It started with a simple wound—a gash on the leg foreleg during an African safari trail ride. With time, bandages, antibiotics, and phenylbutazone, the then 9-year-old gelding’s wound healed well and caused no signs of lameness. So why did Mashatu become markedly lame a week later? And why, five weeks after the injury, did he end up non-weight-bearing lame on the affected limb?

According to his treating veterinarians at the Onderstpoort Veterinary Academic Hospital in the Republic of South Africa, intraosseous pressure—pressure inside the bone itself; specifically, inside the radius’ medullary cavity—was to blame for Mashatu’s pain.

The solution? According to the authors of a recently published study, a 3.2-mm drill bit.

In Mashatu’s case, veterinarians couldn’t find any visible injuries on the affected leg, and X rays only revealed some irregular new bone formation from the wound healing process. But on a nuclear scintigraphy exam, or a bone scan, veterinarians found significant radiopharmaceutical build-up, or a "hot spot," inside the left radius bone behind the five-week-old scar, said Mashatu’s treating veterinarian, Luis M. Rubio-Martinez, DVM, DVSc, PhD, Dipl. ACVS, ECVS. Rubio-Martinez was an associate professor in equine surgery at the University of Pretoria at that time and treating veterinarian for Mashatu at Onderstpoort