CT‐based Morphometric Analysis of Approach of Percutaneous Transforaminal Endoscopic Lumbar Interbody Fusion

Abstract

Objectives A radiographic study was designed to measure the relationship of the exiting nerve root and its surroundings to the corresponding intervertebral disc for percutaneous transforaminal endoscopic lumbar interbody fusion to better understand the regional anatomy and to improve clinical applications. Methods A retrospective study from January 2017 to October 2017 was conducted at Tianjin Hospital. CT images were obtained from patients presenting low back pain (110 patients), and analysis was performed bilaterally from L2‐3 to L5S1. In the rotating coronal plane we analyzed: the nerve root–dural sac distance at the superior and inferior margins of the disc (Js, Ji); the nerve root–pedicle distance at the medial, middle, and lateral borders of the pedicle (Pa, Pb, Pc); the pedicle width (W); and the safe working zone, defined as a trapezoid bounded by the inferior pedicle and the exiting nerve root (S). In the transverse plane, the nerve root‐articular process and the shortest distance for the nerve root‐articular process joint surface were analyzed at the superior and inferior margins of the disc (Gs, Gi), respectively. The groups were analyzed using ANOVA, and paired t‐tests were used to compare the left and right sides. Results From L2‐3 to L5S1, the distance of the nerve root to the dural sac was larger at the inferior margin of the disc. From L2‐3 to L5S1, each segment of the vertebral nerve root‐pedicle distance gradually decreased from medial to lateral. From L2‐3 to L5S1, the distance from the exiting nerve root to the middle and lateral margins of the pedicle gradually decreased, with L5S1 being the minimum. Some significant differences were observed between the left and right sides for L4‐5 and L5S1. The pedicle width of the vertebral body and the mean area for the safe working zone gradually increased from L2‐3 to L5S1. In the axial plane, the shortest distance between the nerve root and articular process joint surface at the inferior margin of the disc was greater than the distance for the nerve root to the articular process at the superior margin of the disc from L2‐3 to L5S1. There were no significant differences between the two sides. Conclusions It is more difficult to implant a cage with a width of 10 mm above the L3‐4 level. By removing part of the superior articular process, the safe working area can be expanded, and damage to the nerve or other structures can be avoided when implanting a cage.

Cadaveric anatomy of the lumbar triangular safe zone of Kambin’s in North West Indian population

“…We found that the area gradually increased from L1-2 space to L4-5 space. The observations by the present authors are in accordance with that of Zhang et al [ 14 ] but do not correlate with that of Ozer et al [ 15 ] and Wimmer and Maurer [ 16 ]. The reason for differences in dimensions may be due to the different methodologies used by the later.…”

“…Zhang et al [ 14 ] in a retrospective CT based study in 110 Chinese patients with low back pain found that the mean area for the safe working zone gradually increased from L2-3 to L5-S1. However, they considered the safe zone to be a trapezoid area bounded by exiting nerve root and inferior pedicle.…”

“…The differences might be due to slight change in the position of the vertebral column during measurement on both sides or due to bilateral variation in bony components or intervertebral discs, although proper care had been taken to avoid any confounding factors and mean of three values were considered to avoid possible error. Zhang et al [ 14 ] observed difference in the safe working zone between both the sides at L4-5 and L5-S1 level which they opined was due to differences they found in the vertical distance between middle of the pedicle and exiting nerve root. However, we have not considered this parameter in our study.…”

“…The reason for differences in dimensions may be due to the different methodologies used by the later. Most of the earlier authors concluded that the maximum area is at the L4-5 level [ 6 , 8 , 14 ].…”

Oblique Fixation from Posterior Corner in Lumbar Spine Through Kambin’s Triangle: A Neuroimaging Anatomic Assessment

“…The majority of lumbar interbody fusion surgeries with integrated endoscopy system are performed through the transforaminal approach [14][15][16][17][18]. Anatomical studies have shown that the size of Kambin's triangle in each segment of the lumbar spine is safe for interbody fusion cages [19][20].…”