Abstract
The superficial digital flexor tendon (SDFT) is the most frequently injured structure of the musculoskeletal system in sport horses and a common cause for early retirement. This project’s aim was to visualize and measure the strain of the sound, injured, and healing SDFTs in a pony during walk and trot. For this purpose, biplanar high-speed fluoroscopic kinematography (FluoKin), as a high precision X-ray movement analysis tool, was used for the first time in vivo with equine tendons. The strain in the metacarpal region of the sound SDFT was 2.86% during walk and 6.78% during trot. When injured, the strain increased to 3.38% during walk and decreased to 5.96% during trot. The baseline strain in the mid-metacarpal region was 3.13% during walk and 6.06% during trot and, when injured, decreased to 2.98% and increased to 7.61%, respectively. Following tendon injury, the mid-metacarpal region contributed less to the overall strain during walk but showed increased contribution during trot. Using this marker-based FluoKin technique, direct, high-precision, and long-term strain measurements in the same individual are possible. We conclude that FluoKin is a powerful tool for gaining deeper insight into equine tendon biomechanics.
Highlights
Accepted: 24 May 2021Injuries of the superficial digital flexor tendon (SDFT), especially in the metacarpal region, are a common musculoskeletal disorder in sport horses [1,2,3,4]
No pain or lameness was detected after marker implantation in the SDFTs or metacarpal bones
The implanted beads could clearly be identified with ultrasound imaging and Computed tomography tomography (CT) and in the fluoroscopic kinematography (FluoKin) videos (Figure 2)
Summary
Injuries of the superficial digital flexor tendon (SDFT), especially in the metacarpal region, are a common musculoskeletal disorder in sport horses [1,2,3,4]. Tendonitis of the SDFT represents the most common cause of lameness and early retirement in ponies used for sport, such as polo ponies [5]. Within a follow-up period of two years, 40% of those horses suffer re-injury [7]. Human Achilles tendonitis is a comparable pathophysiological condition to the disorders of equine SDFT, which is considered a good animal model because of similar physiology [8,9]. Due to being “spring-loaded”, the SDFT operates near its physiological limit under maximal load [10,11,12,13]. Strains of up to 16.6% have been measured in the SDFT [14]
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