Throwers, or athletes who engage in repetitive overhead motions, are a unique subset of athletes that experience distinct shoulder injuries. Athletes engaged in baseball comprise the majority of patients seeking orthopedic care for throwing related injuries. Injuries specific to throwers most commonly involve the labrum and the undersurface of the rotator cuff. In addition, tissue changes in both the anterior and posterior glenohumeral capsule are common with repetitive overhead motions. These capsular changes alter. This article will examine the pathomechanics of injuries to throwers, elaborate means of diagnoses of cuff and labral injury and discuss recent advances in both non-operative and operative interventions, including preventative principles.
Key points
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Injuries specific to throwers most commonly involve the labrum and the undersurface of the rotator cuff.
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The act of throwing has been described as occurring in several distinct phases. Of particular importance are the late-cocking, ball release and follow-through phases. These portions of the throwing motion produce the largest forces about the glenohumeral joint, and therefore, the highest injury risk.
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In late-cocking, the anterior capsule is under significant strain in an effort to prevent anterior translation of the humerus. Tensile failure and attenuation of the anterior capsule is thought to occur from repetitive ‘hard throwing’.
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During the follow through phase, the posterior capsule and posterior cuff undergo tremendous eccentric loads – up to 108% of body weight – in order to decelerate the rapidly internally rotating arm and to restrain the significant distractive forces seen at the posterior shoulder joint.
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The thrower’s shoulder is prone to injury secondary to the convergence of the following factors: attenuation of the anterior capsular constraints, acquisition of a posterior capsular contracture, development of scapula dyskinesis, breakdown of the kinetic chain and repetitive contact of the posterior superior labrum and greater tuberosity.
Introduction
Throwers, or athletes who engage in repetitive overhead motions, are a unique subset of athletes who experience distinct shoulder injuries. For purposes of clarity, this article focuses on athletes engaged in baseball, because this patient population comprises most patients seeking orthopedic care for throwing-related injuries. Baseball remains one of America’s favorite pastimes, and children often participate in the sport by the age of 5 or 6 years. The common participation in overhead throwing by today’s youth increases the likelihood of orthopedic surgeons encountering patients with throwing-related shoulder pathology.
Injuries peculiar to throwers most commonly involve the labrum and the undersurface of the rotator cuff. In addition, tissue changes in both the anterior and posterior glenohumeral capsule are common with repetitive overhead motions. These capsular changes alter shoulder kinematics and subsequently contribute to both labral and cuff injury. Furthermore, the glenohumeral joint and the scapula are inextricably linked. In fact, scapular issues may herald the development of tissue breakdown in the shoulder. This article examines the pathomechanics of injuries to throwers, elaborates means of diagnoses of cuff and labral injury, and discusses recent advances in both nonoperative and operative interventions, including preventative principles.
Introduction
Throwers, or athletes who engage in repetitive overhead motions, are a unique subset of athletes who experience distinct shoulder injuries. For purposes of clarity, this article focuses on athletes engaged in baseball, because this patient population comprises most patients seeking orthopedic care for throwing-related injuries. Baseball remains one of America’s favorite pastimes, and children often participate in the sport by the age of 5 or 6 years. The common participation in overhead throwing by today’s youth increases the likelihood of orthopedic surgeons encountering patients with throwing-related shoulder pathology.
Injuries peculiar to throwers most commonly involve the labrum and the undersurface of the rotator cuff. In addition, tissue changes in both the anterior and posterior glenohumeral capsule are common with repetitive overhead motions. These capsular changes alter shoulder kinematics and subsequently contribute to both labral and cuff injury. Furthermore, the glenohumeral joint and the scapula are inextricably linked. In fact, scapular issues may herald the development of tissue breakdown in the shoulder. This article examines the pathomechanics of injuries to throwers, elaborates means of diagnoses of cuff and labral injury, and discusses recent advances in both nonoperative and operative interventions, including preventative principles.
