Clinical results of medial mobile bearing unicompartmental knee arthroplasty using kinematic alignment technique with at least 5-years follow-up

Abstract

Objective: To evaluate the mid-term results of kinematic alignment technique in Oxford mobile bearing unicompartmental knee arthroplasty (OUKA). Methods: The clinical data of first 98 knees OUKA performed from June 2015 to January 2017 using kinematic alignment technique with at least 5-year follow-up were retrospectively analyzed, including 28 knees in 24 males and 70 knees in 62 females. The mean surgical age was (68.4±8.0) years. The clinical data of patients before operation and at the last follow-up were recorded and compared. The knee Hospital for Special Surgery (HSS) score, visual analogue scale (VAS) of pain, range of motion, surgical complications and radiological assessment were analyzed to evaluate the efficacy of kinematic alignment technique in OUKA. Results: The mean follow-up was (70.9±5.9) months (60-81 months). The mean operation time was (56.4±9.1) minutes. There was no conversion to total knee replacement, no collateral ligament injury and no fracture in operation. The postoperative hospital stay was (5.8±1.9) days. Postoperative hemoglobin drop was (12.7±5.5) g/L. There was no blood transfusion. No patient died during perioperative period. No serious adverse events related to surgery occurred after operation, such as pulmonary embolism, fat embolism, cardio-cerebrovascular accident, etc. No revision, bearing dislocation, periprosthetic joint infection, prosthesis aseptic loosening, contralateral compartment arthritis progression occurred at final follow-up. Three patients reported persistent unexplained knee pain. Afther the operation, the HSS score increased from 59.1±8.2 to 91.8±5.6 after the operation, the range of motion increased from 122.4°±10.0° to 125.6°±7.1°, and the VAS score decreased from 6.9±0.8 to 1.6±1.2 (all P<0.05). Radiological assessment showed that 92.9%(91/98) implant positions were ideal and 7 knees were outliers. The mean HKAA was 173.3°±3.7° before surgery and it was 177.2°±3.0° after surgery (P=0.038). The mean A angle of femur varus/valgus angle was 2.0°±2.8° (-11°-13°), and the mean B angle of femur flexion/extension angle was 4.8°±3.4°(0°-17°). The mean tibia valgus/valgus angle E angle was 1.0°±1.9°(-4°-9°), and the mean F angle was 6.7°±2.3°(1°-12°). The mean postoperative prosthesis distance was (4.29±2.46)mm(2-7 mm). Conclusions: It's demonstrated that the kinematic alignment technique follows the design principle of OUKA, has satisfactory mid-term results. The radiological assessment of the prosthesis is acceptable.