Download - The Throwing Athlete · 2018. 4. 1. · The Throwing Athlete Biomechanics Function & Dysfunction R. Scott Cook, DO, FAOASM Director, St. Joseph Sports Medicine Fellowship Commonwealth

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The Throwing Athlete Biomechanics Function & Dysfunction

R. Scott Cook, DO, FAOASM Director, St. Joseph Sports Medicine Fellowship

Commonwealth Orthopaedic Associates

Presentation Goals

! Provide an understanding of normal Scapular Function and Motion. ! Discuss the importance of the Scapula within the kinetic chain of the

throwing athlete. ! Describe clinical examination techniques for evaluation of scapular

function. ! Define Scapular Dyskinesis and the role it plays in shoulder injury and

pathology.

Normal Scapular Function

! Scapular Osseous Components ! Body, Spine, Coracoid Process, Acromion Process, Glenoid,

Inferior Angle. ! Arise from several ossification centers with varies stages of

coalescence: –  Coracoid: 14-18yo –  Acromion: 19-20yo –  Inferior Angle: 18-20yo –  Glenoid Fossa: 20-25yo

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! Basic Anatomy: Scapula is enveloped by multiple muscular layers. – Anterior Scapular Muscle Attachments:

! Triceps ! Biceps (Short and Long Heads) ! Coracobrachialis ! Subscapularis ! Serratus Anterior ! Pectoralis Minor ! Omohyoid

Normal Scapular Function ! Basic Anatomy:

–  Posterior Scapular Muscle Attachments: ! Triceps ! Biceps (Long Head) ! Omohyoid ! Trapezis ! Supraspinatous ! Infraspinatous ! Teres Major ! Teres Minor ! Levator Scapulae ! Latissimus Dorsi ! Deltoid ! Rhomboideus Major and Minor


! Scapular Bursae: ! Infraserratus Bursa (Bursa Mucosa Serrata)

–  Lies between Serratus Anterior and Chest Wall –  Inflammed = Inferior Angle Pain

! Supraserratus Bursa (Bursa Mucosa Angulae Superioris

Scapulae) –  Lies between Subscapularis and Serratus Anterior –  Inflammed = Superior Angle Pain

! Scapulotrapezial Bursa –  Lies between Superomedial Scapula and Trapezius

–  Contains the Spinal Accessory Nerve.

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! Scapular Anatomic Positioning at Rest: ! Anteriorly Rotated (relative to trunk) approx 30° ! Medial Border Rotated

–  Inferior Pole diverged 3-5° from Spine

! Anteriorly Tilted 20° in sagittal plane


! Scapulothoracic Anatomy & Function: ! Scapular Postural Support

–  Levator Scapulae & Upper Trapezius

! Scapular Retraction –  Middle Trapezius & Rhomboids

! Scapular Protraction –  Serratus Anterior

! Upward Scapular Rotation –  Serratus Anterior & Trapezius

! Scapular Elevation –  Upper Trapezius & Levator Scapulae


! A. Scapular Posterior Tilting ! B. Scapular Superior Rotation ! C. Scapular External Rotation ! D. Clavicular Elevation ! E. Clavicular Protraction

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! Dynamic Anatomy: ! Humeral movement in relation to Glenoid. ! Glenohumeral Ligament and Labral static constraint on

Humeral Translation. ! Rotator Cuff dynamic constraint on Glenohumeral Motion.

The Scapula is intimately involved in each one of these functions.


! Glenohumeral Articulation ! Scapula must continually move to maintain instant center of

rotation. ! Proper glenoid alignment optimizes function of articulations

and rotator cuff to allow concentric GH-Motion. ! Scaulothoracic positioning determines position and inclination of

both Glenoid and Inferior Glenohumeral Ligament. ! Improper alignment can lead to GH Instability.


! Thoracic Wall Articulation ! Scapular Retraction (external rotation) facilitate cocking

position. ! Scapular Lateral Protraction (internal rotation) allows

acceleration. ! Scapular Anterior Thoracic Translation allows maintenance of

normal GH position and dissipation of deceleration forces.

