Stiffness Comparisons of SOP Interlocking Plate Configurations in 3D Printed Canine Lumbosacral Vertebrae

There are no published biomechanical studies evaluating the effect of stabilization techniques on the stability of the 3D printed models of the canine lumbosacral junction. The purpose of the study was to quantify stiffness of String of Pearls (SOP) interl ocking plating system on the lumbosacral junction in dogs. Testing was performed on five canine lumbosacral junction 3D printed models. Four - point bending was applied and displacement along the ventral aspect of the lumbosacral junction measured. Stiffness of six stabilization techniques was tested:  Models with contiguous polymer reconstruction articular facets.  Models with two dorsal SOP plate each with two pedicle screws in L7, two sacral screws and contiguous polymer reconstruction articular facets.  Models with two SOP plates with two L7 pedicle screws, two sacral screws and disarticulated L7 - S1 articular facets.  Models with two SOP plates with only the caudal L7 pedicle screw and two sacral screws and disarticulated L7 - S1 articular facets.  Models wit h two SOP plates with only the cranial L7 pedicle screw, two sacral screws and disarticulated L7 - S1 articular facets.  Models with one SOP plate, with two pedicle screws in L7 and two sacral screws and disarticulated L7 - S1 articular facets. The greatest st iffness was obtained in models with contiguous polymer reconstruction articular facets stabilized by two SOP plates with two screws engaging the pedicle of L7 (90.13 ±11.16 N/mm). There was no difference in gap stiffness between models with two SOP plates and disarticulated articular facets (54.43 ± 6.25 N/mm), and models with two SOP plates and only a cranial L7 pedicle screw (42.01 ± 8.64 N/mm). The lowest stiffnesses was recorded in constructs with two SOP plates and a caudal L7 pedicle screw (26.38 ± 4. 56 N/mm) and one SOP plate (26.94 ±5.83 N/mm) and intact models, contiguous polymer reconstruction articular facets, with no stabilization technique applied to the lumbosacral junction (16.16 ± .89 N/mm). The study - demonstrated stiffness using a single cra nial pedicle screw in the pedicle of L7 was no different from models with two pedicle screws in L7. Contiguous polymer reconstruction articular facets had a constructive effect on overall stiffness of the lumbosacral junction.