Postoperative Spinal Subdural Lesions Following Lumbar Spine Surgery: Prevalence and Risk Factors

STUDY DESIGN: Retrospective case–control study PURPOSE: To clarify the prevalence and risk factors for spinal subdural lesions (SSDLs) following lumbar spine surgery. OVERVIEW OF LITERATURE: Because SSDLs, including arachnoid cyst and subdural hematoma, that develop following spinal surgery are seldom symptomatic and require reoperation, there are few reports on these pathologies. No study has addressed the prevalence and risk factors for SSDLs following lumbar spine surgery. METHODS: We conducted a retrospective analysis of the magnetic resonance (MR) images and medical records of 410 patients who underwent lumbar decompression surgery with or without instrumented fusion for degenerative disorders. SSDLs were classified into three grades: grade 0, no obvious lesion; grade 1, cystic lesion; and grade 2, lesions other than a cyst. Grading was based on the examination of preoperative and postoperative MR images. The prevalence of SSDLs per grade was calculated and risk factors were evaluated using multivariate logistic regression analysis. RESULTS: Postoperative SSDLs were identified in 123 patients (30.0%), with 50 (12.2%) and 73 (17.8%) patients being classified with grade 1 and 2 SSDLs, respectively. Among these, one patient was symptomatic, requiring hematoma evacuation because of the development of incomplete paraplegia. Bilateral partial laminectomy was a significantly independent risk factor for SSDLs (odds ratio, 1.52; 95% confidence interval, 1.20–1.92; p<0.001). In contrast, a unilateral partial laminectomy was a protective factor (odds ratio, 0.11; 95% confidence interval, 0.03–0.46; p=0.002). CONCLUSIONS: The prevalence rate of grade 1 SSDLs was 30%, with no associated clinical symptoms observed in all but one patient. Bilateral partial laminectomy increases the risk for SSDLs, whereas unilateral partial laminectomy is a protective factor.

Major Surgical Treatment of Osteoporotic Vertebral Fractures in the Elderly: A Comparison of Anterior Spinal Fusion, Anterior-Posterior Combined Surgery and Posterior Closing Wedge Osteotomy

STUDY DESIGN: A retrospective study. PURPOSE: To clarify the differences among the three major surgeries for osteoporotic vertebral fractures based on the clinical and radiological results. OVERVIEW OF LITERATURE: Minimally invasive surgery like balloon kyphoplasty has been used to treat osteoporotic vertebral fractures, but major surgery is necessary for severely impaired patients. However, there are controversies on the surgical procedures. METHODS: The clinical and radiographic results of patients who underwent major surgery for osteoporotic vertebral fracture were retrospectively compared, among anterior spinal fusion (group A, 9 patients), single-stage combined anterior-posterior procedure (group AP, 8 patients) and posterior closing wedge osteotomy (group P, 9 patients). Patients who underwent revision surgery were evaluated just before the revision surgery, and the other patients were evaluated at the final follow-up examination, which was defined as the end point of the evaluations for the comparison. RESULTS: The operation time was significantly longer in group AP than in the other two groups. The postoperative correction of kyphosis was significantly greater in group P than in group A. Although the differences were not significant, better outcomes were obtained in group P in: back pain relief at the end point; ambulatory ability at the end point; and average loss of correction. CONCLUSIONS: The posterior closing wedge osteotomy demonstrated better surgical results than the anterior spinal fusion procedure and the single-stage combined anterior-posterior procedure.