The act of throwing
Throwing a baseball more than 90 mph generates great demands on the shoulder girdle. Humeral angular velocities have been estimated to exceed 7000° per second, with estimated external rotation (ER) torques as high as 67 Nm. The act of throwing has been elegantly described as occurring in several distinct phases. Of particular importance are the late-cocking, ball release, and follow-through phases. These portions of the throwing motion produce the largest forces about the glenohumeral joint and, therefore, the highest injury risk.
In late cocking, the anterior capsule is under significant strain in an effort to prevent anterior translation of the humerus. Tensile failure and attenuation of the anterior capsule is thought to occur from repetitive hard throwing. Throwers demonstrate increased passive ER in the abducted and externally rotated (ABER) position compared with controls. Furthermore, stretching of the coracohumeral ligament (CHL) may also occur during forced ER and explain the rotator interval laxity commonly seen in overhead athletes.
During the follow-through phase, the posterior capsule and posterior cuff undergo tremendous eccentric loads, up to 108% of body weight, to decelerate the rapidly internally rotating arm and to restrain the significant distractive forces seen at the posterior shoulder joint. In time, the continual strains across the posterior cuff may lead to muscular fatigue and thereby a much larger transfer of stress to the posterior capsule. Chronic attritional tearing of the posterior capsule may result in a fibroblastic healing response, increased collagen deposition, and loss of tissue compliance. All these elements converge and are thought to give the overhead thrower a stiff posterior cuff and capsule.
To obtain the great arm velocity required to pitch effectively, throwers must attain increased degrees of ER. The greater the arm can externally rotate, the more time the arm has to accelerate before ball release. Pitchers who are able to pitch at great velocities possess not only great muscle strength and fast twitch muscle capability but also inordinate degrees of ER ability.
Humeral retroversion
Fetal humeri demonstrate significantly greater degrees of retroversion compared with adult humeri, along the order of 78°. During development and growth, retroversion slowly decreases until the adult average of roughly 30° is attained ( Fig. 1 ). Immature throwers, on the other hand, by virtue of Wolf’s law, impose stresses across the proximal humeral physis, which impedes the loss of retroversion. It is not unusual for a thrower, who began pitching in Little League, to present with more than 45° of retroversion in adulthood. There is also a particular asymmetry of the throwing and nonthrowing shoulders. A study in pitchers demonstrated that a the dominant shoulder exhibited increased humeral retroversion (HRT), glenoid retroversion (GRV), ER at 90°, ER in the scapular plane, and decreased internal rotation (IR) relative to their nondominant shoulder. In another study of professional baseball pitchers, the HRT to GRV ratio was found to be 2.3:1 for throwing shoulders and 7:1 for nonthrowing shoulders. The adaptive morphologic changes of increased proximal HRT and GRV in throwing shoulders are thought to be at least initially adaptive. On the contrary, nonthrowing individuals do not display this discrepancy between their dominant and nondominant shoulders.
Increased retroversion resets the clock in terms of the arc of motion for the thrower, in which ER is gained with a symmetric loss of IR. This increased retroversion allows a greater amount of ER to occur before the greater tuberosity abuts the posterior superior labrum in the ABER position. This contact between the greater tuberosity and posterior superior labrum, sustained repetitively, can lead to posterior cuff and labral injury in many throwers. Although this contact, known as internal impingement, has been shown to occur normally in overhead athletes, contact pressures between the posterior cuff and labrum are less than in those throwers endowed with increased retroversion. Those who embrace throwing after skeletal maturity, by virtue of lessened retroversion, may be more susceptible to impingement type injury than a lifetime thrower. However, Thomas and colleagues have posited the increased retroversion may predispose the thrower to increased posterior capsular thickness, which is thought to increase the risk of injury. These investigators found a correlation between posterior capsular thickness and retroversion. That is, the same retroversion thought to be beneficial to throwing velocity and avoidance of cuff and labral impingement may predispose the athlete to posterior capsular contracture, or glenohumeral internal rotation deficit (GIRD). The potential negative effects of GIRD on shoulder kinematics are discussed in more detail.
