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Study Design: A cross-sectional study on 18,325 patients with back pain enrolled at first visit in the National Spine Network (NSN) database from January 1998 to April 2000., Objectives: To examine whether patients who had previous low back surgeries had poorer general health status than patients with no surgery., Summary of Background Data: Several studies have described the role of psychological abnormalities in patients with chronic low back pain. Some of these patients have had previous spinal surgeries performed. No study has examined the effects of previous low back surgery on the general health status., Methods: The Short Form Health Survey 36 was administered to the initial visit NSN patients. Of the 18,325 patients enrolled, 3,632 had previous low back surgeries., Results: Patients who had previous lumbar surgeries fared significantly poorly in all 10 scores of the SF-36 health survey, even after adjustment for confounding factors. Among these patients, decompression achieved significantly higher scores for General Health, Role-Physical, and Mental Component Summary scales. Patients who had decompression as their most recent surgery had higher scores for General Health, Role-Physical, Role-Emotional, and Mental Component Summary scales, when compared to those who had other surgeries. Patients who had instrumentation as their most recent surgery had higher scores for Bodily Pain and Physical Component Summary scores. There is a positive correlation between time since last surgery and the SF-36 outcomes., Conclusions: Previous back surgery is associated with significantly worse general health status than those without surgery. Among patients who had previous surgeries, decompression seems to exert better effects on SF-36 health status. There is a positive correlation between time since last surgery and the SF-36 outcomes, although the SF-36 scores are significantly lower than those without previous surgery.

Reliable ingrowth of bone into porous-coated cementless total hip components can be expected in primary surgery. In the revision scenario, however, bone deficiency frequently is encountered and the remaining bone may have less ingrowth potential. Allograft bone and bone graft substitutes may be successful in healing bone defects, but have virtually no capacity to induce bone growth from the defect into the porous surface. To evaluate the role osteoinductive bone proteins may play in enhancing bone ingrowth, six canines had bilateral total hip arthroplasties with a cementless press-fit porous-coated acetabular component. A defect 8 mm in diameter and 5 mm in depth was created in the superior weightbearing area of each acetabulum. One defect in each animal was filled with recombinant human osteogenic protein-1. Each contralateral defect was filled with allograft bone, left empty (defect healing control), or no defect was created (intact) to serve as a control for ideal conditions for bone ingrowth. The osteogenic protein-treated defects healed more completely than allograft bone-treated or empty defects and achieved a bone density equivalent to the intact acetabulum. Bone ingrowth also occurred to a significantly higher degree in the osteogenic protein group compared with the allograft or empty defects achieving a degree of ingrowth equivalent to the intact acetabulum controls. The osteogenic bone protein was successful in achieving complete defect healing and inducing extensive ingrowth from the defect into the adjacent porous coating.

The ideal surgical treatment of multilevel cervical spondylosis remains unclear. This study analyzed the complications in using titanium cages and plating to reconstruct multilevel cervical corpectomies. This was a retrospective analysis of 21 consecutive patients who had multilevel cervical corpectomies and reconstruction with titanium cages and anterior plating. Sixteen had 2-level, one had 2.5-level, three had 3-level, and one had 3.5-level corpectomies. All had reconstruction with titanium cages and anterior plating. Thirty-three percent of the patients developed complications. Radiographs revealed bony consolidation in 95% of patients. Reconstructing multilevel cervical corpectomies with titanium cages and plating is associated with complications. Advantages include rigid immobilization and the avoidance of iliac crest bone graft harvesting. Major complications are largely the result of failures of the cage and plate construct, especially in patients with osteopenic bone. Supplemental posterior stabilization may be considered for cases with spasticity or greater than 2-level corpectomies with profound osteoporosis.

Poorer outcomes of treatment are reported in patients with spinal disorders who receive worker's compensation. The reason for their suboptimal outcomes is unclear. No study has examined the relationship between worker's compensation and SF-36 health status of patients with neck pain. The aim of our study was to compare the self-perceived health status of patients with neck pain receiving worker's compensation, with that of patients not receiving worker's compensation. A cross-sectional study was conducted on 2356 patients with neck pain who were evaluated at the 27 centers comprising the National Spine Network, between January 1998 and April 2000. The outcome measures used were the eight individual and two component scores of the SF-36 health survey. Of the 2356 patients, 171 (7%) were receiving worker's compensation. Bivariate analyses revealed seven individual scores (except General Health) and two summary scores of the SF-36 were significantly lower in patients receiving worker's compensation. After controlling for confounding covariates, worker's compensation status was a significant predictor of lower SF-36 scores for Physical Functioning ( P<0.05). The results of this study indicate that worker's compensation status is associated with poorer Physical Functioning in patients presenting with neck pain. Another significant finding of the study is that confounding factors can exert major effects on the SF-36 scores obtained on normal validated instruments.

Study Design: A case of cauda equina syndrome is reported., Objective: To recognize a serious complication related to the use of Gelfoam in the lumbar spine., Summary and Background Data: Absorbable hemostatic gelatin sponges have long been used to control bleeding around the spinal cord. Despite widespread use and a safe history with few reported adverse reactions, Gelfoam sponges have potential for complications that may be overlooked., Method: A case of cauda equina syndrome is reported and discussed., Results: A retained Gelfoam sponge was found in the epidural space after lumbar decompression and fusion for spinal stenosis. The retained gelatin sponge had expanded and solidified, causing a mass affect. The resultant nerve compression led to progressive myelopathy. On removal of the Gelfoam, symptoms rapidly resolved., Conclusions: Although the use of Gelfoam in spine surgery generally is considered safe, care must be taken to avoid placing a large mass of sponge in a potentially closed space. If Gelfoam is not handled properly, it can engorge and fail to be resorbed appropriately, thus causing a mass effect. If neurologic compromise develops, Gelfoam should be considered a potential cause and subsequently removed.

