Purpose: Potential associations between radiographic parameters and the incidence of symptomatic postoperative spinal epidural hematoma (PSEH) have not been identified. This study aimed to identify risk factors including radiographic parameters for symptomatic PSEH after posterior decompression surgery for lumbar spinal canal stenosis (LSS). Methods: We retrospectively reviewed 1007 consecutive patients who underwent lumbar decompression surgery for lumbar spinal canal stenosis (LSS) at our institution. We identified 35 cases of symptomatic PSEH, defined by clinical symptoms and MRI findings, and selected 3 or 4 age- and sex-matched control subjects for each PSEH subject (124 controls). We compared radiographic parameters and previously reported risk factors between PSEH and control subjects. Results: Compared to the control group, PSEH patients had significantly higher preoperative systolic (p =.020) and diastolic (p =.048) blood pressure, and more levels of decompression (p =.001). PSEH and control subjects had significant differences in lumbar lordosis (PSEH 24.8° ± 14.6°, control 34.8° ± 14.5°), pelvic tilt (25.1° ± 11.7° vs. 20.8° ± 8.4°), sacral slope (23.4° ± 9.4° vs. 27.6° ± 8.3°), and pelvic incidence minus lumbar lordosis (23.7° ± 15.0° vs. 13.7° ± 14.6°). Multivariate analysis revealed two significant risk factors for PSEH: decompression of two or more levels and lumbar lordosis < 25°. Conclusions: Multilevel decompression and hypolordosis are significant risk factors for symptomatic PSEH after decompression surgery for LSS. LSS patients with lumbar hypolordosis or multilevel stenosis should be carefully observed for PSEH after decompression surgery. Graphical abstract: These slides can be retrieved under Electronic Supplementary Material.[Figure not available: see fulltext.].
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