Validation of Hounsfield units for preoperative bone mineral density assessment in intertrochanteric femoral fractures.

Abstract

Background: Hounsfield units (HU) on computed tomography (CT) are strongly correlated with bone mineral density (BMD) and may aid in osteoporosis screening. However, there is no standardized method for assessing bone density in displaced femoral head fractures. This study aimed to measure HU values in the femoral head using preoperative post-fracture CT images of patients with intertrochanteric femoral fractures and investigate whether it correlated with BMD measured by dual-energy X-ray absorptiometry (DXA).

Materials and methods: We retrospectively analyzed post-fracture CT images of intertrochanteric fractures (n = 52). Hounsfield units were measured in the axial, coronal, and sagittal planes using the femoral neck axis as a reference. Severe osteoporosis was defined as <60 % of the young adult mean (YAM) (T-score <-3.3). We evaluated the correlations between HU and DXA-derived BMD, along with reliability (intraclass correlation coefficient [ICC]), measurement bias (Bland-Altman analysis), and diagnostic performance (receiver operating characteristic [ROC]).

Results: HU values demonstrated strong associations with BMD across all planes, with the highest correlations observed in the axial and coronal planes. ICC values exceeded 0.9, indicating excellent reliability. Bland-Altman analysis revealed no proportional bias but a fixed bias in the sagittal plane, whereas the narrowest limits of agreement were observed in the axial plane. Based on the ROC analysis, an axial HU cutoff of 151.5 identified severe osteoporosis (sensitivity, 0.756; specificity, 0.783).

Conclusions: Axial HU measurements were most reliable for assessing the bone quality. This cutoff value may help identify severe osteoporosis and determine eligibility for cement augmentation. However, further validation is needed.