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Lunate Dislocation

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Other Names

  • Lunate Dislocation

Background

History
Epidemiology

  • Carpal dislocations account for less than 10% of all wrist injuries
  • Less than 1 per 100,000 injuries annually (need citation)
  • 7% of all carpal injuries involve the lunate, 3% of of those are classified as lunate dislocations[1]

Introduction

Illustration of lunate dislocation[2]
Pathophysiology of a lunate dislocation[3]

General

  • Uncommon wrist injury secondary to trauma
  • The Lunate is disarticulated and displaced volarly from both the capitate and the radius.
    • Dorsal dislocation is less common
    • The remaining carpal bones are in normal anatomic position
    • 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
    • Up to 25% may be missed initially[4]

Etiology

  • Classically a fall on outstretched hand
    • Causes wrist hyperextension, ulnar deviation, and intercarpal supination.

Pathophysiology

  • 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

Associated Conditions

Anatomy of the Lunate

  • Situated in the center of the proximal row of the carpus between the scaphoid and triquetrum
  • Articulates with the distal radius
  • Stabilized by a series of ligamentous attachments, most notably the scapholunate ligament
  • Function is to provide osseous structure to the wrist, involved in movement at the wrist

Risk Factors

  • Unknown

Differential Diagnosis

Differential Diagnosis Wrist Pain


Clinical Features

History

  • Patient will describe some form of trauma
  • Often pain and swelling over palmer side of the wrist

Physical Exam: Physical Exam Wrist

  • Limited range of motion of the wrist
  • Median nerve distribution may be diminished due to volar displacement of the lunate
  • Patients may hold their fingers in flexion due to pain with extension

Evaluation

Lunate dislocation is seen on the lateral view (spilled teacup sign). The PA projection shows disruption of normal carpal alignment. Ulnar styloid fracture also noted[5]
Sagittal CT of the wrist demonstrating lunate dislocation (green arrow) and disruption of the normal radiocarpal alignment (red line)[6]

Radiographs

  • Standard Radiographs Wrist
  • PA view
    • Dislocation is often missed
    • Disruption of normally smooth line made by tracing the proximal articular surfaces of the hamate and capitate
    • Increased radiolunate space
    • Lunate overlaps the capitate and has a 'triangular' or 'piece of pie' appearance
  • Lateral Radiograph
    • Lunate seen displaced and angulated volarly
    • 'Spilled teacup' appearance
    • Lunate does not articulate with capitate or radius
  • Piece of pie sign
    • Characteristic triangular appearance of the lunate on the PA view caused by volar rotation of the lunate
  • Spilled teacup sign
    • Found on the lateral x-ray due to volar rotation of the lunate
  • Signet Ring Sign
    • Rounded appearance of the scaphoid tubercle due to rotatory subluxation from injury to the scapholunate ligament

MRI

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

CT

  • Not required to make diagnosis
  • Better at characterizing osseous structures

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

Management

Acute Management

  • Emergent Orthopedic consultation for reduction and stabilization with operative management
  • Immediate closed reduction and splinting alone may be utilized
    • 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

Nonoperative

  • Most cases requires surgical management for optimal outcomes
  • Decision to manage non-operatively should be made with surgical consultation
  • Recurrent dislocation is common in nonoperative management

Operative

  • Indications
    • Generally speaking, all cases requires surgical management
  • Technique
    • Open reduction, ligament repair, fixation, possible carpal tunnel release
    • Proximal row carpectomy
    • Wrist Arthrodesis

Rehab and Return to Play

Rehabilitation

  • Needs to be updated

Return to Play/Work

  • Patient's should not be cleared for return to play until proper surgical intervention and therapy.

Prognosis & Complications

Prognosis

  • Generally associated with poor outcomes
  • Delayed treatment associated with:
    • Reduced functionality
    • Reduced range of motion
    • Carpal instability
    • Pain
    • Carpal tunnel syndrome
  • Patients treated surgically exhibit signs of permanent damage as early as 2 months post op
    • Progressive degenerative changes of the radio-capitate, midcarpal joints[7]

Complications


See Also

Internal

External


References

  1. Kastanis G, Velivasakis G, Pantouvaki A, Spyrantis M. An Unusual Localization of Lunate in a Transcaphoid Volar Lunate Dislocation: Current Concepts. Case Rep Orthop. 2019;2019:7207856.
  2. Case courtesy of Andrew Murphy, Radiopaedia.org, rID: 150605
  3. Goodman, Avi D., et al. "Evaluation, management, and outcomes of lunate and perilunate dislocations." Orthopedics 42.1 (2019): e1-e6.
  4. Aslani H, Bazavar MR, Sadighi A, Tabrizi A, Elmi A. Trans-Scaphoid Perilunate Fracture Dislocation; A Technical Note. Bull Emerg Trauma. 2016;4:110–112.
  5. Case courtesy of Andrew Dixon, Radiopaedia.org, rID: 9906
  6. Case courtesy of Bruno Di Muzio, Radiopaedia.org, rID: 17209
  7. Inoue G, Shionoya K. Late treatment of unreduced perilunate dislocations. J Hand Surg Edinb Scotl. 1999;24(2):221-225.
Created by:
John Kiel on 18 June 2019 23:03:15
Last edited:
22 February 2024 13:22:00
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