Measurement Of Spinal Canal Volume Of Patient With Lumbar Spinal Stenosis Before And After Surgery On 3D Images Of CT And Its Application

Objective:The aims of this study were to evaluate the measurements of spinal canal volume in the patient with lumbar spinal stenosis(LSS)before and after surgery on three-dimensional reconstruction(3D)images of computed tomography(CT)and its application in minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF)for the treatment of LSS.Methods:(1)Measurements on different methods and validation:(1)Measurement methods:Measurements on 3D images of CT: the spinal canal volume was measured using a CT post-processing software,the median sagittal position of the spinal canal was taken as a reference,on the axial image,the distance between the upper and lower midpoint of each vertebral body of two neighboring vertebrae with the stenotic segment of the spinal canal was measured.Measurement on 2D images of CT: the cross-sectional area of the narrowest part of the stenotic spinal canal was measured on2 D images of CT in the PACS.(2)Water model validation: The reliability of measurement of the spinal canal volume was validated through comparing the measurement of the volume of the water model on CT images of the water model to the known volume of the water model.(3)Single-blinded validation using statistical analysis: The spinal canal volume was measured on images of CT of the patient with stenotic spinal canal before and after surgery by two radiologists independently andwith each one blinded to another,including 30 cases measured on 3D images and 57 cases measured on 2D images,and correlation between the two measurements was calculated.(2)Study on the measurements and surgical curative effects.The measurements were compared with the ODI scores of surgical curative effects.ODI scores of surgical curative effects were performed before and after surgery,respectively,which were matched with the measurements obtained from 3D and 2D images of CT,respectively.The changes of spinal canal volume and area before and after surgery based on measurements rendered from 3D and 2D images of CT were calculated,respectively,and correlation analyses were conducted for these parameters.(3)Evaluation of clinical application of the measurements of spinal canal on 3D and2 D images of CT for perioperative evaluation of the patient with stenotic spinal canal.Pearson correlation coefficient analysis was performed.Results:(1)Water model validation: The actual volume of the water model is 6778.054 cm3,the measurement of the spinal canal volume is 6675.094 cm3,and the accuracy is98.2 %.Single-blinded validation using statistical analysis: The results were:preoperative spinal canal volume measurements on 3D images of CT(r = 0.983,P =0.000),postoperative spinal canal volume measurements on 3D images of CT(r =0.979,P = 0.000);preoperative spinal canal area measurements on 2D images of CT(r = 0.996,P = 0.000),postoperative spinal canal area measurements on 2D images of CT(r = 0.997,P = 0.000).(2)After MIS-TLIF,the average spinal canal volume increased by 32.8 % on 3D images of CT,and the preoperative and postoperative average spinal canal volumes were(3.742 ± 1.311)and(4.875 ± 1.600),respectively.There was a statistically significant difference in spinal canal volume before and after surgery(P < 0.05).The preoperative and postoperative mean values of ODI scores in patients measured on 3D images of CT were(45.1 ± 11.0)and(9.8± 10.8),respectively,and there was significant difference between preoperative and postoperative ODI scores(P < 0.05).After the MIS-TLIF,the mean enlargement rate of the spinal canal in patients measured on 2D images of CT was 112.6 %,and the preoperative and postoperative average spinal canal area were(58.31 ± 27.70)and(107.24 ± 37.30),respectively.The difference of spinal canal area between before and after surgery was statistically significant(P < 0.05).The preoperative and postoperative average ODI scores were(54.34 ± 15.70)and(8.6 ± 9.4)in patients measured on 2D images of CT,respectively.There was significant difference between preoperative and postoperative ODI scores(P < 0.05).Pearson correlation coefficient showed that there was a correlation between the rate of improvement of spinal canal volume in 3D group and the improvement rate of ODI score(r = 0.45,P = 0.01);there was no correlation between improvement rate of spinal canal area and rate of improvement of ODI score in 2D group(r =-0.02,P = 0.89).(3)There was no correlation between the 3D spinal volume improvement rate and 2D spinal volume improvement rate(r =-0.13,P = 0.57).Conclusions:The measurements of the spinal canal volume and area of patient with lumbar spinal stenosis on 3D and 2D images of CT are accurate and feasible.The spinal canal volume,area and clinical symptoms of lumbar spinal stenosis after MIS-TLIF surgery are significantly increased or improved compared with those before surgery,but the correlation between spinal canal volume increment and improvement of ODI is significantly stronger than that the spinal canal area increment and improvement of ODI,which indicates that the measurements of the spinal canal volume of patient with lumbar spinal stenosis on 3D images of CT is superior and optimal.