PT3 - The Shoulder Complex And Orientating The Hand Flashcards
What are the functions of the shoulder?
- shoulder girdle => orientation of hand to any position
- CNS may sacrifice anatomical structure of shoulder to maintain hand dexterity
- upper limb has more mobility, but at the cost of structural stability
What are the articulations of the shoulder?
- stenoclavicular
- acromioclavicular
- scapulothoracic
- glenohumeral (ball and socket)
- supra-humeral (sub-acromial)
- long head of biceps and Bicipital groove
Describe the structure of the SC joint
- shallow, saddle shaped between manubrium and first costal cartilage
- sternal articular surface larger than sternum
- convex vertically + concave in sagittal plane
- lined with fibrocartilage + fibrocartilaginous disc => divides joint into 2 synovial cavities (each lined with it’s own membrane)
- fibrous capsule surrounds articular surfaces, thicken in front + behind but thin above and below
Name the ligaments around the AC joint
From medial to lateral:
- conoid ligament = clavicle => scapula
- trapezoid ligament = clavicle => scapula
- acromioclavicular ligament = clavicle => acromion
- coracoacromial ligament = scapula => acromion
How many bones meet at the AC joint?
- 2 bones = clavicle + scapula via acromion
What are the movements available at the AC joint?
- plane synovial joint => gliding movements
What happens when you get to the end of range of AC joint moment?
- AC becomes part of complex movement = global movement of shoulder complex
How can this joint be injured?
- FOOSH
- landing direction on acromion
- disruption of ligamentus support
How can you assess for AC injury?
- graded based on the number of ligaments disrupted
- might notice a step between clavicle and acromion
- might notice laxity in ligament
- common site of osteoarthritis
- end ranges of movement causes compression and degenerative changes
What is the structure of the AC joint?
- planar synovial joint
- located between oval facet at lateral end of clavicle + facet at medial aspect of acromion
- articular surfaces lined with fibrocartilage
- wedged-shaped articular disc separates joint surfaces
- capsule is attached to articular margins + reinforced superior and inferior to AC ligaments
- coracoclavicular ligament (+conoid + trapezoid components) => major stability of joint
What is the functional anatomy of the rotator cuff?
- dynamic stability of GH joint (unlike passive stability of ligaments in AC)
- maintaining integrity of glenoid in capsule
- combines with joint capsule
- less reliant on passive structures to support the shoulder
- RCM sometimes described as dynamic ligaments
What are the muscles of the RC?
- teres minor
- infraspinatus
- supraspinatus
- subscapularis
What is the functional anatomy of the rotator cuff?
- RC does not permit assessment of individual musculotendinous unit => think of them as a whole structure
- tendons fuse into 1 structure
- supraspinatus + infraspinatus fuse at insertion (greater tubercle of humerus)
- teres minor + infraspinatus fuse proximally to musculotendonous junction
- subscapularis + supraspinatus tendons fuse => sheath around bicep tendon
- RC tendons adhere to GH joint capsule
What is the function of the RC?
- dynamic stability of huméral head in glenoid fossa
- blend with joint capsule => layers of fibres in different directions
- high muscle spindle control => act as ligaments
- support inferior glide of humeral head during abduction to maintain stable contact with glenoid (think patella in knee)
What is the function of the long head of the bicep?
- attaches to scapula
- humerus glides along bicep => facilitates downward shift of humeral head
- bicep assists RC dynamic stabilisation
- triceps similar, but not as much involvement as biceps
What is impingement syndrome?
- as arm elevates, if no control of GH => compress structures within subacromial space
What is the function of the long head of bicep?
- neither head attaches to humerus
- antagonistic action on passive humerus (allows humerus to slide along LHB tendon)
- LHB alters axis for G/H motion during abduction
What are the functions of the scapulothoracic joint?
- serratus anterior provides separation for 2 sides of scapulothoracic articulation
- inter-serratus-thoracic ‘articulation’ => outside of thorax + ribs + medial surface of serratus anterior + loose fatty tissue allowing gliding
- inter-thoracic scapular ‘articulation’ between lateral surface of serratus anterior + anterior surface of subscapularis
What muscles attach to the scapulothoracic joint?
- latissimus dorsi
- trapezius
- rhomboid minor + major
- pec minor + major
- omohyoid
- levator scapulae
- serratus anterior
What symptoms can you have at the shoulder?
- painful/weak e.g. rotator cuff related shoulder pain
- painful/stiff e.g. adhesive capsulitis & OA
- painful and unstable e.g. dislocation
What diagnosis may you have for RC related shoulder pain for: Painful + Weak
- subacromial pain (impingement) syndrome
- rotator cuff tendinopathy
- symptomatic partial or full rotator cuff tears
- tends to be pain on activity
Where might you experience RC pain?
- 45 - 120 degrees => RC are working hard to keep shoulder away from body
Where in the pain arc might you see acromioclavicular pain?
- 170-180 degrees (top of arc)
Which muscle injury in the shoulder is less common?
- deltoid
- stress + mechanical force are less robust
- if you have a deltoid injury => you’ll have a mechanical shoulder injury