Standardisation of the neck-shaft angle and measurement of age-, gender- and BMI-related changes in the femoral neck using DXA.

INTRODUCTION: The morphology of the proximal femur has often been investigated in the literature, but the normal population ranges and standard deviations have still not been determined for this area. This study aimed to determine the age-, gender- and body mass index (BMI)-related changes in the femoral neck, especially on the neck-shaft angle, by using dual-energy X-ray absorptiometry (DXA) measurements. METHODS: Retrospective analyses of DXA images of the proximal femur from 18,943 individuals aged 20-108 years were performed. The age, gender, weight and height of each individual were obtained at the time of bone measurement. Data on theta angle were obtained from DXA measurements. Simple linear regression analysis and Pearson's correlation coefficients were used to investigate the relationships between theta and age, gender and BMI. RESULTS: There was a significant correlation between theta and age (p < 0.001). We also found a significant difference between the various age groups using analysis of variance (p < 0.001), but there was no meaningful correlation between theta and BMI (p = 0.377) and the BMI groups (p = 0.180). There were small but statistically significant differences in the neck-shaft angle between males and females (p < 0.05). CONCLUSION: In this study, DXA-based measurements were used and many parameters of proximal femur geometry were calculated with limited radiation exposure. We have demonstrated that the mean neck-shaft angle is greater in males than in females, and that theta increases with age. We also found a significant difference between different age groups, but no meaningful correlation between theta and BMI.