Abstract
BACKGROUND: Three-dimensional (3D)-printed acetabular cups may enhance initial fixation and osseointegration; however, early radiographic findings warrant careful monitoring. This study evaluated short-term radiographic outcomes of an electron beam melting (EBM)–fabricated 3D-printed titanium acetabular component (GS cup) used in primary total hip arthroplasty (THA). METHODS: This multicenter retrospective cohort study included 236 consecutive primary THAs performed at seven hospitals. Postoperative radiographs at approximately 2 years were analyzed (mean follow-up, 24.6 months; range, 23–31 months). The primary endpoint was the presence of a radiolucent line (RLL) in DeLee and Charnley Zone 2 at 2 years. Secondary endpoints included initial polar gaps (≥ 1 mm), gap filling, RLLs in other zones, osseointegration assessed by Moore criteria, and survivorship with acetabular component revision for any reason as the endpoint. RESULTS: Initial polar gaps occurred in 19/236 hips (8.1%); 14/19 (73.7%) demonstrated gap filling at follow-up. RLLs were present in 48/236 hips (20.3%) (Zone 1, 13.6%; Zone 2, 9.7%; Zone 3, 11.4%). In exploratory univariate analyses, same-diameter reaming showed lower proportions of polar gaps and Zone 2 RLLs compared with 1-mm underreaming; however, no factors remained independently associated with Zone 2 RLLs after multivariable adjustment. At follow-up, 188 cups (79.7%) demonstrated ≥ 3 Moore signs, and no acetabular component revisions occurred by the standardized 2-year assessment. CONCLUSIONS: In this multicenter retrospective cohort, the EBM-fabricated 3D-printed titanium acetabular component demonstrated generally favorable early radiographic findings and no acetabular component revisions at approximately 2 years. Given the retrospective design and the limited number of Zone 2 RLL events, the observed associations between surgical factors and radiographic findings should be interpreted cautiously and considered hypothesis-generating. Longer-term follow-up, ideally with comparative designs and clinical outcomes, is warranted. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12891-026-09708-x.