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

Elise C Pegg, Francesco Mancuso, Mona Alinejad, Bernard H van Duren, John J O'Connor, David W Murray, Hemant G Pandit

OAI: oai:purehost.bath.ac.uk:openaire_cris_publications/e40c4adf-a5c2-4c8b-b70f-ee5b812a0934 • DOI: https://doi.org/10.1016/j.clinbiomech.2015.10.004

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 a mean 5-year follow-up. The purpose of 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° 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.

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.