It is estimated that baseball is the second most commonly played team sport in the United States, with approximately 8.6 million participants aged 6-17 yr participating each year (35). Although much of the media attention is on the adult game, children and adolescents account for the greatest number of participants in baseball. Overall, baseball is a very safe sport in which to participate (33), but the demands of the game can lead to particular injury patterns. Traumatic injuries in baseball demonstrate patterns that are similar to other sports and therefore will not be dealt with in this article. The objective of this article is to enlighten the clinician about overuse patterns commonly noted in youth baseball so as to properly diagnose, treat, manage, and prevent these injuries.
All health care providers working with young throwers should be aware of the bone maturation of the shoulder and elbow. The physis of the humerus in a young thrower may not close completely until as late as age 20, with a range of 14-20 yr. This factor plays a role in proximal epiphysiolysis of the humerus and a phenomenon known as humeral retroversion that may possibly lead to glenohumeral internal rotation deficit (GIRD), an acquired lesion causing subtle posterior subluxation of the humeral head in maximal abduction and external rotation (34).
Knowledge about the timing of physeal closure at the elbow also is important. Six ossification centers appear around the elbow from ages 3 months to 11 yr and do not close until age 10-17 yr (Table 1). These open growth plates can be the weak link in the system and may be the site of injury. Awareness of the timing of closure also can be important when evaluating for fracture.
Because the ulnar collateral ligament (UCL) is much stronger than an open physis, when injury occurs due to stress on the medial elbow, it often involves the physis. Injuries include medial epicondyle avulsion fractures and medial epicondylar apophysitis (Little League elbow). Upon closure of the physis, the UCL is more likely to be injured. Olecranon apophysitis and frank avulsion fractures can result from excessive, repetitive stress to the posterior elbow (11). In the skeletally immature shoulder, the repetitive, rotational stress applied to the physis of the proximal humerus during throwing may lead to widening of this physis, or epiphysiolysis (Little League shoulder) (31). In the older thrower, however, these forces can result in tendinopathy and tears of the rotator cuff.
Many risk factors have been proposed for young throwing athletes, and there is strong evidence that injury rates, and subsequent surgery, is on the rise (1). Initial epidemiological studies surveyed coaches and orthopedic surgeons to determine perceived injury risk factors (25). These studies led to the first recommendations in 1996 from USA Baseball, the governing body for all amateur baseball in the United States. Subsequent research has helped to shape the most recent guidelines, which are available through USA Baseball (Table 2).
Epidemiological studies have demonstrated that taller and heavier children have an increased risk of injury to the elbow and shoulder than their counterparts of the same age (30). One possible explanation for this finding may include their higher level of performance and subsequent overuse by coaches set on winning.
GIRD also has been proposed as a nonmodifiable risk factor for shoulder injury due to chronic distractive forces experienced by the posterior/inferior capsule during follow-through resulting in posterior capsular contracture. Subsequent migration of the humeral head in a posterior-superior direction may put the rotator cuff and labrum at risk for injury. Evidence seems to indicate that humeral retroversion, which may lead to GIRD, develops due to the forces across the proximal humerus in young throwers (29,36). There also is evidence that GIRD may bring risk to the UCL (14).
Proper throwing biomechanics also are important for safe pitching practices (3,24). Two separate studies using high-speed video demonstrated: 1) that flaws in the mechanics of adolescent throwers increased the likelihood of injuries and 2) that proper mechanics lowers the likelihood of high-risk stressors to the elbow and shoulder (12,21).
It also is conversely believed that poor mechanics may lead to pain and injury in young athletes (4). A common injury pattern is due to the principle described as "valgus extension overload" (18). In the early phases of throwing, the medial elbow sustains a significant tensile force while the lateral elbow experiences a compressive force. The olecranon, posteriorly, is subject to stress during full extension that occurs in the late stage of throwing. Fleisig et al. (16) evaluated the biomechanics of different levels of development in pitchers (youth, high school, college, and professional) and found that the young pitchers are in fact able to learn proper biomechanics at a young age.