Pathomechanics
The thrower’s shoulder is prone to injury secondary to the convergence of the following factors: attenuation of the anterior capsular constraints, acquisition of a posterior capsular contracture, development of scapula dyskinesis, breakdown of the kinetic chain, and repetitive contact of the posterior superior labrum and greater tuberosity. Each of these factors has been examined, and strategies have been suggested to prevent injury.
Anterior Capsule
Biomechanical studies demonstrate that the anterior capsule, particularly the anterior band of the inferior glenohumeral ligament, is the primary restraint to anterior translation of the humerus when the arm is ABER. Thus, repetitive stress to this area and the thrower’s unconscious desire to attain extreme ER (the slot) conceivably leads to anterior capsular laxity or attrition. Although the attributed causes are somewhat controversial, throwers do indeed demonstrate more passive ER than in the contralateral arm. If this excessive rotation exceeds that which is expected to occur from increased retroversion, that is, excessive ER gain is greater than IR loss, then the soft-tissue restraint is lax. In support of this notion is the work of Jobe and colleagues, which describes tensioning of the anterior capsule (anterolabral capsular reconstruction) as a means of returning pitchers to throwing. Although this open procedure was successful for many, violation of the subscapularis and excessive tightening potentially explain why not all patients were able to throw at preinjury levels of performance after reconstruction. In a study investigating patients who underwent labral repair, Levitz and colleagues reported that those who underwent subtle thermal shrinkage of the anterior capsule, in addition to superior labral repair, enjoyed greater success than those who had superior labral repairs alone. As anterior laxity evolves, ER increases and further increases contact of the posterior cuff and labrum, thereby facilitating injury. Rizio and colleagues demonstrated increased superior labral strain in cadaveric shoulders placed in the ABER position after surgically creating subtle anterior laxity. These studies lend support to the notion of anterior capsular laxity as one contributing factor to shoulder pathology in the thrower and that HRT is beneficial against anterior capsular attenuation.
In addition, because the CHL is a primary restraint to ER, stretching of the CHL and superior glenohumeral ligament (SGHL) may ensue with repetitive throwing. The thrower may present with increased passive ER with the arm adducted, as well as a positive sulcus sign, inferior shoulder laxity that persists in ER. On arthroscopic examination, interval laxity manifests as a capacious biceps sling, the enclosure of the intra-articular biceps comprising the SGHL, CHL, and supraspinatus insertion. Morgan has posited that interval laxity must be addressed during concomitant labral surgery to increase the likelihood of successful return to throwing (Craig D. Morgan, personal communication, 2013) ( Fig. 2 ). In addition, because the CHL inserts into the deep fibers of the supraspinatus, injury to this structure may be intimately associated with the undersurface supraspinatus tears commonly seen with overhead athletes. Habermeyer and colleagues found lesions of the CHL accompanied by undersurface supraspinatus lesions in 73% of subjects studied.
Posterior Capsular Contracture
With time, throwers demonstrate decreased IR, especially when measured in the abducted position. This diminished IR is thought to occur for 2 reasons. First, as mentioned previously, increases in HRT observed in throwers manifests as a loss of IR. This loss, due to boney remodeling, however, is accompanied by a symmetric gain of ER. This resetting the clock of rotation usually accounts for no more than 10° to 17° of rotational loss. The second means of IR loss is ascribed to a posterior capsular/cuff contracture. This GIRD is thought to occur, as stated previously, as a healing response to chronic distractive forces applied to the posterior capsule during follow-through. Rotational loss due to capsular contracture is evident when GIRD exceeds that which can be explained by boney remodeling alone (more than 12°) and when the internal rotational loss exceeds the external rotational gain as compared with the contralateral shoulder. For example, a young thrower who presents with GIRD of 35° surely has more than increased retroversion to account for internal rotational loss. In a study investigating change in passive range of motion (ROM) and development of GIRD in professional pitching shoulders between spring training in consecutive years, Shanley and colleagues found that even accounting for HRT, ROM was significantly altered between seasons of pitching secondary to soft-tissue adaptations. The finding suggests that some changes in the pitching shoulder may be transient and amenable to modulation. Furthermore, many throwers, particularly less mature athletes, often demonstrate dramatic increases in IR after a dedicated stretching regime. Boney restraints would not respond to stretching programs. In a study investigating the effects of a stretching protocol on passive IR in the throwing shoulders of collegiate baseball players, Aldridge and colleagues found that the posterior capsule stretching program was effective in increasing passive IR, and total ROM, but not on ER in the throwing shoulder. The stretching program had no effect on nonthrowing arm IR, ER, or total ROM.
