The Medial Rotation Knee replacement: Clinical and radiological results of a multi-centre surveillance study at five years

Background The Medial Rotation Knee (MRK) has one of the lowest revision rates of total knee replacement designs in the National Joint Registry. While survival is one metric of performance of implants, patient-reported outcomes, combined with clinical and radiological evaluation, allow more complete analysis. We report the five-year results of a prospective, multi-centre surveillance study of the MRK. Methods A 16-surgeon, three-centre series of 520 total knee replacements were performed in 486 patients, comprising 182 males and 304 females. The mean age was 70.3 years (46–96) and BMI 29.5 kg/m2 (18–57). Study subjects were given questionnaires pre-operatively, at six months, and annually thereafter. Clinical and radiological reviews were scheduled pre-operatively, at six months, three and five years. Results At five years, 395 of the original 486 patients (427 of 520 knees) remained under active review. Twenty-six patients (27 knees) had withdrawn, 44 patients/knees had died and one was excluded. Thirteen patients (14 knees) were lost to follow-up, but were not revised. Seven knees were revised, equating to a survival probability of 98.6% at five years. There were significant improvements in mean Oxford Knee Score (21.23–35.79), EQ-5D (0.440–0.694) and Knee Society Score (Knee 43.00–83.97; Function 49.45–71.39). Of the radiographs available for evaluation, radiolucency was identified in 25 knees (14.6%) with one case of osteolysis of the tibial component. Conclusion In addition to excellent survivorship, mid-term patient-reported, clinical and radiological results at five years are satisfactory, and consistent with other medial pivot designs.