JBJS | Current Concepts Review - Fracture-Dislocation of the Elbow*

The Journal of Bone & Joint Surgery, Volume 80, Issue 4

Current Concepts Review | April 01, 1998

Current Concepts Review - Fracture-Dislocation of the Elbow*

DAVID RING, M.D.†; JESSE B. JUPITER, M.D.†, BOSTON, MASSACHUSETTS

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Investigation performed at the Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston

The Journal of Bone & Joint Surgery. 1998; 80:566-80

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Introduction

The elbow joint is one of the most inherently stable articulations of the skeleton^1,54,75,77. When a dislocation is not associated with a fracture, early mobilization after closed reduction is associated with a low risk of redislocation^72,99, despite the fact that, in most patients, all of the capsuloligamentous stabilizers of the articulation of the elbow are ruptured^19,45,48,49. When at least one of the osseous or articular component structures that contribute to stability of the elbow is disrupted, the risk of recurrent or chronic instability and arthrosis is increased^11,50. Treatment of these injuries remains challenging in part because accurate definitions of the patterns of injury, the specific roles of the component structures contributing to stability of the elbow, and a rational approach to treatment have not been fully determined. Despite the preponderance of literature on traumatic injuries about the elbow, there are relatively little data specifically addressing combined osseous, articular, and ligamentous injury of the elbow^{11,34,50,107,124}.

The purposes of this review are to define the component structures that together make the elbow such a unique articulation and to provide an understanding of the treatment of complex fracture-dislocations of the elbow.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Department of Orthopaedic Surgery, Massachusetts General Hospital, ACC 527, 15 Parkman Street, Boston, Massachusetts 02114.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Department of Orthopaedic Surgery, Massachusetts General Hospital, ACC 527, 15 Parkman Street, Boston, Massachusetts 02114.

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Fig. 1 Illustration demonstrating how the stabilizing structures of the elbow can be thought of as components of a ring. If one part of the ring (such as the radial head) is injured, disruption of another part of the ring (such as the medial collateral ligament) should be sought. The complexity of the injury increases with the number of components (or columns) involved. Stability is restored through restoration of each component of the ring.

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Fig. 2 Prereduction radiograph of a fracture-dislocation of the elbow. Such fractures can be difficult to characterize on the basis of radiographs. Careful evaluation reveals that the normal contour of the radial head is absent and that there are a number of fracture fragments about the elbow. One fragment (arrow) is seen between the trochlear notch and the coronoid process. It is impossible to judge the status of the coronoid process from this projection, but it may also be fractured. Whereas the treatment of a simple dislocation of the elbow is straightforward, the treatment of a fracture-dislocation such as this one can be very challenging. Closed reduction may be impossible because of entrapped intra-articular fracture fragments, and acute and chronic recurrent instability are much more likely. Restoration of stability depends on prompt, appropriate operative treatment. Consideration must be given to repair or replacement of the radial head, repair of a fracture of the coronoid process if one is present, and repair of ruptured ligaments.

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Fig. 3 Radiograph illustrating the most complex pattern of instability of the elbow, in which all components of the ring are involved. Not only is the ulna dislocated posteriorly with respect to the humerus, which usually results in rupture of all of the capsuloligamentous restraints, but also the osseous and articular restraints provided by the trochlear notch are disrupted at both the coronoid and the olecranon process. Furthermore, the radial head is fractured. All of the fractures are multifragmentary, which greatly increases the difficulty of operative fixation. However, injuries such as this one, with involvement of all of the osseous, articular, and capsuloligamentous components that contribute to stability of the elbow, are rare. Often, when there is failure through osseous elements, at least some of the capsuloligamentous restraints are spared.

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Figs. 4-A through 4-D: Treatment of a fracture of the proximal aspect of the ulna that is associated with an anterior or transolecranon fracture-dislocation is sometimes simple but more often is very complex. The term transolecranon fracture-dislocation reflects the fact that the distal aspect of the humerus is driven through the proximal aspect of the ulna and emphasizes the potential for complex skeletal disruption, including comminution of the depths of the trochlear notch, extension into the ulnar diaphysis, fracture of the coronoid process, and segmentation of the olecranon. The entire forearm is dislocated anteriorly with the radioulnar relationship intact, thus distinguishing this injury from a Monteggia lesion. Fig. 4-A: Radiograph of a simple fracture of the elbow. Such fractures are usually oblique, starting between the articular surfaces of the coronoid and olecranon processes (in the transverse groove of the trochlear notch) and exiting distally on the posterior surface of the ulna.

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Fig. 4-B Radiograph of a complex fracture in which the coronoid process has separated as a single large fragment. There is extensive comminution in the depths of the trochlear notch and extending distally into the shaft, and the olecranon is fragmented as well. The radioulnar relationship is relatively intact, and the entire forearm has dislocated anteriorly.

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Fig. 4-C Radiograph of a complex fracture in which the coronoid process remains attached to the ulnar shaft but the depths of the trochlear notch and the olecranon are comminuted.

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Fig. 4-D Radiograph of the elbow seen in Fig. 4-C, made after reconstruction of the proximal part of the ulna. Such a reconstruction requires stable, anatomical fixation of the ulna with a contoured plate to restore the contour and dimensions of the trochlear notch. Reliable fixation of the olecranon fragment is ensured by contouring of the plate toward the tip of the olecranon. As a result, three screws can be placed in the fragment. The most proximal screws are oriented at a 90-degree angle with respect to the more distal screws. This enhances stability further by creating an interlocking construct. There is a small amount of heterotopic ossification (arrow) anterior to the humerus.

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Figs. 5-A and 5-B: Radiographs of a posterior Monteggia lesion. Such fractures can occur at various locations in the ulna, ranging from the middle of the diaphysis to the olecranon process. Fig. 5-A: The ulna most commonly fractures through the metaphysis, just distal to the coronoid process. Usually, the anterior cortex fails with a separate triangular or quadrangular butterfly fragment (arrow).

