Elbow Dislocation

Elbow dislocation is the displacement of either the radius or the ulna relative to the humerus. The most common mechanism of injury is falling on an outstretched hand. Elbow dislocation presents with joint swelling, pain, and restricted range of motion. Dislocation of the elbow can be classified into simple or complex depending on the absence or presence, respectively, of a concomitant fracture. Dislocations are diagnosed with an X-ray. Management depends on whether the dislocation is simple or complex. Simple dislocations are managed with joint immobilization and casting, while complex dislocations require open reduction and internal fixation. Elbow dislocations can be complicated by joint contractures, which are due to fibrotic changes in the joint capsule, or permanent joint instability, which are due to loose ligaments.

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Overview

Definition

Elbow dislocation is the displacement of either the radius or ulna relative to the humerus.

Anatomy

The elbow is a synovial hinge joint between the upper arm and the forearm. 

  • Articulation point between the humerus in the upper arm and the radius and ulna in the forearm
  • Consists of 3 joints, which form a functional unit enclosed within a single articular capsule:
    • Humeroulnar joint 
    • Humeroradial joint
    • Proximal radioulnar joint
  • Supported by the articular capsule as well as several ligaments:
    • Radial collateral ligament
    • Ulnar collateral ligament
    • Annular ligament of the radius
    • Interosseous membrane
  • The muscles of the elbow originate in the upper arm and insert into the forearm, producing flexion/extension of the elbow as well as supination/pronation of the forearm.

Epidemiology

  • More common in men
  • Peak incidence: 12–20 years
  • 2nd most commonly displaced joint after the shoulder

Etiology and Classification

Etiology

Trauma is the most common cause, and the direction of the force affecting the elbow joint determines the direction of the dislocation.

  • A fall on an outstretched hand (most common mechanism of injury) → elbow dislocated posteriorly
  • Medial trauma → elbow dislocated laterally
  • Lateral trauma → elbow dislocated medially
  • Posterior trauma → elbow displaced anteriorly

Classification

The classification of elbow dislocations can be anatomical or clinical.

  • The clinical classification focuses on the presence of a concomitant fracture. 
  • The anatomical classification focuses on the direction of the dislocation.

Clinical classification:

  • Simple elbow dislocation: no concomitant fracture
  • Complex elbow dislocation: concomitant fracture, commonly associated with “the terrible triad” of the elbow
    • Fracture of the coronoid process
    • Fracture of the radial head or neck
    • Posteriorly displaced elbow

Anatomical classification:

  • Posterior dislocation (most common)
  • Anterior dislocation
  • Medial dislocation
  • Lateral dislocation

Clinical Presentation

  • Restricted movement during elbow flexion and extension due to displaced bones
  • Swelling and pain of the joint with possible erythema
  • Limb length discrepancy
    • If the elbow is displaced posteriorly, the affected extremity is shorter than the contralateral one.
    • In contrast, if the elbow is displaced anteriorly, the affected extremity is longer than the contralateral one.
  • Elbow deformity with prominent olecranon process
  • Damage to the brachial artery that can present with pain, pallor, absence of pulse distal to the injury, paralysis, or paresthesia 
  • Neuropathy:
    • Which (if any) peripheral nerve is affected depends on the direction of the elbow dislocation and the presence of a concomitant fracture.
    • Nondisplaced fractures with medial elbow dislocations: associated with ulnar neuropathy with decreased sensation and strength of the 4th and 5th digits
    • Nondisplaced supracondylar fractures with anteromedial elbow dislocations: associated with median neuropathy with decreased sensation and strength of lateral 3½ digits
    • Anterolateral elbow dislocation: associated with radial neuropathy with finger drop, wrist drop, and decreased sensation on the posterior forearm and the dorsal hand