Biomechanical Consequences of GIRD
Recent clinical and biomechanical studies lend credence to the notion that GIRD may be the sentinel event in the pathologic cascade that many throwers experience. Burkhart and colleagues noted that professional throwers who presented to preseason with GIRD values less than 25°, as compared with the contralateral shoulder, experienced less shoulder difficulties during the ensuing season. Others have noted that throwers who present with superior labral injuries invariably exhibit GIRD generally greater than 25° to 30°. Even small degrees of GIRD place the thrower at increased risk for injury, as evidenced by a study by Wilk and colleagues, which found that pitchers with as little as 5° of GIRD were at higher risk for injury and shoulder surgery.
Cadaveric studies have helped elucidate the association between GIRD and labral or cuff injuries. Clabbers and colleagues imbricated the posterior capsule of cadaveric shoulders and placed them in the late-cocking position. They observed a tendency (nonsignificant) for posterior capsule tightening to encourage relative posterior/superior migration of the humeral head. Grossman and colleagues and Huffman and colleagues elegantly demonstrated the same phenomenon and introduced anterior laxity, in addition to posterior capsular tightness, to a compressively loaded joint, which more closely mimicked the in vivo condition. All 3 studies suggested that posterior capsular tightness, with or without anterior capsular laxity, promoted a relative shift of the humeral head contact point on the glenoid in the ABER position. In another cadaveric model, Gates and colleagues further found that decreases in posterior and inferior translation of the humeral head could be observed with as little as 5% GIRD, further highlighting the importance of the finding.
This shift in contact theoretically brings the humeral head closer to the superior labrum in late cocking, promoting increased contact between the 2 structures. Furthermore, Laudner and colleagues showed that throwers with internal impingement present with significantly more GIRD than asymptomatic throwers. In addition, a more posterior vector could conceivably increase the posterior force on the labrum in late cocking. This increased peel back force may result in a higher incidence of posterior labral injury. Kuhn and colleagues have shown that the posterior labrum is more prone to failure in the late cocking rather than in the follow-through phase of throwing.
The posterior superior shift that occurs with GIRD is thought to result from the inferior tether that posterior/inferior capsular contractures produce. A contracted posterior/inferior capsule does not permit full ER of the humerus. In an effort to find the slot, the thrower begins to rotate around a new instant center of rotation, one that is more posterior and proximal. In essence, a tightened posterior inferior capsule drives the humerus more proximally and posteriorly. Burkhart and colleagues liken this to a yo-yo on a string. In support of this tethering phenomenon, the investigators have noted several pitchers who have presented with both posterior-superior and posterior-inferior labral tears, confirming the notion that GIRD increases both the capsular tether inferiorly and labral shear posterior-superiorly. With the concomitant posterior shift in humeral head contact, an obligatory anterior laxity is thought to occur, owing to the cam-shaped structure of the humerus. Burkhart and Lo describe this as pseudolaxity and has shown that posterior shift in contact point does indeed introduce laxity of the anterior capsule. The same laxity allows the thrower to hyperrotate, promoting even more contact between the posterior labrum and cuff. In addition, hyper ER may introduce excessive strain on the rotator cuff. Hyper twist of cuff fibers may lead to eccentric fiber failure and undersurface tearing.
