Introduction/Pertinent Anatomy
As youth sports participation continues to increase, there has been a corresponding increase in the amount of injuries seen, especially shoulder injuries in overhead athletes. Traumatic injuries such as fractures are common across the spectrum of competitive sports. Overuse injuries, however, tend to predominate in the pediatric throwing athlete and comprise approximately 60% of all sports injuries in children and adolescents.
Baseball and throwing in particular has been the focus of extensive research with regards to shoulder injuries. The incidence of shoulder pain and symptoms ranges from 32% to 35% within a season of youth baseball and the incidence of injury for pitchers has been shown to be 37.4% versus only 15.3% for position players.
Throwing places a significant amount of stress on the shoulder and overhead athletes require a delicate balance between shoulder mobility and stability to meet the functional demands of their sport. During pitching, peak angular velocities of the humerus have been recorded up to 7550 degrees/second, the generation of internal rotation torques have been reported as high as 67–92 Nm, and it has been demonstrated that a compressive force of up to 1090 N is produced on the shoulder.
Although youth athletes may present with many of the same complaints as more mature athletes, differences in anatomy and throwing technique often leads to age-specific injuries. Injuries in youth throwing athletes are typically caused by repeated stress and cumulative trauma to the developing physis of the proximal humerus as well as adaptive changes in the soft tissue stabilizers of the glenohumeral joint.
In pediatric athletes, the proximal humerus growth plate typically remains open until 14–16 years old in girls and 16–18 years old in boys. Open physeal plates, increased joint laxity, and underdeveloped musculature about the shoulder are three unique aspects of the developing skeleton that lead to inherent susceptibility for injuries in the pediatric overhead athlete.
Similarly, in adults, the rotator cuff muscles, long head of the biceps, and scapular stabilizers contribute dynamic stability to the shoulder joint, while the capsule and ligaments of the glenohumeral joint provide static stability to the shoulder. The static stabilizers function primarily at the extremes of motion and different portions of the capsule tighten depending on the position of the athletes arm.
The anterosuperior capsule, superior glenohumeral ligament, and other rotator interval structures function to limit inferior and posterior translation of the humeral head with the arm adducted. The middle glenohumeral ligament functions to limit anterior–posterior translation in the midrange of abduction and external rotation (∼45 degrees). The inferior glenohumeral ligament functions to limit anterior–posterior translation in the abducted (90 degrees) and maximally externally rotated arm. The posterior capsule does not have any direct posterior ligamentous reinforcement but is important in limiting posterior translation in the adducted, internally rotated, and forward-flexed arm.
Little League Shoulder
Background/Epidemiology
Little league shoulder (LLS) is an overuse injury of the shoulder (specifically the physis) in youth athletes that presents as pain and is accompanied by radiographic evidence of widening of the proximal humeral physis. In 1953, Dotter first described it in a case report in the Guthrie Clinical Bulletin. Since then, it has been described by numerous authors and referred to as osteochondrosis of the proximal humeral epiphysis, proximal humeral epiphysiolysis, or as a rotational stress fracture of the proximal humeral epiphyseal plate.
Pediatric overuse injuries are most common in children between 11 and 16 years old with LLS presenting most commonly at age 13–14 years in boys. Although most commonly seen in male baseball pitchers, LLS can also occur in females, catchers, baseball position players, and other overhead athletes such as tennis players, quarterbacks, and cricket players.
The inherent susceptibility of the developing shoulder plays a predominant role in the development of LLS. Additionally, poor throwing technique or mechanics also increases susceptibility. Other risk factors include the quantity and frequency of pitches thrown, the pitch type, muscular imbalance, and glenohumeral internal rotation deficits (GIRD). In a study by Heyworth et al., almost one-third of patients with LLS had GIRD on physical exam and the odds of recurrence in this subgroup were 3.6 times greater than in those without GIRD.
As the incidence of LLS is increasing, it is important for practitioners to be aware of this condition when considering the spectrum of disorders that affect the pediatric shoulder. Additionally, educating players, parents, trainers, and coaches on risk factors along with the symptoms, such as shoulder fatigue, pain, and decreased velocity, may help identify LLS earlier and lead to prompt and appropriate treatment.
Mechanism/Pathophysiology
LLS is the result of repetitive microtrauma to the physis of the proximal humerus. Skeletally immature athletes tend to develop stress reactions of the proximal humeral physis, as the physis is the weak point in the upper arm compared with the surrounding bony, muscle/tendinous, and ligamentous structures. Additionally, epiphyseal growth cartilage is more susceptible to injury by repetitive microtrauma than is adult cartilage and the growth plate is also especially weak during periods of rapid bone growth, such as puberty.
