Innervation of three weight-bearing areas of the foot: an anatomic study and clinical implications.

The aim of this cadaver study is to improve our knowledge on the anatomy of the sensory fibres of the three weight-bearing areas of the plantar region. Previous studies mainly focused on the innervation of the heel but the innervation of the other two weight-bearing areas over the most medial and lateral metatarses have been neglected and are not well known. The study was carried out on 10 feet of five male cadavers. The tibial nerve was dissected down to the fat pads over the heel and the first and fifth metatarsal heads under the microscope. The distances of the branching point of the tibial nerve and origins of the medial and inferior calcaneal nerves to a line drawn from the centre of the medial malleolus to the centre of the calcaneous were all measured. The tibial nerve was divided into two branches called the lateral and medial plantar nerves 23.45 mm proximal to the predefined axis. The medial plantar nerve passed underneath the abductor hallucis muscle and gave two sensory branches to the fat pad over the first metatarsal head. The lateral plantar nerve coursed beneath the abductor hallucis and flexor digitorum brevis muscles and supplied innervation of the fat pad over the fifth metatarsal head. The sensory innervation of the heel was provided by medial calcaneal and inferior calcaneal nerves. The medial calcaneal nerve originated from the tibial nerve 41.89 mm proximal to the axis. It divided into two or three branches innervating the fat pad over the heel. The inferior calcaneal nerve originated from the lateral plantar nerve (70%) or the medial calcaneal nerve (30%) 10.66 mm proximal to the axis. This study describes the sensory fibres to the heel and the previously neglected weight-bearing areas over the first and fifth metatarses. Reconstruction of defects in these areas is very difficult so every attempt should be made to protect the sensory fibres during any surgical procedure.