Also of note, abnormal scapular motion on the thoracic wall can both contribute to shoulder injury and indicate rotator cuff injury or glenohumeral instability. Normally, the scapula rotates externally and upwardly during abduction of the arm (23). Both scapulae should move with similar rhythm and without "winging."
High velocity also has been found to be a risk factor. In cadaveric studies of the UCL, the upper limit of torque the ligament can withstand before failure is around 32 Nm. This correlates with pitch speeds approaching 80 mph (1,13,30). In addition, these high-velocity throwers were more likely to be overused, recruited to more leagues, and pursued early to accelerate their development. More pitching practices that have been implicated as risky for a young thrower include being primarily a starter, participating in showcases, and throwing a greater number of warm-up pitches prior to entering a game (30).
The overwhelming factor that leads to injury is overuse. Pitching too much in a short time span, with insufficient periods of rest, has been shown to lead to adverse outcomes. Olsen's study showed that the athletes requiring surgery had a significantly greater number of pitches per game, per season, and per year than noninjured counterparts. Lack of time off from throwing also was a risk factor. Throwing with fatigue and pain also had a large effect on causing damage to structures of the elbow and shoulder of throwers (30).
A topic of significant debate is the influence of pitch type on injury. Recent studies hint that pitch volume (pitch count and frequency) and overuse lead to shoulder and elbow injuries in the young throwing athlete (16,25,30), not necessarily the type of pitch thrown. Dun et al. (15) found that shoulder internal rotation torque and proximal force as well as elbow varus torque and proximal force were significantly less for the curveball than the fastball when comparing the biomechanics of youth pitchers throwing the fastball, curveball, and change up. Although more research in this important area is needed, this suggests that the curveball might not be more harmful to the youth pitcher than the fastball.
Medial elbow pain in a thrower often is a diagnostic dilemma secondary to the fact that there are many structures in close proximity that may generate pain from the stress of throwing. The medial epicondyle physis is the last to close at the elbow, and the flexor/pronator tendon attaches at the medial epicondyle. Medial tensile forces across the medial elbow can lead to common overuse symptoms consistent with medial epicondylar apophysitis, flexor/pronator strains and tendinopathy, UCL sprains, ulnar neuritis, or medial epicondyle avulsion fractures (20). Patients often present with pain but may complain only of loss of control or decreased velocity.
Conventional radiographs, especially when conducted with comparison films of the uninvolved elbow, can be helpful in teasing out the culprit. Widening or frank avulsion of the medial epicondyle differentiates the less severe entities from those that might require lengthier rest or surgery. The physis is the weak link and therefore is more often injured than the UCL in the skeletally immature athlete. At our institution, displacement of the medial epicondyle in an athlete who seems dedicated to a throwing sport is concerning secondary to the fear that UCL function may be compromised after the physis heals. Surgical fixation of an avulsed medial epicondyle therefore is an option to be considered in this population.
On the lateral side, the differential to consider in the young thrower is much more confined. Lateral epicondylitis/extensor tendinopathy is far rarer than in adults. Lateral pain in this setting needs to have the practitioner consider an osteochondritis dissecans (OCD) of the capitellum. It has long been felt that repetitive compressive forces of throwing upon the capitellum, along with its tenuous blood supply, combine to lead to the OCD seen in this area of the young elbow (6). Conventional radiograph can help to establish the diagnosis, but magnetic resonance imaging (MRI) is required to stage the lesion and provide prognosis. The severity of the OCD and bone age will determine healing potential if treated conservatively (28).
Another cause of chronic, dull, aching pain in the lateral elbow of younger children aged 7-10 yr is Panner's disease. An entity that usually is worse with activity, such as throwing, Panner's disease is localized to the capitellum with degeneration and necrosis followed by regeneration and recalcification. Prolonged rest from painful activity while following radiographic healing is the hallmark of treatment (7).
Posteriorly, much of the issues revolve around repetitive forced extension seen in the follow-through phase of pitching, commonly referred to as "valgus extension overload." This force can lead to posterior olecranon impingement, apophysitis, avulsion fractures, or stress fractures. Mechanical symptoms of locking or inability to fully extend also may indicate the presence of intraarticular loose bodies. Posterior olecranon impingement also can be the first sign of UCL incompetence (18).