Scapular Dyskinesis
An abnormality of either the static or dynamic position of the scapula is termed scapular dyskinesis ( Fig. 3 ). The scapula normally accommodates the proximal humerus closely so that a stable platform (the glenoid) and concavity compression of the cuff is optimally attained. Kibler and McMullen likened this relationship to a seal balancing a ball on its nose. With time, throwers may develop scapula dyskinesis, which may, in turn, potentiate further cuff or labral injury.
Origins of Dyskinesis
Muscles commonly respond to proximate joint afflictions with atrophy or contracture. For example, quad atrophy often accompanies knee pain and hamstring tightness often accompanies low-back discomfort. Shoulder pain commonly results in inhibition of the lower trapezius and serratus anterior, as well as tightening of the upper trapezius and pectoralis minor. The net effect of this muscular imbalance is a protracted and anterior tilted scapula, one that deviates away from the midline and anterior to the frontal plane. Because the thorax is ellipsoid, a protracted scapula essentially follows the contour of the rib cage and rests in a relative internally rotated and inferior position. Myers and colleagues noted that throwers who suffer from internal impingement demonstrate increased scapular protraction during humeral elevation. Pink and colleagues has advanced the concept of scapula windup (secondary to GIRD) as a means to increasing scapular protraction. In essence, throwers with loss of capsular IR rely more on scapular IR as a means of attaining follow-through. In time, as the scapula winds up and over the ellipsoid thorax, it loosens its static restraints and perhaps overwhelms dynamic stabilizers. The net effect is a scapula that is deviated from the midline and anteriorly tilted.
Thomas and colleagues have studied adolescent and collegiate pitchers and have noted a temporal relationship between GIRD and dyskinesis. Less mature pitchers developed GIRD without scapular dyskinesis, whereas more mature throwers tended to develop more GIRD and began to manifest scapular changes in the throwing shoulder. GIRD more than 15° seemed to herald the onset of scapular changes. Thus, there seems to be a dose response of GIRD leading to scapular abnormalities.
Effects of Excessive Protraction
There are numerous biomechanical consequences of a protracted or excessively internally rotated scapula. First, a protracted scapula leads to rotator cuff weakness. Because the rotator cuff complex essentially originates on the scapula, a dyskinetic or protracted scapula serves as an unstable platform and does not afford optimal length-tension relationships to the cuff muscles. Kibler’s scapular retraction test affirms the importance of scapula position in optimizing cuff strength. To perform the test, an examiner checks supraspinatus strength, testing both with and without manual stabilization of the medial border of the scapula against the thorax. Patients with dyskinesis of the scapula demonstrate increases (often striking) in strength on affixing the medial border of the scapula to the thorax. Second, increased protraction anteverts the glenoid, virtually uncovering the humeral head anteriorly and thereby leading to anterior destabilization and increased strain on the anterior ligaments. Excessive protraction also increases the degree of impingement between the posterior superior glenoid and posterior rotator cuff by positioning the posterior glenoid closer to the greater tuberosity during ER and horizontal abduction. Increased pinching or contact of the posterior superior glenoid and posterior supraspinatus occurs more readily in an anteverted glenoid. Supporting this fact, Laudner and colleagues demonstrated that throwers with pathologic internal impingement exhibit a more protracted scapula. This internal impingement can result in posterior shoulder pain and potentiate posterior labral or cuff injury.
