Shear Wave Elastography of Normal Flexor Tendons of the Fingers and Its Clinical Application for the Diagnosis of Reruptured Tendons After Primary Repair

PURPOSE: Shear wave elastography quantifies tissue stiffness. This study aimed to assess the stiffness of the flexor tendons of the fingers under physiological conditions in healthy individuals and compare the results with cases of tendon rupture. METHODS: Twenty-two healthy volunteers were enrolled in this study. Shear wave speed (SWS) measurements of the flexor tendons were obtained in three positions (rest, extension, and flexion) by two independent observers. The effects of laterality, fingers, time (repeating the measurements at 0, 2.5, and 5 min after initial positioning in extension), age, and sex were analyzed. Additionally, eight patients with tendon rupture after primary repair were assessed, and their SWS values were compared with those of healthy volunteers. RESULTS: We observed statistically significant differences in SWS values between rest and extension, as well as between rest and flexion. Tendon size also showed a statistically significant effect. Excellent inter-rater reliability was found between the two observers' measurements. Notably, the difference in SWS between a ruptured tendon and the contralateral healthy tendon of the same digit was considerably greater than the difference between any two healthy fingers. CONCLUSIONS: This study establishes a reference standard for SWS values in healthy flexor tendons and demonstrates the potential of shear wave elastography as a diagnostic tool for detecting tendon rupture in vivo. A standardized protocol is required for its reliability and reproducibility. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic IV.