Complex Instability of the Elbow

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CHAPTER 29 Complex Instability of the Elbow

Bernard F. Morrey, Shawn W. O’Driscoll

INTRODUCTION

Since the first edition of this book, improvements in the recognition and treatment of complex instability are among the most significant developments in managing elbow trauma. The coexistence of multiple articular and soft tissue injuries is being increasingly appreciated.^9,⁴²

DEFINITION

Complex instability of the elbow is defined as an injury that destabilizes the elbow because of damage to the articular surface and to the ligamentous structures.²¹ Others add soft tissue involvement, including neural and vascular injuries in the diagnosis.³⁶ However, vascular injuries are uncommon in this setting. Over a 10-year period, for example, Moneim and Garst²⁰ documented only two instances of vascular injury among 56 with fracture dislocation injury. The clinical presentation is usually one in which the instability is obvious, but more subtle forms are being recognized.³⁹ In this chapter, the relative contributions of the articulation and the ligaments to normal stability, as well as to their interactions, are first defined. We then offer a rationale for the reliable treatment of a spectrum of these acute injuries.

CONTRIBUTIONS TO NORMAL STABILITY

ARTICULAR ELEMENTS

Although the distal humerus is sometimes involved, for the purpose of this discussion, it is assumed that the distal humerus is intact. Therefore, the articular elements to be considered are the radial head, olecranon, and coronoid. The relative role of these elements to elbow stability have been recently reviewed.²⁷

Radial Head

It is known clinically that the radial head may be resected without altering the stability of the otherwise normal elbow.²⁷ Therefore, the contribution of the radiohumeral joint to elbow stability is intimately related to and dependent on the integrity of the collateral ligaments. Experimental data have clearly documented that the resistance to valgus stress provided by the radial head is minimal when the medial collateral ligament is intact^24,^25,⁴⁰ (Fig. 29-1). However, the radiohumeral joint offers enough resistance to valgus stress to prevent subluxation if the medial collateral ligament is attenuated or torn. The major structure resisting initial valgus displacement, even with an intact radial head, is the medial collateral ligament. If the medial collateral ligament is intact, the radial head offers little resistance to valgus stress, but if the medial collateral ligament is attenuated or torn, the radial head assumes the role of an important stabilizer. Thus, the radial head is an important secondary stabilizer to valgus stability.

FIGURE 29-1 Demonstration of the radial head as a secondary stabilizer when the medial collateral ligament is intact (2) and the radial head may be removed (1). However, if the medial collateral ligament is released after the radial head has been resected, marked instability occurs. The alternative situation is one in which the radial head is left intact. In this setting, when the medial collateral ligament is resected, some instability occurs but the gross instability is seen only when the radial head has been removed-thus the designation of the radial head as a secondary stabilizer.

The relationship of the radial head to the ulnar part of the lateral collateral ligament has been initially defined experimentally by O’Driscoll and associates.^30,³² Today, posterolateral rotatory instability is well recognized to be associated with lateral ulnar collateral deficiency^5,^19,³³ and can occur in the presence or absence of the radial head. However, clinical experience suggests that elbows without a radial head do less well after reconstruction of the ulnar part of the lateral collateral ligament than do those in which the radial head is intact.^2,²⁹ This provides further evidence of the important role of the radial head to resist posterolateral rotatory instability but, once again, in a secondary capacity.

Olecranon

The major determinant of stability of the elbow is clearly the ulnohumeral joint, specifically the coronoid. Although the stabilizing influence of this joint has not been studied to any great extent, the relative contribution of the olecranon in resisting various loading configurations has been shown to be linearly correlated with the extent of resection of the proximal part of the ulna (Fig. 29-2).¹ The critical amount of articulation required for maintaining stability is about 50%. These data may be altered by dynamic forces, but this has not been studied.

FIGURE 29-2 The articular contribution of the proximal ulna in various loading modes and in various flexion positions demonstrates that the articulation contributes to stability to the extent that it is present. Thus, approximately 25% stability is lost when 25% is removed, 50% is lost when 50% is removed. However, the collateral ligaments are contained in the distal 25%; thus, at least 75% and ideally 50% of the olecranon should be present to provide ulnohumeral stability.

