Relaxation of forces needed to distract cervical vertebrae after discectomy: a biomechanical study.

STUDY DESIGN: In vitro and in vivo biomechanical stress measurements are made of the intervertebral disc segment distraction force during anterior cervical discectomy. OBJECTIVE: The purpose of this study is to determine the short-term force relaxation of the native intervertebral disc segment and to determine the short-term force relaxation of the segment after removal of the intervertebral disc, as is commonly performed in anterior cervical discectomy with fusion and arthroplasty. SUMMARY OF BACKGROUND DATA: No published data examine the issue of intraoperative distraction force of the cervical intervertebral disc segment. This is a novel research in this area. METHODS: In vitro and in vivo studies under institutional review board approval were performed to determine the mechanical behavior of the normal and diseased cervical functional spinal unit. Seven in vitro and 11 in vivo spines were studied. Strain measurements between distracting Caspar-type pins were made before, at various points during, and after discectomy to assess how removal of the disc and other spinal components affects the force-displacement behavior of the spinal unit. RESULTS: The in vitro data show progressive reduction in force needed for distraction after discectomy and uncovertebral joint resection. Greatest reduction is noted after discectomy. The in vivo data indicate that, on average, the cervical functional spinal unit requires 20 N less force to achieve the same degree of distraction after removal of the intervertebral disc. CONCLUSIONS: A sharp reduction in the strain across the intervertebral space occurs after distraction. The removal of the cervical intervertebral disc significantly reduces the viscoelastic response of the cervical motion segment. The long-term force used to stabilize intervertebral grafts or implants is less than what is achieved at the time of distraction. The exact magnitude of the resultant force on graft or device at a given distraction force is unknown and would depend also upon fit.

The short-term effects of electrosurgical ablation on proinflammatory mediator production by intervertebral disc cells in tissue culture.

BACKGROUND CONTEXT: Percutaneous discectomy can be performed by a variety of methods. One method, electrosurgical ablation, has been shown in a chronic animal model to alter the expression of inflammatory cytokines in degenerated discs. PURPOSE: To determine whether electrosurgical ablation has an acute direct effect on proinflammatory mediator production by disc cells. STUDY DESIGN: A short-term in vitro study using normal and interleukin (IL)-1alpha stimulated porcine disc cells cultured in alginate gel to evaluate the biochemical effects of electrosurgical ablation. METHODS: Porcine annulus and nucleus cells were embedded into alginate gels and cultured using control culture media or IL-1alpha-treated media for 6 days before ablation treatment. Treated gels were ablated by using a radiofrequency-based electrosurgical device for 5 seconds and cultured an additional 3 or 6 days. IL-1beta, IL-6, IL-8, tumor necrosis factor alpha (TNF-alpha), prostaglandin E2 (PGE2), nitric oxide (NO), and heat shock protein-70 (Hsp70) levels in culture medium were measured. Levels were normalized to DNA and compared between ablated and shams. RESULTS: For normal annulus cells, there were no significant changes in cytokine levels between ablation and sham groups. For normal nucleus cells, ablation produced significantly greater levels of IL-8 at 3 days and 6 days, Hsp70 at 3 days but not 6 days, and NO at 6 days. PGE2 was also increased at 3 days and 6 days but not significantly. For IL-1-stimulated annulus cells, IL-6 and NO in the ablation group were decreased at 3 days relative to the control group. However, IL-6, IL-8, PGE2, and Hsp70 were significantly increased in the 6-day ablation group. For degenerated nucleus cells, IL-6, IL-8, and TNF-alpha were significantly decreased in the ablation group at both 3 days and 6 days. Ablation resulted in reduced PGE2 at 3 days but not 6 and reduced Hsp70 and NO at 6 days. CONCLUSIONS: The results show that electrosurgical ablation has an acute direct effect on proinflammatory mediator production by disc cells. The effect produced depends on disc cell phenotype, the mediator, and time. These direct biologic effects may be a mechanism of pain relief after percutaneous discectomy using electrosurgical ablation. However, the measured responses are limited to the short-term (1 week), and the existence of a prolonged effect remains to be determined.

Disc arthroplasty design influences intervertebral kinematics and facet forces.

