Long-term outcomes of a dual-mobility cup and cementless triple-taper femoral stem combination in total hip replacement: a multicenter retrospective analysis.

BACKGROUND: The separate design concepts of dual-mobility cups and triple-taper femoral stems were developed to improve survivorship following total hip replacement (THR) by reducing instability/dislocation and enabling enhanced fixation. Successful outcomes at over two decades have been reported with earlier-generation devices based on these concepts. The current study aimed to provide the first long-term results with a unique pairing of later-generation dual-mobility cup and triple-taper cementless femoral stem after a decade of use in patients undergoing THR. METHODS: In this retrospective analysis, records were reviewed for all subjects implanted with this dual-mobility cup/cementless femoral stem combination at three centers between 2002 and 2005. Any subject who had not already had follow-up visit beyond 10 years, was not previously revised, and still living were invited for a single follow-up visit consisting of Merle d'Aubgine Scores, the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index, and standard radiographs. RESULTS: There were 244 THRs available for analysis. At a mean follow-up of 11.9 years, the Kaplan-Meier survivorship (endpoint: revision for any reason) was 99.1% (95% CI, 97.6-99.7) for the stem and 95.9% (95% CI, 93.1-97.6) for the cup. Merle d'Aubigne Scores were significantly improved from baseline and WOMAC scores were in the satisfactory range at the final follow-up. Radiographic analysis revealed no cases of stem subsidence, no cases of bone hypertrophy, 1 (0.4%) case of bone atrophy, and 3 (1.2%) cases of osteolysis around the stem. No subjects had radiolucent lines greater than 1 mm in any femoral Gruen zone. Evidence of cup migration was seen in 1 (0.4%) subject and 1 (0.4%) subject had evidence of osteolysis that was seen in Gruen zones I, II, IV, and V. CONCLUSIONS: This combination of a later-generation dual-mobility cup and cementless triple-taper stem was associated with excellent survivorship and satisfactory functional outcomes at over 10 years follow-up. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02648152. Date of registration: January 6, 2016. Retrospectively registered.

The dual-mobility POLARCUP: first results from a multicenter study.

Dislocation is a leading cause of revision after total hip arthroplasty (THA). To address this risk, dual-mobility technology was developed, which features a mobile polyethylene liner locked onto a femoral head and articulating in a metallic acetabular shell. This study reports clinical outcome data after implantation of the third-generation POLARCUP Dual-Mobility System (Smith & Nephew Orthopaedics AG, Rotkreuz, Switzerland). Primary THA procedures were performed in 150 patients. At 7.1 years, cumulative cup survival according to Kaplan-Meier was 97.4%. The mean Postel-Merle d'Aubigne score improved from 8.9 to 17.1 during the investigation. Two cups were revised at 5.4 and 6.4 years because of aseptic loosening. No dislocations were observed during follow-up. The current results confirm excellent early to midterm clinical outcomes for the POLARCUP Dual-Mobility System.