Peter Bousum, V.M.D.

Nuclear scintigraphy (Bone Scanning) is currently the most sensitive and comprehensive method of diagnosing lameness in the horse.  The process involves the intravenous injection of a radiopharmaceutical that selectively attaches to actiely metabolizing (injured or stressed) bone and the subsequent detection and imaging of these affected areas.  Obvious areas of accumulated radiation on an image are referred to as uptake.

Why is a bone scan more sensitive than other imaging modalities such as digital radiography, ultrasound, magnetic resonance and computed tomography?

Bone scanning detects active injuries as early as a few hours following even a subtle injury becuase it reies on active bone repair and not anatomic changes.  It may demonstrate these injuries or degenerative processes for months following the initial insult--often when they are not evident on other modalities such as radiographs, ultrasound or MRI.

What types of injuries are detected?

Occult or incomplete fractures, tears of trhe attachments of ligaments and muscles (enthesis), and subchondral stress (joint disease, arthritis) are readily evident on a bone scan and are rarely noted on radiographs in the early stages of lameness.

Can scintigraphy be useful for diagnosing intermittent sublte lameness?

Yes, bone scans are most helpful with these types of lameness.  Classical catastrophic fractures commonly seen in athletic horses (more commonly in racing) are most often preceded by undetected subtle or intermittent lameness that may typically improve dramatically between episodes.  These can often be noted on a bone scan well before the obvious and severly debilitating injury becomes evident.

How can scintigraphy help to manage injuries?

Bone scans can often help predict the healing time and suggest proper clinical management by grading the intensity of uptake in the initial scan and can be compared with subsequent scans during recovery.

Can bone scans be useful for injuries above the lower limb?

Yes, scintigraphy can be useful for the entire skeleton of the horse (including the head, spine and pelvis).  These areas can be scanned in a relatively short time period (several hours).  Bony injuires to these structures are difficult if not often impossible to detect by other methods.

Does the horse have to undergo general anesthesia for the procedure?

No, the horse is examined for one to two hours in the standing position and is given only light sedation.

How long is the horse's stay at the hospital?

The typical horse is admitted to the hospital the morning of the scan and then discharged at least 24 hours following detection.  These horses often require several hours on the day following scintigraphy for review and clinical examination.  Once the areas of intense uptake are noted, they may require radiographs for further assessment.