Within the physis, the zone of hypertrophy tends to be the affected area due to its vertically oriented columns of cells and collagen fibers with little structural matrix, thus making it the weakest portion of the growth plate and most susceptible to injury.
Two major types of loading have been implicated in the pathogenesis of proximal humeral epiphysiolysis. The first and most important is rotational stress or torque applied to the physis during throwing, which can result in repetitive trauma, possibly causing a fatigue fracture or a local inflammatory reaction to the growth plate. The second is a distraction force on the physis at the time of ball release. In response to this distraction force, the rotator cuff muscles contract to create a proximally directed force on the humeral head to keep the glenohumeral joint intact.
A biomechanical study of youth baseball pitchers by Sabick et al. showed that shear stresses on the physis arising from high torque during throwing were approximately 18 Nm or equivalent to 400% of the shear force that growth plate cartilage can normally tolerate and large enough to cause deformation of the weak proximal humeral epiphyseal cartilage. Therefore, proximal humeral epiphysiolysis or LLS is the pathological response to these stresses over time and results in clinical symptoms.
Presentation/Clinical Evaluation
Patients typically present with diffuse shoulder pain during throwing that is often worse in the late cocking or deceleration phases. Rest usually relieves the pain but some patients may progress to having pain with activities of daily living or even at rest. Initially, patients may also complain of a decrease in velocity or control while throwing.
On examination, there is often a focal tenderness or pain over the anterolateral shoulder at the level of the proximal humerus physis. There may be swelling, weakness, atrophy, and loss of motion in the involved shoulder; however, these are all uncommon and nonspecific findings in LLS. Shoulder motion, flexibility, and strength should be examined along with evaluating for scapular dysfunction and assessing other components of the kinetic chain. Additionally, clinical evaluation and provocative testing to exclude other potential causes of shoulder pain in the throwing athlete should also be assessed as clinical suspicion warrants.
Imaging
X-rays of the symptomatic shoulder should be obtained and will classically show physeal widening and possibly some increased sclerosis, demineralization, metaphyseal calcification, or fragmentation adjacent to the physis ( Fig. 25.1 ). These findings tend to be most identifiable in the anterolateral region of the physis, so an external rotation view of the shoulder may be helpful in addition to an AP view. Contralateral shoulder X-rays are also recommended for comparison to help confirm the diagnosis.
Advanced imaging, such as an MRI, will show edema around the physis but it is typically not necessary and reserved for patients with refractory cases or those with instability, where it may be used to rule out other pathology, such as a labral tear.
Treatment
Different from adult throwing injuries that often require surgery, conservative treatment of LLS is highly effective. Please see the rehabilitation section later for a detailed discussion of physical therapy treatment.
Shoulder Instability
Background/Epidemiology
Anterior shoulder instability is a common problem in pediatric athletes that most often results from a traumatic episode and is more commonly seen in contact and collision sports rather than in overhead athletes. The throwing athlete more commonly may present with anterior microinstability or multidirectional instability.
The overhead athlete is presented with a unique paradox in which there is a fine line between ideal excess laxity to allow for full range of motion (ROM) while throwing and instability leading to subluxation of the humeral head. Microinstability is subtle, atraumatic asymmetry of glenohumeral translation in the overhead athlete that may lead to impingement findings and pain secondary to this laxity. Multidirectional instability (MDI) is defined by atraumatic glenohumeral instability in at least two planes, arising from weakness of the joint capsule and surrounding rotator cuff muscles.
It is estimated that 4%–13% of the pediatric population exhibits some degree of joint hypermobility, although this incidence may be even higher in youth overhead athletes due to overuse and adaptive changes. Although not all athletes with hypermobility suffer from shoulder instability, some throwers experience recurrent subluxations that gradually stress and lengthen their capsule and ligamentous structures, leading to symptomatic microinstability or multidirectional instability.
Mechanisms/Pathophysiology
Although traumatic anterior shoulder macroinstability is typically caused by an anterior directed force on the arm while the shoulder is in abduction and external rotation, microinstability and multidirectional instability are not typically caused by a single traumatic event. Their underlying mechanism is either microtrauma from overuse or due to generalized ligamentous laxity that may be associated with a connective tissue disorder such as Ehlers–Danlos syndrome. However, it is important to note that children frequently display greater shoulder laxity compared with adults due to an increased proportion of type III collagen in their ligaments.
Anterior microinstability can develop from repetitive throwing, as external rotation during the overhead motion places tremendous stress on the anterior capsule and ligamentous structures leading to ligamentous laxity overtime. Initially, the periscapular and rotator cuff muscles can compensate but these dynamic stabilizers fatigue with repetitive activity and anterior translation ensues with subsequent development of instability.
