The distribution of bone mineral density in the femoral heads of unstable intertrochanteric fractures.

PURPOSE: Intertrochanteric fractures are usually treated with open reduction and internal fixation, but controversy still remains regarding the proper placement of the lag screw on the anteroposterior view. The stability of the lag screw has been shown to correlate with the bone quality around the screw, but the three-dimensional distribution of the bone mineral density (BMD) in the femoral head has not been studied in detail. Herein, the BMD along the femoral neck axis was measured to clarify the recommended position of the lag screw.

METHODS

Ten femoral heads acquired from intertrochanteric fractures were evaluated in this study. Each femoral head was scanned with micro computed tomography and the BMD along the femoral neck axis was measured in five regions: center, anterior, posterior, superior, and inferior. The BMD on the anteroposterior view (superior, center, and inferior) and the BMD on the lateral view (anterior, center, and posterior) were compared.

RESULTS

The BMD of the center region (173.0 ± 50.6 mg/cm3) was significantly higher than that of the inferior region (139.7 ± 50.1 mg/cm3) on the anteroposterior view ( p < 0.01). On the lateral view, the BMD was lower than the center region in the anterior region (165.7 ± 52.8 mg/cm3) and in the posterior region (157.5 ± 42.3 mg/cm3), but the difference was not significant.

CONCLUSION

The BMD was higher in the center region of the femoral head than in the inferior region. Therefore, lag screws are recommended to be inserted into the center of the femoral head.