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THORACIC AND LUMBAR DEFORMITY
Rationale for Selecting the Appropriate Fusion Technique
(Anterior, Posterior, and 360 Degree)
Susan M. Liew, MD, MB, BS(Hon), and
Edward D. Simmons, MD, BSc, CM, MR, FACS, FRCS(C),

DEGENERATIVE DISC DISEASE KYPHOSIS
Degenerative disc disease kyphosis is the most common deformity seen in a general spine practice. In the elderly population, this deformity is commonly associated with canal stenosis. Occasionally, postlaminectomy instability is seen. The most comfortable posture for these patients is in a flexed position, but the deformity is usually tolerable, albeit with pain.

Treatment. The authors prefer decompression as needed and posterolateral fusion with segmental instrumentation contoured into lordosis and iliac crest graft (sometimes supplemented with allograft), followed by a chairback brace. Occasionally an anterior release and fusion is necessary for a rigid deformity. The risk of additional surgery, however, must be taken into account for patients over 60 years of age, ^{19, 24} and the physiologic age of the patient may determine the extent of surgery.³ An appealing alternative in these patients is a posterior lumbar interbody fusion (PLIF), which can be added to a standard posterolateral fusion at the level at risk for delayed healing or pseudarthrosis. The advantage of this is in allowing a 360-degree fusion without requiring a separate anterior exposure. Rigidity of the deformity is assessed preoperatively via a lateral spine x-ray in the supine position with a bolster under the apex of the kyphosis. The authors have not found that the use of the Andrews table compromises lordosis, as long as care is taken to extend the foot end of the table and recreate lordosis before carrying out the instrumentation.

The authors have observed that osteoporosis per se is not a risk factor for bone healing. Fusion rates in the elderly can be good if proper technique is used along with autogenous bone graft. Smoking is a risk factor, as in all ages, as well as diabetes and poor nutritional status. For most of these patients, posterior instrumentation with posterolateral fusion is adequate without the necessity of more aggressive front and back procedures. Careful attention must be paid to the medical status of the patient, and the surgeon must try to accomplish realistic goals for the patient with the least morbidity possible. An eggshell decancellation procedure can be used, if necessary, to gain further sagittal plane correction. This can obviate the need for a separate anterior approach.'

In this older age group, the author, have not found a significant problem with adjacent instability problems in the long-term.^{2, 50} Use of a 1/4-inch rod has been associated with few breakages. Segmental fixation with pedicle screws has superior holding power. Interbody fusion treatment options include PLIF, with carbon fiber or metal cages or bone block, and anterior lumbar interbody fusion (ALIF), in the form of carbon fiber or metal cages, bone block, and femoral allograft with or without fixation.

IATROGENIC FLAT BACK
The iatrogenic loss of lumbar lordosis, which has been referred to as flat back, is a not too uncommon problem that may require surgical correction. Two common causes are previous Harrington instrumentation and fusion for scoliosis (usually below previous scoliosis surgery) and inadequate contouring of lordosis with the use of more recent segmental instruments. Many of the same considerations apply to this group as in the degenerative disc disease kyphosis group except this group of patients is generally younger.

Treatment. The authors recommend removal of previous instrumentation, posterior closing wedge osteotomy at L3-4 or L4-5, posterolateral fusion with segmental instrumentation and iliac crest graft, and TLSO brace. Occasionally an anterior release and fusion is necessary for larger or more rigid deformities. Rigidity of the deformity is assessed preoperatively via a lateral spine x-ray in the supine position with a bolster under the apex of the kyphosis. The amount of correction is assessed by the lateral 3-foot standing spine x-ray to bring C7 back over S1. The site of the osteotomy should be below the conus at the level of an unankylosed disc space or new anterior release. The authors find that when an anterior release is not needed for correction, anterior fusion has not been necessary, once the patient becomes balanced. Other treatment options include anterior release, either single level or multilevel, and sequential anterior fusion.

