The spin move to facilitate antegrade coronoid fixation in terrible triad injuries

The role of the coronoid process in elbow instability has been established. When necessary, coronoid fixation can be challenging. Placing fixation perpendicular to the fracture requires achieving a trajectory as close as possible to the midline axis of the proximal ulna, either from anterior to posterior or vice versa. The aim of this study was to determine whether coronoid exposure-and the ability to place fixation from anterior to posterior-is improved via a lateral extensor-splitting approach with forearm supination, that is, the "spin move," with progressive stages of lateral elbow instability.

The lateral extensor-splitting approach was performed on 9 cadaveric upper extremities. A 0.157-mm (0.062-inch) wire was drilled perpendicularly into the lateral aspect of the humerus just proximal to the lateral epicondyle. A second wire was drilled into the tip of the coronoid, aiming for a drill trajectory as close as possible to the midline axis. The angle between the 2 wires was measured as the initial angle. Three stages of progressive lateral elbow instability were produced by sequential release of the lateral ulnar collateral ligament (LUCL), common extensor origin (CEO), and posterior capsule. At each stage, the spin move was performed and the angle between the 2 wires was measured. The difference between this angle and the initial angle was calculated, with the average value reported as the Δ angle for each stage. The average difference between each stage and the next stage was reported.

The spin move resulted in Δ angles of 10.3° with the LUCL released, 20° with the CEO released, and 29.1° with the posterior capsule released. Progressing from LUCL release to CEO release to posterior capsule release, the Δ angle between the K-wires increased an average of 9.6° from the LUCL stage to the CEO stage and 9.1° from the CEO stage to the posterior capsule stage.

The spin move is a simple maneuver that can improve exposure of the coronoid process regardless of the degree of elbow instability. This may facilitate a more perpendicular screw, bone tunnel, or suture anchor trajectory via the lateral approach, reducing the need for posterior-to-anterior fixation. The improved exposure is inferred from the differences in the K-wire angles with and without the spin move. This study has also quantified the change in coronoid exposure using the angles of the wires with progressive release of the LUCL, CEO, and posterior capsule. If necessary, releasing the CEO or posterior capsule with eventual repair may allow improved coronoid fixation from the lateral approach.