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Fig. 5-B Often, the ulnar fractures more proximally, at the level of the coronoid process. In such cases, the anterior cortex fails with the coronoid process as a single large fragment. This injury therefore represents a transitional lesion that affects the function of both the radioulnar and the ulnohumeral articulation. Successful treatment requires anatomical alignment of the ulna to ensure appropriate radioulnar articulation as well as stable anatomical reduction of the coronoid process to restore the contour and dimensions of the trochlear notch and to ensure ulnohumeral stability.

Components That Contribute to Stability of the Elbow

The structure of the elbow reflects a balance between the functional requirements for spatial positioning of the hand and the need for sufficient stability to allow for the manipulation of heavy objects, throwing, and bearing weight^1,54,61. Flexion and extension of the elbow at the ulnohumeral articulation alters the length of the strut holding the hand away from the trunk⁵⁴. Furthermore, humans are capable of using the upper extremity for sophisticated tasks (such as using tools) largely as a result of the rotational motion that occurs at the proximal and distal radioulnar joints^54,61. During the evolution of bipedal mammals, a number of adaptations developed in order to preserve the stability of the elbow as the mobility of the articulation increased⁶¹. These adaptations include an anterior tilt of the ulnotrochlear articulation, a deep trochlear notch with a prominent coronoid process, interdigitation of a ridge in the trochlear notch with a groove in the trochlea, and maintenance of the force-transferring role of the radius^1,54,61.

Osseous and Articular Components

The trochlear notch surrounds almost 180 degrees of the trochlea^108,123, making the elbow one of the most confined articulations in humans and accounting in large part for its inherent stability¹. The distal articular surface of the humerus is tilted 30 degrees anteriorly. This is matched by a comparable posterior tilt of the trochlear notch^{54,75,108,123}. The forward tilt of the articulation is beneficial in two ways. First, it increases the prominence of the coronoid process so that it helps to resist posterior subluxation of the elbow in both flexion and extension. Second, it increases the range of flexion of the elbow by ensuring clearance of the coronoid as it approaches the humeral shaft and by providing space for the flexor muscles of the arm and forearm^54,61. Interlocking of the coronoid and olecranon processes into their corresponding fossae on the distal aspect of the humerus provides for additional motion and stability at the extremes of ulnohumeral motion⁷⁷.

The shape and contour of the ulnohumeral articular surface further enhance stability. The trochlea has been described as spool-shaped—that is, it is wide in the coronal plane and has a deep groove in its midportion^108,113. The interdigitation of this central groove with a corresponding ridge in the trochlear notch adds stability to the articulation^{54,61,75,108,113}.

The ulnohumeral articulation contributes not only to anterior-posterior stability but also to varus, valgus, and rotatory stability. An experiment in cadavera in which incrementally greater portions of the proximal aspect of the ulna were resected demonstrated a roughly linear decrease in combined varus, valgus, and rotational stability of the elbow². The resistance to valgus load was diminished by 50 per cent with resection of only a quarter of the olecranon process, but resistance to varus load did not diminish substantially until the resection approached the coronoid process. Another study in cadavera demonstrated that the ulnohumeral articulation is the most important stabilizer of the elbow under varus stress, providing 55 per cent of the resistance to varus stress when the elbow is in full extension and 75 per cent of the resistance when it is in 90 degrees of flexion⁷⁷. The remainder of the resistance is contributed by capsuloligamentous structures.

When a fracture of the olecranon or the coronoid process occurs with a fracture-dislocation of the elbow, the restoration of stability depends largely on the reestablishment of the anatomical dimensions of the trochlear notch. A fracture of the coronoid process near its base compromises stability of the elbow in two ways: it disrupts the inherent stability of the trochlear notch and it renders the anterior band of the medial collateral ligament, which attaches near the base of the coronoid process, incompetent^12,75. Large coronoid fracture fragments may also include the insertion of the brachialis, which provides a measure of both static and dynamic stability to the elbow^12,40. The brachialis inserts distally at the junction of the coronoid process with the ulnar shaft and is therefore not attached to smaller coronoid fragments¹².

The radial head contributes to stability and force transmission across the elbow joint despite the fact that, over the course of evolution, it has become smaller and more circular in order to facilitate rotational motion of the forearm⁶¹. Studies of cadavera have demonstrated that the radial head contributes to force transmission from the hand to the humerus over a wide range of positions of the elbow^33,80. Maximum joint contact and force transmission occur when the forearm is pronated and the elbow is extended⁷⁰. As much as 60 per cent of a load applied to the hand may be transmitted to the humerus through the radiocapitellar articulation, even when the interosseous ligament of the forearm has been transected³³.

In several studies of cadavera in which the radius was fixed in relation to the ulna and was subjected to a valgus load, resection of the radial head resulted in an approximately 30 per cent decrease in the resistance to valgus load by the elbow^{13,31,42,77,98}. The resistance was only partially restored by prosthetic replacement of the radial head^13,42,98. In particular, restoration of the resistance to valgus stress was very limited when a silicone prosthesis was implanted^13,42,98, whereas a prosthesis made of a stiffer material, such as polymethylmethacrylate, wood, or ultra-high molecular weight polyethylene, restored as much as half of the resistance lost following resection of the radial head^13,31,98.

The articulation between the radius and the distal aspect of the humerus (the lateral osseous column of the elbow) is essential in maintaining stability of the elbow when the collateral ligaments are damaged. In studies of cadavera, resection of the radial head had a limited effect on the kinematics of the elbow when the anterior bundle of the medial collateral ligament remained intact⁸³. In contrast, a combination of resection of the radial head and disruption of the anterior bundle resulted in substantial instability leading to dislocation. This instability was partially offset by simulated active muscle contraction.

