Posterior Forearm Flashcards
What nerves provide cutaneous innervation to the posterior forearm?
Supraclavicular nn. Axillary n. Radial n. Medial brachial cutaneous n. Medial antebrachial cutaneous n. Intercostobrachial n. Ulnar n. Proper palmar digital nn. (Median n.)
What 6 muscles are present in the superficial group of the posterior forearm?
Brachioradialis m. Extensor carpi radialis longus m. Extensor carpi radialis brevis m. Extensor digitorum longus m. Extensor digiti minimi m. Extensor carpi ulnaris m.
What 4 muscles are present in the deep group of the posterior forearm?
Supinator m.
Abductor pollicis longus m.
Extensor pollicis longus m.
Extensor indicis m.
ALL muscles of the posterior forearm are innervated by what nerve?
Radial n.
ALL muscles of the posterior forearm are innervated by the radial n. via what branches?
Deep branch or posterior interosseous nerve branch
Origin of brachioradialis m.
Supraepicondylar ridge of humerus
Insertion of brachioradialis m.
Lateral distal radius, proximal styloid process
Action of brachioradialis m.
Weak arm flexion; maximal when mid-pronated
Innervation of brachioradialis m.
Superficial branch of radial n.
Origin of extensor carpi radialis longus
Lateral supraepicondylar ridge of humerus
Insertion of extensor carpi radialis longus m.
Dorsal side of 2nd metacarpal
Action of extensor carpi radialis longus m.
Extends/abducts hand at wrist
Origin of extensor carpi radialis brevis m.
Lateral epicondyle of humerus
Insertion of extensor carpi radialis brevis m.
Dorsal base of 3rd metacarpal
Action of extensor carpi radialis brevis m.
Extends/abducts hand at wrist (same as extensor carpi radialis longus m.)
Origin of extensor carpi ulnaris m.
Lateral epicondyle; posterior ulna via shared aponeurosis
Insertion of extensor carpi ulnaris m.
Dorsal base of 5th metatarsal
Action of extensor carpi ulnaris m.
Extends and adducts hand at wrist
Origin of extensor digitorum m.
Lateral epicondyle
Insertion of extensor digitorum m.
Extensor expansion of medial 4 digits
Action of extensor digitorum m.
Extends primarily at MPJ, but also at IPJ
[also has some wrist extension function]
Origin of extensor digiti minimi m.
Lateral epicondyle
Insertion of extensor digiti minimi m.
Extensor expansion of 5th digit
Action of extensor digiti minimi m.
Extends 5th digit at MPJ but also at IPJ
Origin of supinator m.
Deep part = ulna
Superficial part = lateral condyle
Insertion of supinator m.
Radial tubercle; oblique line of radius
Action of supinator
Supinates forearm
Origin of extensor indices m.
Posterior surface of distal ulna
Insertion of extensor indices m.
Extensor expansion of 2nd digit
Action of extensor indices m.
Extends 2nd digit; assists extending hand at wrist
Origin of abductor pollicis longus m.
Posterior half of ulna, radius, and interosseous membrane
Insertion of abductor pollicis longus m.
Base of 1st metacarpal
Action of abductor pollicis longus m.
Abduct thumb and extend at carpometacarpal joint
Origin of extensor pollicis longus m.
Posterior middle-third ulna and interosseous membrane
Insertion of extensor pollicis longus m.
Dorsal base of distal phalanx of thumb
Action of extensor pollicis longus m.
Extends distal phalanx of thumb at IPJ; extends at MPJ and carpometacarpal joints
Origin of extensor pollicis brevis m.
Posterior distal radius and interosseous membrane
Insertion of extensor pollicis brevis m.
Dorsal base of proximal phalanx of thumb
Action of extensor pollicis brevis m.
Extends proximal phalanx of thumb at MPJ; extends carpometacarpal joint
What is the extensor expansion/extensor hood mechanism as it applies to the hand?
What other muscles participate in this movement?
As extensor digitorum contracts, it pulls on the extensor expansion (extensor hood), which causes IP joints to extend
The lumbricals also attach to the expansion at the “hood” and are thus also able to extend the IP joints
What provides the arterial supply to the posterior forearm and hand?
Posterior interosseous a. (branch of common interosseous a.)
Perforating (posterior) branch of anterior interosseous a.
Radial a. via deep palmar arch and dorsal carpal arch
The forearm branches of the radial n. that innervate the posterior forearm include:
The superficial branch of the radial n. which is lateral and runs beneath the ___________ m.
The deep branch of the radial n. which is posterior and becomes the ___________ ___________ n.
Brachioradialis
Posterior interosseous
The deep branch of the radial n. changes names to the posterior interosseous n. after penetrating what muscle?
Supinator m.
An injury to the radial n. at the proximal humerus due to humeral fracture or turniquet injury might result in what motion deficits?
