Extensor Process Fracture in a Horse

A teen-age gelding presnted for the complaint of forelimb lameness. The gelding had been purchased approximately 6 months prior and the prepurchase exam performed did NOT include a radiographic exam. The gelding was mildly lame in a straight line however the lameness was significantly worse when lunged in a small circle. Through a series of nerve blocks it was determined that the lameness was originating from the foot and a radiographic study was performed. The radiographic images in Figure 1-3 are lateral views of the foot in question. Two abnormalities are noted by the yellow and blue arrows in Figure 2. The blue arrow corresponds to a chip fracture of the extensor process of the coffin bone and the yellow lines correspond to extensive mineralization of the cartilage of the foot (side bone).

Figure 1

Figure 2

 In Figure 3, the extensor process chip fracture is magnified. It is likely that this chip fracture was present at the time of purchase and would have been discovered had the client opted for a radiographic exam of the forelimb feet.  In my opinion, this radiographic finding would have been reason enough the FAIL the horse at the time of prepurchase exam.  In addition to the extensor chip fracture, moderate "side bone" development is evident in the lateral view and the dorsal-palmar view (Figure 4). Typically, side-bone does not present a clinical problem however does consist of an abnormal finding and in this horse the side bone is more pronounced along the inside versus the outside of the foot. The asymmetry of the side-bone may be more clinically relevant that bilateral side-bone that is symmetrical.

Figure 3

Figure 4

The horse was treated with intra-articular corticosteroid and is approximately 75% improved with respect to lameness. The long term prognosis for this horse is guarded due to fracture of the extensor process of the coffin bone. This case represents yet another example of the need for at least foot radiographs at the time of prepurchase exam.