DXA-Based Bone Strain Index: A New Tool to Evaluate Bone Quality in Primary Hyperparathyroidism

Context Primary hyperparathyroidism (PHPT) is associated with impaired bone quality and increased fracture risk. Reliable tools for the evaluation of bone quality parameters are not yet clinically available. Bone Strain Index (BSI) is a new metric for bone strength based on Finite Element Analysis from lumbar spine and femoral neck dual-energy x-ray absorptiometry (DXA) images. Objective To assess the lumbar spine (LS), femoral neck (FN), and total hip (TH) BSI in PHPT patients compared with controls and to investigate the association of BSI with vertebral fractures (VFs) in PHPT. Methods This case-control study enrolled 50 PHPT patients and 100 age- and sex-matched control subjects from an outpatient clinic. The main outcome measures were LS-BSI, FN-BSI, and TH-BSI. Results FN bone mineral density (BMD) and one-third distal radius BMD were lower in the PHPT group than in controls (FN 0.633 +/- 0.112 vs 0.666 +/- 0.081, P = 0.042; radius 0.566 +/- 0.07 vs 0.625 +/- 0.06, P < 0.001). PHPT group has significant lower TBS score compared with controls (1.24 +/- 0.09 vs 1.30 +/- 0.10, P < 0.001). BSI was significantly higher at LS (2.28 +/- 0.59 vs 2.02 +/- 0.43, P = 0.009), FN (1.72 +/- 0.41 vs 1.49 +/- 0.35, P = 0.001), and TH (1.51 +/- 0.33 vs 1.36 +/- 0.25, P = 0.002) in PHPT. LS-BSI showed moderate accuracy for discriminating VFs (AUC 0.667; 95% CI, 0.513-0.820). LS-BSI >= 2.2 and was a statistically significant independent predictor of VFs, with an adjusted odds ratio ranging from 5.7 to 15.1. Conclusion BSI, a DXA-derived bone quality index, is impaired in PHPT and may help to identify PHPT subjects at high risk of fractures.

Automated summary

Primary hyperparathyroidism (PHPT) is associated with impaired bone quality and increased fracture risk. The Bone Strain Index (BSI) derived from DXA images showed significant differences in PHPT patients compared with controls, and may help identify those at high risk for fractures.