Only contains triceps,
radial nerve and profunda.
3 heads: long, lateral & medial; medial head would be better called deep and long head medial.
(1) Long head from infraglenoid tubercle on axillary border of scapula.
(2) lateral head from back of humerus; above groove for radial nerve
- long & lateral heads converge into superficial lamina of tendon inserting into olecranon.
(3) Medial head deep; arises below radial groove & both intermuscular septa ¨ forms a deep lamina
- blends with other lamina & inserts into olecranon
- few fibres support posterior part of elbow jt capsule
Radial nerve & profunda brachii pass between lateral & medial heads
Nerve supply: by 4 branches of radial nerve (C7,C8), 2 to medial head.
- branches arise before nerve contacts radial groove; # mid-shaft of humerus unlikely to paralyse triceps given high origin of branches.
Action: extensor of elbow; long head supports shoulder jt, aids shoulder extension.
Leaves axilla, passes over posterior humerus across groove b/n long & medial heads of triceps with the profunda brachii.
Then pierces lateral intermuscular septum (above origin of brachioradialis) to enter anterior compartment; runs toward brachialis medially and brachioradialis (later ECR) laterally.
1) branches to triceps as above; branch to lateral head supplies anconeus as well.
2) posterior cutaneous nerve of arm comes off in axilla (see 446)
3) inferior lateral cutaneous nerve of arm
4) posterior cutaneous nerve of forearm (both of these perforate lateral head ¨ superficial)
5) branches to brachioradialis, ECRL, lateral brachialis (in anterior compartment)
6) terminal superficial branch (divides at level of lateral epicondyle)
7) posterior interosseus nerve (other terminal division)
8) supplies elbow joint.
Surface marking: from where posterior wall of axilla and arm meet ¨ point 2/3 along a line from acromion to lateral epicondyle.
Only enters posterior compartment at lowest extent, then disappears into forearm
- passes through gap b/n humeral and ulnar heads of FCU.
- In contact with bone posteriorly, then against medial lig of elbow (supplies it)
Synovial hinge; communicates with proximal radioulnar jt below.
Inferior humerus has trochlea (¨ulnar) and capitalum (¨ radius)
- Capitalum projects forwards and down, and is not visible on the posterior aspect of humerus
- Trochlea (medial) is grooved around to posterior surface where trochlea notch of ulnar meets
- Anterior fossae above c & t receive head of radius and coronoid process of ulna in full flexion
A sharp long ridge projects down as the medial trochlea border ¨ carrying angle
Upper head of radius is spherically concave to fit the capitulum
Trochlea notch of ulnar is a deep groove attaches oblique to humerus shaft as part of carrying angle.
Attaches: media and lateral margins of capitulum & trochlea; anteriorly above fossae, posteriorly above olecranon fossa.
Distally: margins of trochlear notch of ulnar, and to annular ligament (not actually attached to radius)
Synovial membrane lines capsule and lower annular ligament across articular margins of all 3 bones
Quadrate ligament attaches to lower margin of radial notch of ulna and neck of radius.
Ulnar collateral (medial): triangular; 3 bands:
i) anterior band (strongest) from medial humeral epicondyle to tubercle on medial coronoid.
ii) posterior band joins sublime tubercle (medial coronoid) and medial border of olecranon
iii) middle band joins these (olecranon to medial epicondyle) grooved surface lodges ulnar n.
Radial collateral (lateral): triangular also:
- apex attaches to lateral epicondyle, base fuses with annular ligament
- anterior and posterior ligaments are merely capsular thickenings.
Annular ligament: attaches to anterior and posterior margins of radial notch of ulnar, clasping radial head in the proximal radioulnar joint. Radius remains free to rotate inside it.
Musculocutaneous, median, ulnar, radial (all of them).
Simple flexion/extension hinge.
- 140o flexion in oblique axis to humerus, ie carrying angle, bigger in women than men
- in pronation there is no carrying angle (the usual working position of the arm)
- pathologically large carrying angle may stretch the ulnar nerve causing palsy
In extension tip of olecranon is in line with epicondyles; in flexion they make and = triangle.
Medially: displace ulnar nerve backwards, detach common flexor origin to expose capsule
Lateral detach common extensor origin.
- do not extend lateral incision lower than radial head to avoid damaging posterior interosseus nerve winding around the shaft in supinator
Aspiration: insert into posterolateral side above head of radius, with elbow at R angle
- avoid medial side because of ulnar nerve.