Relationship between exiting nerve roots and superior articular process: a CT study of lumbar anatomy

English Keywords:Lumbar exiting nerve roots  Superior articular process  CT  Lumbar discectomy

English Abstract:

  【Abstract】 Objectives： To measure the distance between the exiting nerve roots and the superior articular process in the lumbar intervertebral foramen by the multi-planar reformation(MPR) technique, and to provide important anatomic reference for clinical percutaneous transforaminal spinal endoscopic surgery. Methods: This study included 60 healthy volunteers who underwent multi-slice spiral CT continuous tomography from January to February 2018, 30 males and 30 females, with an average age of 50.8±13.2(21-73) years. The scanned CT images were reformatted by MPR technique to measure the distance between the exiting nerve roots and the tip of the superior articular process, the midpoint of the superior articular process, the root of the superior articular process in the L1-L5 intervertebral foramen. Results: ①The distances between the exiting nerve roots and the superior articular process in the L1-L5 intervertebral foramen were not significantly different between different genders or between the left and right side of lumbar spine(P>0.05). ②The distances between the exiting nerve root and the superior articular process gradually increased from L1 to L5, but the differences were only about 1mm. The distances between the L5 exiting nerve root and the tip, the midpoint, the root of the superior articular process were 3.91±0.50mm, 4.67±0.57mm, 5.77±0.56mm respectively. ③The distances between the exiting nerve root and the tip, the midpoint of the leading edge, the root of the superior joint gradually increased, and the maximum distances were 4.29±0.20mm in L1, 4.36±0.27mm in L2, 4.61±0.44mm in L3, 4.92±0.39mm in L4, 5.77±0.56mm in L5. ④The distance between the exiting nerve roots and the superior articular process gradually increased from tip to root in L1-L5, and the differences ranged from 0.92±0.31mm to 1.86±0.57mm, which presented a trapezoid shape. Conclusions: The three-dimensional bone-nerve space between the exiting nerve root and the superior articular process in the lumbar intervertebral foramen is approximately parallel or trapezoid shape which is narrow in proximal end and wide in distal end. To reduce the injury rate of exiting nerve roots in PELD, the foraminoplasty to enlarge the intervertebral foramen near the facet joint is strongly recommended before the introduction of 7.5mm-diameter working cannula.