Flexor hallucis longus tendon branch test: Development and validation of a new method to assess anatomical variation of the tendinous slip.

Background: The flexor hallucis longus (FHL) muscle often has a tendinous slip with a variable number of branches. We aimed at developing the FHL branch test to determine the number of FHL branches.
Methods: In anatomical validation study, 6 intact cadavers were used. The toe flexion angles were measured while the FHL and flexor digitorum longus (FDL) were manually pulled individually. For electrophysiological studies, 4 healthy men participated. The FHL was electrically stimulated, and electromyography (EMG) of the FHL and FDL were recorded during the FHL branch test.
Results: The toe flexion angles' changes in the FHL pulling condition were equivalent with pulling FDL in toes with FHL branching. The electrical stimulation of the FHL produced similar flexion as the FHL branch test. EMG of the FHL was higher than FDL during the FHL branch test (p=0.036).
Conclusions: The FHL branch test could be used to evaluate the number of FHL branches.
(Copyright © 2019 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.)