Relationship between site-specific bone mineral density in the proximal femur and instability of proximal femoral fractures: A retrospective study.

BACKGROUND: Proximal femoral fractures can occur in patients with osteoporosis. However, the relationship between bone mineral density (BMD) of the proximal femur and fracture type and instability remains unclear. This study aimed to determine whether there is a relationship between the site-specific BMD of the proximal femur and the instability of proximal femoral fracture. HYPOTHESIS: The instability of proximal femoral fractures is related to the site-specific BMD of the proximal femur. PATIENTS AND METHODS: Using dual-energy X-ray absorptiometry (DEXA), the BMD on the non-fractured side was retrospectively examined in 252 women who underwent surgery for proximal femoral fracture at our hospital. The BMD was measured at three sites: the femoral neck (neck), trochanter (trochanter), and intertrochanteric region (inter). The BMD at several sites was compared between the femoral neck and trochanteric fractures. Femoral neck fractures were classified into the displaced and non-displaced types, and trochanteric fractures were classified into stable and unstable types. A comparative analysis was conducted for each proximal femur site and fracture type. RESULTS: Both total and site-specific BMDs were lower in trochanteric fractures than in femoral neck fractures. No difference was observed between BMD and displaced or non-displaced femoral neck fractures. However, the BMD of the intertrochanteric region was lower in unstable trochanteric fractures (0.57±0.12g/cm2) than in stable trochanteric fractures (0.61±0.11g/cm2) [p<0.05]. DISCUSSION: Several factors, including the patient's age and the bone component of each region, may influence the lower BMD in trochanteric fractures. In trochanteric fractures, the site-specific BMD of the proximal femur may predict the type of fracture and the degree of instability, especially in those with low BMD at the intertrochanteric site. The study findings suggest that a decrease in the BMD of the intertrochanteric region of femoral trochanteric fractures, which is thought to be involved in instability, is associated with fracture type instability. LEVEL OF EVIDENCE: III, retrospective study.