Osteochondroma in a horse!!

 The radiograph in Figure 1 corresponds to the carpus of the horse which became lame ONLY after heavy work. Once he was lame, the lameness was resolved by injecting carbocaine into carpal joints. Careful radiographic examination of the carpus and the surrounding structures noted a bony protuberance along the distal, palmar aspect of the radius (Figure 1 and 2). This finding is consistent with an osteochondroma formation. In humane medicine, an osteochondroma is defined as " an abnormal, solitary, benign growth of bone and cartilage, typically at the end of a long bone". In horses, osteochondroma formation is not common however when it does occur, the occurs commonly along the lower end (distal) aspect of the radius. In this location, the osteochondroma may cause irritation to the surrounding soft tissue structures including the carpal sheath. 

Figure 1

Figure 2

In Figure 3 and 4, an ultrasound exam was performed of the distal radius to determine if the osteochondroma was the source of the lameness. Two irregular lines (yellow lines) can be seen on the ultrasound exam which are consistent with the bony protuberances noted in the radiographs. In addition, the surrounding tissue is irregular with pockets of edema and there is a large accumulation of fluid within the carpal sheath (Red star). 

Figure 3

Figure 4

When the left and right forelimbs were compared via ultrasound (Figure 5), there is no evidence of an osteochondroma in the normal leg (right) compared to the left leg. A needle was placed into the pocket of fluid within the carpal sheath and blood tinged synovial fluid was collected. Following fluid aspiration, the carpal sheath was treated with cortisone, antibiotic, and Hylartin V. Most osteochondromas in horses are surgically removed and the prognosis is good for full return to work.