CHAPTER 48 Lateral Collateral Ligament Insufficiency
INTRODUCTION
The lateral collateral ligament complex is one of the main structures implicated in the stability of the elbow joint. Insufficiency of the lateral collateral ligament com-plex is present in many patients with elbow instability. Several basic science and clinical studies have im-proved our understanding of the contributions of the lateral collateral ligament complex to elbow stability, the etiology of lateral collateral ligament insufficiency, the value of different clinical and imaging tests for identification of this entity, and the outcome of surgical repair or reconstruction. The term posterolateral rotatory instability has been coined to describe the clinical condition that results from lateral collateral ligament complex insufficiency.25
BASIC SCIENCE
Several ligamentous structures may be identified on the lateral aspect of the elbow joint (see Chapter 2). The ligamentous fibers connecting the lateral humeral epicondyle with the lateral aspect of the ulna seem to be the most important for elbow stability on the lateral side. These fibers, commonly referred to as lateral ulnar collateral ligament,22 attach distally into the tubercle of the supinator crest (Fig. 48-1). More anterior fibers originated at the lateral humeral epicondyle, named by some as radial collateral ligament, blend with the fibers of the annular ligament. Unlike the medial side of the joint, morphologic and histologic studies have not been able to show distinct ligaments on the lateral side of the joint consistently.5,14
Lateral collateral ligament complex insufficiency allows excessive posterolateral displacement of the proximal forearm relative to the distal humerus. The contribution of the lateral collateral ligament complex to elbow stability has been investigated in several cadaveric models. Release of the whole lateral collateral ligament complex has been required in most experimental settings to produce a significant increase in varus and posterolateral displacements.5,8,13,27,29,35 Isolated section of the ulnar insertion of the lateral ulnar collateral ligament has not been shown to promote dramatic elbow instability in all cadaveric studies.5,27–29 However, reconstruction of the lateral ulnar collateral ligament with a tendon graft restores varus and posterolateral stability in the laboratory.17 The overlying common extensor-supinator group has also been shown to play a major role in elbow stability.5,9 There is a complex interplay be-tween the lateral collateral ligament complex and other elbow structures, including the coronoid and radial head.6,7,15,34
ETIOLOGY
TRAUMA
The lateral collateral ligament complex may be damaged as a result of trauma to the elbow, resulting in elbow dislocation, fracture-dislocation, subluxation, or ligamentous sprain (Box 48-1). McKee et al.21 reported on the soft tissue injury patterns identified in 10 dislocations and 52 fracture-dislocations treated surgically. The lateral collateral ligament complex was disrupted in all cases; proximal avulsion was the most common failure mode, followed by midsubstance rupture. The common extensor-supinator group was injured in 66% of the cases. The anterior bundle of the medial collateral ligament was injured in approximately 50% of the cases. Less severe injuries causing dislocation or an elbow sprain (usually hyperextension or varus stress) may also damage the lateral collateral ligament complex if they place substantial strain on the ligament fibers.
When injured, the medial collateral ligament seems to heal without residual clinically significant medial-sided instability in most patients.10 On the contrary, persistent lateral-sided instability seems to be more frequent, but the reasons are unclear: It may be related to a decreased healing potential, as seen in other anatomic locations such as the lateral side of the knee joint; the constant tensile gravitational loads imposed on the injured lateral side with elbow use; or the more common association with additional injuries such as radial head or coronoid fractures. Lateral collateral ligament insufficiency should be suspected in patients with recurrent dislocation, subjective instability, lateral-sided pain, and a history of elbow trauma.
