[Effect of Coflex interspinous stabilization and vertebral arch pedicle screw implantation on the stability of three-dimensional motions of the lumbar spine].

OBJECTIVE

To evaluate the effect of Coflex interspinous stabilization and vertebral arch pedicle screw implant on the stability and motion of the lumbar spine.

METHODS

The range of motion (ROM) of 6 fresh adult human cadaver lumbar spine specimens (L(1) approximately S(1)) was biomechanically tested in forward flexion/extension stretch, left/right lateral bending and left/right axial rotation. The ROM and neutral zone (NZ) of the segments L(2/3), L(3/4), and L(4/5) were measured and compared in 3 conditions, namely intact condition (a), rigid fixation of the segment L(4/5) with vertebral arch pedicle screw (b), and condition b plus L(3/4) stabilization with Coflex device (c).

RESULTS

The ROM of segment L(4/5) was significantly smaller in conditions b and c than in condition a in all the directions (P<0.05). The ROM of segment L(3/4) was significantly smaller in conditions a and c than in condition b in extension stretch (P<0.01), smaller in condition a than in conditions b and c in left/right lateral bending (P<0.01), and decreased significantly in the order of a<c<b in forward flexion stretch and left/right axial rotation (P<0.05). The ROM of segment L(2/3) was significantly smaller in conditions a and b than in condition c in extension stretch (P<0.01), but showed no significant differences between the 3 conditions in the other directions (P>0.05).

CONCLUSIONS

The ROM of the segment superior to the lumbar spine with rigid fixation increases in all the directions, but can be reduced with Coflex device implanted in the superior segment, which results in only increased ROM of the segment superior to Coflex device in extension stretch.