominal approach, a posterolateral costotransversectomy approach, or a Michelle-Krueger approach involving the resection of the transverse process and pedicle, affording visualization of the vertebral body and anterior cord. The anterior approach is preferred as it appears to be safer, affords better visualization for decompression, and certainly enhances one's ability to perform an anterior approach.

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Rigid or more severe curves require an anterior approach. In cases in which correction is not desired, discectomy and anterior spinal fusion in situ utilizing a strut graft technique is performed. Correction can be achieved with the use of a two-staged approach; the first stage is osteotomy in the case of a type II congenital kyphosis, or release of the anterior longitudinal ligament in Scheuermann's kyphosis; the second stage consists of a posterior fusion with instrumentation.

Spondyloarthropathy

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Ankylosing spondylitis is the most common of the rheumatic disorders, including psoriatic arthropathy, Reiter's syndrome, arthropathy associated with inflammatory bowel disorders, and rheumatoid arthritis, which can lead to fixed spinal deformity. These patients present with progressive kyphotic deformity of the cervical or thoracic spine or loss of lumbar lordosis. This is initially associated with pain, but eventually results in a painless ankylosis. In more severe cases, the patient is unable to stand upright even with knee flexion, producing a severe functional disability.

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Beginning with Smith-Petersen, Larson, and Aufrane in 1945, several authors have described spinal osteotomy for correction of this deformity. Concern over reports of death and neurological complications following this procedure, particularly in the series presented by Law, limited the acceptance of this technique.

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Evaluation of the patient is essential because the source of the deformity may occur at anyone of several sites. The flexed posture may be related to hip flexion contractures, which, if present, should be addressed before attempting spinal surgery. Spinal deformity may occur in the lumbar spine, the thoracic spine, or at the cervicothoracic junction. The most common site of pathology in the spine is in the lumbar region, with loss of lumbar lordosis and pelvic tilting. The lumbar spine is the safest site to perform an extension osteotomy, which is generally performed between L2 and L3, or between L3 and L4.

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The technique of the osteotomy is similar to that previously described. As much as 2 cm of bone and a portion of each pedicle may be resected to achieve maximum correction. It is essential that the apex of the osteotomy lie anterior to the dural tube so that the neural elements are not stretched when the osteotomy is closed down. The ideal apex is at the junction of the posterior longitudinal ligament with the intervertebral disc. Correction occurs by virtue of fracturing through the ossified anterior longitudinal ligament and disc space in tension. As in other deformities of sagittal imbalance, the key to maintaining correction has proven to be the ability to center the plumb line from C7 over the sacrum.

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Occasionally the primary deformity from ankylosing spondylitis is in the thoracic spine. When possible it is through the lumbar region, because this is safer. If correction and stabilization through the thoracic spine is necessary, a two-stage procedure consisting of a first-stage anterior osteotomy and interbody fusion followed by posterior osteotomies with compression instrumentation is the preferred approach.

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Kyphotic deformity of the cervical spine at the cervico-thoracic junction is sometimes seen in the spondyloarthropathies. Most authors recommend performing surgery at this level under local anaesthesia with the patient immobilized in a halo and in a sitting position. Osteotomy at the C7-Tllevel is considered safest because the vertebral artery is anterior to the transverse processes at this level, and injury to the nerve root at risk, C8, is likely to cause less disability than at other cervical roots. Wide laminectomies from C6 to T2 with decompression and visualization of the C8 nerve root bilaterally and slow, controlled correction has proven safe and efficacious.

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With the evolution of newer techniques, whereby a spinal shortening procedure is performed, the correction of these crippling deformities has proven a viable undertaking. The complications of any spinal osteotomy, such as pseudoarthrosis, neurological damage, dural laceration, and implant failure, also exist for this procedure; further particular attention should be paid to postoperative ileus, which is common in these patients and should be treated prophylactically with the institution of nasogastric drainage.

Thoracic lordosis

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Thoracic lordosis or hypokyphosis is most commonly seen in primary scoliotic deformities, and the surgical management of this condition consists of that described for scoliosis. The occasional patient is seen in whom primary thoracic lordosis leading to a decrease in chest volume necessitates treatment. Scoliotic deformities also exist in which the thoracic lordosis is a significant treatment consideration and is not addressed by the use of standard instrumentation techniques.

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Treatment of thoracic lordosis can be through either a single-stage or two-stage technique. Single-stage posterior instrumentation and fusion with the L-rod system and sublaminar wires afford some correction of thoracic lordosis, but it is generally inadequate in the rigid adult spine when significant sagittal plane correction is necessary. Similarly, while adolescent patients with thoracic lordoscoliosis can be instrumented with the C-D system and, through rod rotation can achieve correction into thoracic kyphosis, the more rigid deformity with inadequate bone stock found in the adult makes this technique less reliable.

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A combined technique, consisting of a first-stage anterior approach in which rib osteotomies at the posterior rib angle at multiple levels and multiple-level intervertebral discectomies are performed. This is followed by a posterior procedure in which similar rib osteotomies are performed on the opposite side and segmental sublaminar wires are used to pull the spine and the attached posterior rib cage to the pre bent distraction by L-rods, creating thoracic kyphosis. This technique has proven useful in the treatment of patients having rigid thoracic lordosis greater than -30 degrees and presenting with incipient or frank pulmonary dysfunction.

Postoperative Management

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Other than in cases in which vertebrectomy is performed or in which spinal stability is believed to be severely compromised, the patients are allowed out of bed between stages to a bedside chair or with a walker. Most patients are out of bed within 2 to 3 days postoperatively and are allowed to begin walking. A standing mold is taken for a removable thoracolumbosacral orthosis (TLSO) which the patient wears fulltime except when in bed or in the shower. Adult patients with good bone stock who are believed to have been rigidly fixed with a C-D implant are occasionally managed postoperatively without an orthosis. However, most patients treated with the C-D system, and all patients treated with Luque or Harrington instrumentation, are advised to wear a brace after surgery.
Traction is rarely used between stages as it has not been found to lead to increased curve correction. The occasional patient with paralytic scoliosis and significantly diminished pulmonary function may be managed by preoperative halo-wheelchair traction to optimize respiratory capacity, which is then continued between stages. Patients are usually discharged 7 to 10 days after surgery. Walking 1 to 2 miles is encouraged in the early postoperative period. If roentgenograms show the implant to be in satisfactory condition with no loss of correction, patients are allowed to return to work 2 to 4 months after surgery, as well as to resume sexual activities.

Conclusions

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The spectrum of adult spinal deformities is varied, but several common threads may be seen in these difficult problems. In an increasingly older patient population, it is imperative to adequately evaluate the patient's preoperative medical condition as well as to exhaust all possibilities for conservative management. The indications for surgery in any given case need to be carefully evaluated and compared to the sometimes disappointing results and complications seen in these conditions. Reliance on newer implants to compensate for inadequate preoperative planning, lack of attention to the complex three-plane deformities seen, or failure to carry out meticulous fusion techniques are factors contributing to certain failure. On the other hand, many adults with complex spinal deformities may be helped with the new techniques available to the spinal surgeon.

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