Review Question - QID 216855

Patients with posteromedial rotatory instability of the elbow present with fractures of the anteromedial facet of the coronoid.

Posteromedial rotatory instability of the elbow is typically associated with a fall backwards onto an outstretched arm, resulting in varus stress across the elbow and progressive pronation of the forearm. This results in fracture of the anteromedial coronoid facet, which often require open reduction internal fixation. In addition, the lateral collateral ligament is typically compromised. This is identified as widening of the radiocapitellar joint during preoperative dynamic fluoroscopic examination. In this scenario, direct repair of the lateral collateral ligament complex should also be performed to produce a stable elbow. If instability remains after fixation, a dynamic external fixator may be utilized to gain stability.

Karbach et al review elbow instability and the related anatomy, biomechanics, diagnostic maneuvers, and testing. They report that varus posteromedial rotatory instability results following an axial and valgus load with the forearm in pronation, which causes a fracture to the anteromedial facet of the coronoid and a rupture of the LCL. They conclude that dynamic fluoroscopic examination under anesthesia is the gold standard for evaluation of widening at the ulnouhmeral joint.

Bellato et al review the role of the lateral collateral ligament in posteromedial rotatory instability of the elbow. They report that widening of the radiocapitellar joint was only identified in those specimens in which the LCL was sectioned. They concluded that the LCL lesion was required for elbow subluxation to occur.

Wyrick et al review the management of complex elbow dislocations via a mechanistic approach. They report that posteromedial rotatory instability occurs via a varus load that ruptures the LCL complex and causes the trochlea to fracture the anteromedial facet of the coronoid as the deformity progresses. A fluoroscopic evaluation under general anesthesia may reveal varus instability, with a widened lateral joint space and medial joint collapse. They conclude that these findings suggest that both the LUCL complex and the coronoid require surgical intervention.

Illustration A demonstrates the location of various coronoid fractures, including that of the anteromedial facet.

Incorrect Answers:
Answer 1 & 4: Coronoid tip fractures are associated with posterolateral rotatory instability, which often occurs in conjunction with radial head fractures.
Answer 3: Disruption of the medial elbow generally occurs through the anteromedial facet of the coronoid, not the medial epicondyle.
Answer 5: Olecranon fractures are not part of the injury pattern for varus posteromedial instability.