Lunate Dislocation

Other Names

• N/A

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Background

• Uncommon wrist injury secondary to trauma
• The Lunate is disarticulated and displaced volarly (dorsal dislocation less common) from both the capitate and the radius.
• The remainder of the carpal bones remain in normal anatomic position in relation to the radius
• Frequently missed on initial presentation due to subtlety of radiographs

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Pathophysiology

• Classically a fall on outstretched hand causing wrist hyperextension, ulnar deviation, and intercarpal supination.
• Sequence of events:
  • Scapholunate disruption
  • Disruption of capitolunate articulation
  • Disruption of lunotriquetral articulation and Lunotriquetral Ligament
  • Failure of dorsal radiocarpal ligament
  • Lunate rotates and dislocates, usually into the carpal tunnel
• Epidemiology
  • Carpal dislocations account for less than 10% of all wrist injuries

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Risk Factors

• Unknown

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Differential Diagnosis

• Fractures
  • Distal Radius Fracture
    • Barton's Fracture
    • Chauffer's Fracture
    • Colles' Fracture
    • Die-Punch Fracture
    • Radial Styloid Fracture
    • Smith's Fracture
  • Distal Ulna Fracture
  • Carpal Fractures
    • Scaphoid Fracture
    • Lunate Fracture
    • Triquetrum Fracture
    • Pisiform Fracture
    • Trapezium Fracture
    • Trapezoid Fracture
    • Capitate Fracture
    • Hamate Fracture
  • Essex Lopresti Fracture
• Dislocations
  • Carpometacarpal Joint Dislocation
  • Distal Radioulnar Joint Dislocation
  • Lunate Dislocation
  • Perilunate Dislocation
• Instability & Degenerative
  • Scapholunate Instability
  • Lunotriquetral Instability
  • Scaphoid Nonunion Advanced Collapse
  • Distal Radial Ulnar Joint Instability
  • Kienbocks Disease
  • Dorsal Wrist Impingement
• Tendinopathies & Ligaments
  • De Quervain's Tenosynovitis
  • Intersection Syndrome
  • TFCC Injury
  • Wrist Tendinopathies
  • Extensor Carpi Ulnaris Instability
• Neuropathies
  • Carpal Tunnel Syndrome
  • Pronator Teres Syndrome
  • Anterior Interosseus Nerve Syndrome
  • Posterior Interosseus Nerve Syndrome
  • Guyon Canal Syndrome
• Pediatric Considerations
  • Distal Radial Epiphysitis (Gymnast's Wrist)
  • Torus Fracture
• Arthropathies
  • Wrist Osteoarthritis
  • Rheumatoid Arthritis
  • Gout
• Cartilage
  • Osteochondral Defect
• Vascular
  • Hypothenar Hammer Syndrome
• Other
  • Ganglion Cyst of Wrist
  • Ulnar Impingement Syndrome
  • Infectious Tenosynovitis

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Clinical Features

• General: Physical Exam Wrist
• Often pain and swelling over dorsum of the wrist
• Limited range of motion of the wrist
• Median nerve distribution may be diminished due to volar displacement of the lunate
• May have associated radial styloid, scaphoid, capitate, or triquetral avulsions and dislocations

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Evaluation

Radiographs

• Standard Radiographs Wrist
• Piece of pie sign is the characteristic triangular appearance of the lunate on the PA view caused by volar rotation of the lunate
• Spilled teacup sign is found on the lateral x-ray due to volar rotation of the lunate

MRI

• Not required to make diagnosis, may be helpful to clarify soft tissue injuries

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Classification

Mayfield Classification

• Stage 1: scapholunate dissociation
• Stage 2: scapholunate dissociation, lunocapitate disruption
• Stage 3: scapholunate dissociation, lunocapitate disruption, lunotriquetral disruption
• Stage 4: Lunate dislocated with median nerve compression

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Management

Nonoperative

• Most cases requires surgical management for optimal outcomes

Acute Management

• Emergent Orthopedic consultation for reduction and stabilization with operative management
• Immediate closed reduction and splinting alone may be utilized though often associated with poor functional outcomes and redislocation
• Closed reduction technique
  • Finger traps, elbow at 90 degrees of flexion
  • Hand 5-10 lbs traction for 15 minutes
  • Dorsal dislocations are reduced through wrist extension, traction, and flexion of wrist
  • Apply Sugar Tong Splint

Operative

• Generally requires surgical management

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Return to Play

• Patient's should be emergently referred to Orthopedic Surgery for operative management.
• Patient's should not be cleared for return to play until proper surgical intervention and therapy.

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Complications

• Median Nerve Neuropathy
• Chronic carpal instability
• Degenerative arthritis
• Radiocarpal Arthritis

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See Also

• Internal
  • Forearm Pain (Main)
  • Wrist Pain (Main)
  • Hand and Wrist Anatomy (Main)
  • Physical Exam Wrist
• External
  • Sports Medicine Review Wrist Pain: https://www.sportsmedreview.com/by-joint/wrist/

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