Although the exact pathogenesis of symptomatic multidirectional instability is still unclear, it can be postulated that inherent laxity and instability in the youth shoulder may predispose these patients to symptomatic chronic instability when combined with the repetitive overhead stress of throwing. Affected athletes typically possess underlying laxity that is exacerbated by repetitive traumatic insults, resulting in the inability to maintain dynamic stability.
Both MDI and microinstability can lead to secondary impingement syndrome, a condition in which it is difficult for the humeral head to stay centered in the glenoid fossa while the arm is in motion, due to ligamentous laxity and weakness in the rotator cuff muscles.
Presentation/Clinical Evaluation
In overhead athletes with microinstability or MDI, symptom onset is usually gradual, atraumatic, and may correlate with an increase in training. Patients are usually most symptomatic during late arm cocking and early acceleration phases, when the arm is in maximal external rotation. Their chief complaint is often pain more than instability but they may have a subjective feeling of laxity with overhead activities or complaints of popping or catching. MDI patients may also experience concomitant recurrent transient episodes of numbness, tingling, and weakness in the affected extremity, while microinstability patients often have findings of rotator cuff inflammation and impingement secondary to underlying recurrent microinstability.
Examination of the shoulder should reveal instability in two or more planes to be defined as multidirectional instability, while in patients with microinstability more subtle asymmetries of glenohumeral translation between the affected and unaffected side may be present.
Both shoulders should be evaluated and any signs of scapular dysfunction should be noted. Some specific tests to be performed include the following:
- •
The Sulcus Sign—Visible indentation is created between the acromion and the lateral deltoid/humeral head when inferior traction is pulled on the arm
- •
Apprehension Testing—With the patient supine, the examiner flexes the patient’s elbow to 90 degrees and abducts the patient’s shoulder to 90 degrees, maintaining neutral rotation. The examiner then slowly applies an external rotation force to the arm to 90 degrees while carefully monitoring the patient. Patient apprehension from this maneuver is considered a positive test
- •
Relocation Test—This test is administered as a second part to a positive Apprehension test. With the arm still in 90 degrees of abduction and external rotation, the examiner applies a posteriorly directed force to the shoulder. If the patient’s apprehension is reduced, the Relocation test is considered to be positive
- •
Anterior and Posterior Load and Shift tests—With patient seated or supine, the examiner stabilizes the scapula, axially loads the humerus, and applies anterior/posterior translation forces. This should then be compared to the contralateral side. The test is positive when there is greater than 50% movement of the humeral head or increased translation compared to the contralateral side.
Testing for generalized ligamentous laxity should also be performed using the Beighton nine-point scoring system for hypermobility. This involves testing the patient’s ability to touch their palms to the floor while bending at the waist, testing for hyperextension of the knees, elbows, and MCP joints, and testing for the ability to abduct the thumb to the ipsilateral forearm.
Imaging
Although X-rays and MRI are often ordered, imaging usually will not demonstrate significant abnormalities, underscoring the importance of the history and physical exam.
As with LLS, AP radiographs should be taken in both internal and external rotation, but additional axillary and scapular Y views can also be helpful to rule out proximal humeral physeal fractures and other bony pathology.
MRI, specifically MR arthrogram with the addition of intraarticular contrast, may provide a more diagnostic image of the shoulder with instability; however, routine use of an MRI for instability secondary to overuse is not needed unless the clinician suspects associated damage. Notable findings may include a patulous and expanded joint capsule and an increased rotator interval. Additionally, labral tears and/or other intraarticular pathology can be ruled out.
Treatment
Nonoperative
See the rehabilitation section of this chapter later.
Operative
Most cases of instability in the pediatric throwing athlete can be successfully treated nonoperatively with activity modification and an inclusive physical therapy program. If the patient continues to be symptomatic after a 6-month trial of nonoperative management, surgical intervention for stabilization is an option.
Traditionally, stabilization was accomplished via an open technique and performing an inferior capsular shift to minimize capsular redundancy. Despite the elimination of instability and good return of functionality, return to play at preoperative levels was only found in 69% of patients. However, as arthroscopic surgery and techniques have improved over time, most are now occurring arthroscopically. In contrast to open surgery, arthroscopic capsulorrhaphy allows improved access to all portions of the joint, allows the surgeon to address anterior, inferior, and posterior disease at the same time, and minimizes postoperative external rotation loss, which is critical in the overhead athlete. Newer arthroscopic suture anchor techniques also allow the surgeon to tighten the capsule and attach it to the glenoid rim.