Capsuloligamentous Components

The posterior and transverse bundles of the medial collateral ligament complex are subtle thickenings in the capsule, but the anterior bundle is readily identified in anatomical dissections^22,32,75. Serial sectioning studies of cadaveric elbows have suggested that the anterior bundle provides one-third to one-half of the elbow's resistance to valgus stress, depending on the amount of flexion of the elbow^42,77,98,112. Of interest is the fact that soft-tissue and capsular structures other than the medial collateral ligament complex are responsible for as much as 40 per cent of the resistance to valgus stress and one-third of the resistance to varus stress when the elbow is in full extension⁷⁷. This resistance has been ascribed to the anterior aspect of the capsule. Attenuation of the medial collateral ligament has been associated with difficulty in performing activities that subject the elbow to large valgus loads, such as sports that involve throwing, but it does not cause recurrent dislocation in the absence of an associated osseous or articular injury^16,44.

If the coronoid process is fractured near its base, the integrity of the anterior bundle of the medial collateral ligament may be at least partially spared as the loss of skeletal continuity between the coronoid process and the proximal aspect of the ulna diffuses the force of the injury from the ligament itself¹⁰⁵. In other words, a large fracture of the coronoid process, a fracture of the medial epicondyle, and a rupture of the anterior bundle of the medial collateral ligament may represent alternative patterns of disruption of the medial components that contribute to stability of the elbow.

The lateral collateral ligament complex originates from the lateral epicondyle at a site collinear with the axis of ulnohumeral rotation⁷⁸. This ligament inserts onto the annular ligament, which binds the radial head to the lesser sigmoid notch, and directly onto the ulna^15,89. Some authors have emphasized an ulnar insertion of the lateral collateral ligament complex termed the lateral ulnar collateral ligament^75,84,89. A large proportion of cases of recurrent dislocation of the elbow in the absence of an associated fracture have been ascribed to posterolateral rotatory instability as a result of post-traumatic attenuation of this ligament^84,89,90. The primacy of this particular ligament was brought into question by a recent investigation in which human cadaveric elbows were serially sectioned in order to define the relative importance of the lateral soft-tissue structures¹⁵. The results of that study emphasized the shared responsibility for resistance to posterolateral rotatory instability among the ulnar and annular insertions of the lateral collateral ligament complex; the annular ligament itself; and musculotendinous structures, including the supinator tendon, a fascial band of the extensor carpi ulnaris, and the conjoined extensor origin reinforced by its intermuscular septa¹⁵. Tension in the lateral collateral ligament complex and overlying musculotendinous structures maintains apposition of the radial head and the capitellum and is therefore critical to the stability of the elbow^41,91,111. When there is a fracture-dislocation of the elbow, both repair or replacement of the radial head and ligamentous repair or reconstruction may prove essential.

Musculotendinous Components

The muscles crossing the elbow joint also contribute to its stability⁸³. The action of these muscles helps to maintain the trochlea in its corresponding notch in the ulna. An experiment on cadaveric elbows in which the anterior bundle of the medial collateral ligament had been sectioned demonstrated that simulated physiological muscle action partially restores normal kinematics to the elbow⁸³.

Patterns of Injury

We have adopted the thesis of Heim, who suggested that the patterns of fracture-dislocation of the elbow can be categorized according to the extent of the disruption of the capsular ligaments and the extent of the injury to the osseous and articular components on which the elbow is dependent for its stability³⁶. It is instructive to consider these anatomical restraints as a structural ring with anterior, posterior, medial, and lateral columns, or components, that contribute to stability (Fig. 1). The potential for recurrent or chronic instability becomes greater as more components of the ring are injured. Furthermore, when there is radiographic evidence of disruption of one component, such as a comminuted fracture of the radial head, a second disruption of the ring, such as an injury of the medial collateral ligament, is likely.

Injuries of Ligamentous Structures Only

A spectrum of soft-tissue injury, extending from lateral disruption alone to rupture of all of the capsuloligamentous restraints of the elbow, can occur with simple dislocation as well as with dislocation associated with a fracture⁹⁰. Studies of operative repair of simple posterior dislocations of the elbow have demonstrated complete disruption of all of the capsuloligamentous structures in nearly every patient^19,45,48,49. In addition, the surrounding muscles were injured to a variable degree^19,48,49.

Even though complete capsuloligamentous disruption is associated with most simple posterior or posterolateral dislocations, closed reduction can usually restore sufficient stability of the elbow to allow early active mobilization⁷². Instability and arthrosis were uncommon findings in long-term follow-up studies of simple dislocation of the elbow⁴⁷. Josefsson et al. evaluated fifty-two patients an average of twenty-four years after a posterior dislocation of the elbow without an associated fracture⁴⁷. None of the patients had symptoms related to residual instability, although eight (15 per cent) had signs of valgus instability on examination. Nineteen (38 per cent) of fifty patients for whom radiographs were available had radiographic evidence of mild degenerative joint disease (sclerosis, osteophytes, irregularities, or cysts in the subchondral bone), but no patient had narrowing of the joint space. These observations suggest that the intrinsic stability afforded to the elbow by the osseous and articular components of the articulation is sufficient to ensure healing and restoration of function of the capsuloligamentous stabilizers of the elbow.

Persistent instability following closed reduction of a simple dislocation may be related to soft-tissue interposition or entrapment of a chondral or osteochondral fragment in the joint⁴⁰. If these causes can be ruled out, stability should be reevaluated with the forearm in pronation, which tends to increase the tension on the lateral soft-tissue constraints^15,62. If stability is restored in pronation, active mobilization can be initiated with the extremity in a hinged cast-brace that holds the forearm in pronation. Prolonged immobilization after a dislocation is detrimental^72,99. Mehlhoff et al. evaluated fifty-two patients an average of thirty-four months after a simple posterior dislocation of the elbow and found that pain, stiffness, and instability (pain with valgus load) were more common in the elbows that had been immobilized for more than two weeks⁷².

