Clinical, functional, and radiographic outcomes of primary total knee arthroplasty using a rotating hinge implant: A retrospective cohort study

Introduction/Objective. The aim was to evaluate the clinical, functional, and radiographic outcomes, as well as implant survivorship, of primary total knee arthroplasty (TKA) using a rotating hinge knee (RHK) prosthesis in complex primary knees. Methods. This single-center, retrospective observational cohort study included 32 patients (32 knees) operated between December 1, 2023, and December 31, 2025. Primary outcomes were cumulative implant survivorship (Kaplan-Meier analysis with revision for any cause as the endpoint) and complication rates. Secondary outcomes included functional scores using the Oxford Knee Score (OKS), range of motion (ROM), coronal alignment correction via the mechanical femorotibial angle (mFTA), and radiographic stability. Results. The median follow-up was 20.3 months. Surgical indications included primary (43.8%) and secondary osteoarthritis (21.9%), post-traumatic arthritis (21.9%), neuropathic arthropathy (9.4%), and proximal tibial nonunion (3.1%). Preoperative ligamentous instability was present in 87.5% of knees. Cumulative 20-month implant survivorship was 87.5% (all 4 revisions occurred within five months postoperatively due to early periprosthetic joint infection and wound complications; 0% aseptic loosening). The overall complication rate was 34.4%. Postoperatively, the mean OKS significantly increased from 13.25 ± 5.62 to 41.09 ± 3.74 (ΔOKS = +27.84, p < 0.001), median ROM increased from 70° to 115° (p < 0.001), and absolute coronal deformity (deviation from neutral biomechanical axis) decreased from 23.90° to 2.36° (p < 0.001). Conclusion. Primary TKA with an RHK implant provides excellent functional recovery, robust early mechanical stability, and predictable deformity correction in complex primary cases, though strict infection control and soft-tissue handling remain essential.