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A 7-year-old boy presented with vertebra plana of T11. The presumptive diagnosis suggested by clinical presentation, conventional radiographs, and computed tomographic scans was eosinophilic granuloma. Progressive neurologic symptoms required surgical excision of the lesion and decompression. Histopathologic examination of the surgical specimen confirmed the diagnosis of Ewing sarcoma.

The combination of improved resection, stabilization, and fusion techniques allows for more aggressive removal of malignant spinal tumors with acceptable mortality and morbidity. Thirty consecutive patients with primary sarcomas of the mobile spine, who were operated on at the authors' institution from January 1970 to December 2000, were included in the current study. Demographic information, tumor location, type of resection, resection margins, local recurrence, and overall survival data were retrieved and analyzed. Treatment consisted of en bloc resection in 12 patients (40%) and piecemeal resections in 18 patients (60%). The resection was classified as wide in seven patients (23.3%), marginal in three patients (10%), and intralesional in 20 patients (66.7%). Pathology reports showed tumor-free resection margins in 12 patients (40%). In the remaining 18 patients (60%), resection margins were positive and resulted in a fivefold increase in the risk of a local recurrence. Ninety-two percent of the patients with local recurrence died of sequelae associated with the local recurrence. Primary sarcomas of the mobile spine in certain cases, can be removed completely with tumor-free resection margins. En bloc resection with tumor-free margins provides substantial improvement in overall survival.

Major sacral resection generally is reserved for patients with malignant lesions. Because of the uncommon nature of these diseases, little is known about outcomes of surgical treatment. The current authors describe the retrospective analysis of bowel and bladder function in patients having major sacral resection at their institution during a 10-year period. Fifty-three patients were identified. In patients who had unilateral sacrectomy, in whom the contralateral sacral nerves were preserved, normal bowel and bladder function was retained in 87% and 89%, respectively. In patients who had bilateral S2-S5 nerve roots sacrificed, all had abnormal bowel and bladder function. In patients who had bilateral S3-S5 resection, normal bowel and bladder function was retained in 40% and 25%, respectively. In patients who had bilateral S4-S5 resection, with preservation of the S3 nerves bilaterally, normal bowel and bladder function was retained in 100% and 69%, respectively. In patients who had asymmetric sacral resections, with preservation of at least one S3 nerve root, normal bowel and bladder function was retained in 67% and 60%, respectively. These results show that unilateral resection of sacral roots or preservation of at least one S3 root in bilateral resection preserves bowel and bladder function in the majority of patients.

Cartilage defects are common, painful conditions and none of the currently available treatment options are satisfactory. Tissue engineering techniques involving scaffolds made from biodegradable synthetic polymers hold great promise for the future. These materials can be manufactured in an injectable form for minimally invasive procedures or in a preformed state to treat large irreparable lesions including arthritis. The mechanical and biologic properties of synthetic polymers can be tailored to different clinical applications and engineering strategies. The scaffold serves as a mechanical substrate for cells and bioactive factors and can help direct and organize the process of regeneration. The ultimate goal of tissue engineering is to recapitulate normal organogenesis to create histologically and functionally normal tissue. A review of the characteristics and potential of synthetic polymers shows that these substances will play a major role in treating cartilage disorders.

