Researchers Examine Annular Ligament Injuries

In a retrospective study, researchers from the United Kingdom found that injuries to the palmar or plantar annular ligament (PAL)--the anatomic structure that holds that superficial and deep digital flexor tendons in place as they pass the fetlock (ankle) joint--can be readily diagnosed, are common, and have a worse prognosis if observed concurrently with injury to the deep digital flexor tendon.

tendons and ligaments

According to Sue Dyson, MA, VetMB, PhD, DEO, FRCVS, Head of Clinical Orthopaedics at the Animal Health Trust in Newmarket, England, and a co-author on this study, "While PAL syndrome is well recognized, there is limited information regarding horses affected with a primary injury to the annular ligament itself."

In this study, medical records from 71 horses with a history of lameness, clinical signs of PAL injury, and the ultrasonographic diagnosis of a thickened PAL (> 2 mm) were collected from three hospitals.

Results showed that most (63%) of the affected horses were used for general riding purposes and only 23% were performance horses. PAL injury occurred more commonly in the hind limb compared to the forelimb, and bilateral PAL thickening was very common (found in 68% of horses), especially in hindlimbs.

"Thirty of the 71 horses (42%) had a positive outcome following either surgical or conservative treatment," Dyson summarized.

The researchers did find, however, that horses with PAL injury/thickening in addition to injury to the deep digital flexor tendon and formation of scar tissue in the area, or with a bilateral PAL, have a worse prognosis than horses with a PAL injury alone.

To better determine the treatment of choice and a more accurate prognosis in horses with PAL injury, further research is necessary.

The study, "Retrospective study of palmar/plantar annular ligament injury in 71 horses: 2001-2006" will be published in an upcoming edition of the Equine Veterinary Journal. Contributing authors were Dyson; K. Rosie Owen, BVSc; Tim Parkin, PhD; Mads Kristoffersen, DVM; Ellen Singer, DVM; and Tim Mair, BVSc.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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