Femoral Osteosynthesis in Black Capuchin Monkey (Sapajus nigritus) using Locking Plate

Background: Locking bone plates for internal fixation are characterized by plates with a locknut by screwing in a threaded chamber. The increased stability associated with less vascular lesion contribute to the lower risk of complications and makes the locking bone plates especially interesting in fracture management of wild animals to be reintroduced into nature.The aim of this report is to describe the case of a black capuchin monkey with a femoral fracture, submitted to internal fixation using locking plate, with a satisfactory postoperative evolution, characterized by the bone consolidation and full recovery of the function of the member.Case: An exemplar of an adult male black capuchin monkey (Sapajus nigritus) with 4.2 kg of body weight was presented due to a comminuted, diaphyseal fracture of the left femur. The animal was then submitted to internal fixation of the femoral fracture using a 2.0 mm locking plate with 11 holes. For the internal fixation, the plate was contoured and positioned on the lateral surface of the bone. In addition, four locking screws were inserted through both cortices in the proximal bone segment, while other three locking screws were inserted in the distal bone segment. Two of the distal locking screws were inserted through both bone cortices, while one of them were inserted through only one bone cortical. The animal showedcomplete functional recovery of the left hind limb at 30 days postoperatively. Despite this, it was visualized at the radiographic examination a partial release of the plate from the distal bone segment. Due to this, the animal was submitted to another surgical intervention to replace the distal locking screws by bicortical locking screws. The animal showed hind limb weight support at the second day postoperatively. The complete functional recovery of the left hind limb, however, was verified at 26 days postoperatively. In this moment, it was performed a new radiographic examination, which allowed the visualization of bone consolidation, and the animal was reintroduced into its natural habitat.Discussion: The choice of the bone plate may play a fundamental role in the bone healing process. Among many bone plates configuration, locking plates are highlighted, as they offer greater angular stability to the fracture and result in less injuring periosteum and blood vessels. In addition, other methods for internal fixation are related to numerous postoperative complications. Despite the low rate of complications of the locking system, in the present case, it was visualized the partial release of the plate from the distal bone segment, which is probably related to the higher concentration of load near the sniffle joint, and the early release of one monocortical screw. The use of monocortical screws is permissible whenproperly locked in the threaded chambers of the plate. In the present case, however, it is believed that the early release of the distal monocortical screw is probably related to the incompletely screw head locked in the threaded chamber of the plate. Therefore, the use of bicortical screws should be preferred even using locking systems, especially in anatomical regions subjected to a higher concentration of load, as near the sniffle joint. In addition, it is concluded that the locking plate maybe a viable option for the treatment of long bone fractures in wild animals, in particular femoral fractures of specimens of black capuchin monkey (Sapajus nigritus).Keywords: wild animals, internal fixation, fracture.