Clinical history A 14 year old French stallion presented acutely lame and was non-weight-bearing on the left hindlimb. The foot was swollen and difficult to examine. Radiographs were made of the affected foot using 4 views. Radiographic study of the foot Radiographic diagnosis Biaxial fractures of the plantar eminences (wings) of P2 with separation of the fragments. Both fractures are articular. At least one additional fracture fragment can be identified (arrows). Subluxation of the PIJ is present. The fractures lines are thought not to involve the DIJ. Fractures of this type are thought to result from external trauma or a combination of compression and torsion (twisting) forces that occur with sudden stops, starts, and short turns. Note the status of the metatarsophalangeal joint. Oblique radiographic view of the fetlock joint Radiographic diagnosis Chronic chip fractures originating from the proximal articular surface of the first phalanx. The fractures are chronic as indicated by the smooth margins. These fractures are described as osteochondral (chip) fractures of the proximal (first) phalanx and usually occur medial or lateral to the to the digital extensor tendon. The appearance and location of the fractures suggests excessive overextension of the joint with stress on the dorsal aspect of the proximal end of the proximal phalanx as it is pressed against the third metatarsal bone. While frequent in race horses, the history of this horse was not known. In some horses with a chronic chip fracture, only a small amount of swelling or lameness indicates the presence of the bony lesion. The lesion was not suspected in this stallion. Treatment was not attempted because of the age of the horse and the suspected injury to the fetlock joint.
