Horses with chronic inflammation of the digital flexor tendon (DDFT) sheath that doesn't respond to conventional therapy might be suffering from longitudinal tears in the DDFT. Warmbloods which suffer from chronic annular ligament constriction syndrome (ALCS) also could have hidden longitudinal tears. Unfortunately, it is not easy to diagnose longitudinal tears. Ultrasonography, which is commonly used to evaluate tendon injuries, can identify changes at the DDFT borders, but a closer examination within the tendon sheath is necessary to get an accurate diagnosis of longitudinal tears.

Researchers from the Equine Hospital De Bosdreef in Belgium, including Hans Wilderjans, DVM, Dipl. ECVS, evaluated the digital flexor tendon sheath of Warmbloods with chronic tenosynovitis and/or ALCS using tenoscopy, a relatively simple technique similar to arthroscopy for tendons and their surrounding sheaths. "We use arthroscopy equipment with other instruments specifically developed for the procedure," he says. The study was designed to determine how often longitudinal tears are the underlying cause of chronic tendon sheath inflammation in Warmbloods.

The records of 25 horses which received tenoscopy were reviewed. All had a chronic history of digital flexor tendon sheath distension. On ultrasound examination, 11 horses had changes on the lateral or medial borders of the DDFT, but nothing diagnostic of a specific problem. When tenoscopy was performed, however, a diagnosis of longitudinal tears was made in all 11 horses. An additional six were diagnosed during surgery. Seven did not have any longitudinal tears. Treatment consisted of removing the torn collagen fibrils (small fibers) and releasing the tension on the fetlock canal by cutting the palmar annular ligament.

The outcome of the tenoscopic procedure was mixed. Ten horses recovered fully and returned to work. Four returned to a decreased workload and needed periodic intrathecal (within the sheath) injections with hyaluronic acid and short-acting steroids to remain sound. Three horses remained lame. Importantly, none of the operated limbs returned to a normal cosmetic shape.

After this study was performed, Wilderjans and his colleagues altered the procedure somewhat by cutting the palmar annular ligament only when solid evidence of constriction was evident. "There were some cases where adhesions developed between the palmar annular ligament and the superficial digital flexor tendon," he explains. Still, despite the few complications, the researchers concluded that longitudinal tears occur with some frequency (17 of 25 horses examined). Therefore, horses with chronic tenosynovitis/ALCS which do not respond to conventional therapy should be considered for this tenoscopic procedure. Horses which don't respond to the tenoscopic procedure might respond to an open approach and suturing of the tear.

Wilderjans and researchers at the Equine Hospital De Bosdreef in Belgium are currently traveling to meetings around the world to present their research findings on methods of repairing lacerations of flexor tendons in horses. Soon their results, which include more than 100 cases, will be published. Wilderjans and his colleagues are also working on a procedure called buccotomy, a surgical approach for removing diseased teeth via the outer cheek surface.

If you would like to learn more about the work taking place at the Equine Hospital De Bosdreef, visit and, web sites for these two equine referral hospitals in Belgium.

Wilderjans, H.; Boussauw, B.; Madder, K.; et al. Equine Veterinary Journal, 35 (3), 270-275, 2003. 

About the Author

Susan Piscopo, DVM, PhD

Susan Piscopo, DVM, PhD, is a free-lance writer in the biomedical sciences. She practiced veterinary medicine in North Carolina before accepting a fellowship to pursue a PhD in physiology at North Carolina State University. She lives in northern New Jersey with her husband and two sons.

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