Study Design: A case report of cervical myelopathy caused by ossification of the posterior longitudinal ligament in a patient with vitamin D-resistant rickets is presented together with a review of literature., Objective: To report the diagnosis of ossification of the posterior longitudinal ligament in a white woman with vitamin D-resistant rickets., Summary of Background Data: The association between ossification of the posterior longitudinal ligament and untreated vitamin D-resistant rickets has been reported in Japan, but infrequently in white populations. In whites, ossification of the posterior longitudinal ligament is closely associated with diffuse idiopathic skeletal hyperostosis. A clear association between ossification of the posterior longitudinal ligament and vitamin D-resistant rickets in white populations has not yet been established., Methods: The medical record and imaging studies of a patient treated at the authors' institution for cervical myelopathy caused by ossification of the posterior longitudinal ligament in the setting of treated vitamin D-resistant rickets were reviewed. A Medline search of the medical literature between 1966-1999 was performed to identify pertinent studies and similar case reports., Results: The occurrence of spinal stenosis in untreated adults with vitamin D-resistant rickets has been reported in all regions of the spine in Japanese patients. The association between ossification of the posterior longitudinal ligament and untreated vitamin D-resistant rickets was first reported in Japan, where ossification of the posterior longitudinal ligament is endemic. This association may be incidental, because reports on ossification of the posterior longitudinal ligament in whites are not as frequent as in Japanese, reflecting the higher prevalence of this condition in Japan., Conclusion: Ossification of the posterior longitudinal ligament and ossification of the posterior longitudinal ligament associated with deranged calcium or phosphate metabolism may be different pathologic entities sharing a common outcome. Adequate treatment of vitamin D-resistant rickets may not always prevent or reverse ossification of the posterior longitudinal ligament.

Study Design: Case report of surgically treated mechanical low back pain from the facet joint contralateral to a unilateral anomalous lumbosacral articulation (Bertolotti's syndrome)., Objectives: To describe the clinical presentation, diagnostic evaluation, and management of facet-related low back pain in a 17-year-old cheerleader and its successful surgical treatment with resection of a contralateral anomalous articulation., Summary of Background Data: Lumbosacral transitional vertebrae are common in the general population. Bertolotti's syndrome is mechanical low back pain associated with these transitional segments. Little is known about the pathophysiology and mechanics of these vertebral segments and their propensity to be pain generators. Treatment of this syndrome is controversial, and surgical intervention has been infrequently reported., Method: A retrospective chart analysis and radiographic review were performed., Results: Repeated fluoroscopically guided injections implicated a symptomatic L6-S1 facet joint contralateral to an anomalous lumbosacral articulation. Eventually, a successful surgical outcome was achieved with resection of the anomalous articulation., Conclusion: Clinicians should consider the possibility that mechanical low back pain may occur from a facet contralateral to a unilateral anomalous lumbosacral articulation, even in a young patient. Although reports of surgical treatment of Bertolotti's syndrome are infrequent, resection of the anomalous articulation provided excellent results in this patient, presumably because of reduced stresses on the symptomatic facet.

Many studies have shown a positive correlation among screw pullout strength, screw insertional torque, bone thickness, and areal bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. Variations are significant in the anatomy of the occipital bone. But no studies have correlated these variables with respect to the two locations commonly used for plate fixation to the occiput. The purpose of this study was to determine the thickness and quality of the occipital bone and to correlate these variables with the insertional torque of screws and the pullout strength of plates secured into two different locations on the occiput. The occiputs of 12 adult human fresh frozen cadaveric specimens were used. The specimens were analyzed by dual-energy X-ray absorptiometry. Direct thickness measurements of the occiput were performed. Areal and volumetric BMD were measured. A simple pelvic reconstruction plate (3.2 mm) was fixed to the occiput either laterally or at the midline with bicortical 4-mm cancellous screws. Torque was recorded at the time of insertion of each screw. Axial pullout tests were performed on all specimens. The peak load, failure load, stiffness, and energy to failure were recorded for each construct. Statistical analysis showed that the average thickness of occipital bone is greater in the midline than laterally. Occipital bone is thicker and screw torque is greater close to the inion. There is a positive correlation between bone thickness, areal BMD as measured by dual-energy X-ray absorptiometry, screw insertional torque, and strength of fixation. A plate fixed in the midline region of the occiput provides more rigid fixation than a plate fixed laterally. Areal BMD correlates better than volumetric BMD with bone thickness and is a reliable predictor of the strength of occipital fixation.

