[Effect of femoral rotation on hip bone mineral density measurement].

OBJECTIVE

To measure hip bone mineral density (BMD) on different femoral rotations and to identify the influence of femoral rotation during hip densitometry.

METHODS

Forty women were recruited at the out-department of orthopedic, with the average age of 60.7 years (45-85 years), the average height of 161.8 cm (150-175 cm), and the average weight of 67.4 kg (48-80 kg). BMD measurement of hip was done in neutral position (0 degrees), 15 degrees and 30 degrees of internal rotation under quality control of DXA machine. All the subjects were asked to get down scan table and reposition after each measuring in different rotation.

RESULTS

Hip BMD of proximal femur (femoral neck, Ward's area and trochanter region) have significant variations in measurement (P < 0.01) among neutral position, 15 degrees and 30 degrees of internal rotation. There were more BMD change at the cancellous region (Ward's triangle and trochanter region) than at cortical bone area (femoral neck region). Statistical analysis showed a significant positive correlation for hip BMD change between neutral degrees to 15 degrees of internal rotation and 15 degrees to 30 degrees of internal rotation. But no correlation between neutral degrees to 30 degrees of internal rotation for hip BMD change.

CONCLUSIONS

Femoral rotation was shown to have a significant effect on hip BMD measurements. Cortical bone region of hip have a less BMD change than cancellous bone region. Proper positioning of the femur during scan can improve precision significantly.