Does Body Mass Index affect the outcomes of patients undergoing unicompartmental knee arthroplasty? A retrospective cohort study

Abstract Background: Unicompartmental knee arthroplasty（UKA） has become one of the main methods for the treatment of unicompartmental knee osteoarthritis. There is still lack of medium term data on the outcomes of UKA and survival rate of prosthesis in different body mass index (BMI) groups. Objective: we focus on the effectof BMI on the medium clinical outcomes of UKA. Methods: The retrospective study included patients who received UKA at our hospital, between January 1, 2014 to December 31, 2017.All patients All patients underwent surgery of unicompartmental knee arthroplasty. They were divided into three groups according to BMI. normal body mass group [group A, BMI 14.50～24.99 kg/m2, 14 cases (16 knees)], overweight group [group B, BMI 25.00-27.99 kg/m2, 15 cases (17 knees)], obesity group[group C, BMI 28.00-39.99 kg/m2, 16 cases (18 knees)]. There was no significant difference in gender, age, sides, diseaseduration, and preoperative American Special Surgery Hospital (HSS) score, pain visual analogue scale (VAS) score, and knee range of motion (ROM) among 3 groups (P>0.05). The operation time, intraoperative dominant blood loss, and the postoperative decreased amount of hemoglobin at 2 week were recorded and compared among 3 groups. The the Knee Society Score (KSS), the University of California at Los Angeles (UCLA) activity scale，Knee society score ，VAS score, and ROM were evaluated in three groups. Results: Forty-five of 58 eligible patients were included. All the 45 patients were followed up 36-70 months, with an average of 57.55 months. The function of knee joint in all patients was improved and the pain was obviously relieved. Significant differences were found in the knee score, function score and the knee society score between three groups at 70-month follow-up (p<0.05). Conclusions: For normal and overweight patients with anterior medial compartmental osteoarthritis of the knee joint, the use of minimally invasive UKA can achieve satisfactory short- and medium-term effectiveness. However, this procedure should be chosen carefully with overweight patients.