As with any joint venture in any given industry, positive and negative impacts are felt. Tulane University School of Medicine experienced impacts on its academic and clinical missions as a result of the joint venture between Tulane University and HCA, a for-profit public company. The laws of business had entered the halls of medicine. Although patients, personnel, and physicians experienced culture shock and inconveniences, Tulane University School of Medicine has been able to maintain viable training programs, and its faculty physicians have a hospital and corporately run clinics across the street. In addition, multidisciplinary centers of excellence, long spoken of in the academic realm, came to fruition through the corporate world. This may not have been the case, had Tulane University not entered into ajoint venture with HCA. Is it worth the effort? For Tulane University, whether one likes the entire package or not, the answer must be yes. The greatest impact is that the orthopaedic surgeons still are in a position to fulfill their academic and clinical missions.

Background Context: Poorer outcomes of treatment are reported in patients with spinal disorders who receive workers compensation. The reason for their suboptimal outcomes is unclear. No study has examined the relationship between workers compensation and the Short Form Health Survey (SF-36) health status of patients with spinal disorders., Purpose: To compare the self-perceived health status of spinal disorder patients receiving workers compensation with those not receiving workers compensation., Study Design/setting: A cross-sectional study on 18,389 patients who were evaluated in the 28 centers comprising the National Spine Network., Patient Sample: The study data were derived from patients when first evaluated for back or neck pain between January 1998 and April 2000., Outcome Measures: The outcome measures used were the eight individual and two component scores of the SF-36., Methods: All first-visit patients enrolled in the National Spine Network from January 1998 to April 2000 were reviewed. Eight individual scores and two component scores of the SF-36 were compared., Results: Of the 18,389 patients, 1,535 (8%) were receiving workers compensation. Bivariate analyses showed all eight individual scores, and two summary scores of the SF-36 were significantly lower (p<.0001) in patients receiving workers compensation. After controlling for confounding covariates, workers compensation status was a significant predictor of lower SF-36 scores for General Health (p<.0001), Physical Functioning (p<.0001), Role Physical (p<.01), Social Functioning (p<.05), and Mental Health (p<.05)., Conclusions: Workers compensation status is associated with poorer physical and mental health of patients with spinal disorders. Because the workers compensation group is younger, has a shorter duration of symptoms, and fewer comorbid medical problems, the lower SF-36 scores most likely reflect psychological factors and not ill health per se. The lower SF-36 scores may also reflect premorbid personality differences in the workers compensation patients, compared with those not receiving workers compensation. SF-36 is a validated tool that can be used to objectively identify the patient at risk for delayed recovery. Future treatment protocols should pay special attention to improve the health-related quality of life, especially general health and physical functioning of spinal patients receiving workers compensation.

The role of spinal instrumentation is to provide mechanical stability, obtain and maintain anatomic alignment, and promote fusion. The American Society for Testing and Materials (ASTM) introduced guidelines and procedures so that biomechanical properties of different implant designs could be compared in a consistent manner. Combined with biomechanical analyses, clinical evaluation allows the safety and efficacy of a spinal implant system to be determined before construction. The objective of our study was to determine the biomechanical properties and clinical performance of the OMEGA-21 Spinal Fixation System. Static and dynamic (fatigue) biomechanical testing was performed per ASTM guidelines and recommendations on individual components and on the system assembled in a corpectomy model. Clinical and radiographic evaluation of 57 consecutive patients with indications for instrumented spinal arthrodesis of the lower dorsal lumbar and sacral segments of the spine was performed at a mean follow-up of 31.9 months. Static and fatigue testing revealed superior biomechanical properties of the individual components and of the assembled system. The mechanical-strength values of the system were comparable with maximum reported values for existing implant designs. At final clinical follow-up, 86% of patients obtained relief of their symptoms; 84% considered their clinical results to be excellent or good. Ninety-one percent of patients satisfied radiographic criteria for bony fusion. There were 5 implant-related complications: 2 misplaced screws (2 patients), local pain above the implant (2 patients), and 2 broken expansive screws (1 patient). Biomechanical and clinical results indicate that the OMEGA-21 system is feasible and performs well as a spinal instrumentation system for the lower dorsal, lumbar, and sacral spine.

Lumbar interbody fusion can be performed anteriorly or posteriorly. An anterior approach generally requires an access surgeon and often is combined with a posterior fusion. A traditional posterior interbody fusion can destabilize the spinal motion segment and requires neural retraction. A new surgical technique, a transforaminal lumbar interbody fusion (TLIF), was recently described. It requires minimal neural retraction, and the disk space is exposed posterolaterally with removal of only one facet joint. This study compares the cost of an anterior-posterior one-level lumbar fusion with the cost of the same procedure performed using the TLIF technique. Table 1 lists the specific demographics. A retrospective review of the hospital charges of 80 patients undergoing interbody lumbar stabilization was conducted. The two groups consisted of 40 patients with an anterior-posterior fusion and 40 patients who were fused circumferentially using the TLIF technique. A cost analysis with normalization of 1998 dollars between the two groups was performed. The TLIF group had an average operative time of 213 minutes, compared with 269 minutes for the anterior-posterior group. In addition, an average additional 38 minutes were required to turn the patient from the anterior or posterior position. The average blood loss for the anterior-posterior procedure was 969 mL, compared with 489 mL for the TLIF group. Twenty-three of the anterior-posterior patients received an average of 2.2 units of blood and six of the TLIF patients received an average of 1.3 units. Use of the surgical intensive care unit was much lower in the TLIF group (38 of 40 patients versus 2 of 40 patients). The average length of stay was 6.1 days for the anterior-posterior group compared with an average of 3.3 days for the TLIF group. The average cost of the anterior-posterior patients was $49,085, compared with $33,784 for the TLIF group. Cost analysis between the two groups show the TLIF patients had an average savings of approximately $15,000 per admission. This cost comparison was conducted only for the time of the operative procedure. No attempt was made to analyze rates of fusion between the two groups or ultimate clinic outcome. There were no major complications in either group, and no patient returned to surgery for a lumbar spinal problem at the authors' hospital within 1 year of the index procedure.

