Shoulder exam and anatomy

Question 1

What is the scapular plane?

Answer 1

• 30 ^o anterior to the coronal plane.
• Abuction require external rotation to allow the greater tuberosity to miss the acromium.
• if pt has internal rotation contraction they cannot abduct beyond 120^o
  *

Question 2

What movement happen in abduction?

Answer 2

• At 2 joints
• 120^o from glenohumeral joint
• 60^o from scapulothoracic

Question 3

Can you decribe the static restraints in the glenohumeral joint?

Answer 3

• Negative intra-articular pressure
• ​Articular congruity and version
• Glenohumeral ligaments
• Glenoid labrum
• = NAGG

Question 4

Describe the dynamic restraints to glenohumeral joint?

Answer 4

• Rotator cuff muscles
• Biceps
• Periscapular muscles
• = RBP

Question 5

Describe the glenohumeral ligaments of the shoulder?

Answer 5

• Superior Glenohumeral ligament
  
  • Restraint to Inferior translation at 0^o of abduction
• Medial Glenohumeral ligament
  
  • restraint anterior and posterior translation in midrange of abduction 45o ER
• Inferior Glenohumeral ligament
  
  • posterior band of IGHL
    
    • most important restraint to Posterior subluxation at 90^o flexion and IR
    • tightness -> internal impingment and increased shear forces on superior labrum ( linked to SLAP lesion)
  • Anterior band of IGHL
    
    • primary restraint to ant/inf translation at 90o flexion and max ER
    • anchors into ant labrum
    • forms weak link that prediposes to bankart lesions
  • Superior band IGHL
    
    • ***most important static stabiliser about the joint***
    • 100% increased strain on superior band of IGHL in presence of SLAP lesion
• Coracohumeral ligament
  
  • limits posterior translation w shoulder in flexion, adduction, IR
  • limits inferior translation & external rotation at adducted position

Question 6

Describe the anatomy of th labrum?

Answer 6

• Helps create a cavity-compression and creates 50% of glenoid socket depth
• composed of fibrocartilage tissue
• blood supply
  
  • suprascapular artery
  • ant humeral circumflex a
  • post humeral circumflex a
  • anterio-superior labrum poorest supply
• ​Stability
  
  • ​anterior labrum
    
    • ​anchors IGHL - weak -> bankart lesions
  • ​superior labrum
    
    • ​anchors biceps tendon -> weak-> SLAP

Question 7

Describe the anatomy of the soft tissue dynamic stabilisers of the glenoidhumeral joint?

Answer 7

• Posterior capsule (static)
  
  • thin <1mm no ligaments
• Rotator interval
  
  • included the SGHL, coraccohumeral ligament and long head of biceps that bridge gap between supraspinatus and subscapularis
  • boundaries
    
    • medial by coracoid base
    • superiorly by ant edge of supraspinatus
    • inferiorly by sup border of subscapularis
    • lateral apex formed by transverse humeral lig
• ​​Rotator cuff (dynamic)
  
  • ​subscapularis is an important stabiliser to post subluxation in external rotation
• ​Long head of biceps ( dynamic)
  
  • ​long head of bicpes acts as a humeral head depressor
  • variable origin from superior labrum
  • forms weak link that -> SLAP tear

Question 8

Describe the osteology of the glenohumeral joint?

Answer 8

• Humeral head
  
  • retroverted 30^o from transepicondylar axis of distal humeral shaft
  • articular surface inclined upwards 130^o from shaft
  • blood
    
    • ​Ascending branches of anterior humeral cicrumflex artery and arcuate artery
      
      • run parallel to lateral aspect of tendon of long head of biceps in bicipital groove
    • **Posterior humeral circumflex artery
    • *main blood supply to humeral head
• ​Glenoid
  
  • ​pear shaped av tilt 5^o
  • average version is 5^o retroversion in relation to axis of scapular body
• Coracoid
  
  • coracobrachialis, pect minor, short head of biceps attach to coracoid
• Acromium
  
  • normal acrominohumeral interval is 7-8mm
  • morphology
    
    • 1= flat
    • 2= curved
    • 3= hooked

Question 9

Can you draw a free body diagram of the arm?

Answer 9

• Assuming A= 3cm and B= 30cm
• Sum of all moments M =0
• (AxD)- (Bx0.5W)=0
• 3D=0.5W (30)
• D= 5W

Question 10

What is the position you arthrodese a shoulder in ?

Answer 10

• 15-20^o Abduction
• 20-25^o forward flexion
• 40-50^o internal rotation

Question 11

Describe the anatomy of the acromioclavicular joint?

Answer 11

• A diarthrodial joint ( allows max movement)
• fibrocartilaginous intraarticualr disc between osseous segments
• majority of motion is from bones, not thru joint
  
  • clacvicle rotates 45^o
  • 8^o thru ac joint rotation
  • rest thru scapular
  • joint limited to sliding motion
• Stablity
  
  • acromioclavicular lig
    
    • horizontal stability
    • sup, inf ant and post components
    • superior is strongest, then post
  • Coracoclavicular lig
    
    • trapezoid and conoid
    • provides vertical stability
    • trapezoid inserts 3cm from end of clavicle
    • conoid inserts 4.5cm from end of clavicle
  • capsule, deltoid and trapezius act as stabilisers

Question 12

Describe the anatomy of the sternoclavicular joint?

Answer 12

• A diathrodial saddle joint incongruous ( 50% contact)
  
  • fibrocartilage
  • contains intrarticular disc
• motion
  
  • elevation of arm to 90o -> rotation at SC j of 30^o
• imaging
  
  • Serendepity view
  • involves 400 dephalic tilt of sternum and clavicle
• Ligaments
• Posterior sternoclavicular lig
  
  • primary restraint for ant-post stability
• anterior sternoclavicular lig
  
  • primary restraint to sup displacement medial clavicle
• intra-art disc ligament
  
  • prevents medial displacment
• costoclavicular lig
  
  • prevents rotation and either lat/med displacement

Question 13

Describe when the clavicle ossifies?

Answer 13

• Clavicle is the 1st bone to ossify (5-6th wk gestation)
• last bone to complete ossification process
  
  • medial epiphysis of clavicle is last physis to close at 20-25 yrs

Question 14

Describe the motion of the scapulothoracic joint?

Answer 14

• Primary motion
  
  • elevation and depression
    
    • movement up & down along rib cage
• Secondary motion
  
  • protraction and retraction
    
    • movement away from and towards the vertebral column
• Shoulder abduction
  
  • GH joint 0-120^o then scapulothoracic does 60^o

Question 15

What is os acrominale?

Answer 15

• A unfused secondary ossification centre
• most common location is junction of meso and meta acromion
• important to distinguish from acromium fx
• incidence is 8%
• bilateral in 60%
• assoc conditions
  
  • shoulder impingment
  • rotator cuff disease
• Prognosis
  
  • poorer outcomes after RC repairs in pt with meso-os acromiale

Question 16

Describe the 3 ossification centres of the acromium?

Answer 16

• Meta-acromium = base
• Meso-acromium= mid
• Pre-acromium=tip

Question 17

What is the presentation of a pt with os acrominale?

Answer 17

• Signs & symptoms of impingment

Question 18

What is the best view to see on xray os acrominale?

Answer 18

• Axillary lateral

Question 19

What is the tx of os acrominale?

Answer 19

Non operative

• mild symptoms

Operative

• Two stage fusion and acromioplasty
  
  • symptomatic os acrominale w impingement
  • direct excision can -> deltoid dysfunction
  • a 2 stage proceedure may be required to
  • fuse the os acrominale w bone graft
  • 2nd preform acromioplasty