Feasibility of a femoral nerve motor branch for transfer to the pudendal nerve for restoring continence: a cadaveric study

Abstract

Object: Nerve transfers are an effective means of restoring control to paralyzed somatic muscle groups and, recently, even denervated detrusor muscle. The authors performed a cadaveric pilot project to examine the feasibility of restoring control to the urethral and anal sphincters using a femoral motor nerve branch to reinnervate the pudendal nerve through a perineal approach.

Methods: Eleven cadavers were dissected bilaterally to expose the 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: 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 the Alcock canal, a distance of 13.7 ± 0.71 cm. This was performed via a perineal approach. The cross-sectional area of the pudendal nerve was 5.64 ± 0.49 mm(2), and the femoral nerve motor branch at the suggested transection site was 4.40 ± 0.41 mm(2).

Conclusions: The 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.

Fig. 1

Location of the pudendal nerve. A: Diagram showing the location of the pudendal nerve (PN) in the Alcock canal (pudendal canal) located medial to the ischial tuberosity (IT) and lateral to the anus (An). After exiting the Alcock canal, the pudendal nerve divides into several branches that course to the anus, external urethral complex (U; nerve indicated by small arrows), and clitoris. The location of the femoral nerve (FN) on the anterior thigh is also indicated in the diagram. B: Photograph of the pudendal nerve (held by a needle driver) as it exits the pudendal canal. Its path toward the urethra (U) is indicated by the small arrows. The location of the ischial tuberosity (IT) is indicated by a large arrow. C: Enlarged photograph of the pudendal nerve as it exists the Alcock canal. Its path toward the urethra is indicated by the arrows. Note the several small branches from the pudendal nerve as it nears its terminal targets.

Fig. 2

Location of the femoral nerve and branches. A: Diagram showing the location of the femoral nerve (FN) and several of its branches in the anteromedial thigh prior to removal of the subcutaneous fascia. Note its relationship to the great saphenous vein (Gr Saph V). B: Photograph of a female cadaver showing the femoral nerve (elevated by forceps) exiting the femoral triangle medial to the rectus femoris (RF) and coursing inferiorly on the anterior thigh toward the knee. The medial relationship of the great saphenous vein to the femoral nerve is indicated. C: Enlarged photograph indicating the medial relationship of the femoral artery (FA) and great saphenous vein (Gr Saph V) to the femoral nerve (elevated by forceps), and the lateral relationship of the rectus femoris (RF) muscle to the nerve.

Fig. 3

Feasibility of transferring a motor branch of the femoral nerve to the pudendal nerve. A: Photograph of anterior thigh showing the location of a motor branch of the femoral nerve (FN, indicated by 2 string loops, and the surgeon’s hand). The location of the pudendal nerve (PN) within the perineum and its proximity to the femoral nerve are shown. B: Photograph of the anterior thigh and perineal regions showing the transfer of the femoral nerve branch (FN, string loop and arrow) from its anterior thigh position to the pudendal nerve (PN, string loop and arrow). C: Diagram showing the transfer of a femoral nerve branch to the proximal pudendal nerve as it exists from the Alcock (pudendal) canal. D: Photograph showing the transfer of a large branch of the femoral nerve from its original anterior location (Fem N, indicated by the dashed line at the right margins of image), medially across the thigh, to the site of the proximal pudendal nerve in the Alcock canal (small clip and large gray arrow). Large black arrow and metal marker indicate the location of ischial tuberosity (IT). An = anus.