Medial Epicondyle Apophysitis (Little League Elbow)

Etiology

The biomechanics of a typical overhead throw or serve places significant valgus stress on the elbow.[4] Sports involving repetitive overhead arm motions, such as baseball, softball, volleyball, tennis, football, swimming, and javelin throwing, may lead to apophysitis of the medial epicondyle.[5] Baseball pitching is the activity most commonly associated with medial epicondyle apophysitis. Risk factors for developing MEA among baseball players include a high volume of pitches per game, baseball pitch velocity, continued pitching time despite arm fatigue, and participation on multiple baseball teams.[5] The alternate position of catcher, as well as the number of innings and months, pitched per year, may also be associated with medial epicondyle apophysitis, but additional research is required.[6]

Epidemiology

Medial epicondyle apophysitis occurs only in children 6-15 years of age due to fusion of the apophyseal ossification center around age 15. Of all youth sports injuries, about half are due to overuse.[7] According to the high school sports-related injury surveillance studies, the overall risk of injury increased by 15 percent between 2011 and 2016, and the proportion of baseball injuries associated with the elbow nearly doubled in the same time frame. Factors include increased youth engagement in organized sports, elevated competition at younger ages, playing on multiple teams simultaneously, and earlier sport specialization, often with year-round play.[8][9][10] 

In baseball, the prevalence of medial elbow pain increases with age, and the prevalence of medial epicondyle apophysitis peaks between the ages of 11 to 12, with a rate of about 30 percent. X-ray screening of Little League Baseball regional and national championship contenders showed that 57 percent had radiographic evidence of medial epicondyle displacement.[11] Regarding gender demographics, females typically have more sports-related overuse injuries, but since so many young males play baseball, the incidence of medial epicondyle apophysitis is likely higher in boys.[11][12] It is difficult to determine if males are indeed at higher risk for medial epicondyle apophysitis physiologically than females or if they just have increased exposure to MEA-inducing biomechanics.

Pathophysiology

Medial epicondyle apophysitis results from repetitive valgus stress of the ulnar collateral ligament exerting traction on the medial epicondyle of the humerus. Excessive stress on this kinetic chain causes injury at the weakest point – the open apophysis, which is five times weaker than the UCL. With repetitive, highly forceful valgus stress, as seen in baseball pitching or another overhead throwing, particularly in the late cocking phase of the throw, the apophysis can get inflamed and partially separate from the distal humerus. Continued stresses on this weakened connection can complicate the injury with an acute avulsion fracture.[2]

History and Physical

Prompt and accurate diagnosis of medial epicondyle apophysitis requires a thorough history and physical of young athletes presenting with medial elbow pain. Important historical clues include an age range between 6 to 15 years old with a history of a sporting activity requiring repetitive overhead motions. If the patient regularly plays a sport, providers should inquire about the position played, frequency and duration of athletic activity, and type of overhead arm motion required for the sport. The typical presentation of medial epicondyle apophysitis is an insidious onset of progressively worsening medial elbow pain associated with overhead throwing and decreased throwing performance and endurance.[4] Additionally, in patients whose medial epicondyle apophysitis is complicated by an avulsion fracture, they may describe acute pain with a “pop” sensation at the time of avulsion injury.[12]

The physical exam is vital for the diagnosis of medial epicondyle apophysitis. The patient will typically have medial epicondyle point tenderness, medial elbow pain with valgus stress, and sometimes subtle elbow contractures.[8][4] Special exam maneuvers developed for UCL injury can be used for medial epicondyle apophysitis, given the similarity of injuries. The moving valgus stress test is the gold standard exam for UCL injury with 100% sensitivity and 75% specificity.[13] This exam technique consists of placing a constant valgus torque to a fully flexed elbow as it is fully extended. The test is positive if medial elbow pain is reproduced. The “milking maneuver” consists of applying a valgus torque, with the elbow flexed at 90 degrees, while anchoring the elbow and supinating the wrist.[8] 

Avulsion fractures of the medial epicondyle can have additional exam findings, including elbow instability, reduced ROM, and ulnar neuropathy.[14] In addition to a thorough elbow exam, providers should complete a neurological exam to evaluate for ulnar nerve deficits and to rule out other causes of arm pain and weakness that could originate from the wrist, shoulder, or cervical spine.[4]

Evaluation

Imaging is a vital part of evaluating young athletes with risk factors and an exam concerning medial epicondyle apophysitis. Initial studies should include bilateral anterior, posterior, and lateral plain radiographs of the elbows in addition to a lateral image of the elbows flexed at 90 degrees with the application of valgus stress.[8] Medial epicondyle apophysitis appears as widening of the medial epicondylar physis with a ragged and sclerotic appearance of the border of the ossification center.[15] Image (a) shows MEA in the right elbow and image (b) shows a normal left elbow [15]. Elbow instability is identified radiographically as greater than 3 millimeters of joint separation in the stress radiograph.[8] In the clinic setting, point-of-care ultrasound (US) may be helpful as it has an 88% positive predictive value in identifying medial epicondyle apophysitis when used by an experienced provider.[16] However, the meaning of a negative US in a symptomatic patient has not been studied. Therefore, radiographic evaluation is still recommended.

