A Kangaroo Spine Lumbar Motion Segment Model: Biomechanical Analysis of a Novel <i>In Situ</i> Curing Nucleus Replacement Device

Abstract

This in vitro study compared the effects of nucleotomy alone, with nucleotomy then implantation with a novel nucleus replacement device (D3 device) in a single segment kangaroo spine model. This study utilised dynamic biaxial biomechanical testing of intact, nucleotomy and nucleus replacement implant conditions to evaluate the kinematic behaviour of the single segment kangaroo lumbar spine. Studies have examined the biomechanical efficacy of invasive treatments such as Total Disc Replacement and Intervertebral Fusion for the treatment of chronic low back pain, however no studies to date have investigated the biomechanical effects of a novel elastomeric compressive load sharing nucleus replacement device. Kangaroo lumbar spine motion segments with all musculature, ligamentous tissue and posterior elements removed, were tested in intact state prior to undergoing nucleotomy or nucleotomy then nucleus implantation using the D3 device. All specimens were tested in flexion-extension and lateral-bending; Range of motion (ROM), Neutral Zone (NZ), Hysteresis (H), and Elastic Stiffness (ES) were evaluated. Nucleotomised motion segments demonstrated a 30% to 90% increase in ROM, NZ, H, but not ES for all Flexion-Extension testing conditions and in Lateral Bending test conditions when compared to intact state. Implantation of the nucleus replacement device demonstrated no significant difference when compared to intact state except for H during Lateral Bending testing conditions when compared to the intact state. Therefore, there was a significant increase in ROM, NZ, and H after Nucleotomy during Flexion-Extension motions and an increase in ROM alone during lateral bending motions in the single segment kangaroo spine model. These changes return to that of the intact state with the placement of a novel nucleus replacement device. Our data suggest that the D3 device tested can restore the kinematic changes of a degenerated disc represented by the nucleotomised single motion segment.

Global and segmental kinematic changes following sequential resection of posterior osteoligamentous structures in the lumbar spine: An in vitro biomechanical investigation using pure moment testing protocols

“…47,48 But kangaroo lumbar spines have been used previously in in vitro biomechanical studies, and in one case for evaluating biomechanical efficacy of a nucleus replacement implant. 25,49 Just like any other mammalian spine, kangaroo spines have morphological adaptations to accommodate species-specific biomechanical demands. 50 Compared with human lumbar vertebrae, kangaroo's lumbar vertebrae have a smaller vertebral body diameter, greater vertebral body height, enlarged mammillary process, greater prominence of superior articular process above the superior endplate, smaller prominence of inferior articular process below the inferior endplate, comparable transverse distance between the inferior articular processes, and a comparable pedicle length.…”

Phase 1 evaluation of an elastomeric nucleus pulposus device as an option to augment disc at microdiscectomy: Experimental results from biomechanical and biocompatibility testing and first in human

“…The material is contained within a silicone jacket that conforms to the shape of the nucleotomised cavity when inflated and uses a proprietary system of sophisticated delivery instruments to fill the jacket with an inert in situ curing elastomeric filler material. Finite element analysis study and in vitro mechanical testing supported that KDD could restore the axial compressive mechanical properties of a disc after a discectomy and the kinematic changes of a degenerated disc represented by the nucleotomised single motion segment 15,16 . However, to our knowledge, there are no related studies assessing the silicone made in situ curing elastomeric nucleus augmentation device (Table 1).…”

“…Finite element analysis study and in vitro mechanical testing supported that KDD could restore the axial compressive mechanical properties of a disc after a discectomy and the kinematic changes of a degenerated disc represented by the nucleotomised single motion segment. 15 , 16 However, to our knowledge, there are no related studies assessing the silicone made in situ curing elastomeric nucleus augmentation device (Table 1 ). In this study, we evaluate the biomechanical and biocompatible properties of the novel nucleus augmentation implant (KDD).…”

Morphometry of the kangaroo spine and its comparison with human spinal data

“…However, not only the morphometry determines the value of a model but also tissue material properties of bones, intervertebral discs, and ligaments are just as important. Some of these data are represented indirectly by load-deformation characteristics, which can be determined with flexibility tests (Chamoli et al, 2014(Chamoli et al, , 2015Sabet et al, 2011).…”