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

• Published in: The knee Vol. 19; no. 6; pp. 875 - 879
• Main Authors: Cross, Michael B, Nam, Denis, Plaskos, Christopher, Sherman, Seth L, Lyman, Stephen, Pearle, Andrew D, Mayman, David J
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.12.2012; Elsevier Limited
• Subjects: Adult; Aged; Arthroplasty, Replacement, Knee - adverse effects; Arthroplasty, Replacement, Knee - methods; Cadaver; Distal femur; Female; Femur - surgery; Humans; Joint Capsule - physiopathology; Joint Capsule - surgery; Joint Instability - etiology; Joint Instability - physiopathology; Joint line elevation; Knee extension; Knee Joint - physiopathology; Knee Joint - surgery; Male; Middle Aged; Midflexion laxity; Models, Biological; Orthopedics; Range of Motion, Articular - physiology; Recut; Knee extension; Midflexion laxity; Distal femur; Joint line elevation; Recut
• ISSN: 0968-0160; 1873-5800
• DOI: 10.1016/j.knee.2012.05.007

Abstract Background The aim of this study was to quantify the effects of distal femoral cut height on maximal knee extension and coronal plane knee laxity. Methods 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 + 2 mm 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. Results For a 10 degree flexion contracture, performing the first distal recut of + 2 mm 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 + 2 mm 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 2 mm recut of the distal femur. Conclusions Recutting the distal femur not only increases the maximum knee extension achieved but also increases coronal plane laxity in midflexion.