103 TRANSFER OF FEMORAL NERVE BRANCHES TO PUDENDAL NERVE BRANCHES REINNERVATES THE URETHRAL AND ANAL SPHINCTERS IN A CANINE MODEL AND IS FEASIBLE IN A CADAVER STUDY

Abstract

INTRODUCTION AND OBJECTIVES: Although we previously demonstrated that transfer of the genitofemoral nerve to vesical branches of the pelvic nerve reinnervates the canine urinary bladder after bladder, urethral sphincter and anal sphincter denervation by transection of the S2 and S3 spinal roots, reinnervation of the sphincters requires additional nerve transfer strategies. The goal of this investigation is to determine the feasibility of reinnervation of the urethral and anal sphincters by transfer of femoral motor nerve branches to pudendal nerve branches for functional sphincter reinnervation in a canine model and clinical feasibility in a cadaver study. METHODS: After bladder, urethral sphincter and anal sphincter denervation in 3 female canines, femoral nerve branches were mobilized bilaterally, attached by end to end anastomosis to the distal cut ends of the pudendal nerves as they emerged from Alcock’s canal and implanted with nerve cuff electrodes interfaced to radiofrequency micro-stimulators (RFMS). Eleven cadavers were dissected bilaterally to expose pudendal and femoral nerve branches. Pertinent landmarks and distances that could be used to locate these nerves were assessed and measured, as were nerve cross sectional areas. RESULTS: Activation of the 5 of 6 implanted RFMS induced increased urethral and anal sphincter pressure with stimulus intensity of 15 mAmp or greater. Retrograde tracing studies demonstrated labeling of the upper lumbar ventral and lateral horns of the spinal cord with fast blue from the urethra and fluoro ruby from the anal sphincter, 8% of which were dual labeled. In the cadavers, a long motor branch of the femoral nerve was followed into the distal vastus medialis muscle for a distance of 17.4 0.8 cm, split off from the main femoral nerve trunk and transferred medially and superiorly to the pudendal nerve in Alcock’s canal, a distance of 13.6 0.71 cm. This was performed using a perineal approach. The cross sectional area of the pudendal nerve was 5.64 0.49 mm, and the femoral nerve motor branch at the suggested transection site was 4.40 0.41 mm. CONCLUSIONS: In the canine model, both urethral and anal sphincters can be reinnervated with femoral to pudendal nerve transfer. In the cadaver study, use of a femoral nerve motor branch to the vastus medialis muscle for heterotopic nerve transfer to the pudendal nerve is surgically feasible, based on anatomical location and cross sectional areas.