24 Elbow Dislocation

10.1055/b-0040-176965

24 Elbow Dislocation

Jodi Siegel

Introduction

Simple elbow dislocations involve dislocation of the ulnohumeral and radiocapitellar joints with no associated fractures. The elbow joint is typically stable after closed reduction. Older patients, patients with higher-energy mechanisms, and fracture-dislocations have a higher risk for residual instability which may require operative intervention.

I. Preoperative

History and physical exam
1. The typical mechanism is fall on an outstretched hand. Patients present with obvious deformity and pain.
2. Inspect the skin for open wounds.
3. A thorough distal neurovascular examination must be performed and documented for both sensory and motor functions. Radial and ulnar pulses should be evaluated and compared to the contralateral extremity.
4. Ipsilateral upper extremity injuries occur in up to 20% of patients with elbow fracture-dislocations and most commonly these injuries are in the wrist.
Anatomy
1. Elbow stability is conferred by the surrounding soft tissues and the bony articulations.
2. Static soft-tissue stabilizers (capsule, collateral ligaments):
  1. Joint capsule contributes to stability in full flexion and full extension.
  2. Lateral collateral ligament (LCL), which has three components (the radial collateral ligament, annular ligament, and lateral ulnar collateral ligament [LUCL]), is the primary varus and posterolateral rotational stabilizer.
  3. Medial collateral ligament (MCL) is composed of two bundles—the anterior bundle is the main valgus stabilizer; the posterior bundle is a secondary restraint to valgus forces.
3. Dynamic soft-tissue stabilizers (muscles crossing the elbow):
  1. Muscular contraction loads the elbow joint creating joint reaction forces which contribute to stability, most importantly when the static constraints are disrupted.
  2. Biceps, brachialis, and triceps provide compressive force while common extensor muscle group supplies valgus stability.
  3. As such, pronation will help to stabilize the LCL-deficient elbow.
4. The stabilizing structures of the elbow can also be divided into primary and secondary stabilizers.
5. Primary stabilizers:
  1. MCL.
  2. LCL.
  3. Coronoid: primary stabilizer to varus stress.
6. Secondary stabilizers:
  1. Capsule.
  2. Radiocapitellar articulation: the radial head is a secondary valgus stabilizer.
  3. Common extensor and flexor origins.
7. Pathoanatomy:
  1. Simple dislocation typically results in disruption of the LCL, MCL, and capsule.
  2. Muscular origins may also be disrupted.
  3. In the general population, most residual instability is due to incompetence of the LCL as most activities of daily living (ADLs) result in varus stresses across the elbow.
  4. In overhead throwing athletes who repeatedly have valgus stresses across the elbow, the MCL is the more important stabilizer and more likely to be compromised.
8. Coronoid fractures occur in up to 15% of elbow dislocations (▶ Fig. 24.1 ).
  
  Fig. 24.1 Anteroposterior radiograph showing an elbow dislocation with a large anteromedial coronoid fragment (a). Post reduction (b) and postsurgical (c) lateral images show the ulnohumeral and radiocapitellar joints reduced and the coronoid fragment stabilized. Surgical treatment was through a medial flexor carpi ulnaris splitting approach with a mini-fragment buttress plate.
  1. The size and location of the fragment and the associated soft-tissue injury dictates treatment.
  2. Coronoid plays an important role in providing varus stability and acts as an anterior and varus buttress.
  3. It also helps to resist axial and posterolateral and posteromedial rotatory forces.
  4. The sublime tubercle is on the anteromedial facet of the coronoid and serves as the insertion site of the anterior bundle of the MCL. The MCL acts as a restraint to valgus and posteromedial rotatory instability.
9. The ulnar nerve is the most commonly injured nerve with elbow dislocation.
Imaging
1. Anteroposterior, lateral, and oblique plain radiographs of the elbow are used to diagnose a dislocation and to confirm a concentric reduction.
2. Computed tomography scan and magnetic resonance imaging are rarely indicated unless there are concerns for associated fractures or nerve entrapment for which management would be altered.
3. Completion plain radiographs of the injured extremity are obtained as they are clinically necessary.
Classification
1. Simple dislocations are named according to the direction of the distal segment: posterior, posterolateral, posteromedial, medial, lateral, and anterior.
2. The most common dislocations are posterior or posterolateral.
3. Posterolateral dislocations:
  1. Occur due to a valgus, axial, and posterolateral forces.
  2. Soft-tissue injury is thought to begin on lateral side with disruption of LCL and proceed through the capsule to medial side with the MCL injured last.
4. Posteromedial dislocations:
  1. Less common; they occur due to a varus, axial, posteromedial force.
  2. The force runs medial to lateral and frequently results in small anteromedial coronoid fracture.
5. ‘Terrible triad’:
  1. Elbow dislocation.
  2. Radial head fracture.
  3. Coronoid fracture.
  4. Typically a posterolateral rotatory mechanism that shears off the anterolateral radial head and tip of the coronoid while dislocating the elbow joint.
6. Coronoid fractures—Regan and Morrey classification (▶ Fig. 24.2 ).
  
  Fig. 24.2 Regan and Morrey classification of coronoid fractures. Type I: tip of coronoid fracture; Type II: coronoid fracture less than 50% of the height; Type III: coronoid fracture greater than 50% of the height.