Risk factors for elbow injuries in professional baseball players based on ultrasound images: a prospective cohort study of 56 players

Masahiro Ikezu; Shintarou Kudo; Issei Noda; Takanori Kubo; Hidetoshi Hayashi

doi:10.1016/j.jseint.2025.04.029

Risk factors for elbow injuries in professional baseball players based on ultrasound images: a prospective cohort study of 56 players

JSES Int. 2025 May 22;9(5):1820-1824. doi: 10.1016/j.jseint.2025.04.029. eCollection 2025 Sep.

Authors

Masahiro Ikezu^{1

2}, Shintarou Kudo^{1

2}, Issei Noda^{1

3}, Takanori Kubo⁴, Hidetoshi Hayashi⁴

Affiliations

¹ Inclusive Medical Science Research Institute, Morinomiya University of Medical Sciences, Osaka, Japan.
² AR-Ex Medical Research Center, Tokyo, Japan.
³ Department of Rehabilitation, Ashiya Orthopedics Sports Clinic, Hyogo, Japan.
⁴ Department of Orthopedic Surgery, AR-Ex Oyamadai Orthopedic Clinic, Tokyo, Japan.

Abstract

Background: Risk factors for the development of elbow injuries, focusing on the function of the flexor digitorum superficialis (FDS) and the structure of the ulnar nerve, have not been fully clarified. This study aimed to prospectively investigate the ring-down artifact (RDA) under gravity load and gravity load with FDS contraction conditions and the cross-sectional area (CSA) of the ulnar nerve and clarify the risk factors for elbow injuries in professional baseball players.

Methods: We enrolled 56 professional Japanese baseball players without elbow pain. The measurements were RDA under gravity load and gravity load with FDS contraction, and the CSA of the ulnar nerve at the Struthers arcade, cubital tunnel, and Osborne's ligament. We prospectively investigated the development of elbow injuries over a 1-year period. Statistical analysis was performed using Fisher's exact test, and the relative risk (RR) was calculated.

Results: The development of elbow injuries was associated with the following variables: the presence of RDA under gravity load (P < .01, RR: 5.22), the presence of RDA under gravity load with FDS contraction (P = .02, RR: 3.26), CSA at Struthers arcade ≥10 mm² (P < .01, RR: 6.71), CSA at cubital tunnel ≥10 mm² (P < .01, RR: 36.56), and CSA at Osborne's ligament ≥10 mm² (P < .01, RR: 4.57).

Conclusion: The RDA under gravity load, FDS contraction conditions, and increased CSA of the ulnar nerve were associated with the development of elbow injuries in professional baseball players.

Keywords: Baseball; Elbow injury; Flexor digitorum superficialis; Ring-down artifact; Risk factors; Ulnar nerve.