Introduction
History
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Baseball, the great American pastime, was first described by Abner Doubleday in 1839.
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The game evolved considerably in the early years, but it was with the advent of the overhand pitching motion in the 1880s that shoulder and elbow problems became a familiar part of the game.
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Although ballplayers are subject to usual sports-related strains, sprains, bumps, and bruises, it is in understanding the common shoulder and elbow throwing injuries that the baseball team physician is defined.
Game Coverage
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A team physician is required at the professional level.
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Physician coverage is not required at the Little League, high school, or college level.
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Occasionally, a college will provide trainer coverage.
Throwing Biomechanics and Associated Pathology
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Throwing a baseball is all about the transfer of energy from the body to the ball.
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A smooth transition will maximize ball velocity while reducing the risk of injury.
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Throwing mechanics can be separated into five phases ( Fig. 74.1 ).
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Because certain body structures are susceptible to injury during each phase of throwing, determining the phase in which the injury or pain occurs may help make a diagnosis.
Figure 74.1
Phases of the overhead throw.
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Windup
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Varies from pitcher to pitcher
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Description:
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Begins from the set position with the ball in the pitcher’s glove
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Arms drop and body rotates 90° (see Fig. 74.1 )
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The stride leg is elevated and flexed.
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Provides rhythm and balance
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Injury risk: minimal
Stride
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Description:
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Begins when the supporting leg flexes and the body is lowered
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The stride leg moves toward the plate.
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The trunk remains back.
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The stride length averages 75% of the body height with an offset of 0.4 cm (i.e., the lead foot lands almost directly in front of the back foot).
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Injury risk:
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Stride too long: The athlete will be unable to rotate the hips, resulting in a loss of velocity. This break in the kinetic chain is known as “arm throwing,” and the athlete may compensate by overloading the shoulder, resulting in a possible rotator cuff strain.
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Stride is off line to the first base side (right-handed pitcher)—the torso will be ahead of the shoulder, resulting in “opening” too soon and stressing the anterior capsule; this may result in shoulder instability.
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Stride is off line to the third base side (right-handed pitcher)—the pitcher will “throw across his body” with possible labral shearing.
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Altered stride may also be a sign of hip contracture or hip labral pathology. A physical examination is required to assess the overall range of motion and rule out femoral acetabular impingement.
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Cocking
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Places the arm in maximum external rotation while abducted
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Description:
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Begins when the stride foot makes contact with the mound
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Hip rotation begins, followed by the trunk (speed of hip rotation correlates well with ball velocity).
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Ends when the shoulder reaches maximum external rotation
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External rotation in a professional pitcher may approach 180°.
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Injury risk:
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When the shoulder is in maximum external rotation and 90° of abduction, internal impingement may occur: undersurface of the superior rotator cuff impinges against the posterior/superior labrum. This may result in undersurface tearing of the rotator cuff and posterior/superior labrum fraying.
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Anterior capsule stretching may occur over time and result in increased anterior/inferior laxity and possible glenohumeral instability (see Fig. 74.1 ).
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Acceleration
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Generates ball velocity
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Description:
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Begins with initiation of shoulder internal rotation
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Ends with ball release
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Injury risk:
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Primary movers and stabilizers of the shoulder are stressed by rapid acceleration.
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Rotator cuff strain—primary stabilizer
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Latissimus dorsi and teres major strain—internal rotation and adduction
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Labral injury if humeral head does not remain centered during rapid acceleration
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The elbow is placed under significant valgus stress—ulnar collateral ligament (UCL) is under tension while radiocapitellar articulation is under compression. Thus, UCL is at a risk of tearing and radiocapitellar articulation at a risk of osteochondral injury.
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Valgus extension overload—as elbow extends under valgus load, the posteromedial aspect of the olecranon may impinge against the olecranon fossa, resulting in posteromedial elbow pain. Over time, spurring and degenerative changes may occur at the posteromedial ulnohumeral articulation (see Fig. 74.1 ).
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Deceleration
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Dissipation of energy as ball is released
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Distractive force at shoulder is equivalent to pitcher’s body weight.
