Extract
Complex instability of the elbow is the condition resulting from both the injury and the resultant loss of function due to damage to the articular surface and the ligamentous structures that stabilize the elbow. The clinical presentation may be subluxation, or it may be incongruity with malalignment in either the lateral or the anteroposterior plane. The specific goal of this report is to provide a rationale for the reliable treatment of a spectrum of these acute injuries. To accomplish this, the relative contributions of the articulation and the ligaments to normal stability, as well as their interactions, must first be defined.
Complex instability of the elbow is the condition resulting from both the injury and the resultant loss of function due to damage to the articular surface and the ligamentous structures that stabilize the elbow. The clinical presentation may be subluxation, or it may be incongruity with malalignment in either the lateral or the anteroposterior plane. The specific goal of this report is to provide a rationale for the reliable treatment of a spectrum of these acute injuries. To accomplish this, the relative contributions of the articulation and the ligaments to normal stability, as well as their interactions, must first be defined.
*Printed with permission of The American Academy of Orthopaedic Surgeons. This article will appear in Instructional Course Lectures, Volume 47, The American Academy of Orthopaedic Surgeons, Rosemont, Illinois, March 1998.
†The author has received or will receive benefits for personal or professional use 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 Orthopedic Surgery, Mayo Clinic, 200 First Street, S.W., Rochester, Minnesota 55905.
Articular Elements
For the purpose of this discussion, it is assumed that the distal part of the humerus is intact. Therefore, the elements of the articulation to be discussed include the radial head and the proximal part of the ulna, specifically the coronoid. The ligamentous structures include the medial collateral ligament and the ulnar part of the lateral collateral ligament. The various interactions between the soft-tissue and articular constructs are well known (Fig. 1). Some of these interrelationships have been quantified.
Radial Head
It is known clinically that the radial head may be resected without altering the normal stability of the elbow11. Therefore, the contribution of the radiohumeral joint to the stability of the elbow is intimately related to and dependent on the integrity of the collateral ligaments. As the radial head involves the lateral aspect of the articular complex, its particular contribution is best studied by evaluating its role in preventing valgus instability. Experimental data have clearly demonstrated that the resistance to valgus stress provided by the radial head is minimum14 when the medial collateral ligament is intact (Figs. 2-A and 2-B). However, the radiohumeral joint offers enough resistance to valgus stress to prevent subluxation of the joint 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. Thus, the radial head is an important secondary stabilizer that prevents valgus instability; 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.
The relationship of the radial head to the ulnar part of the lateral collateral ligament has also been studied experimentally. O'Driscoll et al. demonstrated the clinical manifestation of an attenuated or torn lateral collateral ligament; posterolateral rotatory subluxation can occur in the presence or absence of the radial head12,17. 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 intact15. This suggests that the radial head provides some resistance to posterolateral rotatory instability but, once again, in a secondary capacity.
Proximal Part of the Ulna
The major determinant of stability of the elbow is clearly the ulnohumeral joint. 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 (Figs. 3-A and 3-B)1. A critical amount of articulation is required to maintain stability, but the relevance of these data is tempered by the lack of dynamic studies. At least 30 per cent of the articular portion of the ulna appears to be needed for stability, as this is also the site of attachment of the collateral ligaments.
Coronoid
I know of no experimental data with regard to the amount of the coronoid required for stability with or without ligamentous integrity. This question is currently under investigation in our laboratory. There is a moderate amount of clinical experience suggesting that at least 50 per cent of the coronoid must be present for the ulnohumeral joint to be functional, and this is consistent with our preliminary laboratory findings. An important clinical correlate is the ability to estimate the amount of the coronoid that no longer remains functional on the basis of the opening angle (the angle defined by a line connecting the tip of the olecranon and the tip of the coronoid and a line along the long axis of the ulna). Normally, this angle is 30 degrees; however, fractures involving 50 per cent of the coronoid reduce it to 0 degrees (Figs. 4-A and 4-B).
Ligamentous Contributions
The relative contributions of the medial and lateral collateral ligaments to varus-valgus stability with the elbow in flexion and extension have been studied experimentally13. Investigation has shown that the collateral ligaments provide approximately 50 per cent of the stability of the joint and the articular surfaces, an additional 50 per cent. The only exception is with the elbow in full extension: under this condition, the anterior part of the capsule has been found to resist both varus and valgus stress. This may be important in patients who have a fracture-dislocation with disruption of both the medial and the lateral collateral ligament as well as the anterior part of the capsule.
Principle
The basic principle underlying the treatment of complex instability of the elbow, which has been defined on the basis of careful evaluation of the experimental data and our clinical experience, is that it is essential that all treatment options take advantage of or restore a stable ulnohumeral joint. In this paper, complex instability is discussed on the basis of this principle. The most common conditions are classified primarily according to the articular injury.
