Supracondylar Humerus Fracture

Snapshot

• An 8-year-old boy falls from a tree and lands on his outstretched right hand. He immediately develops severe elbow pain and swelling. On exam, he is unable to flex or extend his elbow due to pain. Elbow radiograph is shown and demonstrates a dorsally displaced supracondylar humerus fracture.

Introduction

• Clinical definition
  • fracture of the distal humerus proximal to the medial and lateral condyles
• Epidemiology
  • incidence
    • most common pediatric elbow fracture
    • accounts for 41% of all serious pediatric elbow injuries
    • extension type injury most common (95-98%)
  • demographics
    • children aged 5-7 years of age
    • rare in adults
    • males and females equally likely
• Etiology
  • accidental trauma (e.g., fall from moderate height)
    • fall on outstretched hand
      • leads to a extension type injury
    • fall on posterior elbow
      • leads to a flexion type injury
• Pathoanatomy
  • normal anatomy
    • humerus articulates with the radius and ulna at the elbow joint
    • medial and lateral condyles are located at the distal portion of the humerus
      • condyles represent the medial and lateral columns of the distal expansion of the humerus
    • supracondylar humerus is the part of the humerus just proximal to the medial and lateral condyles
  • fracture mechanics
    • in an extension type injury, the olecranon process is forced against the weaker metaphyseal bone of the supracondylar humerus
      • distal fracture fragment will be angulated and/or displaced posteriorly 
    • in a flexion type injury, a direct blow to the posterior elbow forces the distal condylar bone to displace anteriorly
      • distal fracture fragment will be angulated and/or displaced anteriorly 
• Associated conditions
  • neurapraxia
    • anterior interosseous nerve (AIN) neurapraxia  
      • branch of median nerve
        • innervates flexor pollicis longus, pronator quadratus, and lateral half of flexor digitorum profundus
      • most common neurapraxia in extension type fractures
    • radial nerve neurapraxia
      • second most common neurapraxia in extension type fractures
    • ulnar nerve neurapraxia
      • most common neurapraxia in flexion type fractures
• Prognosis
  • favorable
    • non-displaced or minimally displaced fractures
  • negative
    • poor anatomic reduction
• vascular injury

Presentation

• Symptoms
  • elbow pain and limited range of motion
• Physical exam
  • inspection
    • gross deformity only in severe cases
    • swelling
    • ecchymosis
  • palpation
    • tender to palpation
  • motion
    • limited flexion and extension
    • pain with passive movement
  • neurologic exam
    • important to assess motor and sensory nerve function
      • AIN neurapraxia
        • unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (can’t make A-OK sign) 
      • radial nerve neurapraxia
        • inability to extend wrist or digits
  • vascular exam
    • important to assess for vascular insufficiency
      • cold, pale, and pulseless hand necessitates immediate reduction and pinning
• if hand is still dysvascular after reduction and pinning it may require vascular exploration

Imaging

• Radiographs 
  • indication
    • anteroposterior (AP) and lateral radiographs always indicated if fracture is suspected
  • findings
    • fracture line may or may not be present
    • anterior fat pad sign (sail sign) and posterior fat pad sign 
• joint effusion suggestive of fracture

Treatment

• Conservative
  • long arm posterior splint followed by long arm casting
    • indications
      • non-displaced fractures
      • minimally displaced fractures with no comminution and minimal swelling
• Operative
  • closed reduction and percutaneous pinning
    • indications
      • displaced fractures
      • flexion type fractures
• dysvascular hand

Differential

• Radial head subluxation (Nursemaid’s elbow) 
  • second most common pediatric elbow injury
  • arm held in flexion and pronation
  • commonly occurs due to excessive traction and not a fall
• Lateral epicondyle fracture
  • third most common pediatric elbow injury
  • second most common pediatric elbow fracture
• will be tender on lateral side with minimal tenderness on medial side

Complications

• Malunion
  • cubitus varus (gunstock deformity)
    • malalignment resulting in change from physiologic valgus elbow alignment to varus alignment
    • cosmetic deformity with minimal functional impairment
• Vascular injury
  • Volkmann ischemic contracture 
    • damage to brachial artery leads to volar compartment syndrome and muscle necrosis
    • irreversible muscle contractures in the forearm, wrist, and hand