Medium And Long-Term Clinical Outcome Analysis Of The Mobile-Bearing Unicompartmental Knee Arthroplasty

Objective:To observe and analyze the mid-and long-term clinical effects of mobile-bearing unicompartmental knee arthroplasty in many aspects through the preoperative and postoperative data obtained from the follow-up samples after unicompartmental knee arthroplasty with Oxford phase III.Methods:Part 1:Unicompartmental knee arthroplasty cases using Oxford phase III unicondylar prosthesis in Qingdao University Affiliated Hospital from June 2008 to June2014 were selected for retrospective analysis.Knee Association Score(KSS),KSS functional score,and range of motion(ROM),Hospital for special surgery score(HSS),Range of motion(ROM),Femoral tibial angle(FTA)were collected before and at the last follow-up.A total of 193 patients(229 knees)were received an average of 93.3±24.2months’follow-up.According to the BMI,the patients were divided into normal weight group:BMI 18.5-22.9 kg/m~2,overweight group:23-24.9 kg/m~2,obesity group:25-29.9kg/m~2,severe obesity group:≥30 kg/m~2.The mid-and long-term clinical effects of the mobile-bearing unicompartmental knee arthroplasty were evaluated by analyzing the scores,complications within each group of BMI.Part 2:Collection of scores is the same as Part 1.To explore the impact of BMI on mid-and long-term clinical effects of the mobile-bearing unicompartmental knee arthroplasty through stratified analysis of various scores,ROM,survival rate of prosthesis and radiographic parameters between groups.Part 3:Among 456 patients(506 knees)who underwent medial mobile-bearing unicompartmental knee arthroplasty from June 2013 to June 2017,28 patients who failed early were selected,and all patients were followed up for a mean of 24.2 months(range,1-56 months).Demographic data,including age,gender,body mass index,date of surgery,and preoperative activity level,were recorded for each patient in the failure group.Another 28 patients was then selected as matching controls and they were paired in a 1:1 ratio according to the aforementioned criteria.Collect and record the preoperative and postoperative femoral tibial angle(FTA),tibial plateau angle(TPA),posterior tibial slope(PTS)of the two groups of patients.The possible risk factors for postoperative failure of UKA,including preoperative and postoperative FTA,TPA,PTS and difference values between them were performed by univariate Logistic regression analysis and multivariate Logistic regression analysis.Results:Part 1:There was a statistical difference in the scores between the preoperative and the last follow-up(P<0.05).The incidence of complications was 6.99%,and the prosthesis survival rate was 96.07%.Part 2:There was no significant difference in preoperative KSS score,KSFS score,HSS score,ROM and FTA immediately after operation among the BMI groups(P>0.05).The KSS score(F=8.141,P<0.05)and HSS score(F=4.248,P<0.05)at the last follow-up showed significant differences among the groups,only the severe obesity group was significantly different from the other three groups(P<0.05).There was no statistically significant difference among the groups in KSFS score(F=1.534,P>0.05),ROM(F=0.236,P>0.05)and FTA(F=1.382,P>0.05)at the last follow-up.Patients with BMI≥30 kg/m~2had greater FTA inversion at the last follow-up,and the difference was statistically significant(P<0.05).It is worth noting that the evaluation indexes such as KSFS score,ROM and FTA of the severe obesity group are worse than the other three groups,although the degree is not particularly obvious.There was no significant difference in the survival rate of the prosthesis among the BMI groups(2=1.861,P=0.602),but the survival rate of the prosthesis in the severe obesity group was lower than the other three groups.Part 3:The prosthesis revision rate in this study cohort was 6.1%,the dislocation of polyethylene gasket is the main failure mode of UKA in this study(64.3%).The results of multivariate logistic regression analysis showed that the PTS difference value(OR=26.252)was statistically significant(P<0.05),so the oversize difference value of PTS was should be considered a risk factor for the failure of UKA surgery.Conclusion:The mobile-bearing unicompartmental knee arthroplasty has excellent mid-and long-term clinical and radiographic results,and high prosthesis survival rate.BMI has no effect on the mid-and long-term survival rate of mobile-bearing unicompartmental prosthesis,Severe obesity(BMI≥30 kg/m~2)is a significant predictor of smaller improvement in clinical outcomes after UKA,surgeons should be cautious in choosing obese patients.Polyethylene gasket dislocation is the most important failure mode of the mobile-bearing UKA.Through radiographic analysis,it is found that the oversize difference value of PTS before and after surgery is a risk factor for the failure of UKA,in order to reduce the failure risk of UKA,the posterior angle of the prosthesis should be controlled.