Comparing Clinical and Radiological Outcomes for a Three-Dimensional Printed Highly Porous Cup and a Hydroxyapatite-Coated Non-Highly Porous Cup in Total Hip Arthroplasty Using Propensity Score Matching

BACKGROUND: The use of highly porous acetabular components in total hip arthroplasty (THA) has gained popularity. To elucidate the clinical and radiological outcomes of three-dimensional (3D)-printing highly porous cups, we compared highly porous cups and hydroxyapatite (HA)-coated non-highly porous cups in computed tomography (CT)-based navigated THA. METHODS: We retrospectively investigated 196 hips of 175 patients (the highly-porous group, 112 hips of 97 patients; the HA-porous group, 84 hips of 78 patients) who underwent THA using a computed tomography-based navigation system. After propensity score matching for age, sex, diagnosis, and surgical approach, each group comprised 66 hips. Clinical outcomes were evaluated using the Japanese Orthopaedic Association hip score and Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire score preoperatively and at six, 12, and 24 months postoperatively. Radiological outcomes for cup orientation, positioning, initial gap, migration, loosening, and radiolucent lines were assessed. Cup placement was measured using 3D templating software. RESULTS: Clinical outcomes did not differ significantly between groups after two years. The mean absolute error of cup orientation did not differ significantly between the two groups (inclination: 2.9 ± 2.3° versus 2.6 ± 2.2°, respectively; anteversion: 2.7 ± 2.0° versus 2.7 ± 2.0°, respectively). There was no migration or loosening in both groups during the study period. The incidence of initial gap was significantly higher in the highly porous group than in the HA-porous group (18 of 66 cases, 27.3% versus 8 of 66 cases, 12.1%, P = 0.027). The radiolucent lines exhibited progressive decline during the 2-year follow-up in both groups, and there were no significant differences at two years. CONCLUSIONS: The 2-year clinical outcomes and radiological evaluations of the 3D highly porous and non-highly porous cups were comparable. Initial gaps in the 3D-printing highly porous cups diminished, and the highly porous cups showed excellent radiological outcomes.