Oxford phase 3 unicompartmental knee arthroplasty (clinical and radiological results)

PURPOSE: To evaluate the radiological, clinical results and determine the factors affect implant survival of Oxford phase 3 unicompartmental knee arthroplasty(UKA) which were performed for unicompartmental osteoartrithis between 2011-2016. MATERIALS METHODS: In this retrospective study; Oxford phase 3 UKA applied 52 knees of 49 patients with minimum 6 months follow-up were included. Lateral UKA, hemiCAP applied patients not inclueded. Knee Society Score(KSS), functional knee society score(fKSS), Oxford Knee Score(OKS), visual analog scale(VAS) score were pre and postoperatively used. Range of motion(ROM), body mass index(BMI), patello-femoral arthrosis presence were recorded. In radiological evaluation we used posterior tibial slope(PTS), tibial plato angle(TPA), femorotibial angle(FTA) in addition to Oxford radiological criteria. We grouped patients according to their ages, follow-up time, body mass index, radiological criteria, patellofemoral arthrosis presence, complication and revision existence. Clinical, functional results of these groups compared statistically. The factors which affect upcoming of revision by regression analysis and four years survivorship without infirmity by Kaplan-Meier survival analysis were determined. RESULTS: 40 female, 9 male patients inclueded with avarage age, BMI, follow-up time is 60, 34.6, 30 months. OKS, KSS, fKSS, ROM improved significantly from 12.7, 43.3, 34.8,111º preoperatively to 37.8, 85.7, 82, 123º postoperatively. VAS decreased from 9 to 2.6. Not significant differences was found between the age and patellofemaral arthrosis groups. Postop VAS scores were high, knee scores were significantly low at morbid obeses while other BMI groups got perfect knee scores. Knee scores are significantly low, VAS scores are high at patients with femoral component varus is 10º, greater than 10 º, postop TPA is smaller than 85º, higher than 90º. Most frequent mistake was sagittal plane positioning of femoral component. Lateral positioning and more than 10º varus-valgus of tibial component, abnormal PTS, more than 10º varus-valgus of femoral component are the most frequent mistakes of revised knees. All revised cases were in the group that operated at first two years of surgical experience. Postop PTS, TPA, morbid obesity are the most significant factors which affect upcoming revision. Revision ratio is 11.5%. Acccording to Kaplan-Meier survival analysis; 1, 2, 3, 4 years survivorship without any infirmity are 93.7%, 91.5%, 91.5%, 85.7% respectivly. CONCLUSION: Independent from age, patellofemoral arthrosis; it is possible to achieve perfect results at anteromedial arthrosis with UKA by convenient patient selection, correct surgical technique and improved surgical experience. Postop TPA, PTS and patient based factor morbid obesity are the most important factors for success.