Spinal cord injury models: a review.

BACKGROUND: Animal spinal cord injury (SCI) models have proved invaluable in better understanding the mechanisms involved in traumatic SCI and evaluating the effectiveness of experimental therapeutic interventions. Over the past 25 years, substantial gains have been made in developing consistent, reproducible and reliable animal SCI models. STUDY DESIGN: Review. OBJECTIVE: The objective of this review was to consolidate current knowledge on SCI models and introduce newer paradigms that are currently being developed. RESULTS: SCI models are categorized based on the mechanism of injury into contusion, compression, distraction, dislocation, transection or chemical models. Contusion devices inflict a transient, acute injury to the spinal cord using a weight-drop technique, electromagnetic impactor or air pressure. Compression devices compress the cord at specific force and duration to cause SCI. Distraction SCI devices inflict graded injury by controlled stretching of the cord. Mechanical displacement of the vertebrae is utilized to produce dislocation-type SCI. Surgical transection of the cord, partial or complete, is particularly useful in regenerative medicine. Finally, chemically induced SCI replicates select components of the secondary injury cascade. Although rodents remain the most commonly used species and are best suited for preliminary SCI studies, large animal and nonhuman primate experiments better approximate human SCI. CONCLUSION: All SCI models aim to replicate SCI in humans as closely as possible. Given the recent improvements in commonly used models and development of newer paradigms, much progress is anticipated in the coming years.

Spinal infections. Diagnosis and treatment.

Spinal infections encompass a broad spectrum of pathology. Any element of the spine, the vertebrae, disks, surrounding soft tissues, potential spaces, or the cord itself may be involved solely, or more commonly, in combination. Staphylococcus aureus is the organism most frequently found, with Gram negative bacteria often cited in association with infections of the urinary tract and in intravenous drug abusers. Early diagnosis and treatment are essential for optimal outcomes. In some cases, the only necessary treatment consists of parenteral antibiotics and immobilization. However, certain instances require operative intervention. The goals of treatment for any infection of the spine are: early diagnosis with identification of the offending organism, preservation of neurological function or cessation of progressive neurologic deficit, and complete eradication of the infection with a pain-free, stable spine.

Use of epidural steroids after discectomy may predispose to infection.

STUDY DESIGN: This is a report of three cases of epidural abscess occurring after use of intraoperative epidural methylprednisolone in 31 patients who had undergone lumbar microdiscectomy. The possible role of epidural steroids in the cause of these abscesses is discussed, and a review the literature concerning its value is provided. OBJECTIVE: To evaluate experiences with the efficacy and safety of perioperative methylprednisolone. SUMMARY OF BACKGROUND DATA: No previous study has described a high infection rate with the use of epidural methylprednisolone. The literature supporting epidural steroids is equivocal, and reports supporting their perioperative use are scant. METHODS: In an 8-month period, 31 patients received 1 mL (40 mg) epidural methylprednisolone at the conclusion of microdiscectomy. Therapy was discontinued after an increased postoperative deep infection rate was noted. Results in these patients were compared with those in more than 400 others who did not receive intraoperative steroids during a 7-year period. RESULTS: In the steroid group, three epidural abscesses were encountered. There were no deep infections in the nonsteroid group. CONCLUSION: The use of perioperative epidural methylprednisolone in the currently reported cases was associated with three incidences of infection. A prospective study is needed to examine its use.

Contemporary management of spinal osteomyelitis.

