1Shoulder BiomechanicsLecture originally developed by Bryan Morrison, Ph.D. candidateArizona State UniversityFall 20002Outline Anatomy Biomechanics Problems3Shoulder 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)4Bones Humerus Clavicle Scapula Ribs5Humerus Articular Surface (33-55 mm) ____° from Shaft 32° Retroverted (Rotated ________)6Scapula 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)7Joints Glenohumeral  ______________ Acromioclavicular ______________ Last 3 Collectively Called Shoulder Girdle8Ligaments Glenohumeral  ______________ Superior, Middle, Inferior Glenohumeral  Acromioclavicular Conoid Trapezoid  Sternoclavicular ____________ Sternoclavicular Costoclavicular9Glenohumeral Joint Movement Flexion (___)/Extension (___) (Sagittal) Abduction(180)/Adduction(-75) (__________) Internal(___)/External Rotation(-90) (_____________)  Horizontal Abduction(___) /Adduction(-45) (Flexion/Extension) Primarily Rotational (___)10Elevation Planes Frontal Sagittal Scapular ___________ Advantageous11Shoulder Girdle Movement Upward/ Downward Rotation (______) Protraction/Retraction (________/________)(Transverse)  Upward/ Downward Tilt (________) Elevation/Depression (_________)12Elevation and Tilting13Protraction and Rotation14Large Range of Motion Motion Spread Through All articulations (Synchronous and Simultaneous) Glenoid Fossa Mobility (Scapular Motion) Optimal Portion of Length-Tension Curve Minimal Constraints15Joint Movement Patterns Many Ways a Joint Could Move Glenohumeral Joint Initial movement __° Flexion __° Abduction Spine Reasons for Different Opinions Measurement Techniques Planes Anatomic Variations16Opinions on MovementDoody (Scapular Plane)Saha (Scapular Plane)Poppen(Scapular Plane)Freedman(Scapular Plane)2/1 after 60°/30° - 120°/60° Total MotionInnman (1944) Flexion/AbductionGlenohumeral/ Shoulder Girdle17Codman’s Paradox Flex Horizontally Abduct Adduct Rotation with out Rotation18Joint 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 Osteotomy19Glenohumeral Muscles Deltoid (A, Middle, P) Rotator Cuff ___________ ___________ ___________ ___________ Teres Major Coracobrachialis20Scapulothoracic Muscles Trapezius Rhomboids Levator Scapulae ______________ Pectoralis Minor21Multiple Joint Muscles Pectoralis Major Latissimus Dorsi Biceps Brachii Triceps (_________)22Muscular Motions GlenohumeralFlex, Horiz. AddCoracobrachialisExtend, Int. Rotation, Add, Horiz. AbdTeres MajorInt. RotationSubscapularisTeres MinorInfraspinatusAbduct, Int. RotationSupraspinatusExtend, Add <90, Abd >90, Ext. Rotation, Horiz. AbdPos. DeltoidMiddle DeltoidFlex, Add <90, Abd >90, ________ Rotation, Horiz. ________Ant. Deltoid23Muscular Motions ScapulothoracicAbd, Inf-Upward Rotation, Depression, Sup-Downward Rotation, ElevationPectoralis MinorSerratus AnteriorLevator ScapulaeAdd, Downward Rotation, ElevationTrapezius24Muscular Motions of Multiple Joint MusclesBiceps BrachiiExtend, Int. Rotation, Add, Horiz. AbdPectoralis Major25Outline Anatomy Biomechanics Problems26Reasons for Biomechanical Analysis Rehabilitation Therapy Loads Repair Strengths Injury Motions That Transfer Higher Loads Injury Mechanisms Dislocation Prosthetic Design Stress (Load) Analysis27Injuries Broken Bones Clavicle Scapula Humerus Impingement ____________ Biceps Tendon Bursitis Dislocation Subluxation Tendon Ruptures __________ Biceps28Impingement Compartment Inflammation Increase in Pressure Feedback29Dislocation ______________ Most Common Superior Subluxation Difficult Acromion Coracohumeral Ligament Coracoacromial Ligament Rotator Cuff Provides Dynamic Stability Protects Inferior, Anterior, Posterior Displacements30Rotator Cuff Repair Suture Anchor Bioscrew Tack Cyclic Loads to ___N (2/3 Max Contraction Force) 45°31Testing•Suture Anchor Good Overall•Tack Best for Good Cuff-Weak Bone•Screw Best for Strong Bone-Any Cuff32Joint Replacement Loosening Cemented Uncemented Prostheses Design Stress Shielding33Troubles 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 Rotated34Multiple Motions of Single Muscle Anterior Deltoid - Muscle Flexion/Internal Rotation Teres Major - Muscle Extension/Internal Rotation .35Coupling - 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-Infraspinatus36Muscle Pair Ratios Flex:Extension ( ) Abd:Add ( ) Internal:External ( ) Adduction-Extension-Flexion-Abduction-Internal Rotation-External Rotation37Forces 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)38Forces at the Shoulder (Poppen et al., 1978) Abduction in the Frontal Plane Elevation Bent Arm Reduces Shoulder Force by%39Shoulder 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 Fatigue40Simplified Joint Force 1 Muscle