IATROGENIC SPONDYLOLISTHESIS
The most common cause of iatrogenic spondylolisthesis is a previous wide laminectomy without fusion, in which the facet joints are excessively damaged or removed.

Treatment. For a small slip with recurrent symptoms at the same level, the authors recommend decompression with segmental instrumentation and posterolateral fusion with autogenous iliac crest graft, followed by a chairback brace.⁵⁶ The authors have found that the slip is always reducible to some extent, particularly with pedicle screw fixation.¹ Double-threaded screws can be used to obtain reduction if necessary. Despite a high fusion rate with this technique, the overall clinical outcome is poorer than those with isthmic or degenerative spondylolisthesis, ⁵⁵ and some get better results with a circumferential fusion.²⁴ Other treatment options include additional PLIF, in the form of carbon fiber or metal cages and bone block and additional ALIF to effect anterior release, in the form of carbon fiber or metal cages, bone block, and femoral allograft with or without fixation.

POSTTRAUMATIC KYPHOSIS
The most common problem of posttraurnatic kyphosis is pain in the region of the kyphos of an old thoracolumbar burst or compression fracture, probably caused by a combination of disc pathology and posterior incompetence with imbalance. Thin patients may complain about the gibbus per se or may be getting fatigue pain in the area of compensatory hyperextension below the kyphos. Compensatory hyperlordosis of the spine below the kyphos can also be pain producing.

Treatment. To determine the appropriate surgical management, extension and bending radiographs must be done to determine flexibility. For a small or flexible deformity with a pseudarthrosis in situ, fusion with correction as much as possible, posterolateral fusion with segmental instrumentation and iliac crest graft, and TLSO brace can be carried out. For a larger or fixed deformity, the authors recommend anterior corpectomy, femoral strut allograft with local bone graft, plate instrumentation, and TLSO. The authors have not found additional posterior release and fusion to be routinely necessary, but this depends on the extent of the deformity. Femoral allograft is clinically satisfactory,⁵⁰ but others report problems with subsidence.³⁶ The authors prefer not to take large grafts from the iliac crest, and problems with fractures have been reported.²⁰ Whatever material is used as a strut, however, it should cover at least 30% of the end plate,¹⁴ which is why the authors also prefer not to use fibula or rib grafts as have been described.³⁰

Titanium mesh cages (Harms) can also be used effectively. In the future, a prosthesis may also become available with the ability to preserve some motion.⁴⁰ Thoracoscopic anterior approaches for release and possibly corpectomy and reconstruction are also an alternative.^{42, 43} The authors prefer to use a plate ^{21, 25} rather than a single rod system. A double-rod system³³ is probably just as good as a plate and depends on the surgeon's preference. There are also future possibilities with a spinal nail.¹⁶ Multiple posterior osteotomies can be used for these deformities as well.³⁸

ANKYLOSING SPONDYLITIS (LUMBAR CORRECTION)
The patient commonly presents with a progressive deformity and inability to see ahead when standing. These deformities are not flexible. Another cause of pain with or without a progressive deformity can be a lesion of spondylodiscitis.
Figure 1. A-D, A 43-year-old man with ankylosing spondylitis and progressive kyphotic deformity with increasing pain. Note associated lesion of spondylocliscitis at T1 1-12. Treated with posterior resectionextension osteotomy at 1-3-4 and long instrumentation above level of spondylocliscitis.

