High prevalence of borderline hip dysplasia in young patients with femoral head subchondral stress fractures.

BACKGROUND

Limited research exists on young patients with femoral head subchondral stress fractures (SSF), especially regarding how hip anatomy may contribute to this condition. Few studies have explored the potential correlation between its pathogenesis and developmental dysplasia of the hip (DDH). We aimed to determine hip morphology in patients with femoral head SSF and analyze the distribution of various parameters reflecting hip coverage and stability.

MATERIALS AND METHODS

Radiographic data of all patients with femoral head SSF who met the inclusion criteria between January 2019 and November 2023 were retrospectively reviewed. These data included the lateral center-edge angle (LCEA), Tönnis angle, anterior center-edge angle (ACEA), femoral head extrusion index, acetabular arc, femoral head lateralization, upsloping lateral sourcil, cliff sign, crossover sign, posterior wall sign, and ischial spine sign. We determined the proportion of borderline DDH (BDDH) and the distribution of each parameter on the affected side. Additionally, we compared differences between patients with LCEA < 25° and LCEA > 25°.

RESULTS

In affected hips, 15 cases (57.7%) had BDDH, 3 cases (11.5%) had DDH, and only 8 cases (30.8%) had a normal LCEA. On the contralateral side, 8 cases (30.8%) had BDDH, 4 cases (15.4%) had DDH, and 14 cases (53.8%) had normal LCEA. Abnormalities were prominent in the extrusion index (50.0%), acetabular arc (65.4%), femoral head lateralization (46.2%), cliff sign (42.3%), and posterior wall sign (65.4%). Among patients with affected-side LCEA < 25°, more than 50% exhibited abnormalities in ACEA, extrusion index, acetabular arc, cliff sign, or posterior wall sign. Among patients with normal LCEA on the affected side, most had acetabular retroversion, with 75.0% showing a positive crossover sign and 75.0% showing a positive ischial spine sign.

CONCLUSIONS

This study revealed a notably high prevalence of BDDH in young patients with femoral head SSF. The various abnormalities observed in parameters reflecting coverage and stability in BDDH may explain the potential association between BDDH and femoral head SSF.

LEVEL OF EVIDENCE IV

Retrospective case series.