Applicability of ARFI elastography in detecting elasticity changes of the equine superficial digital flexor tendon with induced injury.
Authors: N. Bernardi, I. D. Da cruz, M. Maronezi, M. M. Santos, Katiucha Rebeca Jennifer Lopes Lera, B. Gasser, L. Aires, José Corrêa de Lacerda Neto, P. A. Canola, Ricardo Pozzobon, R. Uscategui, M. Feliciano
Journal: Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association
Summary
# Editorial Summary Researchers used acoustic radiation force impulse (ARFI) elastography to track stiffness changes in the superficial digital flexor tendon (SDFT) and adjacent structures following experimentally induced collagenase injury in eight horses, monitoring both injured left forelimbs and control right forelimbs over 90 days. B-mode ultrasound revealed typical hypoechoic lesions with disrupted fibre pattern, whilst ARFI imaging demonstrated a predictable stiffness trajectory: the injured SDFTs appeared notably softer (cool colours on elastograms) in the first three weeks post-injury, with stiffness values dropping significantly below controls (P < 0.001), before progressively stiffening from day 40 onwards as healing progressed. A cutoff velocity of less than 6.21 m/s during the first two timepoints identified tendinopathy with 75.8% sensitivity and 92% specificity, providing an objective quantitative threshold beyond conventional greyscale assessment. Changes in stiffness rippled through adjacent structures—the deep digital flexor tendon, accessory ligament, and suspensory ligament all showed altered elasticity at different stages of healing, indicating that injury-induced remodelling extends beyond the primary lesion site. For equine practitioners, ARFI elastography offers a non-invasive, quantifiable means to monitor tendon healing trajectory and detect subtle stiffness changes that may indicate progression or complications, potentially refining prognosis and rehabilitation timelines in clinical cases of flexor tendon injury.
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Practical Takeaways
- •ARFI elastography offers a quantifiable, objective measure of tendon healing that goes beyond conventional ultrasound, potentially improving monitoring of SDFT injuries in clinical practice
- •Stiffness changes follow a predictable pattern during healing (soft → hard over ~30 days), which can help identify healing trajectory deviations and guide rehabilitation timing
- •Adjacent structures undergo mechanical changes during primary tendon injury healing; comprehensive assessment should monitor neighboring tendons and ligaments, not just the primary injury site
Key Findings
- •Injured SDFTs showed decreased stiffness (soft/cool colors) from days 3-15 post-injury, then increased stiffness from day 30 onwards approaching control values
- •ARFI elastography cutoff value of <6.21 m/s achieved 75.8% sensitivity and 92.03% specificity for detecting SDFT tendinopathy at days 3-15
- •Tendon injury caused stiffness changes in adjacent structures (DDFT, AL-DDFT, SL) at different timepoints during 90-day healing period
- •ARFI elastography successfully monitored soft tissue repair progression and detected mechanical property changes invisible to conventional B-mode ultrasound