The results of arthroscopic treatment have been encouraging for those subset of patient’s that have failed nonoperative treatment, with recurrence rates reported between 2% and 12% and with improved patient satisfaction and return to sport compared with traditional open techniques. In a study by Baker et al. that assessed 2–5-year clinical outcomes, most patients had good to excellent pain scores, 91% of patients had full or near full ROM, 98% had normal or near normal strength, and 86% of patients were able to return to sports.
However, it is important to note that in adolescents with connective tissue disorders, such as Ehlers–Danlos syndrome, results are not as optimistic, with return to play at 64% and only 47% reporting no further episodes of instability at 8-year follow-up.
Post-Op Rehab
Rehabilitation after surgery is outlined in detail later within the rehabilitation section of this chapter.
SLAP Tears
Background/Epidemiology
Superior labral anterior–posterior (SLAP) lesions are another pathology seen in overhead athletes, although much less common in younger patients. A study of 490 baseball players ranging from 13 to 22 years old revealed that players’ ages 13–15 had only a 5.2% incidence of SLAP injury, which is significantly lower than high school and college aged throwers. In contrast to younger athletes, mature throwers more often develop disorders of the superior glenoid labrum, as once the proximal humeral physis closes, the static and dynamic stabilizers of the shoulder are more likely to be injured.
Other risk factors that can predispose the adolescent athlete for the development of a superior labral injury include alterations in shoulder and scapular motion. Although it is controversial whether an incidental finding of GIRD is a measure of injury risk, studies have shown that throwers with GIRD of at least 18 degrees had a 1.9× higher risk of a shoulder injury including SLAP tears.
SLAP tears were originally classified by Snyder in 1990 and although others, such as Maffet, have expanded his classification, the original Snyder classification remains the most widely recognized and describes four major variants.
Type I lesions involve labral fraying with localized degeneration. The superior labral and biceps anchor attachments remain intact.
Type II lesions involve detachment of the superior labrum/biceps anchor complex from the glenoid. They have abnormal mobility and are the most common and clinically significant SLAP tear in overhead athletes.
Type III lesions involve a bucket handle tear of the superior labrum with an intact biceps tendon anchor (biceps separates from bucket handle tear).
Type IV lesions also involve a bucket handle tear of the labrum but have extension of the tear into the biceps tendon. This often creates a split appearance of the biceps tendon with a portion attached to bucket handle tear and a portion remaining attached to the glenoid.
Mechanisms/Pathophysiology
A variety of injury mechanisms have been proposed for SLAP tears including forceful traction loads to the arm, direct compression loads to the arm, and repetitive overhead throwing activities.
The strength of the superior labrum–biceps complex has been examined in multiple studies simulating overhead throwing and these studies have shown that the stability of the biceps anchor and pattern of injury is dependent on shoulder position. SLAP tears are most frequently shown to occur in the late cocking position with one cadaver study showing that the biceps anchor demonstrated 20% less strength in the late cocking phase than in the early deceleration phase. Another study examining simulated loads on the biceps because of throwing showed that strain in the superior labrum was significantly increased in the late cocking phase.
Several factors predispose the overhead athlete to SLAP tears. This includes increased external rotation of the shoulder, which creates a dynamic “peel back” of the biceps anchor during the late cocking phase, resulting in a torsional force at the posterior superior aspect of the glenoid labrum. The labrum and biceps displace medially (“peel back”) over the glenoid rim with each throw and this leads to attritional tears. Additionally, in patients with GIRD, there is increased stress on the labrum from altered glenohumeral kinematics. The posterior capsular contracture seen in GIRD leads to abnormal posterosuperior positioning of the humeral head on the glenoid during arm rotation and creates shear forces across the posterosuperior labrum that can lead to the development of an SLAP tear.
Presentation/Clinical Evaluation
Throwers with an SLAP tear typically present with an insidious onset of shoulder pain, most often during the late cocking phase, and this may be associated with a decrease in velocity or “dead arm.” Patients may complain of a dull aching sensation within the joint, a catching feeling when throwing, and/or difficulty sleeping because of shoulder discomfort. However, the pattern and location of pain are often nonspecific. The pain may localize deep within the shoulder or radiate to the anterior or posterior aspects of the shoulder, mimicking symptoms from biceps pathology, anterior and posterior labral tears, or acromioclavicular joint disease. Typically, the symptoms are worse not only with throwing and overhead motion but with heavy lifting and pushing.