Coronoid

The amount of the coronoid required for stability with or without ligamentous integrity and with and without the radial head is just now emerging. Experimental and clinical experience suggests that at least 50% of the coronoid must be present for the ulnohumeral joint to be functional (Fig. 29-3). Absence of the radial head further and dramatically compromises the elbow with a 50% coronoid deficiency. From a practical perspective, we have found it useful to observe that the typical 30-degree angle formed by a line from the intact olecranon and coronoid is reduced to 0 degrees when the critical50% of the coronoid is present (Fig. 29-4). Anatomically and clinically, the coronoid is the subject of intense investigation to better understand fracture patterns, and the “critical portion” needed for stability.⁴

FIGURE 29-3 Experimental study measuring ulnohumeral translation with resection of various portions of the coronoid demonstrates instability both with (A) and without (B) the radial head. However, when as much as 50% of the coronoid is present, the degree of instability is dramatically reduced and the ulnohumeral joint approaches normal. These data were obtained after releasing the ligaments, common flexor-extensor tendons, and capsule. The testing was performed with the elbow in the neutral (sagittal) plane and no unbalanced varus-valgus moments.

FIGURE 29-4 When the coronoid is intact, the line between the tip of the olecranon and the coronoid makes approximately a 30-degree angle with the shaft of the humerus. However, when 50% of the coronoid is absent, a line through the remnant and the tip of the olecranon is approximately parallel to the shaft of the ulna. This information is useful to the clinician in assessing the amount of coronoid present, which has direct implications for treatment options and strategy.

LIGAMENTOUS CONTRIBUTIONS

The relative contributions of the medial and lateral collateral ligaments to varus-valgus stability with the elbow articulation intact and in flexion and extension have been studied experimentally.²³ This investigation has shown that the collateral ligaments provide approximately 50% of the varus-valgus stability of the joint, and the articular surfaces provide an additional 50%. The only exception is with the elbow in full extension: under this condition, the ulnohumeral joint and anterior capsule render the elbow stable to varus-valgus stress, even in the absence of collateral ligaments. The role of the ligaments in conjunction with the articulation is described earlier.

CLINICAL MANAGEMENT: PRINCIPLE

A basic principle underlying the treatment of complex instability is simply that a competent ulnohumeral jointbe attained and maintained.^21,³¹ This is the primary overriding principle.

FRACTURE OF THE RADIAL HEAD WITH ATTENUATION OR TEAR OF THE MEDIAL COLLATERAL LIGAMENT

The presentation of medial ligament injury can be extremely subtle. The prevalence is difficult to ascertain, but in my experience, as an isolated lesion, it has occurred only in about 1% to 2% of patients who had a fracture of the radial head.²² One should have a highlevel of suspicion that an injury to the ligament might be present when there is a compression fracture with or without comminution of the radial neck. Ecchymosis on the medial side of the elbow should be an obvious clue but is often absent.

Treatment

Treatment of this difficult structured problem is based on the realization that the medial collateral ligament tends to heal if the ulnohumeral joint is reduced. Furthermore, the radial head is an important secondary stabilizer to valgus stress when the medial collateral ligament has been disrupted. The primary goal of the treatment strategy is to restore ulnohumeral joint stability. However, a reconstructed medial collateral ligament has been observed to stretch in the absence of radial humeral integrity; hence, if it is amenable to fixation, the fracture is fixed; if not, the head is replaced. If the arc is stable within 40 degrees of extension, unrestricted passive motion is allowed after 7 to 10 days of protection. If dislocation occurs with extension of approximately 60 degrees, the elbow is immobilized for 10 days, after which motion in a Mayo Elbow Brace with a 45-degree extension stop, is allowed for 2 weeks. In our practice, the collateral ligament need not be repaired in those with a stable ulnohumeral, radiohumeral joint. Nonetheless, the popularity of suture anchors has prompted a more aggressive attitude toward ligament repair. Rodgers and colleagues ³⁸ report 88% satisfactory results in 17 patients treated with suture anchors who had major elbow injuries.

If osteosynthesis is not possible, then restoration of the radiohumeral joint with the use of a prosthesis becomes a higher priority. Prostheses of today are considerably more effective than in the past. Therefore, the possibility of use of metal implants has been reintroduced.^7,^12,¹⁵ In some instances in which the medial collateral ligament has been disrupted, replacement of the radial head with an allograft has been performed as an alternative method of providing stabilization (Fig. 29-5A and B).

FIGURE 29-5 A, Radiograph showing gross valgus instability in a patient who had resection of the radial head in the presence of an unrecognized disruption of the medial collateral ligament. B, Two years after reconstruction with an allograft, the patient had excellent function.

If the radiohumeral joint cannot be effectively reconstructed, it is appropriate to address the injury of the medial collateral ligament directly and to repair it as soon as possible. The ligament may be avulsed from its origin or insertion, allowing direct reattachment. Midsubstance tears are more difficult to repair, and there is less likelihood of achieving immediate stabilization.