Background Context: Pedicle screw fixation in osteoporotic bone and in revision of previous pedicle screw fixation cases presents a significant challenge to spine surgeons. Biomechanical tests have shown that a pedicle screw that expands within the vertebrae body can substantially improve fixation in the presence of compromised bone., Purpose: To review the clinical and radiographic results with the use of expandable pedicle screws., Study Design: One hundred forty-five patients received one or more expandable pedicle screws from the Omega21 spinal fixation system (EBI, L.P., Parsippany, NJ) to obtain thorocolumbar or lumbosacral stabilization., Patient Sample: The indications for use of the expandable screws were osteoporosis (21 cases), reoperation of previous pedicle instrumentation (27 cases), intraoperative screw relocation (17 cases), construct reinforcement (23 cases), and sacral anchoring to avoid the necessity of anterior penetration of the sacral cortex (57 cases)., Outcome Measures: The presence of radiographic fusion and complications arising from the instrumentation were reviewed at a mean follow-up period of 35 months (range, 24-72 months)., Methods: A retrospective clinical and radiographic review was performed. Fusion was evaluated based on anterior-posterior and lateral radiographs as well as dynamic radiographs in flexion and extension., Results: Radiographic evidence of fusion was obtained in 125 of the 145 cases (86%). Eighty-six percent of patients with osteoporosis and 89% of reoperations fused. There were no instances of screw loosening or pullout of the expandable screws. Screw breakage occurred in four patients (2.8%), including three patients where fusion was not obtained. In six patients the expandable screws were removed without difficulty after fusion because of local discomfort., Conclusion: The results of this study have shown that expandable pedicle screws can be efficacious in cases in which pedicle screw fixation is difficult and adds a valuable tool to the growing armamentarium of spinal instrumentation.

Multilevel anterior cervical discectomy and fusion (ACDF) remains a difficult problem. A recently described surgical technique for multilevel ACDF has eliminated the morbid complications associated with harvesting iliac crest bone graft (ICBG) while maintaining the advantages of using autologous bone graft. A matched-pairs t test was used to compare the estimated costs of 27 ACDFs using titanium surgical mesh, local autologous bone graft, and anterior plate instrumentation with 27 ACDFs using ICBG and plate fixation. The three variables considered were cage cost, operating time (cost), and hospitalization cost. The estimated costs for the two surgical procedures were not significantly different. Thus, the time saved by not harvesting an ICBG was comparable to the cost of the cage. Harvesting ICBG also increased the morbidity rate by 22%.

Allograft struts are used to reinforce the deficient proximal femur in hip arthroplasty or for fixation of a periprosthetic fracture. Although the use of strut grafts wired or cabled to the proximal femur generally has been successful, the time for healing is slow. The purpose of the current study was to determine whether cortical strut graft healing to the femur could be enhanced by the addition of recombinant human osteogenic protein-1. Fourteen adult dogs underwent bilateral onlay allograft strut procedures to the midfemur using stainless steel cables. In each animal one femur received 500 mg of osteogenic protein-1 device (2.5 mg recombinant human osteogenic protein-1/g Type I collagen) interposed between the graft and host bone. The results showed that the healing of cortical strut grafts to the femur was enhanced dramatically by the addition of the osteogenic protein-1 device. The sites treated with osteogenic protein-1 had significantly greater radiographic, histologic, and microradiographic scores at all times. Rapid formation of new bone and graft incorporation was observed in sites treated with the osteogenic protein-1 device. Strut healing with the osteogenic protein-1 device at 4 weeks postoperative was superior to the healing in control sites at 8 weeks. Improving and accelerating the course of cortical strut graft healing should provide a substantial clinical benefit in lowering the risk of graft nonunion and fracture and shorten the time of protected weightbearing and functional disability.

A case of distal aortic occlusion after circumferential lumbar spine surgery is presented. The paradoxical clinical findings are discussed.

The advantages of pedicle screw fixation depend on their ability to retain bony purchase until the fusion mass is stable. Osteoporotic bone and removal and replacement of pedicle screws in revision procedures substantially reduce screw mechanical fixation strength and can lead to clinical failure. The objective of this study was to determine if an expansive pedicle screw design could be used to improve biomechanical fixation in bone of compromised quality. Axial mechanical pullout testing was performed on paired expansive and conventional pedicle screws placed in fresh, unembalmed cadaveric vertebrae. Bone mineral density measurements (made using a dual-energy X-ray absorption meter) were used to characterize bone quality. A preliminary clinical and radiographic evaluation of 14 patients was also performed at a minimum 2-year follow-up. The mean axial pullout force in bone of all qualities was increased 30% when the expansive pedicle screw design was used. This included an appropriate 50% increase in pullout force in bone of poor quality (low bone mineral density). The preliminary clinical and radiographic results were supportive of the biomechanical design rationale and mechanical testing. The results were similar to those expected for spinal instrumentation using pedicle screws, even though compromised bone was present in two thirds of the cases in which the expansive screw was used.

Monosegmental cervical spondylosis with radiculopathy requiring operative intervention responds well to anterior disc excision and fusion with autograft. However, there is a 20% to 25% morbidity from the donor site. Several new surgical techniques using biomechanical spacers or internal fixation have been developed that can be used with local bone or allograft, thus eliminating donor site morbidity. Surgical outcomes are comparable with those of traditional anterior cervical discectomy and fusion.

