Evaluation of hip angles with magnetic resonance imaging in early stage femoral head osteonecrosis

Aims: It was aimed to evaluate the alpha and Wiberg angles of patients with clinical and radiological diagnosis of idiopathic femoral head osteonecrosis (FHO) in comparison with the control group. Methods: Routine hip MRI (Magnetic resonance imaging) s between January 2022 and May 2024 were examined retrospectively. MRI images diagnosed with early stage (Stage I, II according to Ficat and Arlet classification), idiopathic femoral head osteonecrosis were recorded. A control group matched in age and gender was created. Alpha angle was measured as the angle between the parallel line drawn from the center of the femoral head to the femoral neck in axial MRIs and the line drawn from the transition point between the femoral head and neck in the anterior to the center of the femoral head. Wiberg's central corner angle was measured as the angle between the perpendicular line drawn from the center of the femoral head to the acetabulum and the line connecting the outermost point of the acetabulum in coronal images. Measurements were compared statistically in both groups. P<0.05 was considered statistically significant. Results: A total of 70 hips were examined, including 35 FHO (13 unilateral and 11 bilateral hips) and 35 control groups (3 unilateral and 16 bilateral hips). There was no difference between the groups in terms of age and gender (P>0.05). We found statistically significant differences in alpha and Wiberg angles between the FHO and control groups (P=0.04, P=0.025, respectively). There was no statistically significant difference between stages I and II in terms of alpha and Wiberg angles (P= 0.376, P= 0.078, respectively). Conclusion: These changes in hip angle measurements in this study may explain the cause of idiopathic FHO. We can predict femoral head osteonecrosis early.