Background The forearm flexors (FF) are a stabilizing biomechanical aspect of the medial elbow. However, there are no studies investigating the association of concomitant UCL injuries and FF injuries in throwing athletes.

Objective Our hypothesis is a considerable number concomitant FF injuries occur with (medial) UCL injury in throwing athletes. Additionally, we hypothesized that an increased severity of UCL injury in throwers is associated with a greater likelihood of concomitant FF injury.

Design Descriptive retrospective epidemiological study.

Setting Academic, tertiary care medical center.

Patients Patients with sports-related throwing UCL injuries from 1/1/10 to 12/31/19 for patients aged 12–24 years.

Assessment of Risk Factors Electronic medical records and key word searches identified all patients. A board certified and fellowship trained Musculoskeletal Radiologist reviewed all imaging studies.

Main Outcome Measures The primary study outcome measures planned before data collection included: UCL and FF structural injury on advanced imaging (MRI and/or MRI-Arthrogram), location of UCL injury, concomitant FF injury with UCL injury, UCL-Reconstruction (UCL-R) and associated FF injury, and concomitant FF injury and complete UCL tear.

Results Fifty-four patients (46 male, 8 female, mean age 17.1 years, SD 2.3) were included. Fifty-four UCL injuries (21 complete ruptures, 16 proximal partial injuries, 17 distal partial injuries) were confirmed by magnetic resonance imaging (MRI). Twenty-eight FF injuries (22 strains, 6 tears) were diagnosed with MRI and/or MRI-arthrogram. There was a significant association between sustaining a FF injury and UCL reconstruction (UCL-R) (X² = [1, N = 54], = 3.97, P = .046) (15/22, 68.2%), as well as FF injury and UCL injury location (X² = [1, N = 33], = 3.86, P = .049) (10/17, distal partial UCL injury, 58.8%). Analysis of FF injury and complete UCL tear is not significant (X² = [1, N = 54], = 3.02, P = .08) (14/21, 66.7%).

Conclusions FF injury is related to UCL injury in throwing athletes. Future prospective studies should investigate association of FF and UCL injury in a throwing athlete as a means to prevent further injury.