The posterior femoral cutaneous nerve contributes significantly to sensory innervation of the lower leg: an anatomical investigation

Abstract Background Incomplete peripheral nerve blocks distal to the popliteal region are commonly considered a sciatic and femoral/saphenous nerve block failure. The existence of a much more distal innervation area of the posterior femoral cutaneous nerve (PFCN) as described has not been assumed yet. We therefore investigated the distal termination of the PFCN in the lower leg. Methods In 83 human lower extremities embalmed with Theil's method, the course of the PFCN was investigated from the sub-gluteal fold to the most distal macroscopically dissectible branch. The topographic connection to other landmarks, such as the small saphenous vein or small arteries, was investigated. Results Popliteal ending of the PFCN was found in 9.7% of cases. The PFCN terminated at the proximal or distal lower leg in 45.7% and 44.6% of cases, respectively. The PFCN had a close connection to the Achilles tendon in 13.2% of cases and was found distally to the medial malleolus in one case. The small saphenous vein was close to the PFCN in 90.3% of cases and can therefore be used as a landmark to identify the nerve. In 40.9% of cases, the PFCN was accompanied by a small descending branch of the inferior gluteal artery. In two cases, an innervation of the fibula or calcaneus periosteum was found. Conclusions The PFCN has a much more distal termination in the lower leg than previously demonstrated. To ensure complete anaesthesia of the lower leg and foot, the PFCN must be included in combined peripheral nerve block procedures.