Biomechanics of

Human Upper

ExtremityPicture retrieved from http://catalog.nucleusinc.com/enlargeexhibit.php?ID=797

ENT 214 Biomechanics

Picture retrieved from

http://thestar.com.my/archives/2006/12/9/sports/Sazali.jpg

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http://en.wikipedia.org/wiki/Image:Human_arm_bones_diagram.svg

Sternum

Manubrium

Sternoclavicular jointAcromioclavicular jointCoracoclavicular jointGlenohumeral jointScapulothoracic joint

Structure of the Shoulder

Structure of the Shoulder

Sternoclavicular joint: modified ball and socket joint between the proximal clavicle and the manubrium of the sternum

Interclavicular ligament

Clavicle

Sternoclavicular ligament

Costoclavicular ligament

Sternum

Clavicle

Articular disk

Costal cartilage (1st rib)

Structure of the Shoulder

Acromioclavicular joint: irregular joint between the acromion process of the scapula and the distal clavicle

Coracoclavicular ligament

Coracoclavicular ligament

Anterior view Posterior view

Clavicle

Verterbal border

Acromioclavicular joint

Acromion process

Coracoacromial ligament

Coracoid process

Glenoid fossa

Axillary border

Inferior angle

Clavicle

Scapular spine

Vertebral border

Inferior angle

Structure of the Shoulder

Coracoclavicular joint: syndesmosis with the coracoid process of the scapula bound to the inferior clavicle by the coracoclavicular ligament

Coracoclavicular ligament

Coracoclavicular ligament

Anterior view Posterior view

Clavicle

Verterbal border

Acromioclavicular joint

Acromion process

Coracoacromial ligament

Coracoid process

Glenoid fossa

Axillary border

Inferior angle

Clavicle

Scapular spine

Vertebral border

Inferior angle

Structure of the Shoulder

Glenohumeral joint: ball and socket joint in which the head of the humerus articulates with the glenoid fossa of the scapula

Acromion process

Coracohumeral ligament

Long head of biceps

Humerus

Coracoid process

Articular capsule

Scapula

Structure of the Shoulder

What is the scapulothoracic joint?

articulation between the anterior scapula and the thoracic wall

Bursae

A small fluid-filled sac located between movable parts of the body especially at joints

Reduce friction between layers of collagenous tissue

Movements of the Shoulder Complex

scapulohumeral rhythm: a regular pattern of scapular rotation that accompanies and facilitates humeral abduction

First 30o humeral elevation, contribution of scapula only 1/5 of glenohumeral joint

Beyond 30o, scapula rotates 1o for every 2o of humerus movement

First 90o of arm elevation, clavicle elevated 35o to 45o of motion at sternoclavicular joint.

Movements of the Shoulder Complex

Movements of the Shoulder Complex

What muscles contribute to flexion at the glenohumeral joint?

anterior deltoid clavicular pectoralis major assisted by:

coracobrachialis short head of biceps brachii

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Movements of the Shoulder Complex

What muscles contribute to extension at the glenohumeral joint? sternal pectoralis major latissimus dorsi teres major assisted by:

long head of triceps brachii

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Movements of the Shoulder Complex

What muscles contribute to abduction at the glenohumeral joint?

middle deltoid supraspinatus

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Movements of the Shoulder Complex

What muscles contribute to adduction at the glenohumeral joint? latissimus dorsi teres major sternal pectoralis major assisted by:

short head of biceps brachii long head of triceps brachii

Movements of the Shoulder Complex

What muscles contribute to medial rotation of the humerus?

subscapularis teres major assisted by:

pectoralis major anterior deltoid latissimus dorsi short head of biceps brachii

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Movements of the Shoulder Complex

What muscles contribute to lateral rotation of the humerus?

• infraspinatus• teres minor• assisted by:

• posterior deltoid

Movements of the Shoulder Complex

What muscles contribute to horizontal adduction of the humerus?

