Bending strength and stiffness of canine cadaver spines after fixation of a lumbar spinal fracture-luxation using a novel unilateral stabilization technique compared to traditional dorsal stabilization

Abstract

Objective: To 1) assess the bending strength and stiffness of canine cadaver spines after fixation of a lumbar spinal fracture-luxation using a novel unilateral stabilization technique with pins and polymethyl methacrylate (PMMA) and 2) compare the results to a reference standard dorsal pin and PMMA technique.

Study design: A randomized non-inferiority trial.

Sample population: Cadaveric lumbar spines (L1-L6) from 20 Greyhounds.

Methods: Specimens were paired to match bodyweight and vertebral size. A standardized fracture/luxation was performed between L3 and L4. One spine within each pair was randomly assigned the unilateral fixation technique and the other received the reference standard dorsal fixation technique. Four-point bending of each specimen in flexion was performed by applying load to pins placed transversely into vertebrae L1, L2, L5, and L6. During testing, angular bending strength and stiffness were measured as a function of flexion angle. Margins for non-inferiority were defined a priori. Strength and stiffness of the specimens for each technique were compared statistically.

Results: Lower limits of 95% confidence intervals were above the defined margins for non-inferiority. Thus, based on these margins, for strength and stiffness, unilateral fixation was not inferior to dorsal fixation.

Conclusions: This novel unilateral approach to lumbar spinal fixation yielded comparable strength and stiffness when tested for bending in flexion to that of reference standard dorsal approach. This approach is therefore a suitable alternative to the dorsal approach in appropriate lumbar spinal fracture configurations.