http://upload.orthobullets.com/topic/6030/images/ecu.jpg
http://upload.orthobullets.com/topic/6030/images/attenuate.jpg
http://upload.orthobullets.com/topic/6030/images/rotation.jpg
http://upload.orthobullets.com/topic/6030/images/torn.jpg
http://upload.orthobullets.com/topic/6030/images/subsheath.jpg
Introduction
  • Overuse of wrist can lead to spectrum of ECU tendonitis and instability
  • Pathoanatomy
    • ECU subluxation is secondary to attenuation or rupture of the ECU subsheath (6th dorsal compartment)
    • attenuation  
      • remains intact but is stripped at ulnar/palmar attachment to produce a false pouch that the ECU tendon can subluxate/dislocate into
    • rupture  
      • ulnar sided ECU subsheath tears
        • ECU subluxates on supination, and reduces on pronation
      • radial sided ECU subsheath tears
        • ECU subluxates on supination, and lies on top of the torn subsheath on pronation
    • subluxation and snapping can lead to ECU tendonitis
  • Risks
    • tennis 
    • golf
Anatomy
  • Extensor tendon compartments  
    • Compartment 1 (De Quervain's Tenosynovitis )
      •  APL
      •  EBP 
    • Compartment 2 (Intersection syndrome )
      •  ECRL 
      •  ECRB 
    • Compartment 3
      •  EPL 
    • Compartment 4
      •  EIP 
      •  EDC 
    • Compartment 5 (Vaughn-Jackson Syndrome )
      •  EDM
    • Compartment 6 (Snapping ECU )
      •  ECU
  • ECU tendon
    • ECU subsheath is part of the TFCC that is most critical to ECU stability   
    • ECU subluxates during ulnar deviation, supination, wrist flexion  
      • this position has the greatest angulation of the ECU tendon with respect to the ulna
Presentation
  • Symptoms
    • pain and snapping over dorsal ulnar wrist
  • Physical exam
    • extension and supination of the wrist elicit a painful snap   
    • ECU tendon reduces with pronation 
Imaging
  •  Radiographs
    • unremarkable
  • Ultrasound
    • can dynamically assess ECU stability
  • MRI
    • can show tendonitis, TFCC pathology, or degenerative tears of ECU 
Treatment
  • Nonoperative
    • wrist splint or long arm cast 
      • indications
        • first line of treatment
      • technique
        • arm immobilized in pronation and slight radial deviation
  • Operative
    • ECU subsheath reconstruction +- wrist arthroscopy
      • indications
        • if nonoperative management fails
      • technique
        • direct repair in acute cases
        • chronic cases may require a extensor retinaculum flap for ECU subsheath reconstruction
        • wrist arthroscopy shows concurrent TFCC tears in 50% of cases
 

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