Carpal bones (including ossification)
The carpal bones are the eight bones of the wrist. They form the articulation between the forearm
and the hand.
Gross anatomy:
Unlike the metacarpals the carpals do not belong to individual fingers
The corresponding bones in the foot at the tarsals
Divided in 2 rows proximal and distal
Proximal:
- Scaphoid
- Lunate
- Triquetrum
- Pisiform (actually a sesamoid bone with the flexor carpi ulnaris tendon)
Distal:
- Trapezium
- Trapezoid
- Capitate
- Hamate
Mnemonic: Some lover’s try positions that they can’t handle
Articulations: All synovial
- Radiocarpal
- Intercarpal
- Carpometacarpal
Ligaments:
- Ulnar and radial collateral ligaments
- Palmar and dorsal radiocarpal ligaments
- Palmar and dorsal carpometacarpal ligaments
- Intercarpal ligaments
Ossification:
Start at the capitate move around anti-clockwise, skip the pisiform
- Capitate 1m
- Hamate 2m
- Triquetrium 3y
- Lunate 4y
- Scaphoid 5y
- Trapezium 6y
- Trapezoid 7y
- Pisiform 8y
Arterial:
- Dorsal carpal arch, deep palmer arch, direct radial, and ulnar branches
Venous:
- Dorsal venous plexus, deep palmer venous arch, direction radial and ulnar veins
Variants:
- Carpal coalition
- Bipartate scaphoid
- Type 1 or type 2 lunate
Lunate
The lunate is a bone of the proximal row of carpal bones
Location: between the scaphoid and triquetrum in the proximal carpal row
Osteology:
- Semi-lunar in shape
- 4 articular facets (five in type 2)
Articulations:
- Radius
- Scaphoid
- Triquetrum
- Capitate
- Hamate (in type 2 lunate)
- Triangular fibrocartilage complex
Attachments:
Musculotendonous – nil
Ligaments:
- Scapholunate
- Lunotriquetral
- Radiolunotriquetral
- Radioscapholunate
- Ulnolunate
Blood supply:
- Dorsal radiocarpal arch and dorsal intercarpal arch
Venous:
- Dorsal venous plexus
Variants:
- Lunotriquetral coalition
- Os epilunatum
- Os hypolunatum
- Type 1 lunate – single distal articular facet for the capitate
- Type 2 lunate – additional distal articular facet for the hamate
Scaphoid
The scaphoid is a carpal bone
Location: Most lateral bone of the proximal carpal row
Relations:
- Lateral/dorsal: radial artery
- Medial: lunate and the carpal tunnel
- Distal: Trapezium
- Proximal: distal head of the radius
- Forms the radial portion of the carpal tunnel
Osteology:
- Largest of the proximal row of carpal bones
- Boat shaped
- Dividable into proximal and distal poles, separated by a waist which is further dividable into proximal and distal waists
- Scaphoid tubercle is a bony prominence on the ventral surface serves as an attachment for the flexor retinaculum
Articulations:
- Medial: Lunate
- Proximal: Radius
- Distal:
- Trapezium
- Trapizoid
- Medially with the capitate
Ligaments:
- Scapholunate
- Radioscapholunate
- Dorsal: Dorsal radiocarpal ligament
- Radial surface: radial collateral ligament
Blood supply:
- Direct branches from the radial artery
- Dorsal radiocarpal arch
- Supply enters the distal pole to perfuse the proximal pole (risk of osteonecrosis with waist fracture)
- Venous drainage vie the dorsal venous plexus and the radial veins
Ossification:
- 5 years old
Variants:
- Bipartite scaphoid
- Carpal coalition
- Scaphoid hypoplasia
Radius
The radius is one of the two long bones of the forearm.
Location: Lateral in the forearm, extending from the elbow to the wrist
Osteology:
Components:
- Proximal: Head, neck and tuberosity insertion of the biceps brachii tendon
- Mid: Shaft – thicker that the ulnar and becoming more thick distally
- Distal: Carpal articular facet, ulnar notch, radial styloid, Lister’s tubercle (Dorsal)
Articulations (articular surfaces are synovial):
Proximal:
- Radial head with the capitulum of the humerus
- Radial head with the radial notch of the ulnar
Distal:
- Distal radius facet with the scaphoid and lunate
- Ulnar notch with the ulnar head
Ligaments:
- Radial collateral ligaments of the elbow and wrist
- Radial annular ligament
- Interosseous membrane of the forearm
- Radial carpal ligaments (dorsal and palmar)
- Radioulnar ligaments (dorsal and palmer)
Blood supply:
- Radial artery and vein
Lymphatics:
- Supratrochlear
- Axillary
Innervation:
- Anterior and posterior interosseous nerves
Variants:
- Radio-ulnar synostosis
- Hypoplastic or absent radius
Ulna
The ulna is one of the two long bones of the forearm.
