Review Question - QID 4333

Clinical episodes of posteromedial rotatory instability are most commonly associated with fractures of the anteromedial facet of the coronoid.

Coronoid injuries are pathognomonic of an elbow instability event. In episodes of severe varus stress, the shear forces exerted on the coronoid by the distal humerus lead to injury. The anteromedial facet, which is important for varus stability, is subsequently fractured. When combined with lateral collateral ligament complex injury, posteromedial rotatory instability results.

O’Driscoll et al. review treatment of coronoid fractures as part of a review on management of difficult elbow injuries. They indicate that anteromedial coronoid injuries are representative of varus posteromedial rotatory instability injuries. In the setting of coronoid injury, the radial head assumes a critical role in elbow stability.

Tashjian et al. review the etiology, diagnosis, and management of complex elbow instability. In their discussion of coronoid fractures, they indicate that identification of anteromedial facet injuries is often difficult and that treatment should be instituted promptly to limit persistent instability and subsequent arthritis.

Illustration A shows an AP radiograph of the affected elbow. An event of posteromedial instability is evidenced by the fracture through the anteromedial facet of the coronoid. Illustrations B and C show the AP and lateral radiographs of a patient who developed significant arthrosis after inadequate treatment of varus posteromedial rotatory instability.

Incorrect answers
Answers 1, 3, 5: These injuries may be seen as the sequlae of posterolateral rotatory instability.
Answer 4: Large coronoid fractures are seen in olecranon fracture-dislocations around the elbow.