Augmentation of tendon healing in an intraarticular bone tunnel with use of a bone growth factor

We hypothesized that an exogenous bone growth factor could augment healing of a tendon graft in a bone tunnel in a rabbit anterior cruciate ligament-r econstruction model. Seventy rabbits underwent bilateral anterior cruciate ligament reconstructions with a semitendinosus tendon graft. One limb recei ved a collagen sponge carrier vehicle containing a mixture of bone-derived proteins while the contralateral limb was treated with either no sponge or a sponge without bone-derived proteins. The reconstruction was evaluated at 2, 4, or 8 weeks with histologic, biomechanical, and magnetic resonance im aging analysis. Histologic analysis demonstrated that specimens treated wit h bone-derived proteins had a more consistent, dense interface tissue and c loser apposition of new bone to the graft, with occasional formation of a f ibrocartilaginous interface, when compared with control specimens. The trea ted specimens had significantly higher load-to-failure rates than did contr ol specimens. Treatment with bone-derived proteins resulted in an average i ncrease in tensile strength of 65%. The treated specimens were stronger tha n control specimens at each time point, but the difference was greatest at 8 weeks. On the basis of signal characteristics and new bone formation, mag netic resonance imaging was useful for predicting which limb was treated, t he site of failure, and the limbs with higher load-to-failure values. This study demonstrates the potential for augmenting tendon healing in an intraa rticular bone tunnel using an osteoinductive growth factor.