Elbow Anatomy Flashcards
Elbow joint
hinge joint
- radiocapitellar joint (humeroradial)
- ulnotrochlear joint (humeroulnar)
- proximal radioulnar joints
elbow ligaments
lateral collateral ligament (radial collateral ligament -RCL): lateral epicondyle to radius, resists varus forces (pushing elbow out), common with tennis; prevents subluxation and dislocation
medial collateral ligament (ulnar collateral ligament -UCL): medial epicondyle to ulna, resists valgus forces (pushing elbow in), common with throwing (baseball)
[anterior bundle most important bundle of UCL]
annular radial ligament: stretches across radial head, prevents anterior displacement radius; nursemaid elbow when radial head subluxed out of ligament and ov erlying rather than underlying; common when child’s hand yanked up; Tx is to reduce it
common extensor tendon and common flexor tendon runs superficial to RCL and UCL, respectively
Elbow flexion (muscles, inn.)
Biceps brachii: C5-6, upper trunk, lateral cord, musculocutaneous n.
- supinator (most powerful) and elbow flexor
- *Brachialis**: C5-6, upper trunk, lateral cord, musculocutaneous n.
- chief elbow flexor, pure elbow flexor
- implications for botox injections if wanting to maintain supination and relieve flexor spasticity
Brachioradialis; C5-6, upper trunk, posterior cord, radial n. (BELOW spiral groove)
Pronator teres: C6-7, upper and middle trunks, lateral cord, median n.
Elbow extension (muscles, inn.)
Triceps: C6-8, all 3 trunks, posterior cord, radial n. (innervated ABOVE spiral groove)
Anconeus: C6-8, all 3 trunks, posterior cord, radial n. (innervated ABOVE spiral groove)
midshaft humeral fractures may damage radial n. → wrist drop, finger drop, impaired radial n. muscles at elbow and below
- *triceps and anconeus preserved because already innervated (above spiral groove)**
- *HIGH YIELD**
Forearm supination (muscles, inn.)
Biceps brachii: C5-6, upper trunk, lateral cord, musculocutaneous n.
- supinator (most powerful) and elbow flexor
Supinator: C5-6, posterior cord, radial n., PIN-posterior interosseous n. (pure motor n. from median n.)
Forearm pronation (muscles, inn.)
Pronator teres: C6-7, upper and middle trunks, lateral cord, median n.
Pronator quadratus: C7-8-T1, middle and lower trunks, medial and lateral cords, median n., AIN-anterior interosseous n. (pure motor n. from median n.)
Common flexor tendon
medial epicondyle humerus (golfer’s elbow/medial epicondylitis)
pronator teres (PT): C6-7, upper and middle trunks, lateral cord, median n.
flexor carpi radialis (FCR): C6-7, upper and middle trunks, lateral cord, median n.
palmaris longus
flexor carpi ulnaris (FCU): C8-T1, lower trunk, medial cord, ulnar n.
flexor digitorum superficialis (FDS): C7-8, middle and lower trunks, medial and lateral cords, median n.
PIP flexion, attaches to proximal phalanx of digits 2-5
flexor digitorum profundus (FDP): C7-8-T1, middle and lower trunks, medial cord, AIN/ulnar n.
“so profound that it requires 2 nerves to innervate it (median and ulnar)
splits around FDS tendon, attaches to distal phalanx for DIP flexion digits 2-5
[FPL originates off radius, not part of common flexor tendon; like FDP to digit 1 and flexes distal phalanx of thumb; consider like “FDP 1”]
Common extensor tendon
located at lateral epicondyle of humerus (tennis elbow/lateral epicondylitis)
extensor carpi radialis longus and brevis (ECRL/ECRB)
ECRB most commonly inflamed w micro tears w tennis elbow
C6-8, all 3 trunks, posterior cord, radial n. (innervated ABOVE spiral groove)
extensor digitorum (ED/EDC): C7-8, middle and lower trunk, posterior cord, radial n., PIN
Anconeus: C6-8, all 3 trunks, posterior cord, radial n. (innervated ABOVE spiral groove)
Supinator
extensor carpi ulnaris (ECU): C7-8, middle and lower trunk, posterior cord, radial n., PIN
Humeral shaft fracture
FOOSH
radial nerve injury - spiral groove
impaired wrist drop
Dx: XR, PE
Tx: splinting usually
Distal humerus fracture
trauma
Dx: XR, PE, good neuromuscular exam
radial, median, ulnar ns. run through
Tx: if displaced - ORIF, if non displaced - splint
Olecranon fx
FOOSH
ulnar n. injury
Dx: XR, PE
Tx: splinting if non displaced, ORIF if displaced
Radial head fx
FOOSH
Dx: XR, PE
Tx: splint or ORIF
Valgus extension overload syndrome (VEO)
repetitive valgus extension forces (baseball players)
posteromedial elbow pain worse w pitching and VEO test
VEO test: flex elbow, extend it while applying valgus stress (stimulates pitching)
Dx: XR (olecranon osteophytes / loose bodies may be seen)
Tx: surgery to remove above, fix pitching mechanics to reduce valgus extension forces
Little leaguer’s elbow: repetitive valgus stress → traction apophysitis medial epicondyle growth plate → osteochondritis dessicans of capitellum
apophysis: local spot on bone where tendons attach
osteochondritis dessicans typically just happens at capitellum → lateral elbow pain
Osteochondrosis of elbow
poor blood supply to epiphysis → aseptic necrosis of capitellum epiphysis
lateral elbow pain worse w activity, improved w rest
usually in children
Dx: XR - patchy lucencies in capitellum
Tx: splinting, gradual increase activity
Elbow dislocation
FOOSH
most common dislocation in children
vs shoulder w adults
usually posterior dislocation; ulna goes posteriorly
Dx: XR, PE, neurovascular
Tx: closed reduction → splinting → gradual activity
