The Shoulder Complex

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The Shoulder Complex
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The Shoulder Complex

1. General Structure Function
2. Structure Function of Specific Joints
3. Muscular Considerations
4. Specific Functional Considerations
5. Common Injuries

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The Shoulder Complex

• General Structure Function
• Structure Function of Specific Joints
• Muscular Considerations
• Specific Functional Considerations
• Common Injuries

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General Structure
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General Function

• Provides very mobile, yet strong base for hand to
  perform its intricate gross and skilled functions
• Transmits loads from upper extremity to axial
  skeleton

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Shoulder Girdle
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Shoulder Complex Movements

• Shoulder Girdle
• Elevation depression
• Protraction retraction
• Upward downward rotation
• Upward tilt
• Shoulder (glenohumeral)
• FL, EXT, HyperEXT
• ABD, ADD, HyperADD, HyperABD
• MR, LR, HorizontalABD, HorizontalADD

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Abduction/Lateral Tilt (Protraction)
Linear Movement Frontal Plane Angular
movement Transverse Plane
Adduction/Reduced Lateral Tilt (Retraction)
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Depression
Elevation
Linear Movement Frontal Plane
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Downward rotation
Upward rotation
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Shoulder Complex Movements
Upward tilt Reduction of Upward Tilt Angular
movement Sagittal plane
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Limited by capsular torsion
Limited by bony impingement of greater tubercle
on acromion
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Large ROM Due To

• Poor bony structure
• Poor ligamentous restraint
• Scapulohumeral cooperative action

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The Shoulder Complex

1. General Structure Function
2. Structure Function of Specific Joints
3. Muscular Considerations
4. Specific Functional Considerations
5. Common Injuries

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Structure Function of Specific Joints

1. Sternoclavicular Joint
2. Acromioclavicular Joint
3. Scapulothoracic Joint
4. Glenolhumeral Joint
5. Coracoacromial Arch

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Sternoclavicular Joint Bony Structure
Poor Diarthrodial Biaxial
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Sternoclavicular Joint Capsule
Very strong
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Sternoclavicular Joint Interclavicular Ligament
Resists superior anterior (posterior portion)
motion
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Sternoclavicular Joint Sternoclavicular Ligament
Resists anterior (PSL), posterior (ASL),
superior motion
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Sternoclavicular Joint Costoclavicular Ligament
Resists upward and posterior motion
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Sternoclavicular Joint Accessory Structures
Resists medial inferior displacement via
articular contact
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Sternoclavicular Joint Articular Surfaces

• Medial end of clavice
• is convex
• Clavicular facet is
• reciprocally shaped

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Sternoclavicular Joint Motions
Axial Rotation 50 EL/DEP 35 PROT/RET 35
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Sternoclavicular Joint Motions

• Frontal plane
• Elev/Dep
• Sagittal plane
• Post Rot
• Horizontal plane
• ProT/ReT
• Ant/Post axis
• Vertical axis

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Acromioclavicular JointBony Structure
Poor Diarthrodial Nonaxial
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Acromioclavicular JointJoint Capsule
Very weak
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Acromioclavicular JointAcromioclavicular Ligament
Resists axial rotation posterior motion
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Acromioclavicular JointCoracoclavicular Ligament
Resists superior motion
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Acromioclavicular JointAccessory Structures
Articular disc
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Acromioclavicular Joint Motion
Little relative motion at AC joint
UR/DR 60 EL/DEP 30 PROT/RET 30-50
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Acromioclavicular Joint Osteokinematics

• Horizontal plane
• adjustments
• during scapulothoracic
• protraction
• Sagittal plane adjustment
• during scapulothoracic
• elevation

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Clavicle

• Acts a strut connecting upper extremity to thorax
• Protects brachial plexus vascular structures
• Serves as attachment site for many shoulder
  muscles

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Scapula
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Scapular Plane
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Scapulothoracic Joint

• No osseous connection
• SUBSCAP SA

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Glenohumeral Joint Humerus
Retroversion angle 30
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Glenohumeral Joint Humerus
Inclination angle 45
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Glenohumeral Joint Glenoid Fossa

