Posttraumatic widening of the lateral aspect of the radiohumeral joint space on unstressed anteroposterior elbow radiograph: a predictive sign of elbow instability

We present a case of incomplete or perched irreducible elbow dislocation, which occurred spontaneously into cast immobilisation performed for a diagnosis of "elbow sprain". Initial anteroposterior unstressed elbow radiograph revealed a subtle widening of the lateral aspect of the radiohumeral joint space. Because of the unusual irreducibility of this subluxation, the patient underwent surgical exploration which showed the lateral collateral ligament complex and capsule to be interposed into the radiohumeral joint space and interfering with elbow reduction. This case report intends to draw attention on the radiographic sign of widening of the radiohumeral joint space on the unstressed anteroposterior elbow radiograph as a predictive sign of instability and to document the anatomic lesion that leads to this presentation.