The rehabilitation of common skeletally immature throwing injuries.

The volume and intensity of competition among young throwing athletes can place them at increased risk of shoulder injuries, which occur in patterns unique to the skeletally immature athlete. Prompt recognition and treatment of these injuries are critical to prevent long-term functional disability. Adolescents participating in recreational and organized throwing sports are particularly susceptible to shoulder injuries involving both osseous and soft-tissue structures. Understanding the relevant functional anatomy, biomechanics of throwing, pathophysiology of injury, and keys to a successful rehabilitation can help the clinician manage common skeletally immature throwing injuries. Overuse injuries occur more frequently than do acute, traumatic injuries; and early recognition, coupled with appropriate treatment or prevention, can help restore and maintain normal shoulder function. Four of the most common pathologies seen in the skeletally immature throwing athlete include shoulder impingement, Little League shoulder, rotator cuff tears, and glenohumeral instability.

Common Injuries

Little League Shoulder Proximal humeral epiphysitis, or Little League shoulder, is most often seen in pitchers between 11 and 16 years of age. This is caused because the weakest link of the throwing shoulder in the adolescent population is the proximal humeral epiphysis. This growth plate is present in the shoulder of younger athletes in the distal humerus. Repetitive stress causes this growth plate to be more vulnerable than the surrounding muscles or tendons. The problem arises when athletes age 9–13 have ununited epiphyses that are subjected to repetitive torque produced by the attached muscles.

The chief complaint of athletes with Little League shoulder is usually pain in the proximal humerus while throwing. Lynman et al1 has demonstrated a relationship between the number of pitches thrown and this disease. Often, the athlete will present with tenderness to palpation of the proximal humerus. An x-ray is useful in confirming this diagnosis.

Impingement Syndrome

Impingement syndrome is painful irritation of the tendons and/or bursa attached to the rotator cuff in the shoulder. The tendons and bursa rub against one another whenever the athlete gets into the late cocking throwing position and cause inflammation. A Hawkins test or Neer impingement test can confirm this diagnosis. The underlying etiology has been linked to poor throwing mechanics, tight posterior shoulder structures, external rotation weakness in 90/90, and scpulohumeral rhythm dysfunction.

Rotator Cuff Injuries

Rotator cuff injuries are the most common cause of shoulder pain in adults over 30. Significant trauma to the upper extremity is often a prerequisite for rotator cuff failure in the younger patient. However, overhead-throwing athletes have been reported to sustain rotator cuff tears due to chronic overuse. Subacromial impingement due to occult shoulder instability and internal impingement of the rotator cuff on the posterior glenoid are described mechanisms of injury.2 Pain and weakness were the most common symptoms reported by these patients. On physical examination, objectively documenting focal weakness or decreased range of motion with abduction or external and internal rotation should raise suspicion of rotator cuff injury. Furthermore, magnetic resonance imaging serves as a useful adjunct in the workup of adolescents with suspected rotator cuff abnormality.

Shoulder Instability

Shoulder instability is a condition in which the capsular restraints are stretched and dynamic muscular force is unable to hold the humeral head centered in the glenoid fossa. Most of the time in the throwing athlete, it creates microinstability and unwanted glenohumeral translation. In some cases, the unstable shoulder can actually slip out of the socket. The microtrauma of throwing, coupled with a baseline level of increased laxity, puts this athlete at risk for developing damage to the intra-articular structures of the shoulder.3 As a result of their increased level of laxity, many of these athletes will throw with the most velocity and ball movement but will have the greatest risk of long-term injury. If not treated, instability can lead to arthritis of the shoulder joint. Persons with this type of instability exhibit signs of generalized ligamentous laxity. These athletes exhibit bilateral, symmetric increases in shoulder laxity. For these patients, the relocation test is often positive and glenohumeral translation is excessive.

Treatment Protocols

Rehabilitation of any throwing athlete, especially one that is skeletally immature, is a critical component of returning the athlete back to their desired sport. Using the principles of rehabilitation in the thrower set forth by Wilk et al4 (Table 1, below), will lay a strong foundation for the rehabilitation of this patient population regardless of the above diagnoses with which they may present. Within these principles, a few key components demand specific attention. These include: total glenohumeral range of motion, progressive strengthening, a return-to-throwing program, and understanding age-restriction modifications. Each of these research-based components is an essential key area that all personnel who work with throwing athletes should understand and consider when rehabilitating these patients.