• Inclination angle 5
• Retroversion angle 7

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Glenohumeral Joint Glenoid Fossa

• Articular cartilage thicker on periphery
• Shallow fossa 1/3 diameter of humeral head

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Glenohumeral Joint Bony Structure

• Pure rotation
• Bony restraint poor
• Head 4-5X larger than fossa
• Close-packed position
• ABD with LR

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Glenohumeral Joint Joint Capsule

• Inherently lax
• Surface area 2X head
• Provides restraint for ABD, ADD, LR, MR

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Glenohumeral JointSuperior GH Ligament

• Resists inferior translation in rest or adducted
  arm
• Well-developed in 50

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Glenohumeral Joint Coracohumeral Ligament

• Resists inferior translation in shoulders with
  less-developed SGH

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Glenohumeral JointMiddle GH Ligament

• Great variability in proximal attachment
  morphology
• Absent in 30
• Resists inferior translation in ABD ER
• Restrains anterior translation (45 ABD)

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Glenohumeral JointInferior GH Ligament

• 3 components (A,P,Ax)
• Resists inferior, anterior, posterior
  translation

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Glenohumeral Joint Bursae

• Subcoracoid
• Subacromial
• Subscapular

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Glenohumeral Joint Accessory Structures
Labrum

• 50 of depth
• Increases tangential stability 20

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Glenohumeral Joint Intra-articular Pressure

• Synovial fluid causes adhesion
• Provides 50 restraint

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Coracoacromial Arch
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Glenohumeral Joint ROM

• Flexion (167 W 171 M)
• 30 in max LR
• Extension (60)
• Abduction (180)
• 60 in max IR
• Hyperadduction (75)

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Glenohumeral Joint ROM

• Total rotation 180
• Total ROT 90 in 90 ABD

• Medial rotation (90)
• Lateral rotation (90)
• Horizontal abduction (45)
• Horizontal adduction (135)

Role of multiarticular muscles???
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Glenohumeral Joint ROM

• Medial rotation (90)
• Lateral rotation (90)
• Horizontal abduction (45)
• Horizontal adduction (135)

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Soft Tissue Restraint Summary

• Anterior
• Capsule
• Labrum
• Glenohumeral lig
• Coracohumeral lig
• Subscapularis
• Pectoralis major
• Inferior
• Capsule
• Triceps brachii (L)

• Posterior
• Capsule
• Labrum
• Teres minor
• Infraspinatus
• Superior
• Labrum
• Coracohumeral lig
• Suprapinatus
• Biceps brachii (L)
• Coracoacromial arch
• Subacromial bursa

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The Shoulder Complex

1. General Structure Function
2. Structure Function of Specific Joints
3. Muscular Considerations
4. Specific Functional Considerations
5. Common Injuries

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Shoulder girdle has its own set of muscles.
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Retraction of the Scapulothoracic Joint
Levator scapula
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Protraction of the Scapulothoracic Joint
Pectoralis minor
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Pathomechanics of a weak serratus anterior muscle

• Deltoid force causes scapula to downwardly
  rotate.

Unstable and cannot resist deltoid force
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GH Flexion

• Prime flexors
• Anterior deltoid
• Pectoralis major clavicular portion
• Assistant flexors
• Coracobrachialis
• Biceps brachii short head

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GH Flexion

• Anterior deltoid
• Coracobrachialis
• Biceps brachii

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GH Extension

• Gravitational force
• Posterior deltoid
• Latissimus dorsi
• Pectoralis major (sternal)
• Teres major (with resistance)

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Abduction at Glenohumeral Joint

• Major abductors of humerus
• Supraspinatus
• Initiates abduction
• Active for first 110 degrees of abduction
• Middle deltoid
• Active 90-180 degrees of abduction
• Superior dislocating component neutralized by
  infraspinatus, subscapularis, and teres minor

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Abduction at Glenohumeral Joint
Initiates abduction Active for first 110 degrees
of abduction
Active 90-180 degrees of abduction Superior
dislocating componentneutralized by
infraspinatus, subscapularis, and teres minor
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Abduction at Glenohumeral Joint The Kinetic Arc
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Adduction of Glenohumeral Joint

