Chronic repetitive stress injuries are more common in the pediatric population than acute traumatic fractures and dislocations . Skeletally immature individuals are susceptible to stress injuries to the weaker physeal cartilage of the epiphyses and apophyses. Repetitive microtrauma can disrupt endochondral ossification in the physes of long bones and lead to extension of unmineralized cartilage into metaphyseal bone . Stress fractures are encountered in patients who load the upper extremity in a chronic and repeated fashion. Causes of stress injuries in children include overuse, underlying bony weakness (caused by poor bone mineralization or failure of bone formation), infection, endocrine abnormalities, congenital abnormalities, neoplasm, previous trauma, or an inflammatory response.
Increased competitive youth sport participation has led to an increase in the prevalence of stress injuries of the upper extremity. When conducting a patient history and physical examination, one must consider a multitude of causes, but this review will focus on overuse injuries. Challenges to establishing the diagnosis of stress injuries in children are an absence of a complete history, an inability to recognize the activities that led to injury, and a lack of specific complaints . Most stress injuries require only conservative treatment and improve with rest. However, the stress injury must be identified and the stressor must be removed to prevent potential growth disturbances.
Stress injuries of the shoulder are common in throwing athletes. A thorough cervical spine examination should be conducted to rule out occult abnormalities of the cervical spine that may cause radiating pain to the shoulder (e.g. herniated nucleus pulposus or spinal cord syrinx). Common types of shoulder stress injuries include little leaguer's shoulder, glenohumeral instability, and glenohumeral internal rotation deficit (GIRD).
Little leaguer's shoulder mainly occurs in pitchers between 11 and 13 years of age, when physeal growth is maximal [4▪▪]. Throwing activities cause repetitive rotational stress across the proximal humeral physis . The typical patient presents with pain during pitching activities that have persisted for several months. Radiographs frequently show proximal humeral physeal widening (Fig. 1). Treatment involves rest from throwing activities until the pain resolves, which takes 3 months on average . In addition, a throwing mechanics evaluation and a course of physical therapy to strengthen and stabilize the shoulder are useful adjuncts in treatment in an effort to avoid re-injury.
Glenohumeral instability is a stress injury frequently encountered in throwers, gymnasts, and swimmers. Glenohumeral instability can have traumatic or atraumatic causes. The discussion of traumatic causes is beyond the scope of this review. Ligamentous laxity in pediatric athletes can lead to multidirectional shoulder instability. Increased elasticity of the glenohumeral ligaments leads to microtrauma and subsequently abnormal translation of the humeral head. Typically, patients will present with complaints of subluxation episodes with their specific sport activity. These patients should be evaluated for hypermobility of their joints with the Beighton criteria (e.g. flat hands on floor with straight knees, hyperextension of elbows and knees, thumb touches volar surface of the forearm) . MRI aids in the detection of lesion associated with glenohumeral instability. Structured rehabilitation is successful in 80% of patients with multidirectional instability . If conservative treatment fails, surgical options may be considered, such as a capsular shift [4▪▪].
GIRD is another cause of shoulder pain in throwing athletes. Similarly to little leaguer's shoulder, GIRD develops and worsens over time; it is not associated with an acute event. The patient typically complains of vague shoulder pain; and the physical examination is notable for a loss of internal rotation of the throwing shoulder compared with the contralateral shoulder. If left untreated, GIRD can alter scapular and shoulder biomechanics . Often, GIRD is overlooked as glenohumeral instability and is likely underdiagnosed. Although rare, osteochondritis dissecans (OCDs) of the glenoid may mimic symptoms of GIRD (pain and limited range of motion). MRI helps to confirm the diagnosis of GIRD by ruling out other shoulder lesion. Most children will respond to conservative treatment that involves aggressive posterior capsule stretching . As with glenohumeral instability, if conservative treatment fails, then surgical options are considered.
Pediatric elbow injuries occur most commonly in baseball, tennis, and gymnastics [10▪]. Stress injuries at the elbow can be divided into medial, lateral, and posterior compartments. Elbow stress injuries collectively are referred to as little leaguer's elbow. When dealing with injuries of the elbow, it is important to consider the patient's age, acute or chronic nature of the pain, anatomic location of the pain, and position played. Physical examination must include palpation and inspection of bony prominences, assessment of elbow range of motion (flexion, extension, pronation, and supination), and varus and valgus stress testing to gauge joint stability. Furthermore, a thorough neurological examination and evaluation of the neck, shoulder, and wrist must be completed to insure that there are no other causes of pain. Although radiographs are indicated at the first evaluation, elbow lesion is often better diagnosed with MRI. Radiographs of the contralateral elbow may be useful for comparing anatomy of the uninjured extremity. Common types of elbow stress injuries include medial epicondyle apophysitis, medial epicondyle avulsion fractures, ulnar collateral ligament (UCL) insufficiency, lateral elbow compression from Panner disease, OCD of the capitellum or radial head, posteromedial impingement, and olecranon apophysitis.
