Biological response to a new composite polymer augmentation device used for cruciate ligament reconstruction

A resorbable composite augmentation cord braided of poly(L-lactide) and poly(L-lactide-co-glycolide) fibers was designed for the temporary protection of repaired cruciate ligaments. This study examined the biocompatibility of the new device and the influence of augmentation duration on ligament healing in a sheep model. The anterior cruciate ligament (ACL) was cut close to the femoral insertion and reinserted with sutures. The repaired ACLs were augmented with the slowly degrading new composite cord and alternatively with a faster degrading polydioxanone cord (PDS). A tendon graft group (gold standard) served as control. Histological evaluation and biomechanical testing were performed after 6 months. The composite cord showed no signs of degradation, whereas the PDS was intra-articularly resorbed. Both devices showed only minor foreign body reactions, proving their good biocompatibility. However, 9 of 11 composite cords had ruptured too early because of fatigue at the bone tunnel entrances. All operated knees were less stable than the nonoperated collateral joints. Knees equipped with the composite cord showed the largest anterior instabilities, whereas the PDS-augmented group exhibited in some cases knee instabilities comparable with that of the tendon group. A positive effect of a longer mechanical protection by a slowly degrading augmentation could not yet be shown. The fatigue strength of the device still needs improvement.