Context: Screening programs to identify negative ulnar nerve adaptations in throwing athletes can help minimize injury risk and individualize treatment programs prior to the onset of symptoms. However, it is currently unclear how the ulnar nerve structurally adapts chronically in professional baseball pitchers.

Objective: To compare ulnar nerve ultrasound structural characteristics between the throwing (dominant) and non-throwing control (non-dominant) elbows in professional pitchers, with a secondary purpose of comparing ultrasound structural characteristics between subluxating and non-subluxating ulnar nerves.

Design: Cross-sectional study.

Setting: The beginning of the 2022 Minor League Baseball spring training of a single professional baseball organization.

Participants: All asymptomatic professional baseball pitchers from a single organization.

Main Outcome Measures: Bilateral elbow ultrasound examinations by a musculoskeletal radiologist for subsequent image quantification of ulnar nerve properties (echogenicity, area, circularity), as well as to identify ulnar nerve subluxation.

Results: Overall, 67 male professional baseball pitchers were enrolled. No significant bilateral differences in ulnar nerve cross-sectional area (dominant: 0.2 cm2 vs. non-dominant: 0.2 cm2, p=0.4), echogenicity (137 pixel intensity vs. 128 pixel intensity, p=0.07), or circularity (0.67 vs. 0.69, p=0.4) were observed. Ulnar nerve echogenicity was significantly lower in subluxating dominant ulnar nerves compared to non-subluxating dominant ulnar nerves (127 pixel intensity vs. 143 pixel intensity, p=0.006), while no significant differences in ulnar nerve area (0.2 mm2 vs. 0.2 mm2, p=0.1) or circularity (0.68 vs. 0.66, p=0.4) were observed between groups.

Conclusions: The ulnar nerve of the throwing elbow had similar cross-sectional area, echogenicity, and circularity compared to the non-dominant ulnar nerve. Nerve echogenicity was significantly decreased in subluxating ulnar nerves, however further research is necessary to determine why this difference exists and the potential direction of causality.

ulnar nerve, ultrasound, adaptation, baseball, elbow
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Author notes

Ryan Paul ([email protected])

Alim Osman ([email protected])

Chizoba Umeweni ([email protected])

Levon Nazarian ([email protected])

Austin Looney ([email protected])

Manoj Reddy ([email protected])

Michael Ciccotti ([email protected])

Steven Cohen ([email protected])

Brandon Erickson ([email protected])

Paul Buchheit ([email protected])

Joseph Rauch ([email protected])

Stephen Thomas ([email protected])

Ryan Paul: None

Alim Osman: None

Chizoba Umeweni: None

Levon Nazarian: None

Austin Looney: None

Manoj Reddy: None

Michael Ciccotti: American Orthopaedic Society for Sports Medicine: Board or committee member. Major League Baseball Team Physicians Association: Board or committee member.Orthopaedic Learning Center: Board or committee member.

Steven Cohen: American Orthopaedic Society for Sports Medicine: Board or committee member. Arthrex, Inc, Major League Baseball: Research support. CONMED Linvatec: Paid consultant. International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine: Board or committee member. Slack, INC: Publishing royalties, financial or material support. Zimmer: IP royalties; Paid consultant; Paid presenter or speaker.

Brandon Erickson: Education payments from Arthrex, DePuy, Smith & Nephew, Pinnacle, and Gotham Surgical. Research support/consultation payments from Arthrex, DePuy, Linvatec, Smith & Nephew, and Stryker. Consulting fees from Arthrex. AAOS, AOSSM, and ASES: Board or committee member. PLOS One: Editorial or governing board.

Paul Buchheit: None

Joseph Rauch: None

Stephen Thomas: None

IRB Approval: Approved by Thomas Jefferson University IRB #21D.056