Coronoid Fracture


Practice Essentials

Fractures of the coronoid rarely occur in isolation. They are often seen as a part of complex elbow fracture dislocations, usually involving a radial head fracture, a dislocation of the elbow, or both (terrible triad of the elbow) [123; rarely, they may be seen in conjunction with high Monteggia fractures. Large coronoid fractures often are associated with persistent elbow instability even after reduction of the dislocation. There has been a trend toward fixation of these injuries to restore stability and facilitate initiation of an early range-of-motion (ROM) program. [456789]

Images depicting the elbow joint can be seen below.

Elbow joint, anterior view. Elbow joint, anterior view.
Elbow joint, posterior view. Elbow joint, posterior view.

Type 1 and most type 2 fractures (see Workup) usually are managed nonoperatively and do not require operative stabilization. Highly comminuted type 3 fractures pose a significant problem during open reduction and internal fixation (ORIF) and may be better treated with a hinged external fixator. A displaced coronoid fracture that presents with a block to elbow motion is a definite indication for surgical stabilization.

Anatomy

The coronoid acts as the anterior buttress of the greater sigmoid notch of the ulna. It provides attachment to the anterior band of the medial collateral ligament (MCL) and the middle portion of the anterior capsule. The anterior colliculus of the MCL is the primary stabilizer of the elbow against valgus strain in the functional arc of 20-120° of flexion. This ligament is most likely to become injured with a low coronoid fracture with the elbow in full extension. [10A fracture of the coronoid, therefore, results in the loss of all of these supports.

The brachialis muscle is attached to the base of the coronoid process. [11Dissection of the brachialis during fixation of these fractures contributes to the risk of heterotopic ossification in these cases.

Pathophysiology

Morrey et al, in their biomechanical study of the elbow, concluded that approximately 50% of the elbow stability comes from the congruent articulation between the trochlea and the ulna. [12]

Closkey et al studied the stabilizing function of the coronoid process under axial load to the elbow. [13They found no significant difference, at any flexion position, in posterior axial displacement between intact elbows and elbows in which 50% or less of the coronoid process was fractured (types 1 and 2; see Workup). Differences in posterior axial displacement were significant, across all flexion positions, between intact elbows and elbows in which more than 50% of the coronoid process was fractured (type 3).

The authors concluded that in response to axial load, elbows with a fracture involving more than 50% of the coronoid process displace more readily than elbows with a fracture involving 50% or less of the coronoid process, especially when the elbow is flexed 60º and beyond. [13]

Etiology

Coronoid fractures were believed to result from avulsion of a bony fragment of the coronoid by the brachialis, which inserts onto the coronoid process. This, however, does not explain the mechanism of type 1 and some type 2 fractures, as the brachialis attaches to the base of the coronoid process of the ulna. (See Workup, Imaging Studies, for a discussion of fracture types.) These fractures probably occur from shear forces at the time of the dislocation when the trochlea pushes off a piece of the coronoid.

Epidemiology

Coronoid fractures account for fewer than 1-2% of all elbow fractures. They have been identified in 10-15% of elbow dislocations. [1415Radial head fractures are seen in about 5-10% of elbow dislocations. [16Coronoid fractures, especially with large fragments, are associated with more instability and an increased incidence of complications.

Prognosis

The prognosis for a complex fracture dislocation of the elbow is definitely poorer than that for a simple elbow dislocation, which has been shown to have good long-term results. [17181920]

Prognostic factors include the following:

  • Size of the fragment - Type 3 fractures have the worst prognosis, with only 20% having good results in the series presented by Regan et al [14]
  • The degree of damage to the articular cartilage at the time of injury
  • The extent of soft-tissue injury [21]
  • The stability obtained at the time of reduction
  • The duration of immobilization


History and Physical Examination

Coronoid fractures are usually seen in patients with elbow dislocations. The patient usually presents with a history of a fall on the outstretched hand and a deformity of the elbow.

The presence of an unstable reduction is suggestive of an associated coronoid or radial head fracture. An irreducible dislocation, on the other hand, should arouse suspicion of soft-tissue (brachialis, median nerve) or bony (medial epicondyle) interposition in the joint.

Distal vascularity and neurologic status should always be tested in these cases.

In children, coronoid fractures have a bimodal age distribution, with peaks at age 8-9 years and at age 12-14 years. [23 Coronoid fractures in children are often associated with elbow dislocations, olecranon fracturesmedial epicondyle fractures, or lateral condyle fractures.

In children younger than 6 years, Blasier described an unusual flap injury of the unossified coronoid in which the elbow is dislocated and a small flap of the articular surface gets flipped back into the joint. [24 This usually appears on the lateral radiograph as a small flake of bone in the anterior portion of the joint. This flake is a clue to the underlying pathoanatomy and the extent of injury.



