Throwing Injuries of the Shoulder and Elbow

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Throwing Injuries of the Shoulder and Elbow

• Timothy G. Sanders, MD
• Director of Education and Research
• National Musculoskeletal Imaging
• Weston, Florida

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Biomechanics of Throwing
Shoulder
-Four Joints
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Biomechanics of Throwing
Shoulder
-Four Joints -Ligaments
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Biomechanics of Throwing
Shoulder
-Four Joints -Ligaments -Muscles
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Biomechanics of Throwing
Shoulder
-Four Joints -Ligaments -Muscles -Design
maximizes 3-D motion -Excellent Mobility but
prone to Instability
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Biomechanics of Throwing
Elbow
-Complex Joint
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Biomechanics of Throwing
Elbow
-Complex Joint -Flexion/Extension
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Biomechanics of Throwing
Elbow
-Complex Joint -Flexion/Extension -Supination/Pron
ation
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Throwing is the Prototypical Overhead Activity
-Throwing related injuries -Overuse -Repetitive
motion -Extremes of motion -Rotational
forces -Excessive tensile forces
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Throwing is the Prototypical Overhead Activity
-Throwing related injuries -Overuse -Repetitive
motion -Extremes of motion -Rotational
forces -Excessive tensile forces -Biomechanics
of throwing
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Throwing is the Prototypical Overhead Activity
-Throwing related injuries -Overuse -Repetitive
motion -Extremes of motion -Rotational
forces -Excessive tensile forces -Biomechanics
of throwing -Normal anatomy
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Throwing is the Prototypical Overhead Activity
-Throwing related injuries -Overuse -Repetitive
motion -Extremes of motion -Rotational
forces -Excessive tensile forces -Biomechanics
of throwing -Normal anatomy -Patterns of injury
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Mechanics of Throwing
-Windup Phase
-Period between the initiation of motion until
the ball is removed from the glove -Injury during
this phase is rare
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Mechanics of Throwing
-Windup Phase -Early Cocking Phase
-Period between when the ball leaves the glove
and when the arm reaches maximum
abduction/external rotation -Injuries rare during
early cocking phase
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Mechanics of Throwing
-Windup Phase -Late Cocking Phase
-Period at which maximum abduction and external
rotation of the arm occurs just prior to the
start of forward motion of the ball -Injuries
common during late cocking phase
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Mechanics of Throwing
-Windup Phase -Early/Late Cocking
Phase -Acceleration Phase
-Period between onset of forward motion until the
ball is released from the hand -Injury commonly
occurs during this phase
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Mechanics of Throwing
-Windup Phase -Early/Late Cocking
Phase -Acceleration Phase -Deceleration Phase
-Period between release of the ball until the
upper limb motion induced by the acceleration
phase ceases -Most violent phase of
throwing -Injury common during this phase
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Mechanics of Throwing
-Windup Phase -Early/Late Cocking
Phase -Acceleration Phase -Deceleration
Phase -Follow Through Phase
-Period during which deceleration of the body
takes place -Injury during this phase is rare
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Shoulder Stabilizers
-GH Joint inherently unstable -Static and active
stabilizers -At rest -Negative intra-articular
pressure
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Shoulder Stabilizers
-Mid-range activities -Muscles of rotator cuff
dominate stabilizer -Injury -Chronic repetitive
microtrauma -Acute macrotrauma -Primary or
secondary impingement
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Shoulder Stabilizers
-At extremes -GH ligaments and capsule
predominates -Injury -Repetitive
microtrauma -Capsular stretching -GH ligament
disruption
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Rotator Cuff Extrinsic Impingement
Primarily throwing athletes over 35 y.o.
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Cuff Injuries Extrinsic Impingement
Acromion
Clavicle
Clavicle
Acromion
C-A Ligament
C-A Ligament
Coracoid
Coracoid
-Occurs in the late-cocking/ early acceleration
phase -Certain anatomic configurations increase
risk for extrinsic impingement -Cuff pathology
usually located in anterior supraspinatus tendon
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Acromial Types
Type I
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Acromial Types
Type II
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Acromial Types
Type III
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Acromial Types
Type IV
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Acromial Down Sloping
Anterior Down Sloping Evaluated on Sagittal Images
Axis of Acromion
Normal Axis of Acromion
Anterior Down Sloping
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Acromial Down Sloping
Lateral Down Sloping Evaluated on Coronal Images
Axis of Acromion
Normal Axis of Acromion
Lateral Down Sloping
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Acromial Osteophyte
Os Acromiale
-Spur
-If unstable can impinge on RC during contraction
of Deltoid -Deltoid/SST contract to abduct arm
during early-cocking
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Acromioclavicular Joint
-AC degenerative change, capsular
hypertrophy -Cuff less rigidly confined
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Coracoacromial Ligament
-Normal Ligament lt3 mm
-Thick Ligament can Impinge on Anterior Rotator
Cuff
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Coracoid Impingement Syndrome
-Narrowed (lt 7 mm) C-H Distance Can Impinge on
Subscapularis
-Normal Coracohumeral Distance is gt 9 mm
-Well defined cause of anterior shoulder pain in
throwing athlete
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Secondary Extrinsic Impingement from Instability
-Most common source of impingement pain in the
young throwing athlete -Etiology instability of
humeral head in the glenoid fossa
-Micro-instability which results from repetitive
abduction external rotation -Stretching of
anterior capsular -Swimmers, throwers, tennis
players
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Secondary Extrinsic Impingement from Instability
-Cuff tendonosis can occur anywhere in the
supraspinatus or infraspinatus tendon -Usually an
articular surface partial thickness tear
-Conventional MR less accurate in diagnosing
rotator cuff tear in the young athlete with
secondary impingement
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Secondary Impingement from Instability
-MR arthrography with ABER most
sensitive -Undersurface fraying of rotator cuff
-ABER view -Contrast extending into the
undersurface fibers
-Normal ABER
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Cuff Injuries Distraction Forces
Tensile overload resulting from violent
deceleration forces
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Cuff Injuries Distraction Forces
-Direct tensile forces (overuse, repetitive
use) -Critical zone tendonosis most common
injury
-Primarily an overload injury deceleration
phase -Repetitive use of shoulder above
horizontal level
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Small Full Thickness Tear Distraction forces
Cuff pathology from distraction forces typically
occurs in anterior portion of supraspinatus tendon
-Partial or full thickness tears can occur
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Intrasubstance Tear Shear Forces
-Rotator cuff 5 layers of collagen
-Acceleration/deceleration/rotational forces
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Cuff Injuries Internal Impingement
-Late cocking/ early acceleration
phase -Traumatic/ Atraumatic/ Micro-instability
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Internal Impingement ABER View
-Laxity of anterior band IGHL results in
posterior translation of humeral head with
compression of posterosuperior labrum and biceps
anchor
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Posterior Superior Glenoid Impingement
-Undersurface of posterior rotator cuff impinged
between the greater tuberosity and the
posterosuperior labrum
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Rotator Cuff Injuries