Treatment. The authors prefer posterior resection-extension osteotomy at L3-4 (with anterior osteoclasis), posterolateral fusion with segmental instrumentation and local bone graft, and TLSO.⁶⁰ A sagittal assessment of the entire spine must be made²³ via a 3-foot standing lateral x-ray. A cervical deformity is addressed at the cervical spine. The thoracic and lumbar spine must be assessed as a whole (i.e., if the deformity is marked in the lumbar spine [loss of lumbar lordosis]). Whether there is concurrent thoracic deformity or not, a lumbar osteotomy is beneficial. Concurrent lesions of spondylodiscitis must be included in the fusion (Fig. 1). When planning the amount of correction, the surgeon should remember the spine is stiff and avoid overcorrection. Once the sagittal balance has been restored, the authors have not found it necessary to perform anterior fusion, although some do.¹⁰ Studies have also shown satisfactory results with posterior-only surgery ^{69, 70} and with the use of the technique of a posterior transpedicular decancellation. closing wedge osteotomy. ⁶⁴ Other forms of bone graft have not been necessary, and it has been found that allograft works well in this particular disease state.¹⁰

ANKYLOSING SPONDYLITIS (THORACIC CORRECTION)
Presentation is as for ankylosing spondylitis (lumbar correction), although the patient has a predominant thoracic deformity with a normal or increased lumbar lordosis.

Treatment. For a flexible deformity, the authors recommend preoperative halodependent traction for correction, multiple posterior osteotomies, posterolateral fusion with segmental instrumentation and local bone graft, and a TLSO brace. For a rigid deformity, a staged procedure is performed: (1) anterior release (without taking the diaphragm down) with rib grafts; (2) correction with halodependent traction; and (3) multiple posterior osteotomies, posterolateral fusion with segmental instrumentation and local bone graft, and hyperextension brace. To determine flexibility, a supine x-ray with a bolster under the kyphos is necessary. Multiple osteotomies are necessary because of the small canal and relatively fixed position of the cord. Anterior thoracoabdominal surgery should be avoided. The diaphragm should not be taken down because these patients have little or no chest excursion during respiration and breathe solely with their diaphragms. Staged procedures in a fixed deformity are safer to allow awake control of the correction and to minimize insult to the spinal cord blood supply. The authors have found an average 7 to 8 degrees of correction per level is possible with neurologic safety. Other treatment options include additional anterior instrumentation.

INFECTIOUS SPONDYLITIS
Infections are not infrequently seen in the thoracolumbar spine, and the mainstays of treatment remain chemotherapy and supporting the spine in position until autofusion can occur.

Treatment. A full discussion on the treatment of infections is beyond the scope of this article, but generally the surgical management is reserved for infections refractory to chemotherapy, deformity secondary to collapse, and neurologic instability. For those with deformity secondary to vertebral body collapse, perform an anterior discectomy/corpectomy, femoral allograft or Harms cage, anterior plate, then use a TLSO, preferably after the infection has been treated. For those who require debridement of the infection, such as is sometimes necessary in tuberculosis, the same approach is well proven,⁵ used with the principle of trying to use minimal instrumentation in the infected area, while still leaving a stable construct. Rarely, posterior debridement may be necessary, obviously requiring a posterior approach instead (Fig. 2). The authors do not think it necessary to add additional posterior instrumentation after an anterior procedure. The results in tuberculosis are probably the best subgroup studied.⁴⁴ Other treatment options include autograft, metal cage, anterior screw and rod system, and sequential posterior instrumentation.
Figure 2. A, Lateral radiograph of 75-year-old man with kyphotic collapse and deformity in thoracic spine secondary to fungal infection. B, Sagittal MR imageof samearea. C, PostoperativeAP radiograph of spine with anterior CASP plate and femoral allograft strut.

TUMORS
Metastatic tumors are the most common and usually are found in the vertebral body rather than the posterior elements and may present with kyphotic collapse in addition to pain or neurologic instability. Consideration must also be given to the patient's prognosis and previous or planned radiotherapy.

Treatment . For anterior collapse alone, the authors recommend anterior corpectomy, femoral allograft or metal cage strut, anterior plate, TLSO. For posterior destruction alone, the authors recommend posterior decompression as necessary, with posterior segmental instrumentation and fusion. In cases involving anterior and posterior structures or evidence of concomitant instability, the authors recommend both procedures, if possible, as singlestage surgery. Generally, a metal cage strut is used for patients with a poorer prognosis. The issue of a prophylactic anterior and posterior instrumentation and fusion is controversial, although recommendations have been made according to the probability of collapse. ⁶³ The authors have found it necessary only to address the site of the pathology and continue to observe the patient. Other treatment options include allograft or bone substitute, cement, metal cages, and additional posterior surgery for all patients.

