the shoulder complex. a.general structure & function b.structure & function of specific...

The Shoulder Complex


A. General Structure & Function

B. Structure & Function of Specific Joints

C. Muscular Considerations

D. Specific Functional Considerations

E. Common Injuries

General Structure

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

Shoulder Girdle

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

Abduction/Lateral Tilt (Protraction)

Adduction/Reduced Lateral Tilt (Retraction)

Linear MovementFrontal PlaneAngular movementTransverse Plane

Depression

Elevation

Linear MovementFrontal Plane

Downward rotation

Upward rotation

Shoulder Complex Movements

Upward tiltReduction of Upward Tilt

Angular movementSagittal plane

Limited by capsular torsion

Limited by bony impingement of greater tubercle on acromion

Large ROM Due To:

Poor bony structure Poor ligamentous restraint Scapulohumeral cooperative action






E. Common Injuries

Structure & Function of Specific Joints

1. Sternoclavicular Joint

2. Acromioclavicular Joint

3. Scapulothoracic Joint

4. Glenolhumeral Joint

5. Coracoacromial Arch

Sternoclavicular Joint: Bony Structure

PoorDiarthrodial Biaxial

Sternoclavicular Joint: Capsule

Very strong

Sternoclavicular Joint: Interclavicular Ligament

Resists superior & anterior (posterior portion) motion

Sternoclavicular Joint: Sternoclavicular Ligament

Resists anterior (PSL), posterior (ASL), & superior motion

Sternoclavicular Joint: Costoclavicular Ligament

Resists upward and posterior motion

Sternoclavicular Joint: Accessory Structures

Resists medial & inferior displacement via articular contact

Sternoclavicular Joint: Articular Surfaces

Medial end of clavice

is convex

Clavicular facet is

reciprocally shaped

Sternoclavicular Joint: Motions

Axial Rotation: 50°EL/DEP: 35°PROT/RET: 35°

Sternoclavicular Joint: Motions

Frontal planeElev/Dep

Sagittal planePost Rot

Horizontal planeProT/ReT

Ant/Post axisVertical axis

Acromioclavicular JointBony Structure

PoorDiarthrodial Nonaxial

Acromioclavicular Joint:Joint Capsule

Very weak

Acromioclavicular JointAcromioclavicular Ligament

Resists axial rotation & posterior motion

Acromioclavicular JointCoracoclavicular Ligament

Resists superior motion

Acromioclavicular JointAccessory Structures

Articular disc

Acromioclavicular Joint: Motion

Little relative motion at AC joint

UR/DR: 60°EL/DEP: 30°PROT/RET: 30-50°

Acromioclavicular Joint: Osteokinematics

Horizontal plane

adjustments

during scapulothoracic

protraction

Sagittal plane adjustment

during scapulothoracic

elevation

Clavicle

Acts a strut connecting upper extremity to thorax

Protects brachial plexus & vascular structures

Serves as attachment site for many shoulder muscles

Scapula

Scapular Plane

Scapulothoracic Joint

No osseous connection

SUBSCAP & SA

Glenohumeral Joint: Humerus

Retroversion angle: 30°

Glenohumeral Joint: Humerus

Inclination angle: 45°

Glenohumeral Joint: Glenoid Fossa

Inclination angle: 5° Retroversion angle: 7°

Glenohumeral Joint: Glenoid Fossa

Articular cartilage thicker on periphery

Shallow fossa 1/3 diameter of humeral head

Glenohumeral Joint: Bony Structure

Pure rotation Bony restraint poor Head 4-5X larger than

fossa Close-packed position

ABD with LR

Glenohumeral Joint: Joint Capsule

Inherently lax Surface area 2X

head Provides restraint for

ABD, ADD, LR, MR

Glenohumeral Joint:Superior GH Ligament

Resists inferior translation in rest or adducted arm

Well-developed in 50%

Glenohumeral Joint: Coracohumeral Ligament

Resists inferior translation in shoulders with less-developed SGH

Glenohumeral Joint:Middle GH Ligament

Great variability in proximal attachment & morphology

Absent in 30% Resists inferior

translation in ABD & ER

Restrains anterior translation (45° ABD)

Glenohumeral Joint:Inferior GH Ligament

3 components (A,P,Ax)

Resists inferior, anterior, & posterior translation

Glenohumeral Joint: Bursae

Subcoracoid Subacromial Subscapular

Glenohumeral Joint: Accessory Structures

50% of depth Increases tangential stability 20%

Labrum

Glenohumeral Joint: Intra-articular Pressure

Synovial fluid causes adhesion

Provides ~50% restraint

Coracoacromial Arch

Glenohumeral Joint: ROM

Flexion (167° W; 171° M) 30° in max LR

Extension (60°) Abduction (180°)

60° in max IR Hyperadduction (75°)

Glenohumeral Joint: ROM

Medial rotation (90°) Lateral rotation (90°)

Horizontal abduction (45°) Horizontal adduction (135°)

Total rotation 180°

Total ROT 90° in 90° ABD

Role of multiarticular muscles???

