Quantitative assessment of bone mineral density in cervical spine surgery: Diagnostic accuracy of C2 and C3 Hounsfield units versus cervical vertebral bone quality scores.

BACKGROUND

Preoperative bone mineral density (BMD) assessment is essential for cervical spine surgery, yet dual-energy X-ray absorptiometry (DXA) is not routinely performed. Opportunistic imaging metrics such as computed tomography-derived Hounsfield units (HU) and magnetic resonance imaging-based vertebral bone quality (VBQ) scores have been proposed as surrogates, but their comparative diagnostic value in the cervical spine remains unclear.

METHODS

In this retrospective single-center study, 154 patients aged ≥50 years undergoing cervical spine surgery for degenerative diseases were included. All patients underwent cervical CT, cervical MRI, DXA, and bone turnover marker testing within 3 months preoperatively. HU values at C2-C7 were measured on sagittal CT images, and VBQ scores were calculated from T1-weighted MRI. Correlations between imaging parameters and DXA T-scores (lumbar spine, femoral neck, and total hip) were analyzed. Receiver operating characteristic analysis evaluated diagnostic performance for reduced BMD (T-score <-1.0), including sex-specific subgroups.

RESULTS

Mean cervical HU values decreased progressively from C4 to C7 and were significantly lower in patients with reduced BMD (all p < .001). C2 HU showed the strongest correlations with DXA T-scores (r = 0.528-0.671). C2 and C3 HU demonstrated numerically higher discriminative ability for identifying reduced BMD (area under the curve [AUC] = 0.737 and 0.741) compared with VBQ (AUC = 0.638) and Goutallier grade (AUC = 0.623). Performance of C2 HU was consistent across sexes. HU values showed weak correlations with β-cross-linked telopeptide of type I collagen and osteocalcin and no association with 25-hydroxyvitamin D or procollagen type I N-terminal propeptide.

CONCLUSIONS

Upper cervical HU measurements, particularly at C2 and C3, demonstrated favorable discriminative performance for identifying reduced BMD and may serve as a practical opportunistic screening tool in patients undergoing cervical spine surgery.