Proximal humeral epiphysiolysis (Little League shoulder) is a shear or stress injury of the epiphyseal cartilage of the proximal humerus. Little League shoulder has also been referred to as osteochondrosis of the proximal humeral epiphysis and rotation stress fracture of the proximal humeral epiphyseal plate. Little League shoulder occurs exclusively in athletes whose physis remains open, prior to closure of the growth plate, and it classically affects youth baseball pitchers. Since growth plate closure occurs between 18 and 21 years old, injuries can theoretically occur until that age. However, the typical age at presentation is between 11 and 16 years old. Although it is typically described in youth baseball players and throwing athletes, there have also been cases reported in competitive gymnasts and tennis players.
Little League shoulder is the result of excessive rotational and distractional forces that occur with repetitive overhead throwing. This repetitive microtrauma leads to cartilage damage of the proximal humeral epiphysis. It is believed that the rotational force has a larger role than the distractional force in the development of the condition.
The epiphyseal plate is at increased risk for injury because it is weaker than neighboring ligaments. This distinction is significant and explains why this age group is more likely to suffer growth plate injuries, whereas adults would suffer tendon or ligament injuries. The epiphyseal growth cartilage is also at higher risk for injury due to the repetitive action than adult cartilage. Another factor increasing the risk of injury in adolescents is bone growth, which can cause strength and flexibility imbalances. Additionally, the growth plate is more susceptible to torsion than it is to tension.
Another factor posited to contribute to Little League Shoulder is the angle of humeral retrotorsion. A recent case study suggested a rapid change in the humeral retrotorsion angle may increase susceptibility to growth plate damage. However, other studies state the increased retrotorsion does not appear to cause symptoms.
Little League shoulder is most common in youth baseball players. One study looked at 2055 baseball players between age 9 and 12. They found that 13.4% reported shoulder pain in their throwing arm. Of those patients with pain, 41 agreed to have x-rays taken of his or her shoulder. Of these 41, 36.6% had findings of Little League shoulder on x-ray. While this is a small sample size, this places the prevalence of Little League shoulder among all baseball players in this study, with and without pain, at 4.9%.
Another study of 1563 youth baseball players found that 15.9% had shoulder pain, although this was not specific to Little League shoulder.
There are 2 broad phases of the throwing motion. These are the arm-cocking phase followed by the acceleration phase. The pathophysiology leading to Little League shoulder is believed to be the significant external rotational torque on the humeral shaft during the final part of the arm-cocking phase, just before the acceleration phase. This torque likely leads to the deformation of the proximal humeral epiphysis cartilage, which eventually leads to proximal humeral epiphysiolysis.
As mentioned above, the distractional force has a lesser role than the rotational force. The distractional force that occurs during the throwing motion results in the rotator cuff muscles causing a force on the proximal humerus to keep the glenohumeral joint intact. The rotator cuff muscles exert a force on the proximal humerus because their insertion site is proximal to the proximal humeral epiphysis.
During an examination of a child suspected of having Little League shoulder, it is important to ask about a history of shoulder or elbow injury. Shoulder and elbow injury history are both important because they could both lead to a child consciously or subconsciously change his or her throwing mechanics to ease prior elbow pain. Altering mechanics may increase the risk of injury by distributing forces throughout the humerus differently. The examiner should also ask the patient if he or she has had a recent growth spurt as this likely places him or her at higher risk for proximal humeral epiphysiolysis.
Symptoms typically include a progressive onset of generalized shoulder pain when throwing. As symptoms advance, pain can develop with simply lifting the arm; there may even be pain at rest. However, until the late stages of the condition, the patient will likely report that symptoms improve with rest. Additional symptoms can include diminished throwing accuracy and/or velocity. Up to 13% of patients can have elbow pain in addition to shoulder pain.
