Lingering Lameness

Q. I have a 10-year-old mare that tore her deep digital flexor tendon two years ago where it meets the coffin bone. After an MRI, we injected platelet-rich plasma (PRP). I put her on stall rest for three months with a wedged pad on the affected foot. We slowly lowered the wedge over time, and I hand-walked her when she graduated from complete stall rest. She is slightly better but not sound enough to run barrels at her former level. Would she be a candidate for adipose-derived regenerative stem cell treatment, or is the injury too old?

Jessica Holmes, South Dakota

A. First, it would be helpful to know if your veterinarian found any other abnormalities on your mare's MRI exam two years ago. In my experience I've learned it is important to treat all of the injuries, not just the most obvious one. If you only treat part of the problem, you can't expect the horse to be sound.

Does the horse currently block completely sound with diagnostic nerve blocks of the foot, or does she block only partially sound? Sometimes we find other ongoing problems farther up the limb that are also contributing to the lameness. It may be worthwhile to repeat the diagnostic nerve blocks and confirm that your horse is sound when the foot is blocked. If she is, then the only way to know if the deep digital flexor tendon tear is still a problem is to perform another MRI. If she does not block sound in the foot, then you need to look elsewhere for other problems.

If the deep digital flexor tendon is not healed two years after PRP treatment, then adipose-derived regenerative cells (ADRCs) can still provide significant healing potential. Rarely, though, do I see isolated deep digital flexor tendon tears without other injured foot structures. Again, if you only treat part of the problem, you can only expect partial improvement. These deep digital flexor tendon tears down inside the foot are some of the most difficult injuries to treat. When comparing the tendon-healing effects of PRP to ADRCs, there is no contest. The latter have far more "healing power" than PRP, and in my experience ADRCs heal injuries faster and with a lower reinjury rate than PRP. I rarely use PRP anymore because I have had much greater success with ADRCs than I ever did with PRP.

About the Author

Ross Rich, DVM, PA-C

Ross Rich, DVM, PA-C, is the owner of Cave Creek Equine Hospital in Phoenix, Ariz., where he specializes in equine lameness, orthopedic surgery, sports medicine, performance problems, diagnostic imaging, regenerative medicine, and respiratory problems. He’s used stem-cell therapy to treat orthopedic issues in horses since 2004.

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