Shoulder Flashcards
Joints of the shoulder complex
- GH
- AC
- SC
- Scapulo-thoracic
Weight transmission through UE
1) through humerus
2) through GH
3) through AC to strong SC
Ligaments of the SC joint
- Anterior (covers whole front)
- Interclavicular (covers top)
- Costoclavicular (underneath, connects to first rib)
Degrees of freedom in the shoulder
3 rotation degrees of freedome
Scap mvmt at 90 ABD
30 (60 arm) 2:1
Scap mvmt at 180 ABD
65 (115 arm) ~3:1
Prime movers of the scap when arm is elevated
Trapezius and SA
Nerve for traps
Accessory CN11
Nerve for SA
LTN
Ligaments of the GH jount
- Coracohumeral (bicep long head goes through)
- Superior/middle/inferior GH ligs
Only GH lig with a posterior side
Inferior GH lig
Bicep long head runs through this GH lig
Coracohumeral lig
Function of superior GHL
- Limits anterior and inferior translation
- Bridges gap between supraspinatus and subscap tendons
Function of middle GHL
Limits anterior translation in abduction
GH lig absent in ~30% of peeps
Middle GHL
Function of inferior GHL
- Has 2-3 bands (including axillary pouch
- Limits antero/postero-inferior
- Espescially in abduction
Labrum extends fossa depth by ____%
50%
GH fossa points _____ regularly, to provide _____ stability
Upwards, inferior
Where the GH is more taut/lax
Taut: superiorly, or inferiorly at full ROM
Lax: inferior
Where most of the dynamic GH stabilizers are
Posteriorly (all except subscap, kinda supraspinatus)
Function of the cuff during arm elevation
- Pull head of humerus towards glenoid fossa
- Provide inferior translation - limiting superior translation (shear)
Most vulnerable RC muscle
- Supraspinatus
- Tearing or calcification that can lead to impingement
Inflammation of shoulder can impact
- Capsule/ligs
- Tendons
- Bursa
Bicep tendonitis
Most commonly the long head. Repetitive attraction in friction triggers inflammation leading to swelling, further mechanical irritation
Complications of biceps tendonitis
- Sheath thickens, causing fibrosis, scarring, & adhesions
- Compromises mobility of the muscle
Usually associated with primary shoulder pathologies
- Impingement in subacromial space
- RC tears
- Coracoacromial ligament thickening
Mechanism of bursitis
Overuse of RC muscles
Most common shoulder bursa to get irritated
Subacromial
Complications of subacromial bursitis
Impingement
Mechanism of frozen shoulder
- Inflammation (more cytokines and inflammatory cells)
- Leads to capsular fibrosis, where more collagen is deposited and normal collagenous remodelling is lost
How to identify adhesive capsulitis
Articular surface loses smoothness, becomes red
(mechanical) Consequence of shoulder impingement
- Shoulder instability, excessive translation of the humeral head
- Deltoid fire more
Most common shoulder impingement
Supraspinatus + subacromial bursa
Incidence of impingement
1/3 in lifetime
Compensation with shoulder impingement
- More superior translation of humeral head
- Decreased rotator cuff activation/coactivation
- More upper traps and deltoid activity
Mechanism of anterior shoulder dislocation
Force + Abduction, extension, external rotation
% of dislocations that are anterior
95-97%
Complications of anterior shoulder dislocation
Hill-Sachs Lesion
- osteochondral indentation on humeral head due to pressing up on glenoid ridge
Bankart lesion
- Tear in glenod
- Can be fibrous or bony
% of posterior shoulder dislocations
2-5%
Mechanism of post. shoulder dislocation
Force with adduction, flexion, and internal rotation
Complications of post. shoulder dislocation
- RC and lig tears
- Reverse bankart & hill sachs lesions
% of sup./inf. shoulder dislocations
0.5%
Mechanism for superior dislocation
Extreme superior force on adducted shoulder
Mechanism for inferior dislocation
- Forceful hyperabduction of the shoulder
- Direct axial loading on abducted shoulder
Mechanism for AC joint dislocation
- Lateral blow to arm in adduction
- Usually in sports, MVA, or falling on side of body
Mechanism for clavicular #
- Common in children
- Direct impact
- FOOSH
Should also be examined in clavicular #
- Neurovasculature
- Lungs
Locations of clavicular #
- Medial 1/3 5%
- Middle 1/3 80%
- Lateral 1/3 15%
Neurogenic TOS
- 85-95%
- Pain, numbness, weakness, paraesthesia
Arterial TOS
Cold pale fingers, numbess, tingling, weakness
Venous TOS
Fatigue, UL heaviness, swelling, bluish tone to skin of UL
Areas of entrapment (TOS)
- Interscalene triangle
- Costoclavicular space
- Pectoral triangle
Interscalene triangle
- Ant + mid scalene, superior border of 1st ribe
- Subclavian vein runs anterior, not trapped
- Only brachial plexus and subclavian artery
- Can also be due to cervical rib
Costoclavicular space
- Medial 1/2 of clavicle, first rib, scapula
- Most likely structure to be compressed is the subclavian vein
Pectoral triangle
- Coracoid process, ribs, pec min
- Commonly neurovascular structures compressed here
- Any inflammation/hypertrophy/posture of pec min can cause this.
- Aggravated with arm elevated
Sensory innervation of radial nerve
Poserolateral arm and forearm, post thumb, 2nd, and 1/2 of 3rd figit
Radial nerve entrapment
- Motor (pierces supinator, deep)
- Sensory (superficial, sometimes pierces ECRB
MSC nerve entrapment
Pierces coracobrachialis
Sensory distribution of MSK nerve
Anterolateral forearm
Ulnar nerve entrapment
- Cubital tunnel
- Between FDP and FDS
- Guyon’s canal
Sensory distribution of ulnar nerve
- Anterior medial wrist and 5th digit + 1/2 of 4th
- Posterior wrist, digits 5,4, 1/2 of 3 (no tips)
Median nerve entrapment
- Carpal tunnel
- Pronator teres (rare, between ulnar and radial heads of PrT)
Median nerve sensory distribution
Anterior hand (minus 5th, 1/2 4th, post. tips of 1,2,3
Axillary nerve entrapment
- Quadrangular space, or pst # of humerus
