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Duke Orthopaedics
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Wheeless' Textbook of Orthopaedics

Extensor Carpi Ulnaris


- See: Forearm Extensors :

- Anatomy:
    - origin: 2 heads from lateral epicondyle & middle 1/3 of posterior ulna;
    - insertion:
          - posterior surface of base of 5th metacarpal;
          - ECU is the only wrist extensor that lies in its own fibro-osseus tunnel;
    - action: extends and adducts the hand at the wrist;
    - synergists: ECRL, ECRB
    - nerve: deep radial - C7 > C6 > C8;

- Tunnel VI:
    - ECU passes thru groove on ulnar side of distal end of ulna & is covered by an annular ligament;
            - tenosynovitis may occur at this point;
    - synovial cyst may form in pt w/ RA as synovial sheath covering this tendon becomes irritated by constant ulnar deviation;
    - tendon inserts into midportion of 5th metacarpal & can be used as tendon transfer  both because of its length & because it is more of ulnar deviator than
              dorsiflexor & can thus be readily spared;

- Tenosynovitis: (diff dx of ulnar sided wrist pain)
    - clinical findings:
           - common in tennis players;
           - tenderness over the dorsoulnar aspect of the wrist, which is worsened with wrist supination, wrist flexion, and ulnar deviation
 
- Dislocation of ECU Tendon:
    - recurrent subluxation of ECU tendon is characterized by painful "snap" over ulnodorsal aspect of wrist, particularly on forearm rotation;
    - ECU retinaculum can rupture and the tendon can leave its sheath;
    - this condition may be confused w/ recurrent subluxation of distal radioulnar joint;
    - on supination w/ wrist-ulnar deviation, tendon displaces (leaves its sheath), often w/ audible snap, when moved in the ulnar and palmar directions;
    - on pronation, it relocates into its normal sulcus;
    - closed treatment by immobilization w/ forearm in pronation & wrist in radial deviation may be appropriate;
    - dislocation of ECU from distal radius frx: (see colles frx):
           - in normal wrist ECU tendon crosses the extensor surface of distal ulna;
           - ECU is more palpable when pt's wrist is extended & ulnarly deviated;
           - w/ Colles frx w/ assoc frx of distal end of ulnar styloid process, dorsal carpal ligament of tunnel VI may tear;
                   - as result, extensor tendon may dislocate over styloid process during pronation;
                   - in this instance there is perceptible, audible snap which may cause some attendant pain;
    - dislocation of ECU from RA:
           - in RA, tendon may displace in an ulnar direction or rupture;
           - in RA wrist the tendon lies on volar surface of ulna as distal ulna begins to subluxate on the radius;
           - thus tendon behaves as a flexor of the wrist rather than as extensor;
           - this has the effect of causing an imbalance between the radial and ulnar extensors, and the radiocarpal joint becomes pulled into radial deviation;
           - as tendon slips from its position on back of ulna so it loses its role as stabiliser of the distal ulna, permitting more dislocation;
    - entrapment of ECU following Galeazzi frx;
           - extensor tendons can also occur at sites of frxs of distal part of radius w/ distal radio-ulnar joint involvement (Galeazzi frx types);
           - x-rays show displaced frx of distal part of radius & widened distal radio-ulnar joint;
    - entrapment from ulnar styloid frx:
           - see ulnar styloid frx;
           - ulnar styloid may sustain avulsion frx & displace into distal radio-ulnar joint w/ ECU is tendon;
           - exam of distal ulna reveals vacant ECU sulcus (empty sulcus sign)
           - distal radio-ulnar joint is irreducible even after internal fixation of radial frx, & dorsal exploration delineates interposed ECU  tendon, with or w/o the avulsed ulnar styloid;



Excursion of prime wrist tendons.

Diagnosis and Anatomic Reconstruction of Extensor Carpi Ulnaris Subluxation

Extensor carpi ulnaris injuries in tennis players: a study of 28 cases

Extensor carpi ulnaris problems at the wrist--classification, surgical treatment and results.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, December 15, 2011 10:51 am