Kinetic chain breakdown
Rubin describes a kinetic chain as a series of links, acting sequentially, to generate a force. The image of cracking the whip illustrates how proximal links (the handle and base of the whip), when acting in unison with more distal aspects or segments of the whip, can produce a great force distally. Similarly, throwers generate great velocities by linking force generated by the lower extremity and core muscles funneled via the shoulder to the arm. The lower extremities generate more than 50% of the kinetic energy of the throw. Any break in the chain, from feet to fingers, results in loss of velocity and catch up demand in more distal links. For example, weak hip abductors on the stance leg or, more commonly, the stride leg of throwing creates an unstable base from which to throw. A recent kinematic and kinetic investigation of collegiate and professional pitchers found that increased time in lower extremity and trunk phases of the throwing motion not only decreased the magnitude of upper extremity kinetics linked to overuse injuries but also correlated with decreased ball speed. In accordance with the distal catch up principle to maintain velocity, increased demand is placed on the more distal shoulder and elbow segments. Similarly, loss of IR of the shoulder promotes increased reliance on the more distal elbow and wrist links to produce the long axis IR necessary to complete a throw. Suzuki and colleagues have demonstrated that scapula fatigue results in increased elbow demand in the act of throwing. The hip has also received more recent attention, as it pertains to throwing. Femoracetabular impingement of the hip necessarily diminishes IR of both lead leg and trail legs for a thrower. It has been posited that such deficits in motion translate to increased distal kinetic chain breakdown. Byrd has described the positive effects of hip arthroscopy on restoring throwing ability in athletes.
It is imperative for the examiner to discern subtle breakdowns of the kinetic chain. The following often unnoticed kinetic chain abnormalities have been called to attention: ankle stiffness or instability, loss of IR of the lead leg, lumbar spine inflexibility, psoas tightness, and hip abductor weakness. Spinal inflexibility, especially accentuated lumbar lordosis, may force the torso to become positioned anterior to the arm during late cocking. This, throwing out of the scapular plane, as mentioned previously, potentiates posterior cuff and labral contact.
Diagnosis of cuff and labral injury in the thrower
History
Throwers usually present with chief complaints of pain, loss of velocity or control, or mechanical symptoms of clicking or locking. These symptoms suggest cuff and/or labral injury. Tenderness is usually seen posteriorly and may reflect posterior labral tear or posterior cuff irritation. Anterior pain on palpation (less common) may indicate an anterior labral disruption or leading edge of the supraspinatus lesion. Anterior/medial pain, coursing in the subpectoral region, is more consistent with biceps tendon pathology. Night pain, especially pain lying on the ipsilateral shoulder, usually reflects rotator cuff involvement.
The loss of zip or an inability to find the slot during throwing may be due to labral or cuff damage, with subsequent abnormal mechanics. Kinetic chain breakdown may cause errant control. For example, loss of IR of the lead leg may cause the athlete to open up prematurely during late cocking and thereby generate a loss of pitch accuracy.
Often, the thrower relays a history of an event, or single pitch after which their throwing was never the same. The event may be described as a sudden dead arm during late cocking or merely one pitch, which elicited an inordinate amount of pain. These abrupt changes in symptoms may indicate a slap event and often indicate mechanical tissue failure.
Examination
Physical examination of the thrower must include all aspects of the kinetic chain and evaluation of scapula position.
Because proper conditioning of the trunk and lower extremity musculature is essential for the transfer of energy from the lower extremity to the upper extremity during the pitching motion, pathology involving the spine, trunk, and lower extremities can ultimately affect the upper extremity and predispose the athlete to injury. A comprehensive shoulder examination, therefore, begins with a brief trunk and lower extremity examination. While standing, the athlete is examined for spinal mobility by asking him or her to touch their toes with knees straight and to perform side bends. Hip abductor strength is assessed by asking the athlete to perform multiple single-leg squats on the stance leg and stride leg. Dipping of the pelvis or knee valgus during this maneuver indicates gluteus medius weakness and a significant proximal kinetic chain breakdown.
No shoulder examination is complete without a scapular examination, and the athlete is asked to remove the shirt if man or don a tank top if woman for optimal inspection. Kibler’s scapular slide is useful in noting scapula position both at rest and under provocation. The posterior shoulder can be effectively examined with the athlete’s hands at sides and with resisted arm forward flexion, to elicit serratus anterior weakness. Any asymmetry of scapular position of the left versus the right shoulder indicates dyskinesis of the scapula. Although Kibler and colleagues espoused a 4-part classification for scapular dyskinesis, it is only moderately reliable in symptomatic patients and was shown to have low reliability in healthy patients. Regardless, care must be taken to carefully examine the scapula position, as the presence of scapular dyskinesis frequently indicates a kinetic chain abnormality, a continued painful stimulus, or persistent anatomic lesion (ie, labral/cuff injury). True scapular pathology must be associated with pain or dysfunction. As Tate and colleagues have indicated, the relief of symptoms with scapular assistance or relocation denotes true scapular dysfunction. Milder degrees of scapular asymmetry may, in fact, be adaptive responses to the thrower’s demands and should not necessarily be treated in the absence of pain of dysfunction.
