A shoulder injury in an overhead throwing athlete is a complex condition that can present several difficulties in both diagnosis and treatment. The ability to throw a baseball at velocities exceeding 90 miles per hour with pinpoint accuracy is the end result of a complex transfer of energy from the lower extremity through the trunk, shoulder, elbow, and finally, the hand. The stresses placed on the individual links of the kinetic chain during throwing can lead to failure of and injury to these structures. The repetitive acceleration and deceleration of the arm during the throwing motion places the arm in extreme positions and under extreme stresses, which can lead to chronic overuse-type injuries, as well as acute shoulder injuries.
The pitcher’s shoulder endures supraphysiologic forces while a pitch is thrown. Professional pitchers have the ability to generate up to 92 Nm of humeral rotation torque, which is greater than the torsional failure limit found in cadavers. The shoulder of a pitcher experiences forces nearly half of his or her body weight during the late cocking phase and distraction forces of nearly the entire body weight during the deceleration phase. The shoulder endures peak angular velocities of 7250 degrees per second during a single pitch. To perform these supraphysiologic feats, the shoulder will often make several adaptations. However, the stresses placed on the shoulder by throwing can lead to injuries to several of the structures in and around the shoulder.
Sports physicians who treat overhead throwing athletes must be familiar with the subtle changes in a pitcher’s performance to recognize an injury to the shoulder. Often these athletes may not primarily report pain but instead will present with decreased velocity or accuracy of their pitch. A thorough understanding of the anatomy and adaptive changes that occur in the thrower’s shoulder along with the physiology of throwing is necessary to provide treatment in these complicated cases. In addition, a systematic approach to evaluating pathology in the shoulder used in throwing is critical because many injuries are multifactorial as a result of any number of mechanical, technical, training-related, and structural factors.
Adaptations of the Thrower’s Shoulder
Over time, overhead throwing athletes develop well-described adaptations in response to the stresses placed on the shoulder as a result of throwing. These changes most likely begin in early childhood when the athlete begins throwing. The changes include both soft tissue and bony adaptations. These adaptations may be subtle but are imperative to the thrower’s abilities to function at a high level under such nonphysiologic conditions.
One of the primary physiologic changes seen in the thrower’s shoulder is the range of motion (ROM). Most throwers exhibit a difference in the amount of external rotation (ER) and internal rotation (IR) between the shoulder they use to throw and the shoulder not used in throwing ( Fig. 50-1 ). When the shoulder used in throwing is examined in 90 degrees of abduction, ER is greater compared with the shoulder that is not used in throwing, and IR is commonly decreased. The comparatively diminished IR has been termed glenohumeral internal rotation deficit (GIRD).
Brown et al. reported that professional pitchers had a mean shoulder ER of 141 degrees with the arm at 90 degrees of abduction. The increased ER was 9 degrees more than their nondominant arm and also 9 degrees more than the shoulder that position players use in throwing. Although the magnitude of IR and ER seen in the dominant and nondominant arm of overhead throwing athletes differs, the overall range of motion arc is usually similar. Wilk et al. reported that the total rotational arc of motion in the shoulder used in throwing was within 7 degrees of the total motion of the shoulder not used in throwing. These investigators found that the total rotational arc of motion was 176.3 degrees for both shoulders. Ellenbecker et al. examined the total shoulder range of motion in 167 elite athletes who engaged in repetitive overhead motions. No difference was found between the arm used to throw and the arm not used to throw of the athletes studied, but these investigators did find significantly less arm total rotation of motion in the dominant versus nondominant arm of elite junior tennis players (149.1 degrees vs. 158.2 degrees, respectively). These studies confirm that ER is increased and IR is decreased in the dominant shoulder of overhead throwers, but that the total arc of motion of the shoulder is nearly equal.
The bony adaptations in the thrower’s shoulder have been well documented. Crockett et al. evaluated 25 professional pitchers and 25 nonthrowing subjects to evaluate the role of humeral head retroversion in relation to increased glenohumeral ER. The throwing group demonstrated a 17-degree increase in retroversion compared with the shoulder not used in throwing. The group of athletes who did not perform overhead motions did not show a difference in retroversion between their shoulders. These investigators concluded that the dominant shoulder of the throwing group exhibited significantly greater humeral head retroversion.
Reagan et al. evaluated 54 asymptomatic college baseball players radiographically to determine their humeral retroversion. Humeral retroversion averaged 36.6 degrees in the dominant shoulder and 26 degrees in the nondominant shoulder. The investigators concluded that increased ER and decreased IR of the shoulder were due to the bony adaptations in the proximal humeral anatomy more so than soft tissue changes. Chant and colleagues found an average 10.6 degrees greater retroversion in the arm used in throwing in overhead throwing athletes compared with the arm not used in throwing. The greater humeral head retroversion was associated with increased ER and decreased IR in the arm used in throwing.
The increased retroversion may be a response to the stresses that the thrower places on his or her physis while throwing at a young age. Yamamoto et al. showed that the retroversion angle in the dominant arm was greater than in the nondominant arm. Based on their data, these investigators concluded that the repetitive throwing motion does not increase the retroversion of the humeral head but instead restricts the physiologic derotation process of the humeral head during growth. The amount of retroversion appears to be greater in pitchers than in athletes who play other positions.
