Musculoskeletal: Anatomy - Elbow and forearm Flashcards
In what direction do the fibres of the interosseous membranes run?
Inferiorly from radius to ulna, to transmit forces to the humerus (e.g. in FOOSH)
Which is the longer of the two forearm bones?
Ulna
What palpable aspect of the forearm delineates the medial boundary between the flexor and extensor compartments?
Posterior border of ulna
With what movement of the thumb is the radial styloid process most easily palpated?
Abduction of thumb
Which is more distal: radial or ulna styloid?
Radial ~1cm more distal (also larger)
What is the clinical significant of isolated radial or ulna fractures?
Likely to be associated with dislocation of nearest joint (due to shafts being bound together by interosseous membrane)
What is a Colles fracture?
Complete transverse fracture of distal 2cm of the radius
Often there is an avulsion fracture of the ulnar styloid
What is the most common fracture of the forearm?
Colles fracture
Describe dinner-fork deformity
Seen in Colles fracture
Posterior angulation just proximal to wrist and normal anterior curvature of hand
Due to dorsal displacement of distal fragment of radius
What is the common flexor attachment of the muscles of the forearm?
Medial epicondyle and supra-epicondylar ridge
What is the common extensor attachment of the muscles of the forearm?
Lateral epicondyle and supra-epicondylar ridge
What are the subcut borders of the anterior and posterior compartments of the forearm?
Medial: subcut border of ulna palpable posteriorly in proximal forearm and medially in distal forearm
Lateral: radial artery palpable in anterior forearm distally and laterally in proximal forearm
Describe the functional division of anterior and posterior compartments of the forearm
Anterior: flexor-pronator muscles, supplied by median n. except for 1.5 exceptions supplied by ulnar n.
Posterior: extensor-supinator muscles, supplied by radial n. (directly or via deep branch)
What does the anterior compartment of the forearm communicate with?
Central compartment of the palm via the carpal tunnel
How many muscles cross the elbow joint? What is the breakdown by part/compartment?
17
2x arm flexors (biceps brachii, brachialis)
2x arm extensors (triceps brachii, anconeus)
5x superficial and intermediate muscles of anterior compartment of forearm (pronator teres, FCR, palmaris longus, FCU, FDS)
6x superficial muscles of posterior compartment of forearm
1x deep muscle of posterior compartment of forearm
What is the difference in bulk and strength between flexor and extensor muscles of forearm?
Flexors twice the bulk and strength of extensors
Which muscles are in what layers of the anterior compartment of the forearm?
Superficial (from lateral to medial attachment/course): pronator teres, FCR, palmaris longus (present in 17% of population), FCU
Intermediate: FDS
Deep: pronator quadratus, FDP, FPL
How many muscles are in each layer of the anterior compartment of the forearm?
Superficial: 4
Intermediate: 1
Deep: 3
Which muscles attach via the common flexor tendon?
Muscles of the superficial layer of the anterior compartment: pronator teres, FCU, FCR, palmaris longus
Which muscles of the superficial layer of the anterior compartment of the forearm have both ulnar and humeral heads?
Pronator teres
FCU
What is the proximal and distal attachment, innervation, and main action of pronator teres?
Proximal: humeral head to common flexor attachment, ulnar head to coronoid process
Distal: lateral aspect mid-radial shaft
Innervation: median n. (C6-7)
Action: forearm pronation, elbow flexion
What is the proximal and distal attachment, innervation, and main action of FCR?
Proximal: common flexor attachment
Distal: base of 2nd metacarpal
Innervation: median n. (C6-7)
Action: wrist flexion and abduction
What is the proximal and distal attachment, innervation, and main action of FCU?
Proximal: humeral head to common flexor attachment, ulnar head to olecranon and posterior ulna (via aponeurosis)
Distal: pisiform, hook of hamate, 5th metacarpal
Innervation: ulnar n. (C8)
Action: wrist flexion and adduction
What is the proximal and distal attachment, innervation, and main action of palmaris longus?
Proximal: common flexor attachment
Distal: distal half flexor retinaculum and apex of palmar aponeurosis
Innervation: median n. (C7-8)
Action: wrist flexion, tenses palmar aponeurosis
What is the proximal and distal attachment, innervation, and main action of FDS?
Proximal: humero-ulnar head to common flexor attachment and coronoid process, radial head to superior half of anterior radial border
Distal: shafts of middle phalanges of fingers (not thumb)
Innervation: median n. (C7-T1)
Action: flexion at PIPJ and MCPJ of fingers (not thumb)
What is the proximal and distal attachment, innervation, and main action of FDP?
Proximal: proximal 3/4 of anteromedial ulna and interosseous membrane
Distal: medial part to base of distal phalanges of digits 4-5, lateral part to base of distal phalanges of digits 2-3
Innervation: medial part by ulnar n. (C8-T1), lateral part by anterior interosseous n. from median n. (C8-T1)
Actions: flexion at DIPJ
What is the proximal and distal attachment, innervation, and main action of FPL?
Proximal: anterior radius and adjacent interosseous membrane
Distal: base of distal phalanx of thumb
Innervation: anterior interosseous n. from median n. (C8-T1)
Action: flexion of phalanges of thumb
What is the proximal and distal attachment, innervation, and main action of pronator quadratus?
Proximal: distal 1/4 anterior ulna
Distal: distal 1/4 anterior radius
Innervation: anterior interosseous n. from median n. (C8-T1)
Action: forearm pronation, deep fibres bind radius and ulna together