Sagittal kinematics of mobile unicompartmental knee replacement in anterior cruciate ligament deficient knees

Journal article

Background: There is a greater risk of tibial component loosening when mobile unicompartmental knee replacement is performed in anterior cruciate ligament deficient knees. We previously reported on a cohort of anterior cruciate ligament deficient patients (n=46) who had undergone surgery, but no difference was found in implant survivorship at mean 5 year follow-up. The purpose this study was to examine the kinematic behaviour of a subcohort of these patients. Methods: The kinematic behaviour of anterior cruciate deficient knees (n=16) after mobile unicompartmental knee replacement was compared to matched intact knees (n=16). Sagittal plane knee fluoroscopy was taken while patients performed step-up and forward lunge exercises. The patellar tendon angle, knee flexion angle and implant position was calculated for each video frame. Findings: The patellar tendon angle was 5° lower in the deficient group, indicating greater anterior tibial translation compared to the intact group between 30 and 40 degrees of flexion. Large variability, particularly from 40-60 degrees of flexion, was observed in the bearing position of the deficient group, which may represent different coping mechanisms. The deficient group took 38% longer to perform the exercises. Interpretation: Kinematic differences were found between the deficient and intact knees after mobile unicompartmental knee replacement; but these kinematic changes do not seem to affect the medium-term clinical outcome. Whether these altered knee kinematics will have a clinical impact is as yet undetermined, but more long-term outcome data is required before mobile unicompartmental knee replacement can be recommended for an anterior cruciate ligament deficient patient.

Authors: Pegg, E; Mancuso, F; Alinejad, M; van Duren, B; O'Connor, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Clinical Biomechanics
• Volume: 31
• Pages: 33-39
• Publication date: 2015-10-22
• DOI: 10.1016/j.clinbiomech.2015.10.004
• ISSN: 1879-1271
• Keywords: anterior cruciate ligament; unicompartmental knee replacement; function; patellar tendon angle; knee kinematics