Soft tissue adaptations also occur in overhead throwing athletes as a result of the large rotational and distractive forces that act upon the glenohumeral joint during the throwing motion, resulting in posterior capsular tightness and anterior capsular laxity. Most throwers exhibit laxity of the glenohumeral joint. Krishman and colleagues reported that the excessive laxity exhibited by the thrower is the result of repetitive throwing. The term microinstability has been used to describe the acquired capsular laxity that allows increased humeral head translation and increased arm rotation. The cause of this microinstability is believed to be repetitive tensile loading as a result of scapular protraction or repetitive ER loading. The changes in laxity appear to be an adaptation to throwing because increased anterior-posterior humeral head translation has been demonstrated in both symptomatic and asymptomatic pitchers.
Investigators have attributed the posterior shoulder soft tissue tightness seen in overhead throwing athletes to the deceleration phase of the throwing motion. Pitchers appear to have increased laxity of their shoulder compared with athletes who play other positions. Bigliani et al. evaluated the shoulders that professional pitchers and players of other positions use to throw and found a sulcus sign in 61% of dominant shoulders in pitchers but in only 47% of dominant shoulders in players of other positions. These investigators considered the increased laxity to be a congenital change in overhead throwing athletes.
Biomechanics of Throwing
To understand the injuries that occur in the shoulder that is used in throwing, the stresses placed on the shoulder during the action of throwing must be understood. The phases of overhead throwing have been studied extensively in pitchers. The overhead throwing motion can be broken down into six discrete phases, which include the wind-up, early cocking, late cocking, acceleration, deceleration, and follow-through phases ( Fig. 50-2 ). The overhead throwing motion takes approximately 2 seconds to complete, with 75% of that time occurring during the preacceleration phase.
During the first phase of throwing, the wind-up, the body raises over the center of gravity and the shoulder is placed in slight abduction and IR. At this point in the pitching motion, no stress is placed on the upper extremity. During the early cocking phase, the arm is placed into abduction and ER. At this point, the arm rotates behind the body axis approximately 15 degrees. Once the arm reaches the top of its motion and stops moving backward, the early cocking phase ends and late cocking phase begins. At the beginning of the early cocking phase, the deltoid is active as it abducts the arm. Later, the rotator cuff musculature fires, cocking the arm into a more externally rotated position.
The third phase of throwing, late cocking, begins as the lead leg contacts the ground and ends when the arm reaches maximal ER of nearly 180 degrees. During this phase, the scapula retracts to provide a stable glenoid surface for the humeral head to compress against. The upper arm is maintained in 90 degrees to 100 degrees of abduction, and the elbow moves even with the plane of the torso. The humerus progresses into ER, and the humeral head translates posteriorly on the glenoid because of the increasing tightness of the anterior structures. The infraspinatus and teres minor muscles are active early in the late cocking phase, leading to the external rotation of the humerus. The subscapularis becomes active late in this phase as IR begins. The rotator cuff compresses the humeral head against the glenoid with significant force.
The acceleration phase of throwing begins as the humerus internally rotates and ends when the ball is released. Although significant angular velocity is developed by the muscular forces around the shoulder during this phase, little stress is noted in the shoulder. The triceps becomes active early on in the acceleration phase, followed by the pectoralis major and the latissimus dorsi muscles later. The deceleration phase begins just after the ball is released and ends when humeral internal rotation ceases. This phase leads to tremendous stresses generated by the rotator cuff muscles as the arm is brought to an abrupt halt. Eccentric loads on the posterior cuff reach 1000N as the muscle dissipates the kinetic energy generated in the earlier phases of the throw.
The final phase of the throwing motion is the follow-through. It is at this point of the pitch that the body regains balance and stability. The muscles cease to fire and the compressive forces on the glenohumeral joint drop significantly.
Pathophysiology of the Thrower’s Shoulder
Internal Impingement
Great stresses are placed on the thrower’s shoulder during the overhead motion. Although isolated injuries of the shoulder structures may occur, a cascade of pathologic changes is commonly associated with shoulder pain in the overhead throwing athlete. Common injuries to the throwing shoulder include superior labral tears, partial-thickness tears of the posterior supraspinatus and anterior portion of the infraspinatus, a tight posterior capsule, and anterior instability. Andrews and colleagues noted that labral tears were present in 100% of 36 competitive athletes with articular-sided partial rotator cuff tears. Sixty-four percent of this cohort were baseball pitchers. Andrews et al. initially theorized that the partial articular-sided tears resulted from repetitive large eccentric forces to the supraspinatus and infraspinatus tendons during the deceleration phase of throwing. Davidson and colleagues considered the repetitive contact between the articular side of the rotator cuff and the posterosuperior glenoid in late cocking to be the primary cause of tears. Because of the limited patient population and variable presentation of the syndrome, our understanding of the processes leading to internal impingement has evolved gradually and remains incomplete.
In 1992, Walch et al. reported on contact that occurs between the deep side of the supraspinatus tendon and the posterosuperior edge of the glenoid cavity in tennis players and coined the term internal impingement . Jobe applied this idea of internal impingement to athletes who engage in repetitive overhead motions and described an expanded spectrum of injury to the rotator cuff, glenoid labrum, and bone. Internal impingement is characterized by contact of the articular surface of the rotator cuff and the greater tuberosity with the posterior and superior glenoid rim and labrum in the position of ER and abduction of the arm ( Fig. 50-3 ). The shoulder is predisposed to internal impingement in overhead throwers because of the anterior translation and extremes of ER associated with throwing. Repeated contact with internal impingement has been postulated to lead to undersurface articular-sided partial rotator cuff tears and superior labral lesions. Jobe proposed that two different extremes of positions or motions in throwers could cause the constellation of injuries seen in internal impingement—specifically, either direct forward elevation or abduction-ER that occurs during late cocking. Jobe believed that microinstability exacerbates the effects of internal impingement.
