Causes / typical injury mechanism: An Essex-Lopresti fracture is a triad injury pattern consisting of a radial head fracture, a distal radioulnar joint (DRUJ) dislocation, and an interosseus membrane (IOM) disruption. The mechanism of injury is axial compression along the longitudinal axis of the forearm, usually from a trauma (motor vehicle collision, fall from height on an outstretched extremity, etc).

Classic history and presentation: A patient will usually endorse trauma to the affected extremity, pain, and decreased range of motion at the elbow and/or wrist. The diagnosis often requires a high index of suspicion as it has been previously reported that only 20% of these injuries are fully diagnosed at the time of initial presentation. Occult radial head fractures may be difficult to detect on plain films and may be read as negative.

Prevalence: Radial head fractures account for up to 4% of all fractures and approximately one-third of all elbow fractures (it is the most common fracture of the elbow). Essex-Lopresti fractures make up a minority of these cases; it is a rare injury. One study found a 4% incidence of IOM disruption in patients with radial head fractures.

Pathophysiology: The radial head articulates with the capitellum at the elbow and is the primary longitudinal stabilizer of the forearm. The IOM and DRUJ are secondary longitudinal stabilizers of the forearm. The DRUJ includes the ulnar head and sigmoid notch of the distal radius at the level of the wrist, and this articulation is stabilized by the triangular fibrocartilage complex (TFCC). The IOM consists of 5 ligaments: the central band, distal oblique bundle, proximal oblique cord, accessory band, and distal oblique accessory cord. Of these, the central band is the most important in terms of forearm stabilization.

The usual mechanism of injury describes an axial compression force initially causing the radial head fracture. Without the bony support of the radial head, the continued loading of the forearm causes the radius to displace proximally, disrupting the secondary stabilizers of the forearm, the IOM and DRUJ. However, there are cadaveric studies that dispute this sequence of events; they demonstrated IOM disruption with separation of the radius and ulna initially, followed by radial head fracture and DRUJ dislocation. The IOM disruption can cause continued longitudinal instability of the forearm if the radial head fracture is not treated, which can manifest as positive ulnar variance leading to ulnar abutment syndrome. Additionally, accelerated radiocapitellar arthrosis can be seen due to increased axial load being transmitted through the radiocapitellar joint in the setting of chronic injury.