Risk Factors for Postoperative Knee Stiffness in Patients with Anteromedial Knee Osteoarthritis Undergoing Unicompartmental Knee Arthroplasty with Cemented Prostheses: A Short-Term, Retrospective, Case-Control Study

Background: The present study was performed to determine the potential risk factors for postoperative knee stiffness in patients with anteromedial knee osteoarthritis undergoing unicompartmental knee arthroplasty with cement-ed prostheses. Material/Methods: This retrospective cohort study evaluated patients with anteromedial knee osteoarthritis who underwent me-dial unicompartmental knee arthroplasty at our hospital between May 2017 and May 2020. The patients were divided into 2 groups according to their prognosis: those who experienced knee stiffness after undergoing uni-compartmental knee arthroplasty and those who did not. The factors associated with stiffness after UKA were identified using univariate analysis. Frequencies are used to express categorical variables, while mean +/- SD is used to express continuous variables. The t test and chi-square test were used. A multivariate logistic regres-sion model was built to identify the risk factors for postoperative stiffness. Results: We included 590 knees in the study after unicompartmental knee arthroplasty. The overall incidence of post-operative stiffness in unicompartmental knee arthroplasty surgery was 10.17%. In terms of the radiological measurements, varus deformity (70.34% vs 29.66%) and tibial component posterior slope angle (4.8 +/- 2.0 vs 4.6 +/- 2.0, P<0.001) were significantly differences between the 2 groups. Four independent risk factors for stiff-ness after unicompartmental knee arthroplasty were identified: age (95% CI, 1.022-1.048), varus deformity (95% CI, 1.186-1.192), tibial component posterior slope angle (95% CI, 0.550-0.870), and preoperative maxi-mum flexion (95% CI, 0.896-0.923). Conclusions: The overall incidence of postoperative knee stiffness in patients with anteromedial knee osteoarthritis under-going unicompartmental knee arthroplasty with cemented prostheses was 10.17%, which was at a moderate level compared to patients with other diseases undergoing unicompartmental knee arthroplasty. Four inde-pendent risk factors were identified: age, varus deformity, preoperative maximum flexion, and tibial compo-nent posterior slope angle. Awareness these risk factors might help surgeons prevent the occurrence of post-operative knee stiffness in patients with UKA.