Chulalongkorn Medical Journal


Background: Adjacent syndrome is a widely concerned adverse outcome after spinal fusion. Interspinous distraction device (IDD) has become an interesting device and seems to be the solution by theoretically controlling loads to adjacent levels. Objective: To analyze the effects of a modified U-shape IDD on the intervertebral disc (IVD) pressure atm instrumented and adjacent level of a lumbar spine model. Methods: Three cadaveric specimens using lumbar vertebrae level 1 - 5 (L1 - L5) spines were loaded in neutral, flexion and extension. Needle pressure sensor was applied to measure IVD pressure at anterior annulus, nucleus pulposus, and posterior annulus of the IVD at L2 - L3, L3 - L4, and L4 - L5. Cadaveric specimens were tested in 4 consecutive sequences including intact specimen, bilateral facetectomy at L3 - L4, insertion of the modified U-shape IDD at L3 - L4, and pedicle screw fixation at L3 - L4, respectively. Results: By using the modified U-shape IDD, the IVD pressures at L2 – L3 were decreased when compared to both destabilized specimen and specimen with pedicle screw fixation especially IVD pressure at nucleus pulposus in flexion position of cadaveric specimen (P = 0.021). However, the IVD pressures at L3 – L4 and L4 – L5 were randomly affected by this device. Conclusions: The modified U-shape IDD provides support for the upper adjacent IVD pressures but the effect for the instrumented and lower adjacent level are still unremarkable.



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