• Extrinsic impingement gt35 y.o.
• Secondary impingement capsular laxity
• Tensile overload distraction forces
• Intra-substance tears shear forces
• Internal impingement anterior capsule laxity

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Nerve Injuries (Quadrilateral Space Syndrome)
-Axillary Nerve Compression Neuropathy Etiologies
-Fibrous Bands- Seen with Repetitive Overhead
Activity -Paralabral Cyst Mass -Poorly
Localized Shoulder Pain in ABER Position -Atrophy
of Teres Minor and Deltoid Muscles
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Axillary Nerve Neuropraxy
-Compression of axillary nerve -Acutely leads to
edema within Deltoid and Teres Minor muscles

-High signal on T2W images
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Quadrilateral Space Syndrome
-Chronic Nerve Compression Fatty Atrophy of
Teres Minor and Deltoid -High Signal on T1W
Images -Treatment surgical release of fibrous
bands
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Superior Labrum Distraction Injuries
-Deceleration phase
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Superior labrum Compression Injury (Internal
Impingement)
-Type I SLAP injury fraying of labrum -No
distraction labrum remains firmly attached to
glenoid
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Inferior Glenohumeral Ligament Distraction
injury
-Stretching or disruption of the anterior capsule
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Inferior Glenohumeral Ligament
Composed of -Anterior band -Axillary
pouch -Posterior band
-Redundant when the arm is in neutral position
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Inferior Glenohumeral Ligament
-Prevents anterior subluxation with arm in full
abduction and external rotation
Anterior Band
Posterior Band
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Humeral Avulsion of the Inferior Glenohumeral
Ligament (HAGL) Lesion
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Long-term GH Instability
-Labrum degeneration -Cartilage
abnormalities -Osteoarthritis
-Capsular/ Ligament stretching
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Glenohumeral Internal Rotation Deficit (GIRD)
-Scarring and thickening of the posterior capsule
and has recently been described as a source of
potential pain in throwing athletes - MR imaging
demonstrates thickening of the posterior capsule
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GLAD Lesion

• Non-displaced tear of anteroinferior labrum
• Articular cartilage defect

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Labrum/Capsular Injuries

• SLAP I- compression injury (internal impingement)
• SLAP II- distraction injury (rapid deceleration
  forces)
• Stretching/disruption anterior capsule HAGL (late
  cocking phase/ rapid deceleration phase)
• Scarring and thickening of the posterior capsule
• GLAD lesion (crossed arm adduction injury)

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The Elbow Throwing Injuries
Distraction medially
Compression laterally
Excessive valgus load during late cocking
phase/early acceleration phase
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Medial Elbow
Common Flexor Tendon Superficial Structure
Ulnar Collateral Ligament Deep Structure
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Medial Epicondylitis The Role of MR Imaging