SCHEUERMANN'S KYPHOSIS
In the adult population, presentation of Scheuermann's kyphosis may be in later life with thoracic discogenic pain or lumbar pain secondary to compensatory hyperlordosis below the thoracic kyphosis. On rare occasions, progressive deformity caused by Scheuermann's disease in adolescents may need to be treated (if >70 degrees or when it causes cord compression).⁴

Treatment . If the kyphotic deformity corrects to 50 degrees or less on a supine hyperextension film over a bolster, a single-stage posterior approach is usually adequate. The authors recommend posterolateral fusion with segmental instrumentation and iliac crest graft and hyperextension brace. More rigid, severer deformity needs a first-stage anterior release and fusion with rib or fibula³² graft, ⁷¹ followed by a posterior procedure. Milwaukee brace treatment in adolescents has proven value. Flexibility is determined by supine lateral xray with a bolster under the kyphos. If the kyphosis can be reduced to less than 50 degrees, posterior instrumentation and fusion alone is adequate. Conversely, if it cannot be reduced to less than 50 degrees, an anterior release and fusion is also indicated. This is probably a good indication for consideration of anterior thoracoscopic surgery.^{46, 52} Those presenting in later adult life generally remain in good sagittal balance and have a problem with pain rather than the deformity per se and so usually do not require large corrections. ⁷¹ The authors and others³⁹ have not had any problems with significant recurrence of deformity with posterior-only procedures. The authors have not seen a case of cord compression with this condition although this has been reported. Good results with a posterior-only procedure, involving decompression from the posterolateral approach, have been reported.⁴ Other treatment options include additional anterior internal fixation.

OSTEOPOROTIC KYPHOSIS
The best treatment of osteoporotic kyphosis is prevention of osteoporosis. Although deformity is a problem, the most common presentation is that of pain rather than the deformity, which may be exacerbated by a crush fracture.

Treatment . Most osteoporotic fracture-related problems can be treated with hyperextension bracing. Posterolateral fusion with segmental instrumentation and iliac crest graft (sometimes supplemented with allograft and bone morphogenetic protein) and hyperextension brace can be carried out if necessary. Education, adequate nutrition, and strengthening exercises are of value at all stages. Hormone therapy for postmenopausal women should be considered, along with vitamin D and calcium supplementation and other medical management. A concurrent degenerative myopathy exacerbates the pain and and deformity, and active resistive exercises are to be encouraged, especially in the stages of early deformity. There has been no need for circumferential fusion because it has not been proven that these patients have any problems producing a fusion mass; this has been the experience in the authors' practice as well. A posterolateral fusion has been usually adequate, especially given the ages and medical morbidity of some of these patients. Some have reported fixation problems in relation to the low bone mineral density of these patients,⁴⁸ but the authors have not had a major problem in this regard. It must be kept in mind that the aim is to maintain or attain a sagittal balance rather than a complete correction per se. Anterior release and strut grafting may be necessary, however, if fixed, severe kyphotic deformity is present. Other treatment options include anterior strut fusion with or without release and fixation.

DEGENERATIVE SCOLIOSIS
Some degree of scoliosis and kyphosis (as discussed in the degenerative disc disease kyphosis section) is common in patients presenting with lumbar degenerative disease. It must be recognized that although the lumbar curve may be the most obvious, the problem often occurs in the concavity of the lumbrosacral curve below.

Figure 3. A-G, A 73-year-old man with neurogenic claudication and progressive degenerative scoliosis with spinal stenosis. Treated with posterior decompression and instrumentation with posterolateral fusion. H and /, Corrective techniques for degenerative short segment lumbar curves. Distraction on concave side also provides further indirect decompression of neural foranima.

