Percutaneous Endoscopic Lumbar Discectomy for L5-S1 Disc Herniation: Consideration of the Relation between the Iliac Crest and L5-S1 Disc

Background: Percutaneous transforaminal techniques for the treatment of lumbar discherniation have markedly evolved. Percutaneous endoscopic lumbar discectomy (PELD) for L5-S1disc herniation is regarded as challenging due to the unique anatomy of the iliac crest, large facetjoint, and inclinatory disc space. Among these, the iliac crest is considered a major obstacle. Thereare no studies regarding the height of the iliac crest and their appropriate procedures in PELD.Objectives: This study discusses PELD for L5-S1 disc herniation and the appropriate approachaccording to the height of iliac crest.Study Design: Retrospective evaluation.Methods: 100 consecutive patients underwent PELD via the transforaminal route for L5-S1 discherniation by a single surgeon. The study was divided into 2 groups: the foraminoplasty grouprequiring foraminal widening to access the herniated disc and the non-foraminoplasty grouptreated by conventional posterolateral access. Radiological parameters such as iliac height, therelative position of the iliac crest to the landmarks of the L5-S1 level, iliosacral angle and foraminalheight, and disc location were considered. Clinical outcomes were assessed by the Visual AnalogueScale (VAS, 0 – 10) for back and leg pain, the Oswestry Disability Index (ODI, 0 – 100%), and themodified MacNab criteria.Results: The overall VAS scores for back and leg pain decreased from 6.0 to 2.3 and from 7.5to 1.7. The mean ODI (%) improved from 54.0 to 11.6. Using modified MacNab criteria, a goodoutcome was 92%. Foraminoplasty was required in 19 patients. Iliac crest height was significantlyhigher in the foraminoplasty group than the non-foraminoplasty group (37.7 mm vs 30.1 mm,P < 0.001). In the foraminoplasty group, the iliac crest is above the mid L5 pedicle on lateralradiography in all cases. There were no significant differences in foraminal height, foraminal width,iliosacral angle, or disc height between the 2 groups. In addition, there were no differences inclinical outcome between the 2 groups.Limitations: This study is a retrospective analysis and simplifies the complexity of the L5-S1 leveland iliac bone using two-dimensional radiography.Conclusion: In high iliac crest cases where the iliac crest is above the mid L5 pedicle in lateralradiography, foraminoplasty may be considered for transforaminal access of L5-S1 disc herniation.Conventional transforaminal access can be utilized with ease in low iliac crest cases where the iliaccrest is below the mid-L5 pedicle.Key words: Percutaneous endoscopic lumbar discectomy, transforaminal, L5-S1, iliac crest,foraminoplasty