No difference in implant survival between 28-mm M2a RingLoc metal-on-metal and metal-on-polyethylene total hip arthroplasty: results from the Finnish Arthroplasty Register

Antton Palomäki; Matias Hemmilä; Markus Matilainen; Antti Eskelinen; Jaason Haapakoski; Ari-Pekka Puhto; Jukka Kettunen; Konsta Pamilo; Mikko Manninen; Anna Vasara; Keijo T Mäkelä

doi:10.2340/17453674.2022.5252

Authors

Antton Palomäki Department of Orthopaedics and Traumatology, Turku University Hospital, Turku, and University of Turku
Matias Hemmilä Department of Orthopaedics and Traumatology, Turku University Hospital, Turku, and University of Turku https://orcid.org/0000-0003-3727-9036
Markus Matilainen Turku PET Centre, Turku and Faculty of Science and Engineering, Åbo Akademi University, Turku
Antti Eskelinen Coxa Hospital for Joint Replacement, Tampere https://orcid.org/0000-0003-0302-0253
Jaason Haapakoski National Institute for Health and Welfare, Helsinki https://orcid.org/0000-0001-5145-3956
Ari-Pekka Puhto OYS Centre for Musculoskeletal Surgery, Oulu University Hospital, Oulu https://orcid.org/0000-0002-5006-4876
Jukka Kettunen Department of Orthopaedics and Traumatology, Kuopio University Hospital, Kuopio https://orcid.org/0000-0002-2797-2497
Konsta Pamilo Coxa Hospital for Joint Replacement, Tampere https://orcid.org/0000-0001-5961-4072
Mikko Manninen Orton Hospital, Helsinki
Anna Vasara Department of Orthopaedics and Traumatology, Helsinki University Hospital and University of Helsinki, Helsinki, Finland https://orcid.org/0000-0001-6706-1674
Keijo T Mäkelä Department of Orthopaedics and Traumatology, Turku University Hospital, Turku, and University of Turku

DOI:

https://doi.org/10.2340/17453674.2022.5252

Keywords:

Arthroplasty, Hip, Implants

Abstract

Background and purpose: Long-term outcome of small head (28 mm) metal-on-metal (MoM) total hip arthroplasty (THA) is available mainly for Metasul devices (Sulzer Medica, Winterthur, Switzerland). Biomet MoM THA was frequently used in Finland. Therefore, we assessed long-term survivorship of the M2a 28-mm RingLoc MoM THA (Biomet, Warsaw, IN, USA) and compared it with the metal-on-polyethylene (MoP) RingLoc THA from the same manufacturer.
Patients and methods: We conducted a register study based on THAs from the Finnish Arthroplasty Register performed between January 1, 2000 and December 31, 2007. 290 28-mm head M2a MoM THAs and 1,647 28-mm head MoP THAs (reference group) were included. The endpoint was revision for any reason, or revision for aseptic loosening, osteolysis, liner wear, or metallosis as one group. Kaplan–Meier survival estimates were calculated, and revision risks were assessed using a Cox multiple regression model, both with 95% confidence intervals (CI).
Results: No difference was found in the 15-year Kaplan–Meier survivorship between the 28-mm head M2a RingLoc MoM THA and the reference group for any reason for revision (87.7% [82.9–92.1] and 83.3% [81.0–85.3], respectively). The adjusted hazard ratio (HR) for any reason for revision for the MoM THA group compared with the reference group was at least equal or better (0.70 [0.48–1.02]). Both groups presented similar survival for revision for aseptic loosening of the cup, osteolysis, liner wear, or metallosis, at 96.2% (92.7–98.0) and 95.4% (93.9–96.5), respectively.
Interpretation: In the long-term survival there was no difference between the M2a 28-mm RingLoc MoM THA and 28-mm MoP THA. Further follow-up regimens for M2a 28-mm RingLoc THA patients may be unnecessary, but long-term metal ion and radiological data is needed before any formal suggestions.