Shoulder exam and anatomy Flashcards

Glenohumeral joint anatomy, stabilizer, biomechanics acromioclavicular joint sternoclavicular joint oa acromiale

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1
Q

What is the scapular plane?

A
  • 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 120o
    *
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2
Q

What movement happen in abduction?

A
  • At 2 joints
  • 120o from glenohumeral joint
  • 60o from scapulothoracic
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3
Q

Can you decribe the static restraints in the glenohumeral joint?

A
  • Negative intra-articular pressure
  • Articular congruity and version
  • Glenohumeral ligaments
  • Glenoid labrum
  • = NAGG
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4
Q

Describe the dynamic restraints to glenohumeral joint?

A
  • Rotator cuff muscles
  • Biceps
  • Periscapular muscles
  • = RBP
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5
Q

Describe the glenohumeral ligaments of the shoulder?

A
  • Superior Glenohumeral ligament
    • Restraint to Inferior translation at 0o 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 90o 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
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6
Q

Describe the anatomy of th labrum?

A
  • 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
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7
Q

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

A
  • 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
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8
Q

Describe the osteology of the glenohumeral joint?

A
  • Humeral head
    • retroverted 30o from transepicondylar axis of distal humeral shaft
    • articular surface inclined upwards 130o 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 5o
    • average version is 5o 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
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9
Q

Can you draw a free body diagram of the arm?

A
  • Assuming A= 3cm and B= 30cm
  • Sum of all moments M =0
  • (AxD)- (Bx0.5W)=0
  • 3D=0.5W (30)
  • D= 5W
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10
Q

What is the position you arthrodese a shoulder in ?

A
  • 15-20o Abduction
  • 20-25o forward flexion
  • 40-50o internal rotation
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11
Q

Describe the anatomy of the acromioclavicular joint?

A
  • A diarthrodial joint ( allows max movement)
  • fibrocartilaginous intraarticualr disc between osseous segments
  • majority of motion is from bones, not thru joint
    • clacvicle rotates 45o
    • 8o 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
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12
Q

Describe the anatomy of the sternoclavicular joint?

A
  • A diathrodial saddle joint incongruous ( 50% contact)
    • fibrocartilage
    • contains intrarticular disc
  • motion
    • elevation of arm to 90o -> rotation at SC j of 30o
  • 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
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13
Q

Describe when the clavicle ossifies?

A
  • 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
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14
Q

Describe the motion of the scapulothoracic joint?

A
  • 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 0-120o then scapulothoracic does 60o
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15
Q

What is os acrominale?

A
  • 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
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16
Q

Describe the 3 ossification centres of the acromium?

A
  • Meta-acromium = base
  • Meso-acromium= mid
  • Pre-acromium=tip
17
Q

What is the presentation of a pt with os acrominale?

A
  • Signs & symptoms of impingment
18
Q

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

A
  • Axillary lateral
19
Q

What is the tx of os acrominale?

A

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