• Primary adductors
• Latissimus dorsi
• Teres major
• Sternocostal pectoralis
• Minor assistance
• Biceps brachii short head
• Triceps brachii long head
• Above 90 degrees- coracobrachialis and
  subscapularis

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GH Medial Rotation

• Subscapularis
• Latissimus dorsi
• Pectoralis major
• Teres major (with resistance)

Decreased activity with ABD
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GH Lateral Rotation

• Primary
• Infraspinatus
• Assistant
• Teres minor
• Posterior deltoid

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Horizontal Adduction and Abduction

• Anterior to joint
• Pectoralis major (both heads), anterior deltoid,
  coracobrachialis
• Assisted by short head of biceps brachi
• Posterior to joint
• Middle and posterior deltoid, infraspinatus,
  teres minor
• Assisted by teres major, latissimus dorsi

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Muscle Strength

• Adduction (2X ABD)
• Extension
• Flexion
• Abduction
• Internal rotation (max in neutral)
• External rotation (max at 90 FL)

Role of multiarticular muscles???
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The Shoulder Complex

1. General Structure Function
2. Structure Function of Specific Joints
3. Muscular Considerations
4. Specific Functional Considerations
5. Common Injuries

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Specific Functional Considerations

• Stability Functions of Shoulder Girdle
• Mobility Functions of Shoulder Girdle
• Rotator Cuff Function

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Stability Functions of Shoulder Girdle

• Provides stable base from which shoulder muscles
  can generate force
• Shoulder girdle muscles as stabilizers
• Maintain appropriate force-length relationship
• Maintain maximum congruence of shoulder joint

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Specific Functional Considerations

• Stability Functions of Shoulder Girdle
• Mobility Functions of Shoulder Girdle
• Rotator Cuff Function

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Mobility Functions of Shoulder Girdle

• Permits largest ROM of any complex in the body
• Shoulder girdle increases ROM with less
  compromise of stability (scapulohumeral rhythm)
  (4 joints vs. 1 joint)
• Facilitate movements of the upper extremity by
  positioning GH favorably

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Dynamic Stabilization Mechanisms

• Passive muscle tension
• Compressive forces from muscle contraction
• Joint motion that results in tightening of
  passive structures
• Redirection of joint force toward center of GH
  joint

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Muscular Considerations

• Force-length relationships quite variable due to
  multiple joints
• Tension development in agonist frequently
  requires tension development in antagonist to
  prevent dislocation of the humeral head
• Force couple 2 forces equal in magnitude but
  opposite in direction

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Movements in the Frontal PlaneGH Joint -
Abduction
ABD - 60 UR - 20

• Shoulder Girdle UR
• Totals
• Upward rotation - 60
• GH Abduction - 120
• 21 (.66) ratio
• 1.251 after 30
• 0.5-0.75 across individuals

ABD - 30 UR - 40
ABD 30
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Movements in the Frontal PlaneGH Joint -
Adduction

• Shoulder Girdle DR

Fig 5.17
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Movements in the Sagittal PlaneGH Joint
Flexion Extension

• Shoulder Girdle
• UR
• ELEV (gt90)
• PROT ( to 90)
• RET (gt90)

Fig 5.18
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Movements in the Sagittal PlaneGH Joint -
Hyperextension

• Shoulder Girdle Upward tilt of scapula

Fig 5.20
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Movements in the Transverse PlaneGH Joint MR
LR
Fig 5.22a
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Spinal Contribution to GH Motion
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Movements in the Transverse PlaneGH HAdd HAbd
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Influences on GH ROM

• Humeral position in other planes
• FL limited by ER (30? FL in max ER)
• ABD limited by IR (60?-90? ABD in max IR)
• ABD with ER 90-120?
• Rotation limited by ABD (total ROT only 90? in
  90? ABD)
• Scapular position
• Elbow position

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Large ROM Due To

• Poor bony structure
• Poor ligamentous restraint
• Scapulohumeral coordination

• Normal movement dependent on interrelationships
  of 4 joints
• Restriction in any of these four can impair
  normal function