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






E. Common Injuries

Shoulder girdle has its own set of muscles.

Retraction of the Scapulothoracic Joint

Levator scapula

Protraction of the Scapulothoracic Joint

Pectoralis minor

Pathomechanics of a weak serratus anterior muscleDeltoid force causes scapula to downwardly rotate.

Unstable and cannot resist deltoid force

GH Flexion

Prime flexors: Anterior deltoid Pectoralis major: clavicular portion

Assistant flexors: Coracobrachialis Biceps brachii: short head

GH Extension

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

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

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

GH Medial Rotation

Subscapularis Latissimus dorsi Pectoralis major Teres major (with resistance)

Decreased activity with ABD

GH Lateral Rotation

Primary Infraspinatus

Assistant: Teres minor Posterior deltoid

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

Muscle Strength

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

Role of multiarticular muscles???






E. Common Injuries

Specific Functional Considerations

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

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

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

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

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

Movements in the Frontal PlaneGH Joint - Abduction

Shoulder Girdle: UR Totals

Upward rotation - 60° GH Abduction - 120°

2:1 (.66) ratio 1.25:1 after 30° 0.5-0.75 across

individuals

ABD

30°

ABD - 30°

UR - 40°

ABD - 60°

UR - 20°

Movements in the Frontal PlaneGH Joint - Adduction

Shoulder Girdle: DR

Fig 5.17

Movements in the Sagittal PlaneGH Joint – Flexion & Extension

Shoulder Girdle: UR ELEV (>90°) PROT ( to 90°) RET (>90°)

Fig 5.18

Movements in the Sagittal PlaneGH Joint - Hyperextension Shoulder Girdle: Upward tilt of scapula

Fig 5.20

Movements in the Transverse PlaneGH Joint – MR & LR

Fig 5.22a

Spinal Contribution to GH Motion

Movements in the Transverse PlaneGH HAdd & HAbd

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

Subscapularis

Teres minorSupraspinatus

Infraspinatus

Function of Rotator Cuff

Large external muscles (e.g., lats, delts) create shear forces

Rotator cuff provides Joint compression Tangential restraint

(Ant, Post, Sup)

Destabilizing Action of Deltoid

Deltoid produces superior shear force at GH joint.

Subscapularis

Resists superior shear

Produces simultaneous internal rotation

Infraspinatus & Teres Minor

Resists superior shear

Neutralizes SUBSCAP internal rotation

Supraspinatus

Summary of Active Arthrokinematics Resisting Shear

Destabilizing Action of Latissimus Dorsi

LD pulls humerus INF

SSP resists INF force

INF & SUBSCAP create compressive force






E. Common Injuries

Common Shoulder Injuries

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

Impingement

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

Impingement: Roll-Slide Kinematics

“Roll” created by abduction not countered with “Slide” action

During ABD SSP tendon pushed into

acromion process & CA ligament

During ROT SSP tendon dragged along the

inferior surface of the acromion process

Wind-Up Phase

Kinesiological breakdown of overhand throwing

First Motion Maximum knee lift of leg

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


Stride

Lead leg begins to moveArms separate

Lead foot contacts the ground

• ER in ABD position; ER 150-180°• ECC action of SUBSCAP (decelerates ER

humerus)• RC stabilization


Arm Cocking

Lead foot contact Maximum shoulder external rotation

• Concentric IR (PMJR & LD ) • IR velocity (> 1000 °/s)• RC stabilization


Arm Acceleration

Maximum shoulder ER Ball release

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


Arm Deceleration

Ball release Maximum shoulder IR

• Decelerating IR• ECC action of TMin• RC stabilization


Follow Through

Maximum shoulder IR Ends in balanced position

Rotator Cuff Injuries: Solution

Alter technique during problem phases to avoid impingement Arm cocking Arm acceleration

Strengthen rotator cuff Surgical repair

Video techniques

Intrinsic Risk Factors

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

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.

Swimming

Mechanism: ABD + IR

Solutions: Lead with hand to ↓ IR Increase body roll to ↓ ABD

Supraspinatus Tear

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

Biceps Tendon Tear

Subscapular Neuropathy

Denervation of INF with ↓ strength GH ER

Mechanism: Repeated stretching of nerve

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)

Glenohumeral Injuries

Most common dislocation in anterior (anterior-inferior 95%)

most commonly dislocated when abducted and ER overhead

recurrence rate 33-50% (66-90% <20 yrs)

the shoulder complex. a.general structure & function b.structure & function of specific...

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