Review Question - QID 4867

The combination of valgus, axial, and posterolateral rotatory forces (forearm supination) can result in a "terrible triad" injury of the elbow.

The key features of a terrible triad injury include a radial head fracture, coronoid fracture, and dislocation of the elbow. Disruption of the lateral collateral ligament complex often concomitantly occurs. While restoration of the bony anatomy is important for static stability, the key primary stabilizer that needs to be addressed is the lateral collateral ligament complex. In acute injuries LCL repair may be possible. In chronic injury, LCL reconstruction would need to be considered.

O'Driscoll et al. 1991, examined 5 patients with recurrent posterolateral rotatory instability of the elbow. They showed that by applying supination of the forearm with a valgus moment and an axial compression force to the elbow while it is flexed from full extension, this can demonstrate posterolateral rotatory instability of the elbow. The elbow is reduced in full extension and must be subluxated as it is flexed in order to obtain a positive test result (a sudden reduction of the subluxation).

O'Driscoll et al. 1992 looked at a cadaveric study of the elbow. They showed that external rotation and valgus moments with axial forces resulted in posterior dislocations in 12 of the 13 specimens when the anterior medial collateral ligament (AMCL) remained intact. Clinically, it valgus stability in pronation is demonstrated, the AMCL can be assumed to be intact.

Illustration A and B shows radiographs of a terrible triad injury. There is posterolateral dislocation of the elbow with associated radial head fracture, coronoid fracture.

Incorrect Answers:
Answer A: Extension-type supracondylar fractures typically occur with FOOSH injuries with posteriorly directed forces.
Answer B: Flexion-type supracondylar fractures typically occur with the elbow in flexion with an anterior directed force.
Answer C: Anterior olecranon fracture dislocation typically occurs with a direct high-energy blow that is applied to the posterior aspect of the forearm with the elbow in 90° flexion.
Answer D: Coronoid fracture, olecranon fracture and lateral collateral ligament injury typically occur with the arm positioned in supination, axial and VARUS moment forces.