OBJECTIVE: We review the results of treatment of a series of patients with spinal osteomyelitis, to formulate a systematic and comprehensive approach to the management of this disease in light of recent technical and conceptual advances in imaging, spinal biomechanics, and internal fixation. METHODS: We retrospectively reviewed the records for 57 consecutive patients with pyogenic spinal osteomyelitis who were treated between June 1987 and June 1995. Pain and weakness were the most common presenting symptoms. The mean duration of symptoms at the time of diagnosis was 10.6 weeks. Surgical indications included the presence or development of motor deficits with epidural compression and/or localized kyphotic deformities or the failure of medical therapy. RESULTS: Thirty-three patients underwent surgery as their initial treatment. Six additional patients experienced medical therapy failure and received subsequent surgical treatment. Seventeen patients were treated using an anterior approach only, 13 were treated using a posterior approach only, and 9 were treated using a combined anterior and posterior approach. After a minimal follow-up period of 24 months, 93% of the surgically treated patients showed neurological improvement or were neurologically intact, with a mean 16-degree decrease in localized kyphotic deformities and with solid bony fusion and resolution of pain for all patients. CONCLUSION: Early surgical decompression results in rapid improvement of neurological deficits, decreases in kyphotic deformities, and stabilization with bony fusion. The presence of active infection does not preclude the use of internal fixation. Nonsurgical management is indicated for patients with minimal or no neurological deficits and the absence of significant localized kyphotic deformities. However, 25% of patients who were initially treated nonsurgically experienced medical therapy failure and underwent surgical treatment.

Microdiskectomy for lumbar disk herniation: a review of 100 cases.

One hundred patients who underwent microlumbar diskectomy over 5 years were retrospectively reviewed. L4-5 and L5-S1 were compared to determine whether a patient's post-surgical outcome is related to the level where a herniation has occurred. Overall results included 70 excellent, 19 good, 2 fair, and 9 poor. Statistical analysis showed that neither the level involved, length of follow-up, nor degree of manual labor predicted outcome. Older patients and females tended to fare worse, but the trends were not significant. Three recurrent herniations occurred, 1 in the L4-L5 group and 2 in the L5-S1 group. No variable predicted recurrence.

Open discectomy as treatment for herniated nucleus pulposus of the lumbar spine.

Open discectomy is the "gold standard" for operative intervention in patients with herniated lumbar discs whose conservative treatment has failed. Over 60 years the indications for surgery and the expected success rates have been clearly elucidated. The specific patient selection and determination of surgical procedures continues to evolve. Recurrent herniations occur at a low rate, and serious complications are rare.

Modern management of spinal tuberculosis.

The resurgence of pulmonary tuberculosis in the United States has been paralleled by a concomitant rise in tuberculosis of the spine (Pott's disease). The appearance of drug-resistant strains of tuberculosis, infection in large numbers of immunocompromised hosts, newer imaging modalities, and the development of more effective spinal reconstruction techniques have raised important issues regarding the management of Pott's disease. In spite of this, there has been little published recently on the modern management of Pott's disease in developed countries. We report our experience with the management of 20 patients with Pott's disease in the past 5 years, 16 of whom were admitted during the last 18 months of this retrospective study. The mean patient age was 49 years. Sixteen (80%) were men. Nineteen (95%) had a positive tuberculin skin test, and 13 (65%) had pulmonary tuberculosis. Symptoms consisted of spinal pain, weakness, sensory complaints, and flank mass in order of decreasing frequency. Ten patients were neurologically intact; the remainder had motor deficits of variable severity. The thoracic spine was involved in 13 patients, the lumbar spine was involved in 4, the cervical spine was involved in 2, and the thoracolumbar spine was involved in 1. Spinal deformity was present in 11 patients, spinal epidural compression was present in 13, and a paraspinal mass was present in 18. Operative indications included motor deficits, spinal deformity, nondiagnostic computer tomographic-guided needle biopsy, and noncompliance with, or lack of, response to medical therapy. Eleven patients underwent operations. Six patients had vertebrectomy and bone grafting with posterior instrumentation when indicated; three had laminectomy, debridement, and abscess drainage; one had laminectomy and posterior instrumentation; and one had paraspinal abscess drainage. Two patients have died; the remainder have been monitored for at least 1 year and are neurologically improved or normal without residual infection. The average angulation decreased from 31 to 24 degrees by the follow-up examination. In selected patients, early operative treatment with instrumentation, when indicated, minimizes neurological deterioration and spinal deformity, allows early ambulation, and results in excellent neurological outcome.

Posterior plates in the management of cervical instability: long-term results in 44 patients.

