Quantifying in vivo laxity in the anterior cruciate ligament and individual knee joint structures

Abstract

A custom knee loading apparatus (KLA), when used in conjunction with magnetic resonance imaging, enables in vivo measurement of the gross anterior laxity of the knee joint. A numerical model was applied to the KLA to understand the contribution of the individual joint structures and to estimate the stiffness of the anterior-cruciate ligament (ACL). The model was evaluated with a cadaveric study using an in situ knee loading apparatus and an ElectroForce test system. A constrained optimization solution technique was able to predict the restraining forces within the soft-tissue structures and joint contact. The numerical model presented here allowed in vivo prediction of the material stiffness parameters of the ACL in response to applied anterior loading. Promising results were obtained for in vivo load sharing within the structures. The numerical model overestimated the ACL forces by 27.61–92.71%. This study presents a novel approach to estimate ligament stiffness and provides the basis to develop a robust and accurate measure of in vivo knee joint laxity.

Keywords:

• Knee joint
• passive laxity
• anterior cruciate ligament
• numerical modelling

Acknowledgements

The authors would like to greatfully acknowledge Richard Frayne and the Seaman Family MR Research Centre at the Foothills Hospital in Calgary Alberta for their contribution to this study.

Notes

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to gratefully acknowledge the sources that helped to fund this project, including the Natural Sciences and Engineering Research Council of Canada (NSERC), Alberta Ingenuity Fund (AIF), Canadian Institutes of Health Research (CIHR), Canada Research Chair Program, Alberta Heritage Foundation for Medical Research (AHFMR), Geomatics for Informed Decisions (GEOIDE) and National Centre of Excellence (NCE).