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Although the Little League pitchers in the MRI study showed excellent compliance with guidelines for pitch counts and rest days, year-round play and single-sport specialization warrant more attention as factors in arm woes, the study's authors conclude.
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Published 7/1/2017
Terry Stanton

Abnormal Elbow Findings Identified in Little League Throwers

"Strikingly high" number of arm problems seen in many players who followed pitching guidelines
A study of Little League baseball players before and after a season of play found that arm pain and MRI abnormalities of the medial elbow were common even in players who complied with the Little League throwing guidelines, especially those who played year round. Study data also support the conclusion that pain and injury are more closely related to the cumulative number of throws and not necessarily the number of pitches in a given game.

"Overuse injuries in the young throwing athlete have been getting a lot of media attention lately due to a so-called epidemic of overuse injuries," said Andrew Pytiak, MD, of Rocky Mountain Hospital for Children, who presented the study during the 2017 AAOS Annual Meeting in San Diego. "Two and a half million American children play Little League baseball. Of these, 18 percent to 20 percent will experience arm pain during the course of a season. Risk factors include pitching for consecutive days, playing on multiple teams, and playing multiple games per day."

Little League Baseball implemented pitching guidelines in 2007 in response to concerns about these overuse injuries, Dr. Pytiak, first author of the study, explained. The guidelines restrict the number of pitches a player can throw in a game and specify the number of days of rest needed after pitching.

The study
The researchers evaluated 26 Little League players age 10 to 13 years. Prior to the start of the season, players underwent bilateral elbow MRI. In addition, a physical examination and questionnaire data addressing playing history and arm pain were recorded. At the end of the season, the physical exam and MRI were repeated. The radiologists were blinded. During the season, player statistics including innings played, pitch counts, and guideline compliance were recorded.

Of the players, 11 (42 percent) were pitchers, and 14 (54 percent) were pitchers/catchers. Seventy-seven percent were right-hand dominant.

Subjects were excluded if they had a contraindication to an MRI, if they were unable to tolerate either the preseason or postseason MRI, or if they sustained a season-ending injury. The throwing history focused on several key factors including years of play, primary position(s) played, months of play per year, number of teams each played on, private coaching history, and age at which various pitches (change-ups, sliders, and curve balls) were initiated. Each player was queried about having a prior history of arm pain or a throwing injury. Additionally, patients were asked whether they were familiar with the Little League throwing guidelines, and whether they had ever exceeded the guidelines prior to the start of the season.

Pre- and postseason physical examinations were performed by one of two board-certified orthopaedic surgeons. The surgeons standardized the exam, which focused on tenderness to palpation, passive range of motion, strength, and stability testing.

Arm problems: MRIs pre- and postseason
At the beginning of the season, 9 of 26 players (35 percent) had an abnormal MRI finding. Six patients had one positive finding and three had two positive findings.

After the season, 12 of 25 players (48 percent) had an abnormal MRI. Compared to the preseason MRIs, 8 of these 12 abnormalities represented new findings or progression of a previously visualized abnormality. Most players with an abnormal MRI had a single finding but 4 players (16 percent) had multiple new or worsened abnormalities.

The abnormalities primarily involved the medial side of the elbow, including two cases of fragmentation of the medial epicondyle, five cases of edema within the medial epicondyle apophysis, four cases of edema of the distal humeral metaphysis, and one partial disruption of the ulnar collateral ligament. MRI assessment revealed significant widening of the distal humeral physis during the season (1.54 mm preseason versus 2.31 mm postseason, P < 0.001), whereas no thickening of the ulnar collateral ligament was observed (1.34 mm preseason versus 1.41 mm postseason, P = 0.41).

Postseason physical examination revealed that players lost an average of 11.2 degrees of shoulder internal rotation (P < 0.001), gained an average of 0.4 degrees of external rotation (0.89), and lost 10.8 degrees of total arc of motion during the season (P = 0.02). Additionally, players developed 1.4 degrees of elbow hyperextension compared to their preseason assessment (P = 0.14). A significant positive correlation was observed between total arc of motion change from pre- to postseason and distance of the ulnar collateral ligament to the medial epicondyle physis (P = 0.004). No other physical examination findings were noted to change during the season, including shoulder and elbow stability.

During the course of the season, 7 of 25 players (28 percent) experienced arm pain, and one player's symptoms were severe enough that he sought medical attention. The arm pain was localized to the shoulder in 2 of 25 players (8 percent), the elbow in 3 of 25 players (12 percent), and both locations in 2 of 25 players (8 percent). Preseason variables, in-season variables, and physical examination findings were not found to be significantly correlated with arm pain (P > 0.05).

What about the guidelines?
The authors reported that players and coaches demonstrated "excellent" compliance with the Little League pitch count limits and mandatory rest days, with no violations occurring. However, they noted, "Much poorer compliance was documented with respect to Little League's nonmandatory, nonenforced recommendations. In our cohort, 56 percent threw off-speed pitches (curveballs and sliders), 68 percent failed to rest from baseball for 3 months a year, and 8 percent played on multiple teams during the same season, all against Little League recommendations."

Of the 12 patients with a postseason MRI abnormality, Dr. Pytiak said, 83 percent violated at least one of these three guidelines, compared to 62 percent of those without a postseason MRI abnormality (P = 0.08). In the subset of eight players with a new/worsened postseason MRI abnormality, 88 percent violated at least one guideline compared to 65 percent with no new/worsened finding (P = 0.14).  Of the seven players who complained of postseason arm pain, 71 percent violated at least one guideline, which was similar to 70 percent in those with no self-report of arm pain.

"We find these numbers to be strikingly high and call into question the overall effectiveness of the Little League pitching guidelines," Dr. Pytiak said. "More attention may need to be paid to year-round play and single-sport specialization and not exclusively to pitch counts. Nearly 70 percent of our participants played year-round."

Co-authors, with Dr. Pytiak, of "Are the Current Little League Guidelines Adequate? A Single-Season Prospective MRI Study" are Phil Stearns, CPNP; Joanna Roocroft, MA; Jerry Dwek, MD; Peter Kruk, MD; Tracey Bastrom, MA; and Andrew Pennock, MD.

The original version of this article appearing in the print edition misidentified the presenter of the study. Andrew Pytiak, MD, presented the study and is first author.

Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom Line

  • Overuse injuries in youth baseball throwers are a concern, with 18 percent to 20 percent of Little League players experiencing arm pain.
  • This study involved 26 Little League players who underwent physical examination and elbow MRI before and after a season.
  • Preseason, 35 percent of players had abnormal MRI findings; postseason, 48 percent had abnormal findings, with 16 percent having new or worsened conditions.
  • Players demonstrated a high number of arm problems despite "excellent" compliance with Little League pitch count and rest guidelines. The authors recommend that more attention be paid to the effect of year-round play and single-sport specialization.