On physical exam, patients are often tender to palpation over the growth plate on the lateral aspect of the proximal humerus. There may be subtle swelling; otherwise, inspection and palpation are generally normal. Decreased range of motion and muscle weakness can also be present depending on the severity of the case. Most frequently, weakness is due to guarding secondary to pain.
Diagnosis is primarily clinical suspicion. In most athletes, radiographs will show a normal physis. Diagnosis can be confirmed by radiographs, which may reveal a wide proximal humeral physis on an anteroposterior (AP) view of the shoulder with the arm in external rotation. Chronic changes such as sclerosis, demineralization, and fragmentation can also be seen. Musculoskeletal ultrasound can also help diagnosis in the hands of a practitioner experienced with musculoskeletal ultrasound. Ultrasound findings include increased hypo-echoic swelling around the affected shoulder which is not seen on the contralateral side. Although often unnecessary, MRI can be used to confirm the diagnosis if x-rays are negative. MRI would reveal edema around the physis.
If treated at the onset of pain, discontinuation of activities that cause pain can prevent the onset of an overt stress fracture of the growth plate of the proximal humerus. Prior to stress fracture occurring, pain often resolves with rest. Once stress fracture occurs, pain does not resolve with rest and the skill level while throwing decreases.
The treatment for Little League shoulder is 3 to 6 months of rest and discontinuation of overhead activity. Treatment can advance to core muscle and rotator cuff strengthening with a physical therapist once there is no pain at rest. Once the range of motion, strength, and scapular motion returns to normal, then a gradual return to throwing by participation in a structured throwing program and subsequent return to competition can follow.
Surgery is not indicated for proximal humeral epiphysiolysis.
The differential diagnosis includes:
Less common conditions on the differential diagnosis include:
One study determined a 3-grade classification of Little League shoulder based on radiographic findings.
An older classification system proposes 4 grades based on the level of displacement.
The majority of children with this condition will return to pre-injury activity level if they have sufficient rest from throwing and a gradual, structured return to play. One study found that adequate shoulder flexibility was related to a pain-free return to baseball.
Similarly, another study found that Little League shoulder patients with glenohumeral internal rotation deficit (GIRD), which is a decreased rotational range of motion of the shoulder, was associated with 3-times increased risk of recurrence of Little League shoulder.
Complications are rare, but they include growth plate anomalies such as:
Little League shoulder can be managed without consultation to a sports medicine physician or orthopedic surgeon as long as the managing physician is practicing within his or her expertise and is confident he or she is making the correct diagnosis.
This injury is due to overuse from repetitive throwing. Therefore, deterrence includes avoiding excessive throwing. Current literature proposes limiting pitch counts to prevent primary onset and recurrence of Little League shoulder. Stretching before and after sport and icing the shoulder after throwing is also important. Further, it is recommended to take one season off of throwing per year. United States Baseball and Major League Baseball recommend age-based pitch counts and days of rest based on the pitch count to guide youth players and coaches on a safe amount of throwing-induced stress. Proper biomechanics of a child’s throwing motion should also be encouraged to ensure the mechanics do not cause excess stress on the shoulder. One study found that 80.6 degrees of shoulder abduction and 10.7 degrees of horizontal shoulder adduction minimized the shear forces on the shoulder, while increased shoulder abduction increased anterior force.
Other mechanical factors that can increase torque on the shoulder and elbow and therefore increase the risk of injury include:
When the child returns to throw, the practitioner should discourage the child from taking NSAIDs before throwing to avoid covering up inflammatory etiologies of pain.
The best outcomes with Little League shoulder will occur when the treating physician is working in close contact with a physical therapist who can confidently perform strengthening of the rotator cuff and core muscles. The physical therapist should also be familiar with a throwing program. Parents and coaches should also be included in the treatment team of Little League shoulder as they have the power to ensure adequate rest for the athlete after an injury has occurred. Parents and coaches can also limit throwing to appropriate levels to mitigate the risk of developing primary or recurrent shoulder and other arm injuries.
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