Injuries of the Ligaments and the Radial Head

Treatment of a dislocation of the elbow with an associated fracture of the radial head is much more challenging than treatment of a simple dislocation^11,46,50 (Fig. 2). Not only was there probably more energy involved in the traumatic event but also failure to restore the contact compression of the radial head against the capitellum may severely compromise the ability of the lateral and medial collateral ligament complexes to heal with proper physiological tension. Treatment of a fracture-dislocation of the elbow with excision of the radial head without prosthetic replacement can lead to problems. Josefsson et al. reviewed the results of treatment of twenty-three patients who had a combined fracture of the radial head and dislocation of the ulnohumeral joint⁵⁰. By an average of fourteen years postoperatively, severe arthrosis had developed in twelve of nineteen patients who had excision of the radial head without replacement. Broberg and Morrey noted arthrosis in twenty-two (92 per cent) of twenty-four patients an average of ten years after fracture-dislocation of the elbow treated without repair or replacement of the radial head¹¹. Although only seven patients had moderate or severe arthrosis, more severe radiographic changes were associated with a longer duration of follow-up. Four patients in the series of Josefsson et al. and two patients in the series of Broberg and Morrey had a redislocation within the first two months after the injury, even though many patients in both series had been managed with immobilization in a cast or splint. The redislocation was associated with concomitant fracture of the coronoid process in all of the patients in the series of Josefsson et al. Persistent instability, loss of motion, heterotopic ossification, and post-traumatic arthrosis (all of which are uncommon after simple dislocation) have been well documented following fractures of the radial head associated with dislocation^{11,46,50,122,124}.

Hotchkiss^40,41 modified Mason's⁶⁹ classification system for fractures of the radial head to reflect the options available for treatment. Type I includes small marginal fractures that do not appreciably compromise stability and fractures that are minimally displaced (less than two millimeters) and do not restrict rotation of the forearm. Type II includes larger two-part fractures that are displaced two millimeters or more, any fracture that restricts rotation of the forearm, and relatively simple comminuted fractures that are amenable to operative fixation. Type-III fractures are so comminuted that operative fixation is not possible. This scheme is particularly useful in directing the treatment of fracture-dislocations of the elbow. Type-I fractures rarely necessitate operative intervention, whereas type-II fractures should be repaired and type-III fractures necessitate resection and replacement with a prosthesis in order to restore the stabilizing influence of an intact lateral column^40,41.

There are a number of operative techniques for exposure of the radial head. A midline posterior skin incision is advisable when it is necessary to repair the medial collateral ligament, coronoid process, or olecranon^18,94. This incision provides access to most of the elbow joint while limiting the risk of injury to cutaneous nerves¹⁸. Broad medial and lateral skin flaps are elevated at the level of the deep fascia, and each component of the injury is addressed through a separate muscular interval⁹⁴.

Recently, emphasis has been placed on the need to minimize the risk of operative disruption of the lateral collateral ligament complex^15,84,89. If the exposure described by Kocher⁶⁰ as the interval between the extensor carpi ulnaris and the anconeus is employed, it is important to ensure that the capsular incision remains anterior to the anterior margin of the anconeus and parallel to the fascial limit of the extensor carpi ulnaris¹⁵. Hotchkiss described an alternative exposure in which the elbow joint is first entered by elevating the capsule from the anterior aspect of the lateral part of the humerus in an area anterior to the origin of the lateral collateral ligament complex⁴¹. This allows visualization of the articular surface of the radial head. More distal exposure is accomplished by incision of the capsule longitudinally along a line that bisects the anteroposterior diameter of the radial head. The lateral collateral ligament complex and the annular ligament can be elevated anterior, but not posterior, to this line. More distal exposure of the neck of the radius requires entrance into the common extensor muscle compartment, mobilization of the muscle fibers anteriorly, and incision of the fascial floor of the compartment. This exposes the supinator muscle, which is incised at its posterior margin and swept anteriorly with the forearm in full pronation to protect the posterior interosseous nerve. Another option for exposure of the radial head is osteotomy of the origin of the lateral collateral ligament from the lateral condyle with later repair with use of a 3.5-millimeter screw^29,35,38.

When the surgeon exposes the radial head after fracture-dislocation of the elbow, he or she must take into account the fact that the origin of the lateral collateral ligament complex is often avulsed from the lateral condyle and the fractured radial head may not be useful as an anatomical landmark. Repair of the avulsed origin with sutures anchored to bone (with either drill-holes or suture anchors) should be considered at the time of closure. Repair performed with the forearm in pronation restores optimum tension¹⁵.

Operative repair of fractures of the radial head has been facilitated by the development of better implants for the fixation of small fractures³⁸. Mini-fragment screws can provide stable fixation of articular fragments when interfragmentary compression is applied^29,35,38,101. Provided that the screw is inserted at the non-articular peripheral surface of the radial head, the implant will not block rotation of the forearm. Smith and Hotchkiss, on the basis of experiments on cadavera, described a so-called safe zone for the application of screws and plates to the radial head and neck so as not to interfere with rotation of the forearm¹¹⁰. The zone is defined intraoperatively with use of three reference marks chosen as the bisecting point of the anteroposterior diameters of the radial head with the forearm in full supination, neutral rotation, and full pronation. The anterior limit for fixation is a point two-thirds of the distance from the mark made in neutral rotation to the mark made in full supination. The posterior limit is a point halfway between the marks made in neutral rotation and full pronation. If there is articular impaction or comminution of the radial neck, mini-fragment plates should be used to support the realigned articular fragments^29,38. The defects created by repositioning of the fracture fragments should be filled with autogenous cancellous bone graft to provide additional support and to enhance healing.

When an implant must be inserted across an articular surface for fixation of articular fragments, fixation can be accomplished with self-compressing screws (such as Herbert screws) that can be sunk beneath the chondral surface or with small threaded Kirschner wires^88,106,109. The development of bioabsorbable pins may also prove useful for this purpose⁹⁶.

