2D-shear wave elastographic features of normal and injured equine superficial digital flexor tendons.

Background: Superficial digital flexor tendon (SDFT) injuries cause progressive loss of its mechanical properties. Two-dimensional shear wave elastography (2D-SWE) provides information about tissue stiffness.

Objective: To determine the feasibility, repeatability, and reproducibility of 2D-SWE of healthy and pathological forelimb SDFT.

Study design: Prospective observational cohort study.

Methods: Horses were divided into a noninjured Group (H) and a Group with tendinopathy of the SDFT (P). 2D-SWE of both fore SDFTs was performed at three metacarpal levels (A, B, and C, from proximal to distal). Qualitative and quantitative assessments were performed by two operators, and interobserver agreement was calculated. Differences between Group H and P, and between the affected and unaffected limbs of Group P and with Group H were analysed. Statistical analysis was performed with SPSS IBM. Statistical significance was set for p < 0.05.

Results: Thirty horses were enrolled (13 in Group H, 17 in Group P). Interobserver agreement was excellent to good. Qualitatively, in Group H, SDFT was from light to marked blue; in Group P, it appeared marked blue. Quantitatively, Group H had lower median mean shear wave velocity (SWV, m/s) and Young's modulus (kPa) at levels B and C (SWV: 8.19 and 8.27 m/s vs. 8.47 and 8.48 m/s; Young's modulus: 299.21 and 204 kPa vs. 216.03 and 214.44 kPa). In longitudinal scans, the unaffected limbs of Group P were different from the affected limb and from Group H at level B and in the transverse scan. The affected limbs of Group P were different from Group H in the transverse scan at levels B and C.

Main limitations: Low sample size, examination of naturally occurring lesions, observational nature.

Conclusions: 2D-SWE is feasible as a supplementary diagnostic method for detecting SDFT tendinopathies. Clinically healthy SDFTs exhibit lower SWV and Young's modulus values, suggesting less stiffness.