Research Of The Morphology Of The Lumbar Foraminal In Patients With Spondylolysis By MSCT

Backgrounds and PurposesAs lumbar spondylolysis and isthmic spondylolisthesis, the rate of the miss-diagnosis of it was high simply by means of ordinary X-ray or axial CT scanning. Similarly, the inadequate understanding of intervertebral foramen lesion and the exact location and extent of nerve root compression caused by LS in part led to the Failed Back Surgery Syndrome (FBSS). Multi-slice CT (MSCT) with isotropic properties could achieve a CT scan of the same quality of imaging, fully displaying its direct and indirect signs including the intervertebral foramen stenosis and the exact location and extent of nerve root compression.Most research is focusing on various CT signs of lumbar spondylolysis, comparative study of CT imaging method, the study of normal intervertebral foraminal, the pathogeny and CT signs of the intervertebral foraminal stenosis. For patients with lumbar spondylolysis and isthmic spondylolisthesis, related researchs on foraminal diameter measurement, shape changes and their impact factors, the extent of foraminal nerve root compression by MSCT , and the relationship between it and clinical symptoms are still less.In this paper, by the multi-planar reconstruction technique of MSCT, the comparison of size of intervertebral foramen was performed between patients with LS and ISS and in normal control. The percentage of slipping of the spondylolisthesis and the height of the posterior margin of lumbar vertebra interval were analyzed. Additionally, we observed the extent of intervertebral foramen stenosis and the status of nerve root retraction and compression in patients with LS and ISS, to see whether the observations were consistent with clinical symptoms or not.Materials and MethodsIn case group, 34 patients with LS were collected from the 2nd Xiangya Hospital of Central South University between August 2008 and April 2009, including 18 cases of male and 16 cases of female, aged from 16 to 69 years (mean 48.3±12.66 years). In the normal control group, healthy people with matched age and gender were enrolled.The anteroposterior diameter and vertical diameter of lumbar intervertebral foramen in both groups were measured by Siemens SOMATOM Sensation 64-slice spiral CT image through multi-planar reconstruction (MPR), as well as the percentage of slipping of spondylolisthesis and the height of the posterior margin of lumbar vertebra interval in case group. Then, the difference between the normal group and case group was statistically analyzed, as well as the relationship of the percentage of slipping of spondylolisthesis, the height of the posterior margin of lumbar vertebra interval and the size of the intervertebral foramen.ResultsNormal foraminals of 34 people in control group presented inverted teardrop-shaped performance, foraminal nerve roots are located within the upper recess, surrounded by the adipose tissue.The morphological changes of intervertebral foramen in patients with LS and ISS: according to the foraminal narrow semi-quantitative grading system put forward by Wildermuth, 5 cases were classed as 0 grade; 12 cases as 1 grade; 11 cases as 2 grade; 6 cases as 3 grade. With the percentage of slipping of lumbar isthmic spondylolisthesis increasing, the morphology of intervertebral foramen was changed from the normal form of inverted teardrop to forward and backward ladder-shift of superior and inferior recess, until the absolute separation. Similarly, the morphologic changes of nerve root were from normal to retraction, compression and even could not be displayed. There were 19 cases with symptoms related to nerve root lesion, 17 of which were consistent with the extent of intervertebral foramen stenosis and nerve root compression on CT images (89.5%).Compared with normal group, the anteroposterior diameter and vertical diameter of lumbar intervertebral foramen in case group were both smaller. The difference between them was statistically significant (P<0.05). The percentage of slipping of spondylolisthesis were negatively correlated with the vertical diameter of the intervertebral foramen (r=-0.817, P<0.05), while there was no correlation between the percentage of slipping of spondylolisthesis and the anteroposterior diameter (r=0.133, P>0.05). The height of the posterior margin of lumbar vertebra interval was positively correlated with the vertical diameter of the intervertebral foramen (r=0.694, P<0.05), while there was no correlation between the height of the posterior margin of lumbar vertebra interval and the anteroposterior diameter of the intervertebral foramen (r=0.124, P>0.05).Conclusions1. Multi-planar reconstruction (MPR) of Multi-slice spiral CT could fully display the change of the morphology of intervertebral foraminal and the degree of nerve root compression for patients with LS and ISS. The consistent rate with clinical nerve root compression symptom is 89. 5%.2. The anteroposterior and vertical diameter of intervertebral foramen in case group were quite smaller than those in normal group.3. The vertical diameter of intervertebral foramen was negatively correlated with the percentage of slipping of spondylolisthesis, while positively correlated with the height of the posterior margin of lumbar vertebra interval.Multi-planar reconstruction (MPR) of Multi-slice spiral CT was a effective method to detect the morphology of intervertebral foramen and nerve root for patients with LS and ISS and should be used as a routine preoperative examination.