Review Question - QID 3836

A known complication of fractures of the sustentaculum tali is stenosis (delayed) or injury (acute) of the flexor hallucis longus (FHL) tendon. Stenosis can cause pain and popping with great toe flexion.

Fractures of the calcaneus often occur after falls from height, and in addition, may be associated with vertebral fractures due to the high-impact mechanism. The FHL tendon runs directly underneath the sustentaculum tali on the medial calcaneus and can be injured causing frank tears or delayed stenosis. These fractures may be missed on ankle or foot plain films alone, and advanced imaging should be ordered if clinical suspicion for calcaneus fractures exists given mechanism and location of pain/swelling.

Komiya et al. present a case report of direct impalement of the FHL tendon in the tunnel under the sustentaculum tali. Though this particular complication is quite rare, such a report highlights the relevant anatomy and structures at risk as well as demonstrates the need for a good clinical exam as the injury was not noted on imaging but the concern was raised on physical exam of FHL involvement.

Della Rocca et al. report their 19-patient series on operatively managed isolated sustentaculum tali fractures. They report a high rate of associated ipsilateral foot injuries (14 patients) and describe fixation using a medial approach and retracting the flexor tendons and neurovascular bundle.

Illustration A is an axial CT image from Della Rocca (2009) et al. showing a representative sustentaculum tali fracture

Incorrect Answers:
Answer 1 - beak fractures are posterior, anatomically related to the Achilles tendon insertion, not the FHL tendon.
Answer 2 - FHL tendon is not associated with the tuberosity.
Answer 3 - FHL tendon runs anterior to the posterior facet and would unlikely be involved in that injury.
Answer 5 - FHL tendon runs medially, not laterally.