Prevalence and imaging characteristics of the transverse trochlear ridge on elbow MRI and radiographs in youths.

OBJECTIVES

The transverse trochlear ridge (TTR) is an anatomic variant of the ulnar trochlear groove. This study evaluated the prevalence and imaging characteristics of the TTR on MRI and radiographs in children, adolescents, and young adults.

MATERIALS AND

METHODS

This retrospective analysis included 178 MRI examinations and 95 corresponding radiographs of patients aged 4-25 years. The presence or absence of the TTR was evaluated. The width, height, and depth of the TTR were measured. The sensitivity and specificity of radiography to detect TTRs were evaluated compared with MRI as the reference standard. Binomial logistic regression analysis was used to compare the effects of age and gender on the prevalence of TTR.

RESULTS

TTR was observed on 149 of 178 (83.7%) elbow MRIs. Mean width, height, and depth were 20.6 ± 3.0 mm, 4.2 ± 1.2 mm, and 2.0 ± 0.7 mm, respectively. Comparing increasing age in years with the prevalence of the TTR revealed a statistically significant odds ratio of 1.119 (95% CI; p = 0.012). The maximum predicted probability was a prevalence of 96% for TTR at the age of 25. Sensitivity and specificity values of the TTR on radiographs were 29.6% and 92.9%. Cohen's kappa for the inter-rater agreement for the prevalence of the TTR on MRI was 0.740.

CONCLUSIONS

The predicted prevalence of TTR demonstrated an age-dependent increase in the prevalence up to 17 years of age. The size of the TTR also demonstrated an age‑dependent increase during adolescence. The high frequency of TTR on MRI indicates that TTR represents a common variant.