The clinical diagnosis of SLAP tears on physical examination is often difficult, as patients with SLAP tears frequently have coexistent pathology and examination tests to detect SLAP tears lack sensitivity and specificity. Additionally, studies of provocative testing have mainly been performed in the adult population, and further studies are needed to appreciate their utility in the youth athlete. Two of the most commonly used maneuvers for evaluating patients with suspected SLAP tears include the O’Brien’s active compression test and the dynamic labral shear test.
The active compression test (O’Brien) is performed by forward flexing the affected arm to 90 degrees. The arm is then adducted 10–15 degrees across the body and then pronated, so the thumb is pointing down. The examiner applies downward force to the wrist while the patient resists. The patient then supinates the forearm so the palm is up and the examiner once again applies force to the wrist while the patient resists. A positive test for SLAP tear is when there is pain “deep” in the glenohumeral joint while the forearm is pronated but not when the forearm is supinated.
The dynamic labral shear test was developed by Dr. O’Driscoll and reproduces the shearing mechanism that can cause SLAP tears. It is performed by standing behind the patient, holding the wrist of the patient with one hand and applying an anteriorly directed force on the proximal humerus near the joint line with the other hand. The patient’s arm is then elevated in the plane of the body from the side to maximal abduction. The test is considered positive when the patient reports pain or the examiner feels a click in the patient’s posterior shoulder between 90 degrees and 120 degrees of elevation.
Imaging
Diagnostic imaging is often helpful in confirming an SLAP lesion in a youth athlete who continues to experience symptoms after nonoperative treatment.
Radiographic evaluation includes standard views of the shoulder to identify any other potential sources of shoulder pain while an MRI is the preferred imaging modality for patients with suspected SLAP tears ( Fig. 25.2 ). An MRI is also helpful in identifying other abnormalities that frequently coexist in the shoulder.
Distinguishing SLAP tears from normal variable anatomy of the anterosuperior labrum can be difficult, and the sensitivity and specificity have been reported to range from 84% to 98% and 63% to 91%, respectively. The accuracy of MRI may be improved with the addition of contrast into the joint, with one study showing that MR arthrograms have a sensitivity of 90%.
Findings suggestive of an SLAP tear on MRI include high signal intensity and intraarticular contrast extension under the superior labrum/biceps root on coronal images and anteroposterior extension of high signal intensity at the superior labrum on axial imaging.
Treatment
Nonoperative
Nonoperative treatment for SLAP tears is discussed in detail later within the rehabilitation section of this chapter.
Operative
When a period of rest and physical therapy does not resolve symptoms, surgery may be indicated. However, indications for surgery are variable and dependent on multiple factors, as surgery does not always reliably restore overhead athletes to their preinjury level of function. In one study of 40 overhead athletes following type II SLAP repair, 90% of patients had good to excellent results but only 75% returned to their preinjury sport level. In another study, return to play was 73% for all athletes but only 63% for overhead athletes. Athletes with SLAP tears who are able to perform at a high level are generally allowed to finish a competitive season, while early intervention is considered in athletes with evidence of concurrent suprascapular nerve compression secondary to a paralabral cyst.
Surgical treatment of SLAP lesions is performed arthroscopically. During surgery the superior labrum is examined for erythema and probed for signs of detachment and abnormal mobility to decide if repair is indicated. Type I lesions are treated with debridement when they are significantly frayed but such lesions do not necessarily require treatment. Unstable type II lesions should be repaired when the history and exam are consistent with an SLAP tear in young athletic patients. In contrast type II degenerative tears associated with other shoulder lesions in older less active patients do not require repair. Type III lesions are treated with resection of the unstable labral fragment and repair of the middle glenohumeral ligament (MGHL) if the ligament is attached to the torn fragment. Type IV lesions are generally treated with labral repair and biceps repair. Depending on the extent of trauma to the biceps tendon, biceps debridement, repair, tenodesis, or tenotomy may be required.
Surgical repair involves freeing up the tear, debridement of the articular cartilage above the face of the glenoid to create a bleeding bony bed for healing, and placement of suture anchor fixation. Although biomechanical studies have presented conflicting data regarding the ideal suture anchor configuration for SLAP repairs, it is important to note that the biceps anchor has some normal physiologic motion and over constraint during repair may contribute to postoperative stiffness.
Additionally, normal anatomic variations of the anterosuperior labrum are important to distinguish from pathologic conditions, as errant repair can result in a significant loss of external rotation. The three main normal variations include a sublabral foramen (3.3% patients), a sublabral foramen with a cord-like MGHL (8.6% patients), and an absent anterosuperior labrum with a cord-like MGHL, also known as a Buford complex (1.5% patients).
