Does hip bone morphology differ depending on the presence of cam lesions in borderline developmental dysplasia of the hip?

Background: The purpose of this study was to divide patients with borderline developmental dysplasia of the hip (BDDH) into two groups according to the presence of Cam lesions, and compare radiographs related to bone morphology between them. Methods: We retrospectively analyzed consecutive patients with BDDH who underwent hip arthroscopy (HA) or periacetabular osteotomy (PAO) at our institution between October 2013 and October 2019. The patients were classified into two groups according to the presence of Cam lesions. Radiographic measurements including lateral center-edge angle (LCEA), acetabular roof obliquity (ARO), cliff sign, femoral epiphyseal acetabular roof (FEAR) index, vertical center anterior angle (VCA), and Sourcil Index were compared between the two groups. The cutoff values were calculated using a receiver operating characteristic curve. Results: Sixty-nine hips were analyzed in this study (Cam+: 34, Cam-: 35). The ARO and FEAR index were significantly higher in the Cam-group (P < 0.001, P < 0.001). The LCEA, VCA, and Sourcil Index was significantly lower in the Cam-group than that in the Cam + group (P < 0.001, P < 0.001, P < 0.001). The cutoff values were 21.0° for LCEA, 15.1° for the ARO, 22.5° for the VCA angle, -2.2° for the FEAR index, and 49.5° for the Sourcil Index. Conclusion: Patients with BDDH exhibited significant differences in bone morphology depending on the presence of Cam lesions. Moreover, those without Cam lesions displayed similarities to patients with DDH.