Radiography

Radiographs of the elbow in the anteroposterior (AP), lateral, and, if required, oblique views should be obtained to provide a clear assessment of the extent of bony injury. Oblique views are especially important in minimally displaced fractures because in a true lateral view, the radial head overlaps the coronoid. To avoid this problem, Greenspan and Norman described the radiocapitellar view, in which the elbow is flexed to 90º and placed flat on the table with the x-ray beam directed obliquely toward the shoulder. [2526 This separates the radial head from the coronoid.

Regan and Morrey classified coronoid fractures depending on the size of the fragment, as follows [14:

  • Type 1 - Avulsion of the tip of the coronoid process (see the first image below); Linscheid et al do not believe this to be an avulsion, in that the brachialis is attached to the base of the coronoid [16]
  • Type 2 - Single or comminuted fragment involving less than 50% of the coronoid (see the second image below)
  • Type 3 - Single or comminuted fragment involving more than 50% of the coronoid (see the third image below)
Type 1 coronoid fracture: avulsion fracture at tipType 1 coronoid fracture: avulsion fracture at tip of coronoid.
Type 2 coronoid fracture: unstable elbow fracture Type 2 coronoid fracture: unstable elbow fracture dislocation with fracture involving <50% of coronoid height and associated radial head fracture.
Type 3 coronoid fracture: fracture involving >50% Type 3 coronoid fracture: fracture involving >50% of coronoid height.

CT and MRI

Computed tomography (CT) may be useful in complex fracture dislocations to delineate the fracture patterns and for preoperative planning. [2728]

Rhyou et al studied rates of associated ligamentous injury in isolated and combined coronoid fractures and found the following [29:

  • Complete lateral ulnar collateral ligament rupture (94.1%)
  • Complete medial collateral ligament rupture (17.6%)
  • Medial bone contusion (70.6%)
  • Lateral bone contusion (17.6%)

For magnetic resonance imaging (MRI) findings in elbows with a radial head fracture, see Kaas et al.



Approach Considerations

Type 1 and most type 2 fractures (see Workup) usually are managed nonoperatively [31​ and do not require operative stabilization. [32 Highly comminuted type 3 fractures pose a significant problem during open reduction and internal fixation (ORIF) and may be better treated with a hinged external fixator. [33 A displaced coronoid fracture that presents with a block to elbow motion is a definite indication for surgical stabilization. [34]

In the past, coronoid fractures were treated with a longer period of immobilization (3-4 weeks) in greater degrees of flexion, and this was believed to be a better alternative than operative treatment. However, with increasing understanding of the contribution of the coronoid to stability of the elbow, there has been a trend toward operative stabilization of these injuries and initiation of an early protected range-of-motion (ROM) program to avoid the most dreaded complication of these injuries, which is stiffness.

However, after studying 58 patients over an 8-year period, Kiene et al concluded that surgical therapy could not be statistically justified, particularly if the patient underwent therapy with an external fixator, immobilization for more than 3 weeks, and complications and unstable osteosyntheses. [35]

Medical Therapy

Nonoperative treatment is indicated for type 1 and type 2 injuries. This includes closed reduction of the dislocation and splinting in a moderate degree of flexion for a short period (< 3 weeks) before initiation of a program of protected mobilization of the elbow.

Surgical Therapy

For type 3 fractures or those occurring in conjunction with other injuries about the elbow resulting in instability, operative management is typically required. [36 There are several approaches to management, including the following:

  • ORIF
  • Suture lasso fixation
  • Closed reduction with percutaneous pinning
  • External fixation
  • Arthroscopically assisted closed reduction and internal fixation

The authors’ preferred operative method, when feasible, is ORIF, as described below. If the fragment is too comminuted for internal fixation, then a hinged external fixator should be applied across the elbow and a protected ROM program should be started. [37]

The ultimate goal of surgery for these fractures should be restoration of a stable arc of elbow motion within the functional range (30-130º).

Preparation for surgery

Adequate preoperative imaging studies should be carried out to ascertain the exact fracture anatomy. This typically includes complete radiographs and computed tomography (CT) of the elbow. Magentic resonance imaging (MRI) may be useful for evaluating soft-tissue structures but typically is not required.

Skin condition must be evaluated because severe soft-tissue injury and swelling may be present.

Operative details

There are several surgical approaches that allow visualization of the coronoid. If an associated radial head fracture has occurred, the coronoid can be approached through the radial head fracture site via a laterally based incision.

If the radial head is intact, the coronoid can be approached via a medial incision, through the floor of the cubital tunnel. This is accomplished by identifying and protecting the ulnar nerve and then elevating the flexor carpi ulnaris (FCU) and the flexor pronator group from distal to proximal until the sublime tubercle is visualized. Once the MCL (medial collateral ligament) has been protected, the coronoid fracture can be addressed.

