Recutting the distal femur to increase maximal knee extension during TKA causes coronal plane laxity in mid-flexion

Abstract

The aim of this study was to quantify the effects of distal femoral cut height on maximal knee extension and coronal plane knee laxity.Seven fresh-frozen cadaver legs from hip-to-toe underwent a posterior stabilized TKA using a measured resection technique with a computer navigation system equipped with a robotic cutting guide. After the initial femoral resections were performed, the posterior joint capsule was sutured until a 10° flexion contracture was obtained with the trial components in place. Two distal femoral recuts of +2mm each were then subsequently made and the trials were reinserted. The navigation system was used to measure the maximum extension angle achieved and overall coronal plane laxity [in degrees] at maximum extension, 30°, 60° and 90° of flexion, when applying a standardized varus/valgus load of 9.8 [Nm] across the knee.For a 10 degree flexion contracture, performing the first distal recut of +2mm increased overall coronal plane laxity by approximately 4.0° at 30° of flexion (p=0.002) and 1.9° at 60° of flexion (p=0.126). Performing the second +2mm recut of the distal femur increased mid-flexion laxity by 6.4° (p<0.0001) at 30° and 4.0° at 60° of flexion (p=0.01), compared to the 9 mm baseline resection (control). Maximum knee extension increased from 10° of flexion to 6.4° (± 2.5° SD, p<0.005) and to 1.4° (± 1.8° SD, p<0.001) of flexion with each 2mm recut of the distal femur.Recutting the distal femur not only increases the maximum knee extension achieved but also increases coronal plane laxity in midflexion.

View details for DOI 10.1016/j.knee.2012.05.007

View details for Web of Science ID 000311329300027

View details for PubMedID 22727760