ELBOW DISLOCATION

EPIDEMIOLOGY

Elbow dislocation accounts for 11% to 28% of elbow injuries.

Posterior dislocation is most common, accounting for 80% to 90% of all elbow dislocations.

Annual incidence of elbow dislocations is 6 to 8 cases per 100,000 population per year.

Simple dislocations are purely ligamentous.

Complex dislocations are those that occur with an associated fracture and represent slightly less than 50% of elbow dislocations.

Highest incidence occurs in the 10- to 20-year-old age group and is associated with sports injuries; recurrent dislocation is uncommon.

ANATOMY

The elbow is a “modified hinge” joint with a high degree of intrinsic stability owing to joint congruity, opposing tension of triceps and flexors, and ligamentous constraints.

Three separate articulations are:

• Ulnotrochlear (hinge)

• Radiocapitellar (rotation)

• Proximal radioulnar (rotation)

Stability (Fig. 18.1)

• Anterior-posterior: trochlea-olecranon fossa (extension); coronoid fossa, radiocapitellar joint, biceps-triceps-brachialis (flexion).

• The anterior joint capsule is also felt to play a role in ulnohumeral stability.

• Valgus: The medial collateral ligament (MCL) complex

  • Anterior band is the primary stabilizer in flexion and extension.

  • Anterior capsule and radiocapitellar joint function in extension.

• Varus: The lateral ulnar collateral ligament is static, and the anconeus muscle is dynamic stabilizer.

• Function of the MCL

  • Primary medial stabilizer, especially the anterior band.

  • Full extension provides 30% of valgus stability.

  • Ninety degrees of flexion provides >50% of valgus stability.

  • Resection of anterior band will cause gross instability except in extension.

• Lateral ligaments

  • Prevent posterior subluxation and rotation of the ulna away from the humerus with the forearm supination (posterolateral rotatory instability).

     

     

     

Normal range of motion: 0 to 150 degrees flexion, 85 degrees supination, and 80 degrees pronation.

Functional range of motion (ROM) requires: a 100-degree arc, 30 to 130 degrees flexion, 50 degrees supination, and 50 degrees pronation.

• More recent reports suggest increased ROM is needed to perform contemporary activities of

  daily living such as talking on a cell phone or using a computer mouse and keyboard.

  MECHANISM OF INJURY

Most commonly caused by a fall onto an outstretched hand or elbow, resulting in a levering force to unlock the olecranon from the trochlea combined with translation of the articular surfaces to produce the dislocation.

Posterior dislocation: This is a combination of elbow hyperextension, valgus stress, arm abduction, and forearm supination.

Anterior dislocation: A direct force strikes the posterior forearm with the elbow in a flexed position.

Most elbow dislocations and fracture-dislocations result in injury to all the capsuloligamentous stabilizers of the elbow joint. The exceptions include transolecranon fracture-dislocations and injuries with fractures of the coronoid involving nearly the entire coronoid process.

The capsuloligamentous injury progresses from lateral to medial (Hori circle) (Fig. 18.2); the elbow can completely dislocate with the anterior band of the MCL remaining intact. There is a variable degree of injury to the common flexor and extensor musculature.

CLINICAL EVALUATION

Patients typically guard the injured upper extremity, which shows variable gross instability and swelling.

A careful neurovascular examination is essential and should be performed before radiography or manipulation.

Following manipulation or reduction, repeat neurovascular examination should be performed to assess neurovascular status.

Serial neurovascular examinations should be performed when massive antecubital swelling exists or when the patient is felt to be at risk for compartment syndrome.

Angiography may be necessary to evaluate vascular compromise.

• Following reduction, if arterial flow is not reestablished and the hand remains poorly perfused, the patient should be prepared for arterial reconstruction with saphenous vein grafting.

• Angiography should be performed in the operating room and should never delay operative

  intervention when vascular compromise is present.

• The radial pulse may be present with brachial artery compromise as a result of collateral circulation.

