Lateral Instability

Posterolateral rotatory instability of the elbow results from insufficiency of the lateral ligamentous and muscular support of the elbow. The lateral collateral ligament originates at the lateral epicondyle, blending distally with the annular ligament to form a broad common insertion onto the proximal ulna ( Fig. 86-1 ). Lateral joint laxity allows the proximal forearm (ulna and radius) to subluxate away from the humeral trochlea when axially loaded in supination. Except in the acute setting when seen in association with dislocation or fracture–dislocation, it often presents with subtle findings on history and examination. The diagnosis thus requires a high index of suspicion.

Schematic drawing (A) and cadaveric specimen (B) showing the anatomy of the lateral collateral–annular ligament complex. The overlying extensor muscles and supinator fibers have been removed. The collateral ligament originates at the base of the lateral epicondyle and fans out, blending with the annular ligament. These form a broad conjoined insertion onto the proximal ulna along the supinator crest, just posterior to the proximal radioulnar joint.

(Copyright Mark S. Cohen, Chicago, IL.)

Patients with chronic lateral elbow instability present with a variable history. Previous trauma may involve a documented dislocation of the elbow or an injury without dislocation. In most cases, the mechanism of injury involves a fall onto the involved extremity, with a combination of axial compressive, external rotatory, and valgus forces applied to the elbow. Some cases of lateral instability are iatrogenic, such as those seen after overly aggressive debridement of the soft tissues at the lateral epicondyle for recalcitrant epicondylitis. The condition has also recently been reported in patients with epicondylitis who have not undergone surgical intervention. The association of posterolateral instability with epicondylitis and possibly multiple steroid injections is not entirely clear. Finally, the condition has been reported in patients with chronic cubitus varus deformity of the elbow.

When the lateral ligamentous support of the elbow is lost, symptoms of pain and instability typically follow. It is difficult to compensate for a loss of lateral joint stability because the elbow is subjected to varus stress during many daily activities. Simple abduction of the shoulder away from the body produces a varus moment to the joint. The indication for surgical intervention for lateral elbow insufficiency is recurrent symptoms as a result of documented instability. This typically manifests as painful episodes when the elbow is loaded in certain positions, commonly with the joint in a slightly flexed position and the forearm partially supinated. It is not uncommon, for example, for patients to report pain and a sensation of the elbow “giving way” when they arise from a chair or perform certain lifting activities with the involved extremity. In cases of greater instability, these episodes can occur with very minor loading. Mechanical complaints of popping or catching of the elbow are not uncommon.

Findings on physical examination in patients with chronic lateral collateral ligament insufficiency are characteristically benign. Range of motion and grip strength are typically normal, although a slight loss of extension can be observed. If the initial injury was remote, patients may have only minor discomfort to palpation near the lateral elbow. Infrequently, a fluid collection representing a synovial fistula may be observed. Although it is difficult to show frank posterolateral instability in the office, often subtle subluxation of the lateral elbow can be appreciated with the appropriate provocative maneuver. The posterolateral rotatory instability test is performed with the arm adducted and the forearm in supination, with the elbow partially flexed. The elbow is loaded in supination, with slight axial and valgus force applied. Instability is appreciated as gapping at the ulnohumeral articulation as the ulna and radial head subluxate from the humerus. The elbow will subluxate during this maneuver, but will not dislocate. Patients with lateral rotatory instability characteristically resist this provocative maneuver. Guarding in effect constitutes a positive apprehension test result. The examination is easiest to perform with muscular relaxation under anesthesia.

Findings on plain radiographs are usually negative, although a small avulsion fragment off of the lateral epicondyle may be observed. Stress radiographs can be obtained to aid in the diagnosis ( Fig. 86-2 ). A true lateral elbow film can be taken with the forearm maximally supinated during the provocative maneuver. This may show a widened ulnohumeral articulation with an inferiorly subluxated radial head, now posterior to the midline of the capitellum. We have recently begun using anteroposterior stress radiographs with an applied varus load to the elbow. This may show pathologic gapping of the lateral joint (see Fig. 86-2 ). Under normal circumstances, there should be little or no widening between the radial head and the capitellum with applied varus stress. When in doubt, contralateral comparison films can be used to help define asymmetry. Although not typically used or required to make the diagnosis, a magnetic resonance scan commonly shows signal change at the epicondyle and may show disruption of the lateral collateral and tendinous origins at the humeral epicondyle ( Fig. 86-3 ).

