Phenotyping patients undergoing total knee arthroplasty with full body clinical gait analysis

The phenotyping of patients undergoing total knee arthroplasty (TKA) aims at identifying patient’s profiles to plan and target patient-specific treatments, and provide personalised information before surgery. Up to date, the identification of functional phenotypes focused on knee kinematics and kinetics during gait [1]. Classification of patient’s phenotypes based on full body kinematics during gait could help to understand typical patient’s compensation. Which functional phenotypes can be indentified from the full-body kinematics during gait before surgery for patients undergoing TKA? And, do their clinical outcome differ one-year post-surgery? 79 patients with end-stage osteoarthritis and planned for primary TKA (69.5±7.4 years, 1.64±0.1 m, 81.0±14.9 kg) were included. Patients had two visits: before and one year after surgery. Each visit included clinical gait analysis [2] and patient reported outcomes (WOMAC, SF12, pain during gait, satisfaction after one year). Long axis X-rays were performed before surgery. Patient’s were clustered with the K-means method on the lower limb joints, pelvis and thorax angles time-series. The optimal number of clusters was identified with the silhouette criterion [3]. Differences between phenotypes were assessed with statistical parametric mapping [4] for the kinematics, with one-way ANOVA and post-hoc Student’s t-test for clinical differences of continuous variables and with Chi-square test to compare proportions.Download : Download high-res image (170KB)Download : Download full-size image Three clusters were selected with the main kinematic differences based on the pre-operative deformity of the lower limb in the frontal plane. One cluster was in varus, one in valgus and one had a neutral alignment. The ANOVA showed a group effect on sex, gait speed before and after surgery, and on the pre-surgery anatomical axis. The varus group had 50% females, presented more hip abduction and had higher walking speed pre- and post-surgery. The valgus group had over 80% females. The neutral cluster was characterized by over 90% females, higher pelvic retroversion and reduced hip flexion, typical of elderly gait. There were no significant differences between groups in terms of age, satisfaction, WOMAC, SF12, pain, BMI, and proportion of bilateral affection. The full-body analysis of gait kinematics identified three phenotypes of end-stage OA patients. Two profiles seem related to mechanical sources of joint wear due to misalignment of the knee with one varus (50% females) and one valgus group (>80% female). The last group had neutral knee alignment and was characterized by >90% females, with patterns typical of elderly gait but with no significant difference in age. Analysis of the time-series of gait kinematics was strongly influenced by gender, since two out of three groups were mainly females. A higher statistical power may help characterising better those groups in terms of clinical parameters. As previously underlined in the litterature, differences in gait kinematics do not necessarily relate to differences in PROMs function score [5].