Submuscular Versus Subcutaneous Anterior Ulnar Nerve Transposition: A Rat Histologic Study

PurposeThe 2 most common methods of ulnar nerve anterior transposition are submuscular and subcutaneous. Controversy exists as to which technique yields superior results. The purpose of this study was to examine the histologic differences between the 2 methods in a rat model.MethodsTwenty forelimbs in 10 adult Sprague-Dawley rats had bilateral ulnar nerve transpositions; one side with the submuscular method, and the other side with the subcutaneous method. Animals were killed 6 weeks after the index surgery and the forelimbs were examined for histologic evidence of the health of the axons and perineural scar formation.ResultsNerve health was assessed using a 4-part classification in which 4 = normal nerve, 3 = abnormal axons in one-third cross-sectional area (CSA), 2 = abnormal axons in two-thirds CSA, and 1 = abnormal axons in 100% CSA. Perineural scar formation was assessed using a 3-part classification in which 3 = scar completely encasing nerve, 2 = scar formation partially surrounding nerve, and 1 = no scar. The submuscular method displayed healthier ulnar nerve axons. In addition, the submuscular method displayed less perineural scar tissue.ConclusionsOn this basis of this rat model, the submuscular method of ulnar nerve anterior transposition displayed histologically healthier axons and less perineural scar tissue when compared to the subcutaneous method.