Burkhart and Morgan proposed that the pathologic condition in the rotator cuff and the labrum seen in overhead throwing athletes is a result of a hypertwisting mechanism with large shear stresses leading to fatigue failure of both the rotator cuff and the biceps tendon insertion point of the labrum. These lesions result from an acquired posterosuperior instability that is caused by posteroinferior capsular tightness termed the peel-back mechanism by these authors. They reasoned that the posterior capsule must withstand tensile forces of up to 750 N during the deceleration and follow-through phases of throwing. The posterior tensile forces placed on the shoulder during these actions are offset by the eccentric contraction of infraspinatus and the posteroinferior capsule, including the posterior band of the inferior glenohumeral ligament. The posterior contraction is believed to shift the center of rotation of the shoulder to a more posterosuperior location, creating posterosuperior instability with the shoulder in abduction and ER. The humeral head can then externally overrotate, which produces increased shear in the rotator cuff tendon and increased internal impingement. It has been contended that the loss of internal impingement is actually pathologic, in that the absence of this normal restraint to hyperextension of the humeral head in the throwing motion can lead to a superior labral anterior to posterior (SLAP) tear, fatigue failure of the rotator cuff, and “dead-arm” syndrome.
Muscle fatigue and imbalance may also play a role in the development of internal impingement by altering the mechanics of the shoulder. Fatigue-related humeral hyperextension can occur during the late cocking phase when the rotator cuff muscles cannot completely resist the large acceleration forces generated while pitching. The repetitive motion of throwing may cause a progressive delamination of the posterior capsulolabral structures of the rotator cuff. The excessive violent deceleration of the arm in the follow-through may cause an abrasive degeneration of the rotator cuff on the posterosuperior aspect of the glenoid.
Although a range of theories have been proposed regarding the pathophysiologic role of internal impingement, it seems clear that the causes of disability in the shoulder used for throwing are multifactorial. Shoulder pathology in overhead throwing athletes should be viewed as a syndrome with a cascade of interrelated pathologies. The cardinal lesions of internal impingement, including articular-sided rotator cuff tears and posterosuperior labral lesions, have been shown to occur in association with a number of findings, most importantly GIRD and SICK scapula syndrome (i.e., s capular malposition, i nferior medial border prominence, c oracoid pain, and dys k inesis of scapular movement). Pain in the thrower’s shoulder has also been associated with alterations in the kinetic chain and scapulothoracic function.
Muscle Imbalances
Muscle imbalance and weakness play a role in the development of shoulder pain in overhead throwing athletes. Both symptomatic and asymptomatic throwers have been shown to demonstrate imbalances of shoulder muscle strength. In overhead throwing athletes, an adequate ratio of concentric agonist muscle strength to eccentric antagonist muscle strength is crucial for dynamic stability and optimal function. In throwers with impingement syndrome, imbalances in rotator cuff musculature have been identified, including a relative weakness of the internal rotators, resulting in an abnormal internal/external strength ratio. The muscle imbalance alters the anterior/posterior force couples that stabilize the glenohumeral joint and increases the compression forces in the joint. The muscle imbalance also decreases the ability of the shoulder to decelerate during the deceleration phase of pitching.
Abnormalities in the scapular stabilizers have also been shown in athletes who perform overhead motions. Abnormal activation latencies seen on electromyography were found in the scapular stabilizers of patients with internal impingement syndrome. The serratus anterior and lower trapezius muscles both showed delayed onset latency and decreased activity during the throwing motion in persons with shoulder pain. In addition to muscle imbalance, muscle inflexibility is also seen in overhead throwers. Several muscles around the shoulder become tight in the thrower, including the pectoralis minor, subscapularis, and latissimus dorsi. The muscle tightness is believed to result from chronic tensile overload and fibrotic scar tissue formation or possibly from an adaptive response of the muscles due to the increased stresses of throwing. Tightness of the subscapularis decreases arm ER, limiting arm cocking, whereas tightness of the latissimus dorsi limits overhead positioning and cocking. A tight pectoralis minor muscle leads to an anterior scapular tilt, decreasing the ability of the arm to externally rotate during late cocking and possibly leading to shoulder impingement. Alterations in both muscle strength and flexibility play an important role in the development of a painful throwing shoulder.
Scapular Dyskinesis
The scapula plays a critical role in energy transfer from the trunk to the humerus. Clinically, it commonly is believed that scapular malposition can be a cause of shoulder problems in athletes who throw. Kibler and Thomas described dyskinesis as an alteration of static scapular position or dynamic scapular motion in coordination with arm motion. They stated that the protracted, downwardly rotated scapula with an anterior tilt is caused by abnormal muscular imbalances, or that abnormal firing patterns may contribute to rotator cuff symptoms that overhead throwing athletes develop with activity. As previously mentioned, the abnormally positioned thrower’s scapula has been given the mnemonic SICK by Burkhart and colleagues. These changes in scapular position lead to external impingement as a result of anterior tilt, internal impingement, decreased rotator cuff strength, and anterior capsular strain. Altered static and dynamic scapular mechanics arise from overuse and weakness of scapular stabilizers and posterior rotator cuff muscles.