The presentation of an isolated fracture of the radial head can be extremely subtle. The prevalence is difficult to ascertain, but in my experience it has occurred in about 1 to 2 per cent of patients who had a fracture of the radial head12. The diagnosis requires a high level of suspicion of injury of the ligament when there is a compression fracture of the radial neck. However, some comminuted fractures may also be due to an axial load and severe valgus stress causing concurrent rupture of the medial collateral ligament.
Treatment of this difficult problem is based first on the recognition of the pathological features and second on the realization that the radial head is an important secondary stabilizer when the medial collateral ligament has been disrupted. The primary goal of treatment is to restore the stabilizing function of the radial head by osteosynthesis if possible. If the fracture is amenable to fixation, the stable arc is determined during the procedure. If the arc is stable and within 40 degrees of extension, unrestricted motion is allowed after two weeks of protection. If dislocation occurs with extension of approximately 60 degrees, the elbow is immobilized for two weeks and motion in a hinged splint, with use of a 30-degree extension stop, is allowed for two weeks. The collateral ligament is not repaired in either instance.
If osteosynthesis is not possible, then restoration of the radiohumeral joint with use of a prosthesis is considered. Unfortunately, the silicone implant does not reliably offer the material characteristics necessary to achieve stability; therefore, the possibility of use of metal implants has been reintroduced5,8,10, although there is limited clinical evidence to document their efficacy. I have therefore resorted, in some instances in which the medial collateral ligament has been disrupted, to replacement with a cadaveric radial head in an effort to provide stabilization (Figs. 5-A and 5-B).
If the radiohumeral joint cannot be 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 the medial epicondyle, allowing direct reattachment. Mid-substance tears are more difficult to repair, and there is less likelihood of achieving immediate stabilization.
All patients should wear a locked hinged brace for protection for four weeks postoperatively; the brace is then unlocked, and motion is allowed in the stable arc. The hinged brace is worn for a total of at least six weeks or until the joint is stable.
There is insufficient clinical experience to provide clear expectations of the results. However, treatment of the acute injury is accomplished much more readily than is reconstruction for chronic or late instability.
This lesion is currently described as a Mason type-IV injury, an extension of the original Mason classification of fractures6,11. The simple, type-I fracture is undisplaced; the type-II fracture involves 30 per cent of the radial head and is angulated more than 30 degrees or displaced more than three millimeters; and the type-III fracture is comminuted. There is little information in the literature to help to define the optimum treatment for fracture-dislocations2,19. Assuming that the coronoid is intact, the basic principle of treatment is first to reduce the dislocation and then to determine the extent to which the ulnohumeral articulation provides stability. Additional treatment is determined according to the type of fracture11.
Type-I Fracture
In type-I injuries, if the arc of motion is stable to within 45 to 50 degrees of extension then nothing more need be done except to place the elbow in a splint with a 60-degree extension stop, which the patient wears for ten, eleven, or twelve days. Full extension is then allowed as tolerated while the elbow is protected with a hinged splint.
Type-II Fracture
Type-II fractures are treated with open reduction and internal fixation. These injuries are the most amenable to such treatment; a rate of success as high as eight of eight was reported by King et al. It is essential that elbows with injuries of the collateral ligaments be treated with open reduction and internal fixation, as these injuries result in chronic instability if the radial head is resected4,5,8. Because these fractures are amenable to such treatment, repair of the collateral ligaments has typically not been necessary in my practice. However, if the elbow remains unstable on examination through the arcs of motion described earlier, then enhanced stability may be obtained by repairing or stabilizing the collateral ligaments.
Josefsson et al. reviewed their experience with nineteen complex injuries of the elbow and recommended open reduction and internal fixation of the radial head fracture as well as repair of the ligament. However, treatment of four of nineteen coronoid fractures had a poor result, suggesting that this component of the lesion must be specifically addressed.
Type-III Fracture
These are the most difficult injuries to treat. Experience has suggested that the entire radial head should be excised acutely if it cannot be fixed2. Open reduction and internal fixation is technically difficult and was reported to be successful in only two of six instances by King et al. During operative excision, the elbow is tested according to the scheme described for type-I fractures. If the elbow is unstable, then direct repair of the collateral ligaments should be carried out. If this does not provide sufficient stability, then a silicone implant may be considered as a temporary spacer if it would enhance stability through an additional 20 degrees.
Alternatively, a metal implant may be considered. A successful result was reported with use of a Vitallium implant in twenty-four of thirty-one patients after a mean duration of follow-up of 4.5 years10. Dislocation of the elbow was an associated injury in twenty-one of the thirty-one patients. More recently, an implant design with a so-called floating radial head was introduced; all of twelve procedures performed with this implant were associated with a successful result at a mean of forty-three months8. Those authors particularly recommended the implant for the treatment of a type-III or complex injury. Alternatively, a cadaveric replacement may be an option; however, there has been little experience with use of such a replacement in the acute setting.