BACKGROUND CONTEXT: Total disc replacement is a novel approach for dynamically stabilizing a painful intervertebral segment. While this approach is gaining popularity, and several types of implants are used, the effect of disc arthroplasty on lumbar biomechanics has not been widely reported. Consequently, beneficial or adverse effects of this procedure may not be fully realized, and data for kinematic optimization are unavailable. PURPOSE: To characterize kinematic and load transfer modifications at L5/S1 secondary to joint replacement. STUDY DESIGN: A human cadaveric biomechanical study in which the facet forces and instant axes of rotation (IAR) were measured for different spinal positions under simulated weightbearing conditions before and after total disc replacement at L5/S1 using semiconstrained (3 degrees of freedom [DOF]; Prodisc) and unconstrained (5 DOF; Charité) articulated implants. METHODS: Twelve radiographically normal human cadaveric L5/S1 joints (age range 45-64 years) were tested before and after disc replacement using Prodisc II implants (Spine Solutions, Paoli, PA) in six specimens and SB Charité III (Johnson & Johnson, New Brunswick, NJ) in six other specimens. Semiconstrained fixtures in combination with a servo-hydraulic materials testing system subjected the test specimens to a physiologic combination of compression and anterior shear. Multiple intervertebral positions were studied and included up to 6 degrees of flexion, extension, and lateral bending. The IAR was calculated for every 3-degree intervals, and the force through the facet joints was simultaneously measured using flexible intra-articular sensors. Data were analyzed using repeated-measures analysis of variance. RESULTS: During flexion/extension, the average IAR positions and directions were not significantly modified by implantation with the exception that the IAR was higher relative to S1 end plate with the Charité (p=.028). The IAR had a vertically oriented centrode throughout flexion/extension with the Prodisc (p<.001) and the Charité (p<.016). The centrode tended to be greater with the Prodisc. There was a trend that the facet force was decreased throughout flexion/extension for the Prodisc; however, this was statistically significant only at 6 degrees extension (27%, p=.013). In lateral bending, the IAR was significantly modified by Prodisc replacement, with a decreased inclination relative to S1 end plate, (ie, increased coupled axial rotation). While the IAR moved in the horizontal plane toward the side of bending, this effect was more pronounced with the Prodisc. The ipsilateral facet force was significantly increased in 6 degrees lateral bending with the Charité (85%; p=.001). CONCLUSIONS: The degree of constraint affects post-implantation kinematics and load transfer. With the Prodisc (3 DOF), the facets were partially unloaded, though the IAR did not match the fixed geometrical center of the UHMWPE. The latter observation suggests joint surface incongruence is developed during movement. With the Charité (5 DOF), the IAR was less variable, yet the facet forces tended to increase, particularly during lateral bending. These results highlight the important role the facets play in guiding movement, and that implant constraint influences facet/implant synergy. The long-term consequences of the differing kinematics on clinically important outcomes such as wear and facet arthritis have yet to be determined.

Stability analysis of craniovertebral junction fixation techniques.

BACKGROUND: Craniovertebral arthrodesis in the upper cervical spine is challenging because of the high degree of mobility afforded by this region. A novel method for achieving atlantoaxial fixation with use of polyaxial screws inserted bilaterally into the lateral masses of C1 and transpedicularly into C2 with longitudinal rod connection has recently been introduced. The question remains as to whether this technique provides adequate stability when extended cephalad to include the occiput. The purpose of this study was to determine the primary stability afforded by this novel construct and compare its stability with the current standard of bilateral longitudinal plates combined with C1-C2 transarticular screws. METHODS: We used ten fresh-frozen human cadaveric cervical spines (C0-C4). Pure moment loads were applied to the occiput, and C4 was constrained during the testing protocol. We evaluated four conditions: (1) intact, (2) destabilized by means of complete odontoidectomy, (3) stabilization with longitudinal plates with C1-C2 transarticular screw fixation, and (4) stabilization with a posterior rod system with C1 lateral mass screws and C2 pedicle screws. Rigid-body three-dimensional rotations were detected by stereophotogrammetry by means of a three-camera system with use of marker triads. The range of motion data (C0-C2) for each fixation scenario was calculated, and a statistical analysis was performed. RESULTS: Destabilization of the specimen significantly increased C0-C2 motion in both flexion-extension and lateral bending (p < 0.05). Both fixation constructs significantly reduced motion in the destabilized spine by over 90% for all motions tested (p < 0.05). No significant differences were detected between the two constructs in any of the three rotational planes. CONCLUSIONS: Both hardware systems provide equivalent construct stability in the immediate postoperative period when it is critical for the eventual success of a craniovertebral arthrodesis. On the basis of this work, we believe that the decision to use either construct should be determined by clinical rather than biomechanical concerns.