The examination continues with the athlete sitting, whereby tenderness of the joint, anterior cuff, bicipital groove, acromioclavicular joint, and coracoid may be noted. Rotator cuff strength, especially that of the supraspinatus, is elicited.
Although the specific utility of many special shoulder tests is often controversial, several must be highlighted in the physical examination of the thrower’s shoulder. The empty can test, which involves resisted downward pressure of the forward-flexed arm in the scapular plane, is effective in assessing general supraspinatus strength. The Whipple test, which involves resisted downward pressure of the adducted, forward-flexed arm allows for assessment of the anterior edge of the supraspinatus tendon. The scapula retraction test indicates whether or not cuff weakness may be secondary to a malpositioned, protracted scapula. To perform this test, the examiner manually affixes the medial scapular wall to the thorax and notes if suprasinatus weakness and/or internal impingement pain of the ABER position is corrected with improved scapula position. The apposition of the scapula against the chest wall literally corrects scapula protraction and restores the stable platform necessary for cuff strength. Furthermore, less protraction moves the posterior labral/cuff complex away from the greater tuberosity in ABER.
Several physical examination maneuvers are also useful in assessing the integrity of the thrower’s labrum. The O’Brien test, which involves resisted downward pressure to the 90° forward-flexed, slightly adducted, and internally rotated arm, may be useful in the detection of anterior labrum tears. Anterior joint line tenderness may denote an anterior labral lesion, while posterior joint line tenderness may indicate posterior labral injury or irritation of the posterior cuff. Anterior joint line tenderness similarly may denote an anterior labral lesion. The examination continues with the Mayo shear test, whereby the abducted, externally rotated arm is hyperextended and brought down to adduction. This position may literally shear the posterior labrum in the presence of GIRD and/or anterior laxity. The presence of significant pain during this maneuver, especially at or near 100° of abduction, may indicate posterior labral injury.
The examination continues with the patient in the supine position, whereupon the presence of IR deficit is discerned by stabilizing the scapula in abduction and internally rotating the humerus. Differences between affected and unaffected sides are noted. A discrepancy of more than 20° may indicate a shoulder at risk. Passive ER ROM in both adduction and abduction may indicate subtle interval and anterior capsular laxity, respectively. The relocation test is performed with the patient in the ABER position with humeral extension. Posterior pain relieved with a posteriorly directed force can indicate a posterior Superior Labrum Anterior to Posterior (SLAP) tear, internal impingement, or anterior capsular laxity.
The final sequence of the examination is conducted with the patient in the lateral decubitus position, where a variation of the load shift test is performed. The examiner grasps the wrist with one hand and positions the arm in roughly 20° of forward flexion and 45° of abduction. With the other hand, he or she levers the humeral head anterior/inferiorly with the thumb so that the head rides over the glenoid rim. Next, the examiner abducts and externally rotates the arm, while maintaining pressure with the other thumb, and determines if the humeral head relocates. Failure to relocate in ABER, or the presence of a significant click or clunk, may indicate capsular or labral incompetency. The examination is repeated for the middle glenohumeral ligament (MGHL) by levering the humerus anteriorly and recruiting the MGHL by abducting the arm to 45° with ER. This examination is difficult to master but may reward the examiner with helpful information regarding the competency of the anterior capsular-labral tissues. Kim’s test and the jerk test can also be performed to assess the competency of the posterior inferior and posterior labrum, respectively. A variation of the jerk test, with the arm in lesser degrees of abduction, may sometimes also detect subtle posterior/superior labral lesions. Finally, the newly described passive compression test by Kim for superior labral tears uses the peel back phenomenon to elicit pain. The arm is abducted to approximately 30°, and maximal ER is applied. As the arm is extended, the humerus is forcibly pushed superiorly to further strain the superior labral/glenoid junction.