Many common throwing injuries seen in the adult athlete rarely are seen in youth baseball. External impingement secondary to encroachment of a hooked or spurred acromion or from hypertrophy of a degenerative acromio-clavicular joint is uncommon. Rotator cuff tears and superior labral tears from anterior to posterior (SLAP) lesions also are encountered rarely in the young thrower but may require some consideration in the older adolescent who remains symptomatic in spite of adequate treatment.
Internal impingement, an injury brought on by repetitive striking of the articular surface of the supraspinatus tendon against the posterosuperior glenoid rim and labrum when the arm is in the extreme of abduction and external rotation of the deep cocking phase, can cause damage to the rotator cuff or labrum of the older adolescent shoulder. Some authors believe that the essential lesion that brings on this phenomenon is a tight posterior capsule and cuff. To avoid problems in adulthood, young throwers are encouraged to stretch the posterior structures of the shoulder in a routine manner (8,9).
Another common and somewhat controversial injury that is specific to young overhead athletes is proximal humeral epiphysiolysis. It is believed the rotational stresses upon the proximal humeral physis lead to a type of Salter-Harris I fracture. Upper arm pain and widening of the physis on x-ray has long been enough for the diagnosis of "Little League shoulder" in a young thrower with a history of overuse. Radiographic studies of young arms however, have complicated the picture. Radiographs of 79 baseball players, ages 8 to 15 yr, demonstrated widening of the physis in the dominant shoulder regardless of pain (26). In another study of the Brazilian National team with an average age of 14.5 yr, radiographic changes were seen in two thirds of the team, and no significant correlation could be found with the clinical evaluation. These findings are important to consider as the usual treatment for this problem is lengthy rest from throwing (28).
Like so many overuse injuries, there is little room for cookie cutter strategies with regard to throwing injuries. Almost every scenario will be different depending upon the duration and perceived severity of symptoms, position played, timing of injury, and findings on exam. General recommendations can be made, but historical information and clinical judgment likely will modify any generalities that might be suggested.
Rest is the hallmark treatment of any suspected overuse injury. However, rest often is the most difficult treatment to suggest to an athlete. Arm rest for 6 wk often is recommended as the first line of treatment in an injury that already has led to pain and forced rest by the athlete. The rest recommended usually is considered "relative rest," where the athlete is allowed to be involved in other activities, such as conditioning, batting, and skill work, that do not lead to pain. Also, they are instructed on a gentle rehabilitation protocol that allows for nonpainful motion and strengthening. We often recommend a short, 10- to 14-d course of a nonsteroidal antiinflammatory drug (NSAID) to assist with any acute inflammation and pain. In cases of milder and less prolonged symptoms, the period of rest might be briefer and movement toward return-to-play (RTP) may be quicker. The more demanding positions of pitcher and catcher may further delay return, but position players might be allowed to RTP more rapidly. Essentially all throwers should be progressed back to play through the use of an interval throwing program (ITP) (5). The athlete should be able to demonstrate painless throwing in a practice setting prior to competition. Different positions may require a more extensive ITP than others. In other words, the first base player only may need to progress to 120 ft prior to return, whereas the pitcher will need to move through a phase of throwing 150 ft on flat ground and progression of throwing off the mound. Again, the speed of progression will be driven by severity of symptoms and clinical judgment.
More aggressive interventions can be entertained for recalcitrant cases, but even then, use of injections in children and adolescents should be rare. Fenestration, or percutaneous tenotomy, techniques in more chronic tendinopathies, have shown some efficacy in adults, but there are no studies in younger individuals (27). Platelet-rich plasma (PRP) is a newer innovation that is gaining popularity, but there still is much to be studied. Intuitively safe, PRP lacks solid proof of efficacy, and there are no set protocols to maximize treatment. Out-of-pocket costs and availability also provide barriers to making this treatment mainline.