Orthopaedic Trends in the 1990s An introduction.

Recent advances in orthopaedic technology have been among the most exciting medical developments of the past decade. More than 90 percent of the procedures and implants in use today did not exist a decade ago. The development of new prostheses and implants, the modifications of existing ones, and the development of new surgical techniques have allowed orthopaedic surgeons to treat and rehabilitate patients with diseases and deformities that were previously unmanageable. Furthermore, the newer and less invasive procedures have decreased the cost of treatment and recovery time for many patients. Prosthetic joint replacement is now capable of relieving arthritic pain in a predictable fashion, and spinal deformities of any magnitude can be treated in patients of any age with a high probability of success. The reattachment of amputated parts has become commonplace, and techniques of tissue transfer have enabled the salvage and reconstruction of cancerous or traumatised limbs that previously would have been lost to amputation.

Advances in Spine Surgery.

Technological advances in the field of spine surgery have most often involved instrumentation. In recent years, a great deal of attention has been focused on variable hookscrew-rod systems, the prototype of which is the Cotrel-Dubousset instrumentation (CDI). This French-designed system and similar ones such as the Texas-Scottish Rite (TSRH), or the Isola, provide significantly better fixation and rigidity than has ever been possible, and they allow many patients to be spared the discomfort and inconvenience of post-operative brace or cast support. These features are particularly important for older and chronically ill patients, whose often difficult problems can also be addressed more safely and effectively with this new technology.

Thoracolumbar spinal deformity: Part I. A historical passage to 1990: historical vignette.

Seven millennia of anthropological artifacts and historical tales reference human spinal deformity, its diagnosis, and treatment-many of the latter of which turned out to be worse than the deformity itself. From Hippocrates to Harrington to the 21st century, the literature base has expanded in exponential fashion to yield an imperfect but constantly improving body of evidence, experience, and understanding of this challenging disease phenomenon. This review details the pre-1990 innovations, whose failures and successes have equally contributed to the advancement and dissemination of the increasingly evidence-based field of spinal deformity.

Reoperation after primary fusion for adult spinal deformity: rate, reason, and timing.

STUDY DESIGN: Retrospective cohort study of consecutive patients undergoing primary fusion with segmental fixation for adult spinal deformity. OBJECTIVE: We sought to determine the survivorship of primary fusion for adult spinal deformity and identify patient-specific predictors of complications requiring reoperation. SUMMARY OF BACKGROUND DATA: Compared with the adolescent population, surgery for adult deformity is often more complex and technically difficult, contributing to a high reported rate of complications that can result in the need for reoperation. Reported complication rates vary widely. METHODS: From 1999-2004 all patients who underwent primary instrumented fusion for nonparalytic adult spinal deformity at a single center were included. Inclusion criteria included minimum age at surgery of 20 years and minimum fusion length of 4 motion segments. Surgical, demographic, and comorbidity data were recorded. Reoperation was defined as any additional surgery involving levels of the spine operated on during the index procedure and/or adjacent levels. Comparisons were performed between patients who required reoperation and those who did not. RESULTS: Eighty-nine patients met inclusion criteria. Endpoint (minimum 2 years follow-up or reoperation) was reached for 91%. Mean follow-up was 3.8 years. Cumulative reoperation rate was 25.8%. Survival was 86.4% at 1 year, 77.2% at 2 years, and 75.2% at 3 years. Reasons for reoperation included infection (n = 8), pseudarthrosis (n = 3), adjacent segment problems (n = 5), implant failure (n = 4), and removal of painful implants (n = 3). Multivariate analysis showed smoking was significantly higher in the reoperation group. CONCLUSION: Using a strict definition of reoperation for a well-defined cohort, in the presence of relevant risk factors, many patients undergoing primary fusion for adult spinal deformity required reoperation. The results indicate that complex medical and surgical factors contribute to the treatment challenges posed by patients with adult spinal deformity. This represents the largest cohort reported to date of patients undergoing primary fusion using third-generation instrumentation techniques.