• pectoralis major• anterior deltoid• coracobrachialis• assisted by:

• short head of biceps brachii

Movements of the Shoulder Complex

What muscles contribute to horizontal abduction of the humerus?

infraspinatus middle and posterior deltoid teres minor assisted by:

teres major latissimus dorsi

Torque at shoulder

Torque created by weight of arm is the product of arm weight and perpendicular distance between arm’s COG and the shoulder

Torque at shoulder

Sample Problem 1

If the weight of the arm is 33 N, moment arm for the total arm segment is 30 cm, moment arm for deltoid muscle (Fm) is 3 cm.

How much force must be supplied by deltoid to maintain the arm in this position?

What is the magnitude of the joint reaction force (R)?

wt

Common Injuries of Shoulder

Dislocation Rotator Cuff Damage

Rotator cuff - anatomical term given to the group of muscles and their tendons that act to stabilize the shoulder

Example – supraspinatus, infraspinatus, teres minor, subscapularis muscles

Rotational Damage

Humeroulnar Joint

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Structure of the Elbow

What is the humeroulnar joint? hinge joint in which the humeral trochlea articulates with the trochlear fossa of the ulna

considered to be the elbow joint

Structure of the Elbow

What is the humeroradial joint?

gliding joint in which the capitellum of the humerus articulates with the proximal end of the radius

Structure of the Elbow

What are the radioulnar joints?

the proximal and distal radioulnar joints are pivot joints

the middle radioulnar joint is a syndesmosis

Movements at the Elbow

What muscles contribute to flexion at the elbow?

brachialis

biceps brachii

brachioradialis

Movements at the Elbow

What muscles contribute to extension at the elbow?

triceps brachii

assisted by:

anconeus

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biceps

fore

force?

be

Common Injuries of Elbow

Sprains and dislocationEpicondylitis

Inflammation and sometimes microrupting of collagenous tissue at distal humerus

Wrist

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Structure of the Wrist

What are the radiocarpal joints? condyloid articulations between the radius and the three carpal bones

these joints comprise the wrist

Structure of the Wrist

What is the function of the retinacula at the wrist?

these fibrous bands of fascia form protective passageways through which tendons, nerves, and blood vessels pass

Movements at the Wrist

What muscles contribute to flexion at the wrist? flexor carpi radialis flexor carpi ulnaris palmaris longus assisted by:

flexor digitorum superficialis flexor digitorum profundus

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What muscles contribute to extension at the wrist? extensor carpi radialis longus extensor carpi radialis brevis extensor carpi ulnaris assisted by:

other wrist extensor muscles

Movements at the Wrist

F

I

N

G

E

RRetrieved fromhttp://upload.wikimedia.org/wikipedia/commons/f/f7/X-ray_boy_hand.jpg

Structure of the Hand Joints

What are the carpometacarpal joints?

the carpometacarpal joint of the thumb is a saddle joint

the other carpometacarpal joints are gliding joints

What are the intermetacarpal joints?

irregular joints between the metacarpals that share joint capsules with the carpometacarpal joints

Structure of the Hand Joints

What are the metacarpophalangeal joints?

condyloid joints between the rounded distal heads of the metacarpals and the concave proximal ends of the phalanges these joints form the knuckles of the hand

Structure of the Hand Joints

What are the interphalangeal joints?

the proximal and distal interphalangeal joints of the fingers and the single interphalangeal joint of the thumb are all hinge joints

Structure of the Hand Joints

Movements of the Hand

What motions are permitted at metacarpophalangeal joints 2-5?

flexion extension abduction adduction circumduction

Movements of the Hand

What muscles are responsible for motions of the hand?

there are nine extrinsic muscles with attachments both proximal and distal to the wrist there are ten intrinsic muscles with both attachments distal to the wrist

Common Injuries of Wrist & Hand

Fracture - boxers Injury - golfers Carpal tunnel syndrome

Passageway between carpal bone and flexor retinaculum

Symptom : pain, numbness along median nerve, clumsiness of finger function, atrophy of muscle

Summary

1. Shoulder – Structure– Movement and muscle involve– Common injuries

2. Elbow

3. Wrist

4. Hand

5. Force initiated and torque - calculation