Human recombinant bone morphogenetic protein-2 (rhBMP-2) has been proven effective in stimulating the regeneration of bone in both skeletal and extraskeletal locations. Through encapsulation within, and release from, biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) microspheres, a proven vehicle for sustained delivery of various proteins, the local concentrations of rhBMP-2 could be maintained at optimal levels to stimulate bone regeneration and remodeling at the site of healing in diverse clinical settings. Thus the purpose of this work was to investigate the encapsulation of rhBMP-2 in PLGA microspheres and its biologic activity upon release. Using in vitro tests in simulated body fluids, the effect of rhBMP-2 released from PLGA microspheres upon osteoblast cell cultures was found to be statistically similar to the effect produced by positive controls consisting of nonencapsulated aqueous rhBMP-2 in simulated body fluids. This clarifies an important step in skeletal tissue engineering strategies aimed at the use of encapsulated rhBMP-2 to stimulate bone regeneration and remodeling.

Poly (Propylene Fumarate) (PPF), a novel, bulk erosion, biodegradable polymer, has been shown to have osteoconductive effects in vivo when used as a bone regeneration scaffold (Peter, S. J., Suggs, L. J., Yaszemski, M. J., Engel, P. S., and Mikos, A. J., 1999, J. Biomater. Sci. Polym. Ed., 10, pp. 363-373). The material properties of the polymer allow it to be injected into irregularly shaped voids in vivo and provide mechanical stability as well as function as a bone regeneration scaffold. We fabricated a series of biomaterial composites, comprised of varying quantities of PPF, NaCl and beta-tricalcium phosphate (beta-TCP), into the shape of right circular cylinders and tested the mechanical properties in four-point bending and compression. The mean modulus of elasticity in compression (Ec) was 1204.2 MPa (SD 32.2) and the mean modulus of elasticity in bending (Eb) was 1274.7 MPa (SD 125.7). All of the moduli were on the order of magnitude of trabecular bone. Changing the level of NaCl from 20 to 40 percent, by mass, did not decrease Ec and Eb significantly, but did decrease bending and compressive strength significantly. Increasing the beta-TCP from 0.25 g/g PPF to 0.5 g/g PPF increased all of the measured mechanical properties of PPF/NVP composites. These results indicate that this biodegradable polymer composite is an attractive candidate for use as a replacement scaffold for trabecular bone.

The patient was a 15-year-old girl who had a lesion of the fourth lumbar vertebra. Plain radiographs suggested vertebra plana, with complete collapse of the body of the fourth lumbar vertebra and no involvement of the intervertebral disk spaces. The presumptive diagnosis was eosinophilic granuloma. Progressive neurologic symptoms required surgical excision of the lesion, decompression, and fusion. Histopathologic examination of the operative specimen confirmed the diagnosis of an aneurysmal bone cyst.

Study Design: An in vitro biomechanical study., Objectives: To simulate a severe compressive flexion injury for determination of the relative stability of different anterior instrumentation systems in a porcine model and to validate this model in human cadaveric specimens., Summary of Background Data: Anterior plate fixation is useful for high-grade mechanical insufficiency of the cervical spine and may prevent the need for a second procedure., Methods: The cervical spines of 45 porcine and 12 cadaveric specimens were subjected to nondestructive flexion, lateral bending, and torsional testing on a modified universal testing machine. A corpectomy was performed with release of the posterior ligamentous structures. The specimens were stabilized with one of three anterior plate constructs. The nondestructive testing was repeated to evaluate structural stability (stiffness and neutral zone). Finally, destructive testing examined failure moment, energy to failure, and mechanism of failure., Results: The instrumented specimens had flexural and lateral bending and torsional stiffness values that were similar to or greater than those of their paired intact specimens. The cervical spine locking plate had a significantly higher flexural stiffness ratio (plated:intact), torsional stiffness ratio, lower flexural neutral zone ratio, higher failure moment, and higher energy to failure than did the Caspar plate., Conclusions: The cervical spine locking plate is theoretically safer than the Caspar system because the posterior vertebral body cortex is not breached by the fixation screws, and the screws are less likely to back out anteriorly and irritate the esophagus. According to these results, the cervical spine locking plate system is biomechanically equivalent to and in some cases more stable than the Caspar system for fixation of a severe compressive flexion injury.