Only after the proper nonoperative approaches are tried and have failed is further imaging needed to prepare for possible surgical intervention. Many radiological findings in the throwing shoulder or elbow are not clinically relevant unless the athlete remains symptomatic after appropriate treatment has failed (10,19,22). If the thrower can return to high-performance throwing in a pain-free manner after nonoperative treatments, any findings on imaging studies likely are inconsequential.
The overall outcome from UCL reconstruction in high-school throwers demonstrates similar high levels of return to previous level of activity as other levels of competitors. Petty et al. (32) found that many high-school athletes who underwent UCL reconstruction did not return to previous levels of play due to factors that were unrelated to either baseball or treatments.
While adequate rest between competitions and closely followed pitch counts are recommended (Table 2), young pitchers still are encouraged to throw in other settings (e.g., playing catch at home, playing other positions) for strengthening of his or her arm and body. However, additional pitching sessions with coaches, or even parents, should be avoided. Observing for discomfort and fatigue is important in the prevention of injury (4). It does appear that the number of pitches and recovery time is more important to monitor than the type of pitch being thrown (30). Adolescents should not be allowed to pitch more than 85 pitches each game, more than 8 months out of a year, or with arm fatigue. Correction of poor pitching mechanics also may reduce injury risk. If elbow or shoulder pain develops, the young thrower should be evaluated by a knowledgeable sports medicine physician (17). An excellent resource for young pitchers can be found in a publication from Little League Baseball, Inc. (www.littleleague.org/Assets/old_assets/media/Pitch_Count_Publication_2008.pdf). Contained in this publication is information regarding the use and reasoning behind pitch counts. It also is a good resource for pitching fundamentals and pitching recovery techniques.
Although baseball is a safe sport for young athletes, there are some injuries of which clinicians should be aware in this age group. Fortunately, structural damage that might lead to surgery is rare in this population. Minimizing risk factors is vital in overcoming the possibility of overuse injuries of the upper extremity. Pain in the elbow or shoulder of a young thrower always should be evaluated. Throwing with pain can lead to poor mechanics and a vicious cycle of persistent problems. It also is possible that many of the career-ending injuries seen later in an overhead athlete may have been avoided with simple measures if caught early.
1. American Sports Medicine Institute Website [Internet]. Birmingham (AL): American Sports Medicine Institute [cited 2010 May]. Available from: www.asmi.org/asmiweb/usabaseball.htm
3. Andrews JR, Fleisig GS. Preventing throwing injuries. J. Orthop. Sports Phys. Ther.
4. Andrews JR, Fleisig GS. How many pitches should I allow my child to throw? USA Baseball News.
5. Axe MJ, Snyder-Mackler L, Konin JG, Strube MJ. Development of a distance-based interval throwing program for little league-aged athletes. Am. J. Sports Med.
6. Bradley JP, Petrie RS. Osteochondritis dissecans of the humeral capitellum, diagnosis and treatment. Clin. Sports Med.
7. Bradley JP, Petrie RS, Tejwani S. Throwing injuries, elbow injuries in children and adolescents. In: Delee, Drez, Miller, editors. Delee & Drez's Orthopaedic Sports Medicine-Principles and Practice
. 3rd ed. Philadelphia (PA): Saunders Elsevier, 2010, p. 1238.
8. Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: spectrum of pathology, part I: pathoanatomy and biomechanics. Arthroscopy
. 2003; 19:404-20.
9. Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: spectrum of pathology, part III: the SICK scapula, scapular dyskinesis, the kinetic chain, and rehabilitation. Arthroscopy
. 2003; 19:641-61.
10. Connor PM, Banks DM, Tyson AB, et al
. Magnetic resonance imaging of the asymptomatic shoulder of overhead athletes: a 5-year follow up study. Am. J. Sports Med.
11. Crowther M. Elbow pain in pediatrics. Curr. Rev. Musculoskelet. Med.
2009; 2(2):83-7 [Epub 2009 Mar 14].
12. Davis JT, Limpisvasti O, Fluhme D, et al
. The effect of pitching biomechanics on the upper extremity in youth and adolescent baseball pitchers. Am. J. Sports Med.
13. Dillman, CJ, Smutz P, Werner S, et al
. Valgus extension overload in baseball pitching. [Abstract] Med Sci Sports Exerc.
