Metal-backed versus all-poly tibia in the original cartier unicompartmental knee arthroplasty: outcomes and survivorship at long-term follow-up

Purpose Unicompartmental knee arthroplasty (UKA) is a viable option for localized osteoarthritis (OA) or avascular osteonecrosis with several advantages over total knee arthroplasty (TKA). UKA implants may feature a tibial component either all-polyethylene (AP) or metal-backed (MB). This study aims to retrospectively compare the clinical outcomes and survivorship of 74 UKAs over 16 years, focusing on comparing the results and survivorship of MB versus AP tibial tray. Materials and methods This retrospective study assesses 74 patients who underwent medial unicompartmental knee arthroplasty (UKA) using ACCURIS Uni Knee System (Smith & Nephew, Memphis, TN, USA) implants between January 2003 and December 2008. Patients were divided in two groups: all-polyethylene (AP) tibial implants and metal-backed (MB) tibial components. The two groups were compared at final follow-up regarding survivorship, revision rates and clinical outcomes using the WOMAC score, Oxford Knee Score (OKS) and Forgotten Joint Score (FJS-12). Results Between January 2003 and December 2008, 74 medial unicompartmental knee arthroplasties were implanted in 74 patients. Clinical outcomes were assessed with a mean follow-up of 214.4 months. The implant survivorship was 97.3% for the MB-UKAs and 94.6% for the AP-UKAs (p = 0.55). The average OKS in the MB-UKAs was 42, while in the AP-UKAs 41.6 (p = 0.53), with a total of 64.9% of patients exhibiting excellent outcomes (OKS > 41) and 35.1% showing good outcomes (OKS: 34-41). The average FJS-12 at final follow-up was 81.5 for the MB-UKAs and 82.3 for the AP-UKAs (p = 0.34). The average WOMAC score was 20. 9 for the MB-UKAs and 22.4 for the AP-UKAs (p = 0.55). No statistically significant differences were found between AP-UKAs and MB-UKAs in terms of patient demographics, surgical indications, or clinical outcomes. Conclusions This research demonstrated outstanding implant durability and favorable outcomes during extended follow-up periods for both cohorts undergoing medial UKA utilizing the original fixed bearing Cartier design. The results regarding both survivorship and PROMs were equivalent the AP group and the MB group.