Efficacy of intervention strategies in a brachial plexus global avulsion model in the rat

The treatment of brachial plexus avulsion lesions invariably involves the use of neurotization procedures. Although some of these therapeutic strategies have been used for the past 20 years to restore selective function to the injured extremity, the individual efficacy of these nerve transfers has not been measured objectively, thereby rendering the prognostication of outcomes for these techniques a major problem. Using a true global avulsion model, the present study compares outcomes of the various neurotization procedures for the first time. The strength of this experimental model is that each nerve transfer tested leads to a common terminal pathway involving a single target-namely, the biceps muscle. Thus, quantitative measurements of biceps restoration will provide strong clues to the power of axonal regrowth of that particular motor pool. This study also introduces the Terzis grooming test, a modified behavioral test that can be quantified and that can provide an overall functional scale in the assessment of outcome. Thirty-five Sprague-Dawley rats were divided into seven groups, with each group testing a different motor donor for biceps reinnervation. The ipsilateral brachial plexus was globally avulsed in all animals, with the exception of the ipsilateral C7 group, and the respective motor donor coapted in an end-to-end fashion to the musculocutaneous nerve. Functional outcomes were measured by the Terzis grooming test, electromyography, biceps muscle force measurements, motor end plate counts, and quantitative axonal morphometry. The values of the different parameters were expressed as a standard score on a common scale. The relative standings of each group on each parameter were compared. Superior outcome was observed in the phrenic, the hypoglossal, and the ipsilateral C7 groups.