The SICK scapula sits in a protracted and upwardly tilted position, which predisposes the shoulder to rotator cuff tears and superior labral injuries. This position of the scapula leads to anterior tension, posterior compression, and increased glenohumeral angulation. The cascade of events begins with glenoid protraction, where the anterior band of the inferior glenohumeral ligament tightens, limiting anterior translation of the humeral head and eventually stretching out as a result of chronic strain. At the same time, the posterior edge of the glenoid is brought toward the humerus, placing the posterosuperior labrum and rotator cuff in contact and making articular-sided partial rotator cuff tears and superior labral tears common. Finally, excessive protraction increases glenohumeral angulation. The increased glenohumeral angulation leads to the thrower’s arm lagging behind the body. Excessive external rotation with the preexisting scapular protraction produces posterosuperior glenoid impingement.
Glenohumeral Internal Rotation Deficit and Motion Deficits
It is well recognized that overhead throwing athletes commonly experience ROM deficits. The alterations in ROM are seen in virtually every thrower with shoulder pain. GIRD presents as side to side asymmetry represented by the dominant arm showing decreased IR, increased posterior capsular tightness, and humeral retroversion with increased ER. A tight posterior capsule is part of the cascade that leads to pain in a thrower’s shoulder; however, the exact etiology of the IR deficit is not exactly understood. Posterior capsule tightness has been shown to result in multiple kinematic alterations such as decreased shoulder IR, horizontal adduction and flexion, and increased ER. Posterior capsule tightness has been associated with multiple pathologic injuries including subacromial impingement, SLAP tears, and internal impingement. Because of the posterior capsule tightness, the labrum is particularly vulnerable to injury, in part because the humeral head is no longer able to roll easily on the glenoid-labrum complex as it would normally and is directed in a shearing pattern of force at the labrum.
Instability
Because of the inherent instability of the shoulder, the overhead throwing athlete requires significant dynamic stability to maintain shoulder integrity adequately throughout the full ROM. The joint is stabilized not by bony architecture but by the ligaments and musculotendinous units. True posttraumatic glenohumeral instability is less frequent in this group of athletes; instead, microinstability is more common in throwers. As described previously, microinstability is a term that is commonly used to describe acquired capsular laxity that may allow increased humeral head translation with arm motion. Some investigators believe that microinstability is true laxity and occurs from repetitive tensile loading as a result of scapular protraction. Another theory is that the instability is due to repetitive ER loading. Increased anterior-posterior humeral head translation has been demonstrated in both symptomatic and asymptomatic pitchers. Jobe and Pink believed that the repetitive and forceful overhead activity causes a gradual stretching out of the anterior-inferior capsuloligamentous structures, leading to subclinical laxity, instability, and impingement, which they termed instability complex. Capsular laxity and increased functional translation up to an unknown level exist in the throwing athlete, representing functional adaptations. Above this level, the instability created by this translation is pathologic. Burkhart and colleagues have suggested that glenohumeral ER greater than 120 degrees indicates a pathologic capsular laxity that should be addressed with anterior capsular plication as part of operative treatment.
History
The etiology of a shoulder injury in an overhead throwing athlete is best determined by taking a thorough history. Pitchers frequently describe subjective feelings of heaviness and sluggishness, stiffness, fatigue, and/or weakness and the inability to “bring it.” These feelings are accompanied by the objective findings of decreased velocity on their fastball, lack of movement, and decreased accuracy. Acute injuries occur in overhead throwing athletes; however, it is much more common for injuries to be a result of overuse and fatigue. The timing of the onset of symptoms, current and previous treatment modalities, and a history of a previous injury to the shoulder should be determined. The athlete should also be asked questions specifically related to his or her pitching, including any change in mechanics, development of a new pitch, increased pitch count, change in training regimen, in what phase of the pitch he or she feels the pain, and if any other part of the body has been injured that could be changing the throwing mechanics. The athlete should be questioned about injury to the hip, core, and lumbar spine because injuries in these areas can lead to compensatory alterations in throwing mechanics and increased stress on the shoulder.
Typical symptoms in an overhead throwing athlete with pain include anterosuperior or posterosuperior shoulder pain in the late cocking phase. Labral tears may lead to reports of “popping,” “locking,” or “snapping.” The history should also include questions regarding provocative and alleviating factors, instability, loss of motion, associated weakness, and tingling or numbness that radiates down the arm.
Physical Examination
A thorough and systematic physical examination should be performed for all throwers who present with shoulder pain. The examination should focus not just on the shoulder or upper extremity but also on the remainder of the kinetic chain, including the lower extremities and trunk. The athlete’s natural posture may be evaluated while he or she walks to the examination room and during history taking. The patient should be asked to stand in his or her natural posture and observed from the front, back, and side. The overall alignment, shoulder height and position, pelvic tilt and rotation, lower extremity alignment, head and neck position, and arm position must be evaluated. Functional movements should be assessed to determine hip and trunk control, muscle imbalance, and inflexibilities, which can be accomplished by having the patient balance on one leg and do a single leg half squat. While performing these maneuvers, the patient should be observed for compensatory movements such as pelvic tilt or rotation. Ankle flexibility, lumbar and thoracic spine and shoulder girdle mobility can be assessed by having the patient perform a full squat with his or her heels on the ground and arms overhead. Flexibility of the hamstrings and the thoracic and lumbar spine can be assessed by having the patient perform a straight-leg toe touch. While supine, ROM of the hips is checked to determine if femoroacetabular impingement is present.