The goal of operative fixation is anatomical reduction and secure fixation of the radial head. Healing may be delayed and osteonecrosis can occur as a result of the often tenuous blood supply to this entirely intra-articular epiphysis³⁷. Heim encountered problems with healing or avascular necrosis in association with five of eleven comminuted fractures in which all of the soft-tissue attachments had been stripped by the injury³⁷. Fixation must therefore be sufficiently secure to maintain the lateral columnar support of the elbow until the ligaments heal, at which time a delayed resection of an ununited radial head can be performed more safely¹⁰.

Retrospective case studies of operative fixation of fractures of the radial head^{6,20,29,35,55} have indicated that operative techniques can be demanding and that comminuted fractures may be difficult to fix anatomically and securely. However, they have also demonstrated that good or excellent results can be achieved in a high percentage of patients. For comminuted fractures, we recommend that the surgeon be prepared to resect the radial head and to replace it with a prosthesis.

Geel et al. reported the results for nineteen patients who had internal fixation of a fracture of the radial head²⁹. Exposure was obtained through osteotomy of the lateral epicondyle, and mini-fragment (1.5 and 2.0-millimeter) cortical-bone screws were used for fixation. Autogenous cancellous bone graft from the lateral condyle was inserted in residual osseous defects. A mini-fragment plate was used for fixation if a fracture through the radial neck separated the radial head from the remainder of the shaft. Only three of the fractures were comminuted; the remainder were simple neck, wedge, or central impaction fractures. After a relatively short duration of follow-up (twelve months), fourteen patients had full, painless motion of the elbow and forearm. Five patients had minor restriction of motion and mild-to-moderate pain with heavy activity.

King et al. followed thirteen patients for an average of thirty-two months after operative fixation of fourteen fractures of the radial head⁵⁵. Eight of the radial fractures were associated with fracture or dislocation of the ulnohumeral joint and six were comminuted. Fixation was achieved through a Kocher exposure with 2.7 and 4.0-millimeter screws. A good or excellent result was achieved after treatment of all of the simple (Mason⁶⁹ type-II) fractures but only two of the comminuted (Mason type-III) fractures. Incomplete reduction and early loss of reduction were common after the comminuted fractures (seen in two patients)⁵⁵.

Esser et al. evaluated twenty-six patients an average of more than seven years after internal fixation of a fracture of the radial head with Herbert and mini-fragment screws through a Kocher exposure²⁰. All twenty of the patients who did not have associated ulnohumeral dislocation had a good or excellent result. The only two fair results occurred in patients who had a fracture-dislocation.

Replacement of the radial head is a viable option for treatment of traumatic instability of the elbow or forearm associated with a Hotchkiss type-III fracture (a fracture that is so comminuted it precludes operative repair). The first prosthetic radial heads were implanted more than half a century ago and were initially intended to prevent proximal migration of the radius, cubitus valgus, and heterotopic ossification after resection of the radial head¹¹⁴. While the need for replacement of the radial head after delayed resection has been challenged^10,82, a number of studies have demonstrated advantages to prosthetic replacement in the treatment of fracture-dislocations of the elbow^{34,59,64,81,116}. For a time, the most widely available prosthesis was made of silicone rubber^64,81,116. Although a number of investigations of cadavera have suggested that a silicone prosthesis is not rigid enough to restore support to the lateral column^13,31,42,98, clinical experience has suggested that replacement with such an implant yields better results than simple resection for the treatment of fracture-dislocation of the elbow^64,81. Silicone prostheses, as well as previous designs made of acrylic, are prone to breakage and may induce particulate synovitis¹²¹.

The use of prostheses made of various types of metal has been evaluated, and their effectiveness in the treatment of fracture-dislocations of the elbow is well documented^34,59. Harrington and Tountas reported the results for seventeen patients who were treated with excision because of complex traumatic instability of the elbow involving fracture of the radial head³⁴. Eight patients had a posterior dislocation of the elbow, with an associated fracture of the coronoid process in four; five had a complete rupture of the medial collateral ligament; and four had a fracture of the proximal aspect of the ulna, with an associated fracture of the coronoid process in one. Fifteen patients had the radial head replaced with a metallic prosthesis and two, with a prosthesis made of silicone rubber. According to a strict rating scale that weighted residual pain heavily, a good or excellent result was achieved in all but three patients an average of 6.9 years postoperatively. Knight et al. reviewed the results of resection of the radial head and replacement with a Vitallium prosthesis for the treatment of a comminuted fracture of the radial head in thirty-one patients, twenty-one of whom had an associated dislocation or ulnar fracture⁵⁹. An average of 4.9 years postoperatively, there was no residual instability and only limited loss of motion. Six patients (19 per cent) had aching pain with activity, and one (3 per cent) had pain at rest.

Replacement of the radial head with an osteoarticular allograft was suggested recently, but the technique remains experimental^76,117. It might prove most useful when comminution extends into the radial neck and this portion must also be resected. Currently available prostheses may not provide adequate length in this situation.

Radial head prostheses made of silicone frequently need to be removed because of fragmentation and synovitis¹²¹. It is unclear how often metal prostheses cause symptoms and need to be removed, but removal may be extremely difficult. If removal is needed, it may be necessary to take down the lateral collateral ligament complex from the humerus and to dislocate the elbow. Fortunately, removal of either type of prosthesis is not necessary on a routine basis. In the setting of a fracture-dislocation of the elbow or forearm, the prosthesis should not be removed until healing of the ligaments is ensured. We recommend a minimum of six months after associated ligamentous injury about the elbow before removal of the prosthesis, but the timing after fracture-dislocation of the forearm remains uncertain.

After repair or replacement of the radial head, the stability of the elbow is assessed by moving the joint through a full range of motion. If the elbow redislocates at more than 30 degrees of flexion, stability should be reevaluated after the lateral collateral ligament complex is repaired. When there is persistent instability, exposure and repair of the medial collateral ligament complex should be considered. In the unusual event that excessive instability persists after repair or replacement of the radial head and repair of both ligaments, a hinged distractor can be applied to allow active mobilization while ensuring that the ligaments heal with physiological tension⁶⁵.

