Equine Musculoskeletal Ultrasonography 

Dr. Virginia Reef is the Director of Large Animal Cardiology and Diagnostic Ultrasonography and Chief of Sports Medicine and Imaging at the University of Pennsylvania's New Bolton Center. She is a world renowned expert in ultrasonographic imaging.

Dr. Reef’s lecture focused on the diagnosis and treatment of the "bowed tendon". A "bowed tendon" is a common injury of racehorses and nearly always occurs in the front legs involving the superficial digital flexor tendon. A bowed tendon can be a career-ending injury for a racehorse. The clinical signs of a bowed tendon are swelling, lameness, heat and pain on palpation. These clinical signs are not consistent. In fact, only 50 percent of horses with tendon damage exhibit lameness. In addition, inflammation of the tissues surrounding the tendon may look very similar to a bowed tendon. The use of diagnostic ultrasonography has revolutionized the diagnosis of tendon injury and allows for the differentiation of tendon damage from uncomplicated soft tissue swelling surrounding the tendon. Dr. Reef and Dr. Ronald Genovese, a specialist in equine distal limb ultrasound, have developed objective methods of quantifying tendon injury using ultrasonography. These objective measurements are then used to monitor tendon healing and permit the tailoring of rehabilitation to the individual horse.

Traditional treatments of "bowed" tendons consist of puncturing the tendon multiple times with a needle or other sharp instrument (tendon splitting), cutting the fetlock annular ligament which restricts the movement of the flexor tendon and cutting the superior check ligament, which anchors the superficial flexor tendon to the radius in the forearm of the horse. None of these treatments, including just resting the horse, have been proven to be effective and recurrence of the same injury is common. In 1998, Boehringer Ingelheim, gained FDA approval for BAPTEN (beta-aminoproprionitrile fumarate), a substance which blocks lysyl oxidase, the enzyme responsible for collagen cross-linking. Injection of BAPTEN into the lesion in the tendon is administered approximately one to three months after the initial tendon injury. This treatment is coupled with a controlled exercise program. At four months post-treatment it became apparent that there was a better sonographic quality of tendon repair (i.e., more parallel fiber alignment) in the BAPTEN treated horses as compared to the placebo treated. Generally, 6 months of low intensity exercise following treatment is necessary to ensure that adequate time has passed for collagen cross-linking to occur and for the tendon to regain its strength.

Credits: US Food and Drug Administration