• Francesco Castagnini, Barbara Bordini, Monica Cosentino, Emanuele Diquattro, Mara Gorgone, and Francesco Traina.
• Ortopedia-Traumatologia e Chirurgia Protesica e dei Reimpianti d'anca e di Ginocchio, IRCCS Istituto Ortopedico Rizzoli, Via Pupilli 1, 40136, Bologna, Italy. francescocastagnini@hotmail.it.
• Arch Orthop Trauma Surg. 2024 Sep 3.

IntroductionOptimal bearing size in total hip arthroplasty (THA) has not been clearly ascertained, but large diameter ceramic balls may improve function and implant stability, with minimal concerns for wear. Delta ceramic-on-ceramic (COC) THA were stratified based on head diameter (32, 36 and 40 mm), aiming to assess: 1) survival rates, reasons for revision and hazard ratios for failure; 2) survival rates and hazard ratios for aseptic loosening, dislocation/primary instability, liner failure.Materials And MethodsA regional arthroplasty registry was enquired about Delta COC THA performed for primary osteoarthritis, stratified by head size. 13,161 primary cementless THAs were included in the study, with a mean follow-up of 5.7 years (range: 0-17): 3980 (30.2%) 32 mm balls, 8327 (63.3%) 36 mm heads, 854 (6.5%) 40 mm heads.ResultsThe three cohorts achieved similar survival rates (p = 0.99) and adjusted hazard ratios (p > 0.05). No revisions for head breakage or metallosis occurred. When revision for cup aseptic loosening was the endpoint, the survival rates of three cohorts (p = 0.08) and the adjusted hazard ratios (p > 0.05) were similar. The three cohorts achieved comparable survival rates when revision for dislocation/primary instability was the endpoint (p = 0.08). When the endpoint was revision for liner breakage, 32 mm cohort showed higher rates of revision (p = 0.01). No liner failure was detected in the 40 mm cohort.Conclusions32 mm, 36 mm and 40 mm provided similar 10-year survival rates in Delta COC THA. 40 mm heads emerged as safe options but did not lower the revisions for dislocations/primary instability.Level Of EvidenceIV (therapeutic study).© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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