Injuries of the Ligaments, Radial Head, and Coronoid Process

When a fracture-dislocation involves the coronoid process, the threat of recurrent and chronic instability of the elbow increases. In most cases, the radial head is also fractured. This combination of injuries (dislocation of the elbow, fracture of the radial head, and fracture of the coronoid process) was referred to as the so-called terrible triad of the elbow by Hotchkiss⁴⁰ and is prone to acute redislocation⁵⁰ as well as to chronic instability and post-traumatic arthrosis^14,102.

There has been very little discussion of these injuries in the literature, particularly with regard to patterns of injury, decisions regarding treatment, operative tactics, and outcome. On the basis of our review of the literature and our own experience, it appears that the size of the coronoid fracture fragment in this injury can range from a small marginal fragment (Regan and Morrey¹⁰² type I) to a more substantial fragment (Regan and Morrey type II), but it is rarely large enough to include the insertion of the anterior bundle of the medial collateral ligament (Regan and Morrey type III)^{8,11,14,17,50,67,71,102}. As a result, in most patients, this pattern of injury includes complete capsuloligamentous disruption combined with a loss of the osseous and articular support of the lateral and anterior columns. In such a situation, it may become necessary to repair even relatively small coronoid fracture fragments in order to restore sufficient osseous and articular stability to allow active mobilization of the elbow.

It is difficult to decide whether to use internal fixation for a fracture of the coronoid process on the basis of the size of the fragment alone. Morrey contended that the ulnohumeral joint remains functional with a loss of as much as 50 per cent of the height of the coronoid process⁷⁶. Reports in the German-language literature state that a fragment that represents more than one-sixth of the circumference of the trochlear notch should be fixed^17,71,115. We recommend that each patient be evaluated individually as we have encountered cases in which the elbow remained unstable until a small fracture of the coronoid process was realigned and secured.

Indirect reduction and fixation of the coronoid process with interfragmentary screws is useful for larger fractures but is rarely possible for smaller fractures. The coronoid process can be exposed from the medial side of the elbow through a posterior skin incision after a medial skin flap is raised and the ulnar nerve is mobilized and transposed anteriorly into the subcutaneous tissues. Medial exposure is obtained by mobilization of the flexor muscles of the forearm either by osteotomy of the medial epicondyle³⁸ or by elevation of the flexor carpi ulnaris from its ulnar origin, leaving the humeral origin of the flexor-pronator muscles and the medial collateral ligament intact⁹⁴. Alternatively, if there is a fracture of the radial head, it may be possible to gain limited exposure of the coronoid process from the lateral side before the radial head is repaired or replaced. An alternative is a direct anteromedial approach to the coronoid process through a separate skin incision¹²⁰, although this places the brachial artery and median nerve at risk for injury. Fixation of the coronoid process is achieved either with a small screw or with a wire or stout braided non-absorbable suture passed through drill-holes in the fragment or secured to the insertion of the anterior part of the capsule on the fragment. A hinged distractor is applied only in the uncommon circumstance that repair of the radial head, coronoid process, and ligamentous structures fails to restore sufficient stability to allow active mobilization of the elbow⁶⁵.

Injuries of the Ligaments, Radial Head, Coronoid Process, and Olecranon

A fracture of the olecranon adds to the complexity of traumatic instability of the elbow not only by disrupting the trochlear notch further but also by interfering with the static and dynamic contributions of the triceps to the stability of the elbow. Combined injury of the coronoid and olecranon processes and the radial head represents complete disruption of the osseous and articular components that contribute to the stability of the elbow (Fig. 3). Large fractures of the coronoid process (Regan and Morrey¹⁰² type III) are common among these patterns of injury and represent loss not only of the anterior osseous buttress but also of support from the medial column because the insertion of the anterior bundle of the medial collateral ligament is disrupted. Restoration of the contour, dimensions, and depth of the trochlear notch requires stable anatomical fixation of the fractures of both the olecranon and the coronoid process.

A large percentage of fracture-dislocations of the elbow that involve the olecranon tend to occur in characteristic and distinct patterns depending on an anterior or a posterior direction of dislocation^{5,7,53,93,103,105,107,118,124}. One exception is fracture-dislocation of the elbow resulting from a severe, high-energy direct impact (so-called sideswipe injuries); these injuries are often so complex that they do not fit a particular pattern³⁹. Anterior fracture-dislocations have been called transolecranon fracture-dislocations to describe the disruption of the olecranon process and trochlear notch that occurs as the forearm dislocates anteriorly with respect to the trochlea^7,105 (Figs. 4-A, 4-B, 4-C and 4-D). Posterior fracture-dislocations of the olecranon are thought in many cases to represent the most proximal extent of the spectrum of posterior Monteggia lesions^53,95,97 (Figs. 5-A and 5-B). Common to these two types of injury are complex disruption of the proximal aspect of the ulna, often involving large (Regan and Morrey¹⁰² type-III) fractures of the coronoid process and relative sparing of the collateral ligaments.

Anterior or Transolecranon Fracture-Dislocation of the Elbow

Anterior fracture-dislocation of the elbow occurs when a high-energy direct blow is applied to the dorsal aspect of the forearm with the elbow in mid-flexion^7,105. Whereas anterior dislocation of the elbow without an associated fracture is exceedingly rare, anterior fracture-dislocation of the elbow may be underrecognized^{105,107,118,124} and is often misidentified as an anterior Monteggia lesion¹⁰⁵. Discussion of this injury in the literature has been limited for the most part to relatively simple fracture-dislocations of the olecranon^3,7 (Fig. 4-A); however, the fracture of the proximal aspect of the ulna in this setting is often complex and may include large (Regan and Morrey¹⁰² type-III) coronoid fracture fragments, extension of the fracture into the ulnar diaphysis, extensive comminution of the depths of the trochlear notch, and fragmentation of the olecranon¹⁰⁵ (Figs. 4-B and 4-C). The confusion with anterior Monteggia lesions is a result of the apparent anterior dislocation of the radiocapitellar articulation. However, anterior fracture-dislocations of the elbow are distinguished from Monteggia lesions by the fact that both the radius and the ulna dislocate anteriorly and remain associated^7,105. To emphasize these characteristics and to enhance their recognition, we follow Biga and Thomine in referring to this injury as a transolecranon fracture-dislocation of the elbow^7,105.

