A biomechanical cadaveric study of a modified U-shaped interspinous distraction device.

STUDY DESIGN

An experimental study.

OBJECTIVE

To analyze the effects of a modified U-shape interspinous distraction device (IDD) on the stability of a destabilized lumbar spine model.

SUMMARY OF BACKGROUND DATA

The use of IDD for treatment of lumbar spine pathology remains a subject of debate. A modified design of an IDD consisted of a titanium (Ti) U-shape dynamic stabilizer and a Ti tensioning wire loop was biomechanically tested.

MATERIALS AND METHODS

Six sets of cadaveric lumbar vertebrae levels 1-5 (L1-L5) were subjected to loads in flexion, extension, and lateral bending in the 4 following sequences: intact specimen, unilateral facetectomy and discectomy at L3-L4, insertion of the modified U-shape IDD at L3-L4, and pedicle screw fixation at L3-L4. The range of motion (ROM) of L3-L4 following modified U-shape IDD insertion was compared with that of the intact specimen. The ROM of the adjacent vertebrae (L2-L3 and L4-L5) following modified U-shape IDD insertion was compared with that after pedicle screw fixation. Statistical analysis was performed using the Wilcoxon signed-rank test.

RESULTS

The modified U-shape IDD decreased the ROM of a destabilized L3-L4 in all testing load (P<0.05). The stability of L3-L4 following the modified U-shape IDD insertion was restored to that of the intact specimen (P>0.05). The ROM at adjacent vertebrae after the modified U-shape IDD placement was similar to the ROM obtained after pedicle screw fixation at L3-L4.

CONCLUSIONS

The modified version of a U-shape IDD is effective in stabilizing an unstable segment of the lumbar spine. The device does not create deleterious effects on the adjacent vertebrae.