Single-rod versus dual-rod anterior instrumentation for idiopathic scoliosis: a biomechanical study

STUDY DESIGN

Anterior single- and dual-rod instrumented human and ovine thoracolumbar spines, with and without structural interbody support (SIS), were biomechanically tested and compared in flexion, lateral bending, and torsion.

OBJECTIVE

To determine significant differences in global stiffness of the constructs in an attempt to clarify specific indications for each in the treatment of spinal deformities.

SUMMARY OF BACKGROUND DATA

Single- and dual-rod anterior systems have been used without any consensus as to indications for one versus the other. The potential added benefit of incorporating SIS and transverse connectors (dual-rod) with these constructs has also not been fully explored.

METHODS

Four human cadaveric and six ovine spines were instrumented in single- and dual-rod constructs and biomechanically tested intact, postdiscectomy with and without SIS, with single- and dual-rod constructs, and with and without transverse connectors (ovine only). Biomechanical testing modes were flexion, lateral bending, and torsion.

RESULTS

In the human cadaveric specimens, testing in flexion revealed that SIS was the major contributing factor for construct stiffness. In lateral bending, stiffness of single- and dual-rod constructs with and without SIS was equivalent. In torsion, both single- and dual-rod instrumentation and SIS appeared to contribute to global stiffness. In ovine specimens, dual rods were stiffer than single-rod constructs and SIS played only a minor role. Transverse connectors appeared to significantly stiffen dual-rod constructs in torsion only.

CONCLUSIONS

Dual-rod constructs with SIS appear to be the best combination for providing stiffness in anterior instrumentation. The addition of cross-links to anterior constructs does not appear to increase stiffness except in torsion.

Chiari I malformation associated with syringomyelia and scoliosis: a twenty-year review of surgical and nonsurgical treatment in a pediatric population

STUDY DESIGN

Retrospective review of patients with Chiari I malformation with or without associated scoliosis.

OBJECTIVES

Determine the effect of decompression of Chiari I malformation with syringomyelia on stabilization or improvement of associated scoliosis.

SUMMARY OF BACKGROUND DATA

Chiari malformations are often associated with spinal deformities, including scoliosis. Studies have suggested a causal relation between syringomyelia and scoliosis.

METHODS

Patients with Chiari I malformation and syringomyelia with or without scoliosis treated over the last 20 years were reviewed. Patients with any other anomalies were excluded. Scoliotic curves were classified by magnitude and curve type. All patients were treated with surgical decompression of the Chiari malformation with or without drainage of the syringomyelia.

RESULTS

Twenty-five patients were identified, ranging in age from 19 months to 16.5 years. Nineteen patients (76%) had associated scoliosis. The majority of the patients with scoliosis (13 of 19) sought treatment for spinal deformity, and only 6 had for pain or neurologic symptoms. Eleven of 19 patients with scoliosis (58%) underwent fusion. Eight of 19 (42%) patients have not undergone fusion: 3 have experienced progress, 1 remains in a stable condition, and 4 have experienced improvement of curvature since undergoing decompression. The mean age of patients who experienced progress after decompression was 14.5 years, compared to 6 years for patients who experienced improvement.

CONCLUSION

Early decompression of Chiari I malformation with syringomyelia and scoliosis resulted in improvement or stabilization of the spinal deformity in 5 cases. Each of these patients underwent decompression before 8 years of age and before the curve was severe. However, this series represents a few patients demonstrating this trend, and further follow-up and investigation are warranted.

Histologic characterization of acute spinal cord injury treated with intravenous methylprednisolone

OBJECTIVE

Many substances have been investigated for attenuation of spinal cord injury after acute trauma; however, pharmacologically only steroid administration has shown clinical benefits. This study attempts to characterize local spinal cord histologic response to human dose equivalent (HDE) intravenous methylprednisolone (MP) administration in a rodent model of acute spinal cord injury.

DESIGN

Forty-eight Sprague-Dawley rats were divided equally into control and experimental groups. Each group was subdivided into eight sets of three animals each, according to postinjury intervals. Paraplegia after lower thoracic laminectomy was achieved using a standardized weight drop technique.

INTERVENTION

Within one hour, experimental animals were treated with HDE MP followed by 23-hour continuous infusion of HDE MP. Spinal cords were harvested at variable intervals postinjury and prepared for histologic/immunohistochemistry examination.