Once a comprehensive examination of the remainder of the kinetic chain is completed, a focused evaluation of the affected shoulder is performed. The entire shoulder complex must be visualized. Male patients are asked to remove their shirts, and female athletes should be asked to wear a tank top or sports bra. First, the shoulder is inspected visually. Muscular atrophy and scapular winging should be documented. The position of the scapula at rest should be noted, including asymmetry of scapular tilt, rotation, and elevation or depression of the scapula. Scapular depression in the resting position is common in overhead throwing athletes with a painful shoulder. After visual inspection, the shoulder should be systematically palpated to identify areas of pain. All bony prominences are palpated, including the bicipital groove, greater tuberosity, and acromioclavicular (AC) joint. Tenderness over the long head of the biceps tendon can be indicative of biceps tendonitis or potentially a SLAP tear. Coracoid process tenderness can be suggestive of pectoralis minor tendonitis or tightness, which has been associated with scapular protraction and dyskenesis.
Shoulder ROM, both active and passive (PROM), should be assessed, with special attention given to glenohumeral and scapulothoracic motion. Glenohumeral joint PROM is assessed for ER and IR at 90 degrees of abduction and for ER at 45 degrees of abduction in the scapular plane. The patient should be examined in both the standing and supine positions. Increased ER with the arm at the side with the patient in the supine position can be reflective of rotator interval laxity. Increased ER in the abducted and externally rotated (ABER) position reflects anteroinferior capsular laxity or humeral retroversion.
The presence of GIRD must be identified. The posterior inferior capsule is evaluated by stabilizing the scapula and passively rotating the arm when it is abducted 90 degrees. As previously delineated, internal rotational deficits of 15 degrees to 20 degrees can be seen in the arm used in throwing compared with the arm not used in throwing as a result of adaptations of the throwing shoulder. However, the overall arc of motion in the shoulder used in throwing is typically the same as in the arm not used in throwing. Decreased flexibility of the latissimus dorsi, teres major, subscapularis, and pectoralis major muscles can result in an anterior malposition of the humeral head, which presents as a loss of IR.
In addition to ER and IR, passive and active forward flexion and abduction need to be recorded. When assessing PROM, the clinician should assess both the quantity of motion and the end feel. Palpation of the shoulder during ROM can uncover crepitus, which may indicate bursal thickening or labral or rotator cuff pathology.
Muscle strength should be evaluated after shoulder ROM is determined. Manual muscle strength testing should aim to isolate the muscle being tested and compare the injured side with the contralateral, uninjured side. Supraspinatus strength is determined with use of the empty can test, in which the athlete is in the standing position with the arm elevated to shoulder level in the scapular plane with the thumb pointing down. The examiner applies downward force while the patient resists. The test is positive if weakness is present. The infraspinatus and teres minor muscles are evaluated by resisting ER with the arm at the side and the elbow flexed to 90 degrees. The subscapularis is best assessed using the “lift off” (Gerber) test in which resistance is given to the palm as the back of the hand is lifted off the back with the arm in full IR. The IR lag sign, which may be more sensitive, is performed with the patient sitting and the examiner holding the hand behind the lumbar region in full IR. The patient maintains the position when the examiner releases the arm. The test is positive if the athlete is unable to hold the position. Subtle subscapularis weakness may also be demonstrated with the modified bear hug. The hand on the involved side is placed on the contralateral shoulder with the arm elevated to 45 degrees, and ER of the hand away from the shoulder is resisted.
Subacromial impingement is assessed using the Hawkins-Kennedy and Neer tests. The Hawkins-Kennedy test is performed with the patient standing; the affected arm is forward-flexed 90 degrees and then forcibly internally rotated. This maneuver drives the greater tuberosity farther under the coracoacromial ligament, producing impingement. The test is positive if the patient experiences pain. Sensitivity of the Hawkins-Kennedy test has been reported to be between 0.55 to 0.80, whereas specificity has been reported to be 0.38 to 0.59. During the Neer test, the examiner forces the patient’s internally rotated arm into maximal forward elevation. It is positive if the patient’s symptoms are recreated. The sensitivity and specificity of the test have been reported to be 0.64 to 0.80 and 0.30 to 0.53, respectively.
Several tests are available to examine the labrum of the throwing athlete. The examiner should use the tests with which he or she is comfortable and develop a consistent pattern of examining the labrum. A variety of tests have been described to assess for the presence of superior labral lesions. O’Brien’s active compression test is frequently used to evaluate for SLAP tears. In this test the athlete forward flexes his or her arm to 90 degrees with the elbow in full extension. The arm is adducted 10 degrees to 15 degrees medially and the arm is internally rotated so the thumb is pointing down. The examiner applies a uniform downward force to the arm. The technique is repeated a second time with the palm facing up. The test is considered positive if the patient reports increased pain in the anterior shoulder joint line region with the thumb down versus the palm up. The sensitivity of the test has been reported to be 100% with 97% to 99% specificity to detect glenoid labral or AC joint abnormality. In athletes with shoulder pain, the active compression test was found to have a sensitivity of 0.78 and a specificity of 0.11. The passive distraction test described by Schlechter and collegues has also been found to be useful in evaluating SLAP tears. The passive distraction test is performed supine with the shoulder flexed to 150 degrees and the forearm is passively pronated to elicit increased biceps tension. Deep pain or a pop with passive pronation is suggestive of a superior labral injury. The Speed test has shown variable sensitivity and specificity in identifying SLAP tears in the literature.