Post-Op Rehab
Rehabilitation after surgery is outlined in detail later within the rehabilitation section of this chapter.
Rehabilitation Overview
The key to successful rehabilitation of the youth throwing athlete lies in the therapists’ ability to understand the unique physical features associated with these athletes, while being able to identify and address the underlying pathological features that may have predisposed this athlete to injury. Modifiable risk factors for injury can be broadly classified as external or internal factors. External factors are those that occur because of the environment in which the athlete plays and include things such as playing volume and pitch counts. Internal risk factors are those specific to the player and include things such as soft tissue abnormalities or muscle strength. The key principle that must be acknowledged during the examination and treatment of the throwing athlete is that the throwing motion is a highly coordinated, fast moving task that involves the entire body. Although shoulder pain may be the primary complaint of the athlete, to facilitate optimal recovery, a detailed examination, inclusive of the entire kinetic chain, is necessary. This section of the chapter will first focus on the principles of examination necessary to identify both external and internal factors that may contribute to the development of injury. Foundational principles of rehabilitation that are common across all throwing injuries will then be presented, with specific modifications necessary for specific injury types highlighted. Finally, return to sports considerations, including outcomes testing and pitching evaluation will be discussed.
Examination
History and evaluation of external risk factors
The therapy examination of the pediatric throwing athlete should begin with a thorough history, seeking insight into important details of the injury characteristics, including the level of irritability and predisposing factors for injury. Exposure-related variables, such as playing baseball more than 8 months each year, high overall volume of pitches thrown per game or per season, inadequate rest between pitching outings, and pitching with arm fatigue are well-established risk factors for injury among youth baseball players. Therefore, a thorough review of the athletes baseball-specific activities is required. In addition to these volume dependent factors, the examiner should identify the type of pitches the athlete typically throws, as research has identified children who throw breaking pitches (i.e., curveball or sliders) are more likely to develop arm pain. This information is essential for parent and patient education during the reintroduction of sports activities during the late phase of rehabilitation, and also helpful during counseling regarding reducing the risk of future injuries upon discharge. The examiner will find that the pediatric or adolescent patient will typically forget or gloss over details that may be important for clinical decision-making. As a result, we recommend the examiner use very specific questioning, with age appropriate terminology, while also enlisting the assistance of the parent or guardian, to obtain a complete history. In addition to baseball-specific questions, the examiner should ascertain the athlete’s overall sports participation and external training activities, as these may contribute to overall workloads and the development of injury.
Posture
Generally, the physical examination of the youth athlete’s shoulder should begin with a detailed postural examination. In particular, the examiner should note resting scapular position, degree of thoracic kyphosis, and general muscular bulk or appearance. Although the exact correlation of scapular position or dysfunction with shoulder injury is unclear, abnormal scapular motion (termed scapular dyskinesis) has been associated with decreased shoulder mobility, increased likelihood of shoulder pathology, and impaired muscle activation and therefore should be addressed as part of an inclusive rehabilitation program. Normal scapular motion consists of smooth and symmetrical scapular upward rotation, posterior tilting, and external rotation during active elevation of the shoulders. The presence of scapular dyskinesis can be determined by observing the patient from behind, while the patient actively elevates and lowers both arms first in the frontal, and then in the sagittal plane. The scapulae should be observed, judging for any abnormal degree of motion or altered pattern of mobility. Several visual observation methods of determining scapular dyskinesis have been described and shown to be reliable in distinguishing normal from abnormal motion. Medial scapular border prominence (i.e., scapular winging) and loss of smooth motion during eccentric lowering are common abnormalities observed within the youth thrower. If scapular dyskinesis is present, any correlation to complaints of pain should be noted and the surrounding anatomic structures should be evaluated further, to determine the factors that may be causing dysfunction. This should include an assessment of thoracic spine mobility and flexibility of the pectoralis minor. Pectoralis minor length can be assessed by obtaining a linear measurement from the treatment table to the posterior aspect of the acromion while the patient is lying supine or by measuring the distance while the patient is standing with their back against a wall. Normal measurement distances have been described; however, these may be highly population dependent and thus comparison can be made to the contralateral side to determine relative tightness. In addition, isolated muscle performance testing of scapular stabilizing muscles should be performed, which will be covered in detail later in this chapter.
Shoulder range of motion
Before performing a specific examination of shoulder mobility, the patient should be screened for generalized ligamentous laxity using the Beighton scoring system outlined earlier, as generalized ligamentous laxity may lead to higher than normal ROM.
