Abstract: BACKGROUND: In the follow-up after unicompartmental knee arthroplasty, some patients have knee pain, among which postmenopausal obese women are the most common. As an important index to measure the degree of body obesity, whether body mass index is related to the curative effect after unicompartmental knee arthroplasty and whether obesity will affect the function of knee joint after operation are worthy of further study.
OBJECTIVE: To evaluate the clinical efficacy of postmenopausal obese women undergoing medial unicompartmental knee arthroplasty, and to determine the influence of body mass index on the quality of life after unicompartmental knee arthroplasty.  
METHODS: Female postmenopausal patients who underwent medial unicompartmental knee arthroplasty for the first time due to medial knee pain from January 2017 to January 2019 in the Fourth Clinical Medical College of Xinjiang Medical University were enrolled. A total of 270 cases were included according to inclusion and exclusion criteria, and were divided into 4 groups according to preoperative body mass index: There were 42 cases in normal group (body mass index 18.5-22.9 kg/m2), 58 cases in overweight group (body mass index 23.0-24.9 kg/m2), 122 cases in obese group (body mass index 25.0-29.9 kg/m2), and 48 cases in severely obese group (body mass index ≥30 kg/m2). Hospital for Special Surgery score, Western Ontario and McMaster Universities Osteoarthritis Index score, knee range of motion, visual analog scale score, and hip-knee-ankle angle were compared before, after and at the last time in each group. Patients were followed up to record the time of use of prostheses after surgery and reasons for failure or revision. The effective utilization rate of prostheses was calculated and compared in each group. Survival curve was used for statistical analysis of the effective utilization rate of prostheses. 
RESULTS AND CONCLUSION: (1) There was no significant difference in postoperative follow-up time, knee joint range of motion, visual analog scale score, and hip-knee-ankle angle between the groups (P > 0.05). (2) The Hospital for Special Surgery score and Western Ontario and McMaster Universities Osteoarthritis Index score of each group in final follow-up were significantly improved compared with those before surgery (P < 0.05), and the postoperative effect was obvious in each group (P < 0.05).  Regarding Hospital for Special Surgery score, the improvement effect was worse in the severely obese group. (3) The comparison of hip-knee-ankle angle between all groups immediately after surgery and the last follow-up showed that there were significant differences between the other groups at two time points (P < 0.05) except the normal group (P > 0.05). (4) The effective utilization rate of prosthesis in normal, overweight, obesity, and severely obese groups was 100%, 95%, 94%, and 94%, respectively, and there was no significant difference between the groups (χ2=2.532, P=0.469). (5) It is indicated that body mass index of postmenopausal obese women had no significant effect on the effective utilization rate of medial unicompartmental prosthesis. Obesity is an important factor affecting the postoperative knee function score and the effective utilization rate of prosthesis. Weight should be properly controlled before and after unicompartmental knee arthroplasty. At the same time, female body mass index ≥ 30 kg/m2 is not the best indication for unicompartmental knee arthroplasty. It is suggested that female patients undergoing unicompartmental knee arthroplasty should control body mass index below 30 kg/m2.

中国组织工程研究杂志出版内容重点：人工关节；骨植入物；脊柱；骨折；内固定；数字化骨科；组织工程

Key words: postmenopausal women, body mass index, knee osteoarthritis, unicompartmental knee arthroplasty, estrogen, osteoporosis