Treatment. The authors prefer posterolateral fusion with or without localized decompression, segmental instrumentation with indirect decompression and correction, iliac crest graft (sometimes supplemented with allograft), and chairback bracing. Comments similar to those in the section on degenerative disc disease kyphosis also apply to these similar pathologies, which occur in the same age group. The symptoms and the physiologic age of the patient must be considered together to enable the least surgery necessary. These patients cannot be made nornial. Commonly, in older patients, a short fusion of the lumbosacral curve with decompression (which may be indirect by distraction of the concavity or in the usual direct manner) may be all that is necessary to relieve most of the pain and reattain reasonable coronal and sagittal balance (Fig. 3). The lumbar curve may be a major deformity needing correction along with the lower lumbosacral curve. In these cases, the principle is the same. It is important to have the spine balanced above the levels fused, particularly in the sagittal plane.⁵⁹ The authors have had satisfactory results with a posterior procedure alone as have others²⁸ but recognize that fusion to the sacrum has the highest pseudarthrosis rate and remains controversial.³⁰ The authors prefer not to fuse L5-S1 if possible. Discography may be used in helping to determine the main level of pain generation. It is essential that physiologic lordosis be maintained or attained to prevent ascending ftisions being necessary. Balance in both the sagittal and that coronal planes is the largest correlate for risk of adjacent segment breakdown.⁵⁴ Rotational correction of longer degenerative curves can be carried out with simultaneous improvement of the scoliosis and improved lordosis⁵⁷ (Fig. 4). Other treatment options include additional PLIF in the form of carbon fiber or metal cages and bone block and additional ALIF with carbon fiber or metal cages, bone block, or femoral allograft with or without fixation.

Figure 4. A-G, A 73-year-old woman with spinal stenosis associated with scoliosis. Note retrolisthesis of D with kyphotic malalignment. Rod rotation maneuver used for primary correction of deformity, changing scoliosis into lordosis.

ADULT IDIOPATHIC SCOLIOSIS
The most common reason for presentation is lumbar pain with or without decompensation below the original curve. Progression of deformity is a recognized potential problem throughout adult life.

Treatment . Many of the procedures for these deformities can be done from a single-stage posterior approach. Anterior release and fusion is also necessary in large, rigid deformities, particularly if the spine is kyphotic at all, in the coronal plane. Anterior instrumentation and fusion as a single-stage isolated procedure can be used for primary thoracolumbar curves (Fig. 5).

Figure 5. A-D, A 28-year-old woman with lumbar scoliosis with associated congenital anomaly at the lumbosacral junction and oblique "take-off."

For progression of the original curve or intractable pain below the original curve, the authors recommend instrumentation with correction to attain coronal and sagittal balance, iliac crest graft (sometimes supplemented with allograft), and TLSO. For decompensated curves, the whole complex must be fusedposterolateral fusion with segmental instrumentation with correction, iliac crest graft (sometimes supplemented with allograft and bone morphogenetic protein), and TLSO. For stable curves and older patients, the authors recommend a limited posterolateral lumbar fusion with segmental instrumentation and iliac crest graft and a chairback brace. The spine must be balanced with the upper end vertebra parallel or as close to parallel to the horizontal as possible to prevent future adjacent degeneration.⁵⁴

Similar to patients with degenerative scoliosis, it is advantageous to preserve L5-Sl, but basic principles should be followed.⁸ By the time many of these patients present, the curves are stiff. Bending x-rays are necessary to assess this. Anterior release and fusion may be necessary in severe, stiff deformities. Note that pulmonary function may be compromised to varying degrees, so the authors prefer that posterior correction and fusion be done as a staged procedure. The authors have not found preoperative or interval traction to be necessary. The result must be good coronal and sagittal balance rather than the amount of curve correction per se.⁵⁸ Cosmesis is less of a problem, and the need for consideration of thoracoplasty for the rib hump is rare. Other treatment options include additional PLIF/ALIF for lumbar segments in the form of carbon or metal cages, bone blocks, and femoral allografts, which may be necessary to obtain fusion to the sacrum in certain higher-risk patients, such as smokers.