A, Lateral stress radiograph taken in a patient with lateral collateral instability of the elbow. The image was taken with provocative stress applied using the rotatory instability test. Note the gaping at the ulnohumeral articulation and posterior translation of the radial head, now projecting posterior to the center of the capitellum. B, Anteroposterior stress radiograph in a patient with lateral collateral instability of the elbow. This image was taken with varus stress applied to the joint. Note the gross gapping of the lateral joint between the radial head and the capitellum, confirming the diagnosis.

(Copyright Mark S. Cohen, Chicago IL.)

Magnetic resonance imaging of the elbow in a patient with chronic lateral collateral ligament insufficiency. Fluid is seen between the collateral ligament and extensor tendon origins and the lateral epicondyle. Magnetic resonance imaging can help to confirm the diagnosis and rule out other pathologic processes near the lateral elbow.

(Copyright Mark S. Cohen, Chicago IL.)

Acute Lateral Ligament Repair

Although all elbow dislocations involve some disruption of the lateral elbow ligaments and soft tissue origins at the humeral epicondyle, surgical repair is rarely needed unless there is an associated significant fracture. The elbow is an extremely congruous joint. Without significant loss of articular support, the medial and lateral soft tissues will heal and recurrent instability is extremely rare in “simple” dislocations without fracture.

In the setting of fracture-dislocation, after repair or replacement of the radial head, the lateral ligament and extensor tendon origins are repaired. The most common injury pattern involves proximal attenuation or avulsion of these structures from the lateral epicondyle ( Fig. 86-4 ). In this setting, direct repair of the entire soft tissue sleeve (containing the collateral ligament and extensor tendon origins) back to the humerus restores stability to the lateral elbow. Direct repair is facilitated by placing a running, locking suture into the ligament and tendinous origin, which are then passed through the humerus and tied over the posterior humeral column (see Fig. 86-4 ). Transosseous sutures are preferable to bone anchors because they allow the soft tissue to be pulled and tensioned directly to bone securely.

A, Intraoperative photograph showing a bare lateral epicondyle in a patient who had elbow fracture–dislocation with acute instability. Note how the entire soft tissue sleeve, including the lateral ligament and extensor tendon origins, has torn away from the humerus. B, Schematic drawing showing transosseous repair with a running, locking suture passed through the humeral isometric point and tied over the posterior humeral column.

(Copyright Mark S. Cohen, Chicago IL. B, Courtesy of Hill Hastings, II, MD, and the Indiana Hand Center.)

Lateral Ligament Reconstruction

Chronic lateral elbow instability typically requires a more complex reconstruction. An examination under anesthesia may be performed to confirm the diagnosis of posterolateral rotatory instability of the elbow. For deep exposure, an extended Kocher incision is used, beginning along the supracondylar humeral ridge and passing distally over the lateral epicondyle toward the ulna. Deep dissection is continued along the lateral supracondylar ridge, beneath the epicondyle, and distally between the anconeus and the extensor carpi ulnaris. The anconeus is reflected posteriorly with the triceps and the extensor carpi ulnaris is retracted anteriorly, showing the deep collateral and annular ligament layer overlying the radial head. More proximally, the capsule is maintained over the lateral ulnohumeral joint (the “soft spot” of the elbow).

The center of rotation or isometric origin of the lateral ligament of the elbow is at the base of the epicondyle, where the epicondyle flattens onto the lateral aspect of the capitellum. This point is at the center of the capitellum (and trochlea) and at the intersection of a line connecting the anterior cortex of the humerus with the axis of the radial head when reduced. Clinically, the isometric point is most easily identified by finding the center of the curve of the capitellum. Once this point is defined, it is important to appreciate that the actual entry hole in the humerus is designed so that the most posterior margins of the tunnel define the isometric point ( Fig. 86-5 ). The graft will functionally heal along this posterior cortex. Divergent holes are placed out posteriorly through the lateral supracondylar ridge. Care is taken to allow for an adequate bone bridge between exit points along the posterior humeral column. Alternatively, it is possible to use a single humeral tunnel and tie the sutures over an EndoButton (Smith & Nephew, Andover, MA) rather than a bone bridge.

