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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 a mean 5-year follow-up. The purpose of this study was to examine the kinematic behaviour of a subcohort of these patients.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.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° of flexion. Large variability, particularly from 40-60° 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.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.

Original publication

DOI

10.1016/j.clinbiomech.2015.10.004

Type

Journal article

Journal

Clinical biomechanics (Bristol, Avon)

Publication Date

01/2016

Volume

31

Pages

33 - 39

Addresses

Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom. Electronic address: elise.pegg@ndorms.ox.ac.uk.

Keywords

Anterior Cruciate Ligament, Patellar Ligament, Tibia, Knee Joint, Humans, Joint Instability, Fluoroscopy, Range of Motion, Articular, Arthroplasty, Replacement, Knee, Case-Control Studies, Aged, Aged, 80 and over, Middle Aged, Female, Male, Biomechanical Phenomena