399 - Facet Screws and Interspinous Spacer Fixation Provide Stability Simila...

#399 Facet Screws and Interspinous Spacer Fixation Provide Stability Similar to Pedicle Screw-rod System

Basic Sciences-Research

Poster Presented by: V. Goel


M.K. Kodigudla (1)
A. Agarwal (1)
S. Harpreet (1)
D. Dhanvin (1)
V. Palepu (1)
V.K. Goel (1)
D. Kirschman (2)
L. Felon (2)

(1) The University of Toledo, Bioengineering, Toledo, OH, USA
(2) X-Spine Systems, Inc., Miamisburg, OH, USA


Introduction: Fusion using instrumenation is a gold standard procedure in treating low back pain (LBP) patients who do not respond to conservative treatment. Facet fusion in conjunction with an interspinous spacer is currently explored as an alternative to other instrumentation. The purpose of this study was to compare the stability of a lumbar functional spinal unit (FSU) using the Fixet facet screw and Axle interspinous spacer with a pedicle screw system.

Material and Methods: Six fresh-frozen ligamentous motion segments (3 L2-3 & 3 L4-5) were procured for this study. The cranial (L2/L4) and caudal (L3/L5) ends of each motion segment were potted using bondo, a two part epoxy resin. The caudal end was fixed to the testing apparatus and pure moments were applied in steps of 0, 1.5, 3, 4.5, 6, 8 and 0 Nm in extension, flexion, lateral bending and axial rotation at the cranial end. Motion was tracked during each loading condition using the Optotrak (Northern Digital, Waterloo, Canada) system. Following the biomechanical testing of intact specimens, bilateral Fixcet screws and Axle (BLFS+A) interspinous spacer (X-spine, Miamisburg, OH) of appropriate sizes were implanted (Figure 1A) and tested for motion analysis. Likewise, pedicle screw system (PSS) was also tested in another group of specimens and two groups were compared (Figure 1B). Statistical analysis was performed using unpaired t test to evaluate the significant differences between two instrumentations.

Figure.1 FSU implanted with

A) Bilateral Fixcet facet screw across facet joint and Axle interspinous device [BLFS+A], and

B) Pedicle screw system [PSS].

Results: BLFS+A provided comparable stabilization in flexion/extension, lateral bending and axial rotation to PSS, Figure 2. When compared to intact, stabilization was significant in all modes for BLFS+A (P < 0.05) and there is no significant difference between BLFS+A and PSS systems.

Figure.2 Mean (SD) motion data at 8 Nm.

Conclusion: Bilateral facet screws in combnation with interspinous device is effective in restricting the motion across a FSU and thus provides stabilization to promote fusion across the segment. This implantaion is much less invasive than the pedicle screw instrumentation, thus a viable alternative treatment option. Additional studies are planned to evaluate the facet screw and interspinous spacer based technology for multiple level fixation with and without interbody grafts/cages.

Figure 1

Figure 2