MAIN OUTCOME MEASUREMENTS

Edema, necrosis, and glial fibrillary acidic protein (GFAP) positivity in the specimens from treated/control groups were graded by microscopy and immunohistochemistry staining and compared in a blinded manner by a qualified neuropathologist and senior authors.

RESULTS

Minimal differences were observed between control and MP-treated animals at zero and four hours. At eight hours, increased white matter and medullary edema was evident in control versus MP-treated rats. This trend continued through twelve, sixteen, twenty-four, forty-eight, and seventy-two hours. No difference was observed in the astrocytic response to injury by GFAP immunohistochemistry between the groups.

CONCLUSIONS

Histologically, MP reduces the development of severe edema and preserves spinal cord architecture adjacent to the site of injury. In contrast, MP does not alter the development of spinal cord necrosis or astrocytic response at the zone of injury.

Bilateral partial laminectomy: a treatment for lumbar spinal stenosis and midline disc herniation

BACKGROUND

Lower back pain is extremely common; most patients' symptoms improve with conservative treatment. This leaves only a small percentage of patients with persistent symptoms that are amenable to surgery. Various decompressions have been performed to remedy compressive conditions of the spine, with a wide range of results.

METHODS

We retrospectively reviewed 152 patients with lumbar spinal stenosis or midline disc herniations surgically treated with bilateral partial laminectomy. Short-term follow-up was available for 138 patients (2 weeks to 2 months) and long-term follow-up was available for 88 patients (1-6 years, mean 3.5 years). Clinical outcome was determined by chart review and the use of a standardized questionnaire. Preoperative and postoperative back and leg pain, ambulation, employment status, and satisfaction were assessed.

RESULTS

Overall improvement postoperatively was noted in 88% of the spinal stenosis patients and 91% of the midline disc herniations at long-term follow-up. Average hospital stays for the spinal stenosis group and the midline disc herniation group were 3.7 days and 2.8 days, respectively. Only two patients had undergone subsequent fusions of their lumbar spine after bilateral partial laminectomy.

CONCLUSION

We believe that less radical resection of laminae and spinous processes better preserves the spine's natural architecture and may contribute to improved postoperative stability. This may reduce the number of patients needing concomitant or subsequent fusion, with its associated morbidity. As surgeons push for less radical or less invasive surgical techniques to obtain the same or better postoperative results, the bilateral partial laminectomy is a good alternative to total laminectomy.

Systemic chemotherapy combined with local adoptive immunotherapy cures rats bearing 9L gliosarcoma

Survival of Fischer rats bearing 9L gliosarcoma in the brain was measured to determine the efficacy of 1) systemically administered chemotherapy with local adoptive immunotherapy (chemo-adoptive immunotherapy) or 2) systemically administered chemo-immunotherapy. Winn assays, where tumor instillation coincided with the start of treatment, and one-week established tumor assays were conducted. Survival of chemo-adoptive immunotherapy treated groups given intraperitoneal cyclophosphamide and intracranial lymphokine activated killer cells and recombinant Interleukin-2 was significantly extended when compared to sham treated control groups, to groups given chemotherapy with intraperitoneal cyclophosphamide, and to groups treated by local adoptive immunotherapy with intracranial lymphokine activated killer cells and Interleukin-2. The killer cells were generated from spleens of donor rats that either had or had not been given cyclophosphamide 24 h earlier. Long-term survivors (9/39), sacrificed at day 70, were obtained only in the chemo-adoptive immunotherapy treated groups; 7/39 had no histologic evidence of tumor and had focal sterile abscesses at the site of killer cell instillation. Average group weight plotted over time showed that there was acceptable toxicity with chemo-adoptive immunotherapy; the toxicity was identical to that obtained with systemic cyclophosphamide treatment. In contrast, survival of chemo-immunotherapy treated groups given systemic cyclophosphamide and Interleukin-2 was not significantly extended from groups which were sham treated or treated only with systemic Interleukin-2. Rapid decline of average group weight plotted over time and early deaths following chemo-immunotherapy treatment indicated that the regimen was toxic. The effect of cyclophosphamide administration on the splenocytes of donor rats and the LAK cells generated from them was determined by in vitro studies analyzing cell number, viability, phenotypic expression and cytotoxicity against 9L tumor. In the treatment of this intracranial neoplasm, the beneficial effects of cyclophosphamide were determined to occur in situ in the tumor-bearing host. No benefit resulted from cyclophosphamide treatment of donor rats that supplied splenocytes for LAK cell production.