A positive correlation exists between intra- and post-operative kinematics of a Posterior Stabilized total knee arthroplasty: preliminary analysis

Introduction Since aberrant kinematics has been claimed as possible reason for dissatisfaction after Total Knee Arthroplasty (TKA), to detect specific kinematical patterns in unsatisfied patients it is crucial to improve their outcomes. Recently some kinematical patterns have been detected however the further step should be detect intra-operatively the “abnormal” patterns and to prevent it. To reach this goal it is necessary to merge different technologies in order to couple the intra-operative kinematics with the post-operative one. The aim of this study is to compare the passive flexion-extension kinematics acquired intra-operatively during a TKA surgery and to compare it with the post-operative flexion-extension one acquired during a sit-to-stand motor task. Material and method A cohort of 25 patients has been prospectively recruited and underwent intraoperative kinematic assessment with a commercial navigation system before and after Posterior-Stabilized TKA implantation. So far 5 patients underwent the post-operative evaluation at minimum 9 months follow-up with model based Dynamic RSA during the execution of the sit-to-stand. A correlation analysis has been conducted between the varus-valgus rotations (deg) at 0° and 30° of flexion, the antero-posterior translations at 90° of flexion acquired intra operatively and varus-valgus and AP acquired post-operatively. Results Statistically significant correlation (p<0.05) was found for VV a 30° of flexion (r=0.78, strong), AP a 90° of flexion (r=0.83, strong), and VV at 0° of flexion (r=0.37, poor). Interpretation and conclusion The findings of the present study confirm that intra-operative and post-operative kinematical parameter are comparable, and that positive strong correlation exists between VV rotations at 30° and AP translations at 90°. As a consequence of this finding, the intra-operative kinematic data could be used to detect kinematic pattern that are typical of unsatisfied patients in the post-operative period and therefore correct it during the operation.