Upper Limb Anatomy Flashcards
Describe the structure of a synovial joint
Articular cartilage
- Avascular
- Aneural
Fibrous capsule
- May be reinforced by stabiliser muscles
- Strengthened by intrinsic ligaments
Extrinsic ligaments may be primary stabilisers
- Ligaments have rich nerve supply but poor blood supply
- Injury will cause pain but will take long time to heal
Synovial membrane lines all non-articular surfaces
- Has nerve supply and highly vascularised
- Tearing > haemarthrosis
- Increased fluid from overproduction of synovial membrane may > effusion
What are the special joint structures?
Labrum = fibrocartilaginous rim/lip > deepens socket in ball and socket joints
- May provide site of attachment for muscle which originates inside joint
- Tendon has bony attachment and labral attachment
- Therefore avulsion of head of biceps may detach labrum
Fat pad = intra-capsular but extra-synovial
- Spread synovial fluid around when they move
Ligaments = thickenings of capsule (intrinsic)/some distance from capsule (extrinsic)
Discs - present in some joints
- Meniscus = half-moon shaped disc
Bursa = sac containing synovial fluid, located wherever potential for friction
- Communicate with joint cavity - potential for spread of infection
What are the characteristic of a stable joint?
Congruent and often deep articular surfaces
Tight capsule with strong ligaments
Limited range of movement
What are the characteristics of a mobile joint?
Greater range of movement
Stability dependent on external structures and less dependent on intrinsic articular structures
Associated with increased susceptibility to sublaxation/dislocation
What are the joints of the shoulder complex?
Sternoclavicular Acromioclavicular Glenohumeral Scapulo-thoracic = pseudo-joint between scapula and fat of chest wall - Facilitates clavicular movements
When do most long bones of the skeleton commence ossification?
Shaft ossification occurs in utero at 8 weeks
Epiphyses most likely to appear after birth, but some may appear before birth
What are the common fracture sites for the humerus?
Surgical neck - common in elderly - Endangers axillary nerve Mid-shaft - Endangers radial nerve Supracondylar - Endangers median nerve and brachial artery
What is the function of the anatomical neck of the humerus?
Attachment for capsule, except its medial aspect
Describe the curves of the clavicle
Convex medial 2/3 anterior curve
Concave lateral 1/3 curve
What are the key features of the sternoclavicular joint?
Synovial saddle joint Very stable Composed of 3 articulating surfaces - Proximal end of clavicle - Clavicular notch of manubrium - 1st costal cartilage Intra-articular disc and strong capsule - Containing rich blood supply and nerve supply - Increases complexity of movement - Costoclavicular ligament = main limitation to movement
What are the movements of the sternoclavicular joint?
Elevation and depression with rotation about longitudinal axis
What structures are endangered with sternoclavicular sublaxation?
Subclavian artery and vein
What are the key features of the acromioclavicular joint?
Plane synovial joint
Articular surfaces lie in sagittal plane
Weak capsule
- Acromioclavicular ligament not very strong
Antero-posterior force tends to cause sublaxation/dislocation
Main stabiliser some distance from joint = coracoclavicular ligament
-2 parts separated by bursa
- Both parts prevent upward rotation of clavicle at acromioclavicular joint
What are the grades of acromioclavicular sublaxation?
Grade 1 = acromioclavicular ligaments stretched but not torn
Grade 2 = acromioclavicular ligaments torn and disrupted
Grade 3 = acromioclavicular and coracoclavicular ligaments ruptured with wide separation of joint
What are the five layers of the shoulder joint, from in to out?
Bones
- Large head of humerus fits into relatively shallow glenoid fossa of scapula
Labrum
- Attempt to compensate for lack of glenohumeral joint stability by deepening socket
- Has attachments for long head of biceps and glenohumeral ligaments
Capsule, reinforced by intrinsic ligaments
- Loose capsule, unstable, but allows greater range of movement
- Attaches to anatomical neck and surgical neck, creating dependent fold > allows greater movement
- Opening in capsules for
- Subcapsular bursa
- Tendon for long head of biceps
- Capsule may tighten, causing adhesive capsulitis = frozen shoulder
- Limits range of movement
Tendons = rotator cuff
- Primary stabilisers
- Tendinous insertions of muscles that reinforce joint blend into capsule
- No rotator cuff below joint
Coraco-acromial ligament/arch and sub-acromial bursa
- Subacromial ligament between 2 non-mobile bones - acromion and coracoid
- Subacromial bursa under arch and doesn’t communicate with joint
- Subacromial bursa susceptible to irritation during shoulder abduction, especially if rotator ccuff weak > can cause bursitis
How are the rotator cuff muscles organised around the shoulder joint?
Supraspinatus on top
Infraspinatus and teres minor behind
Subscapularis in front
What is the action of supraspinatus?
