Dr. Susan Dyson, head of clinical orthopedics at the Animal Health Trust in Newmarket, UK, investigated the role that the Superficial Digital Flexor Tendon (SDFT) may play in hind limb lameness, more specifically, where the SDFT attaches to the hock. The SDFT has two broad bands at the portion of the tendon that runs over the back of the hock (tarsus), and a complete tear of one of those bands can cause sudden and severe lameness.
In her research, Dr. Dyson examined the hocks from 12 horses (humanely euthanized for reasons not related to this study), from which the SDFT attachments were measured for length and thickness, and the values recorded. She then examined six horses with no history of lameness and normal appearance to the hock with an ultrasound, looking at the SDFT attachment site for uniformity and thickness, and findings were recorded. Using this information that she had gathered, Dr. Dyson subsequently diagnosed three horses with full-thickness incomplete tears of the medial calcaneal band (the SDFT band located on the inside of the hock), recording the lameness of the horse, the thickness of the SDFT attachment, the stability or instability of the SDFT itself (as a result of the tear) and any enlargement of the calcaneal bursa (fluid-filled structure located over the point of the hock). Dr. Dyson was able to determine via ultrasound the presence of these tears in all three horses.
Based on this piece of research, Dr. Dyson said, “careful palpation of the plantar aspect of the tarsus (the back of the hock) and a comprehensive Ultrasonographic assessment is warranted in horses with lameness associated with swelling of the hock.”
Scientific Article: Dyson, Sue MA, Vet MB, Ph.D., “Incomplete tears of the medial calcaneal insertion of the superficial digital flexor tendon of a hind limb in three horses,” Journal of Equine Veterinary Science, abstract published on line July 16, 2014.
Companion article: Oke, Stacey, DVM, MSc, “Consider SDFT Attachment Problems in Lame Horses,” theHorse.com, Feb. 24, 2015, article #35378.