Autores: Paulo Vinícius Tertuliano Marinho, , Rodrigo de Souza Mendes, Juliana Molina Martins, Renato Otaviano do Rego, Erica Emerenciano Albuquerque, & Carolina Camargo Zani
Background: Cervical fractures in dogs occur most commonly in the cranial region, mostly requiring surgery. Various types of implants are being used while fixation using plate is poorly described in the literature. The plate and screw types are a limiting factor since they can lead to loss of stability due to loosening of the screws. The use of locking plates has been advocated, which does not allow movement between the screw-plate-bone, providing extreme stability and rigidity to the system. This study describes the use of locking bone plate to stabilize axis fracture in a dog and the results obtained with this technique.
Case: A 9-month-old male Poodle presented due to a history of trauma to the cervical spine caused by a fall of an object. Upon physical examination, the patient was alert and physiological parameters within the normal reference limits. However, neurological examination showed tetraplegia, hyperreflexia, preserved nociception and much cervical pain. There were no changes in the cranial nerves test. Cranial cervical lesion was initially suspected and the patient was rigidly fixed on a flat surface. The radiographic examination showed a fracture of the second cervical vertebra (axis) with anatomical axis deviation, and the patient was referred for surgery. After anesthesia, the dog was positioned dorsal decubitus and rigidly fixed on the operating table with the thoracic limbs pulled caudally. The surgical approach of the cranial cervical spine started through the ventral access until complete visualization of the fracture line and the caudal portion of the axis body. After perfect apposition and alignment of the bone fragments, rigid stabilization was performed using locking plate and screws. The patient had a favorable neurological recovery, and five days after the surgery, no change was observed in locomotion and postural reactions, besides the absence of neck pain.
Discussion: The implant used in this study was small and displayed a good fi t along the body axis. The locked system allowed the bolt head to lock in the hole of the plate, forming a bone-screw-plate unit that prevents its failure. In our case, the tip of the caudal screws protruded approximately two millimeters within the spinal canal, without any apparent effect on the outcome. In a previous study, in which plates were used for ventral fixation and stabilization of the atlantoaxial joint, the screws also protruded into the vertebral canal without causing any problems, presumably because the cervical vertebral canal is wider than the diameter of the spinal cord at this location. Failure rate of up to 44% has been reported for all the processes of atlantoaxial ventral fixation if the surgery is deemed successful when resolution of neurological signs occurs, and there is no need for further surgery. According to this, the present case can be considered successful
taking into account the clinical outcome after surgery, the rapid reduction of pain, return to ambulation and the absence of neurological deficits. We conclude that the locking plate was a viable alternative to other fixation techniques for fractures involving the second cervical vertebra in small animals since it allowed relative stability of the fracture and an excellent neurological recovery of the patient.