Opportunistic osteoporosis screening in intraoperative CT can accurately identify patients with low volumetric bone mineral density and osteoporosis during spine surgery.

Purpose: To evaluate the accuracy of opportunistic measurements of volumetric bone mineral density (vBMD) in intraoperative multi-detector CT (MDCT) scans, using preoperative MDCT as the reference.

Methods: This retrospective, single-center study included 105 patients (mean age: 73 ± 12.6 years, 53 women) who underwent spine surgery for various indications. All patients had preoperative MDCT with/without intravenous contrast and unenhanced intraoperative scans. VBMD of thoracolumbar vertebrae was automatically extracted using a convolutional neural network (CNN)-based framework with asynchronous calibration and contrast-phase correction. Vertebrae affected by artifacts, fractures, or severe degenerations were excluded. Root-mean-square errors (RMSEs) for associations between pair-wise vertebrae from preoperative and intraoperative vBMD values were calculated in linear regression models. Mean bias and 95%-limits of agreement (LOA) were calculated in Bland-Altman plots.

Results: Strong associations between preoperative and intraoperative vBMD values were observed in the thoracic (R = 0.94) and lumbar spine (R = 0.96). Intraoperative vBMD values showed high accuracy in reference to preoperative measurements with a mean bias of -1.3 mg/cm for the thoracic spine (LOA: -18.7 to 16.1 mg/cm) and - 3.0 mg/cm for the lumbar spine (LOA: -17.4 to 11.3 mg/cm). RMSEs between preoperative and intraoperative vBMD values slightly increased for contrast-enhanced scans (RMSE: 8.42 vs. 10.1 mg/cm; RMSE: 7.75 vs. 8.87 mg/cm).

Conclusion: Opportunistic osteoporosis screening with the presented approach is feasible and demonstrates high accuracy in reference to preoperative MDCT scans. This could enable the identification of patients with low bone mass during surgery, allowing surgeons to take measures (e.g., adapted techniques) that prevent postoperative complications and improve patient outcomes.