The shoulder is evaluated for instability by testing the integrity of the anterior and posterior labrum. Anterior instability can be assessed using the anterior apprehension test. With the patient supine, the examiner passively abducts and externally rotates the humerus. The test is considered positive if the athlete reports pain, instability, or the feeling of impending dislocation. The Jobe relocation test is performed in the same manner, with the examiner placing the arm in 90 degrees of abduction, full ER, and 90 degrees of elbow flexion. A posterior force is placed on the head of the humerus. The test is positive if the patient’s pain or apprehension diminishes with applied force. Apprehension suggests more severe anterior instability and bony deficits of the glenoid or humerus.
The Crank test evaluates the glenoid labrum. The sensitivity of the test ranges greatly in the literature from 0.13 to 0.91. The test is performed with the patient in the supine position while the examiner elevates the humerus 160 degrees in the scapular plane. Axial load is applied to the humerus while the shoulder is internally and externally rotated. A positive test occurs when the patient reports pain or clicking in the shoulder.
The posterior labrum is evaluated with the labral shear test. The abducted and extended arm is passively lowered to “shear” the labrum between the glenoid and greater tuberosity. The jerk test and the Kim test are also helpful in evaluating the posterior labrum. The Kim test is performed with the athlete sitting and his or her arm abducted 90 degrees. The examiner holds the elbow and lateral aspect of the proximal arm and applies a strong axial loading force. The examiner then elevates the arm to 135 degrees and adds a posterior/inferior force. Development of posterior shoulder pain is consistent with a positive test and a posterior labral tear. The sensitivity and specificity of the test have been found to be 0.80 and 0.94, respectively, by the test developer. The jerk test is performed with the patient sitting and examiner holding the scapula with one hand and internally rotating and abducting the patient’s arm to 90 degrees with the other. The examiner then horizontally adducts the arm while applying an axial loading force. Sharp pain indicates a positive test. The sensitivity and specificity have been reported to be 0.73 and 0.98, respectively.
An important but often underemphasized part of the shoulder physical examination is evaluation of the scapulothoracic joint. Many injured throwers demonstrate loss of external rotation control and elevation and posterior tilt of the scapula, which are manifested as medial scapular border winging. The scapula should be visualized with the arm at rest and at the side. Note is made of any asymmetry of scapular tilt, rotation, elevation, or depression. A resting position of scapular depression can be representative of a SICK scapula. During the scapular assistance test, scapular upward rotation is assisted by manually stabilizing the upper medial scapular border and rotating the inferomedial border as the arm is abducted. A positive test will relieve symptoms of dyskinesis including impingement, clicking, or rotator cuff weakness that are present when assistance is not given.
The scapulohumeral rhythm should be determined by having the patient slowly elevate and lower his or her arms in abduction and forward flexion while looking for dyskinetic scapular motion and/or limitations in either the raising (concentric contraction) or lowering (eccentric) phase of scapular stabilizer muscle function. Scapular dyskinesis is most commonly observed during the eccentric phase of lowering the arms from forward flexion. The overall ratio of glenohumeral to scapulothoracic, AC, and sternoclavicular motion is 2 : 1. The scapular slide test uses three positions to elicit scapular dysfunction. With the patient standing, the examiner records the measurement between the inferior angle of the scapula and the spinous process of the thoracic vertebra of both scapulae at the same horizontal level in the three positions. Position 1 consists of the glenohumeral joint in the neutral position, which is accomplished with the hands at the side. Position 2 is 45 degrees of shoulder abduction and IR. The scapula is inspected with the patient’s hands on his or her hips with the thumbs directed posteriorly. The final position is with the upper extremity in 90 degrees of abduction and full IR. A difference between sides of greater than 1.5 cm is considered scapular asymmetry.
In summary, examination of the painful throwing shoulder must be complete, systematic, and consistent. Several examination maneuvers have been developed to identify the many potential causes of shoulder pain and/or dysfunction. The examiner must develop a routine that he or she performs each time he or she examines the thrower to avoid missing important findings. Additionally, the examiner must avoid focusing only on the shoulder and instead perform a complete assessment of the entire kinetic chain.
Imaging
Complete evaluation of the shoulder in an overhead throwing athlete should include the standard radiographic views of the shoulder consisting of anteroposterior, axillary, and outlet views. These images allow visualization of the glenohumeral articulation, as well as acromial morphology and visualization of the inferior glenoid. Other useful views may include the Stryker notch and West Point views.
