Impact of bone density on distal radius fracture patterns and comparison between five different fracture classifications.

OBJECTIVE: To investigate the impact of bone mineral density (BMD) and bone geometry on failure loads and fracture patterns of the distal radius and to compare 5 different fracture classifications.

DESIGN: Biomechanical and radiologic in vitro study.

SETTING: Research laboratory.

MAIN OUTCOME MEASUREMENTS: A total of 118 intact human forearms from elderly donors were examined by means of conventional radiography and peripheral quantitative computed tomography (PQCT) to determine BMD and geometry. The forearms were subjected to a standardized biomechanical test simulating a fall on the outstretched hand. The distal radius fractures were classified from x-rays using the AO ( 33), Cooney ( 9), Fernandez ( 15), Frykman ( 17), and Melone ( 31) classifications. The grading was repeated after preparation and direct visual inspection of the fracture site and was correlated with radiographic results. Fracture patterns also were correlated with BMD and geometry.

RESULTS: Correlations between bone properties and fracture patterns (r = 0.09-0.70) suggested an increase in the severity of fractures with decreasing bone quality. The highest correlation between failure load and bone properties was found for the cortical area (r = 0.70) and trabecular density (r = 0.60). Good correlations between radiographic and direct visual classification were obtained for the Cooney ( 9) (r = 0.70), the AO ( 33) (r = 0.68), and the Fernandez ( 15) (r = 0.65) classifications. Smaller values were found for the Frykman ( 17) (r = 0.44) and the Melone ( 31) (r = 0.27) classifications.

CONCLUSIONS: With increasing osteopenia, the load to failure decreases, and the severity of fractures increases. Fracture patterns in this patient population can be adequately graded with the AO ( 33) and Cooney ( 9) classifications. The severity of distal radius fractures tends to be underestimated by conventional x-ray examination, which needs to be taken into account when a fracture treatment plan is selected.