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- 1. 1 Shoulder Biomechanics Lecture originally developed by Bryan Morrison, Ph.D. candidate Arizona State University Fall 2000
- 2. 2 Outline „ Anatomy „ Biomechanics „ Problems
- 3. 3 Shoulder Complex „ Greatest ____________ „ Greatest Predisposition for Dislocation „ Little _____ Stability (Mainly Ligaments) „ Range of Motion Starts at _____° or Greater in all Planes and Decreases with Age (activity slows this process)
- 4. 4 Bones „ Humerus „ Clavicle „ Scapula „ Ribs
- 5. 5 Humerus „ Articular Surface (33-55 mm) „ ____° from Shaft „ 32° Retroverted (Rotated ________)
- 6. 6 Scapula „ Glenoid Fossa „ 41 by 25 mm „ Pear Shaped „ _____ Degree Tilt (Posterior)(Retrotilted) „ Glenoid Labrum „ Joint Capsule „ Glenohumeral Ligaments „ Long Head of the Biceps Tendon „ Minimal ___________ Contact (Large Range of Motion)
- 7. 7 Joints „ Glenohumeral „ ______________ „ Acromioclavicular „ ______________ „ Last 3 Collectively Called Shoulder Girdle
- 8. 8 Ligaments „ Glenohumeral „ ______________ „ Superior, Middle, Inferior Glenohumeral „ Acromioclavicular „ Conoid „ Trapezoid „ Sternoclavicular „ ____________ „ Sternoclavicular „ Costoclavicular
- 9. 9 Glenohumeral Joint Movement „ Flexion (___)/Extension (___) (Sagittal) „ Abduction(180)/Adduction (-75) (__________) „ Internal(___)/External Rotation(-90) (_____________) „ Horizontal Abduction(___) /Adduction(-45) (Flexion/Extension) „ Primarily Rotational (___)
- 10. 10 Elevation Planes „ Frontal „ Sagittal „ Scapular „ ___________ Advantageous
- 11. 11 Shoulder Girdle Movement „ Upward/ Downward Rotation (______) „ Protraction/Retraction (________/________)(Transverse) „ Upward/ Downward Tilt (________) „ Elevation/Depression (_________)
- 14. 14 Large Range of Motion „ Motion Spread Through All articulations (Synchronous and Simultaneous) „ Glenoid Fossa Mobility (Scapular Motion) „ Optimal Portion of Length-Tension Curve „ Minimal Constraints
- 15. 15 Joint Movement Patterns „ Many Ways a Joint Could Move „ Glenohumeral Joint Initial movement „ __° Flexion „ __° Abduction „ Spine „ Reasons for Different Opinions „ Measurement Techniques „ Planes „ Anatomic Variations
- 16. 16 Opinions on Movement Doody (Scapular Plane) Saha (Scapular Plane) Poppen (Scapular Plane) Freedman (Scapular Plane) 2/1 after 60°/30° - 120°/60° Total Motion Innman (1944) Flexion/Abduction Glenohumeral/ Shoulder Girdle
- 17. 17 Codman’s Paradox „ Flex „ Horizontally Abduct „ Adduct „ Rotation with out Rotation
- 18. 18 Joint Stability „ Glenoid Fossa „ >___% Longitudinal Length „ >___% Transverse Length „ _________ Tilt of Glenoid Fossa „ Humeral Head Retroversion „ Intact Capsule and Glenoid Labrum „ ____________ Pressure „ Muscular Function of the Rotator Cuff „ Subscapularis „ Supraspinatus „ Infraspinatus „ Upper Teres Minor •Glenoid Osteotomy
- 19. 19 Glenohumeral Muscles „ Deltoid (A, Middle, P) „ Rotator Cuff „ ___________ „ ___________ „ ___________ „ ___________ „ Teres Major „ Coracobrachialis
- 20. 20 Scapulothoracic Muscles „ Trapezius „ Rhomboids „ Levator Scapulae „ ______________ „ Pectoralis Minor
- 21. 21 Multiple Joint Muscles „ Pectoralis Major „ Latissimus Dorsi „ Biceps Brachii „ Triceps (_________)
- 22. 22 Muscular Motions Glenohumeral Flex, Horiz. Add Coracobrachialis Extend, Int. Rotation, Add, Horiz. Abd Teres Major Int. Rotation Subscapularis Teres Minor Infraspinatus Abduct, Int. Rotation Supraspinatus Extend, Add <90, Abd >90, Ext. Rotation, Horiz. Abd Pos. Deltoid Middle Deltoid Flex, Add <90, Abd >90, ________ Rotation, Horiz. ________ Ant. Deltoid
