Reverse Hip Replacement System: Addressing Instability Concerns or Introducing New Risks? A Scoping Review

Abstract

Background: To address instability after total hip arthroplasty (THA), a reverse hip replacement system (RHRS) has been proposed, inspired by the concept of reverse total shoulder arthroplasty. Objective: to evaluate the early functional, radiological, and complication outcomes of the RHRS. Methods: A systematic search in PubMed and Scopus databases was performed in March 2025 using predetermined search terms, which revealed an initial 656 results, and only four studies were eligible for inclusion (one biomechanical study and three clinical studies (one case series and two case reports)). Results: The three clinical studies included 24 patients aged 60 to 79 years; 13 (54.2%) were male, and all were diagnosed with advanced hip OA. After follow-up ranging from 3 weeks to 24 months, all patients were satisfied with the results, except for 2 (8.3%). Detailed function and PROM outcomes for 22 patients at 24 months of follow up showed significant improvement in WOMAC, HHS, OHS, HOOS, SF-36 physical component summary (PCS), and ED-5D (p0.05). However, there was a nonsignificant change in the SF-36 mental component summary (MCS) (p=0.272). Radiological outcomes, as determined by RSA analysis, at 24 months for 18 acetabular cups showed a mean migration of 0.087 ± 0.152 mm. Seven (29.2%) complication incidents, one intraoperative calcar crack, one deep PJI, one postoperative traumatic dislocation, one femoral neuropraxia, one occasional pain, and two recalcitrant iliotibial band syndrome. The biomechanical study results showed lower polyethylene wear debris equivalent to other systems, no wear debris due to metal-on-metal contact, and no signs of polyethylene edge or backside wear. Conclusion: Besides the promising biomechanical results, RHRS's early functional and radiological outcomes are encouraging; however, the incidence of complications is considerably high. Moreover, the results should be interpreted cautiously to the small number of included patients and the short follow up period.