Accurate diagnosis of medial epicondyle apophysitis requires bilateral radiographs to compare the patient’s anatomy and better evaluate for an avulsion fracture. The ossification centers (physes) close at inconsistent ages during adolescence, and bilateral comparison allows the radiologist to evaluate whether the patient’s physes are still open. Bilateral imaging is also helpful in identifying a missing ossification center. Avulsion fractures should be suspected if an ossification center is missing unilaterally or if the medial epicondyle apophysis is missing, but the trochlear, olecranon, or lateral epicondyle ossification centers are present. Computerized tomography and magnetic resonance imaging are only indicated for medial epicondyle avulsion fractures or apophysitis not responding to therapy. They are helpful in more accurately determining the degree of epicondylar displacement and the need for operative versus non-operative management.[17][8][18] In older athletes with near closure of their apophysis, an MRI may be indicated to evaluate for concurrent UCL tears.[16]

Treatment / Management

The foundation of treatment for medial epicondyle apophysitis is rest from the exacerbating sport and cessation of its repetitive overhead arm motion. Athletes should fully rest the affected arm for 4 to 6 weeks. The use of ice and analgesics such as acetaminophen or non-steroidal anti-inflammatory medications may be used for pain control. After refraining from overhead motions for at least 6 weeks, if pain-free, athletes may begin physical therapy focusing on elbow and shoulder strengthening exercises and can initiate a gradual return to a throwing program over the subsequent 6 weeks, with set limitations on throws/pitches.[4][19] Unfortunately, recurrence rates are high and may require an even more conservative graded rehabilitation. If symptoms continue to return after periods of pitch/throw rest, the athlete should cease play for the remainder of the sports season and consider transitioning to a less demanding position or even refraining from the sport until the fusion of the apophysis.[20]

A common complication of medial epicondyle apophysitis is an avulsion fracture of the medial epicondyle, which responds well to nonoperative treatment. Treatment begins with a long arm cast for 2 to 4 weeks followed by a posterior splint accompanied by passive range of motion exercises 3 to 5 times daily. Once the patient has no tenderness to the medial epicondyle, the patient wears a hinged elbow brace for 6 to 8 weeks. After brace removal, the patient can begin physical therapy to avoid strengthening the flexor and pronator muscle groups until the bony union has been confirmed.[14] If the patient develops elbow laxity, instability, or greater than 75% displacement of the medial epicondyle avulsion fracture, the patient will need surgical management with open reduction and internal fixation (ORIF). Post-surgical care is similar to those treated non-operatively.[14] For patients with 25% to 75% fracture displacement, studies have shown no difference in outcome between surgical versus non-surgical treatment.[21]

Differential Diagnosis

The differential for medial elbow pain remains narrow, given its specific anatomical location. Important diagnoses to rule out are ulnar collateral ligament tear, medial epicondylopathy, ulnar neuropathy, or local muscular injury. Partial or full thickness UCL tear presents similar signs and symptoms as medial epicondyle apophysitis, but the patient is usually greater than 15 years old.[4][16] Medial epicondylopathies can also present similarly to medial epicondyle apophysitis but typically affect skeletal maturity and distinguished radiographically.[22] 

Ulnar neuropathy should be suspected if there is associated paresthesia in an ulnar nerve distribution.[23] Injury of the flexor-pronator muscle group can present with muscle weakness and elbow pain aggravated by wrist flexion.[8] Valgus extension overload syndrome can also occur in overhead throwing athletes. Still, the pain is located at the posteromedial elbow, worse at the end of a throw, and is associated with elbow locking and crepitus.[10] As with all musculoskeletal complaints, the clinician must evaluate the muscle, tendon, ligaments, and nerves for injury and should evaluate the entire extremity.

Prognosis

The prognosis of medial epicondyle apophysitis is generally excellent, with most cases resolving with armrest or when the apophysis closes.[7] One-third of athletes return to their sport.[19] However, recurrence of symptoms is common.[20] In a small number of cases, the apophysis does not fuse and can be complicated by residual ossicles after skeletal maturity, sometimes leading to persistent pain.[7] Nonunion and avulsion fractures are more likely in athletes who do not take appropriate rest and rehabilitation measures.[2]

Complications

Medial epicondyle apophysitis complications can include the common complication of medial epicondyle avulsion fracture and the less common complications of entrapment of the avulsed bone in the elbow joint space, ulnar nerve entrapment, residual ossicles, and persistent pain. Nonunion of an avulsed epicondyle can result in residual bone remaining in the joint space, causing locking of the joint, persistent pain, or entrapment of the ulnar nerve. Each of these complications is an indication for evaluation for surgical management.[12] After skeletal maturation, some athletes with resolved medial epicondyle apophysitis can still experience persistent pain from residual ossicles. Resection of the ossicles or tubercleplasty may improve symptoms.[7]