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 morphogenetic protein-2 can enhance bone ingrowth into a tendon graft placed into a bone tunnel. We transplanted the long digital extensor tendon into a drill hole 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 collagen sponge to the contralateral (control) limb. The healed tendon-bone attachment was evaluated at serial times between 3 days and 8 weeks using radiography, histologic examination, and biomechanical testing. At all time points, histologic and radiographic examination demonstrated more extensive bone formation around the tendon with closer apposition of new bone to the tendon in the protein-treated limb than in the paired control limb. Biomechanical testing demonstrated higher tendon pull-out strength in the protein-treated side at all time points, with a statistically significant difference between the low-dose-treated side and the control side at 2 weeks. The histologic and biomechanical data suggested superior healing at the lower protein dose. This study demonstrated that bone morphogenetic protein can accelerate the healing process when a tendon graft is transplanted into a bone tunnel.