Value of somatosensory evoked potential in the treatment of lumbar spinal stenosis with oblique lumbar interbody fusion

English Keywords:Degenerative lumbar spinal stenosis  Oblique lumbar interbody fusion  Somatosensory evoked potential

English Abstract:

  【Abstract】 Objectives: To explore the value of intraoperative somatosensory evoked potential (SEP) monitoring in the treatment of degenerative lumbar spinal stenosis with oblique lateral interbody fusion(OLIF). Methods: The data of 92 patients who underwent combined OLIF and unilateral pedicle screw fixation for degenerative lumbar spinal stenosis with SEP monitoring the operation in General Hospital of Ningxia Medical University from July 2017 to February 2019 were retrospectively reviewed. According to Lee′s grading system of lumbar central canal stenosis, all patients were divided into grade 1 group (n=31), grade 2 group (n=33) and grade 3 group(n=28). Our follow-up study lasted 12-23 months, averaged 15.6±1.8 months． The amplitude of SEP was recorded and analyzed before disk excision and 5 minutes after implantation of fusion cage in each group. The cross-sectional area in the dura(CAD) was measured on T2WI axial MRI. The disk height(DH) and intervertebral foramen height(IFH) were measured on the lateral X-ray. Visual analog scale(VAS) score and JOA score of lumbar spine were used to evaluate the clinical effect. Pearson correlation analysis was used to analyze the correlation between the improvement rate of SEP amplitude and the improvement rate of the radiographic and clinical results. Results: There were significant changes in the average amplitude of SEP in the three groups before disk excision and after implantation of fusion cage under general anaesthesia(P<0.05). The average improvement rate of SEP amplitude in grade 1, grade 2 and grade 3 groups were (48.32±7.37)%, (112.34±18.67)% and (28.05±6.78)% respectively, while 3 patients in grade 3 group showed no changes in SEP amplitude. At the last follow-up, the DH, IFH, CAD, lumbocrural pain VAS score and JOA score of the three groups were significantly improved compared with those at pre-operation(P<0.05). The change values of DH, IFH and CAD in grade 2 group were larger than those in grade 1 group and grade 3 group(P<0.05); There were significant difference in the change values of lumbocrural pain VAS score and JOA score among the three groups(P<0.05). By the evaluation standard of JOA score, at the last follow-up, the average improvement rate of JOA score in grade 1, grade 2, and grade 3 groups were (87.0±36.2)%, (85.8±35.3)% and (46.1±26.2)% respectively, and the excellent and good rate were 93.5%(29/31), 84.8% (28/33) and 50%(14/28) respectively. The improvement rate of SEP amplitude in grade 1 and grade 2 groups were positively correlated with the improvement rate of DH, IFH, CAD, lumbocrural pain VAS score and JOA score. The improvement rate of SEP amplitude was weakly correlated with the improvement rate of CAD, leg pain VAS score and JOA score in the grade 3 group. The improvement rate of SEP amplitude in eligible cases in grade 1 group was more than 25.6%, and that in grade 2 group was more than 85.3%. Conclusions: The improvement rate of SEP amplitude during the OLIF procedure in the treatment of grade 1 and grade 2 lumbar spinal stenosis can be used as an important reference index to judge whether the indirect decompression is effective or not, and it has some reference value for evaluating the degree of indirect decompression in the operation.