Tissue engineering of knee ligaments

Knee ligament injuries are the most common injury sustained in major sports with anterior cruciate ligament (ACL) and medial collateral ligament (MCL) tears accounting for more than 27% of the knee injuries combined. The gold standard for treatment of ligament injuries remains controversial. Non-operative methods can result in decreased strength and prolonged recovery while surgery does not ensure graft incorporation and return to pre-injury function. Tissue engineering technology incorporates biological, chemical, engineering and materials science principles, and can facilitate ligament healing. The purpose of this article is to review current tissue engineering approaches for knee ligament injuries. Intra-articular ligaments, such as the ACL and posterior cruciate ligament (PCL) experience a very different environment than extra-articular ligaments such as the MCL and LCL. Therefore, the approach to healing in these two areas are different. Tissue engineering related to ligament healing consists of three components: cells, scaffolds, and the healing environment. So far, neither an ideal cell source or optimal scaffold has been established. Biological environment modification is in its clinical infancy, and is currently being investigated to address the appropriate stimulation through the application of growth factors. The mechanical environment, in turn, can be reasonably optimized by performing ligament reconstruction surgery in an anatomic fashion. Through advances in tissue engineering, surgeons may one day be able to offer solutions to help patients return to their desired activities faster and stronger.