Location: medially with in the forearm
Gross anatomy:
Wider toward the proximal end
Features:
- Proximal: Olecranon, trochlear notch, coronoid process, radial notch, sublime tubercle (medial), (flexor digitorum), ulnar tuberosity (brachialis)
- Mid: Shaft
- Distal: head, styloid process, fovea, groove for extensor carpi ulnaris
Articulations: (all synovial)
- Trochlear notch with the trochlear of the humerus
- Radial head with the radial notch
- Ulnar head with the ulnar notch (radius)
- Wrist via the triangular fibrocartilage complex
Ligaments:
- Proximal: medial collateral ligament of the elbow, annular ligament
- Medial: interosseous membrane, oblique cord
- Distal: triangular fibrocartilage complex, ulnar collateral ligament of the wrist
Blood supply:
Ulnar and common interosseous artery
Lymphatics:
Supratrochlear
Axillary
- Innervation:
Anterior and posterior interosseous nerves
- Variants:
Ulnar variance (relative length difference between the radius and ulnar)
Humerus
Single long bone of the arm
- *Location:** between the shoulder and the elbow
- *Gross anatomy:**
- *Features:**
- Proximal: Rounded head covered with articular cartilage, greater and lesser tubercles, intertubercular groove
- Mid: Surgical neck inferior to the tubercles, deltoid tuberosity, spiral groove from radial nerve
- Distal: condyle of the humerus which consists of: capitulum, trochlear, medial and lateral epicondyles, radial fossa, olecranon fossa, coronoid fossa
Articulations:
- Proximal: the head of the humerus articulates with the glenoid of the scapula
- Distal: capitulum with the radial head, trochlear with the trochlear notch of the ulnar
Ligaments:
- Superior, middle, inferior and spiral glenohumeral ligaments
- Radial and ulnar collateral ligaments
Relations:
- Anterior: brachialis, bicep brachii, coracobrachialis
- Posterior: Profunda brachii, radial nerve, triceps brachii
- Lateral: deltoid
- Medial: brachial plexus, brachial artery, supratrochlear nodes
Blood supply:
- Anterior and posterior humeral circumflex arteries and veins
- Perforators from profunda brachii
Lymphatics:
- Supratrochlear and axillary nodes
Innervation:
- Radial nerve
Variants:
- Supracondylar process
- Olecranon foramen
Scapula
The scapulae are bones of the pectoral girdle.
Location: Superior/posterior thoracic wall
Function: Movement and support of the shoulder girdle and shoulder
Gross anatomy:
The scapula is a flat triangular bone with apex down.
Features:
- Inferior, lateral and superior angles
- Superior, medial and lateral borders
- Posteriorly the scapula is divided into a supraspinatus and infraspinatus fossa by the scapular spine
- Anteriorly there is the subscapular fossa
- Laterally is the glenoid fossa
- Superiorly is the acromion and coracoid process
Articulations:
- Acromion with the distal clavicular head
- glenoid with the humeral head
Ligaments:
- Transverse scapula ligament across the scapular notch (with the suprascapular nerve below and the vessels above)
- Coracoacromial
- Coracoclavicular
- Coracohumeral
- Glenohumeral superior, middle and inferior
- Acromioclavicular
Blood supply:
Anastomotic network formed by:
- Suprascapular
- Dorsal scapular
- Subscapular
Lymphatics:
- Axillary
Muscles:
- Rotator cuff + terres major
- Long head of the triceps and biceps
Variants:
- Os acrominale
Clavicle
The clavicle is the only bone connecting the pectoral girdle to the axial skeleton. It is also the only horizontal long bone.