No elbow extension
Weak supination
A radial n. injury at the mid-humeral level results in varying muscle weakness depending on location, usually this is due to a fracture in what part of the bone?
Radial groove
An injury to the radial n. at the distal humerus due to repetitive forearm rotation, tennis elbow, and/or compression might result in what motion deficits?
Wrist drop - inability to extend the hand, metacarpal phalangeal joint, and to fully extend forearm
An injury to the radial n. at the wrist such as with trauma, cast, or wristband might result in what primary symptom?
Loss of sensation to dorsal hand
[won’t lose any motor component at this level]
The radial n. can be injured if a person sustains a fracture to the humeral shaft due to its relationship to the _______ groove.
Spiral
Describe wrist-drop
Paralysis of EXTENSORS of the wrist and fingers –> the flexors take over
Wrist assumes partially flexed position while in a relaxed posture
What is the technical term for tennis elbow?
Lateral epicondylitis
Lateral epicondylitis usually arises as an overuse injury of ___________ muscles from the lateral epicondyle resulting in swelling, tenderness, and pain on wrist extension
Extensor
What are the 2 primary muscles affected by lateral epicondylitis?
Extensor carpi radialis brevis m.
Extensor digitorum m.
How is muscle and nerve testing done for the radial n.?
Resistance to extension by extensor digitorum m.
What is the ONLY nerve to extend the MCP joint?
Radial n.
What makes up the anatomical snuff box? (Floor, roof, contents, walls)
Floor = scaphoid bone
Roof = superficial radial n. branches
Contents = radial a.
Muscular walls = Extensor pollicis longus m., extensor pollicis brevis m.
What condition is characterized tenosynovitis of first compartment to thumb APL, EPB?
DeQuervain’s disease aka Washer Woman Sprain
How is the Finkelstein’s test for DeQuervain’s tenosynovitis done?
Thumb in closed fist and hand ulnar deviated
+ test = Pain along radius
Origin/insertion/action/innervation:
Brachioradialis m.
Origin: supra-epicondylar ridge of humerus
Insertion: lateral distal radius, proximal styloid process
Action: weak arm flexion; maximal when mid-pronated
Innervation: superficial branch of radial n.
Origin/insertion/innervation/action:
Extensor carpi radialis longus m.
Origin: lateral supra-epicondylar ridge of humerus
Insertion: dorsal side of 2nd metacarpal
Innervation: radial n.
Action: extends/abducts hand at wrist
Origin/insertion/innervation/action:
Extensor carpi radialis brevis m.
Origin: lateral epicondyle of humerus
Insertion: dorsal base of 3rd metacarpal
Innervation: radial n.
Action: extends/abducts hand at wrist
Origin/insertion/innervation/action:
Extensor carpi ulnaris m.
Origin: lateral epicondyle; posterior ulna via shared aponeurosis
Insertion: dorsal base of 5th metatarsal
Innervation: radial n.
Action: extends and adducts hand at wrist
Origin/insertion/innervation/action:
Extensor digitorum m.
Origin: lateral epicondyle
Insertion: extensor expansion of medial 4 digits
Innervation: radial n.
Action: extends primarily at MPJ, but also IPJ; some wrist extension
Origin/insertion/innervation/action:
Extensor digiti minimi m.
Origin: lateral epicondyle
Insertion: extensor expansion of 5th digit
Innervation: radial n.
Action: extends 5th digit at MPJ but also IPJ
Origin/insertion/innervation/action:
Supinator m.
Origin: deep part on ulna, superficial part on lateral condyle
Insertion: radial tubercle; oblique line of radius
Innervation: radial n.
Action: supinates forearm
Origin/insertion/innervation/action:
Extensor indices m.
Origin: posterior surface of distal ulna and interosseous membrane
Insertion: extensor expansion of 2nd digit
Innervation: radial n.
Action: extend 2nd digit; assists extending hand at wrist
Origin/insertion/innervation/action:
Abductor pollicis longus m.
Origin: posterior half of ulna, radius, and interosseous membrane
Insertion: base of 1st metacarpal
Innervation: radial n.
Action: abducts thumb and extends carpometacarpal joint
Origin/insertion/innervation/action:
Extensor pollicis longus m.
Origin: posterior middle-third ulna and interosseous membrane
Insertion: dorsal base of distal phalanx of thumb
Innervation: radial n.
Action: extends distal phalanx of thumb at IPJ; extends at MPJ and carpometacarpal joints
Origin/insertion/innervation/action:
Extensor pollicis brevis m.
Origin: posterior distal radius and interosseous membrane
Insertion: dorsal base of proximal phalanx of thumb
Innervation: radial n.
Action: extends proximal phalanx of thumb at MPJ; extends carpometacarpal joint
