Use of full cortical allograft to repair a metatarsal fracture in a foal.

This study details the process of using a full cortical allograft, a type of bone graft, to repair an open and complex fracture of the metatarsal bones in a young horse. Following infection and unsuccessful healing efforts, the graft was put in place, providing stability for the horse to bear weight and enabling the formation of a functional bone structure, leading to a successful, long-term recovery.

Introduction

This paper presents the case of a 4-month-old Quarter Horse colt, which was brought in for the repair of an open, comminuted fracture. Comminuted fracture refers to a break or splinter of the bone into more than two fragments. For this foal, the break happened in the proximal portions of the diaphyses of the left second, third, and fourth metatarsal bones. The problem was made more complex due to the open nature of the fracture, which led to an infection.

Initial Treatment

• The initial repair procedure involved the use of internal fixation and cancellous bone graft. In an internal fixation, medical devices such as pins, plates, or screws are used to hold the bone fragments in place. This procedure stabilizes the bones, allowing them to heal correctly and faster.
• Alongside internal fixation, a cancellous bone graft was used. This type of graft involves using the patient’s own spongy bone to help repair the fracture. However, in this case, the third metatarsal bone became infected and did not heal as expected.

Use of Full Cortical Allograft

• After the infection was managed and the infected portions of the bone were removed, a full cortical allograft was used for the repair. This allograft, a graft from a donor of the same species, was 5 cm in size and full thickness, i.e., it included the whole cross-section of the cortical bone. The cortical bone is the hard outer layer of the bones.
• The allograft was placed in the defect left by the infected and removed bone. Through rigid internal fixation, stability was provided to the allograft and to the remaining fracture fragments. This allowed the horse to bear weight on the second and fourth metatarsal bones.

Outcome and Conclusions

• The allograft was eventually resorbed, i.e., the body dissolved it. Despite this, appositional bone growth occurred. This process allows the bone to grow in width, creating a massive, functional metatarsal bone that integrated the second, third, and fourth metatarsal bones.
• Thanks to this procedure, the horse was able to recover successfully and over the long term, even becoming a show horse. The study thus demonstrated the effectiveness of using a full cortical allograft for metatarsal bone repair in such complex conditions.