CORR Insights®: Does Youth Baseball Result in Morphologic Changes of the Lateral Elbow? A Prospective MRI Study

Where Are We Now?

Several studies in pediatric sports medicine have reported that osseous and soft-tissue changes can occur in a developing shoulder that is put under repetitive throwing stress [4, 8, 9]. Moreover, in young throwing athletes with osteochondritis dissecans lesions of the capitellum, structural changes in the elbow such as radial head enlargement portend poor treatment outcomes, such as a lack of lesion healing and advancing elbow pain and disability [1, 2, 5]. However, there is a knowledge gap as to whether repetitive throwing stress can similarly affect the architecture of the developing elbow as it does in the shoulder. The basic science that could be used to explain such an effect is conflicting. For example, Wolff’s law [10] postulates that increased forces across the lateral elbow might be relieved by enlargement of the radiocapitellar joint. This would diffuse compressive forces over a larger surface area. Alternatively, repetitive compression inhibits chondrocyte growth, which may limit enlargement of the radiocapitellar joint or cause another deformity in the developing elbow [6, 7]. Therefore, it is essential to understand how repetitive valgus torque of the elbow from competitive baseball may lead to any stress-induced remodeling changes, including radial head and capitellum overgrowth, which can lead to early degeneration as well as those poor treatment outcomes in patients with capitellar osteochondritis dissecans.

To investigate this dilemma, Harkin et al. [3] devised an appropriately powered and uniquely rigorous study in youth baseball players. They investigated whether repetitive valgus torque of the elbow from competitive baseball leads to stress-induced remodeling changes, including radial head and capitellum overgrowth. Some of their principal methods should be highlighted here, because it is uncommon to read a study with such attention to methodologic detail. The authors followed youth baseball players prospectively with baseline bilateral elbow MRI scans, using each athlete’s nondominant elbow as their own internal control, and were able to obtain follow-up imaging at 3 years. They used well-described, precise measurement techniques and tested them for intrarater and interrater reliability. The raters were blinded to arm dominance. High-level paired, longitudinal statistical analyses were used including repeated-measure analysis of variance. In light of this attention to detail, the fact the authors found no evidence of radiocapitellar joint overgrowth and no morphologic changes after cessation of baseball participation in this cohort should be taken at face value. This is important because it suggests that although both adaptive and pathologic changes are well-documented in the throwing shoulder of young athletes in response to repetitive stress, similar ominous changes in the radiocapitellar joint may not occur.

Where Do We Need To Go?

Despite the methodologic rigor of the study, there are some gaps in our knowledge of the throwing elbow in young athletes. Future studies might also focus on radiocapitellar changes in athletes in repetitive overhead sports other than baseball (such as tennis, volleyball, and water polo). Additionally, researchers could focus on youth baseball pitchers and catchers who play year-round, because these children throw more balls per game and play more games per year than players in other positions and those who do not play year-round. Although it seems to be a logical extension to study elite athletes (such as college and professional athletes) using a case-control study, given the rarity of structural alterations after repetitive valgus stress, this population likely has a Darwinian selection bias away from pathologic changes that would have precluded such a career. In other words, players who experience pathologic changes in the elbow would be less likely to sustain play into the highest elite levels. Therefore, a continued study of this phenomenon in young athletes is warranted, because it is important to specifically understand which young athletes are at the greatest risk of pathologic and potentially permanent elbow morphologic changes that could lead to disability later in life.

How Do We Get There?

The next logical step would be to apply the same study methods to other populations of interest, such as year-round baseball players (particularly pitchers and catchers) and athletes who perform repetitive overhead motions in other sports. Future work on these more-expansive cohorts may uncover a particular at-risk demographic. Moreover, a study focusing on patients who initially presented with elbow pain may reveal morphologic changes that were not noted in the current study. Injuredor early symptomatic elbows may be more likely to demonstrate adaptive or pathologic changes than asymptomatic throwing elbows.

Nonetheless, the authors [3] should be applauded for their meticulous study design, and we should take a page out of their playbook. Adequately powered negative findings should be confidently trusted in this cohort, and this study’s methodology should be expanded to other cohorts of interest in future work. Identifying specific cohorts at the greatest risk of pathologic changes in the radiocapitellar joint would allow for the establishment of guidelines to prevent long-term sequelae, particularly in early single-sport specialized athletes participating in high-risk sports.