Bone Material Strength Index as Measured by Impact Microindentation is Low in Patients with Primary Hyperparathyroidism

Abstract

Context: In primary hyperparathyroidism (PHPT) bone mineral density (BMD) is typically decreased in cortical bone and relatively preserved in trabecular bone. An increased fracture rate is observed however not only at peripheral sites but also at the spine, and fractures occur at higher BMD values than expected. We hypothesized that components of bone quality other than BMD are affected in PHPT as well. Objective: To evaluate bone material properties using impact microindentation (IMI) in PHPT patients. Methods: In this cross-sectional study, the Bone Material Strength index (BMSi) was measured by IMI at the midshaft of the tibia in 37 patients with PHPT (28 women), 11 of whom had prevalent fragility fractures, and 37 euparathyroid controls (28 women) matched for age, gender, and fragility fracture status. Results: Mean age of PHPT patients and controls was 61.8±13.3 and 61.0±11.8 years, respectively, P=.77. Calcium and PTH levels were significantly higher in PHPT patients but BMD at the lumbar spine (0.92±0.15 vs 0.89±0.11, P=.37) and the femoral neck (0.70±0.11 vs 0.67±0.07, P=.15) were comparable between groups. BMSi however was significantly lower in PHPT patients than in controls (78.2±5.7 vs 82.8±4.5, P