Purposes: The aim of this study was to describe and compare the femoral morphologies of Hartofilakidis types C1 and C2 developmental dysplasia of the hip (DDH), and discuss the potential influence on subsequent total hip arthroplasty (THA).
Methods: We analyzed preoperative CT data from 81 patients (42 C1 and 39 C2 subtypes) who underwent THA for arthritis secondary to Hartofilakidis type C DDH. The CT data was three-dimensionally reconstructed and measured of following parameters: neck-shaft angle, femoral neck length, anteversion, medial inclination, femoral offset, height of the greater trochanter and femoral head, mediolateral (ML) and anteroposterior (AP) widths of the medullary canal. The canal flare indices and ML-to-AP ratio were further calculated. We also reviewed surgical and follow-up records to compare the different implants utilized and the clinical results between C1 and C2 hips.
Results: The C2 femurs had a significantly lower neck-shaft angle (119.0° vs. 124.0°), shorter femoral neck (37.0 mm vs. 41.2 mm), larger medial cortical inclination (158.8° vs. 149.1°), and higher position of the greater trochanter. The C2 femurs were narrower and had a smaller canal flare index (2.88 ± 0.50) than C1 femurs (3.64 ± 0.69). The ML-to-AP ratio of the proximal femoral medullary canal was significantly smaller in the C2 group. Accordingly, C2 femurs required thinner stems, more non-sprouted sleeves, and had a higher rate and required a longer length of shortening osteotomies. At an average follow-up of 36.0 months, the C1 and C2 groups had a similar Harris Hip Score (83.5 ± 14.3 vs. 84.2 ± 9.8, P = 0.771) and no stem loosening occurred in either group.
Conclusion: C1 and C2 proximal femurs have substantial differences in the coronal, sagittal, and axial planes. In the setting of THA, C2 femurs may therefore require thinner stems, more non-sprouted sleeves, and have a higher rate and require a longer length of shortening osteotomies.
Keywords: Computed tomography; Femoral morphology; Hartofilakidis type C; Hip dysplasia.