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Specific Functional Considerations

• Stability Functions of Shoulder Girdle
• Mobility Functions of Shoulder Girdle
• Rotator Cuff Function

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Teres minor
Supraspinatus
Subscapularis
Infraspinatus
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Function of Rotator Cuff

• Large external muscles (e.g., lats, delts) create
  shear forces
• Rotator cuff provides
• Joint compression
• Tangential restraint (Ant, Post, Sup)

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Destabilizing Action of Deltoid
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Deltoid produces superior shear force at GH joint.
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Subscapularis

• Resists superior shear
• Produces simultaneous internal rotation

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Infraspinatus Teres Minor

• Resists superior shear
• Neutralizes SUBSCAP internal rotation

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Supraspinatus
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Summary of Active Arthrokinematics Resisting Shear
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Destabilizing Action of Latissimus Dorsi

• LD pulls humerus INF
• SSP resists INF force
• INF SUBSCAP create compressive force

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The Shoulder Complex

1. General Structure Function
2. Structure Function of Specific Joints
3. Muscular Considerations
4. Specific Functional Considerations
5. Common Injuries

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Common Shoulder Injuries

• Joint dislocations
• Clavicular fracture
• Rotator cuff injuries
• Other rotational injuries
• Subscapular neuropathy

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Evaluation of Injuries

• Mechanism of Injury (MOI)
• How did the injury occur?
• Pathology (PATH)
• What tissues are damaged?
• Sign Symptoms (SS)
• What does the patient tell you?
• What can be determined from an evaluation of the
  injury?

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Joint Dislocations Acromioclavicular Sprain

• AKA Shoulder Separation
• MOI Downward blow to outer end of shoulder
• Fall on outstretched hand, Punching
• PATH Sprain of AC ligaments
• SS Pain over AC joint
• Laxity of AC joint???

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Joint DislocationsShoulder Dislocation

• MOI Arm forcefully ABD LR
• May occur by a blow to top of shoulder
• PATH Head of humerus is forced out of the
  glenoid fossa
• SS Arm held out from side in slight ABD LR
• Loss of normal rounded contour of deltoid muscle

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Chronic Dislocation of the Shoulder

• MOI Congenital abnormality
• Repeated acute dislocations
• PATH Head of humerus relatively easily come out
  of the glenoid fossa
• Tissue damage due to repeated dislocations
• SS Usually not very painful

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Clavicular Fracture

• MOI Downward blow to outer end of shoulder
• Fall on outstretched hand
• PATH Fracture to middle 1/3
• SS Patient supports injured arm
• Head may be tilted toward injured side with face
  turned to opposite side

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Rotator Cuff Injuries

• MOI Overuse
• Falling on an outstretched hand
• PATH Strains or tearing of rotator cuff muscles
• Supraspinatus most often injured
• SS Pain, Inflammation, Weakness

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Impingement

• Possible mechanisms
• Weak or inflexible rotator cuff
• Small anatomical space
• Hyperabduction of GH joint
• GH ABD ROT

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Impingement Roll-Slide Kinematics
Roll created by abduction not countered with
Slide action
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Rotator Cuff Injury

• Anatomical cause of rotator cuff injury
• Kinesiological cause of injury

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Impingement

• Narrow space
• Inextensibility of capsule, ligaments, muscles
  esp. rotator cuff
• Abduction and internal/external rotations

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• During ABD
• SSP tendon pushed into acromion process CA
  ligament
• During ROT
• SSP tendon dragged along the inferior surface of
  the acromion process

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Rotator Cuff Injury

• Anatomical cause of rotator cuff injury
• Kinesiological cause of injury

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Kinesiological breakdown of overhand throwing
Wind-Up Phase
No excessive movements
(safe)
First Motion
Maximum knee lift of leg
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Kinesiological breakdown of overhand throwing

• Shoulder ABD (DELT SSP)
• RC maintain proper humeral head position

Stride
Abduction and no rotation
(Safe)
Lead leg begins to move Arms separate
Lead foot contacts the ground
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Kinesiological breakdown of overhand throwing