- 23. 23 Muscular Motions Scapulothoracic Abd, Inf-Upward Rotation, Depression, Sup-Downward Rotation, Elevation Pectoralis Minor Serratus Anterior Levator Scapulae Add, Downward Rotation, Elevation Trapezius
- 24. 24 Muscular Motions of Multiple Joint Muscles Biceps Brachii Extend, Int. Rotation, Add, Horiz. Abd Pectoralis Major
- 25. 25 Outline „ Anatomy „ Biomechanics „ Problems
- 26. 26 Reasons for Biomechanical Analysis „ Rehabilitation „ Therapy Loads „ Repair Strengths „ Injury „ Motions That Transfer Higher Loads „ Injury Mechanisms „ Dislocation „ Prosthetic Design „ Stress (Load) Analysis
- 27. 27 Injuries „ Broken Bones „ Clavicle „ Scapula „ Humerus „ Impingement „ ____________ „ Biceps Tendon „ Bursitis „ Dislocation „ Subluxation „ Tendon Ruptures „ __________ „ Biceps
- 28. 28 Impingement „ Compartment „ Inflammation „ Increase in Pressure „ Feedback
- 29. 29 Dislocation „ ______________ Most Common „ Superior Subluxation Difficult „ Acromion „ Coracohumeral Ligament „ Coracoacromial Ligament „ Rotator Cuff „ Provides Dynamic Stability „ Protects Inferior, Anterior, Posterior Displacements
- 30. 30 Rotator Cuff Repair „ Suture Anchor „ Bioscrew „ Tack „ Cyclic Loads to ___N (2/3 Max Contraction Force) „ 45°
- 31. 31 Testing •Suture Anchor Good Overall •Tack Best for Good Cuff-Weak Bone •Screw Best for Strong Bone-Any Cuff
- 32. 32 Joint Replacement „ Loosening „ Cemented „ Uncemented „ Prostheses Design „ Stress Shielding
- 33. 33 Troubles with Biomechanical Analysis „ Mobility „ High Number of Degrees of Freedom „ Muscles „ Large Number of Muscles Contributing „ Different Contributions „ . „ . „ Angle of Elevation „ Multiple Movements „ Arm Position (example: Biceps) „ Abductor while humerus is Externally Rotated
- 34. 34 Multiple Motions of Single Muscle „ Anterior Deltoid - Muscle Flexion/Internal Rotation „ Teres Major - Muscle Extension/Internal Rotation „ .
- 35. 35 Coupling - Forces Acting in Different Directions to Produce the Same Movement „ Downward Rotation „ Rhomboids-Pectoralis Minor-Serratus Anterior (Superior) „ Upward Rotation (figure) „ Elevation (Frontal) „ A. Deltoid-Teres Minor-Infraspinatus
- 36. 36 Muscle Pair Ratios „ Flex:Extension ( ) „ Abd:Add ( ) „ Internal:External ( ) „ Adduction-Extension-Flexion-Abduction- Internal Rotation-External Rotation
- 37. 37 Forces at the Shoulder (Innman et al., 1944) „ 90° Abduction „ Deltoid Extremity Weight (70% BW) „ GH Joint EW (90% BW) „ Rotator Cuff EW (85% BW) „ Load Bearing (Approximately 1BW)
- 38. 38 Forces at the Shoulder (Poppen et al., 1978) „ Abduction in the Frontal Plane Elevation „ Bent Arm Reduces Shoulder Force by %
- 39. 39 Shoulder Dynamics „ Fatigue and Injury (Working with Arm Elevated) „ Supraspinatus „ Trapezius „ Supraspinatus Tendonitis „ Neck Pain (Trapezius Fatigue) „ Less Fatigue (Herberts, 1980) „ A. Deltoid (45° and 90°) „ Supraspinatus (45°) „ Trapezius (45°) „ had Highest Fatigue
- 40. 40 Simplified Joint Force „ 1 Muscle „ Segment Weight „ Vector Addition
- 41. 41 Joint Force and Stability A B
- 42. 42 Moment (Hinrichs, 1981) „ Reference Line from Anthropometric Data „ Average Limb Weight ( BW) „ Average Center of Mass Distance „ F*d=Moment
- 43. 43 Outline „ Anatomy „ Biomechanics „ Problems
- 44. 44 Problem #1 (1-D) „ ΣM=0
- 45. 45 Problem #2 (2-D) „ ΣFx=0 „ ΣFy=0 „ ΣM=0
- 46. 46 Problem #3 (3-D) „ ΣFx=0 „ ΣFy=0 „ ΣFz=0 „ ΣM=0