Regional distribution of cancellous bone density in the femoral head using CT Hounsfield unit values.

BACKGROUND

Subchondral insufficiency fracture of the femoral head predominantly affects elderly women and commonly occurs in the anterosuperior region. Although regional variations in bone density may contribute to its characteristic location, the distribution of cancellous bone density within the radiographically normal femoral head remains unclear. This study quantified regional cancellous bone density using computed tomography-derived Hounsfield unit values and investigated its associations with patient characteristics.

METHODS

Computed tomography images of 94 femoral heads were analyzed. Hounsfield unit values were measured in 27 predefined regions, and their associations with age, sex, body mass index, and acetabular coverage were evaluated. Age- and sex-related differences were assessed.

RESULTS

The superomedial region showed the highest Hounsfield unit values, whereas the superolateral region had significantly lower values in all coronal slices (all P < 0.01). Age and body mass index were broadly associated with regional Hounsfield unit values throughout the femoral head, whereas sex and lateral acetabular coverage were associated with values in the lateral region of the anterior femoral head. Anterior acetabular coverage was positively correlated with the anterior superolateral Hounsfield unit value. Among participants aged ≥40 years, women had lower values in the superolateral and mediolateral regions of the anterior and central slices, and female sex remained independently associated with a lower anterior superolateral Hounsfield unit value.

CONCLUSIONS

Computed tomography-derived Hounsfield unit values demonstrated distinct regional variations in cancellous bone density within the femoral head. Age-related bone loss was more pronounced peripherally, whereas sex- and acetabular coverage-related associations were predominantly observed in the anterior lateral region. These findings suggest that factors associated with lower cancellous bone density may converge in the anterior superolateral region, providing insight into the characteristic location of subchondral insufficiency fracture.