Thirty-five consecutive patients were evaluated at an average follow-up time of 20 months after circumferential lumbar spinal fusion. All patients had degenerative conditions of the lumbar spine and same-day anterior spinal fusion by using titanium cages packed with autograft bone and posterior instrumentation combined with a posterolateral autogenous bone graft. The purpose of this study was to determine whether anterior titanium cage placement and posterior instrumentation with autologous bone graft was a safe and efficacious procedure in patients with degenerative disease of the lumbar spine. Fusion rates, complications, pain relief, medication use, and work status were specifically analyzed. Although previous reports documented the use of this technique for trauma and tumor cases, few studies assessed clinical and radiographic results in patients with degenerative conditions of the lumbar spine. Plain radiographs were used to determine spinal fusion at each spinal level. All patients were administered preoperative and postoperative questionnaires regarding three specific clinical-outcome parameters. These consisted of pain level, medication use, and work status. Intraoperative and postoperative complications were also documented. Radiographic results showed that 61 (97%) of 63 lumbar levels undergoing an arthrodesis procedure fused either anteriorly, posteriorly, or both. Of the 35 patients in this series, 33 (94%) fused at all levels, and two did not. Substantial pain relief was reported in 46% of all patients. Thirteen (37%) patients had one or more surgical complications. Circumferential spinal fusion in patients with degenerative etiologies yields excellent radiographic fusion rates and good pain relief. The procedure is technically demanding and is associated with a high rate of complications.

We prospectively determined the risk of initial stinger experience in a group of college football players while considering the presence of cervical canal stenosis and each player's position, playing time, and body type. Prospective analysis revealed a 7.7% incidence of initial stinger experience. The average Torg ratio for all players was 0.924 +/- 0.122, with the seventh cervical level being the narrowest. Initial stinger experience depended on position played and body type. The Torg ratio did not influence initial stinger occurrence. Players who experienced multiple stingers, however, had significantly smaller Torg ratios than players experiencing only one stinger (0.75 versus 0.87). A Torg ratio of 0.70 may be a more statistically and clinically appropriate threshold for determining significant cervical stenosis and advising collegiate athletes of their risk of experiencing recurrent stingers.

Study Design: This study analyzed the fusion rate and clinical success rate in adult patients undergoing surgical treatment for symptomatic, low grade, isthmic spondylolisthesis. A postoperative questionnaire and grading scale were used to judge clinical success. Successful fusion was judged using radiographic criteria., Objective: To evaluate the clinical success and fusion success in a group of adult patients undergoing instrumented posterolateral arthrodesis for symptomatic isthmic spondylolisthesis., Summary of Background Data: Seventeen consecutive adult patients with symptomatic low grade isthmic spondylolisthesis underwent the identical surgical procedure consisting of Gill laminectomy, L5 nerve root decompression, Luque pedicle-screw plate instrumentation, and posterolateral arthrodesis at L5-S1 using autogenous iliac crest bone graft. Results were analyzed at an average 30-month follow-up., Methods: An independent observer reviewed the results using a postoperative questionnaire to determine rates of return to work, symptom relief, and analgesic medication usage. Radiographs were evaluated to determine the fusion status., Results: Seventeen patients were evaluated at an average of 30 months after the index procedure. Sixteen of 17 had solid fusions using radiographic criteria. Sixteen of 17 had satisfactory clinical results. Eight of 13 (62%) employed patients, including three of six patients with worker's compensation, returned to their usual jobs., Conclusions: An instrumented posterolateral arthrodesis in combination with a Gill procedure and L5 nerve root decompression results in a high rate of fusion, satisfactory clinical success, and a high rate of return to work.

Study Design: Posterior lumbar spinal fusion segments were evaluated in 9 adult mongrel dogs 6, 12, and 26 weeks after implantation. Four sites on each animal received implants consisting of demineralized bone matrix alone, demineralized bone matrix with allograft bone, allograft bone alone, and autograft bone. Each unilateral fusion spanned one motion segment with one intervening vertebral level left undisturbed using T13-L7. The fusions were evaluated radiographically, mechanically, and histologically., Objective: The purpose of this study was to determine the efficacy of demineralized bone matrix as a bone graft substitute for stable posterior spinal fusion., Summary of Background Data: Posterior spinal fusion is a procedure commonly performed for spinal stabilization. Increasing the incidence and speed of stable spinal fusion is a primary goal in spinal surgery. Concerns have developed regarding the graft material used to induce bone healing at the fusion site. The advent of osteoinductive materials, such as demineralized bone matrix, may eliminate the need to harvest autograft bone and may circumvent the immunologic response and lower osteogenic potential associated with allograft bone., Methods: The quality of fusion and new bone formation was evaluated radiographically using plain films, computed tomography, and magnetic resonance imaging. After the dogs were killed, each fusion segment was evaluated mechanically in torsion to determine stiffness and histologically to determine qualitative parameters of new bone formation and remodeling., Results: Radiographic studies showed that autograft bone sites achieved stable fusion by 26 weeks after surgery. Conversely, the demineralized bone matrix alone and with allograft bone demonstrated some new bone formation at 6 and 12 weeks, but did not achieve fusion by 26 weeks. The fusion sites of allograft bone alone showed minimal new bone formation at all time periods. Mechanically, the autograft fusion sites demonstrated torsional stability that was significantly greater than that of all other fusion sites at all time periods. The remaining fusion sites showed equivalent torsional stiffness at all time periods. Histologic analysis confirmed the radiographic and mechanical findings., Conclusions: The results indicate that demineralized bone matrix alone or with allograft bone is ineffective in achieving stable posterior spinal fusions.

Occurrence of ganglion cysts in the spine is extremely rare. Common symptoms include intermittent lumbar pain and pain at night. Neurological examination to distinguish from other etiologies of radicular pain may be difficult. The L4-L5 level is the most common sight of occurrence. Radiographically, degenerative changes, particularly spondylolisthesis, are a common finding. MRI appearance of the cysts is variable, according to the composition of the cyst. A ganglion cyst should be considered in the differential of radicular pain in the presence of degenerative changes of the lumbar spine.