After obtaining plain radiographs, the next step is commonly magnetic resonance imaging (MRI). In most centers and practice settings, the imaging modality of choice to assess soft tissue pathology of the shoulder is MRI with intraarticular contrast (i.e., an MRI arthrogram [MRA]). An MRA provides the most comprehensive view of the rotator cuff tendons and muscles, glenoid labrum, biceps tendon, and other intraarticular structures. MRI-enhanced arthrography outperforms plain MRI in diagnosing SLAP lesions with a sensitivity and specificity of 89% and 91%, respectively, and an accuracy of 90%. In overhead throwing athletes, the most common lesions are partial-thickness rotator cuff tears and glenoid labral pathology. SLAP tears are identified on MRA by identifying contrast material between the superior labrum and the glenoid that extends around and under the biceps anchor on the coronal oblique view. Use of intraarticular contrast material can be especially helpful in distinguishing between full-thickness and partial-thickness rotator cuff tears. Additional sequences with the arm in the ABER position can be quite useful in this particular patient population to delineate more subtle labral and rotator cuff pathology ( Fig. 50-4 ). The ABER view on MRI is most helpful in identifying articular-sided tears of the rotator cuff, especially those with a delaminated component. Findings suggestive of partial-thickness tears include focal increased signal intensity with morphologic disruption extending through a portion of nonrestricted tendon, irregularity, and thinning or thickening of the tendon. In the setting of internal impingement pathology, MRI findings include articular-sided degeneration and tearing at the junction of the infraspinatus and supraspinatus tendons with associated degeneration and tearing of the posterosuperior glenoid labrum. Subcortical cysts and chondral lesions may be seen in the posterosuperior glenoid and humerus as a result of repetitive impaction.
Connor et al. reported that 40% of dominant shoulders in a series of 20 asymptomatic overhead throwing athletes had partial- or full-thickness rotator cuff tears in their throwing arm compared with no tears in the nondominant shoulders. Halbrecht et al. performed noncontrast MRI of the shoulder in the ABER position in the throwing and nonthrowing arms of 10 asymptomatic college baseball players. Contact between the rotator cuff and posterosuperior glenolabral complex was seen in all shoulders, leading the investigators to conclude that this contact was a normal physiologic occurrence. However, signal changes consistent with tendinosis or delamination were seen in 4 of the 10 shoulders used to throw, whereas 3 of the 10 shoulders used to throw also showed labral tears. These signal changes were not seen in the shoulder of each athlete that was not used in throwing. Given the high rate of abnormal findings seen in the asymptomatic shoulder, the authors stressed caution in treating asymptomatic athletes with abnormalities seen on MRI.
Computed tomography (CT) is less commonly used to evaluate a painful shoulder. However, CT is the gold standard for measuring both humeral version and glenoid version, which have been implicated in the etiology of injuries in the shoulder used in throwing, such as internal impingement and rotator cuff tears. Changes in the humeral anatomy can be measured accurately with use of CT or semiaxial radiographs, as described by Soderlund et al. Three-dimensional CT reconstruction can accurately define the osseous anatomy and adaptations of the glenoid. Although CT may not be helpful as frequently in the clinical setting, it may be a useful modality for preoperative evaluation or research purposes.
Decision-Making Principles
As with many of the common pathologic entities that are encountered, decision making in the management of the shoulder used in throwing ideally follows an algorithmic approach, with a foundation of the available evidence and prior clinical experience. In general, the initial management of the great majority of shoulder injuries in overhead throwing athletes is nonoperative, consisting of a period of rest/activity modification and rehabilitation. Rehabilitation efforts are directed at correcting all the observed abnormalities in the kinetic chain from the lower extremity, hip, trunk, scapula, shoulder, and upper extremity.
Wilk and colleagues have described several phases of rehabilitation for overhead throwers with shoulder pain, including the acute phase, intermediate phase, strengthening phase, and return-to-throwing phase. In the first, acute phase, local therapeutic modalities are used to decrease pain and inflammation. Nonsteroidal antiinflammatory drugs, injections, ice, and iontophoresis may be used to accomplish this goal. A key to this phase is discontinuation of all activity to allow the shoulder to rest and the modalities to take effect. Shoulder motion must be normalized during this phase of rehabilitation, which includes treating GIRD. Stretches such as the sleeper’s stretch ( Fig. 50-5 ) are used to treat posterior capsule tightness. The sleeper’s stretch is performed by having the athlete lie on his or her side with the shoulder in 90° of flexion, in neutral rotation, with the elbow also in 90° of flexion. The shoulder is then passively internally rotated by pushing the forearm toward the table around the fixed point of the elbow. GIRD greater than 20 degrees has been shown to be successfully treated nonoperatively. A major focus of the first phase of rehabilitation is improving the strength and muscle balance. Focus is therefore placed on returning strength to the external rotators, scapular, and lower extremity muscles.
The goals of the intermediate phase are to progress with strengthening and enhanced flexibility of the shoulder. More aggressive isotonic strengthening activities are used during the intermediate phase with the goal of improving muscle balance. Focus is placed on strengthening the external rotators, scapular retractors, protractors, and depressor muscles. Wilk and colleagues prefer side-lying external rotation and prone rowing into ER. Strengthening of the lumbopelvic region and core are also a focus of the intermediate phase of rehabilitation. Jogging and sprinting are integrated into this phase as well to improve lower extremity strengthening and endurance. Upper extremity stretching exercises are also continued.
