Introduction
Coronoid Fractures are typically associated with other fractures and dislocations around the elbow. Elbow stability may be compromised secondary to these fractures if not addressed adequately. Coronoid fractures typically occur during falls on an outstretched hand and it has been proposed that the trochlea imparts a shearing force at the time of injury. The brachialis was thought to cause avulsions, however, authors feel that its attachment to the base of the coronoid discounts this mechanism of injury.
Anatomy
The coronoid is a triangular prominence on the proximal volar surface of the ulna. Its surfaces provides attachments for the brachialis, collateral ligaments, and several flexor tendons. Posterior to the coronoid is the semilunar notch which is the articulating surface for the trochlea. Thus, the coronoid acts as an important bony stabilizer while also providing important origin and attachment points for the soft tissue stabilizers of the elbow.
Classification
Regan and Morrey:
Type I: Avulsion of the tip of the coronoid process
Type II: Fracture involving less than 50% of the coronoid
Type III: Fracture involving more than 50% of the coronoid
Presentation
These patients will typically present after a fall on an outstretched hand and will likely have concurrent fractures or dislocations. The patient will have a swollen elbow and depending on concurrent fractures and dislocations will be unable to flex or extend the elbow. A complete neurovascular exam is mandatory with these types of elbow injuries.
Diagnosis
After a thorough history and physical exam, taking time to assess the patient's neurovascular status, anteroposterior, lateral, and oblique radiographs can help to delineate the fractures and/or dislocations. Greenspan, or radiocapitellar radiographs, are recommended to clear the radial head from the coronoid process. CT scans are not a necessary part of the workup, but can add further anatomic detail in fracture assessment and management.
A dislocated elbow should be reduced and once the patient's elbow is in an acceptable anatomic position, an assessment of stability should be performed.
Treatment
Stable Type I and II coronoid fractures can be treated nonoperatively. Early range of motion can be initiated depending on any concurrent fractures and dislocations. Type III coronoid fractures require open reduction and internal fixation. Fixation can be achieved utilizing anteroposterior or posteroanterior screw fixation. In addition, sutures can be utilized in the soft tissue to reapproximate the coronoid fragment. Techniques involving reconstruction of highly comminuted coronoid fractures utilizing a piece of the radial head or olecranon have also been described in the literature. Finally, external fixation can be utilized if the elbow remains unstable.
Complications
Potential complications include and are not limited to neurovascular injury, loss of motion, chronic instability, and heterotopic ossification.
Red Flags and Controversies
One should be aware, as Ring et al indicated, that coronoid fractures associated with ulnohumeral dislocations are characteristically different from those associated with complex proximal ulna fractures.
Ring D, Jupiter JB, Sanders RW, Mast J, Simpson NS. Transolecranon fracture dislocation of the elbow. J Orthop Trauma. 1997; 11: 545-50.
Outcomes
Post operative immobilization and large coronoid fractures tend to have a less optimal outcome.
Regan W, Morrey B: Fractures of the coronoid process of the ulna. J Bone Joint Surg Am 1989 Oct; 71(9): 1348-54
Ring D, Jupiter JB, Zilberfarb J: Posterior dislocation of the elbow with fractures of the radial head and coronoid. J Bone Joint Surg Am 2002 Apr; 84-A(4): 547-51
