Suspensory ligament injury is a common problem in athletic horses, and it is often slow to heal, with a high recurrence rate when a horse returns to work. Douglas Herthel, DVM, of Alamo Pintado Equine Clinic in Los Olivos, Calif., has been using bone marrow in a new technique for treating these injuries. He began his study in 1995, looking at bone marrow, which contains stem cells, monocytes, platelets, and fat.

"A recent unpublished survey that was done at UC Davis indicates this is the single most common cause of lameness in the show horse," says Herthel of suspensory ligament injury. "It can affect almost any horse that is in athletic performance.

"The experience we had in treating these during the past 25 years–prior to stem cell therapy–was fairly dismal," he continues. "Ours is a referral practice, and we usually got the cases after they'd been looked at and treated numerous times. We were averaging only 20% success in return to full work."

Most of the horses used in his early studies were in dressage and jumping. "Our basis for using bone marrow in treating damaged ligaments was that it is a tremendous source of tissue healing components–growth factors, stem cells, and matrix," he says. The angiogenesis effect (formation of new blood vessels) is important for healing, along with increase of cellularity, fibroblast (connective tissue cell) numbers, and biomechanical strength. These traits had already been shown with stem cell therapy in rabbit collateral ligament studies