Longer and curvier in males.
Medial 2/3 is rounded and convex forwards, lateral 1/3 is flat and curves back to scapula.
Lies horizontal, subcutaneous, crossed by supraclavicular nerves
Nutrient foramen extends lateral in groove for subclavius in the middle 1/3 of lower surface
# is common, always between costoclavicular and coracoclavicular ligaments
- ie both of these are stronger than the clavicle itself.
Ossification: Very first bone to ossify in the fetus
- in a membrane from 2 centres, which ossify at 5th week then rapidly fuse
- secondary centre appears in sternal end during late teens and fuses rapidly.
Flat triangle, laterally thick and angled to form glenoid cavity and angled upwards as coracoid.
- lateral border is thick down to the inferior angle
- blade is thin and near-translucent
- spine extends back and laterally.
Upper border slants down laterally to root of coracoid, before which it dips = suprascapular notch.
- this lodges the suprascapular nerve and is bridged by the transverse scapular ligament
- note the suprascapular artery lies on top of the ligament
Dorsal blade has small supraspinous and large infraspinous fossae.
- spine twists a little along it, free lateral border concave-out with a notch at the back of the lateral angle, across which suprascapular vessels / nerve run to infraspinous fossa
- acromion projects forwards / curves anteriorly from the lateral end of the spine
Lateral angle is wedge-shaped to form the glenoid cavity, upper part projects upwards as the coracoid base; the cavity also ÔpeepsÕ forward around the chest wall rather than looking straight laterally.
The coracoid process rises from a broad base and hooks forward like a finger.
Ossification: ossifies in cartilage from several centres, commencing in 8th week.
- secondary centres for acromion, coracoid, glenoid, medial border and inferior angle appear at puberty, and fuse by about 20 years.
- base of the glenoid and coracoid ossify from the same centre.
Head articulates with capitulum, and broad distal end which meets cuboid and lunate.
Head: cylindrical, covered with hyaline cartilage. Best felt in pronation / supination in fossa behind lateral side of extended elbow.
- spherical hollow on top fits capitulum
- articulates medially with radial notch of ulnar; rest with annular ligament
Neck: enclosed by tapered lower margin of annular ligament, quadrate medially.
Shaft: radial tuberosity projects towards ulna. Biceps attaches to posterior lip, bursa lies against its anterior surface.
- anterior oblique line runs down anterior surface
- mirrored by posterior oblique line on extensor surface; receives supinator between them.
Interosseus membrane: bone pinches into ridge below the tuberosity; oblique cord at upper end, fibres pass down to ulnar below.
Lower end: expanded, rectangular; notch articulates with head of ulna.
- capsule & synovial membrane attach to articular margins and to fibrocartilage.
- Styloid process pyramidally projects below.
Posteriorly: a broad groove lies lateral to the tubercle of Lister.
Inferiorly: articular surface for wrist has two concave areas with hyaline cartilage, ulnar surface is square, articulates with lunate; lateral concave area is triangular, ¨ scaphoid.
CollesÕ #: distal fragment laterally and dorsally rotated with impaction.
Surgical approach: lateral approach as for elbow jt reaches the head: detach common extensors.
- detach supinator below from bone, moving it with periosteum will preserve post. Int. n.
lower down: expose b/n brachioradialis and FCR, or lateral to FCR at lowest end
- safeguard radial artery lateral to FCR and median nerve medial to it.
Ossification: ossifies in cartilage from a centre in the
mid-shaft at 8th week.
Secondary centres for head and lower end. Lower is growing end. Epiphyses fuse at 15 (upper) and 20 (lower)
Tapers in reverse way to radius.
Olecranon and coronoid above grip the trochlea.
- olecranon lodges olecranon fossa during extension of elbow.
- Its triangular posterior surface gives attachment to triceps and origin of deep fascia of forearm.
- coronoidÕs anterior lip has the sublime tubercle, ulnar n in contact with it.
Ulnar tuberosity forms on rough anterior surface.
Lateral surface: carries concave facet for radial notch, covered with hyaline cartilage, continues into trochlear surface.
Trochlear notch fits trochlea (hyaline), capsule of elbow jt attaches to its margins (and to the radial notch; thus elbow and prox radioulnar jts form one cavity).
Shaft: angled laterally.
- anterior supinator crest gives origin to supinator
- interosseous border projects laterally to meet the membrane.
Lower end: head of ulnar; covered with hyaline distally and at radial border; articulates with articular disc of wrist jt (triangular fibrocartilage attaches to base of styloid process);
Surgical approach: incise along posterior border. Elevate periosteum, and aponeurotic origins of FCU and FDP retract medially, ECU laterally.
Ossification: 8th week from cartilage. Secondary centre in head fuses at 18yrs; Two secondary centres join shaft at 16 yrs.