Clinical outcome of deep wound infection after instrumented posterior spinal fusion: a matched cohort analysis.

STUDY DESIGN: Retrospective case control study. OBJECTIVE: Determine the impact of infection on clinical outcome in patients undergoing posterior spinal fusion surgery. SUMMARY OF BACKGROUND DATA: The outcome of patients treated for infection after spinal surgery is not well established because of variability in cohort identification, definition of infection, outcomes instrument, use of a control group, and/or sample size. METHODS: Thirty-two patients were included. Sixteen patients ("infection group") met inclusion criteria of deep wound infection after spinal fusion with posterior segmental instrumentation (including combined approach). A 1:1 matched cohort ("control group") was created based on primary or revision status, length of fusion, diagnosis, and age. Postoperative patient outcomes were evaluated using the physical components of SF-36 v2.0 with minimum 2-year follow-up. RESULTS: No significant difference in the Physical Function, Role Physical, Bodily Pain, and General Health domains was detected between the infection group and control group. Mean follow-up was 62 months. Mean Physical Component Summary was 41.4 in the infection group and 44.3 in the control group (P = 0.6). Infection occurred early in 12 patients and late in 4 patients. Most common organisms isolated were Staphylococcus epidermidis, Enterococcus sp., and Staphylococcus aureus. Multiple debridements were significantly associated with polymicrobial infections and later pseudarthrosis requiring reoperation. CONCLUSION: An aggressive approach to deep wound infection emphasizing early irrigation and debridement allowed preservation of instrumentation and successful fusion in most cases. At the conclusion of treatment, patients can expect a medium-term clinical outcome similar to patients in whom this complication did not occur.

Anterior arthrodesis with instrumentation for thoracolumbar scoliosis: comparison of efficacy in adults and adolescents.

STUDY DESIGN: A retrospective review was performed of adult and adolescent patients who underwent anterior spinal fusion for thoracolumbar idiopathic scoliosis; radiographic and clinical outcomes were compared. OBJECTIVE: The objective of this study was to compare the efficacy of anterior instrumentation to treat thoracolumbar scoliosis in adults and adolescents by evaluating radiographic and clinical outcomes. SUMMARY OF BACKGROUND DATA: Anterior spinal arthrodesis is an effective treatment for idiopathic scoliosis. Deformity characteristics and clinical outcomes of adults versus adolescents have not been compared. METHODS: A retrospective review of patients undergoing anterior fusion for thoracolumbar scoliosis was performed. Clinical outcomes were assessed using SRS-22. Preoperative and postoperative long films were evaluated independently. Flexibility, curve correction, and clinical outcomes were compared between adult and adolescents. RESULTS: Fifteen adults and 15 adolescents who underwent anterior spinal fusion and instrumentation were evaluated. Mean follow-up was 47 and 46 months, respectively. Flexibility of the major curve in adults (63%) was less than in adolescents (79%) (P < 0.05). Mean preoperative, major curve Cobb angles were 51 degrees and 49 degrees for adults and adolescents, respectively. Mean postoperative Cobb angles improved less for adults (17 degrees ) than for adolescents (10 degrees ) (P < 0.05). The SRS-22 questionnaire revealed no statistical difference between populations. CONCLUSION: Anterior spinal fusion is an option for both adults and adolescents with flexible, moderate thoracolumbar/lumbar curves. Flexibility significantly decreased with increased age and curve magnitude. This significantly affected curve correction. Adult patients may develop early degeneration at primary curve and compensatory curves. Careful patient selection is critical with this technique.

The selection of L5 versus S1 in long fusions for adult idiopathic scoliosis.