• Common flexor tendon (tendonopathy partial/
  complete tear)
• Ulnar collateral ligament (partial/ complete tear)

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Medial Elbow MR Appearance
-Common flexor tendon inserts on medial epicondyle
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-Common flexor tendon -Best evaluated in the
axial and coronal planes- T2 FS -Normal
appearance- no bright signal at attachment site
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-Common flexor tendonopathy intermediate signal
within the origin of the common flexor
tendon -Distraction forces at time of maximal
valgus loading
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Common Flexor Tendonopathy/ Partial Tear
-T2-weighted images FS axial and coronal -High
signal at attachment site surrounding edema (can
be subtle)
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Common Flexor Tendonopathy
-Bone marrow edema may be present with chronic
tendonopathy
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Medial Elbow
-Medial collateral ligament -3 bundles -Anterior
bundle best seen on MR -Most important clinically
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Ulnar Collateral Ligament Normal MR Appearance
Anterior Bundle
-Best evaluated in the coronal plane (MR
arthrography) -Firmly attached to the proximal
ulna -Loosely attached to the medial epicondyle
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(No Transcript)
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Chronic Valgus Stress Across the Medial Aspect of
the Elbow
Normal UCL
Thickened UCL
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Partial Tear of the Distal Ulnar Collateral
Ligament
Normal UCL
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Ulnar Collateral Ligament Tear
Normal UCL

T sign -Avulsion of distal ulnar collateral
ligament -Normally the ulnar collateral ligament
is firmly attached to the ulna no contrast or
fluid should extend between the two
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Unlar Collateral Ligament Complete Tear
-Complete disruption of UCL -Most common in
mid-substance -Devastating injury requires
surgical repair
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Osteochondral Injury of the Capitellum
Compression laterally
Distraction medially
-Lateral impaction repetitive valgus
stresscompression -Adolescent pitchers late
cocking/ early acceleration phase -Involves
anterior capitellum- stable lesions conservative
unstable or loose fragments- surgical gt50
develop osteoarthritis
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Pseudodefect of the Capitellum Normal MR
Appearance
-Articular cartilage extends in a 180
arc -Pseudodefect - posterior OCD - anterior
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Capitellum MR Appearance
-Pseudodefect of capitellum -Posterior
-OCD -Anterior
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OCD Loose Fragment
-MR Imaging accurate for determining if lesion is
stable or unstable -MR Arthrography improves
accuracy -Look carefully for loose bodies
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Loose Intra-articular Bodies
-Second most common joint involved after
knee -Secondary to cartilage damage from
impaction injury to capitellum -Easily detected
if joint effusion or with arthrography
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Pediatric Injuries Associated with Throwing

• Children are subject to the same throwing
  injuries as adults
• Also, subject to injuries involving the growth
  plates of the shoulder and elbow

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Injury of the Humeral Head Physeal Plate

• -Three separate epiphyseal growth plates normally
  occur in the humeral head
• Humeral head greater tuberosity lesser
  tuberosity
• -Fuse to form a single physeal plate by
  adolescence

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Little League Shoulder
14 year old pitcher
-Stress injury can occur with widening of the
plate medially (periosteal reaction) -Mechanism
Excessive tensile forces during rapid
acceleration and violent deceleration -Complete
separation of epiphysis from humeral shaft can
occur
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Elbow Medial Epicondyle Injuries
Anatomic relationships structures arising from
the medial epicondyle -Medial collateral
ligament -Common flexor tendon -Ulnar nerve
runs in canal behind med eipcondyle
(occasionally injured with avulsion of med
epicondyle)
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Medial Epicondyle Injuries (Little League Elbow)
-Mechanism violent contraction of flexorpronator
muscle group during acceleration phase of
throwing Adolescent baseball pitchers
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Medial Epicondyle Injuries (Little League Elbow)
-Avulsion Injury -Simple avulsion varying
degrees of distraction avulsion with entrapment
avulsion with dislocation -Inferior displacement
caused by pull of flexor pronator muscle group
overlying STS
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Avulsion Injury of Medial Epicondyle
-MR imaging will show subtle changes of medial
epicondylitis
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Posterior Compartment Stress
-Stress fracture of the olecranon in a
17-year-old pitcher
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Pathologic Fractures Related to Throwing
-Any lesion that weakens bone -Unicameral bone
cyst classic proximal humeral lesion/
adolescents/ can result in fracture/pain with
throwing
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13 y.o. boy with right shoulder pain several
months duration made worse with activities such
as throwing
-Lytic osteosarcoma of proximal humerus with
pathologic fracture
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Other Lesions that can cause pain during throwing
-Osteochondroma benign lesion -Mass effect lead
to mechanical pain during overhead activities
such as throwing