What Is a Bone Scan, and Can It Help My Horse?

By Liz Devine, DVM, MS, DACVS-LA, Pilchuck Veterinary Hospital 

Nuclear scintigraphy, or bone scan, is one of several tools that can be used in the diagnosis of lameness in horses.

Other commonly used diagnostics, such as radiographs, ultrasound and MRI, examine abnormalities in the structure of the horse’s limb, and your veterinarian uses this information to infer the cause of pain. However, one thing that makes nuclear scintigraphy unique is that it looks at the function of the tissue instead of the structure. Because of this, bone scans have a few advantages over other diagnostics:

  • Bone scans can help to localize causes for subtle lameness. While you still get the most information from these scans if the lameness is localized to a particular area, bone scans are quite useful in cases where the lameness is very subtle or coming from multiple limbs, which can make localization challenging.  
  • Bone scans can help to diagnose intermittent lameness. Cases of intermittent lameness can be candidates for nuclear scintigraphy because lameness localization can be a challenge in these horses.  
  • Bone scans can target areas other diagnostics can’t. In horses where a fracture of the pelvis or back is suspected, nuclear scintigraphy can be very helpful because these are often difficult areas to radiograph.  
  • Bone scans can identify stress fractures. Stress fractures are another great use for this tool, as they often do not show up on radiographs initially and misdiagnosis can result in catastrophic injury.
  • Bone scans can be performed on patients that are not tolerant of traditional lameness exams. If a horse does not allow the veterinarian to safely perform a complete lameness exam, nuclear scintigraphy can be a way to help to localize the source of pain. 

How It Works: In order to perform a bone scan, an intravenous catheter is placed in the horse’s vein for safe injection of the medications. A radioisotope is injected into the bloodstream, which has an affinity for areas of high bone turnover. As this radioisotope decays, it emits gamma rays, which are picked up by a gamma camera to make an image. Areas of the body where there is high bone turnover or inflammation have concentrated amounts of radiopharmaceutical and show up as “hot spots” on the image. This will tell your veterinarian what locations have increased inflammation and where to focus further diagnostics or treatments.

Your Horse’s Vet Stay: Nuclear scintigraphy requires an overnight stay for your horse in order for the radioisotope to be safely eliminated from the body through the urine. This process takes anywhere from 24-48 hours for elimination. A technician will check to ensure that the horse is no longer emitting gamma rays before either allowing the horse to return home or continuing further diagnostics or treatments.

Talk to Your Veterinarian: If your horse has a lameness or performance-limiting issue, contact your veterinarian to see if nuclear scintigraphy is an option. The best results are obtained when horses are in active work or if the bone scan is performed a few weeks after injury. Therefore, it is important to work with your veterinarian to determine what will be best for your horse in order to get the most diagnostic scan possible.  

Pilchuck Veterinary Hospital offers equine ambulatory care, referral hospital services and 24/7 emergency. Call 360.568.3111 to schedule a consultation with one of our equine practitioners. Photo courtesy of Pam Poole, LVT.

Article added 8.8.15