Medial elbow lesion
Medial epicondyle apophysitis is a common overuse injury seen in young male pitchers and female gymnasts [10▪]. It occurs secondary to valgus stress with tension on the medial epicondyle via the flexor-pronator muscle mass and UCL [4▪▪]. Typically, patients present with an insidious onset of progressive medial elbow pain during pitching or handstands [10▪]. Physical examination is significant for tenderness over the medial epicondyle with localized edema. On occasion, a subtle flexion contracture may develop and valgus stress testing can induce pain without instability [4▪▪]. Radiographs may demonstrate widening of the apophysis or fragmentation of the ossification center [4▪▪]. Treatment is conservative; patients heal within 4–6 weeks with no functional deficit. For pitchers, a gradual return to throwing is indicated [10▪]. Gymnasts should abstain from handstands, floor routines, and vault initially, then gradually resume one activity at a time as tolerated [10▪]. If the patient is a pitcher, a position change may be considered, but the patient can still swing a bat [4▪▪]. In both baseball and gymnastics, consideration must be paid to proper throwing and jumping and landing techniques, respectively.
Untreated apophysitis may progress to an avulsion fracture of the medial epicondyle; therefore, prompt diagnosis and treatment are essential. Medial epicondyle avulsion fractures are traction injuries due to acute valgus stress and vigorous flexor-pronator muscle contraction. These forces cause failure through the apophysis. Patients present with an acute onset of medial elbow pain in cocking and early acceleration phases of throwing. The injury often prevents further athletic activity. Physical examination is significant for point tenderness over the medial epicondyle with swelling and bruising. Lack of full extension of the elbow, as well as instability with valgus stress testing, may be noted; however, UCL rupture is unlikely. Ulnar nerve sensory and motor function should be documented [4▪▪]. Imaging studies can show widening through the apophysis with possible displacement of the fragment (Fig. 2a). Treatment is based on the displacement of the medial epicondylar fragment. If there is minimal displacement and no rotation, nonsurgical management such as immobilization is indicated. If the fragment is large enough and displaced, reduction and fixation are indicated (Fig. 2b). Medial epicondyle avulsion fractures may preclude pitching for 4–6 months [4▪▪].
UCL insufficiency is a rare injury in skeletally immature individuals because the nearby physis is weaker than the UCL . Most UCL injuries in children are chronic in nature, secondary to repetitive microtrauma [10▪]. The patient will present with medial sided elbow pain and occasionally ulnar nerve parathesias. A pitcher may note a decrease in pitch velocity and control. Physical examination will uncover medial sided tenderness of the elbow, a flexion contracture, and pain with valgus testing in 30° of flexion. Radiographs should be reviewed to rule out a medial epicondyle fracture. Stress radiographs may be helpful, especially when compared with the contralateral side. MRI is used to establish the diagnosis. Treatment involves rest from pitching for 3 months. Initial therapy focuses on cryotherapy, elbow and shoulder motion, and strengthening and stabilizing the shoulder girdle. If symptoms in a skeletally immature competitive throwing athlete do not improve with 6 months of conservative treatment, surgical reconstruction of the UCL should be considered . Surgical reconstruction of the UCL has been shown to increase pitch velocity , when indicated in patients who fail conservative treatment.
Lateral elbow lesion
Panner disease is a self-limiting avascular necrosis of the ossific nucleus of the capitellum [10▪]. Panner disease can cause a lateral elbow compression injury in children secondary to repetitive compression forces across the radiocapitellar joint during late cocking and early acceleration phases of throwing . The typical patient is a 4–9-year-old with idiopathic osteochondrosis of the capitellum who presents with insidious onset of vague lateral elbow pain and stiffness [4▪▪]. Radiographs demonstrate fragmentation of the entire ossific nucleus [10▪]. Treatment involves rest and rehabilitation for approximately 4–8 weeks.
OCD of the capitellum or radial head is a lateral elbow stress injury that tends to affect 12–16-year-old male baseball pitchers or female gymnasts [10▪]. The typical patient presents with an insidious onset of lateral elbow pain with throwing or axial loading handstands [10▪]. Occasionally, mechanical symptoms such as locking and catching may be noted. Physical examination is notable for tenderness over the lateral aspect of the elbow, swelling, loss of full extension, and sometimes crepitus. Radiographs may show focal translucent areas in the anterior and distal most aspect of the capitellum with surrounding subchondral sclerosis [4▪▪] (Fig. 3a). MRI has a higher sensitivity than radiographs and is diagnostic for elbow OCD and chondral loose bodies [10▪] (Fig. 3b).
