FLEXOR TENDON HEALING

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Annually, more than 300,000 upper extremity injuries in the U.S. require operative treatment for repair of tendons injured in their midsubstance or at their insertion sites. These injuries lead to an estimated loss of 4 million workdays. Recent improvements in the treatment of flexor tendon midsubstance injuries have been driven by advances in the scientific understanding of repair and rehabilitation variables. By contrast, there have been no significant changes in the treatment of flexor tendon insertion-site injuries in several decades, in part because there have been few scientific investigations to support such changes. As a result, many patients have a poor clinical outcome after repair of the flexor tendon insertion site, as evidenced by decreased range of motion and loss of grip strength. Our long-term objective is to identify repair and rehabilitation techniques that will consistently produce excellent clinical function for immediate and delayed treatment of flexor tendon insertion-site injuries. In this project, we will apply a canine model of flexor tendon insertion-site injury and repair to investigate several clinically relevant variables that have not been previously addressed: 1) suture technique for reattachment of tendon to bone, 2) increased tendon force and excursion applied during rehabilitation, 3) time interval from injury to repair, and 4) growth factor enhancement of tendon-bone healing. Our primary hypothesis is that the stiffness and strength of the repair site are improved by application of increased tendon force during early, passive motion rehabilitation. In addition, we hypothesize that healing of the tendon-bone repair site can be accelerated by delivery, at the time of repair, of targeted gene products that enhance expression of growth factors that are important to early tissue healing. These include: basic fibroblast growth factor (bFGF), platelet- derived growth factor (PDGF) and vascular endothelial growth factor (VEGF). A multidisciplinary approach will be utilized for evaluation of the experimental variables, with biomechanical, histological and biochemical outcomes analyzed. The final determination of practical benefit will be based on biomechanical assessment of digital range of motion and repair-site stiffness and strength during the critical first 6 weeks of healing. Identification of improved repair and rehabilitation techniques for insertion-site injuries will be an initial step toward modernizing clinical treatment and improving patient outcomes.