Accurate assessment and treatment of shoulder ROM deficits is a key concept in the treatment of the youth throwing athlete. Throwing athletes exhibit a pattern of increased glenohumeral external rotation (ER) and limited glenohumeral internal rotation (IR) in their dominant shoulder. Often the increase in ER is balanced by a concurrent loss of IR, such that the total arc of motion is the normal, just shifted toward an external rotation bias. Thus, upon examination, the typical healthy throwing athlete will demonstrate a greater degree of shoulder ER (external rotation gain), a lower degree of shoulder IR (GIRD), and a symmetrical amount of total shoulder rotational motion (ER + IR) between the dominant and nondominant sides.
Although most studies outlining this ROM profile were performed within adult baseball players, recent evidence demonstrates this asymmetrical shoulder rotation profile can be found in children as young as 8 years old and should be considered normal for this population. Deviations in shoulder motion, specifically GIRD >20 degrees, total arc of motion deficits of >5 degrees, flexion deficits of >5 degrees, and horizontal adduction deficits of >15 degrees, have all been identified as risk factors for injury among throwing athletes and should be assessed and addressed as part of a comprehensive treatment plan.
When assessing shoulder motion, it is important to stabilize the scapula, as unwanted accessory motion from the scapulothoracic joint may impact the accuracy true glenohumeral joint motion. The authors recommend stabilizing the scapular and assessing shoulder motion using standardized techniques as outlined in Fig. 25.3 .
Motor performance
As the shoulder girdle is arguably the least structurally stable joint in the body, the importance of assessing motor or muscular performance cannot be overstated. Various aspects of motor performance, including strength (more accurately described as force production), endurance, and control are crucial for the throwing athlete, and thus require specific evaluation during rehabilitation.
Force production
Manual muscle testing (MMT) may be utilized initially to screen the patient for large strength deficits; however, it should be noted that MMT may lack the sensitivity required to identify strength deficits within this population, particularly within the rotator cuff musculature. Although isokinetic dynamometry is the gold standard, handheld dynamometry (HHD) is an accurate and more clinically feasible alternative. Primary testing should consist of glenohumeral internal and external rotation at neutral elevation and 90 degrees of abduction. A ratio of at least 66% for ER to IR glenohumeral force production has been proposed as ideal and may be associated with reduced injury rates. Although the formal MMT for shoulder flexion and abduction is performed at end range, testing elevation at 90 degrees in the plane of the scapula, otherwise known as the “full can” position, is a better and more functional position. Testing of scapular musculature should not be overlooked, as diminished stability at the scapulothoracic joint has been associated with increased injury risk. Prone horizontal abduction testing at 90 degrees biases the middle trapezius, while the position at 120 degrees biases the lower trapezius. By placing the testing force at the distal radius, greater functional information of the kinetic chain can be garnered, but isolation of the trapezius musculature is better achieved with resistance at the spine of the scapula. Isolated testing of the serratus anterior may also be of particular value if scapular dyskinesis is observed.
Endurance
Adolescents tend to have less muscular endurance, and upper extremity fatigue has been associated with pain and injury in baseball players, making identification and treatment of muscular endurance deficits an important aspect of rehabilitation. Multiple endurance testing protocols exist for the upper extremity including isokinetics and repeated motions. The authors recommend use of the prone Y fatigue test, as decreased performance has been associated with injury, and seems to be most appropriate for throwers. These tests are likely not appropriate at the initial evaluation, but may be utilized later in the course of care for return to sport decision-making, or in the patient that complains of symptoms that seem to be associated with fatigue.
Control
Proprioceptive impairments have been identified in individuals with shoulder or upper extremity pain, and such impairments may increase the risk of injury or reinjury. Proprioceptive abilities may be reliably measured with isokinetic equipment, a laser pointer, or inclinometer. Yet, there is mixed evidence as to whether isolated proprioceptive training compared to more conventional treatment leads to improved outcomes. As such, specific examination of upper extremity proprioception and isolation of it as an outcome is likely unnecessary as long as it is addressed within the treatment plan.
Kinetic chain
The kinetic chain is the interaction of individual parts of the whole athlete to best produce a desired action. In throwing, the kinetic chain functions to transfer force from the ground to the ball, and optimal transfer of energy has been associated with injury prevention and improved performance. The examination of the throwing athlete must also include assessment of the spine, core, and lower extremities. Examination of every aspect of these regions is unreasonable, so key measurements and movement screens have been highlighted.
Spinal rotation should be measured grossly and if deficits are found, thoracic rotation should be examined more closely. Deficits in hip ROM have been associated with groin and throwing arm injuries in baseball players, and sufficient hip ROM has been proposed as necessary for optimal throwing mechanics. Similarly, at least 20 degrees of weight-bearing ankle dorsiflexion is necessary for proper wind-up mechanics, to provide sufficient propulsion from the ground into the driveline of a pitch, and also for allowance of deceleration on the lead leg at the end of the throwing motion. Lower extremity motor performance and balance control can be quickly screened with a single leg squat or lateral step down test.
