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

FIGURE 27-1 Coronoid fracture occurs with an axial load and between 0 and 20 degrees of flexion.

FIGURE 27-2 Experimental data depicting the stability of the ulnohumeral joint. With fractures involving 25%, 50%, and 75% of the coronoid, the joint is grossly unstable. The type II, 50% fracture is unstable at 60 degrees of extension (A) with the radial head removed, the elbow is unstable, even with more than 90 degrees of flexion (B).

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 reports^19,⁶¹ and small series have appeared.^23,^31,⁵⁶

FIGURE 27-3 The Mayo IIIB transolecranon fracture dislocation typically does involve the coronoid.

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).

FIGURE 27-4 Regan-Morrey classification of coronoid fractures. Type I is a small shear fragment (A); type II is a single or comminuted portion involving approximately 50% (B); type III is a fracture involving more than half of the articulation (C).

FIGURE 27-5 Comminuted coronoid fractures may include a sagittal element (A) that will frequently contain the attachment of the medial collateral ligament (MCL) (B).

FIGURE 27-6 Sometimes, the medial coronoid fracture may be very subtle (A). The lateral shows the double crescent sign (arrows) representing the normal and fracture contour (B). The three-dimensional CT reconstruction shows the lesion (C).

ASSOCIATION INJURIES

With type I fractures, or any coronoid fracture, one must assume that the elbow has dislocated. Even if dislocation did not occur, some injury to the ligament is present, even if only a strain. Furthermore, 35% of the patients with type I, 56% of the patients with type II, and 80% of the patients with type III coronoid fractures had other identified injuries.⁴⁹ In fact, today an isolated injury is considered a rarity and other pathology must be sought if it is not obvious.

Our current management philosophy is governed by our clinical experience and by basic investigational data (see Chapter 3).^26,^31,^37,⁴⁶ Simply put, first and foremost, a stable ulnohumeral joint must be attained and maintained. This means

1. All coronoid fractures of greater than 50%, some type II fractures, and all type II fractures are fixed.

2. All associated radial head fractures are fixed if possible (fewer than four fragments) or otherwise replaced.

3. The lateral ulnar collateral ligament is always repaired.

4. An articulated external fixator is applied if any question about fragment fixation or ulnohumeral stability exists.

TREATMENT

Authors’ Preference

(From Regan, W., and Morrey, B. F.: Fractures of the coronoid process of the ulna. J. Bone Joint Surg. 71A:1348, 1989.)

Note: The most important point is that the acute injury must be properly managed. Outcomes of acute management are orders of magnitude better than those of delayed reconstruction.^23,^42,^52,^56,⁶⁷

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).

FIGURE 27-9 The flexor-pronator muscle group is reflected with a cuff of tissue for reattachment (A). Elevating the brachialis tendon off the capsule and a medial arthrotomy allows adequate exposure of the coronoid (B).

FIGURE 27-10 Type III fracture (A) exposed through a medial approach, fixed with two compression screws, and protected with an external fixator (B) (DJD, Howmedica) with excellent 6-month result (C and D).

FIGURE 27-11 A suture through the brachialis tendon may be used to secure badly comminuted fracture fragments.

FIGURE 27-12 A 35-year-old radiologist has a comminuted fracture of the coronoid (A and B). Buttress plate fixation and protected with the external fixator (C and D). At 8 weeks, excellent fixation and early healing. Extension (E); flexion (F).

Reconstruction

An absent coronoid may be reconstructed with a well-fashioned bone graft from the ilium. Moritomo and colleagues ³⁵ 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 al ⁵⁵ and Pugh et al⁴⁶ on 80% satisfactory outcomes following the above-mentioned principles when employed for acute fracture management.

TABLE 27-1 Results of Treatment According to Coronoid Fracture Type

Stress Fracture

Although reported for the olecranon,^30,⁶⁸ stress fracture has not been reported for the coronoid. We have, however, documented one instance occurring in a young 17-year-old female gymnast (Fig. 27-13). Symptoms resolved and full activity returned with cessation of activity for 3 months.

FIGURE 27-13 Plain film of 17-year-old female gymnast with chronic cubital pain, suggesting sclerosis of the coronoid tip (A). Three-dimensional reconstruction confirms stress fixation (B).

(Courtesy of Dr. A. Rettig.)

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.

CLASSIFICATION

Depending on the type of dislocation of the radial head (anterior, posterior, and lateral), three distinct types of injuries were recognized early. Bado ⁴ subsequently proposed a classification that encompasses the full spectrum of these injuries and has become universally accepted.

Type I

Type I injury is an anterior dislocation of the radial head associated with a fracture of the ulnar diaphysis at any level with anterior angulation (Fig. 27-14). This is the most common type of lesion (55% to 78% of Monteggia fractures, depending on the series) and is most common in children.

FIGURE 27-14 Monteggia lesion type I.

(Redrawn from Reckling, F. W., and Cordell, L. B.: Unstable fracture-dislocations of the forearm: The Monteggia and Galeazzi lesions. Arch. Surg. 96:999, 1968.)

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