A yearling foal showed slight lameness on the left forelimb. He had a firm swelling on the medial aspect at the level of the distal radius. The limb was otherwise normal in appearance without evidence of trauma. Cr-Ca and lateral radiographs were made. What is the cause of the lameness? Radiographic diagnosis - Distal radial physitisThe radiographic changes are centered on the distal radial physeal plate medially and caudally and are characterized by a widening of the growth plate with loss of bone density in the metaphysis (arrows). The epiphyseal side of the growth plate is normal. The lateral and cranial aspects of the growth plate are normal in appearance. Soft tissue swelling is minimal and appears to be extracapsular in location. The radiocarpal, intercarpal, and the carpometacarpal joint spaces are normal. Comparison of the cr-ca views of both limbs is helpful in reaching an etiology. The radiograph of the opposite limb is essentially normal. The distal radial growth plate normally closes at 24 to 30 months of age.The radiographic diagnosis in this patient is best limited to the term "physitis" or "epiphysitis" without a specific etiology since several etiologies can present in this way. Nutritional disease can present in this manner except it would be expected to be more generalized across the growth plate with an angular limb deformity and could be present bilaterally. In nutritional disease, the metaphysis often widens and overlaps the epiphysis in addition to causing an angular limb deformity. Infectious disease could be the result of a puncture wound and would be focal and would have a more prominent soft tissue component and a more acute onset of clinical signs. Infectious disease could also be the result of hematogenous disease that could be bilateral or polyostotic. The presence of periosteal new bone could be helpful in suggesting an infectious lesion due to either a puncture wound or hematogenous. In this patient, treatment was symtomatic for pain but also included antibiotics. Follow-up radiographs would have been helpful in evaluation of the disease process and its etiology. The owner agreed to this treatment, but failed to return for any follow-up. Joe P. MorganProfessor EmeritusDepartment of Surgical and Radiological SciencesSchool of Veterinary MedicineUniversity of CaliforniaDavis, CA 95616jpmorgan@ucdavis.edu