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! Acromial Elevation ! Serratus Anterior activation results in traction related superior

acromial elevation. ! Occurs during cocking and acceleration phases of throwing,

and during arm elevation. ! Allows for reduction of impingement and coracoacromial arch

compression.


! Kinetic Chain ! Scapula serves as a link in Proximal-to-Distal sequencing of

Velocity, Energy, and Forces of shoulder function. –  Generation, Summation, Transference

–  Scapula serves as pivotal link of transference of large forces/high energy from lower body/core to the arm/hand. ! Also allows arm stabilization to absorb force loads through long-lever

dynamics to reduce injury.

Scapular Motion

! Normal Scapular Dynamics: ! Bilateral Posterior Tilting, External Rotation, & slight

Superior Translation during elevation of arm. ! Symmetrical motion patterns. ! No prominent medial or superior scapular borders.

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Scapular Dyskinesis

! Scapular Dyskinesis ! Alterations in STATIC scapular position and DYNAMIC

scapular motion resulting in scapular asymmetry in gross postural assessment and function movement.

Scapular Dyskinesis

! Scapular Dyskinesis: ! Affects normal Scapulohumeral Rhythm (SHR). ! May lead to articular and/or soft tissue shoulder dysfunction. ! May result in shoulder pathology and injury. ! May result from injury causing inhibition of scapular

stabilization.

Nonspecific Response: No specific pattern of dyskinesis is associated with a specific shoulder diagnosis.

Scapular Dyskinesis

! Contributing Factors ! Bony Posture & Injury

–  Increased Thoracic Kyphosis ! ↑ Scapular Protraction ! Acromial Depression

–  Clavicle Fractures –  AC Joint Injury

! Disrupt normal progression of scapular rotation

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Scapular Dyskinesis

! Contributing Factors ! Muscle Function Alteration

–  Nerve injury ! Long Thoracic Nerve → Serratus Anterior ! Spinal Accessory Nerve → Trapezius

–  Muscle Inhibition/Weakness ! Common in Glenohumeral Pathology ! Nonspecific response to shoulder pain

68% RC Abnormalities

94% Labral Tears 100% GH Instability

Scapular Dyskinesis

! Contributing Factors – Contracture/Inflexibility

! Pectoralis Minor/SH-Biceps ! Anterior Tilted Scapula

! GIRD –  “Wind-Up” Effect

! Glenoid and Scapula pulled in forward-inferior direction ! May result in ↑ protraction during arm-ADDucted position

Scapular Dyskinesis

! Associated Shoulder Pathology: ! Subacromial Impingement ! Glenohumeral Instability ! Glenoid Labral Injury ! Rotator Cuff Injury

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Assessing Scapular Dyskinesis

! Clinical Examination – Kinetic Chain Evaluation:

! Leg/Trunk Muscle Strength ! Lumbar Lordotic Posture ! Pelvic Alignment

! Iliac Rotations, SI Instability/Dysfunction

! Hip ROM ! Thoracic Alignment/Posture

! Thoracic Kyphosis, Scoliosis

! Cervical Posture ! Cervical Lordosis


! Clinical Examination –  Examine patient from behind with arms at rest at sides. –  Examine Scapular Motion as arms are elevated and

lowered within scapular plane. –  Examine Scapular Motion as arms are elevated and

lowered within the sagittal plane.

Types of Scapular Dyskinesis

! Type I ! Prominence of Inferior Medial Scapular Angle. ! Primarily abnormal rotation around a transverse axis. ! Results in excessive anterior scapular tilt.

! Type II ! Prominence of entire Medial Scapular Border. ! Results in abnormal rotation around a vertical axis. ! Associated with excessive scapular internal rotation.

! Type III ! Prominence of Superior Scapular Border. ! Results in excessive superior scapular translation.

! Type IV ! Normal, Symmetrical scapular motion.

