The relationships between the quadratus plantae and the flexor digitorum longus and the flexor hallucis longus.

ABSTRACT

PURPOSE: The purpose of this research was to clarify the relationships between quadratus plantae (QP) and flexor digitorum longus (FDL) and flexor hallucis longus (FHL) using large-scale specimens. METHODS: This study examined 116 legs from 62 Japanese cadavers. The QP was classified as Type I, formed by the lateral and medial heads; Type II, the lateral head is absent; and Type III, the medial head is absent. The FHL branches to the lesser toes were classified as Type A, connection from FHL to toe 2; Type B, connection from FHL to toes 2 and 3; Type C, connection from FHL to toes 2-4. Next, the relationships between QP and FHL and FDL were observed. RESULTS: Type I accounted for 87%, Type II for 10%, and Type III for 3%. Type A accounted for 33%, Type B for 53%, and Type C for 14%. Regarding the relationship between QP and FDL, regardless of the classification of the connections of the FHL tendon slip to the lesser toes, QP attachments to FDL branching to toes 2, 3, and 4 were seen in 47-59%. Furthermore, QP attachments to FDL branching to toes 2, 3, 4, and 5 were seen in 41-47%. CONCLUSIONS: QP appears to function strongly to counter the oblique pull of FDL and FHL and as a lesser digit plantar flexor.