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Description:
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Begins at ball release
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Final elbow extension occurs
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Final internal rotation of shoulder occurs
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Ends when internal rotation velocity reaches zero
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Injury risk:
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Superior labrum anterior to posterior (SLAP) lesion—traction injury to the superior labrum at insertion of the long head of biceps tendon
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Bennett lesion—traction osteophyte of the posterior glenoid lip with thickening of posterior labrum and capsular attachment due to repetitive traction
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Follow-Through
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Allows for dissipation of energy
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Description:
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Begins at the end of shoulder internal rotation
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Ends when the trailing leg touches the ground
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Injury risk:
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An appropriate follow-through reduces the risk of injury by gradual dissipation of the body’s kinetic energy.
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Common Baseball Throwing Injuries
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Overhead throwing motion results in a preponderance of upper extremity injuries secondary to the significant forces generated.
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Underhanded pitching motion is not associated with significant overuse injury.
Shoulder
Rotator Cuff Injury
Description: The rotator cuff is the key to a healthy throwing shoulder, centering and controlling the humeral head as the arm is accelerated. With weakness, the cuff may impinge against the acromial arch, the capsule may stretch or cause labral tear ( Fig. 74.2 ). With extreme external rotation and abduction during cocking and early acceleration, undersurface tearing may occur. Rotator cuff injury is the primary differential diagnosis for throwing discomfort.
Figure 74.2
Rotator cuff anatomy.
Symptoms: Pain often referred to lateral shoulder; posterior/superior shoulder pain with arm in the cocking position suggests internal impingement with possible undersurface cuff tear; shoulder may continue to ache after activity
Diagnosis:
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Pain and/or weakness with resisted external rotation with elbow at side
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Positive Jobe’s sign: pain from rotator cuff isometric contracture
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Positive Hawkins sign: subacromial impingement of bursal side of cuff against acromial arch
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Pain with extreme abduction/external rotation—internal impingement of articular surface of the cuff against posterior/superior labrum
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Magnetic resonance imaging (MRI) to define the extent of injury when nonsurgical management fails. MRI should be considered as a presurgical study. History and physical examination directs initial treatment. When MRI is advised, consider contrast to better define partial-thickness undersurface tears or associated labral pathology. The abducted and externally rotated (ABER) view of the shoulder is helpful to define posterior, superior labral, and undersurface cuff tears.
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Treatment:
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Relative rest—varies from complete shutdown of all throwing activity to shifting the player’s position (e.g., playing first base instead of pitching)
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Physical therapy
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Rotator cuff strengthening
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Thera-Bands with elbow at the side
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Advance to pulleys with arm in throwing position (shoulder abducted 90° with arm internally rotating against resistance from 90° of external rotation to neutral position)
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High repetitions (30) with single set
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Plyometrics before trial of throwing
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Scapular stabilization—must rule out scapular dyskinesis
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Posterior capsular stretch—must rule out tight posterior capsule
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Cortisone injection—subacromial
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Only after failure to respond to physical therapy
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Must shut down for 5 days after injection
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Surgery if nonsurgical management fails
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Arthroscopic debridement for partial thickness tears
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Arthroscopic or open repair for partial tears >50%; poor outcomes for return to pitching when a rotator cuff requires a repair
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Labral Injury
Description: The superior/posterior labrum can be injured by impingement during the cocking phase or through distraction of the biceps anchor during deceleration (remember, the arm as well as the ball are in essence being thrown from the body and tension from the long head of the biceps can pull the labrum from its attachment).
Symptoms: Deep shoulder joint pain with throwing; typically not a problem with daily activities; pain is often positional and is not present at rest
Diagnosis: Positive provocative maneuvers with triggered pain located deep in the shoulder joint ( Fig. 74.3 ):
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O’Brien’s: Pain while resisting a downward force with the arm extended in the neutral position, horizontally adducted 30°, and thumb pointing down
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Shear: Pain with manipulation of the shoulder in 90° of abduction and maximal external rotation
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Rotation/compression: McMurray’s of the shoulder—compress and rotate the shoulder in an attempt to pinch the labrum and trigger pain
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