Finally, a hinged external fixator is applied in those circumstances in which it is desirable to protect a fractured radial head, the coronoid, or to protect a ligament repair (see Chapter 33).^3,^13,¹⁷ There are several articulated fixators available, but for this indication, Kamineni has shown that the simple half-pin configuration of the Dynamic Joint Distractor (DJDII) (Stryker, Mahwah, NJ) is effective to stabilize the joint even in the absence of both collateral ligaments. Hence, because of cost and simplicity, this is our choice of devices (Fig. 29-6).¹³ If the fixator is not used, patients are fitted with the Mayo Brace in the locked mode for protection for about 2 weeks postoperatively; the brace is then unlocked, and motion is allowed in the brace through the stable arc. The hinged brace is worn for a total of at least 6 weeks or until the joint is considered stable.

FIGURE 29-6 A, Radiograph showing a severe fracture-dislocation of the elbow (a Mason type-III fracture of the radial head). The fracture of the radial head was treated with internal fixation. Because of gross instability, additional stabilization was achieved with use of the Dynamic Joint Distractor (B).

FRACTURES OF THE RADIAL HEAD WITH DISLOCATION OF THE ELBOW

This lesion is often referred to as a Mason type IV injury, an extension of the original Mason classification of fractures ^10,²⁷ (see Chapter 24). This association was observed in 59 of the 333 radial head fractures assessed for associated injuries.⁴² The simple principle defined earlier continues to be relevant. If it is clearly demonstrated that the coronoid is intact, the basic treatment principle is first to reduce the dislocation and then to determine the extent to which the ulnohumeral articulation is inherently stable. Treatment of the radial head is determined according to the type of fracture.²⁷

Type I Fractures

In type I injuries, if the elbow is stable to within 45 or 50 degrees of extension, nothing more need be done except to place the elbow in a splint at 60 degrees flexion to be worn for 1 to 2 weeks. Full extension is then allowed as tolerated usually without protection.

Type II Fractures

Type II fractures are treated by open reduction and internal fixation. These injuries are the most amenable to such treatment. King and associates ¹⁴ report a successful outcome in all eight patients so treated. It isessential that elbows with injuries of the collateral ligaments be treated with open reduction and internal fixation, because these injuries result in chronic instability if the radial head is resected.^6,^7,^12,³⁷ Because these fractures are amenable to such treatment, repair of the medial collateral ligament to a great extent becomes personal preference. One of us (BFM) rarely fixes this ligament, whereas the other author (SOD) is more aggressive in this regard. However, if the elbow remains unstable on examination through the arcs described earlier, enhanced stability is obtained by repairing or stabilizing the medial collateral ligament. Josefsson and associates¹¹ reviewed their experience with 19 complex injuries of the elbow and recommended open reduction and internal fixation of the radial head fracture as well as repair of the medial ligament. However, treatment of 4 of 19 coronoid fractures had a poor result, suggesting that this component of the lesion must be specifically addressed. Without question, the lateral ulnar collateral ligament must be formally and securely fixed.

If uncertainty as to stability still exists, we then resort to the use of the external fixator.

Type III Fractures

These are the most difficult injuries to treat. Experience has suggested that the entire comminuted radial head should be excised acutely if it cannot be fixed.² Open reduction and internal fixation is technically difficult and was reported to be successful in only two of six instances by King and colleagues.¹⁴ We now know those fractures with more than four fragments should be excised, not fixed. A prosthesis is then used and is considered an essential component of the treatment. A review of the literature regarding treatment with several metallic radial head implants reveal an overall success rate of about 90% when managed acutely (Table 29-1). The elbow is tested according to the scheme described for type I fractures. If the elbow is unstable, then direct repair of the medial collateral ligament might be considered.

TABLE 29-1 Summary of 15 Years Literature Involving Prosthetic Radial Head Replacement

If stability remains a problem, a hinged external fixator that allows elbow motion is applied. The indication for use of the external fixator is a joint with a healing radial head with a torn medial collateral ligament that remains unstable (see Chapter 33). If use of an implant or open reduction and internal fixation of the radial head does not restore stability, the distraction device allows congruous alignment of the ulnohumeral joint, allowing motion which lessens the likelihood of stiffness or of fracture displacement. The device is removed as early as the third to fourth week and as late as 12 weeks, after which adjustable splints are used to restore motion (see Chapter 12).

FRACTURE OF THE PROXIMAL PART OF THE ULNA

Fractures of the proximal part of the ulna, both the olecranon or coronoid, pose major treatment problems.²² As always, management consists of restoring the integrity of the ulnohumeral joint, as just described. Ideally, this is accomplished by reduction and stabilization of the fracture.

