Determinant Factors for the Postoperative Range of Motion After Primary Total Knee Arthroplasty

Abstract

This study aims to describe and identify determinants for the postoperative RMA progression after a primary total knee arthroplasty (pTKA).

Prospective study in patients with knee osteoarthritis who underwent pTKA. Patients were operated by the same surgical team, implant, and followed the same rehabilitation protocol. Exclusion criteria included a follow-up of less than six months. The RMA (extension-flexion) was evaluated preoperatively, during the hospital stay, and postoperatively (first, third and sixth months). Functional and satisfactory RMA were established as 5-95º and 0-120º, respectively. Statistical analysis included mixed models for association between postoperative RMA and demographic, pre, intra, and postoperative non-related surgical technique variables (p < 0.05).

Fifty patients (53 pTKA), median age 68 (49-91), 75.5% females. At six months, 100% of patients presented with functional RMA, and 72.2% with satisfactory RMA. A threshold of 105º of flexion at the third postoperative month, was statistically significant for identifying patients who achieved an acceptable RMA at six months (sensitivity = 97.1%; specificity = 75%).

The postoperative RMA progression was determinant for a satisfactory RMA at six months after pTKA. A threshold of 105º of flexion at the third postoperative month has an excellent accuracy to identify patients who will not achieve an acceptable RMA.