[Trabecular bone density measurement in Hounsfield units in the proximal femur for osteoporosis assessment and fracture risk determination].

Background: Osteoporosis leads to fractures, especially in older patients after minor trauma. Hip fractures are frequent.

Research question: The study investigated whether bone mineral density (BMD) and T‑scores can be calculated based on trabecular density in Hounsfield units (HU) in the proximal femur, and whether the presence of osteoporosis and fracture risk can be assessed.

Patients and methods: 370 patients (Ø 69.4 years, 53 men/317 women) were examined using CTXA hip (DEXA equivalent). In addition, HU measurements were taken in the CT cross-section of the caput femoris and proximal femur. Fractures were recorded using supplementary imaging.

Results: Trabecular bone density decreased significantly with increasing age and decreasing BMI. There was a strong correlation between HU values and BMD (R² = 0.88) as well as T‑score (R² = 0.89). A threshold value of 96 HU showed high predictive power for osteoporosis (AUC = 0.97) for the proximal femur region, for the femoral head, the threshold value was 245.5 HU. The fracture threshold value was 245.5 HU for the femoral head and 75 HU for the proximal femur.

Discussion: HU measurement in native CT cross-sectional images allows a reliable assessment of osteoporosis and fracture risk. Opportunistic HU evaluation alone is, therefore, practicable and sufficient.