[Existence of a retinaculum musculorum extensorum immum in man]

The considerable variability of the Mm. extensor hallucis longus et brevis and the medial portion of the M. extensor digitorum brevis reflects the higher strain acting on the medial part of the forefoot. These functional conditions result probably not only in the increased development of the muscles mentioned above but also in the formation of a Retinaculum musculorum extensorum imum, which does, in fact, occur in 64.2% of extremities examined. 2 major forms of this retinaculum can be differentiated: A Retinaculum musculorum extensorum imum fibrosum (52.3%) and musculofibrosum (11.9%). The fibrous form again occurs in 2 varieties, namely a complete (47%) and an incomplete (5.3%) one.