Biomechanical Comparison of Three Lumbosacral Stabilizing Implant Devices in Canine Cadavers

Introduction: Degenerative lumbosacral stenosis (DLSS) is the most common cause of progressive lower back pain in large breed companion and working dogs. Pins/PMMA and SOP systems have been previously shown to provide stability of the canine L7-S1 junction. Polyaxial pedicle screws and rod fixation systems are commonly used in human spinal stabilization; however, canine-specific implants (cPSRC) have never been investigated in canine cadaver models.

Materials and Methods: Twenty-four dissected lumbosacral large canine breed spinal sections were randomly assigned to Pins/PMMA, SOP or cPSRC following routine dorsal laminectomy. The spines were stabilized using 3.2 mm shaft/4.0 mm thread diameter in the Pins/PMMA group, 3.5 mm screws for SOP locking plates and 5 mm rods and 4.5 mm diameter screws for the cPSRC system. Non-destructive cyclic three-point bending (axial, lateral, flexion/extension) applied pure moments of /−5.0 N-m to the constructs and load to failure in dorsiflexion on two samples each.

Results: Analysis showed equivalence between the groups for range-of-motion and compliance/stiffness. Clinically, cPSRC implants should provide similar initial stiffness to other recognized L7-S1 stabilizing devices. Implant placement accuracy was found to be 87.5% for SOP, 87.5% for Pins/PMMA and 75% for cPSRC.

Discussion/Conclusion: The novel cPSRC system should be used to fixate an unstable L7-S1 junction in canines. Although not superior, the cPSRC systems were equivalent in stiffness in torsion, bending and flexure load testing to predicate lumbosacral stabilization constructs.

Acknowledgement: This study was funded by the College Research Council, CVMBS-CSU. The implants were donated from Orthomed, IMEX Veterinary and ArteMedics. The authors have no conflict of interest.

No conflict of interest has been declared by the author(s).