3.4 Flashcards
Osteology of the elbow joint
Hinge type of synovial joint
Involves:
- humerus: trochlea and capitulum
- ulna: trochlear notch
- radius: head
Elbow joint capsule
Fibrous capsule with synovial lining
Joint capsule is weak anteriorly and posteriorly to allow flexion and extension, but is strengthened on each side by collateral ligaments
Ulnar collateral ligament
3 distinct bands:
- anterior band: cord-like, strongest
- posterior band: weakest
- oblique band: deepens socket for trochlea of humerus
Movements of the elbow
Flex/Ext
- primary flexors: biceps brachii & brachialis
- primary extensors: triceps
Sup/Pro
- supination
* radius and ulnar are parallel
* stronger action due to power of biceps brachii
* supinator muscle and biceps brachii
- pronation
* distal end of radius crosses ulna
* pronator teres & pronator quadratus
Subluxation and dislocation of radial head
In children, the radial head is small and underdeveloped. A sudden jerk on the arm can pull the radial head down through the annular ligament. This is known as nursemaid’s elbow.
Olecranon bursitis
Caused by:
- single blow to the elbow
- repeated minor elbow injuries, like leaning on elbows
- bacterial infiltration from skin lesions
Results:
- synovial lining bursa becomes inflammed
- hypersecretion of synovial fluid
- enlargement of bursa
Olecranon fracture
Causes:
- diverse: direct or indirect trauma
- olecranon is pulled proximally by triceps tendon
Fascia
Brachial fascia: snug sleeve
Continuous with the fascia of:
- deltoid m.
- pectoral m.
- infraspinatus m.
Attaches supracondylar ridges
Brachial fascia
Intermuscular septa separates into 2 compartments
Anterior (flexor) compartment
- biceps, brachialis, coracobrachialis
- brachial artery and vein
- ulnar nerve
- median nerve
- musculocutaneous nerve
* inntervates and comes from lateral cord
Posterior (extensor) compartment
- triceps
- deep brachial artery and vein
- radial nerve
* innervates and comes from posterior cord
Biceps brachii
When the elbow is fully flexed and pronated, the biceps is a powerful supinator. Because it crosses the shoulder, the muscle is an accessory flexor of the shoulder.
Corachobrachialis
The musculocutaneous n. pierces coracobrachialis as is exits the axilla.
Triceps brachii
The spiral groove separates the attachments of the lateral and medial head of the triceps.
The lateral head attaches proximal to the spiral groove, while the median head attaches distal to the spiral groove.
Thus, the radial n. travels between these two heads in the gpiral groove.
Cubital fossa
Transition from brachium to antebrachium
Contents:
- terminal part of the brachial a. as it bifurcates into radial a. and ulnar a.
- deep vv. - cephalic and median cubital
- biceps brachii tendon
- median n.
- superficial and deep branches of radial n.
Deep tendon reflxes
Ankle jerk reflex
- tap achille’s to test gastrocnemius
- tibial n. S1 & S2
Knee jerk reflex
- tap patellar tendon to test quads
- femoral n. L2-L4
Biceps reflex
- tab biceps tendon
- musculocutaneous n. C5-C6
Triceps reflex
- tap triceps
- radial n. C6-C8
Brachioradialis reflex
- tap brachioradialis tendon
- radial n. C5-C6
Musculocutaneous n.
Anterior compartment
Pierces coracobrachialis then runs in the plane between biceps and brachialis
Emerges on lateral side of elbow as lateral antebrachial cutaneous n.
Radial n.
Posterior compartment
Crosses the elbow anterior to lateral epicondyle
Splits into superficial and deep branches to continue posteriorly
Median n.
No functions in the arm
Courses along medial side of anterior compartment with brachial artery
Passes anterior to medial epicondyle to enter cubital fossa
Ulnar n.
No function in the arm
Courses along medial side of anterior compartment with brachial artery
Passes posteriorly to medial epicondyle where it’s prone to injury
Funny bone
Elbow anastomosis
Superficial upper extremity veins
Cutaneous innervation of anterior upper extremity
Medial brachial and antebrachial cutaneous nerves
- direct branches from medial cord of brachial plexus
- AKA median cutaneous nerve of arm and forearm
Lateral antebrachial cutaneous nerve
- continuation of musculocutaneous nerve
- AKA lateral cutaneous nerve of forearm
Radial nerve
- chief cutaneous nerve of posterior arm and forearm
