BACKGROUND: The effect of indirect decompression after lateral lumbar interbody fusion (LLIF) is widely acknowledged; however, its details remain unclear. This study aimed to evaluate the immediate effects of indirect decompression just after LLIF cage placement but just before posterior instrumentation, using intraoperative computed tomography myelogram (iCTM). METHODS: Fifty-three levels from 28 patients undergoing LLIF with iCTM, were included in this retrospective study. Radiographic parameters were obtained from preoperative computed tomography myelogram and iCTM. Segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were compared preoperatively and intraoperatively to assess the neural decompression just after LLIF cage placement. Canal stenosis status during axial computed tomography myelogram was classified into 3 grades according to modified Schizas's grading to determine the necessity of additional posterior decompression procedures. The Oswestry Disability Index was obtained before and 3 months after the operation. RESULTS: Significant improvements in all radiological parameters of segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were observed just after LLIF cage placement. However, 11 (21%) levels had insufficient neural decompression status with iCTM grade (10 central canal and 1 lateral recess stenosis), requiring further direct posterior decompression. The difference in the improvement of Oswestry Disability Index between the decompression and nondecompression group was not significant, suggesting the validity of our decision. CONCLUSIONS: Detailed evaluation with iCTM revealed that adequate indirect decompression with LLIF was not always obtained, validating the intraoperative decision of further posterior decompression. This procedure, LLIF with iCTM, may reduce the risk of unnecessary direct decompression and reoperation after insufficient indirect decompression.
BACKGROUND: The effect of indirect decompression after lateral lumbar interbody fusion (LLIF) is widely acknowledged; however, its details remain unclear. This study aimed to evaluate the immediate effects of indirect decompression just after LLIF cage placement but just before posterior instrumentation, using intraoperative computed tomography myelogram (iCTM). METHODS: Fifty-three levels from 28 patients undergoing LLIF with iCTM, were included in this retrospective study. Radiographic parameters were obtained from preoperative computed tomography myelogram and iCTM. Segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were compared preoperatively and intraoperatively to assess the neural decompression just after LLIF cage placement. Canal stenosis status during axial computed tomography myelogram was classified into 3 grades according to modified Schizas's grading to determine the necessity of additional posterior decompression procedures. The Oswestry Disability Index was obtained before and 3 months after the operation. RESULTS: Significant improvements in all radiological parameters of segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were observed just after LLIF cage placement. However, 11 (21%) levels had insufficient neural decompression status with iCTM grade (10 central canal and 1 lateral recess stenosis), requiring further direct posterior decompression. The difference in the improvement of Oswestry Disability Index between the decompression and nondecompression group was not significant, suggesting the validity of our decision. CONCLUSIONS: Detailed evaluation with iCTM revealed that adequate indirect decompression with LLIF was not always obtained, validating the intraoperative decision of further posterior decompression. This procedure, LLIF with iCTM, may reduce the risk of unnecessary direct decompression and reoperation after insufficient indirect decompression.