Study Design: The clinical records, radiographs, histologic sections, and operative reports of 52 consecutive patients with an aneurysmal bone cyst of the spine were reviewed to evaluate diagnostic and therapeutic options and to correlate treatment and outcome., Objectives: To define the incidence, clinical presentation, diagnostic and therapeutic options, and prognosis of patients with aneurysmal bone cyst of the spine., Summary of Background Data: There are special considerations in the management of spinal lesions: relative inaccessibility of the lesions, associated intraoperative bleeding, necessity of removing the entire lesion to avoid the possibility of recurrence, proximity of the lesion to the spinal cord and nerve roots, and potential postoperative bony spinal instability., Methods: Fifty-two consecutive patients with an aneurysmal bone cyst of the spine were treated from 1910 to 1993. Forty patients initially treated for a primary lesion had operative treatment (19 intralesional excision and bone grafting and 21 intralesional excision); four also had adjuvant radiation therapy. Preoperative arterial embolization was performed in two., Results: There was a recurrence rate of 10% within 10 years. All recurrences were noted less than 6 months after surgery. Of 12 patients treated for a recurrent lesion, two had a subsequent recurrence (16.7%) within 9 years. At last follow-up examination, 50 patients (96%) were free of the disease. One patient died of postradiation osteosarcoma, and one died of intraoperative bleeding., Conclusion: Current treatment recommendations involve preoperative selective arterial embolization, intralesional excision curettage, bone grafting, and fusion of the affected area if instability is present.

Study Design: In vitro biomechanical investigation with nondestructive and destructive testing in a human cadaveric model simulating a wide postlaminectomy condition., Objectives: To determine the relative stability conferred by a posterior cervical spinal rod system and posterior cervical plating., Summary of Background Data: Posterior cervical plate fixation has been shown to be biomechanically superior to wiring techniques, but lateral mass screws may injure neurovascular structures or facet joints if they are inserted improperly. A cervical rod system has been developed to enhance the safety of lateral mass instrumentation., Methods: The cervical spines of 12 cadavers underwent biomechanical testing. After completion of the nondestructive intact testing, a wide laminectomy with subtotal facetectomies from C4 to C6 was performed. The specimens in two subgroups (group A, cervical spine rods with unicortical fixation, and group B, reconstruction plates with bicortical fixation) were tested in flexion, lateral bending, and torsion. Finally, destructive testing in flexion was performed. Stiffness, neutral zone, failure moment, energy to failure, and mechanism of failure were determined for each specimen. The data were analyzed using paired t tests and ANOVA., Results: Group B had a greater mean screw torque value. The instrumented constructs had a greater stiffness ratio (instrumented/intact) than the intact specimens in flexion, lateral bending, and torsional testing. Group A had a significantly greater flexural stiffness than Group B. Neutral zone ratio values were significantly lower during flexural testing for the cervical rod construct. Destructive testing resulted in significantly greater failure moment and energy-to-failure values for group A. In the cervical rod construct, failure occurred primarily by superior screw loosening with pull-out from the lateral mass. Reconstruction plates consistently failed with fracture of the lateral mass and superior screw loosening., Conclusion: Significantly greater stability was noted in the cervical rod construct during nondestructive and destructive flexural testing.

The use of a relatively new direct current (DC) electromagnetic tracking device in conjunction with a hostile metal environment of Material Testing Machine was studied. In this research, we first evaluated the reliability and performance of the DC tracking system operating in an ideal metal-free environment for both the translational and rotational error in static and dynamic conditions. When the tracking system with the same factory default configuration was moved into a heavy metal environment, serious translational and rotational distortion were observed. Through a series of evaluation of the physical environment and modification of the settings, the tracking system could perform satisfactorily and both the translational and angular error could be reduced in manufacturer's specifications. The safe working region for the DC tracking systems operating in a material testing machine environment was successfully mapped out. This study provides information for using the DC electromagnetic tracing device in the heavy metal environment exists in the material testing machine.

