Mid-foot retinaculum: an unrecognized entity

Retinacula are thickenings of deep fascia in the region of joints that hold down the tendons preventing them from bowing out of position. In the region of ankle, number of such retinacula have been described. Retinacula like superior and inferior extensor retinacula have been described which hold down the tendons of leg muscles passing to the foot beneath them. As the extensor tendons of the leg have more distal attachment to the toes, the present study was conducted to ascertain the presence of any additional retinaculum in the mid-foot region, which would tie down the tendons for their effective action at the distal joints. The aim was also to determine the attachments of the retinaculum, if present as well as the structures passing beneath them. Fifty cadaveric feet were dissected carefully for this purpose. Presence of an additional extensor retinaculum distal to the inferior band of inferior extensor retinaculum in the mid-foot region was found in 22 feet. Besides the extensor tendons, medial terminal branch of deep peroneal nerve and dorsalis pedis artery was found to pass beneath the retinaculum. A partial or complete mid-foot retinaculum existed in the mid-foot region covering the tarsometatarsal joints in about half of study population. Functionally, this retinaculum may prevent bowstringing of the extensor tendons, clinically it may predispose to entrapment of deep peroneal nerve mimicking anterior tarsal tunnel syndrome.