Although posterior plates are increasingly used to manage cervical spinal instability, long-term follow-up evaluation of patients with a critical analysis of efficacy and complications has not been reported. The authors have retrospectively analyzed the outcome in 44 consecutive patients (37 males and seven females, age range 16 to 80 years) treated with posterior cervical plates. The indications for instrumentation were instability due to trauma in 42 cases, tumor in one, and infection in one. In four patients the follow-up period was limited to 3, 5, 11, and 16 months. Two patients died of chronic medical problems 4 and 9 months after treatment. The remaining 38 patients were followed from 2 to 6 years (mean 46 months). One motion segment was stabilized in 23 patients using two-hole plates; two motion segments were stabilized in the other 21 patients using three-hole plates. In the majority of patients (37 cases), supplemental bone grafting was not used. Patients were immobilized postoperatively in a Philadelphia collar. Solid arthrodesis was achieved in 39 (93%) of 42 patients. Three patients required revision of the cervical plating: in one patient with a C-5 burst fracture, two-hole plates were applied at C5-6 and progressive kyphosis mandated anterior fusion; the second patient required posterior wiring due to screw pull-out resulting from a technical error in screw insertion; the third patient, who refused to wear an orthosis postoperatively, also developed screw pull-out. In two patients who went on to spinal fusion, there was an increase in sagittal kyphosis (6 degrees and 8 degrees) without clinical sequelae. Screw loosening was noted in five patients, involving eight (3.8%) of the 210 lateral mass screws; this complication resulted in instrumentation failure or increased kyphosis in three cases. There were two superficial infections. This analysis indicates that posterior cervical plating is highly effective; at long-term follow-up review the cervical spine was successfully stabilized in 93% of cases. Plate failure was related to faulty screw placement, failure to include sufficient motion segments, and noncompliance with postoperative orthoses. Halo vest immobilization was unnecessary and supplemental bone grafting was generally not required for recent trauma.

A new method of thoracic and lumbar body replacement for spinal tumors: technical note.

Anterior decompressive procedures have gained more widespread usage in the treatment of anterior compressive lesions of the spinal cord due to neoplasms. Alternative methods of vertebral body replacement that use a modified silastic tube placed into adjacent vertebral segments and filled with methyl methacrylate cement are described. The technique is reserved for patients with limited longevity as the result of the malignant nature of their disease process.

A systematic approach to spinal reconstruction after anterior decompression for neoplastic disease of the thoracic and lumbar spine.

The anterior approach to the thoracic and lumbar spine for neoplastic disease is now a well-accepted procedure, with results, for the most part, superior to those achieved with laminectomy. However, the specific indications for anterior decompression and the selection of reconstruction techniques based on the location and extent of bony destruction have received surprisingly little attention. The authors report their experience with the operative management of 33 patients with benign and malignant tumors of the thoracic and lumbar spine, using the anterior transthoracic or retroperitoneal approach. The role of stabilization and the relative indications for anterior or posterior instrumentation are emphasized. The mean age of patients was 58 years. Twenty-three patients were male. Five patients had benign tumors, and the remainder had a variety of metastatic lesions. Twenty-nine patients had lower extremity motor deficits, although 25 were ambulatory preoperatively. Thirty-seven noncontiguous resections were performed in 33 patients. In 13 patients, the resected vertebral body was replaced with acrylic or bone without instrumentation; in 18, the acrylic was supplemented with anterior instrumentation; and in 6, both anterior and posterior instrumentation were used. Above T11, vertebral reconstruction techniques were used to restore stability after decompression. Between T11 and L4, anterior instrumentation was used to supplement vertebral reconstruction in all patients. Supplemental posterior instrumentation was used for three-column involvement. Motor function was stabilized or improved in 94% of patients, and 88% of patients were ambulatory postoperatively. Of 28 patients with malignant disease, 23 died after a mean survival of 10.2 months (range, 2-51 mo) and 5 are alive a mean of 34.4 months since their operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Luque instrumentation in degenerative conditions of the lumbar spine.

