MRI辅助髓核容积测定评价单侧椎弓螺钉置入并椎间融合对邻近节段的影响

MRI measurement of nucleus pulposus volume to assess the influence of unilateral pedicle screw fixation with an interbody fusion cage on adjacent segment

BACKGROUND: A large number of biomechanical studies and clinical application research showed that unilateral pedicle screw fixation with a single cage can not only make the spine to obtain immediate stability, and also reduces the fixed segment stiffness. However, there is not related research on the change of adjacent segment disc nucleus pulposus volume with unilateral pedicle screw. OBJECTIVE: To evaluate the effects of unilateral pedicle screw fixation with a single cage on adjacent segment degeneration for treating lumbar degenerative disease with MRI measurement of lumbar nucleus pulposus volume.  METHODS: A total of 34 patients with lumbar disc herniation were treated by posterior lumbar interbody fusion with unilateral pedicle screw fixation with a single cage insertion. There were L4-5 segment in 16 patients (9 males and 7 females) and L5-S1 segment in 18 patients (10 males and 8 females). The fixator was taken out at 18 months after surgery. They were followed up for 24 to 36 months. With MRI, the transverse diameter and sagittal diameter of the nucleus pulposus were measured by using T2-weighted images at 6, 12, 18, 30 months after treatment, while the nucleus pulposus height was measured by middle sagittal position. Cephalic intervertebral height was measured with angular bisector method on X-ray films. Effects of unilateral pedicle screw fixation on cephalic intervertebral disc degeneration were evaluated according to nucleus pulposus volume and the intervertebral space height.  RESULTS AND CONCLUSION: (1) Nucleus pulposus volume at cephalic L3-4 on the fixed L4-5 segment was reduced in male patients after 30 months of treatment compared with pre-treatment (P=0.139), but increased in female patients (P=0.143). (2) Nucleus pulposus volume at L4-5 near to fixed L5-S1 segment was slightly reduced in male patients after 30 months of treatment (P=0.096); nucleus pulposus volume was slightly increased in female patients after 6, 12, 18 and 30 months of treatment (P > 0.05). (3) Disc space height at cephalic L3-4 near to L4-5 segment was diminished in male and female patients at 30 months of treatment (P > 0.05). (4) Disc space height at cephalic L4-5 near to L5-S1 segment was slightly reduced in male and female patients compared with pre-treatment (P > 0.05). (5) Unilateral pedicle screw with a single cage could effectively prevent adjacent segment degeneration in treatment of partial lumbar intervertebral degenerative disease.