Impact of Incident Osteoporotic Vertebral Fractures on 5-Year Postoperative Outcomes and Spinal Alignment Following Lumbar Fusion Surgery.

Introduction: Osteoporotic vertebral fractures (OVFs) are a significant problem among older patients who are undergoing spine surgery. This study examined the influence of incident OVFs on clinical outcomes and spinal alignment 5 years following short-segment fusion (SSF) for lumbar spinal stenosis. Methods: We studied 88 patients who underwent SSF (≤2-disc level) for lumbar spinal stenosis with instability and were followed up for more than 5 years postoperatively. Those with prior OVFs were excluded. We evaluated incident OVFs with plain whole-spine lateral radiography preoperatively (before) and at 5 years postoperatively (after). Using preoperative lumbar computed tomography, Hounsfield unit (HU) values were evaluated. The patients were classified into two groups according to the presence of incident OVFs. Repeated-measures analysis of variance was utilized to compare the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and the 36-item Short-Form Health Survey (SF-36), and spinal parameters were recorded before and after. Multiple linear regression analyses were employed to investigate the association between the incident OVFs and the clinical scores and spinal alignment recorded after. Results: In the fracture group, the clinical course of low back pain score on the JOABPEQ, physical component summary SF-36 score, and spinal alignment including C7 sagittal vertical axis (SVA), thoracic kyphosis (TK), and pelvic tilt were significantly worse. Multiple linear regression revealed a significant correlation between incident OVFs and worse 5-year postoperative spinal alignment, which includes SVA and TK. The optimal threshold for the HU values for predicting the incidence of OVFs within 5 years postoperatively was 83.0 (area under the curve 0.701). Conclusions: Incident OVFs in patients following SSF were significantly correlated with the 5-year clinical outcomes and spinal alignment. Patients at risk of OVFs, especially those with HU values below 83, must take preventive measures against OVFs, as this could prevent deteriorating midterm postoperative clinical outcomes and spinal alignment. Level of Evidence: 3.