Use of recombinant human bone morphogenetic protein-2 to enhance tendon healing in a bone tunnel

This study examines the hypothesis that recombinant human bone morphogeneti c protein-2 can enhance bone ingrowth into a tendon graft placed into a bon e tunnel. We transplanted the long digital extensor tendon into a drill hol e in the proximal tibia in 65 adult mongrel dogs. We applied two different doses of the bone morphogenetic protein to the tendon-bone interface in one limb using an absorbable type I collagen sponge carrier and only the colla gen sponge to the contralateral (control) limb. The healed tendon-bone atta chment was evaluated at serial times between 3 days and 8 weeks using radio graphy, histologic examination, and biomechanical testing. At all time poin ts, histologic and radiographic examination demonstrated more extensive bon e formation around the tendon with closer apposition of new bone to the ten don in the protein-treated limb than in the paired control limb. Biomechani cal testing demonstrated higher tendon pull-out strength in the protein-tre ated side at all time points, with a statistically significant difference b etween the low-dose-treated side and the control side at 2 weeks. The histo logic and biomechanical data suggested superior healing at the lower protei n dose. This study demonstrated that bone morphogenetic protein can acceler ate the healing process when a tendon graft is transplanted into a bone tun nel.