Gross anatomy:
S-shaped
Features:
- Medial:
- Rounded medial end
- Costal tuberosity
- Groove for subclavius
- Distal:
- Conoid tubercle
- Flat distal end
- Trapezoid line
Articulations:
- Medial end with the sternum
- Distal end with the acromion
Muscles:
- Subclavius
- Pec. Major
- Sternocleidomastoid
- Deltoid
- Trapezius
- Sternohyoid
Ligaments:
- Acromioclavicular
- Coracoclavicular (conoid and trapezoid)
- Sternoclavicular
- Costoclavicular
- Interclavicular
Blood supply:
- Suprascapular artery
Variants:
- Forked clavicle
- Supraclavicular foramen
Wrist joint
The wrist joint is a complex synovial joint
Location: between the forearm and the hand
Movements: flexion, extension, ulnar deviation, radial deviation, circumduction
Gross anatomy:
Made up of the articulations between:
- The distal radius head and ulnar notch
- The ulnar and the triangular fibrocartilage complex (TFCC)
- The radius and the scaphoid, lunate and triquetrum (condyloid joint)
- The TFCC and the triquetrial bone
Special features:
Triangular fibrocartilage complex is a triangular cartilage disc between the ulnar and the triquetral bone
Ligaments:
- Ulnar collateral
- Radial collateral
- Radiocarpal ligaments (palmer and dorsal)
- Flexor and extensor retinacula
- Radioulnar ligaments dorsal and palmer
Muscles:
- Flexor:
- Flexor carpi radialis and ulnaris
- Palmaris longus
- Flexor digitorium superficialis
- Flexor digitorium profundus
- Extensors:
- Extensor carpi radialis longus and brevis
- Extensor carpi ulnaris
- Extensor digitorium
Blood supply:
- Radial and ulnar arteries
Innervation:
- Anterior and posterior interosseous nerves
Variants:
- Absent palmaris longus
- Ulnar variance
Distal radio-ulnar joint
The distal radio-ulnar joint is a pivot joint between the distal radius and ulna
- *Movement:** rotation of the distal radius
- *Gross anatomy:**
- Synovial joint between the ulnar notch on the radius and the ulna head
- The joint in stabilised by the TFCC
Muscles:
- Pronation: pronator quadratus and pronator teres
- Supination: supinator and biceps brachii
Ligaments:
- Anterior and posterior distal radioulnar ligaments
- Interosseous membrane
Blood supply:
- Anterior and posterior interosseous
Innervation:
- Anterior and posterior interosseous nerves
Variants:
- Radial ulna length variance
Glenohumeral joint
The shoulder joint also known as the gleno-humeral joint is a ball and socket synovial joint between the humerus and the glenoid.
Movements:
- Most mobile joint in the body
- Flex/extension, int. ext. rotation, ab and adduction
Articulation:
Head of the humerus with the glenoid fossa of the scapula. The glenoid labrum adds depth to the
glenoid fossa.
Capsule:
- Attached to the margin of the glenoid fossa to the anatomical neck of the humerus, the long head of the biceps travels through it.
- It is re-enforced by the rotator cuff except inferiorly where it is at its weakest
Bursa:
- Subacrominal – subdeltoid bursa
- Subscapular bursa (communicates with the joint by the foramen of Weitbrecht)
Ligaments:
- Superior, middle and inferior glenohumeral ligaments
- Coracohumeral ligaments
- Transverse humeral ligament
Muscles:
- Rotator cuff
- Triceps
- Biceps
- Deltoid
- Many more
Arterial supply:
- Anterior and posterior humeral circumflex and subscapular arteries
Innervation:
- Axially (C5-C6), suprascapular, subscapular, musculocutaneous nerves
Lymphatics:
- Axillary
Variants:
- Buford complex – cord like middle glenohumeral ligament
- Os acrominale
- Capsule attached to labrum
- Long head of biceps insertion – glenoid, glenoid and labrum, labrum only
Acromioclavicular
The acromioclavicular (AC) joint is a plane synovial joint of the pectoral girdle. **Gross anatomy:**
- Between the facets of the convex distal clavicle and flat medial acromion.
- The articular surfaces are lined with hyaline cartilage.
- A fibrocartilaginous wedge-shaped articular disc separates the two articular surfaces.
- A weak, synovium-lined joint capsule is attached to the articular margins and is reinforced superiorly by blending fibres of the trapezius muscle.
Ligaments
Static stabilisation is provided by:
- coracoclavicular ligaments
- superior and inferior acromioclavicular ligaments
Blood supply
- Suprascapular and thoracoacromial arteries
Innervation
- Axillary, suprascapular and lateral pectoral nerves
Variant anatomy
- Acromioclavicular joint configuration
- Os acromiale
Sternoclavicular joint
The sternoclavicular joint is a synovial joint between the medial clavicle, manubrium and the first
costal cartilage that joins the upper limb with the axial skeleton.
Gross anatomy
- Saddle joint between the medial clavicle and the clavicular notch of the sternum
- The articular surfaces are covered with fibrocartilage (rather than hyaline cartilage as in most other synovial joints). The joint space is divided into two separate recesses by a fibrocartilage articular disc.
Ligament
Due to the non-congruent articular facets, much of the joint stability comes from surrounding ligaments:
- anterior and posterior sternoclavicular ligament
- interclavicular ligament
- costoclavicular ligament
Relations
- Anteriorly: sternocleidomastoid muscle
- Posteriorly: sternohyoid muscle, sternothyroid muscle, brachiocephalic veins, the origin of the great vessels
Blood supply
Arterial supply: internal thoracic and suprascapular arteries
Innervation
Medial supraclavicular and subclavian nerves
Variant anatomy
- ~2.5% of the population have an inferior facet for articulation with the first rib
- perforation of the articular disc, where the joint recesses are in communication
