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 Rhythm Pre-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 Rhythm Phase I / S-T Motion Trapezius (upper & lower) & Serratus Anterior (upper & lower) contract Coracoclavicular ligament tightens (locks AC joint)

Scapulohumeral Rhythm Phase I / S-T Motion Clavicle elevates ~ 300 thru SC joint Costoclavicular ligament tightens Tipping and 100 of winging

Scapulohumeral Rhythm Phase I / S-T Motion Total motion following Phase I: 300 of scapula rotation occurring at SC jt. ~ 300 of G-H movement

Scapulohumeral Rhythm Phase 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 Rhythm Phase II / A-C Motion Taut coracoclavicular ligament pulls down on coracoid Pulls conoid tubercle of clavicle down Rotation of clavicle about long axis

Scapulohumeral Rhythm Phase II / A-C Motion Rotation of scapula about axis through A-C joint 200 tipping / 400 winging

Scapulohumeral Rhythm Phase II / A-C Motion Total elevation = 90 - 1200 (pre-phase + phase I) 300 (S-T rotation) + 30-600 (G-H movement) 1800

Scapulohumeral Rhythm Summary 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 instability II. Overuse 20 overhead activities instability w/ secondary impingement III.  II but w/ generalized (systemic) ligamentous laxity IV. 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 Supraspinatus 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