Aids abduction
What is the primary abductor of the shoulder joint?
Deltoid
What is the action of infraspinatus and teres minor?
External rotation
What is the action of subscapularis?
Internal rotation
What are the types of shoulder dislocation?
Anterior
Posterior
What happens in an anterior dislocation of the shoulder?
Most common due to force applied to abducted and exterally rotated arm
Humerus initially moves anteriorly and then dislocated inferiorly
Common in sporting injuries
Axillary nerve endangered by inferior dislocation
- Sensory branches of axillary nerve supply skin over shoulder region (C5)
- Pin-prick test over military badge region to ascertain if there’s been nerve damage
What happens in a posterior dislocation of the shoulder?
Less common
May occur due to electric shock/epileptic fit
What are the two joints contained in the elbow complex?
Elbow joint between humerus and ulna
- Trochlea (medial condyle) of humerus articulate with coronoid process
- Capitulum (lateral condyle) of humerus articulates with radial head
Proximal radioulnar joint
Both joints share 1 synovial cavity
Describe the ligaments of the elbow joint complex
Medial collateral ligament
Lateral collateral ligament
Both resist abduction at elbow joint
Annular ligament encircles head of radius
Describe the medial collateral ligament
Originates from medial epicondyle and inserts onto ulna
Much stronger than lateral collateral ligament
Describe the lateral collateral ligament
Originates from lateral epicondyle of humerus and fuses with annular ligament distally
What muscles attach to the lateral epicondyle of the humerus?
Superficial extensor muscles of forearm
What does the annular ligament allow?
Pronation and supination
What is found inside the fossa of the elbow joint complex?
Intracapsular fat pads
Fill fossa when not occupied by bone
When is their maximal stability in the elbow joint?
Full extension
What is valgus angulation of the forearm and why may it be significant?
Forearm points laterally about 165 degrees when in full extension = cubitus valgus
May result in friction of ulnar nerve
What movements occur across the radioulnar joints?
Supination and pronation
Interosseus membrane = axis of rotation
What are the functions of the interosseus membrane?
Produce pronation and supination
Links 2 sets of radioulnar joints
Transmits forces from radius to ulna
Where are the articular surfaces of the distal radioulnar joint?
Head of ulna
Distal radius
What are the types of fractures and dislocations of the elbow?
Falling backwards with flexed elbow may cause fracture of coronoid process of ulna and posterior dislocation
Dislocation > stretch and spasm of brachial artery and its branches > Volkmann’s ischaemia of forearm musculature
If fracture of medial epicondyle > ulnar nerve susceptible to injury
What are the carpal bones from lateral to medial, proximal to distal?
Some = scaphoid Lovers = lunate Try = triquetral Positions = pisiform That = trapezium They = trapezoid Cannot = capitate Handle = hamate
Describe the scaphoid bone
Large articular surface (proximal)
Bulbous end (distal)
Narrow portion = waist, in between articular surface and bulbous end
- Has vascular foramina > contain blood vessels directed into bone by tendons/ligaments
- Vascular foramina never found on articular surfaces
Projection of scaphoid sitting up = tubercle
Floor of anatomical snuff box
Describe the lunate bone
Directly involved in movements at wrist joint
Describe the triquetral bone
Minimally involved in movement at wrist joint
- Only when in ulnar deviation
Describe the pisiform bone
Sesamoid bone
Found in insertion of tendon of flexor carpi ulnaris
Describe the trapezium bone
Has tubercle
Describe the capitate bone
Largest carpal bone
Describe the hamate bone
Contains hook
What is the flexor retinaculum?
Deep fascia seen when wrist flexed
Tendons of wrist pass into hand under flexor retinaculum
Describe the ossification of the carpal bones
Don’t start ossification until 2 years
Usually biggest bones start ossification 1st
From capitate, ossification happens in anti-clockwise direction
Ossification of pisiform last at 11/12 years
What are the joints of the wrist complex?
Radiocarpal
Intercarpal/midcarpal
Describe the radiocarpal joint
Synovial ellipsoid joint
Involves
- Radius
- Scaphoid
- Lunate
Due to shape of joint, some movements blocked
Flexion greater than extension
- Because of bony blocks of joint
Ulnar deviation greater than radial deviation
- Radial styloid process limits radial deviation
Describe the intercarpal joints
Between proximal and distal carpal rows - excluding pisiform
Multiple articulatins
- Functional rather than anatomical joint
Movements generally opposite to wrist
- Extension more than flexion
- Radial deviation more than ulnar deviation
What is the role of the radiocarpal ligaments?
Resists tendency of carpal bones to slide into medial space between wrist and ulna
Palmar radiocarpal ligaments anchor carpal bones towards radius
Radio-scapho-lunate ligament passes over scaphoid and encircles lunate
- Provides archway across 2 proximal carpal bones, anchoring them
- Any damage to band > immobilisation of lunate bone
What is the most commonly sublaxed carpal bone?
