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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.