CHRONIC ATTRITION
Chronic attrition secondary to repetitive valgus stress is a well-known mechanism leading to medial collateral ligament insufficiency. Chronic attrition of the lateral collateral ligament complex may occur in rare situations such as long-term crutch-walkers (paraplegics, poliomyelitis). Post-traumatic or congenital cubitus varus deformity is recognized as a risk factor for chronic attrition of the lateral collateral ligament complex and tardy posterolateral rotatory instability.1,26 With varus malalignment, triceps contraction has been hypothesized to force posterolateral rotatory subluxation and eventually lead to attenuation of the lateral collateral ligament complex. In addition, one cadaveric study has shown increased strain on the lateral collateral ligament complex with more than 25 degrees of varus deformity and lateral joint line opening with more than 20 degrees of varus deformity.3 In this setting, corrective osteotomy should be considered as an adjunct to lateral collateral ligament reconstruction to prevent failure. Insufficiency of the lateral collateral ligament has also been identified in patients with tennis elbow and no prior surgery16; insufficiency in this setting may be secondary to ligamentous involvement by the same pathologic process affecting the common extensor group4 or the detrimental side effects on collagen fibers of repeated steroid injections.4,16
IATROGENIC INJURY
Inadvertent damage of the lateral collateral ligament may occur during surgical procedures on the lateral side of the joint. Surgical treatment of tennis elbow may compromise the lateral collateral ligament complex if the release or débridement of the common extensor origin are too extensive, especially when the lateral epicondyle is denuded off soft tissues. Exposure of the radial head or capitellum for fracture fixation or chronic reconstruction may also jeopardize the lateral collateral ligament complex, especially when Köcher’s interval is used or the joint needs to be subluxed or dislocated in order to complete the surgical procedure.12,23,33 Special attention is required when performing surgery on the lateral side of the elbow joint to avoid damage to the lateral collateral ligament complex. Formal repair of the damaged ligament should always be part of the wound closure.
DIAGNOSIS
PRESENTATION
The clinical expression of lateral collateral ligament complex insufficiency varies considerably depending on the etiology, severity, associated pathology, previous surgery, and activity level (Box 48-2). Some patients may complain of recurrent episodes of frank elbow dislocation. However, most commonly patients complain of more subtle symptoms, including lateral-sided elbow pain, mechanical symptoms (clicking, catching, snapping, locking) or subjective instability.33 Patients with ligamentous insufficiency after a fracture-dislocation may present with more severe pain or stiffness secondary to the associated injuries. Commonly, most patients with lateral collateral ligament complex insufficiency report a previous history of trauma or surgery. In patients with previous surgery, it is important to determine if the preoperative symptoms were corrected by the surgery or if on the contrary surgery had no effect or occasioned a whole new constellation of symptoms.
Subtle elbow instability is reflected by the inability of the patient to push with the affected upper extremity to stand up from a seat,31 open a heavy door, or similar activities that require active elbow extension against resistance with forearm supination. However, instability episodes are difficult to identify as such by the patient, who often reports pain when attempting to perform the above-mentioned activities.
PHYSICAL EXAMINATION
A detailed physical examination should help identify basic information such as the specific location of the pain and elbow range of motion (see Chapter 4). The location of previous skin incisions and the presence of deformity should be noted. As mentioned earlier, cubitus varus predisposes to tardy posterolateral rotatory instability. In addition, lateral skin incisions centered posterior to the midcoronal plane may be associated with inadvertent ligamentous damage. The integrity of the medial and lateral collateral ligament complex should be tested in all cases. Examination maneuvers for instability may be masked by associated pathology (stiffness or an absent radial head, for example). In the author’s experience, pure varus stress does not allow reliable assessment of the competency of the lateral structures. Several other physical examination maneuvers have been described to specifically test the lateral collateral ligament complex:
Posterolateral Rotatory Drawer Test
This test demonstrates posterolateral subluxation of the proximal radius and ulna with forced supination. It is best performed with the patient laying supine and the upper extremity overhead to lock the shoulder in internal rotation (Fig. 48-2). Forced supination of the forearm in approximately 45 degrees of flexion will induce abnormal excessive posterolateral subluxation of the elbow. The test is best demonstrated when forced supination is combined with valgus torque and axial compression. In some cases, subluxation may not be demonstrated but patients show apprehension with the maneuver.24
