Inferomedial Hip Center Decreases Failure Rates in Cementless Total Hip Arthroplasty for Crowe II and III Hip Dysplasia.

BACKGROUND: We sought to evaluate the outcomes of cementless acetabular components used in patients with Crowe II and III dysplasia, and to compare outcomes between cups placed within vs outside of an "anatomic" zone. Our specific aims were to (1) plot hip centers in these patients at our institution to characterize "anatomic" vs "nonanatomic" positions, (2) evaluate the association between hip center and radiographic loosening, (3) determine whether hip center was associated with acetabular component revision, and (4) compare patient-reported outcome scores between groups.

METHODS: We retrospectively reviewed 88 primary cementless total hip arthroplasties at a mean follow-up of 10 years (range 2-26 years). Patients were 85% female, with a mean age of 44 years (range 28-61 years) and a body mass index of 27 kg/m2 (range 19-42 kg/m2 ). Medical records and radiographs were reviewed, and a survey was conducted for all patients. Anatomic hip center was defined using the 4-zone system, wherein centers are "anatomic" if they are <1 cm superior and <1 cm lateral to the approximate femoral head center. Cox proportional analyses were used to compare outcomes between groups.

RESULTS: Seventy hips (80%) had an anatomic hip center. Anatomic hips had a lower incidence of radiographic acetabular loosening (0% vs 17%, P = .007) and cup revision (0% vs 28%, P = .0002). There were no differences in Hip Disability and Osteoarthritis Outcome and Joint Replacement Scores (96.2 ± 5 vs 91.9 ± 12, P = .7).

CONCLUSION: The incidence of aseptic loosening and cup revision were lower when hip center was <1 cm superior and 1 cm lateral to the approximate femoral head center.