The authors report on the experience obtained in using L-rods and sublaminar wires in obtaining lower lumbar fusions of three or more levels in degenerative diseases of the lumbar spine. A successful fusion was obtained in 86% of the patients. The technique, while offering a satisfactory method of fusion, does violate the spinal canal with sublaminar wires with potential for neurologic injury. Specifically, the passage of sacral wires should be avoided.

Spinal stabilization of vertebral column tumors.

An analysis of indications, techniques, results of stabilization and decompression of 100 consecutive spinal tumour cases was carried out. Localized metastatic disease is best operated anteriorly. Primary malignancies are best treated with en bloc resection. Pain relief in metastatic disease is achieved by rigid stabilization. The unstable spine secondary to benign or malignant disease often requires stabilization for alleviation of pain; 132 stabilization procedures were performed in 100 patients. There were nine benign and 91 malignant tumors including 71 metastatic. Indications for stabilization were pathological fracture or following decompression. Anterior approaches including implant stabilization were used in those with metastatic disease limited to one to two levels or where significant kyphosis existed. Posterolateral decompression with Luque rod stabilization was indicated where disease was more widespread. In metastatic disease acrylic cement was used both anteriorly and posteriorly together with implant stabilization. Eighty-one percent had good to excellent relief of pain; 68 patients had neurological deficits. Significant neurological return was achieved in 40% of posterior decompressions and 71% of anterior decompressions in metastatic disease. All patients with benign tumors have solid fusions. In malignant disease the use of cement provided stability without loss of fixation in 87 of 91 procedures. Complications were 4% infection and failure of two Harrington rods without wiring, one Luque rod and two anterior constructs. The average longevity of patients treated for metastatic disease was 11.3 months.

Evaluation and diagnosis of cervical spine injuries: a review of the literature.

Cervical spine injuries pose devastating potential problems for surgeon and patient alike. This review will stress the early diagnosis of cervical spine injuries, with emphasis on early suspicion of injury. This review will focus on the radiology and types of lesions found with cervical spine injury.

Techniques of internal fixation for degenerative conditions of the lumbar spine.

The indications and techniques for internal fixation of the lumbar spine in degenerative conditions have changed drastically since internal fixation was first applied to the spine almost 100 years ago. Anterior instrumentation and fusion may be used for repair of pseudarthrosis after posterolateral fusion; symptomatic lumbar scoliosis associated with degenerative disc disease; late pain secondary to posttraumatic kyphosis; postlaminectomy instability; and lumbar pain secondary to thoracolumbar kyphosis. Posterior instrumentation and fusion has been performed with Luque instrumentation over 3-4 levels in cases of multilevel instability. Combined anterior and posterior instrumentation and fusion are required for lumbosacral fusion in lumbar scoliosis with degenerative disease, and surgical correction of postsurgical lumbar kyphosis (flat-back syndrome). The techniques are demanding but with attention to detail can be performed with acceptably low-complication rates.

Heterotopic ossification. Incidence and relation to trochanteric osteotomy in 100 total hip arthroplasties.

Heterotopic ossification can impair the functional results of total hip arthroplasty. The causative role of trochanteric osteotomy in heterotopic ossification is uncertain. Postoperative radiographs of 100 total hip arthroplasties were analyzed for incidence of heterotopic ossification. Forty procedures were performed with trochanteric osteotomy and 60 without. There was a 17% overall incidence of clinically significant heterotopic ossification, 22% with osteotomy and 13% without. High- and low-risk categories revealed clinically significant heterotopic ossification in 25% of the high-risk group and in 8% of the low-risk group. In the high-risk group there was a 32% incidence with trochanteric osteotomy and 22% without osteotomy. In the low-risk group there was a 16% incidence without trochanteric osteotomy and a 3% incidence with trochanteric osteotomy. The increase in clinically significant heterotopic ossification in the high-risk group over that of the low-risk group was statistically significant. The present study showed that trochanteric osteotomy tended to increase the incidence and severity of clinically significant heterotopic ossification. These data suggest that trochanteric osteotomy should be avoided, if possible, during total hip arthroplasty to decrease the risk of heterotopic ossification.