The treatment of adult spinal deformities often involves long thoracolumbar fusions into the lower lumbar spine, raising the debate of selecting L5 or S1 as the caudal extent of the fusion. The presence of significant deformity or degenerative pathologic findings at L5-S1 mandates fusion to the sacrum. Fusion to the sacrum is of larger magnitude than fusion to L5 and introduces a higher surgical complication rate. Advantages of ending the fusion at L5 include preservation of motion, avoiding the high complication rate associated with fusion to the sacrum, and possibly avoiding a second operation. Complications with fusion to L5 include possible loss of fixation and subsequent disc degeneration at L5-S1, however, leading to possible pain and loss of sagittal balance and the need for revision surgery. To date, the functional consequences of an open disc space beneath long constructs remain poorly defined, and there is no firm evidence in the literature guiding the surgeon's choice. The issues and evidence guiding the decision to fuse to L5 or S1 are examined in this article.

Pay-for-performance: considerations in application to the management of spinal disorders.

STUDY DESIGN: Descriptive review. OBJECTIVES: To describe the role of pay-for-performance as a health care policy that has a significant influence on the management of spinal disorders, and to consider parameters of quality measure that are likely to optimize the efficacy of a pay-for-performance system as applied to spine care. SUMMARY OF BACKGROUND DATA: Pay-for-performance arrangements have been adopted in many areas of medicine with limited evidence for improvement in quality of care. There is an important role for a system that will improve quality of care in the management of spinal disorders. The absence of accepted evidence-based approaches to the management of spinal disorders makes the choice of parameters to measure for quality difficult. RESULTS: Performance parameters to consider include a continuum of measures from process variables that focus on a discrete component of the health care experience, to outcome variables that encompass the end result of care. There are advantages and limitations to each parameter discussed. CONCLUSION: A pay-for-performance system in the management of spinal disorders should include both process variables that measure safety and outcome variables that reflect the end result of care.

Pay for performance in orthopaedic surgery.

In recent decades American medicine has undergone tremendous changes. Numerous reimbursement and systems approaches to controlling medical inflation and improving quality have failed to provide cost-effective, high-quality health care in most circumstances. Public and private payers are currently implementing pay for performance, a new reimbursement method linking physician pay to evidence of adherence to performance measures, to constrain costs, encourage efficiency, and maximize value for health care dollars. High-quality research regarding pay for performance and its impact is scarce, particularly in orthopaedic surgery. Although supporters argue pay for performance will remedy the fragmented, costly delivery of health services in the United States, skeptics raise concerns about disagreement over quality guidelines, financial implications for providers and hospitals, inadequate infrastructure, public reporting, system gaming, and physician support. Our survey of orthopaedic surgeons reveals limited understanding of pay for performance, marked skepticism of nonphysician stakeholders' intentions, and a strong desire for greater clinician involvement in shaping the pay for performance movement. As pay for performance will likely be a long-term change that will have an impact on every orthopaedic surgeon, clinician awareness and participation will be fundamental in creating successful pay for performance programs.

Operative management of degenerative scoliosis: an evidence-based approach to surgical strategies based on clinical and radiographic outcomes.

Degenerative scoliosis is a common and important cause of lumbar spine deformity in the adult. The operative management of degenerative scoliosis encompasses a spectrum of approaches, including decompression alone, or fusion that may include posterior or anterior approaches. There exists significant variability in surgical approaches to degenerative scoliosis, and evidence to support a specific approach is limited. Including the structural thoracic spine in fusions to the thoracolumbar junction has a lower rate of revision than fusions with a cephalad segment at T12 or L1. Short fusions to L5 have a low rate of revision at a minimum follow-up of 2 years. Combined anterior and posterior surgery is more effective in improving lordosis than posterior-only surgery without osteotomies. Clinical outcomes of surgery for degenerative scoliosis are variable, andwct 2 self-reported scores for pain improve more reliably than scores for function. Further investigation, including comparison of randomized or matched cohorts and measurement of outcomes related to specific preoperative complaints, will be useful in the development of an evidence-based approach to degenerative scoliosis.

The instant axis of rotation influences facet forces at L5/S1 during flexion/extension and lateral bending.

