Osteochondral Fragments and Cartilage Injury in Horses

Researchers recommended bone chip removal to preserve joint health and athletic function.
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Xray on lower leg
Bone chips are frequently found during radiographs, especially in the fetlock joint. | Anne M. Eberhardt/The Horse
Equine veterinarians commonly find osteochondral fragments, whether developmental (osteochondrosis) or traumatic in origin, on radiographs during both performance and prepurchase exams, often in horses’ fetlock joints. They frequently recommend surgical removal of these fragments—commonly referred to as bone chips—even when the horse shows no clinical signs of lameness to preserve joint health and the horse’s athletic ability. In a recent retrospective study researchers in Germany examined associations between horses’ osteochondral fragment size, location, age of the horse, and lameness and prevalence of cartilage injury and, as an extension, whether surgical removal in such cases is recommended.

The research team reviewed radiographs, clinical exam records, and surgical records for 640 horses that had fragments removed from 823 fetlock joints—where the cannon bone, proximal sesamoid bones, and first phalanx (long pastern bone) meet. They assessed osteochondral fragment location, number, and size on radiographs and reviewed clinical evaluation records for the presence of lameness, AAEP lameness score, and lameness duration.

Surgeons noted the location and severity of the articular cartilage injury during surgery. Of the 823 joints, 237 (28.8%) had cartilage injury. The majority—65.5%—of lame horses with osteochondral fragments in the (fetlock) joint also had cartilage lesions evident during arthroscopic surgery, said Jana Evelina Cornelia Goldkuhl, of Pferdeklinik Bargteheide, in Germany, a researcher on the study. This is an important clinical consideration when deciding on surgery because horses who have more bone chips on radiographs will likely have more cartilage damage.

Her team found no difference in lameness occurrence when comparing dorsal (relating to the front side of the joint) versus palmar/plantar (relating to the back side) fragments. Bone chip size didn’t affect lameness occurrence, either.

Further, clinically lame horses were more likely to have cartilage injury identified during surgery. Age appeared to make a significant difference in cartilage injury, which was more likely to affect Warmbloods older than 7 than younger age groups.

In the discussion portion of the study, the authors emphasized that cartilage is poor at healing on its own, leading to the common belief that fragment removal can be desirable to prevent cartilage damage. “I would recommend arthroscopic fragment removal in young sport horses with dorsal osteochondral fragments even when no clinical signs are present to avoid future lesions to the articular cartilage and lameness that might develop with age,” said Goldkuhl.

Horses load the dorsal aspect of the fetlock joint intermittently. When horses are moving slowly (walk and trot), it is non-weight-bearing, but at speed (canter and gallop) it experiences very high and sudden loading during hyperextension both under saddle and in the pasture. This doesn’t occur for the palmar/plantar aspect of the joint. Dorsal cartilage lesions are difficult to repair due to loading forces, which could explain why dorsal fragments tended to be associated with cartilage damage more than palmar/plantar fragments.

Because fragment size was not associated with cartilage injury or synovitis, GoldKuhl advised clinicians to remember osteochondral fragment size is not a decision-maker for fragment removal in the fetlock joint.

Palmar/plantar osteochondral fragments are often more stable than dorsal fragments because of the distal sesamoidean ligaments, she said—continuations of the suspensory ligament branches in this part of the leg—and only 14.7% of that group had cartilage injury in the study. However, other research results have suggested arthroscopically removing fragments prior to development of cartilage injury results in a better prognosis for return to previous athletic function. The presence of osteochondral fragments contributes to the development of osteoarthritis, especially with dorsal lesions. Therefore, said Goldkuhl, removing fragments prior to clinical signs or cartilage injury developing might be ideal.

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Written by:

Jennifer Selvig, DVM, is an associate equine veterinarian at Cleary Lake Veterinary Hospital and the owner and manager of Stargazer Farm, an eventing and dressage barn in Lakeville, Minnesota.

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