The panoply of labral tests available to the orthopedist can certainly cause confusion as to determining which test is the most useful. A systematic review with meta-analysis found that no single shoulder physical examination test could be relied on to make a pathognomonic diagnosis. Furthermore, not one of the 8 physical examination maneuvers examined revealed a sensitivity that would allow a physician to rule out an SLAP lesion after a negative test. That being said, other groups have shown success in combining physical examination maneuvers to improve diagnostic sensitivity. For example, a sensitivity analysis of physical examination and magnetic resonance imaging (MRI) findings found that, although the sensitivity of O’Brien test was 90%, the Mayo shear test was 80%, and Jobe relocation test was 76%; the sensitivity of a physical examination with any 1 of these 3 SLAP provocative tests being positive was 100%. This point is critical, as it emphasizes the importance of a complete physical examination, even if individual tests may fail the examiner.
Imaging
Critical to obtaining a complete picture of a thrower’s shoulder pathology is, of course, diagnostic imaging. Routine radiographs, including a true anteroposterior, axillary, and outlet views, are usually unremarkable; however, the presence of greater tuberosity cystic changes or, more reliably, a greater tuberosity notch has been associated with articular-sided rotator cuff tears. The most useful imaging study is the magnetic resonance arthrogram, with most investigators indicating superior detection of subtle cuff and labral injuries over standard MRI. The addition of the ABER view adds important information regarding the status of the supraspinatus tendon and the integrity of its deep surface.
Despite advances in imaging, arthroscopic evaluation remains the gold standard in diagnosis of superior labral and subtle cuff injury. Furthermore, although physical examination and imaging are usually accurate in delineating labral pathology, combined tears are often only discovered intraoperatively.
Nonoperative Treatment
Treatment of the thrower’s shoulder begins with conservative measures. Overt mechanical, labral symptoms, such as locking, catching, or grinding indicates the need for arthroscopic evaluation.
Posterior capsular contracture and rotator cuff tightness must be addressed and are best relieved with a dedicated posterior shoulder stretching and mobilization program. Stretches must isolate the glenohumeral joint so that scapular compensation is minimized. The sleeper stretch, whereby the patient lies on the affected shoulder to stabilize the scapula and internally rotates the abducted arm until resistance is felt is particularly effective. Performance of the stretch in 60°, 90°, and 120° of abduction is recommended, and exercises should be performed at least twice daily. Joint mobilizations can be performed by athletic trainers or physical therapists in a posterior or posterior/inferior direction to target the contracted portion of the capsule.
Kinetic chain evaluation is essential, and subtleties such as lumbopelvic stiffness, hip flexor tightness, hip abductor weakness, and lead leg loss of IR must be investigated. Once each of the above-mentioned areas demonstrate improvements, lower extremity and upper extremity exercises should be incorporated together to stimulate functional movement patterns.
Scapular dyskinesis, usually present, can often be treated with exercises to help restore scapular ER and posterior tilt. The first step in scapular rehabilitation should focus on neuromuscular reeducation of the scapular stabilizing muscles. Strengthening should not be the primary focus until proper muscular control and firing patterns are reestablished. Serratus anterior strengthening can be achieved with push-ups with a plus and low rows ( Fig. 4 ). Lower trapezius strengthening can be attained with prone horizontal abduction and side lying forward flexion and ER. Other scapula retraction exercises, such as close grip rowing, can help maintain the medial scapula affixed to the thorax. A recent cadaveric study demonstrated that the greatest changes in pectoralis minor length were observed with scapular retraction and 30° of flexion. Pectoralis minor stretches, best performed supine, can further help reposition the scapula into a more physiologic position. Because of the triceps originating on the inferior glenoid neck, it often becomes tight in throwers. Therefore, stretching into forward flexion with the scapular stabilized is often required.