FRACTURE OF THE OLECRANON

The Mayo classification scheme for fractures of the olecranon is based on displacement, comminution, and stability ²² (see Chapter 25). The injury discussed here is termed type III, meaning that the elbow is unstable because of injury both to a collateral ligament and from a displaced fracture of the olecranon (Fig. 29-7). In fact, some might appropriately consider this a Monteggia variant⁹ and others have referred to this as a transolecranon anterior fracture dislocation.^28,³⁷

FIGURE 29-7 Left and Right Panels, A Mayo type III ulnar fracture may or may not be comminuted, but it is characterized by attenuation or disruption of the medial collateral ligament or the ulnar part of the lateral collateral ligament, or both. This is characterization by instability of the forearm.

The type III fracture of the olecranon is accompanied by ligamentous disruption. The principle is again applied: stabilize the ulnohumeral joint (Fig. 29-8). If there is minimum comminution of the olecranon, rigid plate fixation restores the ulnohumeral joint. If the olecranon is rigidly fixed, then the unstable injury is converted to a stable one because the ulnohumeral joint is inherently stable. Hence, the technique for rigid fixation of the fracture is of paramount importance (see Fig. 29-8). A 3.5-mm dynamic compression or low-contour dynamic compression plate bent at an 80-degree angle or precontoured plate applied to the posterior surface of the ulna permits excellent fixation on the small proximal fragment.³² Commonly, one fragment may also involve the coronoid. If it does, this is the most important component of the reduction and fixation. If these principles are followed, a success rate of 88% has been reported in series of 8²⁸ and 15 patients.³⁷

FIGURE 29-8 When there has been disruption of the collateral ligament and alteration of the ulnohumeral joint, the ulnohumeral joint must be somehow stabilized. This may occur by rigid plate fixation if the fracture allows (A), by rigid fixation of the coronoid if the fracture allows (B), or by neutralization of the ulnohumeral relationship if the fractures do not allow rigid fixation (C).

FRACTURE OF THE CORONOID

Without question, the coronoid is the most important portion of the ulnohumeral articulation. This is related to the posteriorly directed forces of both the biceps and the triceps that tend to “drive” the humerus into the coronoid fracture (Fig. 29-9). The base also serves as a site of attachment for the collateral ligaments.

FIGURE 29-9 A, Radiograph showing a Mayo type III ulnar fracture and a fracture of the radial head. B, The fracture was treated with rigid plate fixation, and resection of the radial head was required; stabilization of the joint was supplemented by an external fixator (B). Excellent result at 1 year (C).

Type I Fracture

According to the classification of Regan and Morrey, type I fractures represent a small chip of the tip of the coronoid and serve mainly as an indicator that the elbow has dislocated or at least displaced sufficiently to have sustained an injury of the collateral ligaments.³⁵ The ulnohumeral joint is stable, and rehabilitation is similar to that recommended for type I fracture-dislocations of the radial head. Open reduction is not necessary if the elbow is stable. Occasionally, the fragment will become symptomatic as a snapping or catching requiring arthroscopic removal.¹⁶

Type II Fracture

In type II fractures, as much as 50% of the coronoid is involved and the elbow is usually unstable, especially if the radial head is also fractured. Careful examination with the patient under anesthesia reveals whether the joint is stable after reduction (Fig. 29-10). The threshold for fixation varies with individual surgeons but we are aggressive with any hint of instability. If the reduction is stable, motion within the stable arc, as described previously, may be allowed (see Fig. 29-10). If posterior displacement occurs with less than 40 to 45 degrees of flexion, the articulation is considered inadequate, and the ulnohumeral joint must be stabilized. If the fracture fragment is large enough for fixation, osteosynthesis with a single screw is performed. We approach the fracture laterally if the radial head is to be removed and medially if the head is intact. If the fragment is too small for fixation, a heavy No. 5 suture is placed through the fragment (or fragments), which is brought to its anatomic location and tied through drill holes placed in the ulna. In the latter situation, or even if osteosynthesis has been carried out but there is concern about stability, the elbow may need to be neutralized by the application of a hinged external fixatora-as the external fixator eliminates the dynamic forces that are applied to the fracture site by the muscles that flex and extend the elbow joint (Fig. 29-11). The device allows motion of the ulnohumeral joint while a distraction force is placed on the ulna, thus protecting the articulation. The device is maintained for 3 to 6 weeks, depending on the nature of the injury.³ Cobb and Morrey³ reported on seven such injuries and documented a successful outcome in six. In that series, the coronoid fracture was treated as described earlier, and a distraction device was applied in each instance.