Clinical history of a lame foal A foal was presented to the clinic at 2 weeks of age with a history of lameness since birth. Rather firm swelling was present around the coronary band. Radiographs were made of the left front foot. Radiographic changes Marked destruction with modeling of the distal portion of the second phalanx. Associated injury to the distal interphalangeal joint (DIJ) but the third phalanx is rather well preserved as seen on the lateral view. However, the DIJ on the dorsopalmar view is difficult to identify and is probably with severe injury. The navicular bone is smaller is size than expected, is malformed as seen on the lateral view, and does not have a normal cortical bone. No active periosteal response is present on any of the bones. The hoof is malformed and has a typical “club foot” shape suggesting that the foal hasn’t been bearing weight on that foot. Bone density in the foot is probably less that expected. This could be evaluated by a comparison view of the opposite foot. The proximal interphalangeal joint is probably normal but that also could be judged more accurately by a comparison view. Differential radiographic diagnosis Most likely this is a hematogenous osteomyelitis/infectious arthritis present since/or before birth with rather remarkable modeling that has restored P2 in part. The foot shape suggests disuse with little motion present at the DIJ. The repair is remarkable without signs of focal bone destruction and no signs of active periosteal new bone. Osteochondrosis is a possible cause of absent bone tissue and was strongly considered in this foal because of the absence of radiographic changes expected in an active infection. A third possibility is a healing fracture with healing but with no signs of a healing callus at the time of radiography. The clinical history was helpful in reaching a diagnosis. Diagnosis Further clinical history indicated swelling of the left elbow and the left stifle. On ultrasound examination, the umbilical veins and arteries were enlarged. The left elbow and the DIP joint on the left front were operated. In addition, the umbilicus was explored. The definitive diagnosis was septic arthritis/osteomyelitis with the infection gaining entrance through the umbilical cord. Comments The case is remarkable because of the level of bony repair by the time of the radiographic study. It is difficult to imagine the extent of destruction in distal P2 and the DIJ at the time of birth that would have made a diagnosis of osteomyelitis/infectious arthritis rather easy. The age of the lesion and the degree of bone repair makes the diagnosis more difficult without the clinical history. The case demonstrates the speed of bony repair in the immature skeleton as compared with the mature skeleton. It is interesting to speculate concerning the repair of the DIJ and the prognosis of what originally must have appeared as a highly destructive lesion.