1991; 23(suppl 4): S135.
14. Dines JS, Frank JB, Akerman M, Yocum LA. Glenohumeral internal rotation deficits in baseball players with ulnar collateral ligament insufficiency. Am. J. Sports Med.
2009; 37(3):566-70 [Epub 2008 Dec 4].
15. Dun S, Loftice J, Fleisig GS, et al
. A biomechanical comparison of youth baseball pitches: is the curveball harmful? Am. J. Sports Med.
16. Fleisig GS, Barrentine SW, Zheng N, et al
. Kinematic and kinetic comparison of baseball pitching among various levels of development. J. Biomech.
17. Fleisig GS, Weber A, Hassell N, Andrews JR. Prevention of elbow injuries in youth baseball pitchers. Curr. Sports Med. Rep.
18. Hutchinson MR, Ireland ML. Overuse and throwing injuries in the skeletally immature athlete. Instr. Course Lect.
19. Jazrawi LM, Leibman M, Mechlin M, et al
. Magnetic resonance imaging evaluation of the ulnar collateral ligament in young baseball pitchers less than 18 years of age. Bull. Hosp. Joint Dis.
20. Kaeding CC, Whitehead R. Musculoskeletal injuries in adolescents. Primary Care
. 1998; 25(1):211-23.
21. Keeley DW, Hackett T, Keirns M, et al
. A biomechanical analysis of youth pitching mechanics. J. Pediatr Orthop.
22. Kooima CL, Anderson K, Craig JV, et al
. Evidence of subclinical medial collateral ligament injury and posteromedial impingement in professional baseball players. Am. J. Sports Med.
23. Ludewig PM, Reynolds JF. The association of scapular kinematics and glenohumeral joint pathologies. J. Orthop. Sports Phys. Ther.
24. Lyman S, Fleisig GS, Andrews JR, Osinski ED. Effect of pitch type, pitch count, and pitching mechanics on risk of elbow and shoulder pain in youth baseball pitchers. Am. J. Sports Med.
25. Lyman S, Fleisig GS, Waterbor JW, et al
. Longitudinal study of elbow and shoulder pain in youth baseball pitchers. Med. Sci. Sports Exerc.
26. Mair SD, Uhl TL, Robbe RG, Brindle KA. Physeal changes and range-of-motion differences in the dominant shoulders of skeletally immature baseball players. J. Shoulder Elbow Surg.
27. McShane JM, Nazarian LN, Harwood MI. Sonographically guided percutaneous needle tenotomy for treatment of common extensor tendinosis in the elbow. J. Ultrasound Med.
28. Mihara K, Tsutsui H, Nishinaka N, Yamaguchi K. Nonoperative treatment for osteochondritis dissecans of the capitellum. Am. J. Sports Med.
29. Nakamizo H, Nakamura Y, Nobuhara K, Yamamoto T. Loss of glenohumeral internal rotation in little league pitchers: a biomechanical study. J. Shoulder Elbow Surg.
30. Olsen SJ, Fleisig GS, Dun S, et al
. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. Am. J. Sports Med.
31. Osbahr DC, Kim HJ, Dugas JR. Little League shoulder. Curr. Op. Pediatr.
32. Petty DH, Andrews JR, Fleisig GS, Cain EL. Ulnar collateral ligament reconstruction in high school baseball players: clinical results and injury risk factors. Am. J. Sports Med.
33. Radelet MA, Lephart SM, Rubinstein EN, Myers JB. Survey of the injury rate for children in community sports. Pediatric.
34. Sanders T. Glenohumeral instabilities: imaging of the glenohumeral joint. In: Delee, Drez, Miller, editors. Delee & Drez's Orthopaedic Sports Medicine-Principles and Practice
. 3rd ed. Philadelphia (PA): Saunders Elsevier, 2010, p. 979-80.
35. USA Baseball Website [Internet]. Durham (NC): USA Baseball [cited 2010 May]. Available from: www.usabaseball.com
36. Whiteley RJ, Ginn KA, Nicholson LL, Adams RD. Sports participation and humeral torsion. J. Orthop. Sports Phys. Ther.