Surprisingly Low Rates of Aseptic Loosening in 575 Rotating-Hinge Total Knee Arthroplasties.

Abstract

BACKGROUND Contemporary rotating-hinge total knee arthroplasties (RH-TKAs) have shown reasonable short-term survivorship in smaller series, but concerns remain regarding risks of aseptic and septic failure. The purpose of this study was to assess outcomes of contemporary RH-TKAs in one of the largest series to date. METHODS We retrospectively identified 575 RH-TKAs (60% used for aseptic etiologies and 40% used during reimplantation in 2-stage treatment of periprosthetic joint infection [PJI]) from 2002 to 2021 at a single institution. The mean age was 67 years, 58% were female, and the mean body mass index was 33 kg/m2. Sixty-five percent had Anderson Orthopaedic Research Institute (AORI) type-2B or 3 bone loss. Kaplan-Meier survivorship analyses were performed. The mean follow-up was 6 years (range, 2 to 19 years). RESULTS Survivorship free from any revision was 76% at 5 years and 64% at 10 years. The most common revision indications were PJI (54%) and aseptic loosening (20%). RH-TKA used in the primary setting showed better survivorship compared with RH-TKA used during reimplantation after PJI (79% versus 60% at 10 years). Survivorship free from revision for aseptic loosening was 96% at 5 years and 90% at 10 years. Survivorship free from revision for PJI was 84% at 5 years and 81% at 10 years. Survivorship free from revision for PJI was even lower for RH-TKAs used during reimplantation, 74% at 5 years and 73% at 10 years. RH-TKA used during reimplantation in the treatment of PJI was associated with an increased risk of any revision (HR = 2, p < 0.001). Radiographic analysis of 425 knees that were not revised and had radiographs available for review showed that 6% of femoral components and 8% of tibial components had evidence of loosening at the time of final follow-up. The mean Knee Society Score improved from 33 to 69 at 2 years (p < 0.001). CONCLUSIONS The 10-year survivorship free from aseptic loosening was 90% in this large series of RH-TKAs. This represents one of the best survivorships free from aseptic loosening published to date. Knees with prior PJI had markedly poorer survivorship than knees treated for aseptic etiologies, with double the risk of revision. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.