In vivo forces during remodeling of a two‐segment anterior cruciate ligament graft in a goat model

Abstract

An existing goat model was used to measure in vivo graft forces during walking, to determine if the forces set at surgery change over time under the same external load and if the forces in the graft during in vivo function can be dictated by the forces set at surgery. The anterior cruciate ligament was reconstructed in 12 goats with use of a composite graft consisting of a bone-patellar tendon-bone autograft and a synthetic augmentation segment. The forces in the graft segments were established intraoperatively by a force-setting technique. In five animals, the tendon segment was set to carry 90% of the total graft force, and in the seven other animals, the augmentation segment was set to carry 90% of the total force. The total graft force was the same in all animals. Graft forces due to anterior tibial loads of 67 N were measured before and after fixation and 6 weeks after surgery with the use of buckle transducers mounted extra-articularly over the anterior tibia. They were also measured during straight, level walking at 6 weeks. The forces changed significantly from just after surgery to 6 weeks later, such that the initially set load-sharing was eliminated by 6 weeks. At 6 weeks, a relatively smooth gait had been achieved, and the maximum total graft force in each animal during walking averaged 35 N and was of similar magnitude to forces generated by the anterior tibial loads of 67 N with the animal anesthetized. After fixation, forces in the tendon graft segments were significantly different between the group with high set forces and that with low set forces. At 6 weeks, when functional joint loads were approaching normal levels, the graft segment forces for the two groups were not significantly different. Load-sharing between tendon and augmentation segment and load in the tendon segment at 6 weeks could not be dictated at surgery.

Three-Dimensional Engineered Bone–Ligament–Bone Constructs for Anterior Cruciate Ligament Replacement

“…The sheep and goat have commonly been chosen as animal models for the knee [30][31][32][33] because of anatomical [34][35][36][37] and mechanical [38][39][40][41] similarities to human ACLs. These sheep were obtained from the Michigan Livestock Exchange, various farms in the area or intra-university transfer.…”

Estimation of ACL Forces Utilizing a Novel Non-Invasive Methodology That Reproduces Knee Kinematics Between Sets of Knees

“…Buckle transducers measure the force in the ACL by relating strain caused by the deflection of the transducer to tension in the ACL 19,20 . Pressure transducers are surgically implanted within one of the functional bundles of the ACL relating pressure to force 21 .…”

“…However, the literature provides contradictory and, in many cases, uncertain conclusions as to the force and function of the ACL in vivo [19][20][21][22][23][24][25][26][27][28] . In particular, there is little scientific data available to guide postoperative rehabilitation, which can range from conservative to aggressive.…”

Estimation of ACL forces by reproducing knee kinematics between sets of knees: A novel non-invasive methodology

“…During the last decade, a number of studies have been performed to estimate the in situ forces in the ACL in vivo (Holden et al, 1994;Lewis et al, 1994;Lundberg et al, 1997;Zacharias et al, 2001Zacharias et al, ,2000. While providing valuable information, each methodology requires measurements that are difficult to obtain using human subjects.…”