Finally, if both medial and lateral work is being performed on the elbow, a posterior incision can be used, and the coronoid can be accessed through either of the aforementioned approaches by raising full-thickness flaps.

In the case of a Monteggia type fracture-dislocation, the coronoid may be approached through the interval between the extensor carpi ulnaris (ECU) and the anconeus laterally and the FCU medially. The radial head may be approached between the anconeus medially and the ECU laterally. Using this dual-interval approach reduces the risk of synostosis formation between the radius and the ulna.

In transolecranon fracture-dislocations, the coronoid may be approached through the olecranon fracture by displacing the proximal piece proximally; fixation may then be achieved with headless compression screws and subsequent operative fixation of the olecranon.

After exposure of the fracture site, the hematoma should be evacuated, and the edges of the fracture should be cleaned to facilitate anatomic reduction. Fixation may be achieved by means of several methods, including the following:

  • Use of an interfragmentary screw (from posterior to anterior or, if the fragment is small or osteoporotic, from anterior to posterior)
  • Plate-and-screw fixation (see the first and second images below)
  • If the piece is small, the suture lasso technique, whereby suture anchors or bone tunnels stabilize the fracture [3839(see the third image below)
Status post open reduction and internal fixation oStatus post open reduction and internal fixation of coronoid with plate-and-screw construct. Courtesy of Kenneth Egol, MD.
Second example of plate-and-screw constructs for fSecond example of plate-and-screw constructs for fixation of type 3 coronoid fracture. Courtesy of Kenneth Egol, MD.
Status post open reduction and suture fixation of Status post open reduction and suture fixation of coronoid, as evidenced by drill holes in proximal ulna. Sutures are used as a lasso to capture coronoid fragment, passed through ulnar drill holes, and tied over posterior ulna bony bridge. Patient is also status post radial head replacement for comminuted radial head fracture. This is an example of typical operative management of "terrible triad" elbow injuries.

As noted above, the goal of any fixation should be a stable construct that allows early ROM. (See the image below.)

Chronic elbow fracture dislocation presentation fiChronic elbow fracture dislocation presentation films with type II coronoid fracture (left) and fixation films (right). Fixation consisted of radial head replacement and suture lasso fixation of coronoid fracture. Since the elbow remained unstable throughout the range of motion, a hinged external fixator was placed.

The results from one study noted that suture lasso fixation of coronoid fractures for terrible triad injuries results in fewer complications and greater stability compared with screw or suture anchor fixation techniques. [40A higher rate of implant failure was noted with internal screw fixation, whereas the suture anchor technique resulted in a higher rate of malunion and nonunion.

Giannicola et al studied 18 patients in whom coronoid fractures were repaired with fine-threaded Kirschner wires (K-wires). [41After 26 months, results were excellent in 10 patients, good in seven, and fair in one, according to the Mayo Elbow Performance Index. The authors concluded that this technique was an easy, minimally invasive, stable, and successful procedure for obtaining osteosynthesis in patients with coronoid fractures and complex elbow instability.

A study by Ouyang et al described the use of a novel arthroscopic portal for coronoid visualization, followed by placement of an anterior-to-posterior screw for fracture fixation. [42In this series, all fractures healed without displacement and there were no cases or neurovascular injury. 

In patients with highly comminuted coronoid fractures or chronic lesions resulting in unstable elbows, reconstruction using a piece of the radial head (Esser technique) or a piece of the olecranon (Moritomo technique) has been described. [43 Gray et al studied the effect of a prosthesis on restoring stability to the coronoid-deficient elbow by analyzing eight cadaveric arms. [44They concluded that the use of an anatomic implant restores stability and deserves further study.

Postoperative Care

Immediately after the operation, the elbow is immobilized at 90° of flexion in a well-padded posterior splint for comfort. The neurovascular status of the upper limb is monitored closely for the fist 24 hours. At the earliest sign of neurovascular dysfunction, encircling dressing and bandages should be loosened, and compartment pressures should be monitored for signs of compartment syndrome.

The goal of fixation is a stable and preserved functional arc of motion. Accordingly, splints are typically removed 1-2 weeks after the procedure, depending on the strength of the chosen construct, and protected ROM exercises are begun. 

Complications

Complications include the following:

  • Neurovascular injury
  • Stiffness
  • Instability and recurrent dislocation
  • Posttraumatic arthritis of the elbow

Long-Term Monitoring

The elbow is immobilized for about 1 week, and a protected mobilization program in a hinged orthosis is then initiated, which prevents varus-valgus stresses on the elbow. Brace use is continued for approximately 4-6 weeks to allow the ligaments to heal.

Prophylaxis against heterotopic ossification may also be initiated on postoperative day 1. The authors prefer to use indomethacin (75 mg PO) for 3 weeks after the procedure.

Patients should be followed to ensure that they achieve a functional arc of motion.