ADOLESCENT IDIOPATHIC
SCOLIOSIS
With the efficacy of school screening, many curves of scloliosis are now picked up early, although the difficulty is still selecting those who eventually require surgery. Cosmesis is also an important issue for the patient and parents.

Treatment . Most of these curves are treated nonoperatively with either observation or bracing, depending on the magnitude of the curve and the bone age of the patient. For a thoracolumbar curve (loosely King III and IV types), the authors recommend anterior fusion, segmental instrumentation with correction, rib graft, and TLSO. For thoracic, double major, and other complex curves (inclusive of King I, II, and V types), the authors prefer posterolateral fusion, segmental instrumentation with correction, iliac crest graft, and TLSO. The principle of what levels to fuse' and the principles of fusion remain the same, although instrumentation issues ^{7, 9, 37, 53} and systems continue to be modified. Circumferential fusions are not usually necessary to attain fusion or maintain correction; however, in the preadolescent age group with large growth potential, anterior fusion in addition to posterior fusion may be necessary to avoid the crankshaft phenomenon. This may be the best indication for anterior thoracoscopic surgery.^{10, 46, 52} The result must be good coronal and sagittal balance rather than curve correction per se in regard to adjacent segment breakdown⁵⁴ and later back pain.¹⁵ The option of concurrent thoracoplasty to improve the rib hump must be discussed, and this has been shown to be effective with the advantage of being able to use the resected ribs as graft. ²² Other treatment options include anterior fusion and instrumentation or thoracic and some double major curves and additional PLIF/ALIF for lumbar segments in the form of carbon or metal cages, blocks, and femoral allografts.

PARALYTIC AND NEUROMUSCULAR SCOLIOSIS
A nonwalking adult with cerebralpalsy may present with decompensation in the position or nursing difficulties. Some of these patients may require surgical management. More severely affected adult cerebral palsy patients can have fairly long life spans, and the incidence of spinal deformity is high.

Treatment . The authors recommend posterolateral fusion of the entire curved spin segmental instrumentation, iliac crest graft (sometimes supplemented with allograft), and TSLO brace postoperatively. First-stage anterior release and rib grafting may be necessary in stiff curves or in children with significant growth remaining. There is increasing opinion that if the patient can walk it is preferable not to fuse to the sacrum. Even in nonwalkers, it may not be necessary to fuse to the sacrum if no growth remains⁶² or if surgery is performed before the curve becomes too severe.⁴⁵ Preoperative or interval traction is not well tolerated. In patients with cerebral palsy and sometimes spina bifida, the state of the hips must also be considered, especially with pelvic obliquity. There is probably no correct answer as to which should be addressed first: the spine or the hips. In patients with spina bifida, instrumentation techniques for attaining fusion to the sacropelvic complex are necessary, and the authors use the Galveston technique. The authors prefer to use a mixture of iliac autograft and allograft; however, others have had good experience with use of allograft alone.⁷² It may sometimes be necessary to perform an anterior lumbar release for correction or as an aid to fusion in some cases, ²⁹ and some suggest a combined approach as a routine.⁶¹ In patients with spinal muscular atrophy, the Luque technique remains a successful one, with patients being happy with cosmesis despite no other overall gain in the short or long term. ²⁷ In patients with Recklinghausen's disease, anterior and posterior procedures are required to attain an adequate fusion. Other treatment options include anterior instrumentation and various other methods of lumbosacral fixation.

SPURIOUS SCOLIOSIS
Especially in children, tumors may present as a painful scoliosis. Osteoid osteoma is probably the best known for this. Arnold-Chiari malformations and syrinxes may also be associated with scoliosis among other things in children. In adolescents and adults, a herniated nucleus pulposus may produce a painful list, and in all age groups, scoliosis can be secondary to syringomyelia.