Study Design: In an attempt to evaluate the effects of bone mineral density on the quality of fixation of pedicle screws in the lumbar spine, the axial pullout force was determined and compared in normal and osteoporotic human lumbar spines., Objectives: Four techniques of screw hole preparation were evaluated. Two pedicle screw/offset laminar hook constructs also were evaluated to determine whether the adjunct fixation of the laminar hooks would improve quality of fixation to a level sufficient to allow their use in the osteoporotic lumbar spine., Methods: Pedicle screws were inserted by one of the listed techniques into fresh frozen cadaveric human spines. The fixation strength then was evaluated by pullout on a uniaxial testing frame., Results: Bone mineral density was a strong influence on axial pullout force. In normal bone, the method of screw hole preparation did not significantly affect the quality of fixation. However, in the osteoporotic spine, either an untapped screw hole or the tapping of a screw hole with a 5.5 mm tap improved the pullout force a statistically significant amount (P < 0.003). Also, a pedicle screw with offset hooks at two adjacent levels improved the fixation significantly, increasing the pullout force to twice the expected value., Conclusion: Pedicle screw pullout strength was highly correlated with bone mineral density. A 5.5 mm tap or preparation with a ganglion knife improved pullout strength. Use of pedicle screws in conjunction with laminar hooks at two levels improved pullout strength.

Study Design: The effectiveness of Polyactive (Osteotech, Inc., Shrewsbury, NJ), an elastomeric segmental copolymer, as a barrier material for the prevention of perineural scar formation was evaluated in eight adult mongrel dogs. Two animals each were killed at 2, 4, 8, and 12 weeks postoperation., Objective: This study determined the ability of a Polyactive membrane to prevent perineural scar and compared the results to those obtained using free fat graft and nonimplanted control subjects., Summary of Background Data: Perineural scar formation after laminectomy presents considerable morbidity in lumbar surgery. To date, a wide variety of materials has been evaluated to prevent scar formation including free fat grafts, mechanical barrier devices, hemostatic agents, and anti-inflammatory drugs. However, all studies indicate scar formation is present, and the search for an effective barrier continues., Methods: Gross dissection, radiographic studies, including computed tomography and magnetic resonance imaging, and histologic sections were used to evaluate the presence and degree of perineural scarring. If scarring was evident in each of the evaluations, the degree was graded on a 0-3 scale where: 0 = no scarring; 1 = mild scarring; 2 = moderate scarring; and 3 = extensive scar formation., Results: Polyactive membranes were an effective barrier with only minimal scar formation to the dura observed at any time period. Free fat graft was an effective barrier to scar formation at early time periods; however, progressive fat graft degradation with some increased scarring was observed at latter time periods. Nonimplanted control defect sites resulted in moderate to severe scar formation to the dura as early as 2 weeks postimplantation., Conclusions: The results indicate Polyactive is a reliable and effective means of reducing perineural scar formation. The effectiveness of the Polyactive membrane could be improved markedly if techniques or methods to ensure retention of the membrane in the proper position were developed.

Study Design: The efficacy of solid hydroxylapatite (HA) blocks for obtaining cervical interbody fusion was studied in a canine model. Each of 21 adult colony-reared hounds received a hydroxylapatite implant and an autogenous bone graft in the C3-C4 and C5-C6 disc interspaces. Seven dogs each were killed at 6, 12, and 26 weeks postoperation., Objective: This study determined the rate, mechanical strength, and histologic characteristics of cervical interbody fusions achieved using a hydroxylapatite (HA) block and compared the results to those obtained with autogenous iliac crest bone graft., Summary of Background Data: The use of corticocancellous autograft has been successful in a high percentage of anterior cervical interbody fusions. Calcium phosphate ceramics may provide an alternative to autogenous and allogenous tissue. These materials are biocompatible and capable of direct intimate bonding with bone because of their chemical similarity to bone mineral., Methods: Radiographic evaluation including plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) studies were used to determine fusion quality. Specimens were also subjected to mechanical testing to determine bending and torsional stiffness as well as ultimate load to failure. Histologic evaluation included integrity and incorporation of the graft materials and interface characterization., Results: The CT images were well correlated with plain radiographs and demonstrated progressive incorporation of the graft materials with time. Magnetic resonance images were of little value in evaluating quality of fusion; the autograft sites demonstrated progressive disc height loss with time. Minimal disc height loss was observed with HA blocks. There was no statistical difference in torsional stiffness for the HA blocks and autogenous bone grafts at any time period. In bending, the HA block sites were significantly stiffer at 6 weeks (P < 0.005). There was no statistical difference in the ultimate failure load for the HA and autogenous bone grafts. Histologically, the HA blocks demonstrated areas of direct bone apposition with increased bone appositions and implant incorporation with time. At 6 and 12 weeks postoperation, the autograft sites demonstrated areas of graft resorption and some new bone formations. By 26 weeks, new bone was continuous with the vertebral endplates., Conclusions: The results indicate that HA blocks may provide an alternative to autogenous graft materials for anterior cervical interbody fusion. Block slippage and/or fracture may occur in a small number of patients but is primarily related to insertion technique and does not appear to significantly alter the final result.

