The Shoulder Joint

Scapulohumeral Rhythm

Function: Maximize ROM Maintain glenoid fossa in optimal

position Maintain optimal length-tension

relationship

Scapulohumeral Rhythm

1800 = 1200 G-H + 600 S-T

G-H:S-T = 2:1 over entire range

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)

Scapulohumeral RhythmPhase I / S-T Motion

Trapezius (upper & lower) & Serratus Anterior (upper & lower) contract

Coracoclavicular ligament tightens (locks AC joint)

Scapulohumeral RhythmPhase I / S-T Motion

Clavicle elevates ~ 300 thru SC joint

Costoclavicular ligament tightens

Tipping and 100 of winging

Scapulohumeral RhythmPhase I / S-T Motion

Total motion following Phase I:

300 of scapula rotation occurring at SC jt.

~ 300 of G-H movement

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

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

Scapulohumeral RhythmPhase II / A-C Motion

Rotation of scapula about axis through A-C joint

200 tipping / 400 winging

Scapulohumeral RhythmPhase II / A-C Motion

Total elevation = 90 - 1200 (pre-phase + phase I) 300 (S-T rotation)

+ 30-600 (G-H movement) 1800

Scapulohumeral RhythmSummary

0 to 900 = 600 GH / 300 SH about SC joint

900 to 1800 = 600 GH / 300 SH about AC joint

Acromioclavicular Sprain

Plane-synovial joint

Intraarticular disk – degenerates w/ age

Separation

Acromioclavicular Sprain

Mechanisms: Direct force

Indirect force (less frequent)outstretched arm

Acromioclavicular Sprain

I: sprain of AC ligaments

II: tear of AC ligament / sprain of coracoclavicular

Acromioclavicular Sprain

Acromioclavicular Sprain

III: tear of AC and coracoclavicular ligaments

IV: torn ligaments / posterior displacement of clavicle

Acromioclavicular Sprain

Acromioclavicular Sprain

V: torn ligaments / inferior displacement of clavicle

VI: torn ligaments / clavicle driven into subacromial / subcoracoid position

Acromioclavicular Sprain

Glenohumeral Joint

Stability - intracapsular pressure (20-32 lbs.)

Concavity compression

Capsuloligamentous structures

Glenohumeral Joint

Stability Scapulohumeral balance ()

Glenohumeral Joint - stable

Glenohumeral Joint -unstable

Glenohumeral Joint

Dislocation > 90% anterior

Indirect

Direct

Glenohumeral Joint

Glenohumeral Joint

Impingement

Supraspinatus tendon & subacromial bursa

Acromion and coracromial ligament/arch

Impingement

Repetitive (< 35 y.o.)

Degenerative (> 35 y.o) spur formation capsular thinning tissue perfusion muscular atrophy

Repetitive Impingement

Repeated abduction stresses capsuloligamentous & musculotendinous

Tissue microtrauma tissue failure

GH instability subluxation

Impingement

Classification:I. Isolated impingement w/ no instabilityII. Overuse 20 overhead activities

instability w/ secondary impingementIII. II but w/ generalized (systemic)

ligamentous laxityIV. Traumatic – indirect or direct

Mechanisms of RTC Impingement

Extrinsic - forces outside RTC structural characteristics of

subacromial space

Intrinsic - inflammatory changes within the cuff

Extrinsic

Structural acromion shape

hooked > flat or curved

Spurs stress risers

Extrinsic

Structural Supraspinatu

s outlet

Intrinsic

Inherent due to compromised blood flow 20:

Impingement pressures Avascularity

Risk Factors

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

Populations

W/C athletes Pitchers Swimmers

RTC Rupture

Inflammation microtearing partial or full rupture

Compromised tissue integrity & muscle fatigue altered movement patterns

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

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