The core musculature plays an important role in throwing, as it provides the link for the transference of force from the lower extremities to the upper extremities. A number of specific examination measures, such as timed planks, have been described in the literature. However one criticism of these tests is that they capture isometric endurance, which may not simulate the sport-specific action in baseball, in which motion is fast, dynamic, and often plyometric in nature. Nevertheless, we recommend use of these tests to gauge the athlete’s baseline level of physical ability and develop interventions to address identified deficits.
Treatment Considerations
The components of a successful rehabilitation program are driven by the details of the examination findings of that particular patient. There are many common elements of rehabilitation across the various thrower-specific conditions discussed in this chapter, and thus we will present treatment principles for many of these common elements here. At the conclusion of this section, we will present aspects of rehabilitation that are specific to the pathology or surgical procedure that was performed.
In general the rehabilitation program should be structured to respect the individual athlete’s pathoanatomical diagnosis (e.g., SLAP tear), identified impairments, and level of tissue irritability. The level of irritability relates to the tolerance for stress within the affected tissue and helps guide the clinician to select the appropriate level of intensity for therapeutic intervention. For example, after injury, the athlete may be experiencing high levels of pain and diminished shoulder motion. The treatment program at this time will emphasize patient education in activity modification, modalities to improve pain, and manual therapy to reduce pain and restore mobility. As the patient’s level of irritability decreases, the physical stress associated with rehabilitation exercises should be increased accordingly to more specifically target deficits in strength, motion, neuromuscular control, and other impairments identified during the evaluation that are contributing to dysfunction or impairing performance. Any modifications to rehabilitation based upon pathoanatomy or surgical restrictions will be layered over top of these general principles of rehabilitation progression.
When compared to their adult counterparts, one of the unique features of the youth athlete that makes rehabilitation challenging, but fun, is the necessity for more individual supervision during rehabilitation exercises. The youth athlete will require increased attention to ensure proper form and utilization of intended muscle groups, as substitution patterns are very common and sometimes difficult to identify. Use of visual feedback via mirror or video recording, along with tactile and verbal cuing, will be necessary to achieve optimal performance of exercises. Adherence to the prescribed home exercise program is also sometimes difficult. Typically, adherence can be improved by keeping the volume of exercises at home low, incorporating 4–6 exercises, which can be accomplished in 15 minutes or less. Additionally, variation of home exercise prescription is helpful to keep the program fresh, limiting boredom and keeping the athlete engaged. Parental supervision and involvement can be extremely helpful in improving compliance, while also assisting with monitoring for proper form while performing exercises outside of the clinic.
Posture and scapular dyskinesis
Treatment directed toward improving postural abnormalities and scapular dyskinesis can usually begin during the early phases of rehabilitation. Pectoralis minor tightness can be treated with unilateral corner stretch or manual stretching techniques, in which the scapula is brought into a position of retraction and posterior tilting. Manual stretching techniques may be improved by having the patient lie on a foam roller placed longitudinally along the spine. Manual therapy techniques to improve thoracic spine mobility may also be incorporated to improve posture and have also been shown to improve scapular muscle activity and strength. Various types of posterior to anterior mobilization or manipulation techniques have been described in sitting, supine, or prone. The therapist should determine the best technique for each patient based upon several factors including irritability of symptoms, body positions that may exacerbate patient symptoms, and body morphology. A thorough explanation of the intended mobilization procedure should be explained to both the parent and patient before engaging in this aspect of treatment, to obtain consent and optimize the effects of treatment. Appropriate screening for contraindications should be performed before initiating treatment. Although thoracic manipulation is safe, its use within growing children should be considered a precaution, and thus should be monitored carefully. In addition, the authors do not recommend utilizing manipulation techniques on children with hypermobility or significant ligamentous laxity.
Scapular strengthening exercises should also be incorporated here to improve scapular positioning and control during motion. Early exercises, such as shoulder external rotation with a stable scapula or serratus punches, can be initiated during periods of high irritability. As the patient’s irritability level decreases, exercises should be advanced to include those that target the middle and lower trapezius, such as prone I’s, T’s, and Y’s. Advanced exercises, such as closed chain serratus push-ups and dynamic stabilization in an open or closed chain, with more focus on endurance-based exercise prescription, should be incorporated in the late phases of rehabilitation ( Fig. 25.4 ).
