Presentation on theme: "Chapter 7: The Biomechanics of the Human Upper Extremity"— Presentation transcript:
1 Chapter 7: The Biomechanics of the Human Upper Extremity Basic Biomechanics, 4th editionSusan J. HallPresentation Created byTK Koesterer, Ph.D., ATCHumboldt State University
2 ObjectivesExplain how anatomical structure affects movement capabilities on upper extremity articulations.Identify factors influencing the relative mobility and stability of upper extremity movementsIdentify muscles that are active during specific upper extremity movementsDescribe the biomechanical contributions to common injuries of the upper extremity.
3 Structure of the Shoulder Most complex joint in bodySeparate articulations:Sternoclavicular JointAcromioclavicular JointCoracoclavicular JointGlenohumeral JointScapulothoracic JointAlso: Bursae
4 Sternoclavicular Joint Provides major axis of rotation for movement of clavicle and scapulaFreely 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 elevationClose-packed position with humerus abducted to 90 degrees
6 Coracoclavicular Joint A syndesmosis with coracoid process of scapulabound 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 capsuleTendon of long head of biceps brachiiGlenohumeral ligamentsRotator CuffRotator Cuff MusclesMost 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 regionFacilitate movements of the upper extremity through appropriate positioning of the glenohumeral joint.
9 BursaeSmall fibrous sacs that secrete synovial fluid internally to lessen friction between soft tissues around joints.Shoulder contains:Subcoracoid bursaSubscapularis bursaSubacromial bursa
10 Movements of the Shoulder Complex Humerus movement usually involves some movement at all three shoulder jointsPositioning further facilitated by motions of spineScapulohumeral Rhythm
11 Movements of the Shoulder Complex Muscles of the ScapulaMuscles of the Glenohumeral JointFlexionExtensionAbductionAdductionMedial and Lateral Rotation of the HumerusHorizontal Adduction and Abduction at the Glenohumeral Joint
12 Muscles of the Scapula Functions: 1) stabilize the scapula when shoulder complex is loaded2) move and position the scapula to facilitate movement at glenohumeral jointAre: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 deltoidPectoralis major: clavicular portionAssistant flexors:CoracobrachialisBiceps brachii: short head
15 Extension at Glenohumeral Joint Gravitational force is primary mover when shoulder extension isn’t resisted.Control by eccentric contraction of flexorsWith resistance there is contraction of muscles posterior to the glenohumeral jointAssisted by:Posterior deltoidBiceps brachii: long head
16 Abduction at Glenohumeral Joint Major abductors of humerus:SupraspinatusInitiates abductionActive for first 110 degrees of abductionMiddle deltoidActive degrees of abductionSuperior dislocating component neutralized by infraspinatus, subscapularis, and teres minor
17 Adduction of Glenohumeral Joint Primary adductors:Latissimus dorsiTeres majorSternocostal pectoralisMinor assistance:Biceps brachii: short headTriceps brachii: long headAbove 90 degrees- coracobrachialis and subscapularis
18 Medial and Lateral Rotation of Humerus Due to action of:SubscapularisHas greatest mechanical advantage for medial rotationTeres majorAssisted by:Primarily: pectoralis majorAlso: 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, coracobrachialisAssisted by short head of biceps brachiPosterior to joint:Middle and posterior deltoid, infraspinatus, teres minorAssisted 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 DislocationsRotator Cuff DamageImpingement TheorySubscapular NeuropathyRotational Injuries
22 Rotational Injuries Tears of labrum Mostly in anterior-superior region Tears of rotator cuff musclesPrimarily of supraspinatusTears of biceps brachii tendonDue to forceful rotational movementsAlso: 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, brachioradialisMuscles crossing posterior side of elbow are the extensors:Triceps, anconeus muscle
25 Segments at the Elbow Pronation and Supination Involves rotation of radius around ulnaArticulations:Proximal and distal radioulnar joints (both pivot joints)Middle radioulnar joint (syndesmosis)Pronator quadratusSupinator
26 Loads on the ElbowLarge loads generate by muscles that cross elbow during forceful pitching/throwingAlso in weight lifting, gymnasticsExtensor moment arm shorter flexor moment armTricep attachment to ulna closer to elbow joint center than those of the brachialis on ulna an biceps on radiusMoment arm also varies with position of elbow
27 Common Injuries to Elbow SprainsDislocations“nursemaid’s elbow” or “pulled elbow”Overuse InjuriesLateral Epicondylitis = “tennis elbow”Medial Epicondylitis = “Little Leaguer’s 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 ligamentsRetinaculaForm protective passageways for tendons, nerves and blood vessel to pass through
29 Movements of the Wrist Sagittal and frontal plane movements Rotary motionFlexionExtension and HyperextensionRadial DeviationUlnar Deviation
30 Joint Structure of the Hand Carpometacarpal (CM)Metacarpophalangeal (MP)Interphalangeal (IP)
31 Movements of the HandCM Joints allow large ROM because similar to ball and socket jointDigits 2-4 constrained by ligamentsMP joints allow flexion, extension, abduction, adduction and circumduction for digits 2-5IP joints allow flexion and extensionExtrinsic MusclesIntrinsic Muscles
32 Common Injuries of the Wrist and Hand Sprains and strains fairly common, due to breaking a fall on hyperextended wristCertain injuries characteristic of sport typeMetacarpal fractures and footballUlnar collateral ligament and hockeyWrist fracture and skate/snowboardingWrist in non-dominant hand for golfersCarpal 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 elbowPronation and supination of forearm occur at proximal and distal radioulnar joints.