Multimodal Imaging Predictors of FEA-Derived Lumbar Vertebral Compression Strength

Retrospective cross-sectional study.

To identify multimodal imaging predictors of lumbar vertebral compression strength (CS), focusing on volumetric bone mineral density (vBMD), vertebral bone quality (VBQ), abdominal aortic calcification (AAC), and multifidus fatty infiltration (FI), and to evaluate the cumulative and incremental predictive value of these routinely available imaging and patient-level factors for FEA-derived CS.

Preoperative assessment of vertebral strength is essential in spine surgery. While quantitative CT (QCT)-derived vBMD and MRI-based VBQ have been proposed as surrogate markers of bone integrity, their relative predictive value for biomechanical failure remains unclear. Paraspinal muscle FI has been associated with poorer functional and postoperative outcomes, yet its contribution to vertebral CS is underexamined.

A retrospective analysis of 76 patients undergoing lumbar fusion with preoperative CT and MRI (2014-2020) was performed. Vertebral CS at L1 was calculated using CT-based finite element analysis (FEA). vBMD at L1-L2 was measured using asynchronous QCT. VBQL1/2 was derived from T1-weighted MRI normalized to cerebrospinal fluid. Multifidus FI was quantified at L4 on axial T2-weighted MRI. AAC was graded on lateral lumbar radiographs. Spearman correlation and multivariable linear regression were used to identify CS predictors.

Higher vBMD was associated with greater CS across all models (β=64.7-67.3 N per mg/cm³; all P <0.001). Neither VBQL1/2 nor AAC showed independent associations with CS or improved model performance. Multifidus FI showed a positive but non-significant association with CS (β=51.3 N per % increase; P=0.078), representing a trend, and its inclusion modestly increased overall model fit (adjusted R²=0.781). Sex remained a significant predictor in all models (P <0.001).

vBMD was the only imaging biomarker reliably predicting vertebral CS, underscoring its central role in preoperative bone quality assessment. VBQ, AAC, and multifidus FI, did not independently predict CS. Although multifidus FI was not statistically significant, its modest improvement of model performance suggests a potential secondary contribution to vertebral biomechanics. CT-based evaluation remains essential for identifying patients at risk of vertebral fragility.