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Assessing Scapular Dyskinesis ! Observational Clinical Assessment

! 4-Type Method versus Yes/No Method ! Easily available ! Wide variance of Inter-Rater Reliability

–  (4-Type) Sensitivity 10%-54%; Specificity 62%-94% –  (Yes/No) Sensitivity 74%-78%; Specificity 31%-38%

! Limited assessment of multiple-plane asymmetries

! 3D EM Kinematic Analysis ! Lab-based; limited availability ! Allows for multiple-plane assessment ! Detected asymmetry may not be clinically relevant

Uhl et al; Arthroscopy, 25(11); 2009


! Yes/No Method ! Improved Inter-Rater Agreement (79%)

–  Allows consideration beyond a single-plane of motion –  PPV = 74%

! Displays Sensitivity (76%) & Specificity (35%) similar to other clinical shoulder exam tests.

–  Clinical SLAP tests: Mean Sensitivity 57%; Specificity 41% –  Clinical Instability tests: Mean Sensitivity 71%; Specificity 38% –  Clinical Impingement tests: Mean Sensitivity 68%; Specificity 49%

Scapular Dyskinesis

! Prevalence of Scapular Asymmetry ! 71%-78% (3D Kinematics) of population at large ! Symptomatic vs. Asymptomatic

–  Additional Factors: ! Ligamentous Laxity, Muscle Imbalance, Side Dominance

! Plane of Assessment may determine clinical relevance –  Forward Flexion Motion Asymmetry increased in Symptomatic (54%)

versus Asymptomatic (14%) patients. ! Increased Serratus Anterior activity

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Effects of Scapular Dyskinesis

! Loss of Retraction/Protraction – Retraction Loss

! ↓ stable “Cocking” point or base for arm elevation. ! ↑ Impingement as scapula rotates inferior and anterior.

–  Protraction Loss ! ↑ deceleration forces in GH Joint. ! Functional Glenoid Anteversion.

–  ↑ shear stresses on anterior stabilizing structures. –  ↑ posterior impingement


! Loss of Superior Elevation – Decreased Acromial Elevation

! Predisposes Subacromial Impingement. ! Inhibition of Serratus Anterior and Lower Trapezius.


! Loss of Kinetic Chain Function – Disruption of transferal of lower extremity and core

forces to the upper extremity. ! ↓ Strength and Energy Use ! ↓ Acceleration Velocity

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References ! Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: Spectrum of pathology. Part I: Pathoanatomy

and biomechanics. Arthroscopy 2003;19:404-420. ! Fleisig et al. Biomechanics of overhand throwing with implications for injuries. Sports Med 1996;21:421-437. ! Gaunche et al. The synergistic action of the capsule and the shoulder muscles. Am J Sports Med 1995;23:301-306. ! Glousman et al. Dynamic EMG analysis of the throwing shoulder with glenohumeral instability. J Bone Joint Surg Am

1988;70:220-226. ! Kibler WB, McMullen J. Scapular dyskinesis and its relation to shoulder pain. J Am Acad Orthop Surg 2003;11:142-151. ! Kibler WB. Evaluation and diagnosis of scapulothoracic problems in the athlete. Sports Med and Arthro Rev

2000;8:192-202. ! Kibler WB. Role of the scapula in the overhead throwing motion. Contmp Orthop 1991;22:525-532. ! Kibler WB. The role of the scapula in athletic shoulder function. Am J Sports Med 1998;26:325-337. ! Kibler et al. Qualitative clinical evaluation of scapular dysfunction. A reliability study. J Shoulder Elbow Surg

2002;11:550-556. ! Laudner et al. Scapular dysfunction in throwers with pathologic internal impingement. J Orthop Sports Phys Ther

2006;36:485-494. ! McQuade KJ, Dawson J, Smidt GL. Scapulothoracic muscle fatigue associated with alterations in scapulohumeral

rhythm kinematics during maximum resistive shoulder elevation. J Orthop Sports Phys Ther 1998;28:74-80. ! Myers JB, et al. Glenohumeral range of motion deficits and posterior shoulder tightness in throwers with pathologic

internal impingement. Am J Sports Med 2006;34:385-391. ! Oyama et al. Asymmetric resting scapular posture in healthy overhead athletes. J Athl Train 2008;43:565-570. ! Uhl et al. Evaluation of clinical assessment methods for scapular dyskinesis. Arthroscopy 2009;25:1240-1248.