Study Design: Posterior spinal fusion segments were evaluated in adult mongrel dogs at 6, 12, and 26 weeks post-implantation. Four sites on each animal received implants consisting of recombinant human osteogenic protein-1 on a bone collagen carrier, bone collagen carrier alone, autogenous iliac crest bone, or no implant material., Objective: To determine the efficacy of recombinant human osteogenic protein-1 as a bone graft substitute in achieving posterior spinal fusion and compare the results to those obtained using autogenous bone graft., Summary of Background Data: Posterior spinal fusion generally includes onlay grafting of autogenous or allogeneic bone after decortication of bony surfaces of the vertebral elements. The search for an acceptable bone graft substitute material has in recent years centered upon proteins capable of inducing bone in vivo. Recombinant human osteogenic protein-1 has demonstrated efficacy in healing large segmental osteoperiosteal defects in rabbits, dogs, and monkeys and appears ideally suited as a bone graft substitute for spinal fusions., Methods: The quality of fusion and new bone formation was evaluated using plain films, computed tomography, and magnetic resonance imaging., Results: Radiographic and histologic studies demonstrated that recombinant human osteogenic protein-1-treated fusion segments attained a stable fusion by 6 weeks post-implantation and were completely fused by 12 weeks. The autograft sites demonstrated fusion at 26 weeks post-implantation., Conclusions: The results indicated that recombinant human osteogenic protein-1 is an effective bone graft substitute for achieving stable posterior spinal fusions in a significantly more rapid fashion than can be achieved with autogenous bone graft.

A rabbit ulnar non-union model was used to evaluate the effect of recombinant human osteogenic protein-1 on the healing of a large segmental osteoperiosteal defect. A 1.5-centimeter segmental defect was created in the mid-part of the ulnar shaft of adult rabbits. The defect was filled with an implant containing either recombinant human osteogenic protein-1 or naturally occurring bovine osteogenic protein. The recombinant human osteogenic protein-1 implants consisted of a carrier of 125 milligrams of demineralized, guanidine-extracted, insoluble rabbit bone matrix (the collagen carrier), reconstituted with 3.13, 6.25, 12.5, twenty-five, fifty, 100, 200, 300, or 400 micrograms of recombinant human osteogenic protein-1. Animals that received recombinant human osteogenic protein-1 were compared with animals that received an implant of 250 micrograms of a preparation of naturally occurring bovine osteogenic protein mixed with the collagen carrier. Limbs that served as controls received either the collagen carrier alone or no implant at all. The treated and the untreated defects were examined radiographically and histologically at eight or twelve weeks after implantation. Mechanical testing was performed on six animals. All implants of recombinant human osteogenic protein-1, except for those containing 3.13 micrograms of the substance, induced complete radiographic osseous union within eight weeks. The defects that were treated with an implant of bovine osteogenic protein also healed within this time-period. The bone induced by both types of implants had new cortices with advanced remodeling and marrow elements. Histological evaluation of this new bone at eight weeks postoperatively revealed primarily lamellar bone, with the formation of new cortices and normal-appearing marrow elements. The average torsional strength and energy-absorption capacity of the union induced by recombinant human osteogenic protein-1 was comparable with that of intact bone. The control defects that had been implanted with collagen carrier alone and those with no implant showed no bridging of the defect.

Fourteen patients with a previous lumbosacral fusion underwent neural decompression and fusion of degenerated adjacent motion segment. The most common level was L3-L4, and there was an average of 3.2 (range 1-7) previous lumbosacral surgical procedures. The average interval from the first fusion until operative intervention on the degenerated adjacent segment was 11.5 years (range 3-29 years). Five patients had an uninstrumented fusion, of which only one progressed to arthrodesis. Three of these five patients with pseudarthrosis after uninstrumented fusion--and the remaining nine patients--had fusions with instrumentation. Ten of twelve instrumented fusions progressed to solid arthrodesis. The pseudoarthrosis rate of 80% was decreased to 17% with the use of supplemental instrumentation. There was a significant number of complications and poor results, especially in patients with advanced osteoporosis and those with a short interval between adjacent segment degeneration, respectively. Eleven of 14 patients reported some postoperative pain relief.

The Texas Scottish-Rite instrumentation (TSRH) is a new system for the correction of spinal deformities that uses smooth rods and hooks stabilized to the rod with a three-point interference fit. This obviates the need for the break-off hex bolts and should make for easier removal and/or revision. Twenty-three patients with TSRH instrumentation were followed for an average of 18 months after surgery. The major scoliotic curve was corrected an average of 49% with the compensatory curve averaging 37% correction. Loss of thoracic kyphosis was less than 9 degrees although it increased on average 8 degrees in those patients where kyphosis was improved. There were no acute complications, but late complications included four cases of hook pull-out. Results are comparable to those found with the CD instrumentation. The TSRH instrumentation is an attractive alternative in scoliosis surgery, particularly because of the relative ease in which revision surgery may be performed.

Histologic examination was performed on 42 uncemented, porous-coated acetabular components removed for reasons not related to fixation. Included were 20 devices that had fixed pegs or spikes to aid in initial fixation and 22 devices that used screws through the component. The diagnoses and patient ages at insertion, times in situ, and reasons for removal were comparable for the two groups. Bone ingrowth was observed in 28 of the 42 acetabular components (67%). Of the 20 components with pegs or spikes, nine had no bone ingrowth, six had minimal bone ingrowth, four had moderate ingrowth, and one had extensive bone ingrowth. Of the 22 components with screws, five had no bone ingrowth, six had minimal bone ingrowth, six had moderate bone ingrowth, and five had extensive bone ingrowth. Two of the devices with screws also had external threads on the metallic shell; neither had any bone ingrowth, and the two accounted for two of the five devices having no bone ingrowth in this group. Bone ingrowth occurred more frequently, in greater amounts and was more evenly distributed anatomically in cups using screws for initial adjunct fixation. Roentgenographic and clinical findings were unreliable in predicting ingrowth of bone.

