Establishing an imaging prediction model to predict the remaining life of knee joint for varus knee osteoarthritis patients

Purpose: This study aimed to establish a prediction model basing on onset age, gender, body mass index (BMI) and imaging measurements to predict the remaining life of knee joint for varus knee osteoarthritis patients, and to aid in patient selection and decision-making efforts regarding knee joint preservation and total knee arthroplasty (TKA). Methods Using data collected from our retrospective TKA database, 132 patients with varus knee osteoarthritis (153 knees) were included in the study. We focused on patients with a diagnosis of Kellgren–Lawrence (K-L) grade II in the initial stage of knee osteoarthritis (OA) accompanied by mild symptoms and a diagnosis of K-L grade IV with severe symptoms and TKA records at the endpoint. The interval between baseline and endpoint was defined as the remaining life of knee joint. The following imaging indexes of knee joints were assessed using standard anteroposterior (AP) radiography, medial proximal tibial angle (MPTA) and joint line convergence angle (JLCA) at baseline (MPTA 0 and JLCA 0 ) and at TKA period (MPTA T and JLCA T ); changes in MPTA and JLCA between baseline and TKA period (ΔMPTA and ΔJLCA); and rates of change in MPTA and JLCA between baseline and TKA period ( k MPTA and k JLCA). Meanwhile, basic information of patients was collected, including onset age, gender, body mass index (BMI). Multivariate linear regression analysis was performed for the prediction model about the remaining life of knee joint using statistically significant indexes. Results Multivariate linear regression analysis showed that, onset age, BMI, JLCA 0 , k MPTA and k JLCA were significantly negatively correlated with the remaining life of knee joint, which showed effectiveness in prediction model for TKA. Prediction model: remaining life of knee joint = 195.3–0.6×Onset age-2.0×BMI-4.4×JLCA 0 -159.9× k MPTA-205.5× k JLCA. Conclusions Onset age, BMI, JLCA 0 and rates of change in MPTA and JLCA robustly predict the risk of requiring TKA. Level of Evidence Retrospective Study Level III