Distal lateral third metacarpal fractures occur with a high prevalence in racehorses. This paper discusses a two year old Thoroughbred gelding that presented to the Cornell Large Animal Surgery Service for repair of a left, distal, displaced, lateral third metacarpal fracture. The fracture occurred during a race on the day of presentation and the diagnosis was made from track-side radiographs. The horse was referred to Cornell after a half limb fiberglass cast was placed and a dose of phenylbutazone was given. Presenting physical examination revealed the horse to be mildly tachycardic, and 3/5 lame on the left forelimb with superficial abrasions on the medial aspects of both hind limbs; no additional physical abnormalities were noted. The half-limb fiberglass cast was cracked at the region of the palmar pastern, but because stability was not reduced, it was decided to wait until morning to remove it. Radiographs were performed the next morning which included lateromedial, dorsopalmar, dorsolateral-mediopalmar oblique, dorsomedial-palmarolateral oblique, flexed, and Hornoff views. The radiographs confirmed a left, distal, displaced, lateral, third metacarpal fracture with comminution at the lateral diaphysis. Surgery was performed with peri-operative arthroscopy and fluoroscopy to assess the adequacy of the reduction and cortical screw alignment, respectively. The prognosis for return to racing was considered good.
The paper will discuss the advantage of a Hornoff radiographic projection, the differences between a modified-ASIF technique and a standard ASIF technique in cortical screw placement, and the risk factors associated with distal lateral third metacarpal fractures.