The effect of a plasma-sprayed hydroxylapatite (HA) coating on the degree of bone ingrowth and interface shear attachment strength was investigated using a canine femoral transcortical implant model. Cylindrical implants were fabricated by sintering spherical Co-Cr-Mo particles 500-710 microns in diameter; the nominal implant dimensions were 5.95 +/- 0.05 mm diameter by 18 mm in length. One half of each implant was coated with hydroxylapatite, 25-30 microns in thickness, by a plasma-spray technique. Using strict aseptic technique, the implants were placed through both femoral cortices into defects approximately 0.05 mm undersized. After 2, 4, 6, 8, 12, 18, 26, and 52 weeks, the implants were harvested and subjected to mechanical pullout testing and undecalcified histologic evaluation. The application of the HA coating to porous implants enhanced both the amount of bone ingrowth and the interface attachment strength at all time periods. These differences were statistically significant for the percent of bone ingrowth at the 4-, 6-, 12-, 18-, 26-, and 52-week time periods, and interface shear strength values were significantly different at the 6-, 8-, 12-, 18-, and 26-week time periods. The rate of development of interface strength and bone ingrowth was also more rapid for the HA-coated implants. No evidence of any disruption, mechanical failure, or biologic resorption of the HA coating was observed. The results of the present study--demonstrating a beneficial effect of the HA coating at all time periods--are believed to be due to the use of paired comparisons, which allow assessment of subtle differences that might otherwise have been obscured by normal biological variability.

Postlaminectomy instability of the cervical spine can be managed either anteriorly or posteriorly. The posterior procedures that have been described are best performed at the time of the original decompressive procedure. Thus, the development of a kyphotic deformity is prevented. Generally, it is technically easier to achieve anterior stabilization and arthrodesis if a postlaminectomy kyphosis develops.

A study was undertaken to determine if a somatosensory conduction delay is present in the posterior columns of adolescents with idiopathic scoliosis. Somatosensory evoked potentials were recorded after median and posterior tibial nerve stimulation in 12 adolescent subjects being followed for idiopathic scoliosis with an average age of 14.6 years (range, 12.0-16.6 years). Twelve normal controls matched for age, sex, race, and height underwent identical testing. Evoked potential peak latencies were measured and conduction velocities calculated. Results showed no difference between scoliotics and normal controls. Comparable posterior column conduction velocities were recorded in both groups. If a defect in posterior column function does exist in adolescent idiopathic scoliosis, as previously postulated, it is not reflected by a conduction delay as measured by somatosensory evoked potential testing.

A follow-up study of the bone mineral densities (BMD) of 22 female subjects with idiopathic scoliosis was performed using dual-photon absorptiometry at an average follow-up period of 30.8 months. Compared to the initial scans, statistically significant increases in lumbar spine and femoral neck BMD were observed. When compared to normal subjects, approximately half of the scoliotic subjects were markedly osteoporotic, having BMD measurements at least two standard deviations below the expected value. Scoliotic curvature data could not be correlated with the BMD data. The observed osteoporosis is not transient and appears characteristic of idiopathic scoliosis.

Dual-photon absorptiometry (DPA) with a 153gadolinium radionuclide source was used to measure bone mineral in the lumbar spine of 109 subjects and the femoral neck of 100 subjects 3-20 years of age. From the scan data collected, multiple linear regression models were developed to predict the measured bone mineral density values as a function of age, height, and weight; male and female data were evaluated separately. From the table of predicted values, a particular subject's bone mineral measurements can be readily compared with that of normal subjects in the same way "growth charts" are commonly used to assess development.

The case of a 16-year-old boy with an aneurysmal bone cyst of the fourth lumbar vertebra and a herniated nucleus pulposus of the L4-5 disc is presented. Symptoms included progressive lower back pain and bilateral lower extremity weakness. Roentgenographic studies were consistent with a vertebral aneurysmal bone cyst with an expansile lesion that compromised the neural canal and an L4-5 herniated nucleus pulposus. Surgical treatment included tumor excision, L4-5 discectomy, lumbar decompression, and posterolateral and anterior lumbar fusion. Postoperatively, the lower back pain and lower extremity symptoms resolved. The patient continues to do well at 1-year follow-up.

We studied the radiographs of thirty-two patients with Down syndrome for evidence of atlanto-axial instability. One of the patients had instability in 1970 and seven had it in 1983. The interval between the atlas and the odontoid process in the patients who demonstrated motion at that interval radiographically averaged 2.78 millimeters in 1970 and 6.93 millimeters in 1983 (p less than 0.005). Four patients whose radiographs showed atlanto-axial motion in 1970 lost that motion by 1983, and in seven patients who did not show atlanto-axial instability in 1970 it developed by 1983. Atlanto-axial instability was more likely to develop in boys who were more than ten years old. Accessory upper-cervical ossicles became evident in three patients, none of whom had atlanto-axial motion. However, one of these three patients had an abnormally wide atlanto-axial interval.

In those instances of failed posterior arthrodesis for spondylolisthesis, iatrogenic spondylolisthesis due to posterior neural decompression or severe (grade III or IV) spondylolisthesis, anterior stabilization using a fibular strut graft appears to be feasible and successful. Eleven patients were treated with this technique and ten achieved solid anterior arthrodesi; the eleventh fused posterolaterally. All improved symptomatically with no postoperative complications, including sexual dysfunction in the male.

Eight mechanically failed Harrington rods have been retrieved and examined clinically, metallurgically, and biomechanically to characterize the mode of instrument failure and to determine how future failure rates might be minimized. The results of the study indicated fatigue to be the mode of mechanical failure in all cases, however, in only one case was any significant metallurgical defect observed. Failure occurred at the ratchet-shaft junction in seven of eight cases with the remaining failure occurring at the midshaft region. This occurred in the rod with the metallurgical defect. The possibility of fatigue failure can be lowered by implementing both clinical and design considerations. Clinically, stress on the rod can be lowered by placing the ratchet-shaft junction as close to the hook as possible and by using the shortest rod possible. Both of these will minimize the moment arm at the vulnerable ratchet-shaft junction. Design modifications, including increased rod diameter, polishing the ratchet-shaft interface and material changes, can also be used to lower the stress on the rods and thus reduce the risk of mechanical failure.

