CT Evaluation Of The Influence Of The Single Versus Double Cages Implantation On The Structural Symmetry Of The Adjacent Segments In Lumbar Interbody Fusion

Objective:To investigate the influence of single and double cages implantation on the structural symmetry of adjacent segments through CT evaluation of adjacent segments in lumbar interbody fusion.Methods:From March 1,2019 to October 31,2020,90 patients with L4-5 or L5-S1 lumbar disc degeneration(all single-segment lesion)were selected.Posterior Lumbar Interbody Fusion(PLIF)was adopted for decompression with fenestration on the pathogenic side,discectomy and fusion cage implantation.By a random method,45 cases were implanted with a single fusion cage and 45 cases were implanted with double cages.There were 46 cases at L4-5 segments and 44 cases at L5-S1 segment.Use Mimics Medical software to reconstruct the three-dimensional CT data before and after the operation,then make the facet joint surface of the adjacent segments and the three-dimensional planes(sagittal plane,coronal plane and horizontal plane)relative to the lower vertebral body.Use 3-matic Research software to measure the angle between the facet joint surface and the three-dimensional planes of the vertebral body,and calculate the symmetry of the facet joint surface of the lumbar spine on the left and right sides.Use 3-matic Research software to determine the left,middle,and right three poles of the upper and lower endplates of the intervertebral space,and make the endplate plane based on this,measure the distance between the left,middle,and right poles and the angle between the upper and lower endplate planes(ie Intervertebral angle).Results.(1)For patients with L4-5 segment degeneration and single fusion cage implanted,The difference between the preoperative and postoperative groups for the symmetry of the facet joint surface relative to the sagittal plane and the coronal plane at L3-4 segment was statistically significant(P<0.05).The difference between the preoperative and postoperative groups for the symmetry of the facet joint surface relative to the coronal plane and the horizontal plane at L5-S1 segment was statistically significant(P<0.05).For patients with degeneration of the lumbar intervertebral disc at L5-S1 segment and implanted with a single fusion cage,the difference between the preoperative and postoperative groups for the symmetry of the facet joint surface relative to the sagittal plane and the coronal plane at L4-5 segment was statistically significant(P<0.05).(2)For patients with L4-5 or L5-S1 segment degeneration and single fusion cage implanted,the difference between the preoperative and postoperative groups for the symmetry of the facet joint surface relative to the three-dimensional planes at adjacent segment was not statistically significant(P > 0.05).(3)Compare the symmetry of the facet joint surface relative to the three-dimensional planes at adjacent segment between the single and double cages groups for patients with L4-5 segment degeneration.The difference between the single and double cages groups for the symmetry of the facet joint surface relative to the three-dimensional planes at L3-4 segment was statistically significant(P<0.05).The difference between the single and double cages groups for the symmetry of the facet joint surface relative to the coronal plane and the horizontal plane at L5-S1 segment was statistically significant(P<0.05).Compare the symmetry of the facet joint surface relative to the three-dimensional planes at adjacent segment between the single and double cages groups for patients with L5-S1 segment degeneration.The difference between the single and double cages groups for the symmetry of the facet joint surface relative to the sagittal plane and the coronal plane at L4-5 segment was statistically significant(P<0.05).(4)For patients with L4-5 segment degenerative disease,the difference in the distance between the left and right poles of the L3-4 and L5-S1 segment after the operation was statistically significant between the single and double cages groups(P<0.05).For patients with L5-S1 segment degenerative disease,the difference in the distance between the left and right poles of the L4-5 segment after surgery was statistically significant between the single and double cages groups(P<0.05)(5)For patients with L4-5 segment degenerative disease,the difference between the single and double cages groups for the preoperative and postoperative changes of L3-4 and L5-S1 intervertebral angles was statistically significant(P >0.05).For patients with L5-S1 segment degenerative disease,the difference between the single and double cages groups for the preoperative and postoperative changes of L4-5intervertebral angles was statistically significant(P<0.05).Conclusion:(1)The implantation of double cages can effectively improve the symmetry of the intervertebral space compared with the implantation of a single cage.The effect of implanting double cages in the L5-S1 segment on the adjacent segment was significantly greater than that of implanting double cages in the L4-5 segments on the adjacent segments.When double cages need to be implanted in the L5-S1 segment,the slightly smaller cage can be appropriately considered to reduce the excessive expansion caused by the double cages,so as to reduce the influence of implantation on the adjacent segment.(2)The implantation of a single cage will lead to a significant decrease in the symmetry of the facet joints of the adjacent segments.Compared with implanting a single cage,the implantation of double cages can effectively improve the symmetry of the facet joint surface of the adjacent segment.