A testing system that applies a pure bending moment will uniformly load a spinal construct and be capable of identifying its weakest point. This study describes an apparatus for use with a material testing machine that is simple, inexpensive, and reliably creates a pure bending moment along the whole spine. We tested the system using two strain gauges attached to an aluminum alloy beam. First we verified the reliability and accuracy of the strain gauges system by comparing experimental measurement strain to theoretical prediction of strain in a cantilever beam model. The second experiment assessed the moment and strain created at two locations on a beam which was fixed at one end. The mean strain recorded from the two gauges demonstrated that moment is not uniformly distributed along the length of beam that is fixed at one end. The third experiment was similar to the second except that the beam was attached to an X-Y table instead of being fixed. Results demonstrated that a pure bending moment status is achieved when the end of the beam is fixed to an X-Y table.

The case of a 38-year-old man with delayed myelopathy 19 years after a nontreated odontoid type II fracture is reported. Magnetic resonance imaging of the craniocervical region revealed a periodontoid cicatrix. The clinical syndrome improved, and complete resolution of the retro-odontoid mass was achieved 9 months after posterior cervical fixation. The implications of this unique case for the management of myelopathy associated with nonunion of odontoid fractures are discussed.

Study Design: Radioactively labeled gentamicin was administered to 24 rabbits to assess the concentration of antibiotic in the nucleus pulposus., Objectives: The purpose of the study was to investigate the pharmacokinetics of gentamicin penetration into normal rabbit nucleus pulposus., Summary of Background Data: Disc space infection is a complication of spinal surgery that can be prevented by prophylactic antibiotics. Gentamicin can be used in conjunction with other antibiotics as a prophylactic agent. One previous study demonstrated that a similar antibiotic, tobramycin, penetrates the disc, but no data have been reported on the pharmacokinetics of disc penetration., Methods: Twenty-four rabbits were given an intravenous injection of gentamicin labeled with iodine 125. Four rabbits were killed at hourly intervals 1 to 6 hours after injection. Specimens of nucleus pulposus, blood, whole liver, and saline-perfused liver were obtained and prepared. The radioactivity in the specimens was measured., Results: The gentamicin concentration in the nucleus pulposus peaked at 2 hours and remained at this level for the duration of the experiment. Twenty percent of the gentamicin recovered from the nucleus pulposus was tissue bound., Conclusions: Gentamicin concentration in the rabbit nucleus pulposus does not peak until 2 hours after an intravenous bolus of drug. If gentamicin penetrates human nucleus pulposus in a similar fashion, this study could have implications for the timing of administration of this agent for prophylaxis.

Transthoracic discectomy and fusion were performed on 19 patients for a central or central-lateral herniated thoracic disc. At initial visit, 14 patients had evidence of myelopathy, 5 had bowel or bladder dysfunction, and 13 had pain. Previous laminectomy in three patients compromised the result of later anterior decompression. Coexistent multiple sclerosis was diagnosed in two patients, who had an atypical postoperative course. The overall results of transthoracic discectomy and fusion in patients without prior laminectomy or coexistent multiple sclerosis were excellent in six, good in six, fair in one, and poor in one, demonstrating that it is a safe and effective procedure.

A previously undescribed radiographic sign, the posterior vertebral body angle is successful in distinguishing subtle burst type fractures from compression fractures of the thoracolumbar spine. Correct diagnosis is imperative for proper treatment and accurate prognosis. When positive, this sign will alert the orthopaedist so that further diagnostic testing with computed tomography or sagittal tomograms may be performed. The sensitivity of this sign in diagnosing subtle burst type injuries is 75%.

Advances in imaging studies and techniques of spinal stabilization permit improved surgical treatment of patients with metastatic disease of the spine. Preoperative evaluation, selection of patients for operative management, and results of published clinical series are reviewed. Surgical approaches for optimal tumor excision, neural decompression, and spinal stabilization are discussed.