A, Schematic drawing showing the appropriate position for the humeral tunnel origin. Note how the tunnel begins anterior to the center of the capitellum (isometric point). In this way, the most posterior margin of the tunnel defines isometry. B, Intraoperative photograph showing placement of the humeral and ulnar tunnels. Note that the ulnar tunnels are drilled just posterior to the proximal radioulnar joint. C, Schematic drawing showing the “docking” technique used to secure the free tendon graft. A two-ply graft is created by cutting the graft length so that both tendon ends are pulled into the humerus. The sutures alone are passed through the bone tunnels posteriorly. Tension is provided and the graft is secured by tying the sutures over a humeral bone bridge. D, Intraoperative photograph showing the final graft position after it has been passed through the humeral tunnels. Note how the arms of the graft have been sutured to one another and the underlying native soft tissue to reinforce the reconstruction. E, The anconeus and extensor carpi ulnaris fascia have been closed over this free tendon graft, completing the procedure.

(Copyright Mark S. Cohen, Chicago IL. A and C, Courtesy of Hill Hastings II, M.D. and The Indiana Hand Center.)

It is important to understand the normal insertion of the lateral collateral and annular ligament complex when fashioning the ulnar tunnels. The ligament inserts along the supinator crest of the ulna, beginning at the proximal margin of the radial head and extending distally for approximately 2 cm, as noted earlier. Thus, an entry hole is made in the lateral cortex of the ulna at the proximal margin of the radial head and several millimeters posterior to the joint using sequential drill bits. An exit hole is created several centimeters distally along the supinator crest (see Fig. 86-5 ). Curettes are used to create a path within the ulna between the drill holes.

Next, the tendon graft is obtained. The palmaris longus is most commonly used. When it is not available, alternative grafts include the contralateral palmaris, all or part of the flexor carpi radialis, a hamstring tendon (the gracilis is most appropriate in terms of diameter), and possibly the plantaris tendon. Allograft tendons may be considered as well. When available, the palmaris is most commonly harvested through multiple transverse incisions in the forearm. A tendon stripper may be used once the graft has been freed into the mid-forearm.

The free tendon graft is prepared by placing a running, locking nonabsorbable suture on one end (typically, the distal tendon.) A double-armed suture attached to a Keith needle (FiberLoop, Arthrex, Inc., Naples, FL) can be used to facilitate this. The graft is threaded through the distal tunnel. The prepared end of the graft is then placed into the humeral entry hole, with the sutures exiting one of the humeral tunnels. Although the original description of the technique suggested the use of a four-ply graft, most surgeons now use a “docking” technique popularized on the medial side of the elbow for ligament reconstruction in the throwing athlete (see Fig. 86-5 ). The goal of this method is for both arms of the free graft to be “docked” within the humeral tunnel, with only the two sets of sutures exiting the posterior humerus. Thus, once part of the graft is within the humeral tunnel, the second arm of the graft is cut at an appropriate length that will allow it to end within the humerus. The second end of the graft is then prepared with a separate running, locking suture and these are passed out the other humeral tunnel. Traction on the two sets of graft sutures should allow the two-ply graft to become taut as it advances within the humerus. If one tunnel and an EndoButton are used, the suture ends are threaded through the eyelets of the button.

The forearm is then partially flexed and fully pronated, reducing posterolateral joint subluxation. The forearm is lifted off of the table to remove varus stress. The tendon graft is then pulled taut and the four suture strands are tied, completing the reconstruction. The arms of the free tendon graft can be sutured to one another and to the underlying collateral and annular complex to reinforce the reconstruction. The elbow can be taken through a range of motion once the graft is secured. It is now possible to appreciate the function of the graft, which acts as a reinforcement to the radial collateral and annular ligament complex. It holds up the proximal ulna to the humeral trochlea and provides a lateral restraint to the radial head, not allowing it to subluxate from the capitellum in supination.

The split in the anconeus and extensor fascia is then repaired and the skin is closed in layers (see Fig. 86-5 ). A compressive dressing is applied, with an orthosis maintaining the elbow in approximately 90 degrees of flexion and the forearm in neutral or slight pronation.