Shear wave elastography ultrasound does not quantify mechanical properties of the ulnar collateral ligament of the elbow.

Abstract

Objective: To validate shear wave elastography (SWE) stiffness measurements for the ulnar collateral ligament (UCL) of the elbow compared to mechanical measurements.

Materials and methods: Eleven fresh frozen human cadaveric upper extremities were evaluated by a musculoskeletal-specialized radiologist to provide SWE measurements used to calculate stiffness at 4 points along the anterior band of the UCL at various load states and flexion angles. Specimens were then dissected and optical markers were placed on the UCL to track displacement during applied force by a load frame, thereby providing measurements to calculate the mechanical stiffness. These two stiffness values were compared by ANOVA for all load states and flexion angles.

Results: Measurements of stiffness by SWE for the UCL were three orders of magnitude smaller than the true mechanical testing stiffness and no correlations between SWE and mechanical measurements of stiffness were found at 30, 60 or 90 degrees of elbow flexion (R² = 0.004, p = 0.85; R² = 0.001, p = 0.92; R² = 0.15, p = 0.24 respectively). SWE stiffness was greatest near the insertion of the ligament and lowest in the mid-substance of the ligament (p = 0.0002).

Conclusions: SWE stiffness did not correlate with mechanical measurements. Clinical utility of musculoskeletal SWE may be better defined when biomechanical properties or clinical outcomes can be correlated with SWE measurements. The ultimate clinical utility of SWE in musculoskeletal tissues may be qualitative, as demonstrated by differences throughout the length of the UCL in this study.