KNEE JOINT LIGAMENT RECONSTRUCTION: ON PRETENSION AND COUPLING IN CRUCIATE LIGAMENTS

Wide range of knee cruciate ligament reconstruction procedures with different materials, stiffness, pretensions, orientations, and insertion locations are currently used with the primary goal to restore the joint laxity. With the general lack of success in preservation of force in the reconstructed ligament, the concern, not yet addressed, arises as to the effect of reconstruction on the other intact cruciate ligament. Using a 3-D finite element model, we examined this hypothesis by varying the pretension in each ligament under flexion ±A-P loads and quantifying the extent of coupling between cruciate ligaments. A remarkable coupling was predicted. Moreover, changes in laxity and in ligament forces as ligament pretension was altered varied with flexion and loads. These findings have important consequences in proper management and rehabilitation of the joint ligament disorders

Finite Element Analysis of Bone and Experimental Validation

This chapter describes the application of the finite element (FE) method to bone tissues. The aspects that differ the most between bone and other materials’ FE analysis are the type of elements used, constitutive models, and experimental validation. These aspects are looked at from a historical evolution stand point. Several types of elements can be used to simulate similar bone structures and within the same analysis many types of elements may be needed to realistically simulate an anatomical part. Special attention is made to constitutive models, including the use of density-elasticity relationships made possible through CT-scanned images. Other more complex models are also described that include viscoelasticity and anisotropy. The importance of experimental validation is discussed, describing several methods used by different authors in this challenging field. The use of cadaveric human bones is not always possible or desirable and other options are described, as the use of animal or artificial bones. Strain and strain rate measuring methods are also discussed, such as rosette strain gauges and optical devices.publishe

Barriers to Predicting the Mechanisms and Risk Factors of Non-Contact Anterior Cruciate Ligament Injury

High incidences of non-contact anterior cruciate ligament (ACL) injury, frequent requirements for ACL reconstruction, and limited understanding of ACL mechanics have engendered considerable interest in quantifying the ACL loading mechanisms. Although some progress has been made to better understand non-contact ACL injuries, information on how and why non-contact ACL injuries occur is still largely unavailable. In other words, research is yet to yield consensus on injury mechanisms and risk factors. Biomechanics, video analysis, and related study approaches have elucidated to some extent how ACL injuries occur. However, these approaches are limited because they provide estimates, rather than precise measurements of knee - and more specifically ACL - kinematics at the time of injury. These study approaches are also limited in their inability to simultaneously capture many of the contributing factors to injury