  • The absence of a radial pulse in the presence of a warm, well-perfused hand likely represents

    arterial spasm.

• Medial ecchymosis, a sign of MCL disruption, is typically apparent 3 to 5 days after injury.

   

  ASSOCIATED INJURIES

Associated fractures most often involve the radial head and/or coronoid process of the ulna. Shear fractures of the capitellum and/or trochlea are less common.

Acute neurovascular injuries are uncommon; the ulnar nerve and anterior interosseous branches of the median nerve are most commonly involved.

The brachial artery may be injured, particularly with an open dislocation.

RADIOGRAPHIC EVALUATION

Standard anteroposterior and lateral radiographs of the elbow should be obtained.

• Congruence of the ulnohumeral and radiocapitellar joints should be assessed.

Radiographs should be scrutinized for associated fractures about the elbow.

• Valgus stress views at 30 degrees elbow flexion and full forearm pronation, obtained after initial reduction or at surgery, may help identify an MCL injury.

Computed tomography (CT) scans may help identify bony fracture fragments not visible on plain

radiographs.

CLASSIFICATION

Simple versus complex (associated with fracture)

According to the direction of displacement of the ulna relative to the humerus (Fig. 18.3):

• Posterior

• Posterolateral

• Posteromedial

• Lateral

• Medial

• Anterior

   

   

   

  Fracture-Dislocations

Associated radial head fracture: These make up 5% to 11% of cases.

Associated medial or lateral epicondyle fracture (12% to 34%): They may result in mechanical block following closed reduction owing to entrapment of fragment.

Associated coronoid process fracture (5% to 10%): These are secondary to avulsion by brachialis muscle and are most common with posterior dislocation.

• Types I, II, and III (Regan and Morrey), based on size of fragment (Fig. 18.4):

  • Type I, avulsion of the tip of the coronoid process

  • Type II, a single or comminuted fragment involving 50% of the coronoid process or less

  • Type III, a single or comminuted fragment involving >50% of the process

     

     

     

Elbow dislocations that are associated with one or more intra-articular fractures are at greater risk for recurrent or chronic instability.

Fracture-dislocations of the elbow usually occur in one of several distinct, recognizable injury patterns, including:

• Posterior dislocation with a fracture of the radial head

• Posterior dislocation with fractures of the radial head and coronoid process—the so-called “terrible triad” injury

• Varus posteromedial rotational instability pattern injuries associated with anteromedial facet of

  the coronoid fractures

• Anterior olecranon fracture-dislocations

• Posterior olecranon fracture-dislocations

The following observations may be useful in guiding treatment:

• Terrible triad injuries nearly always have a type I or II coronoid fracture including the anterior capsular attachment. Much less commonly, the coronoid fracture is type III.

• In the setting of an olecranon fracture-dislocation, the coronoid fracture can be one simple large

  fragment, it can be fragmented into two or three large pieces (anteromedial facet, central, and lesser sigmoid notch) with or without a tip fragment, or it can be more comminuted.

  Types of Elbow Instability

Posterolateral rotatory instability (elbow dislocations with or without associated fractures)

Varus posteromedial rotational instability (anteromedial coronoid facet fractures)

Olecranon fracture-dislocations

Posterolateral Rotatory Instability (Fig. 18.5)

May range from radiocapitellar instability to complete ulnohumeral dislocation.

Occurs during a fall onto the outstretched arm that create a valgus, axial, and posterolateral rotatory force. The ulna and the forearm supinate away from the humerus and dislocate posteriorly. May also be caused iatrogenically during a lateral approach to the elbow joint, if the ulnar band of the lateral collateral ligament (LCL) is taken down and left unrepaired.

May result in injury to the radial head or coronoid.

Soft tissue injury proceeds from lateral to medial, with the anterior band of the MCL being the last structure injured. Posterolateral instability begins with disruption of the ulna band of the LCL; most traumatic injuries result in avulsion of the ligament from the lateral humerus.

