The Shoulder Joint

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The Shoulder Joint
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Scapulohumeral Rhythm

• Function
• Maximize ROM
• Maintain glenoid fossa in optimal position
• Maintain optimal length-tension relationship

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Scapulohumeral Rhythm

• 1800 ? 1200 G-H 600 S-T
• G-HS-T 21 over entire range

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Scapulohumeral RhythmPre-phase/Setting

• Inconsistent amount of scapula movement ?
  Proximal STABILITY for distal mobility
• G-H - 600 ? or 300 abduction
• Total 30-600 (all G-H motion)

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Scapulohumeral RhythmPhase I / S-T Motion

• Trapezius (upper lower) Serratus Anterior
  (upper lower) contract
• Coracoclavicular ligament tightens (locks AC
  joint)

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Scapulohumeral RhythmPhase I / S-T Motion

• Clavicle elevates 300 thru SC joint

• Costoclavicular ligament tightens

• Tipping and 100 of winging

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Scapulohumeral RhythmPhase I / S-T Motion

• Total motion following Phase I
• 300 of scapula rotation occurring at SC jt.
• 300 of G-H movement

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Scapulohumeral RhythmPhase I / S-T Motion

• Total elevation
• 30-600 (pre-phase G-H)
• 300 (S-T rotation)
• 300 (G-H movement)
• 90 1200 of total elevation

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Scapulohumeral RhythmPhase II / A-C Motion

• Taut coracoclavicular ligament pulls down on
  coracoid

• Pulls conoid tubercle of clavicle down

• Rotation of clavicle about long axis

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Scapulohumeral RhythmPhase II / A-C Motion

• Rotation of scapula about axis through A-C joint
• 200 tipping / 400 winging

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Scapulohumeral RhythmPhase II / A-C Motion

• Total elevation
• 90 - 1200 (pre-phase phase I)
• 300 (S-T rotation)
• 30-600 (G-H movement)
• 1800

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Scapulohumeral RhythmSummary

• 0 to 900 ? 600 GH / 300 SH about SC joint
• 900 to 1800 ? 600 GH / 300 SH about AC joint

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Acromioclavicular Sprain

• Plane-synovial joint
• Intraarticular disk degenerates w/ age
• Separation

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Acromioclavicular Sprain

• Mechanisms
• Direct force
• Indirect force (less frequent)
• outstretched arm

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Acromioclavicular Sprain

• I sprain of AC ligaments
• II tear of AC ligament / sprain of
  coracoclavicular

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Acromioclavicular Sprain
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Acromioclavicular Sprain

• III tear of AC and coracoclavicular ligaments
• IV torn ligaments / posterior displacement of
  clavicle

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Acromioclavicular Sprain
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Acromioclavicular Sprain

• V torn ligaments / inferior displacement of
  clavicle
• VI torn ligaments / clavicle driven into
  subacromial / subcoracoid position

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Acromioclavicular Sprain
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Glenohumeral Joint

• Stability
• - intracapsular pressure (20-32 lbs.)
• Concavity compression
• Capsuloligamentous structures

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Glenohumeral Joint

• Stability
• Scapulohumeral balance (?)

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Glenohumeral Joint - stable
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Glenohumeral Joint -unstable
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Glenohumeral Joint

• Dislocation
• gt 90 anterior
• Indirect
• Direct

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Glenohumeral Joint
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Glenohumeral Joint
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Impingement

• Supraspinatus tendon subacromial bursa
• Acromion and coracromial ligament/arch

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Impingement

• Repetitive (lt 35 y.o.)
• Degenerative (gt 35 y.o)
• spur formation
• capsular thinning
• ? tissue perfusion
• muscular atrophy

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Repetitive Impingement

• Repeated abduction ? stresses capsuloligamentous
  musculotendinous
• Tissue microtrauma ? tissue failure ?
• GH instability ? subluxation

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Impingement

• Classification
• I. Isolated impingement w/ no instability
• II. Overuse 20 overhead activities
• instability w/ secondary impingement
• III. ? II but w/ generalized (systemic)
  ligamentous laxity
• IV. Traumatic indirect or direct

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Mechanisms of RTC Impingement

• Extrinsic - forces outside RTC
• structural characteristics of subacromial space
• Intrinsic - inflammatory changes within the cuff

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Extrinsic

• Structural
• acromion shape
• hooked gt flat or curved
• Spurs ? stress risers

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Extrinsic

• Structural
• Supraspinatus outlet

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Intrinsic

• Inherent due to compromised blood flow 20
• Impingement pressures
• Avascularity

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Risk Factors

• Awkward / static postures
• Heavy work
• Direct load bearing
• Repetitive UE movement
• Overhead movements

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Populations

• W/C athletes
• Pitchers
• Swimmers

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RTC Rupture

• Inflammation ? microtearing ? partial or full
  rupture
• Compromised tissue integrity muscle fatigue ?
  altered movement patterns

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Kinematic Patterns w/ RTC Tears

• I stable fulcrum supraspinatus part of
  infra ? normal motion / near-normal strength
• II unstable fulcrum supraspinatus infra and
  TM ? disruption of force couples

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Kinematic Patterns w/ RTC Tears

• III captured fulcrum supraspinatus, post
  cuff, subscapularis ?? centering of humeral head
  ?? humeral elevation
• IV unstable fulcrum supraspinatus complete
  subscapularis ? disruption of force couples ?
  poor elevation