Review Question - QID 1366

The superomedial fragment of an intra-articular calcaneus fracture is also referred to as the sustentacular fragment (Illustrations A and B). Additionally, the flexor hallucis longus (FHL) tendon wraps inferiorly around this piece within an osseus groove (illustration C).

In their CT analysis of acute calcaneal fractures, Gilmer et al describe that the superomedial piece typically does not move in these fractures due to its strong ligamentous attachments to the talus. For this reason, it is commonly referred to as the "constant fragment." The superomedial fragment is important during ORIF of calcaneal fractures, because fixation from the lateral side is typically based off this "constant" fragment as a guide to provide anatomic fixation.

The reference by Berberian et al also reviews the CT findings of 100 consecutive calcaneus fractures, and reports that the sustentacular fragment was displaced in forty-two of the 100 fractures. This brings into question the nature of the "constant fragment" possibly being less of a constant finding as we previously thought.

Illustration D shows the classification and position of these fractures.

Incorrect Answers:
Answer 1: This fragment does not typically move due to the Achilles tendon pull.
Answer 3: The fragment does not typically stay in place due to navicular attachments.
Answer 4: This fragment does not typically displace in these directions.
Answer 5: The posterior tibial tendon does not wrap directly inferiorly to this piece of bone.