During the third phase of rehabilitation, the goals are to initiate aggressive strengthening drills, enhance power and endurance, perform functional drills and gradually initiate throwing activities. Plyometric drills are also initiated during this phase. These drills are used to enhance dynamic stability, enhance proprioception, and gradually increase the functional stresses placed on the shoulder joint. Dynamic stabilization drills are also performed to enhance proprioception and neuromuscular control. During this phase, an interval throwing program is started. The interval throwing program is started once the athlete has a satisfactory clinical examination, nonpainful ROM, satisfactory isokinetic test results, and appropriate progress in his or her overall rehabilitation program.
Return to throwing is the fourth and final phase of the rehabilitation protocol. This phase typically involves progression of an interval throwing program. Although a number of approaches for this phase have been described with some variation, the general principles emphasize a strategic progression, often over a period of 6 to 12 weeks, during which the athlete progresses from the initial phase, consisting of short throwing over a limited duration to long toss and subsequently to position-specific throwing and/or throwing from the mound. Each step is taken in a careful fashion, and any increase in symptoms prompts a short period of rest combined with a retreat to the prior phase to allow for resolution of symptoms. Once the athlete has accomplished the final phase of position-specific throwing, the decision can be made to return to competition. A judicious return to competition is recommended with careful monitoring of activity, innings, pitch count, and periods of rest aimed at limiting the risk of symptomatic recurrence.
Surgical options should be reserved for cases when nonoperative treatment fails. The surgical procedure necessary is determined by the shoulder pathology that is present; however, the approach in this population is patient specific. All surgical pathology must be considered and managed systematically for optimal recovery of the athlete, which may require several concomitant surgical interventions such as SLAP repair and articular-sided rotator cuff debridement in the example of recalcitrant internal impingement.
Treatment Options
Internal Impingement
Internal impingement is associated with a spectrum of pathology and lends itself to multiple treatment options. Again, with only a few notable exceptions, conservative options should be exhausted in overhead throwing athletes before surgical intervention is considered. In general, indications for surgery in overhead throwing athletes are the same as those in the general public—specifically, failure of symptoms to improve or the inability to return to competitive play despite a dedicated and thorough rehabilitation protocol. The timing of surgery can depend on whether the athlete is currently playing or if his or her playing season is over. An athlete who is currently playing may attempt to treat or manage a structural shoulder injury conservatively to get through the season before undergoing surgery.
Partial-Thickness Rotator Cuff Tears
The treatment of partial-thickness rotator cuff tears depends on several factors, including the depth and location of the tear, the quality of the tissue, and the athlete’s age and playing position. Surgical options include debridement of the rotator cuff tear, tear completion and subsequent full-thickness repair, transtendinous repair, and intratendinous repair constructs. The decision to debride or repair a rotator cuff tear is primarily based on the percentage of tendon thickness that has been compromised. In the general population, the conventional rule of thumb is that a tear of less than 50% thickness is debrided, whereas tears that are of 50% or greater thickness are more suitable for repair. These guidelines have been adopted by several authors for overhead throwing athletes. However, Rudzki and Shaffer recently contended that partial tears in the overhead throwing population may be different than in patients who do not throw. These investigators emphasize that the high forces endured by the rotator cuff and exaggerated positions the arm must be placed in after surgery in an overhead thrower may threaten the repair in this subset of patients. As a result, Rudzki and Shaffer advocate that a partial tear in overhead throwing athletes should approach a thickness of 75% or greater to be considered for repair.
In articular-sided partial rotator cuff tears that do not meet the criteria for repair, an arthroscopic shaver is used to perform debridement to the extent necessary to achieve healthy, stable tissue. When an articular-sided partial tear of 50% to 75% thickness is identified with diagnostic arthroscopy, surgical repair is favored. One option for repair of rotator cuff tears in these patients is completion of the tear and suture anchor–based repair. However, Lo and Burkhart pointed out that after the soft tissue is debrided and brought over laterally to the footprint, a length-tension mismatch of the repaired rotator cuff muscle may occur. Because of these concerns, the authors described a transtendinous approach to articular-sided partial rotator cuff tears that are greater than 50% of the tendon thickness. The technique restores the medial aspect of the footprint while maintaining the lateral footprint of the rotator cuff. This procedure potentially minimizes the length-tendon mismatch.
SLAP Tears
Injury to the superior labrum in overhead throwing athletes can occur in conjunction with other pathologies or in isolation. Understanding the normal anatomic variants of the superior labrum and biceps insertion is critical to recognizing pathologic changes to the structures. In the setting of true pathology to the superior labrum, the type of SLAP tear dictates its treatment. Type I SLAP lesions are characterized by fraying of the central labrum without detachment of the biceps anchors and are treated with debridement. Type II lesions, which consist of isolated detachment of the superior labrum and biceps anchor, are most common and are typically treated with suture anchor repair when the tear is believed to be unstable. A bucket-handle tear is present in type III lesions; these tears are treated with debridement and removal of the bucket-handle tissue. Type IV tear treatment depends on the extent of biceps tendon involvement. If a small percentage (approximately <30% of the tendon) is involved, type IV lesions are typically treated with debridement of the labral tear and its extension into the biceps tendon. Tears involving more than 30% of the biceps tendon generally are treated with biceps tenodesis and labral repair or débridement.
Posterior Capsular Contracture
Posterior capsular contractures respond very well to conservative treatment. Posterior capsular stretching exercises known as “sleeper stretches” are the first-line treatment for throwers with GIRD. Rates of failure of conservative treatment for IR deficit and capsular contracture are exceedingly low, especially in younger pitchers.
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