It is possible to dislocate the elbow with the anterior band of the MCL remaining intact.

Varus, Posteromedial Rotational Instability

Occurs with a fall onto the outstretched arm that creates a varus stress, axial load, and posteromedial rotational force to the elbow.

This results in fracture of the anteromedial facet of the coronoid process and (1) injury to the lateral collateral ligament, (2) fracture of the olecranon, or (3) an additional fracture of the coronoid at its base.

This injury occurs without fracture to the radial head, resulting in potentially subtle radiographic findings.

Transolecranon Fracture-Dislocations (Anterior)

Result from a direct blow to the flexed elbow.

Some authors suggest that these injuries may result from the same mechanism that usually creates elbow dislocations, particularly in older osteopenic individuals.

Instability Scale (Morrey)

Type I: Posterolateral rotatory instability; positive pivot shift test; lateral ulnar collateral ligament disrupted

Type II: Perched condyles; varus instability; lateral ulnar collateral ligament, anterior and posterior capsule disrupted

Type IIIa: Posterior dislocation; valgus instability; lateral ulnar collateral ligament, anterior and posterior capsule, and posterior MCL disrupted

Type IIIb: Posterior dislocation; grossly unstable; lateral ulnar collateral ligament, anterior and posterior capsule, anterior and posterior MCL disrupted

GENERAL TREATMENT PRINCIPLES

Restore the inherent elbow stability.

Restore the trochlear notch of the ulna, particularly the coronoid process.

Radiocapitellar contact is very important to the stability of the injured elbow.

The lateral collateral ligament is more important than the MCL in the setting of most cases of traumatic elbow instability.

The trochlear notch (coronoid and olecranon), radial head, and lateral collateral ligament should be repaired or reconstructed, but the MCL rarely needs to be repaired.

MCL will usually heal properly with active motion, and its repair is not necessary for stability.

Simple Elbow Dislocation

Nonoperative

Acute simple elbow dislocations should undergo closed reduction with the patient under sedation and adequate analgesia. Alternatively, general or regional anesthesia may be used.

Correction of medial or lateral displacement followed by longitudinal traction and flexion is usually successful for posterior dislocations (Fig. 18.6).

For posterior dislocations, reduction should be performed with the elbow flexed while providing distal traction.

Neurovascular status should be reassessed, followed by evaluation of stable range of elbow motion.

• Loss of neurologic function after closed reduction is rare but can be an indication for surgical exploration to rule out nerve entrapment.

• Elbows that are stable throughout the ROM should be splinted at 90 degrees flexion, followed

  placement of a hinged orthosis after 3 to 5 days, which allows for a protected full ROM.

• If instability is present in less than 30 degrees of elbow flexion, one should pronate the forearm and reassess elbow stability.

  • If pronation confers elbow stability, the extremity should be splinted with the elbow flexed 90

    degrees and the forearm pronated, followed by placement of a hinged orthosis after 3 to 5 days that maintains forearm pronation.

  • Elbows that sublux in less than 30 degrees elbow flexion and full forearm pronation should be splinted with the elbow flexed 90 degrees and the forearm pronated, followed by placement of a hinged orthosis with forearm rotational control and an extension block.

  • Elbows that are unstable in more than 30 degrees elbow flexion should be considered for surgical management.

Postreduction radiographs are essential.

Hinged bracing is maintained for 6 weeks, with progressive advancement of extension and rotation as stability permits.

Close radiographic evaluation is needed to assess elbow reduction.

After 6 weeks, one can discontinue bracing and start physical therapy with terminal stretching.

Recovery of motion and strength may require 3 to 6 months.

Operative

Surgery is indicated in elbows with instability when placed in >30 degrees elbow flexion, elbows that sublux or dislocate during treatment, or those with associated unstable fractures.

Surgery usually involves open reduction and repair of soft tissues back to the distal humerus. The LCL is addressed first, with reattachment using suture anchors or bone tunnels, followed by reassessment of stability. Consideration of MCL repair is made if instability persists after LCL repair. One could also consider use of hinged external fixation for persistent instability.