Diagnosis

  • Physical assessment: characterized by signs and symptoms of fracture/dislocation
    • Pain on palpation
    • Visible swelling or disfigurement
    • Severely restricted motion 
    • Recent history of trauma to the elbow joint
  • X-ray of the elbow joint: Anteroposterior (AP) view and lateral view are obtained to confirm the dislocation.
  • CT of the elbow joint:
    • Not always indicated when X-ray is definitive
    • Performed if a complex elbow dislocation with concomitant fracture(s) is suspected

Management

Nonsurgical management

  • Preferred for simple elbow dislocations with no concomitant fractures
  • IV analgesics 
  • Closed reduction:
    1. Elbow is first flexed at 90 degrees
    2. Elbow is then preferably pronated.
    3. Axial force is applied to the forearm, bringing the olecranon process into place.
  • Postreduction X-ray of the elbow joint to ensure successful reduction and correct anatomical placement
  • Assessment of radial and ulnar pulses to exclude vascular compromise
  • Focused exam of sensation and motor strength of the affected extremity to exclude nerve entrapment
  • Immobilization of the elbow joint with brace or splint after successful reduction

Surgical management

  • Preferred for complex elbow dislocations with concomitant fracture(s)
  • IV analgesics 
  • Open reduction internal fixation: open surgical procedure to stabilize the fractured bone segments and repair the collateral ligaments of the elbow
  • Postoperative X-ray of the elbow joint to ensure successful reduction and correct anatomical placement
  • Assessment of intact radial and ulnar pulses to exclude vascular compromise
  • Focused exam of sensation and motor strength of the distal upper extremity to exclude nerve entrapment

Clinical Relevance

Elbow dislocation can commonly be observed in the following underlying conditions:

  • Radial head subluxation: displacement of the radial head from the annular ligament. Radial head subluxation usually occurs in children when they are hung by their arms (“nursemaid’s elbow”). Excessive upward or outward traction on the radius will displace it from the annular ligament. Radial head subluxation presents with severe pain and a pronated forearm held close to the trunk. Management includes hyperpronation or supination until the radial head is returned into the annular ligament. 
  • Osteogenesis imperfecta: also known as “brittle bone disease.” Osteogenesis imperfecta is an autosomal dominant genetic condition caused by mutations in either the COL1A1 or COL1A2 gene. Osteogenesis imperfecta results in decreased production of otherwise normal type I collagen. Patients may present with bone fractures due to minimal trauma, blue sclerae due to thick choroidal connective tissue, teeth abnormalities due to lack of dentin, and hearing loss due to ossicular defects. 
  • Ehlers-Danlos syndrome: genetic condition with a variable mode of inheritance resulting in defective collagen. There are multiple types of Ehlers-Danlos syndrome (EDS). The hypermobility type is the most common. The classic type affects type V collagen while the vascular type affects type III collagen. Patients present with hypermobile joints, hyperelastic skin, bleeding tendency due to vascular wall weakness, and possible organ rupture. 
  • Marfan syndrome: autosomal dominant connective tissue disease caused by FBN1 gene mutation on chromosome 15. Marfan syndrome results in a defect in the fibrillin that is necessary for the normal function of elastin fibers. Patients present with tall stature, increased arm wingspan, decreased ratio of upper body to lower body, upward and temporal lens dislocation, aortic aneurysm, and chest abnormalities (e.g., pectus excavatum or pectus carinatum).

References

  1. Joseph Chorley, M.D. (2021). Elbow injuries in active children or skeletally immature adolescents: approach. UpToDate. Retrieved March 31, 2021, from https://www.uptodate.com/contents/elbow-injuries-in-active-children-or-skeletally-immature-adolescents-approach
  2. Brian R. Moore, M.D. & Joan Bothner, M.D. (2021). Radial head subluxation (pulled elbow): evaluation and management. UpToDate. Retrieved March 31, 2021, from https://www.uptodate.com/contents/radial-head-subluxation-pulled-elbow-evaluation-and-management
  3. Mark E. Halstead, M.D. (2019). Elbow dislocation: Background, epidemiology, functional anatomy. Medscape. https://emedicine.medscape.com/article/96758-overview

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