Lunate, secondary to radio-scaphoid-lunate ligament injury
How do the flexor and extensor tendons of the forearm act to stabilise the wrist?
Tendons bypass wrist to attach to distal bones
Drag carpal bones closer to radius and ulna - act as stabilisers
Which of the carpal bones are most commonly fractured? What are the consequences of this?
Scaphoid, most commonly at waist
Significant due to blood supply from branches of radial artery through vascular foramina
If fracture not picked up/secured/stabilised, blood flow supplying distal pole becomes so disrupted that proximal pole undergoes avascular necrosis
What are the major joints of the hand?
Carpometacarpal
Metacarpophalangeal
Interphalangeal
Describe the carpometacarpal joints
All synovial joints
Joint of thumb = saddle allows opposition
Describe the metacarpophalangeal joints
Condyloid joints
Flexion/extension and abduction/adduction
Volar (palmar) and dorsal plates = fibrocartilaginous plates expanding surface area for articulation
Describe the interphalangeal joints
Flexion/extension only
Why is it easier to abduct and adduct the fingers in flexion?
Collateral ligaments taut in flexion
What are the types of interphalangeal injuries?
Palmar interphalangeal joint injury > swan neck deformity
- Volar plate may be damaged
Dorsal interphalangeal joint injury > boutonniere deformity
- Top of condyle may push through dorsal plate
Where does the pectoral girlde articulate with the axial skeleton?
Manubrioclavicular joint
Which muscles from the thoracic wall stabilise the pectoral girdle anterolaterally to the chest wall?
Pectoralis major
Pectoralis minor
Subclavius
Serratus anterior
Which muscles from the vertebral column stabilise the pectoral girdle posteriorly to the chest wall?
Trapezius Latissimus dorsi Levator scapulae Rhomboid minor Rhomboid major
What are the attachments of pectoralis major on the pectoral girlde?
Has clavicular and sternocostal head
- Attaches at clavicle
- Attaches to sternum and costal cartilages
Fibres converge >
Small insertion >
Clavicular fibres overlap sternocostal fibres >
Insert onto proximal humerus at lateral lip of intertubercular sulcus
What are the actions of pectoralis major at the shoulder joint?
Adductor Medial rotator Accessory muscle of inspiration - Fix humoral attachment - Pulls on ribs - Expands thoracic cage
Which muscles of the anterior chest wall that stabilise the pectoral girdle are underneath pectoralis major?
Subclavius
Pectoralis minor
Describe subclavius
Small
Fills space between clavicle and 1st rib
Passes laterally
What is the origin and insertion of subclavius?
Origin: anteromedial part of 1st rib
Insertion: undersurface of clavicle
What does subclavius do?
Stabilises clavicle
Describe pectoralis minor
Inferior to subclavius Origin: anterior surface of ribs 3-5 Fibres ascend and converge Insertion: coracoid process of scapula Stabilises scapula Depresses shoulder
Describe serratus anterior
Overlies lateral part of thorax Saw tooth attachment of anterolateral chest wall Origin: lateral surface of ribs 1-8 Heads posteriorly Underlaps scapula Insertion: medial border of scapula Protractor of scapula Holds scapula to chest wall
What is a winged scapula?
Scapula doesn’t glide along chest wall
Swings out like bird’s wing
Due to damage to nerve supply of serratus anterior
What is the clavipectoral fascia?
Fascia from clavicle Surrounds - Subclavius - Pectoralis minor Attaches to inferior fascia of axilla
Which muscles attach the humerus to the scapula?
Deltoid Subscapularis Supraspinatus Infraspinatus Teres minor Teres major
Which muscles make up the rotator cuff?
Subscapularis
Supraspinatus
Infraspinatus
Teres minor
From where does deltoid arise?
1 part from spine of scapula
1 part from aromion laterally
1 part from lateral third of clavicle anteriorly
What is the insertion of deltoid?
Fibres converge
Insert into deltoid tuberosity on humerus
What are the actions of deltoid?
Anterior fibres flex shoulder
Posterior fibres extend shoulder
As a whole, abducts arm
What does supraspinatus do?
Initiates abduction
Gets arm out of vertical
Deltoid fibres take over after that
Where is supraspinatus?
Above spine of scapula
Where is infraspinatus?
Below spine of scapula
Where is teres minor?
Edge to edge with infraspinatus
Arising from inferior angle of scapula
Where do supraspinatus, infraspinatus, and teres minor insert?
On greater tubercle of humerus, on 1 of 3 facets
- Superior = supraspinatus
- Middle = infraspinatus
- Inferior = teres minor
Where is subscapularis?
Deep to scapula, between it and chest wall
Origin: subscapular fossa
Insertion: lesser tubercle of humerus