Because the disc and facets work together to constrain spinal kinematics, changes in the instant axis of rotation associated with disc degeneration or disc replacement may adversely influence risk for facet overloading and arthritis. The relationships between L5/S1 segmental kinematics and facet forces are not well defined, since previous studies have separated investigations of spinal motion and facet force. The goal of this cadaveric biomechanical study was to report and correlate a measure of intervertebral kinematics (the centrode, or the path of the instant axis of rotation) and the facet forces at the L5/S1 motion segment while under a physiologic combination of compression and anterior shear loading. Twelve fresh-frozen human cadaveric L5/S1 joints (age range 50-64 years) were tested biomechanically under semi-constrained conditions by applying compression plus shear forces in several postures: neutral, and 3 degrees and 6 degrees of flexion, extension and lateral bending. The experimental boundary conditions imposed compression and shear representative of in vivo conditions during upright stance. The 3-D instantaneous axis of rotation (IAR) was calculated between two consecutive postures. The facet joint force was simultaneously measured using thin-film sensors placed between both facet surfaces. Variations of IAR location and facet force during motion were analyzed. During flexion and extension, the IAR was oriented laterally. The IAR intersection with the mid-sagittal plane moved cephalad relative to S1 endplate during flexion (P=0.010), and posterior during extension (P=0.001). The facet force did not correlate with posture (P=0.844). However, changes in the facet force between postures did correlate with IAR position: higher IAR's during flexion correlated with lower facet forces and vice versa (P=0.04). During lateral bending, the IAR was oblique relative to the main plane of motion and translated parallel to S1 endplate, toward the side of the bending. Overall, the facet force was increased on the ipsilateral side of bending (P=0.002). The IAR positions demonstrate that the L5 vertebral body primarily rotates forward during flexion (IAR close to vertebral body center) and rotates/translates backward during extension (IAR at or below the L5/S1 intervertebral disc). In lateral bending, the IAR obliquity demonstrated coupling with axial torsion due to resistance of the ipsilateral facet.

Risk factors for infection after spinal surgery.

STUDY DESIGN: A retrospective case control analysis of 48 cases of postoperative infection following spinal procedures. OBJECTIVES: Spinal procedures that became infected after surgery were analyzed to identify the significance of preoperative and intraoperative risk factors. Characterization of the nature and timing of the infections was also performed. SUMMARY OF BACKGROUND DATA: The rate of postoperative infection following spinal surgery varies widely depending on the nature of the procedure and the patient's diagnosis. Preoperative comorbidities and risk factors also influence the likelihood of infection. METHODS: A review of 1629 procedures performed on 1095 patients revealed that a postoperative infection developed in 48 patients (4.4%). Data regarding preoperative and intraoperative risk factors were gathered from patient charts for these and a randomly selected control group of 95 uninfected patients. For analysis, these patient groups were further divided into adult and pediatric subgroups, with an age cutoff of 18 years. Preoperative risk factors reviewed included smoking, diabetes, previous surgery, previous infection, steroid use, body mass index, and alcohol abuse. Intraoperative factors reviewed included staging of procedures, estimated blood loss, operating time, and use of allograft or instrumentation. RESULTS: The majority of infections occurred during the early postoperative period (less than 3 months). Age >60 years, smoking, diabetes, previous surgical infection, increased body mass index, and alcohol abuse were statistically significant preoperative risk factors. The most likely procedure to be complicated by an infection was a combined anterior/posterior spinal fusion performed in a staged manner under separate anesthesia. Infections were primarily monomicrobial, although 5 patients had more than 4 organisms identified. The most common organism cultured from the wounds was Staphylococcus aureus. All patients were treated with surgical irrigation and débridement, and appropriate antibiotics to treat the cultured organism. CONCLUSIONS: Aggressive treatment of patients undergoing complex or prolonged spinal procedures is essential to prevent and treat infections. Understanding a patient's preoperative risk factors may help the physician to optimize a patient's preoperative condition. Additionally, awareness of critical intraoperative parameters will help to optimize surgical treatment. It may be appropriate to increase the duration of prophylactic antibiotics or implement other measures to decrease the incidence of infection for high risk patients.

Neuromuscular scoliosis: causes of deformity and principles for evaluation and management.

