Tissue engineering for anterior cruciate ligament reconstruction: a review of current strategies

The anterior cruciate ligament (ACL) is one the most commonly injured ligaments of the knee. Chronic ACL insufficiency can result in episodic instability, chondral and meniscal injury, and early osteoarthritis. The intra-articular environment of the ligament precludes normal healing and surgical replacement of the injured ligament is often mandated to restore stability. Current surgical strategies include the use of local autograft or allograft tissues for ligament reconstruction. These procedures have yielded superior long-term clinical results yet have the potential for serious associated morbidities. Existing limitations have prompted ongoing research designed to engineer a replacement ligament that will parallel the native ACL in both its biologic properties and mechanical durability. Ligament engineering necessitates the use of appropriate source cells and a growth matrix to support cell proliferation and collagen synthesis. The identification of appropriate growth modulators including both biochemical factors and mechanical stimuli are requisites for successful tissue growth. The characterization of the elements essential for successful graft development represents a significant challenge for investigators. This review examines the current literature regarding the potential and limitations of ligament engineering and describes the development of a novel 3-dimensional scaffold and bioreactor system at our institution.