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

The research article discusses an innovative technique for cervical stabilization in horses. It reports on an experimental study performed on four quarterhorse crossbreeds, outlining the safety and efficacy of the procedure.

Methods

• The researchers conducted an in vivo experimental study on four adult quarterhorse crossbreed horses whose ages ranged between 2 – 4 years and weighed above 250 kg.
• Each horse underwent a procedure wherein one mid-cervical spinal unit (specifically between the third and fourth cervical vertebrae or C3-C4) was distracted using a porous metal interbody fusion device (IFD).
• This spinal unit was then stabilized using a unique polyaxial pedicle screw and rod construct.
• The researchers performed neurologic examinations on the horses both before and after the surgical procedure.
• Radiographs of the fusion site and adjoining vertebrae were also taken preoperatively and subsequently on a monthly basis.
• Eight months post-surgery, the horses were euthanized for further examination and evaluation of the spinal units. The evaluation was done for osseointegration and implant safety using advanced testing methods like micro-computed tomography (micro-CT), histology, and histomorphometry.

Results

• The procedure was accomplished without complications and ensured safety across all horses.
• Radiographic evaluations revealed no instances of implant failure, migration, or spinal unit instability in any of the horses.
• Through the micro-CT technology, researchers identified new bone formation around the screw and rod constructs. This confirmed successful osseointegration—the process where the implanted material and existing bone integrate and connect—of the implant.
• Furthermore, histology analysis showed no signs of inflammation or iatrogenic damage (illness caused by medical examination or treatment).
• All horses also showed evidence of new bone within the IFD, with varying osseointegration levels on the cranial and caudal surfaces (front and back) of the implant.

Conclusions

• The unique technique used in the experiment was applied safely and effectively to stabilize the C3-C4 spinal unit in the horses.
• There was variable osseointegration within an 8-month period.
• Given the positive outcomes, the researchers recommended a strategic evaluation of this technique in horses diagnosed with cervical vertebral compressive myelopathy—a condition that leads to compression of the spinal cord due to various deformities in the cervical vertebral column.