Scoliosis is commonly associated with a variety of neuromuscular disorders including conditions affecting upper and lower motor neurons as well as myopathies. Contained herein is a discussion of the spectrum of neuromuscular disorders that have been associated with scoliosis and related spinal deformities. Management, including surgical treatment in such patients, is summarized including indications, expectations, and impact on trunk balance, pulmonary function, and appearance.

Athletic activity after spine surgery in children and adolescents: results of a survey.

STUDY DESIGN: Questionnaire-based survey. OBJECTIVES: To poll the members of the Scoliosis Research Society regarding their opinions and experience with athletic activity after spine surgery performed on children and adolescents. SUMMARY OF BACKGROUND DATA: Athletic activity is increasingly important in society. Patients are very concerned about returning to sports and exercise after spinal surgery. There are no generally accepted guidelines for surgeons regarding either appropriate sports or the appropriate time to resume sports after spinal surgery. METHODS: A survey was designed by the authors and reviewed by a statistical consultant. The form was mailed to the 721 individuals on the Scoliosis Research Society mailing list. Returned surveys were hand scored and entered into an Excel spreadsheet. RESULTS: Of the 316 forms returned, 278 indicated that the respondent performed spinal fusion on children and adolescents. Two hundred sixty-one completed forms, representing approximately 45% of the society's estimated active clinicians, were reviewed. Formal physical therapy was unlikely to be recommended by members of the society regardless of procedure, although postoperative home exercise was used by many after spondylolisthesis fusion. The majority of patients were returned to gym class between 6 months and 1 year (range, immediate to never) after surgery. Most respondents returned patients to noncontact sports between 6 months and 1 year postoperatively. Contact sports were generally withheld until 1 year after surgery. Close to 20% of respondents required, and 35% suggested, that patients never return to collision sports. Twenty percent of respondents for scoliosis and 5% for spondylolisthesis reported having notable adverse outcomes attributed to athletic activity. CONCLUSION: These survey results show the varying approaches taken by members of the Scoliosis Research Society to postoperative athletic activity, and they provide a starting point for investigations regarding alternative approaches.

Use of allograft femoral rings for spinal deformity in adults.

Anterior structural support plays an important role in spinal deformity surgery. Femoral ring allografts have been widely used for this purpose despite numerous alternative implants such as cages. The literature and the authors' experience support the use of femoral ring allograft as a structural and biologic compatible implant to reconstruct anterior column defects. Pseudarthrosis rates and the rate of subsidence and loss of correction are low. No long-term studies exist that show that cages are superior in correction of deformity. Femoral ring allograft remains a viable, cost-effective, and biologic sound alternative.

In vivo growth factor treatment of degenerated intervertebral discs.

STUDY DESIGN: An in vivo model was used to investigate the response of degenerated discs to various exogenous growth factors. OBJECTIVES: To study growth factor-induced alterations of the spatial and temporal patterns of disc cellularity and matrix gene expression. SUMMARY OF BACKGROUND DATA: Cell proliferation and proteoglycan synthesis have been stimulated by growth factors in normal disc cells, suggesting that growth factors may play a therapeutic role for degeneration. However, the response in situ in degenerated discs has not been characterized. METHODS: Degeneration was induced in murine caudal discs by static compression. Degenerated discs were given single or multiple injections of growth and differentiation factor-5, transforming growth factor-beta, insulin-like growth factor-1, basic fibroblast growth factor, or saline as control. Comparisons of disc morphology, anular cell density, proliferating cells, disc height, and aggrecan and type II collagen gene expression were made either 1 week or 4 weeks after treatment. RESULTS: In some growth and differentiation factor-5 and transforming growth factor-beta treated discs, expansion of inner anular fibrochondrocyte populations into the nucleus was observed. The cells actively expressed aggrecan and type II collagen mRNA. A lesser effect was observed for insulin-like growth factor-1 and little or no effect for basic fibroblast growth factor. Differences in cell density and proliferating cells were not significant between treatments but suggested a trend of increased cellularity and proliferation following growth factor treatment. A statistically significant increase in disc height 4 weeks after growth and differentiation factor-5 treatment was measured. CONCLUSIONS: Anular fibrochondrocytes in degenerated discs are responsive to some growth factors in vivo. The results have implications in the early intervention of disc degeneration to arrest or slow the degenerative process.