Objective:To investigate the radiological measurements and features of the L5/S1 laminar space in the normal prone position and the posterior pelvic prone position

and to provide guidance for the translaminar approach for percutaneous spinal endoscopy in clinical practice.Methods:A total of 52 patients who underwent percutaneous spinal endoscopy in our hospital from January 2017 to December 2018 were enrolled According to the body position during surgery

they were divided into conventional group with the normal prone position and control group with the posterior pelvic prone position

with 26 patients in each group.Radiological examination was performed to measure the width of the L5/S1 unilateral laminar space and the height of the laminar space between 4 mm outward from the spinous process and 4 mm inward from the inner edge of the ipsilateral inferior articular process in the normal prone position and the posterior pelvic prone position.The two groups were compared in terms of time of endoscopic placement and of operation.Results:In the anteroposterior lumbar spine radiographs for the 52 patients

the height of the L5/S1 laminar space in the posterior pelvic prone position was significantly higher than that in the prone position（P < 0.05）

and there was no significant change in the width of the unilateral laminar space in the two groups（P > 0.05）.Compared with the conventional group

the control group had significantly shorter time of endoscopic placement and time of operation（P < 0.05）.Conclusion:The lumbosacral angle can be reduced in the posterior pelvic prone position

which can offset lumbar lordosis

increase the height of the laminar space

and provide help for preoperative placement of PEID（percutaneous endoscopic interlaminar discectomy）channel and intraoperative operation.The posture is easy to place and can be easily promoted in primary hospitals.