From January 1986 to June of 1987, 40 patients underwent transpedicle fixation and fusion using the variable spinal plate system. Nineteen patients had undergone surgery at the same level or levels, and 21 patients had undergone no previous surgery. Diagnostic categories include spondylolisthesis, thoracolumbar and lumbar fractures, internal disc derangement, spinal stenosis, pseudarthrosis, mechanical instability, and fracture mal-union. Minimum follow-up has been 14 months, with the average being 20 months. Overall results showed 13 excellent, 12 good, seven fair, and eight poor. The overall complication rate was 45%. In those patients undergoing no previous surgery, it was 29%, but with those patients having previous surgery, it was 63%. Most of these complications were minor in nature and resolved before discharge. Implant failure occurred in seven patients, and consisted of screw breakage. Design modifications currently available should help minimize this complication. Although this method of internal fixation and fusion is technically demanding and has a high complication rate, it is considered to be indicated in lumbar fractures, revision of pseudarthrosis, spondylolisthesis with or without reduction, and failed surgery with marked instability.

Eleven cases of fracture of the thoracic and lumbar spine were treated with segmental spinal instrumentation (Luque rods). The majority of these injuries occurred in motor vehicular accidents or falls from a height and were usually associated with multisystem trauma. This method of instrumentation provided immediate rigid internal fixation, which obviated the need for postoperative orthoses, allowed easier nursing care and early ambulation, and facilitated rehabilitation of patients with spinal cord injury. At 13 months' average follow-up, there have been no instances of wire breakage, rod deformation, or deterioration of neurologic status. This favorable experience suggests that segmental spinal instrumentation should be considered as an alternative mode of spinal instrumentation in fractures of the thoracic and lumbar spine.

In order to determine the validity of cervical discography in the diagnosis and treatment of patients presenting with cervical discogenic syndrome, a retrospective analysis of 34 patients who underwent cervical arthrodesis on the basis of positive cervical discography was performed. The symptomatic cervical levels were selected by reproduction of the patient's symptoms at the time of injection. No patient had radicular symptoms, and other diagnostic modalities such as computed tomography (CT) scanning or myelography had been within normal limits. Seventy percent of patients who underwent surgical intervention had good or excellent results. With proper utilization, cervical discography is a valid diagnostic study.

This study determined whether a significant difference in response to vibratory stimuli was consistently present in a large group of children with idiopathic scoliosis as compared with age-matched controls. Fifty-eight unselected adolescent females with documented progressive idiopathic scoliosis were studied along with age-matched controls. Threshold to detection of a vibratory stimulus was measured in both the right and left upper and lower extremities. Results indicated that highly significant differences existed between scoliotic children and controls at all sites tested (p less than 0.01), with scoliotic children being more sensitive than controls. The results support the presence of a central aberration in posterior column function that may be a primary etiology of idiopathic scoliosis.

Operative treatment for cervical spondylotic myelopathy and myeloradiculopathy by anterior decompression produced functional improvement of one grade (Nurick's rating system) in 16 of 21 patients evaluated at 32 months average follow-up period. The best results occurred in patients with symptoms for less than one year and classified as grades I-III. The anterior approach for decompression is preferred because it is directed toward the degenerative structures responsible for cord and root compression. The autogeneic fibula dove-tailed strut graft is favored over an iliac crest bone graft because with multilevel decompression in the cervical spine, it provided structural stability and a high union rate. There were no neurologic complications in this series of 21 cases.

Abnormalities in the upper cervical spine resulting in cervical myelopathy in patients with Down's syndrome have been well-documented. However, two adult Down's syndrome patients recently presented with cervical myelopathy secondary to abnormalities of the lower cervical spine. Because of this, 105 Down's syndrome patients with normal upper cervical spines were evaluated clinically and radiographically. They were found to have an increased prevalence of lower cervical spondylosis that significantly correlated with physical findings consistent with cervical myelopathy. Therefore, physicians dealing with Down's patients should closely monitor neurological function and obtain flexion/extension laterals of the cervical spine to evaluate C1-C2 instability and degenerative changes in the lower cervical spine if a change in neurologic status is noted.

Proprioception testing and gait analysis was performed on a group of 17 patients with idiopathic scoliosis. All curves had documented progression. The average curve was 26.8 degrees, all primary curves being right thoracic. The average age was 14.8 years. Twelve, healthy, age-matched controls underwent identical testing. Results showed that scoliotic subjects had asymmetry in their ability to reproduce angles between their two knees, as well as an absolute deficit in their ability to reproduce angles as compared with controls (P less than 0.01). The threshold of detection of change in angle at the knee was also quantitatively higher than controls (P less than 0.05), although asymmetry was not statistically significant. No significant differences were measured in gait parameters between scoliotics and controls. These joint position tests have been applied previously to young and elderly adults, athletes, and total joint patients. In no group has any asymmetry of response been demonstrated, both extremities showing virtually identical performance in each case. The tests administered measure sensory modalities, which are conducted through the posterior columns. Although the site of damage in the neural pathway cannot be specifically localized by these tests, results of this study support the presence of a neurologic deficit in idiopathic scoliosis.

Spondylolysis occurred distal to spinal instrumentation and fusion to a lower lumbar level in a patient with osteogenesis imperfecta. Initial extension to the sacrum may avoid this complication in patients with a weakened spinal column.

Vibratory studies were performed on 10 adolescent subjects being followed for congenital scoliosis. The average age was 12 years 4 months and the average curve was 32 degrees. Twenty-one age-matched controls underwent identical studies. Threshold to detection of vibratory stimuli in the upper and lower extremities was quantified. Results showed that the scoliotic subjects were consistently less sensitive than the controls in the lower but not the upper extremity. The occurrence of hyposensitivity in only the lower extremity of persons with congenital scoliosis implies that the sensory deficit is secondary to the spinal deformity itself rather than a primary etiologic factor.