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Chapter 7: The Biomechanics of the Human Upper Extremity Basic Biomechanics, 4 th edition Susan J. Hall Presentation Created by TK Koesterer, Ph.D., ATC.

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Presentation on theme: "Chapter 7: The Biomechanics of the Human Upper Extremity Basic Biomechanics, 4 th edition Susan J. Hall Presentation Created by TK Koesterer, Ph.D., ATC."— Presentation transcript:

1 Chapter 7: The Biomechanics of the Human Upper Extremity Basic Biomechanics, 4 th edition Susan J. Hall Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University

2 Objectives Explain how anatomical structure affects movement capabilities on upper extremity articulations. Identify factors influencing the relative mobility and stability of upper extremity movements Identify muscles that are active during specific upper extremity movements Describe the biomechanical contributions to common injuries of the upper extremity.

3 Structure of the Shoulder Most complex joint in body Separate articulations: –Sternoclavicular Joint –Acromioclavicular Joint –Coracoclavicular Joint –Glenohumeral Joint –Scapulothoracic Joint –Also: Bursae

4 Sternoclavicular Joint Provides major axis of rotation for movement of clavicle and scapula Freely permitted frontal and transverse plane motion. Allows some forward and backward sagittal plane rotation. Rotation

5 Acromioclavicular Joint Irregular diarthrodial joint between the acromion process of the scapula and the distal clavicle. –allows limited motions in all three planes. Rotation occurs during arm elevation Close-packed position with humerus abducted to 90 degrees

6 Coracoclavicular Joint A syndesmosis with coracoid process of scapula –bound to the inferior clavicle by the coracoclavicular ligament. Permits little movement

7 Glenohumeral Joint Most freely moving joint in human body Glenoid Labrum composed of: –Joint capsule –Tendon of long head of biceps brachii –Glenohumeral ligaments Rotator Cuff Rotator Cuff Muscles Most stable in close-packed position, when the humerus is abducted and laterally rotated.

8 Scapulothoracic Joint Region between the anterior scapula and thoracic wall. Functions of muscles attaching to scapula: –Contract to stabilize shoulder region –Facilitate movements of the upper extremity through appropriate positioning of the glenohumeral joint.

9 Bursae Small fibrous sacs that secrete synovial fluid internally to lessen friction between soft tissues around joints. Shoulder contains: –Subcoracoid bursa –Subscapularis bursa –Subacromial bursa

10 Movements of the Shoulder Complex Humerus movement usually involves some movement at all three shoulder joints –Positioning further facilitated by motions of spine –Scapulohumeral Rhythm

11 Movements of the Shoulder Complex Muscles of the Scapula Muscles of the Glenohumeral Joint –Flexion –Extension –Abduction –Adduction Medial and Lateral Rotation of the Humerus Horizontal Adduction and Abduction at the Glenohumeral Joint

12 Muscles of the Scapula Functions: –1) stabilize the scapula when shoulder complex is loaded –2) move and position the scapula to facilitate movement at glenohumeral joint Are: –Levator scapula, rhomboids, serratus anterior, pectoralis minor, subclavius, and four parts to trapezius.

13 Muscles of Glenohumeral Joint Many muscles involved, some contribute more than others. Large ROM can complicate tension development with orientation of humerus. Tension development in one shoulder muscle is frequently accompanied by development of tension in an antagonist to prevent dislocation of the humeral head.

14 Flexion at Glenohumeral Joint Prime flexors: –Anterior deltoid –Pectoralis major: clavicular portion Assistant flexors: –Coracobrachialis –Biceps brachii: short head

15 Extension at Glenohumeral Joint Gravitational force is primary mover when shoulder extension isnt resisted. –Control by eccentric contraction of flexors With resistance there is contraction of muscles posterior to the glenohumeral joint Assisted by: –Posterior deltoid –Biceps brachii: long head

16 Abduction at Glenohumeral Joint Major abductors of humerus: –Supraspinatus Initiates abduction Active for first 110 degrees of abduction –Middle deltoid Active degrees of abduction Superior dislocating component neutralized by infraspinatus, subscapularis, and teres minor

17 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

18 Medial and Lateral Rotation of Humerus Due to action of: –Subscapularis Has greatest mechanical advantage for medial rotation –Teres major Assisted by: –Primarily: pectoralis major –Also: anterior deltoid, latissimus dorsi and short head of biceps brachii

19 Horizontal Adduction and Abduction at the Glenohumeral Joint 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

20 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

21 Common Shoulder Injuries Dislocations Rotator Cuff Damage –Impingement Theory Subscapular Neuropathy Rotational Injuries

22 Tears of labrum –Mostly in anterior-superior region Tears of rotator cuff muscles –Primarily of supraspinatus Tears of biceps brachii tendon Due to forceful rotational movements –Also: calcification of soft tissues, degenerative changes in articular surfaces, bursitis

23 Structure of the Elbow Humeroulnar Joint Humeroradial Joint Proximal Radioulnar Joint

24 Segments at the Elbow Flexion and Extension –Muscles crossing anterior side of elbow are the flexors: Brachialis, biceps brachii, brachioradialis –Muscles crossing posterior side of elbow are the extensors: Triceps, anconeus muscle

25 Segments at the Elbow Pronation and Supination –Involves rotation of radius around ulna –Articulations: Proximal and distal radioulnar joints (both pivot joints) Middle radioulnar joint (syndesmosis) Pronator quadratus Supinator

26 Loads on the Elbow Large loads generate by muscles that cross elbow during forceful pitching/throwing –Also in weight lifting, gymnastics Extensor moment arm shorter flexor moment arm –Tricep attachment to ulna closer to elbow joint center than those of the brachialis on ulna an biceps on radius Moment arm also varies with position of elbow

27 Common Injuries to Elbow Sprains Dislocations –nursemaids elbow or pulled elbow Overuse Injuries –Lateral Epicondylitis = tennis elbow –Medial Epicondylitis = Little Leaguers Elbow Elbow injuries are more chronic than acute

28 Structure of the Wrist Radiocarpal joint –Reinforced by: volar radiocarpal, dorsal radiocarpal, radial collateral and ulnar collateral ligaments Retinacula –Form protective passageways for tendons, nerves and blood vessel to pass through

29 Movements of the Wrist Sagittal and frontal plane movements Rotary motion Flexion Extension and Hyperextension Radial Deviation Ulnar Deviation

30 Joint Structure of the Hand Carpometacarpal (CM) Metacarpophalangeal (MP) Interphalangeal (IP)

31 Movements of the Hand CM Joints allow large ROM because similar to ball and socket joint –Digits 2-4 constrained by ligaments MP joints allow flexion, extension, abduction, adduction and circumduction for digits 2-5 IP joints allow flexion and extension Extrinsic Muscles Intrinsic Muscles

32 Common Injuries of the Wrist and Hand Sprains and strains fairly common, due to breaking a fall on hyperextended wrist Certain injuries characteristic of sport type –Metacarpal fractures and football –Ulnar collateral ligament and hockey –Wrist fracture and skate/snowboarding –Wrist in non-dominant hand for golfers Carpal Tunnel Syndrome

33 Summary Shoulder is the most complex joint in the human body. Movements of the shoulder girdle contribute to optimal positioning of the glenohumeral joint for different humeral movements. Humeroulnar articulation controls flexion and extension at the elbow Pronation and supination of forearm occur at proximal and distal radioulnar joints.

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