Grants We Funded

Abstract
Project Summary: Nerves stimulate muscles to perform desired movements. When a nerve can no longer communicate with a muscle, that muscle cannot function, leading to considerable disability. For patients with hand dysfunction caused by irreparable nerve injury, tendon transfers provide an opportunity to regain lost function. A tendon transfer works by connecting the tendon of a functioning muscle to the tendon of a denervated muscle, allowing the functioning muscle to pull the nonfunctioning tendons and, thus, return hand motion. Patients who have sustained an injury to the radial nerve lose the ability to extend the wrist and fingers, making it hard to pick up objects. One common tendon transfer used to recover wrist extension connects the pronator teres (PT) tendon, which turns the hand palm up, to the extensor carpi radialis brevis (ECRB) tendon, which extends the wrist. When the PT muscle contracts, it pulls on the ECRB tendon, causing wrist extension. The PT tendon is quite short; in order to reach the ECRB tendon, PT tendon length can be extended by harvesting the adjacent periosteum. However, in some adults, the periosteal tissue is thin and not sturdy enough to maintain a strong connection when woven with the ECRB tendon. In these instances, the ECRB tendon can be lengthened, through a technique called “turnover” tendon lengthening. The elongated ECRB tendon can then be successfully woven together with the PT tendon to join the two tendons. There are no published reports of a turnover-lengthened tendon being used for a tendon transfer. Thus, the goal of this project is to investigate the strength of the turnover-lengthened tendon alone (Specific Aim 1) and when used for tendon transfer (Specific Aim 2). Successful tendon transfer and resultant hand function requires that the tendon transfer resist day-to-day physiologic forces and sudden high loads without stretch or rupture. We will use a uniaxial materials testing machine to exert low-level and high-level forces on lengthened ECRB tendons and PT to ECRB tendon transfers to determine if this method is equivalent to or stronger than traditional non-lengthened tendon transfers. These studies will be performed using cadaveric tendons. Future studies will examine the long-term outcomes of the lengthened tendon transfer in patients. Impact Statement: This study will enhance our knowledge of the biomechanical properties of a lengthened tendon, using the turnover technique, as well as the role of tendon lengthening in tendon transfers for patients with permanent nerve injury. The ability to dramatically lengthen a tendon without compromising tendon strength will also provide support for the use of a lengthened tendon to bridge tendon gaps caused by traumatic hand injury.

Biography
Dr. Erin Weber is a Hand Fellow in the Department of Orthopaedics at the University of Pennsylvania. She is trained in Plastic and Reconstructive Surgery and has also earned a Ph.D. in Biochemistry, with a focus on viral vector design, and completed a postdoctoral fellowship in human hair follicle tissue engineering. Her clinical interests include surgery of the hand and upper extremity, microsurgery, and peripheral nerve injury. Her most recent research efforts have focused on improving the regenerative capacity of processed nerve allografts through Schwann cell seeding.