BACKGROUND: Rotating-hinge implants provide the highest constraint in total knee arthroplasty (TKA) and are used when stable alignment cannot be achieved with less constrained designs. Outcomes are difficult to interpret because primary and revision cases are frequently combined.
METHODS: We retrospectively reviewed 110 patients (120 knees) treated with rotating-hinge TKA from January 1, 2013, through June 30, 2025 (clinical follow-up updated through December 31, 2025), representing 120 of 4,893 (2.5%) of TKAs in this period. Cases were analyzed in two predefined groups: primary (52 knees) and revision (68 knees). There was no minimum follow-up threshold; all primary cases had at least 24 months. The mean follow-up was 118.0 months (range, 24.0 to 156.0) in the primary group and 72.0 months (range, 6.0 to 156.0) in the revision group. Function was assessed with the Knee Society Function Score (KSFS) and Oxford Knee Score (OKS). Implant survivorship (endpoint: any re-revision or component exchange/removal) was estimated by Kaplan-Meier analysis with log-rank comparisons.
RESULTS: Both groups improved significantly: KSFS change +35.1 ± 3.4 (primary) and +31.0 ± 6.2 (revision); OKS change +26.0 ± 8.6 and +24.7 ± 9.4, exceeding the 5-point OKS minimal clinically important difference in 94.2 and 89.7%, respectively. Intraoperative fractures occurred in five primary (9.6%) and four revision (5.9%) knees; deep infection occurred in one primary knee (1.9%). There were three knees that met the failure definition: one of 52 primary knees (deep infection, nine months) and two of 68 revision knees (aseptic loosening, 46 and 74 months). The Kaplan-Meier 5-year survival was 98.1% (95% confidence interval [CI], 87.1 to 99.7) in primary knees and 98.2% (95% CI, 88.2 to 99.8) in revision knees; log-rank P = 0.58.
CONCLUSION: Rotating-hinge TKA produced meaningful functional and patient-reported gains in both settings. Complications should be interpreted in the context of severe deformity, instability, bone loss, and revision complexity; attribution to underlying pathology, rather than implant constraint, remains inferential, as no matched comparator was available. These findings support selective use of modern rotating-hinge implants in high-complexity knees.
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