I. Overview/Epidemiology
A. The elbow is the second most commonly dislocated joint in adults and the most commonly dislocated joint in children.
B. Dislocations represent 10% to 25% of all elbow injuries.
C. The highest incidence is in patients aged 10 to 20 years.
II. Pathoanatomy
A. The stability of the elbow joint is provided by static and dynamic constraints.
1. Primary static constraints (
Figure 1)
a. Ulnohumeral articulation
b. Anterior bundle of the medial collateral ligament (MCL)
c. Lateral collateral ligament (LCL) complex, including the lateral ulnar collateral ligament (LUCL)
2. Secondary static constraints (Figure 1).
a. Capsule (most stabilizing effect with elbow extended)
b. Radiocapitellar articulation (important secondary valgus stabilizer)
c. Common flexor and extensor tendon origins
3. Dynamic constraints—The muscles that cross the elbow joint (the anconeus, triceps, and brachialis); these muscles apply compressive force.
B. Mechanisms of injury for posterolateral dislocations
1. The classic mechanism is thought to be a combination of axial load, external rotation of the forearm (supination), and valgus force (valgus posterolateral). A progressive circular disruption of the soft tissues occurs (
Table 1).
2. A recent biomechanical study suggested that posterior elbow dislocation may occur with a combination of axial load, external rotation of the forearm, and varus (varus posteromedial).
3. Some authors believe that the MCL is always disrupted with elbow dislocation.
4. More than one mechanism may exist for posterior dislocation.
III. Evaluation
A. Physical examination
1. Neurovascular status should be documented.
2. Rule out open injuries and compartment syndrome, which require immediate surgical treatment.
B. Imaging
1. Plain AP and lateral radiographs of the elbow are necessary to document congruent reduction.
[Figure 1. The static constraints in the elbow are analogous to the defenses of a fortress. The primary static constraints to elbow instability are the ulnohumeral articulation, the anterior bundle of the MCL, and the LCL complex (including the LUCL). The secondary constraints include the capsule, the radiocapitellar articulation, and the common flexor and extensor tendon origins.]
[Table 1. Stages of Soft-Tissue Disruption]
2. Oblique views may be useful to identify periarticular fractures.
3. CT is useful to identify associated osseous injury.
IV. Classification
A. Simple versus complex dislocation
1. Simple—Elbow dislocation without osseous injury
2. Complex—Elbow dislocation with osseous injury
a. The terrible triad is an injury characterized by an elbow dislocation with an LUCL tear, a radial head fracture, and a coronoid fracture.
b. Varus posteromedial rotary instability is characterized by a LCL tear with a fracture of the medial facet of the coronoid or a comminuted coronoid fracture.
B. Direction of displacement
1. Posterior dislocations (most common)
a. Posterior
b. Posterolateral
c. Posteromedial (
Figure 2)
2. Anterior, medial, lateral, and divergent dislocations also occur.
V. Treatment
A. Treatment options—An algorithm for nonsurgical and surgical treatment of simple elbow dislocation is shown in
Figure 3.
[Figure 2. AP radiograph of a posteromedial dislocation of the elbow.]
1. Nonsurgical
a. Begin with reduction of the joint under adequate analgesia. Reduction maneuver for posterior dislocations: Perform a controlled reduction first by applying inline traction to correct medial and lateral displacement of the elbow. Supinate the forearm to clear the coronoid under the trochlea while flexing the elbow joint and applying pressure on the tip of the olecranon.
b. Assess postreduction stability. In posterior dislocations, the elbow is typically more unstable in extension. Therefore, the elbow should be immobilized in at least 90° of flexion.
i. If the LCL is disrupted and the MCL is intact, the elbow will be more stable with the forearm in pronation.
ii. If the LCL is intact and the MCL is disrupted, the elbow will be more stable in supination.
c. Apply a posterior splint. Typically, the forearm is placed in a splint for 5 to 7 days, with the elbow positioned at 90° and with appropriate forearm rotation.
[Figure 3. Algorithm for nonsurgical and surgical treatment of simple elbow dislocation. LCL= lateral collateral ligament; MCL= medial collateral ligament.]
d. Perform a radiographic assessment (AP and lateral views with the elbow at 90° and appropriate forearm rotation) to confirm concentric reduction and rule out associated fractures. If concentric reduction is confirmed, the arm is immobilized for 5 to 7 days. Depending on stability, the splint can be removed to allow early active range-of-motion exercises using a brace with or without an extension block.
2. Surgical
a. Indications
i. Stability of the elbow cannot be achieved with reduction and immobilization.
ii. Osteochondral fragment or soft-tissue entrapment prevents concentric reduction.
iii. Complex dislocation-associated fractures are present.
b. Contraindications—Surgery is contraindicated for patients with severe medical comorbidities.
3. Surgical procedures
a. The incision can be made in the posterior mid-line or on the lateral elbow over the Kocher interval (extensor carpi ulnaris and anconeus).
b. Open reduction and internal fixation of the coronoid can be performed through the lateral approach, although severe comminution may necessitate a medial approach.
c. Open reduction and internal fixation or replacement of the radial head is performed.
d. The LCL is repaired or reconstructed.
e. If the elbow is still unstable, the MCL is repaired or reconstructed.
f. Hinged fixation is required only if the elbow is unstable after other surgical procedures (listed above) have failed to maintain a concentric, stable reduction.
B. Complications
1. Loss of extension (most common)—Early, active range-of-motion exercises can help prevent or minimize occurrence. Static, progressive splinting may be initiated when the elbow is less inflamed (typically 6 to 8 weeks after injury).
2. Neurovascular injuries
3. Compartment syndrome
4. Articular surface injuries
5. Chronic elbow instability
6. Late contracture
7. Heterotopic ossification
C. Pearls and pitfalls
1. The most common pitfall is failure to attain and maintain a concentric reduction after surgical or nonsurgical treatment. The joint must be reduced concentrically, and treatment does not stop until satisfactory reduction is achieved.
2. Use forearm rotation to its fullest advantage to attain/maintain concentric reduction.
3. Early active range of motion through a stable arc with the use of splints can help prevent contracture.
4. If open reduction is required, follow a stepwise surgical approach.
D. Rehabilitation—Depending on the postoperative stability of the elbow, active range-of-motion exercises may begin using a brace with or without an extension block.
Top Testing Facts
1. The three primary static constraints of the elbow are the ulnohumeral bony articulation, the anterior bundle of the MCL, and the LCL complex (including the LUCL).
2. The three secondary static constraints of the elbow are the capsule, the radial head, and the common flexor and extensor tendon origins.
3. The dynamic constraints are the muscles that cross the elbow joint (the anconeus, triceps, and brachialis); these muscles apply compressive force.
4. In posterolateral dislocations, the classic mechanism of injury is thought to be a combination of axial load, external rotation of the forearm (supination), and valgus force (valgus posterolateral). A progressive circular disruption of the soft tissues occurs.
5. The joint must be reduced concentrically, and treatment does not stop until satisfactory reduction is achieved.
6. In posterior dislocations, the elbow is typically more unstable in extension. Therefore, the elbow should be immobilized in at least 90° of flexion. If the LCL is disrupted and the MCL is intact, the elbow will be more stable with the forearm in pronation. If the LCL is intact and the MCL is disrupted, the elbow will be more stable in supination.
7. Loss of extension is the most common complications following surgical treatment of elbow dislocation.
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