Study Design. Matched case-control study. Objective. To identify factors other than a multilevel procedure that increase the risk of symptomatic postoperative spinal epidural hematoma (SEH). Summary of Background Data. Postoperative SEH is a potentially devastating complication of spinal surgery. Previous studies that reported risk factors for postoperative SEH all identified a multilevel procedure as a risk factor, but the other risk factors remain unclear. Methods. Patients who developed postoperative SEH requiring surgical evacuation were identified from database. Each patient was matched with 3 controls who underwent spinal decompression at the same number of levels in the same part of the spine by the same surgeon during the preceding or following year. Multiple logistic regression analysis was performed to identify the risk factors for postoperative SEH to obtain adjusted odds ratios with 95% confidence intervals. Clinical outcomes after evacuation were investigated separately divided with or without severe paralysis or time until the second surgery. Results. Postoperative SEH evacuation was performed after 32 of 8250 (0.39%) spinal decompression procedures. The incidence was significantly higher after thoracic procedures (2.41%) than after cervical (0.21%) or lumbar (0.39%) procedures. Multivariate analysis identified a 50 mm Hg or greater increase in systolic blood pressure after extubation (adjusted odds ratio: 3.22, 95% confidence interval: 1.22–8.51) and higher body mass index (adjusted odds ratio 1.15, 95% confidence interval: 1.01–1.31) as risk factors. Among 14 patients with severe paralysis due to postoperative SEH, those who underwent evacuation within 24 hours of the onset had a significantly better improvement in clinical outcome and Frankel grade than did those after 24 hours. Conclusion. A 50 mm Hg or greater increase in systolic blood pressure after extubation and high body mass index were identified as risk factors for SEH. Appropriate blood pressure control especially at the end of surgery is important for the prevention of postoperative SEH, particularly in obese patients. Level of Evidence: 3

Lumbar spinal stenosis (LSS) is one of the most frequent causes of low back pain and gait disturbance in the elderly. Ligamentum flavum (LF) hypertrophy is the main pathomechanism of LSS, but the reason for its occurrence is not clearly elucidated. In this study, we established a novel animal model of intervertebral mechanical stress concentration and investigated the biological property of the LF. The LF with mechanical stress concentration showed degeneration with elastic fibres disruption and cartilage matrix increase, which are similar to the findings in hypertrophied LF from patients with LSS. By contrast, decreased Col2a1 expression was found in the LF at fixed levels, in which mechanical stress was strongly reduced. These findings indicate that mechanical stress plays a crucial role in LF hypertrophy through cartilage matrix increase. The findings also suggest that fusion surgery, which eliminates intervertebral instability, may change the property of the LF and lead to the relief of patients’ symptoms.

Study DesignRetrospective cohort study.PurposeThe purpose of this study was to evaluate the prevalence of diffuse idiopathic skeletal hyperostosis (DISH) in patients with spinal diseases determined by roentgen images of the whole spine.Overview of LiteratureAlthough several studies have investigated the prevalence of DISH in healthy subjects, no detailed data have been reported on the prevalence of DISH in patients with degenerative spinal disorders.MethodsStanding whole-spine roentgen images of 345 consecutive patients who underwent surgery in our hospital were obtained. Patients aged <18 years or with congenital spinal disease, metastatic spinal tumors, or inflammatory spinal disease were excluded. In total, 281 patients were eligible for inclusion. The presence of DISH was assessed according to Resnick's criteria and Mata's scoring system. The prevalence, location, and numbers of fused vertebral bodies of DISH were recorded.ResultsDISH was present in 25.6% of patients (72/281). The prevalence of DISH in the 41–49, 50–59, 60–69, 70–79, and ≥80 year age groups was 8.3% (2/24), 9.8% (5/51), 16.0% (12/75), 49.5% (48/97), and 33.3% (4/12), respectively; the prevalence increased with age. The average number of fused vertebral bodies was 7.5. More than 80% of DISH was located from T7 to T11, and more than 95% of DISH was located at T9/10. Patients with DISH were significantly older (71.1 years vs. 60.9 years, p<0.05), and men were more likely to have DISH than women (p<0.05).ConclusionsIn patients with degenerative spinal diseases with DISH, fused vertebrae were found most frequently in the lower thoracic spine, and their prevalence increased with age. DISH may be an age-related skeletal disorder with a higher overall prevalence in patients with spinal disorders than that in healthy subjects.