Upper Limb Anatomy Flashcards
(209 cards)
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