Lecture 18: shoulder Flashcards
What is shoulder joint
Glenoid fossa with head of proximal humerus in it
Describe proximal humerus lesser tubercle
Medial aspect rounded head
Describe proximal humerus Inter tubercular groove
Attachment of muscle
Describe proximal humerus Anatomical neck
Site of proximal growth plate of humerus - fused in adults
Remnants of where growth plate was where humerus develops
Describe proximal humerus Surgical neck
Constriction distal to tubercles
Describe proximal humerus Clinical correlate
Surgical neck - narrowing = weak spot, prone to fracture, especially in elderly or osteoporotic pppl
Describe proximal humerus Greater tubercle
Larger
More lateral
Describe proximal humerus Deltoid tubersoity
Rough, where deltoid muscle attaches
what type of joint is glenohumeral
Ball and socket
Multi axial
In both directions in 3 planes, and combos of these
Describe joint glenohumeral
Big ball =humeral head
But small, shallow socket = glenoid fossa, 3-4x smaller
= has functional consequences
What motions at glenohumeral joint
Flexion extension = sagittal plane
Abduction adduction = coronal plane
Lateral rotation medial rotation = transverse plane (around longitudinal axis, bend elbow, flexion so then not using pronation/supination)
Describe stability of shoulder
Multi axial large rom + shallow ill fitting ball and socket = INSTABILITY (more prone to dislocations and injuries)
So… glenohumeral joint reinforced by passive and active stabilization structures
What passively stabilizes shoulder
Glenoid labrum
Ligaments
Describe glenoid labrum
Lip - rim of fibrocartilage arounf edge of glenoid fossa and increases contact area = provides stability
Describe ligaments that passively stabilize shoulder
Coracohumeral lig = sup aspect, joint to humeral head
Glenohumeral ligaments 3x
on back synovial capsule = no ligaments!!
Describe shoulder dislocations - clinical correlate
Since posterior aspect joint capsule not reinforced by ligaments = posterior joint surfaces separate more easily —> 95% of shoulder dislocations are ANTERIOR with humeral head in subacromial position (ant and inf)
So head moves out towards easier
What actively stabilizes shoulder
Rotator cuff muscles = 4 Muscles that attaches to scapula and run to tubercles of proximal humerus, all wrap arounf shoulder joint capsule - pull joint closer together when contract
Provides shoulder mobility and active stability (by pulling humeral head against genloid fossa)
Name the rotator cuff muscles
SItS muscles =
Supraspinatus, infraspinatus, Teres minor, subscapularis
Describe what is between Teres minor and subscapularis
Recess of synovial membrane = extra fold so can have extra rom of shoulder
Present in joint, like fibrous capsule area
Supraspinatus attachments
Suprapsinous fossa to superior facet greater tubercle
Supraspinatus Function
Abduction = especially early, first 30 degrees of abduction
Supraspinatus Innervation
Supra scapular nerve c5-c6
Supraspinatus = describe where it runs specifically
Runs over top of glenohumeral joint in narrow subacromial space, inf to acromion and coracohumeral ligament, space also contains a subacromial bursa
Stuck between humeral head and roof, between tendon and muscle of Supraspinatus roof
Supraspinatus Clinical correlate
Narrow subacromial space makes Supraspinatus tendon prone to inflammation due to friction = can lead to rotator cuff tendinitis
Supraspinatus tendon involvement can be diagnosed by painful arc test = where pain due to ss tendon impingement can be felt between 60-120 degrees abduction
What is scapulohumeral rhythm
Collaborative movements of scapulothoracic and glenohumeral joints = increase rom in shoulder abduction
What is scapulohumeral rhythm = what contributes to it
Each joint contributes to total abduction range
Glenohumeral = 120 degrees
Scapulothoracic (acc sternoclavicular)= 60 degrees for a total of 180 degrees
Describe first 30 degrees abduction of shoulder
Movement happens at glenohumeral joint, mainly Supraspinatus
Describe >30 degrees abduction of shoulder
Involves concurrent movements at sternoclavicular (trapezius, Serratus anterior in upwards rotation)
AND gelnohumeral joints (lateral deltoid and Supraspinatus)
Infraspinatus attachments
Infraspinous border to middle facet greater tubercle
Infraspinatus Functions
Lateral rotation (external)
Infraspinatus Innervation
Supra scapular nerve c5-6
Teres minor attachment
Inferior border scapula to inferior facet greater tubercle
Teres minor Function
Adduction = weak
Lateral rotation
Teres minor Innervation
Axiallary nerve - c5-c6
Subscapularis attachments
Subscapular fossa to lesser tubercle humerus
(Mirror of Teres minor and infraspinatus = reverse motions)
Subscapularis Function
Medial rotation
Weak adduction
(Swimming stroke)
Subscapularis Innervation
Superior and inferior subscapular nerves c5-c6
Name shoulder muscles
Deltoid
Teres major
Deltoid attachments
Triangular shaped
Spinal part = posterior scapula
Acromial part = lateral acromion
Clavicular part = anterior clavicle
Scapula and clavicle —> deltoid tuberosity
Deltoid Function
Clavicular - anterior = flexion
Acromial - Lateral = abduction
Spinal - posterior = extension from flexed position - bring it back
Deltoid Innervation
Axilalry nerve - c5-c6
Deltoid Clinical correlate
Subdeltoid bursa connected to subacromial bursa, between Supraspinatus tendon (deep) and deltoid muscle (superficial)
Bursae are prone to inflammation and swelling = bursitis, further narrowing subacromial space and contributing to Supraspinatus impingement in rotator cuff tendinitis
Teres major attachment
Inferior angle scapula (posterior) to crest of lesser tubercle of humerus (anterior)
Back to front muscle, so on other side fo longitudinal axis rotation —>has opposite action to Teres minor
Teres major FUCNTION
Adduction
Medial rotation
Extension when shoulder flexed
Teres major INNervation
Lower subscapular nerve c5-c6
Name thoracohumeral muscles
Thorax muscles with shoulder actions = latissimus dorsi and Pectoralis major
Thoracoappendicular muscles
Attachments latissimus dorsi
Vertebrae, ilium and tlf to floor of intertubercuar groove of humerus
Back to front muscle like Teres major
fucntion latissimus dorsi
Crosses both scapulothoracic and shoulder joints
= adduction (strong adductor of shoulder joint), medial rotation
innervation latissimus dorsi
Thoracodorsal nerve c6-c8
Attachments Pectoralis major
From clavicle, sternum and ribs (3 parts) to crest of greater tubercle of humerus - all converge
Pectoralis major FUCNTION
Medial rotation
Adduction
Pectoralis major Innervation
Medial pectoral nerve c8-t1
Lateral pectoral nerve c5-c7
How to get pure adduction of shoulder
Latissimus, Teres major and Pectoralis major all do medial rotation
Teres minor and infraspinatus need to counteract bc do lateral rotation
=recruit all to get pure adduction
Describe attachment of certain muscles to proximal humerus
Pectoral major = lateral/greater crest
Latissimus dorsi = floor interbercular groove
Teres major = crest of lesser tubercle
“Miss between 2 majors”
(All on anterior side)
Define bursa
Thin fluid filled sac that reduces friction between muscle and surrounding structures
