Evidence for impaired skeletal load adaptation among Canadian women with type 2 diabetes mellitus: insight into the BMD and bone fragility paradox.

OBJECTIVE: Recent data suggest that women with type 2 diabetes mellitus (T2DM) might be more susceptible to fractures due to an impaired adaptive response to mechanical load, despite reportedly higher bone mineral density (BMD). The purpose of this study was to use an engineering beam analysis to calculate and compare the load stresses on the femurs of healthy women and women with T2DM and compare these levels to conventional measures of femoral neck BMD. MATERIALS/
METHODS: We studied 3658 women who participated in the Canadian Multicentre Osteoporosis Study (CaMos), and who had available Hip Structure Analysis (HSA) data from baseline dual energy x-ray absorptiometry (DXA) scans. Women were categorized into two groups based on the presence or absence of self-reported T2DM. We computed stress in megapascals (MPa) at the infero-medial margin of the femoral neck in a one-legged stance using an engineering beam analysis incorporating dimensions and geometry from DXA scans using the HSA method. We used linear regression (SAS 9.3) to determine the association between T2DM status and stress. We also determined the association between T2DM status and femoral neck BMD.
RESULTS: Stresses were 4.5% higher in T2DM women than in non-diabetics (11.03±0.18 vs. 10.56±0.04 MPa; p=0.0093). Femoral neck BMD was 4.2% greater in women with T2DM than in non-diabetics (0.74±0.002 vs. 0.71±0.01 g/cm(2); p=0.0008).
CONCLUSIONS: Despite higher femoral neck BMD, higher stress indicates weaker skeletal geometry for a given load, and suggests an impaired skeletal adaptive response to load may be present in women with T2DM.