Elbow Fracture-Dislocations in General

Nonoperative

The ability to meet treatment goals with nonoperative treatment is rare and surgery is indicated in most fracture-dislocations about the elbow.

Patients who elect nonoperative treatment need to be aware of the potential for instability and the substantial potential for restriction of motion or arthrosis from the radial head fracture.

Operative

The operative measures include fixation or replacement of the radial head and lateral collateral ligament repair.

Most authors do not advocate acute MCL reconstruction.

Most authors, however, do stress the importance of the lateral collateral ligament to elbow stability and advocate reattachment of this ligament to the lateral epicondyle.

When the lateral collateral ligament is repaired, immediate active motion is usually possible (particularly if radiocapitellar contact has also been restored), but up to 10 days of immobilization is reasonable.

“Terrible Triad” Fracture-Dislocations

The addition of a coronoid fracture, no matter how small, to a dislocation of the elbow and fracture of the radial head dramatically increases the instability and the potential for complications.

Not all terrible triad injuries will be unstable, but it may be difficult to predict which injuries will be unstable.

Good results have been reported with fixation of the coronoid or repair of the anterior capsule, fixation or replacement of the radial head, and lateral collateral ligament repair.

This protocol has been shown to restore stability in most cases, but in some patients, either MCL repair or a lateral hinged external fixator may also be necessary if instability persists after reconstruction of the lateral side (Fig. 18.7).

Treatment of a radial head fracture by excision alone in the setting of an elbow fracture-dislocation is associated with a high failure rate secondary to recurrent instability.

COMPLICATIONS

Loss of motion (stiffness): Stiffness following complicated or uncomplicated elbow dislocation is usually the rule. Immobilization of the elbow should generally not go beyond 2 weeks.

Neurologic compromise: Sustained neurologic deficits at the time of injury should be observed.

• The ulnar nerve is most frequently involved. Delayed compromise may present when associated with scar or heterotopic bone formation.

• Spontaneous recovery usually occurs; a decline in nerve function (especially after manipulation)

  and severe pain in nerve distribution are indications for exploration and decompression.

• Exploration is recommended if no recovery is seen after 3 months following electromyography.

• Late ulnar neuropathy may be seen and is associated with loss of elbow extension and scarring in the cubital tunnel.

Vascular injury: The brachial artery is most commonly disrupted during injury.

• Prompt recognition of vascular injury is essential, with closed reduction to reestablish perfusion.

• If, after reduction, perfusion is not reestablished, angiography is indicated to identify the lesion,

  with arterial reconstruction when indicated.

Compartment syndrome (Volkmann contracture): This may result from massive swelling due to soft tissue injury. Postreduction care must include elevation and avoidance of hyperflexion of the elbow. Serial neurovascular examinations and compartment pressure monitoring may be necessary, with forearm fasciotomy when indicated.

Persistent instability/redislocation: This is rare after isolated, traumatic posterior elbow dislocation; the incidence is increased in the presence of an associated coronoid process and radial head fracture (terrible triad of the elbow). It may necessitate capsuloligamentous reconstruction, internal fixation, prosthetic replacement of the radial head, or hinged external fixation.

Arthrosis: May result from persistent elbow instability over a period of time. Greater association with fracture-dislocation of the elbow than simple dislocation.

Heterotopic bone/myositis ossificans:

• Anteriorly, it forms between the brachialis muscle and the capsule; posteriorly, it may form medially or laterally between the triceps and the capsule.

• The risk is increased with multiple reduction attempts, a greater degree of soft tissue trauma, or

  the presence of associated fractures.

• It may result in a significant loss of function.

• Forcible manipulation or passive stretching increases soft tissue trauma and should be avoided.

• The use of indomethacin is controversial for prophylaxis after surgery and in the presence of significant soft tissue injury and/or associated fractures.