• ER in ABD position ER 150-180
• ECC action of SUBSCAP (decelerates ER humerus)
• RC stabilization

Arm Cocking
External rotation in abducted position
Possible cuff damage
Lead foot contact
Maximum shoulder external rotation
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Kinesiological breakdown of overhand throwing
Arm Acceleration

• Concentric IR (PMJR LD )
• IR velocity (gt 1000 /s)
• RC stabilization

Internal rotation in abducted position
Possible cuff damage
Maximum shoulder ER
Ball release
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Kinesiological breakdown of overhand throwing
Arm Deceleration

• Decelerating IR ADD
• ECC action of TMin
• RC stabilization

Internal rotation Abduction reduced
Safer
Ball release
Maximum shoulder IR
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Kinesiological breakdown of overhand throwing
Follow Through

• Decelerating IR
• ECC action of TMin
• RC stabilization

Reduced internal rotation
Safe
Maximum shoulder IR
Ends in balanced position
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Rotator Cuff Injuries Solution

• Alter technique during problem phases to avoid
  impingement
• Arm cocking
• Arm acceleration
• Strengthen rotator cuff
• Surgical repair

Video techniques
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Risk Factors

• Risk factor a characteristic that influences
  the loading on the musculoskeletal system
• Movement risk factors characteristics of a
  movement
• Intrinsic risk factors the personal, physical,
  and psychological characteristics of an
  individual
• Extrinsic risk factors the environmental and
  administrative procedures

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Intrinsic Risk Factors

• Age and gender
• Physical fitness
• Overtraining
• Skeletal abnormalities
• Technique
• Warm-up
• Psychological factors

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Technique

• Technique refers to the movement pattern of an
  individual during a particular movement or
  sequence of movements. Good technique is a
  movement pattern not only effective in
  performance, but also one that minimizes risk of
  injury by appropriately distributing the overall
  load throughout the kinetic chain. Poor technique
  is characterized by inappropriate utilization and
  summation of muscular effort and abnormal joint
  movements, both of which result in localized
  overload and, therefore, increased risk of injury.

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Swimming

• Solutions
• Lead with hand to ? IR
• Increase body roll to ? ABD

Mechanism ABD IR
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Supraspinatus Tear
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Other Rotational Injuries

• Tears of labrum
• Mostly in anterior-superior region
• Tears of biceps brachii tendon
• Due to forceful rotational movements
• Also calcification of soft tissues, degenerative
  changes in articular surfaces, bursitis

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Biceps Tendon Tear
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Subscapular Neuropathy

• Denervation of INF with ? strength GH ER
• Mechanism Repeated stretching of nerve

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Loads on the Shoulder

• Arm segment moment arm
• Perpendicular distance between weight vector and
  shoulder.
• With elbow flexion, upper arm and forearm/hand
  segments must be analyzed separately.
• Large torques from extended moment arms countered
  by shoulder muscles.
• Load reduced by half with maximal elbow flexion

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Injury Potential in the Shoulder Complex -
Impacts

• Sternoclavicular Joint
• not commonly injured
• may sprain anteriorly if fall on top of shoulder
  or middle delt - pain in horizontal abd
• children may dislocate anteriorly during throwing
  because of increased joint mobility as compared
  to adults
• posterior dislocation may occur when force is
  applied to sternal end of clavicle serious
  because of trachea, esophagus, and blood vessels
  located posteriorly

• Clavicular Injuries
• fx to any part due to direct trauma
• fx to middle 1/3 can occur by falling on
  shoulder, outstretched arm, or direct trauma to
  shoulder that transmits force down shaft of
  clavicle
• AC Injuries
• dislocation from fall on shoulder, fall on elbow
  or outstretched arm
• overuse injuries from overhand pattern (throwing,
  tennis, swimming) or sports that repeatedly load
  in the overhead position (wrestling, wt lifting)

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Glenohumeral Injuries

• Most common dislocation in anterior
  (anterior-inferior 95)
• most commonly dislocated when abducted and ER
  overhead
• recurrence rate 33-50 (66-90 lt20 yrs)