Over Constraint Varus Valgus Laxity Leads to Worse Clinical Outcomes at Long Term Follow Up in Total Knee Arthroplasty: Intraoperative Assessment through Surgical Navigation System

The purpose of the present study was to associate the intraoperative kinematics acquired with a computer navigation system with long-term clinical outcomes and survivorship in patients undergoing TKA to investigate the role of constraint in patients’ satisfaction.A surgical navigation system was used to verify bone resections, gaps, and implant positioning during TKA. Kinematic examination, i.e. varus-valgus at full-extended knee (VV0), varus-valgus at 30° of flexion (VV30), anterior/posterior displacement at 90° of flexion (AP90), passive range of motion (ROM) were performed. Long-term clinical assessment interviews were performed. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to investigate patients’ clinical and functional status.Out of 165 patients, 120 met the inclusion criteria. The average follow-up time was 7.7±2.8 years. 7 patients had undergone revision surgery and were considered as a surgical failure with an overall survival rate of 94.2%, while the survival rate at 6, 8, 10 years was 98.8%, 97.4%, 93.6%, respectively. Clinical failure (KOOS score <70) was detected in 11 (9.2%), 10 (8.3%), 21 (17.5%), 39 (32.5%), 113 (94.2%) patients for the Symptoms, Pain, ADL, QoL, and Sport sub-scores, respectively. A statistically significant difference was found in KOOS-QoL between patients with and without clinical failure for the VV0 test (ES=0.58, p=0.022), with lower laxity for patients with score<70.Over-constraint kinematics during TKA surgery leads to worse clinical outcomes at long-term follow-up. Surgeons should be aware of the intraoperative ligament balancing and avoid over-constraint, especially in PS TKA designs.