Many of the capsuloligamentous restraints remain intact with this injury, except when it has been caused by the highest-energy trauma, and most of the failure of the articulation occurs as a disruption of osseous rather than ligamentous components of stability. Fractures of the radial head are uncommon¹⁰⁵. Anatomical fixation of the ulna with restoration of the appropriate contour and dimensions of the trochlear notch (Fig. 4-D) restores stability of the elbow, allowing active motion in the early postoperative period. Fifteen of seventeen patients in our recent series¹⁰⁵ had a good or excellent result, according to the rating system of Broberg and Morrey. The unsatisfactory result for the remaining two patients was related to associated injuries. After an average duration of follow-up of twenty-five months, there was no chronic instability and post-traumatic arthrosis was rare.

Posterior Monteggia Lesions

Penrose suggested that the posterior Monteggia lesion (fracture of the ulna with dislocation of the proximal radioulnar joint in a posterior direction) is a variant of posterior dislocation of the elbow⁹⁷. This injury is most commonly the result of a fall from a standing height by an elderly woman, and people who have osteopenic bone may be more susceptible^53,95,97. The posterior Monteggia lesion may represent an alternative injury pattern that occurs when the mechanism responsible for the posterior dislocation of the ulnohumeral joint results in the failure of osseous rather than ligamentous elements^53,95,97.

One of us (J. B. J.) and colleagues emphasized that many of these fractures have a component of ulnohumeral instability resulting from a large quadrangular or triangular anterior wedge fragment that includes all or most of the coronoid process⁵³. Those authors emphasized that the fracture of the ulna that occurs with a posterior Monteggia lesion can occur in a variety of places on the ulna, from the middle of the shaft to the level of the coronoid process. Their subclassification of these injuries distinguished fractures of the diaphysis (type C), fractures of the metaphysis just distal to the coronoid process (type B), and fractures involving the coronoid process (type A). Type-D fractures are complex and multifragmented and may involve the entire proximal one-third to one-half of the ulna. Most fractures are either type A or type B. Fractures of the radial head are common with all types.

The spectrum of injury occasionally extends more proximally, resulting in a fracture of the ulna at the olecranon process^67,87,122 (Figs. 5-A and 5-B). When the fracture occurs through the olecranon, the coronoid process is also usually fractured, most often as a single large fragment^53,87. Because the radial head is often fractured as well, this pattern of injury may result in complete disruption of the osseous contributions to the stability of the elbow^53,95,97.

The medial collateral ligament complex appears to be spared in this pattern of injury, but the lateral collateral ligament complex may be injured as the radial head dislocates posterolaterally⁴⁵. This may contribute to the ulnohumeral instability that is present with some posterior Monteggia lesions. If there is ulnohumeral instability after stable anatomical fixation of the olecranon, coronoid process, and radial head, protected motion with the elbow in a brace that keeps the forearm in pronation may be sufficient to ensure stability while the lateral ligamentous complex heals^15,62. In contrast, if intraoperative evaluation demonstrates persistent ulnohumeral instability despite pronation of the forearm, then repair of the lateral collateral ligament complex should be considered^84,89.

When the entire spectrum of posterior Monteggia lesions is considered, the results of treatment are found to have been much less predictable than those of anterior Monteggia lesions and anterior or transolecranon fracture-dislocations of the elbow. A review of the experience at Massachusetts General Hospital documented a fair or poor result, according to the elbow performance rating of Broberg and Morrey, for five of eleven patients⁵³. A common problem (noted in four patients) was incomplete reduction of the ulnar fracture with residual subluxation of the proximal radioulnar joint. The apparent key to obtaining a good result is stable anatomical alignment of the ulnar fracture that includes restoration of the trochlear notch with stable anatomical reduction of the fractures of the olecranon and coronoid processes and realignment of the bones of the forearm effecting stable reduction of the proximal radioulnar joint. The importance of preserving the lateral osseous and articular columns through repair or replacement of the radial head is less certain with this injury. Repair or replacement of the radial head should be considered when there is a risk of ulnohumeral or radioulnar instability.

On occasion, it may be possible to reduce and secure a large coronoid fragment while the fracture of the olecranon is hinged open³⁷. The interval created by the fracture allows for direct visualization and manipulative reduction while fixation is achieved with interfragmentary screws entering the dorsal surface of the ulna. Alternatively, realignment of the coronoid process can often be achieved indirectly when distraction is applied. A distractor proves especially useful for repair of complex fractures of the proximal aspect of the ulna with comminution in the depths of the trochlear notch between the olecranon and coronoid processes^70,105. Temporary fixation of the olecranon fragment in an anatomical position with respect to the distal aspect of the humerus can be achieved with use of a large (0.062-inch [0.157-centimeter]) smooth Kirschner wire passed through the fragment and into the distal aspect of the humerus. Distraction applied between this wire and a second pin (a 2.5 or 4.0-millimeter Schanz screw) placed distal to the site of the intended plate in the ulnar diaphysis restores the length of the ulna and the dimensions of the trochlear notch and maintains the reduction while fixation is applied. The distal aspect of the humerus is used as a template to restore the contour of the trochlear notch. Definitive fixation is achieved with a 3.5-millimeter plate contoured around the proximal aspect of the ulna and extending to the tip of the olecranon process. This proximal contour allows more screws to be placed in the often small and osteopenic proximal (olecranon) fragment. To enhance the stability of the fixation further, a large screw inserted through one of the more proximal screw-holes can be directed down the ulnar shaft. By virtue of the contour, the more proximal screws will be directed at a 90-degree angle to the more distal screws, thereby creating an interlocking construct. Dorsal placement of the plate and reconstitution of the anterior ulnar cortex by rigid fixation of separate anterior fracture fragments helps to resist displacement as a result of active muscle forces about the elbow (Fig. 4-D).

