A three-dimensional analysis of fovea morphology in normal and diseased hips

The fovea capitis anchors the ligamentum teres on the femoral head. In normal hips, it resides within the acetabular fossa. However, clinical observations suggest that its position and morphology vary in pathological hips, potentially contributing to joint degeneration through fossa-foveolar mismatch (FFM). Understanding the fovea's morphology is essential to clarifying its role in hip pathomechanics. We asked: (i) what is the proportion of the femoral head occupied by the fovea; (ii) what is the position of the fovea relative to the acetabular fossa; and (iii) what is the FFM index in a defined neutral position for different pathological and normal hips. Using three-dimensional models from computed tomography scans, we analysed 183 hips with femoroacetabular impingement or dysplasia and 22 with normal morphology. Using a standardized medial view of the fovea through the fossa, we determined: (i) the proportion of the fovea surface area on the femoral head; (ii) the positioning of the fovea relative to the fossa; and (iii) FFM indices in all study groups. (i) In normal hips, the fovea accounted for a median of 7% of the femoral head surface. (ii) While the fovea was positioned centrally in normal hips, dysplastic hips demonstrated an anterosuperior displacement of the fovea. (iii) Dysplastic hips had the highest FFM indices (median 0.13; P < .001). This study highlights variations in foveal morphology across different hip pathomorphologies. Foveal size was generally consistent. Foveal position differed markedly, with dysplastic hips showing anterosuperior displacement and the highest FFM indices. These results suggest that altered foveal morphology may contribute to pathological contact and degenerative lesions.