Anatomy of the Dorsal aspect of the Wrist

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

In the dorsal aspect of wrist , tendons are arranged in 6 compartments.

It starts with Abductor Pollicis Longus ,Extensor Pollicis Brevis ,Extensor Carpi Radialis Longus ,Extensor Carpi Radialis Brevis ,Extensor Pollics Longus, Extensor Indicis , Extensor Digitorum ,Extensor Digiti Minimi, and Extensor Carpi Ulnaris . On the top of this tendons is the Extensor rectinaculam.

FIRST COMPARTMENT : Includes abductor pollicis longus ,extensor pollicis brevis. At this compartment an abnormal pathology that could occur is De Quervain’s syndrome. Abductor pollicis longus may have multiple slips and extensor pollicis brevis may have its own separate compartment.

SECOND COMPARTMENT:Includes extensor carpi radialis longus,extensor carpi radialis brevis. This compartment is involved in Intersection syndrome. Extensor carpi radialis longus and extensor carpi radialis brevis are radial to lister’s tubercle.

THIRD COMPARTMENT : Includes extensor pollics longus which is ulnar to lister’s tubercle. EPL tendon can rupture due to nondisplaced distal radial fracture.Test for EPL rupture is by placing the palm flat on the table and lifting the thumb.

FOURTH COMPARTMENT : Includes extensor indicis and extensor digitorum. Extensor indicis is ulnar to the extensor digitorum communis for the index finger. Extensor indices is used as a tendon graft for rupture of the extensor pollicis longus. This won’t affect the function of index finger if the tendon is taken proximal to sagittal band.This compartment has the terminal branch of posterior interosseous nerve (PIN),which supplies sensation to the wrist joint.

FIFTH COMPARTMENT : Includes extensor digiti minimi which is ulnar to the small extensor digitorum communis (the extra muscle is always ulnar).

SIXTH COMPARTMENT : Includes extensor carpi ulnaris.

The extensor pollicis brevis,abductor pollicis longus and extensor pollicis longus form the anatomical “ snuff box”.

ANATOMICAL SNUFF BOX PAIN : Radial side wrist pain after trauma if associated with tenderness in the anatomical snuff box could indicate a scaphoid fracture .Patient should have immobilization of the wrist and the patient should be treated as if a scaphoid fracture is present. Repeat X rays and examination of the patient in 10 days.

PATHOLOGY ASSOCIATED WIYH THE EXTENSOR TENDONS

De Quervain’s Syndrome : Inflammation of the sheath that surrounds the two tendon that control movement of the thumb.presents with pain and swelling over the thumb side of the wrist and difficulty in gripping.

Intersection Syndrome : Pain is felt on top of the forearm where the two muscles that connect to the thumb (APL and EPB) cross over the underlying wrist tendons (ECRL and ECRB).

Extensor Tenosynovitis : Irritation of the tendons located in the fourth extensor compartment.

Snapping ECU Syndrome : Painful “snap” over ulnodorsal aspect of wrist with rupture of the ECU subsheath in the 6 th dorsal compartment.

Vaughan – Jackson Syndrome : Inability to extend the MP joints of the ring and small fingers due to extensor tendon rupture beginning on the ulnar side of the hand and wrist. Usually occurs in rheumatoid arthritis.