Bone Morphogenetic Protein Enhancement of Tendon Healing in a Bone Tunnel
Abstract & Commentary
Synopsis: Bone morphogenetic protein can accelerate tendon healing in a bone tunnel in a dog model.
Source: Rodeo SA, et al. Use of recombinant human bone morphogenetic protein-2 to enhance tendon healing in a bone tunnel. Am J Sports Med 1999;27:476-488.
Rodeo and colleagues examined the hypothesis that bone morphogenetic protein (BMP) could be used to enhance bone ingrowth into the bone tunnel interface with a host tendon. They transplanted a long digital tendon into a tibial bone hole in 65 adult mongrel dogs. They also randomized the limbs to receive either BMP in an absorbable type I collagen sponge carrier or the sponge carrier alone. The animals were then sacrificed at intervals of 3, 7, and 10 days and 2, 4, and 8 weeks. The radiographic, histologic, histochemical, and biomechanical characteristics of the tendon-bone interface were all evaluated. Rodeo et al found evidence of more extensive bone formation around the tendon and closer bone apposition to the tendon in the BMP-treated group at all time intervals. Also, the BMP was given in two separate doses, and the lower protein dose was associated with superior healing. Rodeo et al conclude that BMP can accelerate the healing process involving a tendon transplant into a bone tunnel.
Comment by Stephen B. Gunther, MD
Graft site fixation is often the weak link in orthopedic operations that involve the transplantation of a tendon into a bone tunnel. Therefore, early healing of local bone to the tendon may alleviate potential problems of graft pull-out or slipping causing subsequent laxity. The idea of bone-enhancing proteins that could minimize these complications is appealing. This scientific experiment in dogs shows accelerated bone healing in the protein-treated group. Radiographic, histochemical, histologic, and biomechanical data are all consistent with accelerated bone formation in the BMP-treated group.
This type of protein modulation of bone healing is an appealing option for such cases as anterior cruciate ligament reconstruction and other types of tendon transplantation. BMP-soaked collagen sponges may enhance bone healing and thereby prevent graft stretching and fixation failure, as Rodeo and colleagues mentioned. However, allowing "earlier and more aggressive rehabilitation and earlier return to work" may not be advantageous at all. Dye and Chew have documented increased metabolic activity in these patients, which may lead to degenerative arthritis if aggressive work and sport are encouraged before restoring metabolic homeostasis.1 The cost of BMP and the collagen sponge would also have to be considered.
This is a well-designed scientific experiment that does demonstrate increased bone production in the protein-enhanced specimens and does offer many possibilities for the future.
Reference
1. Dye SF, Chew MH. Restoration of osseous homeostasis after anterior cruciate ligament reconstruction. Am J Sports Med 1993;21:748-750.
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