| The studies herein document the efforts to describe the behavior of the soft tissue in response to distraction osteogenesis, and investigate the usefulness of botulinum toxin (type A) treatment during the procedure. Distraction osteogenesis is a surgical procedure used to lengthen a bone, and the process often induces complications in the surrounding soft tissues. One of the more debilitating complications encountered during tibial elongation is contracture about the ankle. Botulinum toxin administration has been used to help ankle contractures caused by other pathologies, and experiments were conducted to explore its efficacy in treating distraction induced contracture.; The tibias of New Zealand White rabbits were lengthened with a distraction rate and final elongation selected to generate the complications reported during limb lengthening. Each experiment lasted eight weeks after which the animals were sacrificed. Data were gathered before, during, and after the experiment. Their muscles and tendons were harvested and analyzed using various biomechanical, histological and immunchistochemical tools.; Distraction impaired muscle strength of the tibialis anterior by 80%, but had no effect on the gastrocnemius. Toxin injection worsened the loss in target muscles and provided a slight improvement in the antagonist. Distraction alone caused a loss in range of motion from 150° to 57°. When botulinum toxin was injected into the gastrocnemius muscle, dorsiflexion was increased to a total range of 75°; when injected into the tibialis anterior, plantarflexion was increased to a total range of 85°. Distraction also caused morphological changes such as atrophy, increased intramuscular connective tissue, increased mitotic activity and rounded muscle fibers. Injection of botulinum toxin reduced mitotic activity in the opposing un-injected muscle, but elicited additional fibrosis and atrophy in target muscles.; Distraction also adversely affected tendon elastic and viscoelastic properties. Botulinum toxin injection impaired the muscle into which it was injected, while improving the biomechanical properties of the corresponding tendon. Injection of the toxin induced fibrosis and caused muscle weakness and atrophy; however, it improved the range of motion in a joint with contracture. These studies demonstrate that there is a trade off between the benefit and harm provided by botulinum toxin in treating muscles undergoing distraction osteogenesis. |
