Coronoid Process and Monteggia Fractures

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CHAPTER 27 Coronoid Process and Monteggia Fractures

THE CORONOID

As this fracture often occurs in conjunction with radial head fractures and dislocation; it is also discussed in the chapter on complex instability (see Chapter 29).

MECHANISM OF INJURY

Isolated coronoid fractures are uncommon and usually occur in association with elbow dislocation.49,59 One recent review of 120 complex elbow injuries identified 21% with coronoid and radial head fractures, 19% with olecranon and radial head fracture and 33% with radial head, olecranon and coronoid fracture.20 One group identified three of eight isolated coronoid fractures.23 Theoretically, the coronoid is fractured with the elbow in 0 to 20 degrees of flexion during an axial load (Fig. 27-1).1 This is a mechanism similar to that in elbow dislocation. With flexion past 30 degrees, radial head fractures occur. The combination of coronoid and radial head fracture has important implications for treatment, as discussed in Chapter 29. Of particular note is the fact that fractures involving more than 50% of the coronoid (Regan/Morrey type II) are associated with marked elbow instability, especially if the radial head has been resected (Fig. 27-2).12,13,36

INCIDENCE

Fractures of the coronoid process are uncommon. This may occur with a comminuted olecranon or proximal ulnar fracture (Fig. 27-3). The injury has also been reported in 2% to 10% of patients with dislocation of the elbow. Our review of 293 acute radial head fractures documented 33 (11%) concurrent coronoid fractures (see Chapter 24).64 Since the initial series of 35 patients,49 a few case reports19,61 and small series have appeared.23,31,56

CLASSIFICATION

Review of Mayo records resulted in a simple classification of coronoid fractures as well as a rationale for treatment (Fig. 27-4). Type I is a fracture of the tip of the coronoid process caused by a shearing force as the coronoid process subluxates or dislocates over the trochlea. A type II injury involves a single or comminuted fragment constituting about half of the coronoid. A type III fracture involves more than half of the coronoid process. The type II or III fracture may be comminuted, and all three may be associated with dislocation of the elbow or with other injuries. Comminution in the sagittal plane, often involving the medial portion of the coronoid and sometimes even involving the sublime tubercle, has been documented58 (Fig. 27-5). Subtle medial coronoid fractures have also been documented. A hint of such an injury is the appearance of the so-called double crescent sign (Fig. 27-6).

TREATMENT

Authors’ Preference

Technique

If the radial head is fractured or the elbow is grossly unstable, exposure and fixation of the coronoid is facilitated. We still usually use a straight posterior skin incision. Kocher’s interval is used if the radial head is fractured. If the fracture is an isolated one, a medial approach is used (see Chapter 7). This is mandatory if a sagittal component is present and if the medial collateral ligament is involved.

With the use of the posterior incision, the ulnar nerve is exposed but not transferred. The flexor-pronator origin is released with a 1-cm cuff of tendon left on the medial epicondyle (Fig. 27-9). The brachialis muscle is elevated from the capsule, and the joint entered. Fixation is ideally accomplished with one or two compression screws (Fig. 27-10). With comminuted fractures, a heavy No. 5 nonabsorbable suture may be placed through the brachialis tendon, and then through the fracture, and is secured through drill holes in the ulna through the base of the fracture (Fig. 27-11). A buttress plate is also effective (Fig. 27-12).

Reconstruction

An absent coronoid may be reconstructed with a well-fashioned bone graft from the ilium. Moritomo and colleagues35 have also described reconstruction with the osteotomized portion of the olecranon. But in general, reconstruction is unreliable. Using an osteochondral graft is successful in only about 50% of cases. More complex reconstruction has also been assessed42 with better outcomes being realized if the coracoid, radial head, and collateral ligaments are all addressed at the time of the injury.42,53,54

RESULTS

The results of 35 patients with acute coronoid fractures treated at Mayo are shown in Table 27-1. Using an elbow performance index, it is obvious that the chance of a satisfactory result directly correlates with the severity of the injury, as reflected by the coronoid fracture type. Pain is uncommon in type I and typical in type III injury. Our impression is that the results have improved over the last decade owing to (1) a better understanding of the implications of associated injury, (2) more aggressive exposure, and (3) improved design of internal and external fixation systems. Hence, the reports by both Ring et al55 and Pugh et al46 on 80% satisfactory outcomes following the above-mentioned principles when employed for acute fracture management.

MONTEGGIA FRACTURE

Giovanni Battista Monteggia of Milan first described the injury that bears his name in 1814,33 the same year that Colles described his fracture. Monteggia initially reported on a fracture of the ulna associated with anterior dislocation of the radial head, which is today recognized as the most common of the Monteggia lesions, a term coined by Bado4 that includes all ulnar fractures associated with dislocations of the radiocapitellar articulation. These lesions are uncommon (7% of ulnar fractures, 0.7% of elbow injuries5) but are difficult to manage properly.