Optimal Elbow Angle for Sonographic Visualization of the Ulnar Collateral Ligament

Objective: To formally examine the sonographic appearance of the elbow ulnar collateral ligament (UCL) at 30 degrees versus 70 degrees of elbow flexion in asymptomatic baseball pitchers. Design: A prospective, cross-sectional design. Setting: Sports medicine clinic in a tertiary academic medical center. Participants: Thirty asymptomatic adolescent baseball pitchers 13-18 years of age (mean 15.8 years), with at least 3 years of continuous pitching experience and no significant history of elbow pain or injury. Methods: Static sonographic images of the bilateral UCLs were obtained at 30 degrees and 70 degrees of elbow flexion by a single experienced examiner. Images were anonymized and randomized into a slide set. Three clinicians with different levels of ultrasound experience reviewed the static 30 degrees and 70 degrees images for each elbow and chose their preferred image based on UCL conspicuity. The clinicians reviewed a re-randomized slide set 1 week later. A different study co-investigator measured UCL cross-sectional area (CSA) on all images using ultrasound machine electronic calipers. Main Outcome Measures: Preference for the sonographic conspicuity of the UCL at 30 degrees versus 70 degrees of elbow flexion, and UCL CSA at 30 degrees versus 70 degrees of flexion. Results: Each clinician demonstrated a significant preference for UCL images obtained at 70 degrees of flexion when compared to those obtained at 30 degrees (80.3% overall preference for 70 degrees, P < .001). There was no statistically significant effect of clinician experience or arm dominance on image preference. The sonographically determined CSA of the UCLs were on average 1.4 mm(2) greater at 70 degrees than at 30 degrees of flexion (P < .001) when combining dominant and nondominant arms. Conclusions: Static sonographic evaluation of the UCL at 70 degrees of elbow flexion should be integrated into UCL imaging protocols. Furthermore, when performing sonographically guided procedures targeting the UCL, clinicians should consider positioning the elbow at >30 degrees of flexion to optimize UCL conspicuity and CSA.