Treatment. For treatment of tumors, the site of the tumor dictates the approach. Fusion with or without instrumentation is mandatory if decompressive destabilizing surgery is needed (Fig. 6). Neurosurgical assessment is necessary for patients found to have cord or brain pathology. The treatment of herniated nucleus pulposus that is producing a sciatic list and nonstructural scoliosis is well established. First-time surgical candidates are treated with a standard discectomy.

Figure 6. A and B, A 29-year-old man presenting with lower back pain and sciatic list (AP and oblique radiograph). Note missing pedicle at L2. C and D, MR images (sagittal and axial) of same patient.

CONGENITAL SCOLIOSIS AND KYPHOSIS
The most common presentation of congenital deformity is an incidental finding on investigation of other pathologies, such as abdominal pain. Many of these are and remain balanced, requiring prudent observation, especially through the growth spurt. Congenital kyphoses, however, tend to be obvious clinically quite early. Kyphoses associated with syndromes or inborn errors of metabolism tend to present in later childhood.

Treatment . A detailed discussion of congenital deformities is beyond the scope of this article, but the age of the patient, remaining growth, type of anomaly, and associated anomalies, including the spinal cord, need to be taken into account. In children who require fusion to prevent progression, a posterior fusion without instrumentation is usually adequate and, if done early enough, allows some correction with growth. In any corrective procedure, anterior and posterior procedures with an instrumented fusion is generally needed. The surgical treatment of congenital kyphosis has the highest neurologic risk. Distraction of the cord must be avoided, and shortening is safer, although still risky.⁴⁹ Autologous graft is undoubtedly the best choice, and although the author prefer iliac crest, others have used rib, tibia, fibula, and skull. In young children with a pure scoliotic deformity, with growth remaining, an anterior hemiepiphysiodesis and hemiarthrodesis may be needed in addition to a posterior procedure, which may be done in a transpedicular fashion.³⁴ Some believe that instrumentation is also necessary to halt progression.⁴¹
Figure 6 (Continued). E, CT scans of L2 vertebral body and pedicle. F and G, Postoperative radiographs (AP and lateral). Patient treated with combined anterior and posterior approaches and reconstruction with femoral allograft and pedicle screw-rod stabilization. Diagnosis of neurosarcoma made on preoperative needle biopsy and postoperative tissue analysis.

CONGENITAL SPONDYLOLISTHESIS AND SPONDYLOPTOSIS
The treatment of high-grade slips and spondyloptosis remains difficult and fraught with complications. Cosmesis is also an important issue for the patient and parents.

Treatment. The authors prefer posterior reduction (as possible), PLIF, posterolateral fusion with segmental instrumentation, and iliac crest graft. Correction of the kyphotic component is probably the most importment feature in regard to long-term results. Reduction of the slip may be nil, partial, or total, but some suggest this actually makes no difference to the final result in regard to residual pain. ⁵¹ The approach is controversial with support for all approaches-anterior then posterior,⁶⁵ posterior then anterior,⁴⁷ anterior alone,⁶⁶ or posterior alone, ³¹ all of varied techniques. Instrumentation probably improves the fusion rate but not necessarily the clinical result.¹³ It is probably more important that something is put into the disc space.¹⁷ Other treatment options include posterior in situ fusion, posterior segmental instrumentation with reduction of the kyphotic component with partial or full reduction of the slip or with PLIF,¹⁷ in the form of bone or metal cages. Other treatments include sequential anterior fusion, prior anterior release, and anterior approach alone.

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Address repririt requests to
Edward D. Simmons, MD Associate Clinical Professor State University of New York at Buffalo 235 North Street Buffalo, NY 14201

From The Royal Children's Hospital, Parkville, Victoria, Australia (SML); and Department of Orthopaedic Surgery, State Universitv of New York at Buffalo, Buffalo, New York (EDS)