Biomechanical preservation of lumbar spine stability and motion with an intraosseous implant following vertebral body osteotomy.

PURPOSE: When nonsurgical treatments for low back pain with radiculopathy fail to relieve symptoms from nerve root compression, lumbar spine fusion is the standard treatment. A potential new option is using a vertebral body osteotomy (VBO) with the Vertiwedge Intraosseous System™, a novel spinal implant designed to restore foraminal height, spinal alignment, and preserve motion. The purpose was to demonstrate that VBO with the Vertiwedge implant can stabilize and correct collapsed segments while maintaining the spine's native stability and motion under various loading conditions.

METHODS

The Vertiwedge was biomechanically assessed in a novel spine simulator via non-destructive articulations that included randomized compression loads (0-500 N) and planar motions in flexion/extension (20°/18°), lateral flexion (19°), and axial rotation (9°). Simulations were conducted on 8 cadaveric specimens (5 M:3 F, spinal segments L1-S1, ages 35-75 years). A cubic fit model compared equivalence and linear mixed model compared stiffness with covariates of condition, motion, and compression. Change in foraminal height was not addressed as cadaveric specimens were non-pathological.

RESULTS

After surgical implantation, the cubic fit model demonstrated an overall equivalence (60-80%) to the Native condition. The mixed model demonstrated no differences in maximum moments between any conditions (p ≥ 0.067) or condition*motion (p ≥ 0.196). The full interaction (condition*motion*compression) demonstrated no differences of biomechanical stiffness (p ≥ 0.991).

CONCLUSION

The Vertiwedge, after surgical implantation, demonstrated a return of biomechanical stiffness (stability) compared to the native state of the lumbar spine specimen with all three planes of motion across various physiologic compression loads. The Vertiwedge accomplished nearly native stiffness while preserving lumbar spine motion.