Drug Testing and Prepurchase Exams for Horses

A 10 year old, warm-blood mare presented to PHD veterinary services for a prepurchase exam. The standard exam, complete with limb flexion was performed and the mare was found to be completely sound and negative to limb flexion. The buyer requested baseline radiographs of both hocks and both front feet. In addition, it was strongly recommended that a drug screen of the mare's blood be performed for the detection of sedatives, anti-inflammatory medications and corticosteroids.
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Figure 1

Although the mare was sound and did not resent limb flexion, there was radiographic evidence of advanced osteoarthritis of the lower hock joints.  In Figures 1,2, and 4, the yellow arrows are pointing to radiographic changes consistent with arthritis along the front or dorsal aspect of the lower hock joints. There is new bone growth (osteophytes) and joint space narrowing. In addition, in Figure 3, the blue arrows are pointing to the area of sclerosis surrounding the lower hock joints which suggests chronicity of the arthritis and the apparent "fusion" of the distal hock joints. These radiographic changes are advanced and are surprising considering that the mare was sound for the prepurchase exam.

Figure 2

Figure 3

Even though the mare was sound, I did NOT pass this horse for sale and intended use based on radiographic findings and advised the buyer to at least wait for the drug screen results prior to making their decision!   The standard drug screen takes approximately 5-7 days for results to be reported. Interestingly, the mare's blood tested positive for high doses of an anti-inflammatory medication which likely explains why this horse was sound and negative to limb flexion even though she has advanced arthritis in the lower hock joints. This case represents yet another example of the importance of drug testing and base line radiographs for prepurchase exams!! Admittedly, it is a financial slippery slope once you begin the radiographic exam regarding how many areas to evaluate, however; areas of high probablity such as the hocks and front feet should always be considered!

Figure 4