CT-based analysis of the approach of percutaneous endoscopic lumbar interbody fusion

Objective To analyze the relationship between the nerve root and its surroundings to their corresponding intervertebral disc for percutaneous endoscopic lumbar interbody fusion approaches. Methods A retrospective study in Tianjin Hospital from January 2017 to October 2017 was carried out. The CT images were obtained from patients presented with low back pain. One hundred and ten CT data were collected and the images were processed by graphic workstation(AW46) for measuring. The CT analysis was done bilaterally from L2/3 to L5/S1. On the vertical plane of long-axis of pedicle which nerve root was visible, nerve root- dural sac distances were analyzed at the superior and inferior margin of the disc(Js, Ji). Also, nerve root-pedicle distances were at the medial, middle and lateral borders of the pedicle(Pa, Pb, Pc). On transverse plane, nerve root-articular process and nerve root-articular process joint surface shortest distance were analyzed at the superior and inferior margin of the disc(Gs, Gi)respectively. Results From L2/3 to L5/S1, the distances of nerve root- dural sac were larger at inferior margin of the disc. The smallest Js was measured at the superior margin of L2/3 (6.71±2.10)mm and the largest Ji was measured at the inferior margin of L5/S1(22.05±3.96)mm. And from L2/3 to L5/S1, each segment of vertebral nerve root-pedicle distances was gradually reduced from medial to lateral, as well as Pb and Pc. The smallest distance was Pc of L5/S1 (3.86± 1.93) mm. The shortest distance of nerve root-articular process joint surface at inferior margin of disc was larger than the distance of nerve root-articular process at superior margin of the disc from L2/3 to L5/S1. Conclusions It is more difficult to implant a cage with a width of 10 mm above L3/4 segment. By removing the parts of superior articular process, it could expand the safe working area, and avoid hurting nerve or other structures when implanting a cage. Key words: Spinal fusion; Endoscopy; Nerve root; Tomography, X-ray computed; Surgical approach