Predictors of early aseptic loosening of prosthetic components following primary total knee arthroplasty

Background. Aseptic loosening of the knee prosthesis components is one of the most common causes of revision surgery. The acceptable range of angular values for postoperative alignment of the lower limb and the frontal positioning of the prosthetic components remains a subject of debate. The aim of the study — to identify the predictors of the early aseptic loosening of prosthetic components following primary total knee arthroplasty. Methods. The study group included 31 patients with aseptic loosening of prosthetic components. The comparison group consisted of 55 patients with no signs of loosening over a follow-up period of at least 8 years. Baseline characteristics (sex, age, body mass index, and operated side) were compared, along with preoperative and postoperative angular alignment of the lower limbs, specifically, the anatomical femorotibial angle (aFTA) and the hip-knee-ankle angle (HKA), as well as reference angles for prosthetic component positioning. Results. Patient age over 60.5 years and BMI over 27.5 were associated with a 2.9-fold and 2.6-fold increased risk of prosthetic loosening, respectively. Preoperative varus deformity, with an HKA angle exceeding 9.5° and an aFTA over 6.5°, increased the risk of loosening by 9.6 and 23.1 times, respectively. Postoperative residual deformity exceeding 0.5° in either direction, as measured by the aFTA, increased the risk of loosening by 8.7 times. Valgus positioning of the tibial component was associated with a 2.8-fold increased risk of component loosening. Conclusions. In elderly and overweight patients with pronounced varus deformity of the lower limb, personalized preoperative planning should be prioritized to prevent early aseptic loosening of prosthetic components. In cases where postoperative residual deformity or valgus positioning of the tibial component is detected, enhanced clinical follow-up with radiographic monitoring every 6 months is recommended. If radiolucent lines progress and pain is present, early consideration of revision surgery is advisable, as it may increase the likelihood of a successful conservative revision.