Metacarpal fractures associated with pancarpal arthrodesis in dogs

Objective-To report the prevalence of third metacarpal bone fractures after dorsal plating for pancarpal arthrodeses in dogs and to identify predispos ing factors. Study Design-Retrospective clinical study. Animals-Fifty-four client-owned dogs. Methods-Pancarpal arthrodesis was performed using dorsally applied 2.7- or 3.5-mm bone plates. Medical records and radiographs were retrospectively ev aluated to identify those dogs with metacarpal bone fractures after pancarp al arthrodesis and to determine the angle of arthrodesis, the percentage of the third metacarpal bone covered by the bone plate, and the percentage wi dth of the bone occupied by the screw. Radiological evidence of arthrodesis at follow-up examination 6 weeks postoperatively was recorded. Long-term r esults were obtained by telephone follow-up with the owners. All lame dogs were evaluated clinically and radiographically. Results-Metacarpal fractures occurred in 6 of 54 dogs. One of these dogs ha d a stress fracture of the third metacarpal 10 months after implant removal and was not included in the statistical analysis. Fractures occurred throu gh the distal screw hole in four dogs and involved two metacarpal bones (II I and IV) in two dogs. The median ratio of bone screw diameter-to-metacarpa l bone diameter was the same for dogs with metacarpal bone fractures and th ose with no fractures (44%), and the median angles of arthrodesis were 8 de grees and 7 degrees. These values were not statistically significant. The p ercentage length of the metacarpal bone covered by the plate was 53% (no fr acture) compared with 46% (fracture), and this difference was statistically significant (P = .035). Conclusions-Screw diameter was not implicated as a predisposing factor for metacarpal bone fracture in dogs undergoing pancarpal arthrodesis using a d orsally applied dynamic compression plate. The length of the metacarpal bon e covered by the bone plate did affect the frequency of metacarpal fracture , with fewer fractures occurring when greater than 53% of the bone length w as covered by the dynamic compression plate. Clinical Relevance-When performing pancarpal arthrodesis with a dorsally ap plied bone plate, it is recommended that at least 50% of the length of the third metacarpal bone should be covered by the plate. (C)Copyright 1999 by The American College of Veterinary Surgeons.