If stability remains a problem, then an external fixator allowing flexion is applied. The indication for use of the external fixator is a joint without a radial head or a healing radiohumeral joint with a torn medial collateral ligament that is inherently and grossly unstable. If use of an implant or open reduction and internal fixation of the radial head does not restore stability, the distraction device allows a congruous alignment of the ulnohumeral joint, and motion lessens the likelihood of stiffness (Figs. 6-A, 6-B, and 6-C). The device is removed in the third to fourth week, and adjustable splints are used to restore motion.
Fractures of the proximal part of the ulna, the olecranon, or the coronoid associated with instability fortunately are the most uncommon of these injuries, as they pose the most difficult treatment problems12. Treatment consists of restoring the integrity of the ulnohumeral joint, as just described. Ideally, this is accomplished by fixation of the fracture if it is amenable to osteosynthesis.
The Mayo classification scheme for fractures of the olecranon is based on displacement, comminution, and stability12. The injury discussed here is termed type III, meaning that the elbow is unstable because of the injury of a collateral ligament and a displaced fracture of the olecranon (Fig. 7).
Fracture of the Olecranon
The type-III fracture of the olecranon is accompanied by ligamentous disruption. 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 as the ulnohumeral joint is inherently stable. Hence, the technique for rigid fixation of the fracture is of paramount importance (Figs. 8-A, 8-B, and 9). O'Driscoll reported his experience with use of a 3.5-millimeter dynamic-compression plate bent at a 90-degree angle to attain a better position on the small, proximal fragment16. Not uncommonly, one fragment may also involve the coronoid. If it does, this is the most important component of the reduction and fixation.
Fracture of the Coronoid
The coronoid is the most important portion of the ulnohumeral articulation. It serves as a site of attachment for the collateral ligaments and resists posterior displacement of the ulna from the pull of the biceps, brachialis, and triceps.
Type-I Fracture
According to the classification of Regan and myself, type-I fractures represent a small chip of the tip of the coronoid and mainly serve as an indicator that the elbow has, in all likelihood, dislocated or at least sustained an injury of the collateral ligaments. 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 usually necessary.
Type-II Fracture
In type-II fractures, as much as 50 per cent of the coronoid is involved and the elbow is usually unstable. Careful examination with the patient under anesthesia reveals whether the joint is stable after reduction (Figs. 10-A and 10-B). 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. If the fragment is too small for fixation, then a heavy number-5 suture is placed through the fragment (or fragments), which is brought to its anatomical location. In the latter situation, or even if osteosynthesis has been carried out but there is concern about stability, the system is neutralized by the application of a distraction device—that is, the external fixator eliminates the dynamic forces that are applied to the fracture site by the muscles that flex and extend the elbow joint. The device allows motion of the ulnohumeral joint while placing a distal distraction force on the ulna, thus protecting the articulation. The distraction device is maintained for three to six weeks, depending on the nature of the injury3. Cobb and I reported our experience with 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.
Type-III Fracture
These injuries are the most difficult to treat as, by definition, they render the ulnohumeral joint grossly unstable as do type-II injuries. If the coronoid is a large fragment and has not been comminuted, it may be fixed with a screw and the joint will be stable. However, because of the large forces transmitted through this relatively small surface area, as with type-II fractures these injuries should be further neutralized with the distraction device.
The severely comminuted coronoid fracture is a very uncommon injury. In this setting, I reduce the elbow and bring the fracture fragments into relative alignment with use of a heavy suture. I avoid removing any bone fragments as they may serve as a basis for substantive healing and formation of callus. The ulnohumeral relationship is maintained in a reduced position by the distraction device.
In every instance, the most important goal is to prevent posterior displacement of the ulna against the trochlea—thus, the concept of neutralization with an external fixator that permits flexion and extension while keeping the articulation aligned and eliminating the disruptive force from muscle contracture (Figs. 11-A, 11-B, and 11-C).
Fracture of the Radial Head and Coronoid with Dislocation
These injuries are the most difficult in this category to treat. The principle is the same as already discussed: the radial head must be fixed or replaced. The coronoid fracture is fixed, if possible, with use of a direct or retrograde screw. In either instance, the complex is protected by the external fixator (Dynamic Joint Distractor; Howmedica, Rutherford, New Jersey). This allows motion but eliminates force on the radial head and the coronoid.
The first principle for treating complex injuries of the elbow is to restore the essential element, the ulnohumeral joint (Fig. 12). This is done by reduction of the intact joint or, if the coronoid or the olecranon has fractured, by osteosynthesis. The second principle is that the radial head is an important secondary stabilizer, so if the collateral ligaments have been injured the radial head must be restored or replaced. Finally, efforts to restore the ulnohumeral articulation are enhanced by protection with an external fixator that allows flexion. The implications for rehabilitation and the exact degree of instability are best determined after the ulnohumeral joint has been reduced and the elbow has been placed through an arc of motion. If there is any tendency for the elbow to subluxate or dislocate within 45 degrees of extension, it should be treated appropriately.
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