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4 Risk Factors for Tommy John Ligament Surgery in Youth Pitchers

Baseball results in stress on the elbow and ulnar collateral ligament (UCL). The UCL (Tommy John Ligament) is the primary stabilizer of the elbow against stress on the inside of the elbow. Acute injuries and/or chronic degeneration of the UCL (Tommy John Ligament) can lead to pain, decreased control, and decreased velocity, all affecting a pitcher’s performance and longevity. Depending on the severity of the UCL (Tommy John Ligament) injury, time missed after nonoperative treatment can range from several days to 6 months. Although surgical techniques have evolved over the past 3 decades, time missed after surgical treatment can range from 12 months to greater than 18 months.

UCL (Tommy John Ligament) Anatomy

The UCL (Tommy John Ligament) is typically broken down into three sections:

  1. Anterior bundle
  2. Posterior bundle
  3. Transverse bundle

Risk Factors for Tommy John Ligament Surgery

Recently, research has analyzed potential risk factors for elbow overuse injuries. Previous search on deformation of the UCL (Tommy John Ligament) in youth pitchers:

1. Changes in Ligament: Jazrawi et al used conventional magnetic resonance imaging (MRI) to evaluate the elbows of 14 non painful, young nonprofessional pitchers, but they found that UCL (Tommy John Ligament) signal changes were uncommon in this cohort. Kooima et al, showed that UCL (Tommy John Ligament) abnormalities detected by MRI are common in non painful professional baseball pitchers. Specifically, they found that increased UCL (Tommy John Ligament) thickness, signal heterogeneity, or UCL (Tommy John Ligament) disruptions were present in 87% of dominant elbows. Nazarian et al used stress ultrasound (SUS) and found that the mean thickness of the anterior band of the UCL (Tommy John Ligament). Ciccotti et al found an increase in UCL (Tommy John Ligament) thickness may be one of the first changes to develop in young professional baseball pitchers.

2. Degenerative Changes: Wright et al used plain elbow x-rays to examine a cohort of 56 professional baseball pitchers without pain and found that degenerative changes developed over time; however, these changes did not correlate with time spent on the Major League Baseball disabled list.

3. Increase in Calcification: Nazarian et al noted calcifications were more common in pitchers using SUS. Cicotti et al found no statistically significant difference in the presence of calcifications.

4. Increases in Joint Gaping: Ciccotti et al used SUS to determine the amount of space which opened in the elbow of cadavers.  The release of the anterior bundle of the UCL (Tommy John Ligament) resulted in the greatest increase in joint gapping, as measured by SUS. Nazarian et al found greater degree of ulnohumeral joint widening with valgus stress. However, Ciccotti et al did not find a difference in joint gaping using SUS at rest or with a valgus stress applied.


Understanding risk factors for UCL or Tommy John surgery still requires more research, especially as techniques improve. Overall, it seems the SUS is the best method for imaging the UCL (Tommy John Ligament). UCL thickness seems to be one of the first changes in youth professional baseball pitchers. Future studies must analyze if SUS detected thickness predicts UCL injury or Tommy John surgery in the future.


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