The alteration in range of motion in the shoulders of throwing athletes has been a well-researched topic. Many authors have reported the loss of internal rotation and gain in external rotation. However, a number of hypotheses have arisen to explain these alterations.5-7 Although many feel that these changes are a product of soft-tissue adaptations from years of throwing, more recent studies have focused on the bony or osseous changes. In a recently published article by Meister et al, findings suggest that as adolescent throwers’ ages increase, their total range of motion actually decrease. Throwers between the ages of 13 and 14 saw the most dramatic decline in total range of motion. Most interestingly is that this decline in total range of motion is found 1 year prior to the peak age incidence of Little League shoulder.

When rehabilitating a thrower, it is important to consider the thrower’s total range of motion. Burkhart and Morgan8 consider a "shoulder at risk" if it does not have a total range of 180º. Typically, in a thrower, this loss of range will be in the form of a tight posterior inferior capsule and will be noted during internal range of motion at 90º of abduction. This is often termed Glenohumeral Internal Rotation Deficit (GIRD). At our institute, we assess this by measuring the supine internal rotation, as well as by performing the sideling posterior shoulder-tightness test.9,10 (Figure 1, page 28) This measurement will enable us to determine if the loss of internal rotation is a product of musculotendinous tightness or capsular tightness in the posterior shoulder. By addressing these possible deficits, the thrower will be allowed the range of motion to generate the proper torque as they throw, without compromising other structures.

The second key component of a good rehabilitation program for adolescent throwers is a well-designed progressive strengthening program. Most notable is the Thrower’s Ten Program (Table 2, above),

which is designed to exercise the major muscles associated with the throwing motion. These exercises can be easily progressed with the use of resistance bands. Along with these progressive exercises, further addressing proximal scapular strength is essential to maintain a stable base for distal movement. It is important to develop a training program that addresses both strength and endurance of the force couple relationships associated with pitching.11 Based on work by Townsend et al12, Blackburn et al13, and Moseley et al14, our institute also adds a "plus" to push-ups and stresses a Prone Program. The Prone Program consists of horizontal abduction with internal rotation, horizontal abduction with external rotation, and external rotation at 90º of abduction and scaption.

The next progressive step to sending these athletes back to throwing is a plyometric program. Although there is minimal evidence to support the effects of training upper-extremity plyometrics, Heiderschiet et al15 showed potential by improving internal-rotation strength and functional performance in overhead male athletes with upper-extremity plyometric training. It has been well-documented that overhead athletes have altered proprioception in their throwing shoulders, before and after throwing.16-18 This lack of proprioception has often been scrutinized as the catalyst for injury. Adding an upper-extremity plyometric program that addresses strength and coordination in a functional 90/90 position may improve this lack of proprioception.

The third key component is a data-based interval-throwing program. It is difficult to mimic the forces and torques of baseball throwing with therapeutic exercises. The only true way to mimic the joint forces of a baseball throw is to actually throw the ball. By integrating pitching statistics, field dimensions, performance restrictions, biomechanical studies, and a basic understanding of tissue-healing times, Axe et al have developed interval throwing programs for Little League, high school, college, and professional pitchers.19 

The final component of treating these specialized athletes is the understanding of age-restricted modification for prevention. There is a fine line between throwing too much and not throwing enough. Lyman et al1 found that the risk of elbow pain increased 35% and the risk of shoulder pain increased 50% by the time a pitcher (9–14 years old) reached a level of 75 to 99 pitches thrown per game. This also had a cumulative effect during the season. The pitcher’s odds of getting elbow and shoulder pain steadily increased after throwing between 600 and 800 pitches per season. Based on this study and older recommendations by USA Baseball, pitchers between 9 and 14 years of age should consider limiting their pitches to 75 per game or 600 per season. These numbers do not include warm-ups, drills, and other positional throws that are vital to the player’s development. It is also stressed that pitchers in this age group do not throw a curveball or slider. Pitchers should concentrate on developing their fastball and complementary change-up for an off-speed pitch.1

We have highlighted injuries and the importance of a well-rounded rehabilitation program for the skeletally immature throwing athlete. By addressing range-of-motion restrictions and progressive strengthening using a data-based return-to-throwing program, and understanding the importance of pitching modification, we will address the major concerns of the skeletally immature thrower as well as the parents.

Timothy F. Tyler, MS, PT, ATC, is a clinical research associate at the Nicholas Institute of Sports Medicine and Athletic Trauma, Department of Orthopaedics, Lenox Hill Hospital, NY. He is also the founder and director of PRO Sports Physical Therapy of Westchester, Scarsdale, NY. Michael J. Mullaney, MPT, is a staff physical therapist at the Nicholas Institute of Sports Medicine and Athletic Trauma, Department of Orthopaedics, Lenox Hill Hospital, NY.

References

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