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Association of bone mineral density with reoperation rate following instrumented lumbar spinal fusion: a retrospective cohort and case-control study


 Background Low bone mineral density (BMD) is believed to influence the outcome of instrumented spinal surgery and can lead to reoperation. Purpose of this retrospective cohort and case-control study was to investigate the association of BMD with the risk of reoperation following instrumented lumbar spinal fusion (LSF). Methods For the cohort analysis, 81 patients were included who received LSF with and without polymethyl methacrylate (PMMA)-augmentation. For the case-control analysis, 18 patients who had reoperation following LSF were matched to 26 patients who did not have reoperation (matching criteria: sex, age ± 5 years, fused levels, and augmentation). Opportunistic BMD screening was performed in perioperative CT scans using asynchronous calibration. Mean BMD was compared between patients with and without reoperation in augmented and non-augmented surgeries. Results In the cohort analysis, prevalence of osteoporosis (BMD < 80 mg/cm³) was 29% in non-augmented and 85% in augmented LSF. Seven of 48 patients with non-augmented (15%) and 4 of 33 patients with augmented LSF (12%) had reoperation. In non-augmented LSF, patients with reoperation had significantly lower BMD than patients without reoperation (p = 0.005). In the case-control analysis, patients with reoperation presented numerically lower BMD of 78.8 ± 33.1 mg/cm³ than patients without reoperation with BMD of 89.4 ± 39.7 mg/cm³ (p = 0.357).Conclusions Prevalence of osteoporosis in patients undergoing LSF is relatively high. Patients with reoperation following LSF showed slightly lower BMD compared to matched patients without reoperation, but the difference was not statistically significant. Opportunistic BMD screening in preoperative CT is feasible and can provide valuable information about osteoporotic bone status.