Correlation between distal radial cortical thickness and bone mineral density.

PURPOSE: To determine interobserver reliability in measuring the cortical thickness of distal radiuses on posteroanterior radiographs obtained at the time of injury and to determine whether there is a correlation between distal radius cortical thickness and hip and lumbar spine scores on dual-energy x-ray absorptiometry (DXA).

METHODS

Four orthopedic surgeons at 2 academic institutions who were blinded to the study protocol reviewed standard posteroanterior wrist radiographs of 80 women over age 50 years with distal radius fractures with DXA data obtained within the past 2 years. Radial bicortical widths were measured at 50 and 70 mm proximal to the distal ulnar articular surface, and mean bicortical thickness was calculated from radiographs of the injured wrist. Average bicortical width was compared with each patient's femoral and lumbar spine bone density measures. Data were analyzed using Pearson correlation coefficients and simple linear regression. Inter-rater reliability was evaluated using intra-class correlation coefficients.

RESULTS

The inter-rater reliability for average bicortical thickness had a high intra-class correlation coefficient value of 0.91. Average bicortical thickness showed a statistically significant positive relationship with femoral bone density. Average bicortical thickness was statistically correlated with femoral bone density values, with a 1-mm increase in average bicortical thickness associated with a 0.05 g/cm(2)-increase in femoral density. Average bicortical thickness was not associated with lumbar bone density.

CONCLUSIONS

Bicortical thickness of the distal radius was positively correlated with femoral bone density but not with lumbar spine density. This may reflect similarity in quality and loading properties of the femur and radius as appendicular bones, compared with the axial spine. Identification of thinned distal radial cortices in association with distal radius fracture is a simple qualitative observation that should prompt further evaluation with DXA and medical management of bone insufficiency.

TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.