Posterior forearm and dorsum of the hand Flashcards
What muscle is highlighted and what is its innervation?
Anconeus
Radial nerve
What are the attachments of anconeus?
Lateral epicondyle of the humerus to the olecranon of ulna
What is the role of anconeus?
Extension of elbow
What is this muscle and its innervation?
Brachioradialis
Radial nerve
What is the action of brachioradialis?
Flexion of elbow - especially when elbow is in the semi-prone position
What are the attachments of brachioradialis?
Distal humerus (supra-condylar ridge) to the radius proximal to the styloid process
What nerve innervates the muscles of the posterior compartment of the forearm?
Radial nerve
What is the common extensor origin?
Lateral epicondyle of the humerus
What are the actions of extensor carpi radialis longus and brevis?
Wrist extension
Abduction
What muscle is shown and what is its innervation?
Extensor carpi radialis longus Radial nerve (C6,7)
What are the attachments of extensor carpi radialis longus?
Distal humerus (supra-epicondylar ridge) to the base of the second metacarpal
What is this muscle and its innervation?
Extensor carpi radialis brevis
Posterior interosseous branch of radial nerve (C7,8)
What are the attachments of extensor carpi radialis brevis?
Lateral epicondyle of humerus to the base of the 3rd metacarpal
What is this muscle and its innervation?
Extensor carpi ulnaris
Posterior interosseous branch of radial nerve (C7,8)
What are the attachments of extensor carpi ulnaris?
Lateral epicondyle of humerus to the base of the 5th metacarpal
What are the actions of extensor carpi ulnaris?
Extension of the wrist
Adduction
What muscle is shown and what is its innervation?
Extensor digitorum
Posterior interosseous branch of radial nerve (C7,8)
What are the attachments of extensor digitorum?
Lateral epicondyle of humerus to the dorsal expansion of digits 2-5
What are the actions of extensor digitorum?
Extension of MCPs, PIPs and DIPs on digits 2-5
Extension of wrist
What is this muscle and its innervation?
Extensor digiti minimi
Posterior interosseous branch of radial nerve (C7,8)
What are the actions of extensor digiti minimi?
MCP, PIP and DIP extension of little finger
Extension of wrist
Why does the little finger have an extra extensor?
To support the medial side of the hand against a surface when performing precision movements with the thumb and index finger e.g. stabilising the hand when writing
What are the attachments of extensor digiti minimi?
Lateral epicondyle of humerus to dorsal expansion of 5th digit
What is this muscle and its innervation?
Extensor indicis
Posterior interosseous branch of radial nerve (C7,8)
What are the actions of extensor indicis?
MCP, PIP and DIP extension of index finger
Wrist extension
What are the attachments of extensor indicis?
Posterior surface of ulna (and interosseous membrane) to the dorsal expansion of digit 2
What is this muscle and its innervation?
Extensor pollicis longus
Posterior interosseous branch of radial (C7,8)
What are the actions of extensor pollicis longus?
Carpometacarpal (CMC), MCP and IP extension at thumb
Wrist extension
What are the attachments of extensor pollicis longus?
Ulna and interosseous membrane to the base of the distal phalanx of the thumb
What muscles contribute to the borders of the anatomical snuffbox?
Extensor pollicus longus and brevis
What is this muscle and its innervation?
Extensor pollicis brevis
Posterior interosseous branch of radial nerve (C7,8)
What are the attachments of extensor pollicis brevis?
Radius and interosseous membrane to the proximal phalanx of thumb
What are the actions of extensor pollicis brevis?
CMC and MCP thumb joint extension
Wrist extension
What is this muscle and its innervation?
Abductor pollicis longus
Posterior interosseous branch of radial nerve (C7,8)
What are the attachments of abductor pollicis longus?
Radius, interosseous membrane and ulna, to the base of the 1st metacarpal
What are the actions of abductor pollicis longus?
Abduction of thumb and extension at CMC joint
Extension of wrist
What is the deepest muscle of the posterior forearm?
Suppinator
What is this muscle and its innervation?
Suppinator
Posterior interosseous branch of radial nerve (C7,8)
If the musculocutaneous nerve is damaged, will supination still occur?
Yes, suppinator is supplied by radial so will manage weak supination
What are the actions of supinator?
Supination of the forearm - rotates the radius
What are the attachments of radius?
Crest of ulna, lateral epicondyle of humerus, radial collateral lig and annular lig to the lateral radius (proximal third)
Describe the relation of the radial nerve to the suppinator
The radial nerve passes through the lamina of suppinator
The deep branch emerges from the suppinator to form the posterior interosseous nerve that runs with the posterior interosseous artery
Describe the route of the radial artery?
Terminal branch of the brachial, formed in the cubital fossa
Supplies structures in the forearm, then runs along the floor of the anatomical snuffbox
Passes between heads of adductor pollicis to enter hand
Forms most of deep palmar arch and anastomoses with ulnar artery
What part of the hand does the superficial radial nerve supply?
Sensory innervation to the lateral side of the dorsum of the hand
What structures are found on the dorsum of the hand?
- Layer of skin and subcut fat
- Dorsal venous arch
- Cutaneous nerves
- Long extensor tendons that cross the dorsum to reach the digits
What name is given to this area?
Anatomical snuffbox
What structures form the borders of the anatomical snuffbox?
Roof- Branches of the superficial radial nerve and cephalic vein
Floor- Scaphoid, trapezium and 1st metacarpal
Medial- Tendon of extensor pollicis longus and abductor pollicis longus
Lateral- tendon of extensor pollicis brevis
Why is the anatomical snuffbox an area of interest?
Radial artery runs across the bones of the floor and so can be palpates as a pulse point for radial artery
What makes up the dorsal venous arch?
Communcation between cephalic vein (lateral side) and basilic vein (medial side)
From lateral to medial, in what order do the tendons cross the dorsum of the wrist?
- Abductor PL and Extensor PB
- Extensor carpi radialis longus and brevis
- Extensor PL
- Extensor indicis and extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
What are the extensor and flexor retinacula?
Fascia that holds down tendons
What are the dorsal expansions?
Digital expansion of strong connective tissue that allows the long flexors and short muscles of the hand to work on all three finger joints
