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 disc herniation have markedly evolved. Percutaneous endoscopic lumbar discectomy (PELD) for L5-S1 disc herniation is regarded as challenging due to the unique anatomy of the iliac crest, large facet joint, and inclinatory disc space. Among these, the iliac crest is considered a major obstacle. There are 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 approach according to the height of iliac crest. STUDY DESIGN Retrospective evaluation. METHODS 100 consecutive patients underwent PELD via the transforaminal route for L5-S1 disc herniation by a single surgeon. The study was divided into 2 groups: the foraminoplasty group requiring foraminal widening to access the herniated disc and the non-foraminoplasty group treated by conventional posterolateral access. Radiological parameters such as iliac height, the relative position of the iliac crest to the landmarks of the L5-S1 level, iliosacral angle and foraminal height, and disc location were considered. Clinical outcomes were assessed by the Visual Analogue Scale (VAS, 0 - 10) for back and leg pain, the Oswestry Disability Index (ODI, 0 - 100%), and the modified MacNab criteria. RESULTS The overall VAS scores for back and leg pain decreased from 6.0 to 2.3 and from 7.5 to 1.7. The mean ODI (%) improved from 54.0 to 11.6. Using modified MacNab criteria, a good outcome was 92%. Foraminoplasty was required in 19 patients. Iliac crest height was significantly higher 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 lateral radiography 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 in clinical outcome between the 2 groups. LIMITATIONS This study is a retrospective analysis and simplifies the complexity of the L5-S1 level and iliac bone using two-dimensional radiography. CONCLUSION In high iliac crest cases where the iliac crest is above the mid L5 pedicle in lateral radiography, 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 iliac crest is below the mid-L5 pedicle.