Posterior Femoral Cutaneous Nerve Block

The posterior femoral cutaneous nerve (PFCN), also referred to as the posterior cutaneous nerve of the thigh, is a sensory nerve that derives from the sacral plexus (S1, S2, and S3). The main descending branch of the PFCN is approximately 2 mm diameter in the proximal thigh and has a relatively straight course, which is nearly parallel to the sciatic nerve. The PFCN and the sciatic nerve are separated by the long head of the biceps femoris muscle (the PFCN runs over the posterior surface, whereas the sciatic nerve runs underneath the muscle). Perineal branches of the PFCN that innervate the medial thigh and lateral perineum arise 2 to 4 cm distal to the ischial tuberosity. Recurrent branches of the PFCN form the inferior cluneal nerves that supply the gluteal region. End branches of the PFCN travel with the small saphenous vein in the proximal posterior leg.

Potential indications for PFCN block include surgical procedures of the posterior thigh (above the knee), skin graft harvests from the posterior thigh, diagnostic and therapeutic blocks, and perhaps thigh tourniquet tolerance.

PFCN and lateral femoral cutaneous nerve (LFCN) blocks may be a way of improving thigh tourniquet tolerance without concomitant motor block (in combination with other blocks of the lower extremity). PFCN block has limited utility in clinical anesthesia, because few surgeries have an incision on the posterior thigh (above the knee amputation is one exception).