Incidence and Risk Factors of Sacral Fracture following Lumbosacral Fusion for Degenerative Spinal Stenosis with a Minimum Follow-up of 2 years: A Case-Control Study.

BACKGROUND This study aimed to investigate the incidence and risk factors for sacral fractures following lumbosacral fusion. METHODS We conducted a retrospective review of patients who underwent lumbosacral fusion for degenerative spinal stenosis with a minimum follow-up of 2 years. Patients who developed and those who did not develop a sacral fracture were categorized into the "sacral fracture" and "non-fracture" groups. The demographic and radiological data were compared between the two groups. RESULTS A total of 65 patients were included in this study. Among them, seven patients were categorized into the sacral fracture and 58 patients into the non-fracture groups, respectively. The incidence of sacral fracture was 10.8%. In the sacral fracture group, age and fusion levels were significantly higher (P < 0.05), while bone mineral density (BMD) T-score was significantly lower (P < 0.05) than non-fracture group. PI, preoperative PT, postoperative SS, and postoperative LL were significantly higher (P < 0.05) in the sacral fracture than the non-fracture group. Multivariable logistic regression analysis showed that BMD T-score (Odds ratio [OR] 0.25, 95% confidence interval [CI] 0.08-0.79, P = 0.019), postoperative SS (OR 1.14, 95% CI 1.00-1.29, P = 0.047), and changes in L4-S1 lordosis (OR 1.11, 95% CI 1.00-1.23, P = 0.049) were significant factors. CONCLUSIONS The overall incidence of sacral fracture was 10.8%. In our study, advanced age, low BMD, long fusion levels, and preoperative compensatory pelvic retroversion and excessive correction of it were risk factors for sacral fractures.