Type IV Monteggia Fracture in a Puma Cub (Puma concolor) - Surgical Treatment

Abstract

Background: Monteggia fracture is an injury characterized by a bone discontinuity affecting the ulna associated with radial head dislocation. This type of fracture has been rarely reported in human and veterinary literature and even more rarely in studies on wild animals. Herein, we report the case of a puma cub (Puma concolor); also known as cougar) with functional weakness of the right forelimb following an automobile trauma who was diagnosed with type IV Monteggia fracture. The cub underwent osteosynthesis of the radius and ulna, which was associated with reduction of humeroradial dislocation, to achieve functional recovery of the injured limb until its reintroduction into the wild. 

Case: A traumatized puma cub was treated for lameness and functional weakness of the right forelimb. The nature of the trauma is unknown, but probably secondary to vehicle collision.  Following intramuscular chemical sedation with ketamine and xylazine, a physical examination was conducted, revealing that the cub was a young male with permanent incisors and deciduous canines. Radiographic examination revealed fractures in both ulna and radius, along with right humeroradial dislocation, which is a characteristic feature of type IV Monteggia fracture. The cub underwent surgical osteosynthesis associated with correction of the dislocation. Osteosynthesis was performed using locking neutralization plates on both radius and ulna. In addition, a figure-of-8 antirotational suture was performed with steel wire over the head of the radius and condyle of the humerus to reduce the radial head dislocation. After surgery, the animal appeared comfortable, with weight bearing of the operated limb. Bone healing of the fractures was verified within 75 days. It was recommended that the implants should be removed before reintroducing the animal into the wild.

Discussion: Monteggia fractures are an uncommon type of fracture, with only a few reports published in veterinary literature. Despite the lack of information, especially in wild animals. This type of fracture has been reported to be caused by direct high-energy, for example, automobile trauma or falls. Monteggia fractures are difficult to be identified by physical examination, and radiographic examination with at least 2 orthogonal projections is defined as the "gold standard" of diagnosis. These fractures must be treated surgically as early as possible to avoid excessive surgical manipulation and complications. Complications include swelling of the limb, muscle contraction, and inflammation of the soft tissues. The surgical technique may vary depending on the surgeon's preference and patient's characteristics. Furthermore, when bone fragments can be anatomically reconstructed and maintained in position, rigid stabilization methods should be used, such as locking plates. In the feline analyzed in this report, osteosynthesis of the radius and ulna combined with the antirotational suture enabled bone healing and functional recovery of the limb. The osteosynthesis associated to the antirotational suture contributed to the maintenance of the joint congruence, which is extremely important for maintaining an acceptable joint function. Early surgical intervention and appropriate handling of the animal contributed to its successful recovery and reintroduction into the wild. The implants used in the osteosynthesis of the radius and ulna were removed before the animal was released, due to the non-biodegradability of the materials.

Keywords: felidae, wild animal medicine, radius and ulna, humeroradial subluxation, osteosynthesis.