Development of tissue engineered ligaments with titanium spring reinforcement†
Tissue engineering offers a promising alternative to the use of autografts in the treatment of ligament injuries. However, current approaches using only biodegradable materials have insufficient mechanical strength for load bearing applications. In this research, hybrid bio-artificial ligaments were fabricated using a combination of a titanium alloy spring and a fibrin gel/fibroblast construct. The ends of the ligament prosthesis were incorporated into brushite cement anchors to allow fusion with the host bone. Cell attachment to the titanium spring was examined using scanning electron microscopy and fluorescent staining of cells. The unreinforced constructs were observed to fail at the anchor–ligament junction, while the titanium spring reinforcement was found to assist in even transmission of the load to the ligament, and hence to provide a means of load sharing between the biological construct and the spring. As a result, the reinforced construct failed primarily in the soft tissue region. The good load distribution features from the mechanical data was attributed to the good cellular level adhesion to, and alignment along the coiling of, the length of the spring reinforcement. Incorporation of a biocompatible reinforcement in conjunction with a tissue engineered construct gave improved load distribution, reducing stress concentrations, and significantly increased the ultimate strength at failure. The results suggest that the hybrid approach used here shows promise in developing improved therapies for connective tissue injuries.