Posterior elbow lesion
Force dissipation in throwers that produces shear stresses across the posterior compartment of the elbow is termed valgus extension overload [10▪]. These shear stresses cause a posteromedial elbow impingement of the olecranon process against the fossa during the deceleration phase of throwing [4▪▪]. These patients present with posteromedial elbow pain, limited elbow range of motion, and mechanical symptoms, similar to patients who may have a loose body [10▪]. A confirmatory test for posteromedial impingement is pain along the posteromedial aspect of the elbow when an examiner forces a slightly flexed elbow into extension while applying a valgus force [10▪]. The examiner should also assess the integrity of the UCL. Treatment involves rest and activity modification. Surgical removal of osteophytes or loose bodies should be considered for those who do not respond to conservative therapy [10▪].
Olecranon apophysitis is a stress injury of the elbow affecting the posterior compartment. Patients present with pain during repetitive flexion and extension of the elbow. This injury is more common in baseball, lacrosse, and tennis players, as well as competitive fencers. Physical examination is significant for point tenderness at the tip of the elbow, localized swelling, and loss of terminal flexion and/or extension. Radiographs may demonstrate widening or asymmetry of the apophysis with sclerosis and fragmentation of the olecranon [10▪]. Treatment involves rest with 2 weeks of splint immobilization followed by activity modification and physical therapy.
Stress injuries of the wrist arise with repetitive loading across the distal radius physis. The injuries are colloquially referred to as gymnast's wrist. Chronic physeal injury is found in 25% of nonelite gymnasts, with increased prevalence in elite gymnasts . The patient usually presents with dorsal-sided wrist pain worsened by activities that load the wrist joint. Radiographs demonstrate widening and irregularities of the distal radial physis, as well as cystic changes of the metaphysis, similar to the findings in the proximal humerus in little leaguer's shoulder. Imaging can be done on both wrists to compare normal anatomy. MRI of the wrist in gymnasts can identify specific injury patterns, such as diffuse bone marrow edema of the carpal bones (Fig. 4), osteochondral defects, triangular fibrocartilage tears, and scapholunate ligament tears . Treatment involves rest for 4–6 weeks, training modification, and bracing when necessary.
Fractures in children can be subdivided into fatigue (stress) fractures and insufficiency fractures . Whereas stress fractures arise when normal bone is injured by abnormal activity , insufficiency fractures occur when abnormal bone is injured by normal activity. Stress fractures in the upper extremity of children are rare. Particular attention should be paid to stress fractures when the pain is localized to the middle of the humerus or ulna. A recent study demonstrated ulnar shaft stress fractures in honor guard trainees . On physical examination, these patients have tenderness to palpation of both midshaft ulna bones as well as decreased range of motion during pronation and supination . MRI offers advantages over plain radiographs for detecting stress fractures. In fact, early radiographs may detect as few as 15% of stress fractures in an acute setting . MRI has improved specificity and no ionizing radiation, and visualizes lesion in both bone and soft tissue .
Additionally, the examiner should consider stress fractures if the patient is an athlete with a recent change in routine. Muscles can gain strength faster than bones; this can lead to fractures in athletes who increase their workload . Upper extremity stress fractures are associated with throwing sports or activities that strain the upper extremity, such as wrestling and gymnastics . Stress fractures may also happen in patients who return to athletics after being immobilized for a previous injury.
ANCILLARY TESTS TO CONSIDER
There are many causes for stress injuries in the upper extremity. Previously, we have explored overuse injuries. A high index of suspicion is used to detect any underlying cause for insufficient bone formation, especially if the patient does not respond to the usual treatment regimen. The physician ought to consider the following tests: serum 25 dihydroxy vitamin D, calcium, thyroid and parathyroid hormone, phosphorus, and bone-specific alkaline phosphatase, as well as urine N telopeptides (NTX) to assess for appropriate collagen cross-links. A deficiency in one or more of these markers may uncover why the usual modalities of stress injury treatment fail. Pediatric dual-energy X-ray absorptiometry will also confirm osteopenia, and may be used subsequently to monitor success of treatment. A complete blood count with differential, erythrocyte sedimentation rate, and C-reactive protein test may confirm infectious or neoplastic causes that mimic overuse injuries. Furthermore, genetic testing for connective tissue disorders that potentiate instability should be considered in patients with multiple stress injuries at unrelated sites. Throwing mechanics may be evaluated by a sports physical therapist in cases involving overhead throwing athletes. Pitchers with better biomechanics generate lower humeral internal rotation torque, lower elbow valgus load, and increase efficiency, which facilitate injury prevention .
Upper extremity stress injuries in children are more common than acute traumatic fractures and dislocations . This review outlines the potential causes of a variety of stress injuries and will allow improved evaluation and management. Most upper extremity stress injuries initially are treated conservatively and symptoms improve without long-term detriment. However, delays in diagnosis can affect the treatment regimen and the ultimate outcome. Education of parents, coaches, and pediatricians is necessary for prevention and treatment of overuse injuries in the pediatric population.
Conflicts of interest
There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING
Papers of particular interest, published within the annual period of review, have been highlighted as:
- ▪ of special interest
- ▪▪ of outstanding interest
Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 150).
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