Cervical stabilization with polyaxial pedicle screw and rod construct in horses: A proof of concept study

To evaluate safety and efficacy of a novel technique for cervical stabilization.

In vivo experimental.

Four normal adult quarterhorse crossbreed horses (2-4 years of age, > 250 kg).

One mid-cervical spinal unit (C3-C4) was distracted with a porous metal interbody fusion device (IFD) and stabilized with a polyaxial pedicle screw and rod construct. Neurologic examinations were performed preoperatively and postoperatively. Radiographs of the fusion site and adjoining vertebrae were obtained preoperatively and monthly. Horses were euthanized at 8 months and spinal units were evaluated for osseointegration and implant safety via micro-computed tomography (CT), histology, and histomorphometry.

The procedure was performed safely in all horses, without severe postoperative complications. Evaluation of radiographs revealed no implant failure, implant migration, or spinal unit instability in any of the horses. The presence of new bone formation around the screw and rod constructs was confirmed via micro-CT. No evidence of inflammation or iatrogenic damage was noted from histology. New bone was present within the IFD in all horses, with variable osseointegration on the cranial and caudal surfaces of the implant in 3 horses.

The novel technique reported in the present study was safely applied to stabilize the C3-C4 spinal unit in the horses tested here and led to variable osseointegration within 8 months.

The results of this study justify evaluation of this technique in horses with a diagnosis of cervical vertebral compressive myelopathy.