Together, the posterior Monteggia and anterior or transolecranon fracture-dislocation patterns of traumatic instability of the elbow may account for a substantial percentage of large (Regan and Morrey¹⁰² type-III) fractures of the coronoid process. We have documented good results of the treatment of large fractures of the coronoid process that form part of a transolecranon or posterior Monteggia lesion, provided that stable, anatomical fixation is achieved^53,105.

Complications and Their Treatment

Chronic Instability

Reconstruction of a chronically unstable elbow is extremely difficult if the instability is related to articular malalignment or loss of bone^14,68. Appropriate treatment of the acute injury is the best way to preserve function of the elbow. Chronic instability after a complex fracture-dislocation may, at times, involve elements of malunion, non-union, or loss of bone with attenuation of ligamentous structures¹⁴. Suggested options for reconstruction include reinforcement of the coronoid process with a bone graft or deepening of the trochlear notch with or without concomitant ligamentous reconstruction^14,56,68,104. Protection of the healing structures with a hinged elbow-distraction device has also been suggested¹⁴.

Stiffness of the Elbow

Loss of motion is common following both simple and complex dislocations of the elbow. It has been found that more than two or three weeks of immobilization for the treatment of a dislocation that is not associated with a fracture greatly increases the risk of a stiff, painful elbow^72,99. This is also true for dislocations with associated fractures. The primary goal of treatment of these injuries is stable restoration of the osseous and articular components that contribute to stability of the elbow so that early active mobilization can be permitted.

There are two options if skeletal fixation remains somewhat tenuous, despite the surgeon's best efforts, after restoration of the osseous and articular anatomy. A hinged elbow distractor can be applied to maintain concentric reduction of the elbow during mobilization^14,65. The distractor limits the potential for displacement of the repaired skeletal elements while they are healing. Alternatively, the fixation can be protected by restricting mobilization with a cast or brace. Healing of the fracture should take precedence over mobilization of the elbow as chronic instability resulting from osseous and articular deficiencies is more difficult to treat than stiffness^14,68,104.

Turnbuckle or static progressive splinting may help to restore motion in the early period after the fractures have healed³⁰. Once the osseous and articular anatomy is restored, release of the elbow capsule is a very predictable method for restoration of motion of the elbow, provided that residual articular incongruity is limited^28,43,73,74.

Heterotopic Ossification

A fracture-dislocation of the elbow may predispose the patient to heterotopic ossification^{23,24,100,119}. Other established risk factors for heterotopic ossification include injury to the central nervous system^24-26,100, a severe burn injury^23,100, and patient-related factors such as gender, age, and presumably genetics^58,100. The influence of operative treatment of fracture-dislocation of the elbow and its timing on the risk of heterotopic ossification remain controversial. Although a strong tradition against delayed operative intervention has been established on the basis of some authors' admonishment that such a delay may increase the risk of heterotopic ossification^24,27,66, other investigators have suggested that the timing of the intervention may not be important⁸⁶. In one recent review, the authors noted that heterotopic ossification developed after eight (16 per cent) of forty-nine injuries of the elbow that were treated operatively and after seven (13 per cent) of fifty-four that were treated non-operatively⁸⁶. There was no association between the time from the injury to the operation and the development of heterotopic ossification.

Forceful manipulation for the treatment of post-traumatic stiffness of the elbow has been found to increase the risk of heterotopic ossification^57,119; however, gentle active and continuous passive motion may help to limit the risk of heterotopic ossification^9,28,85. Radiation therapy⁵⁸ and non-steroidal anti-inflammatory medications^58,100 have both proved effective as prophylaxis against heterotopic ossification after total hip arthroplasty when treatment is initiated within five days postoperatively. While use of these modalities after fracture-dislocation of the elbow might be considered, it must be remembered that radiation therapy can interfere with healing and is associated with a small, but poorly defined, risk of sarcoma^58,100 and non-steroidal anti-inflammatory medications can be associated with renal, gastrointestinal, and hematological complications⁴.

It has long been recommended that resection of established heterotopic bone be delayed to help to ensure maturity of the ossification process and thereby decrease the risk of recurrence²³. While resection less than twelve months after the inception of heterotopic ossification may increase the risk of recurrence in patients who have an injury of the central nervous system, particularly those who have residual cognitive deficits²⁶, this has not been the case in patients who have post-traumatic heterotopic ossification with no other risk factors⁵². A well defined trabecular pattern on standard radiographs remains the best indication that the heterotopic bone is mature^51,73 because levels of serum alkaline phosphatase may decrease before maturation and activity on bone scans can persist long after maturation is well established⁹². Earlier resection of heterotopic bone is appealing in that soft-tissue contractures and degeneration of the cartilage may be less likely to develop and the total period of disability can be reduced⁷³. Our experience with resection of heterotopic bone in patients who have proximal radioulnar synostosis and total osseous ankylosis of the elbow following trauma suggests that recurrence after resection of radiographically mature bone is uncommon even without the use of prophylaxis⁵². Prophylactic radiation therapy has been described as a means for increasing the safety of early resection⁶³. This modality may prove most useful after resection of heterotopic bone in patients who have an injury of the central nervous system.

Arthrosis

Post-traumatic arthrosis is more prevalent following the more complex fracture-dislocations of the elbow^11,50. This higher prevalence may result from a higher-energy mechanism of injury, with direct injury to articular surfaces, as well as residual instability. Residual instability that is sufficient to contribute to the formation of post-traumatic arthrosis may often be subclinical^11,50. Symptomatic arthrosis that is unresponsive to non-operative therapy can be treated with total elbow replacement, with a high degree of success in older and less active patients⁷⁹, but fascial arthroplasty may be a better option for younger and more active individuals^21,74.

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