Unilateral absence of an extensor digitorum longus muscle and variations of toe tendons

Author(s): Bruce W. Newton*

The extensor digitorum longus and brevis (EDL, EDB) muscles, along with the extensor hallucis longus and brevis, extend the toes. During routine dissection in our anatomy course, the author found the EDL muscle and tendons were absent in the right leg; but the left leg had a small EDL muscle with a single fifth toe tendon. The left EDL also gave rise to a fibularis tertius muscle. In the right foot, the EDB had a variant tendon slip to the fifth toe that crossed superficial to its tendon to the fourth toe. The left EDB had an extra muscle belly whose tendon inserted on the second toe by crossing an additional EDB tendon to the second toe. Each foot had a fibularis digiti minimi tendon arising from the fibularis brevis. The lack of an EDL muscle and/or tendons may have caused this person to have foot drop during the swing phase of walking, as well as causing unexpected problems for surgeons who use EDL tendons for grafts.

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