As with the flexors the extensors are divided into 2 layers
Superficial layer arising in whole or in part form the Common Extensor Origin or Tendon (from lateral epicondyle, lateral collateral ligament of elbow and adjacent fascia)
Includes - Extensor carpi ulnaris, extensor digiti minimi, extensor digitorum (communis), extensor carpi radialis longus and brevis (supinator)(brachioradialis)
Extensor Carpi Ulnaris
Forms medial border of forearm
O: From 2 heads
Humeral - from Common Extensor Origin (CEO)
Ulna - Posterior border of ulna (via a common aponeurosis with FCU and FDP)
Forms a long tendon which inserts into the dorsal surface of the base of the 5th metacarpal
A: Extension and ulnar deviation of the wrist
NS: Posterior interosseous nerve C7, 8 (deep branch of the radial nerve)
Extensor Digitorum (Communis)
Forms four tendons to each of the 4 fingers
Over the posterior aspect of the MCP joints forms the dorsal digital expansion
O: Common Extensor Origin (CEO)
A: Finger and wrist extensor
NS: Posterior Interosseous nerve (C7, C8)
Extensor Digitiorum
The distal attachment of the extensor digitorum is extensive with the tendon proper passing to the dorsal aspect of the intermediate phalanx
At the level of the heads of the metacarpals form the dorsal digital expansion which is an aponeurotic extension which pass medially and laterally to the provide attachments for the interossei and the lumbricals
The expansion forms 2 slips that apps to the distal phalanx
Extensor Digiti Minimi
From the Common Extensor Origin (CEO)
To the ulnar side of the extensor mechanism of the Vth digit
A: Extension of the 5th MCP and wrist joint
NS: Posterior interosseous nerve C7, 8
Extensor Carpi Radialis Longus
From lower 1/3 of the lateral supracondylar ridge and lateral intermuscular septum
To the posterior aspect of the base of the 2nd metacarpal
A: extension and radial deviation
NS: Radial nerve (C6, 7)
Extensor Carpi Radialis Brevis
From Common Extensor Origin (CEO)
To the posterior aspect of base of the 3rd metacarpal
A: Extension and radial deviation
NS: Posterior interosseous nerve C6, 7
Brachioradialis and Supinator
Often grouped with the posterior antebrachial muscles as they share a common nerve supply and attachment
Brachioradialis is a flexor of the elbow (covered with the elbow flexors)
Supinator produces supination of the forearm
Supinator
Arises from 2 heads
Humeral Head - from lateral collateral ligament and Common Extensor Origin (CEO)
Ulna Head - from supinator crest on the lateral aspect of upper ulna
Wraps around the radius before inserting into the lateral and posterior aspects of the proximal 1/3 of the shaft of radius
A: supination of radioulna joints
NS: Posterior interosseous nerve C5, 6
Deep Extensors
All arise from the posterior aspect of the radius, ulna and interosseous membrane
The majority act on the thumb (abductor pollicis longus, extensor pollicis longus and extensor pollicis brevis) and one acts on the index finger (extensor indicis)
Abductor Pollicis Longus
Arises form the posterior aspect of the upper radius, interosseous membrane and ulna
Forms a long tendon which passes under the extensor retinaculum with extensor pollicis brevis
Inserts into the radial side of the base of the 1st metacarpal
A: abduction of the CMC joint of the thumb and extension of the wrist
NS: Posterior interosseous nerve C7, 8
Extensor Pollicis Longus
From posterior surface of middle 1/3 of ulna and adjacent interosseous membrane
Tendon passes around the dorsal tubercle and under the extensor retinaculum
Inserts into the dorsal aspect of the distal of the distal phalanx of the thumb
A: extension of IP, MCP and wrist joint
NS: Posterior Interosseous nerve (C7, 8)
Extensor Pollicis Brevis
From posterior surface of lower 1/3 of radiusand adjacent interosseous membrane below APL
Tendon passes under the extensor retinaculum with APL
Inserts into the dorsal aspect of the distal of the proximal phalanx of the thumb
A: extension of MCP and wrist joint
NS: Posterior Interosseous nerve (C7, 8)
Extensor Indicis
Arises from the posterior surface of the lower 1/3 of the ulna and adjacent interosseous membrane
Inserts into the extensor mechanism of the index finger
A: Extension of the MCP joint of the index finger and the wrist
NS: Posterior interosseous nerve C7, 8
The Extensor Retinaculum
Strong fibrous band of deep fascia
Attached firmly to lower radius and ulna
Compartmentalised by intermuscular septa containing APL and EPB(most lateral compartment), ECRL and B, EPL and EI, ED, EDM, ECU
As tandons pass under the retinaculum the are covered in a synovial tendon sheath – tendons sharing a compartment usually share a common sheath
