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Suprailiac versus transiliac approach in transforaminal endoscopic discectomy at L5-S1: a new surgical classification of L5-iliac crest relationship and guidelines for approach.

Background
Approach to the L5-S1 level with transforaminal access can be challenging. Some surgeons employ the interlaminar or paraspinal endoscopic approach as an alternative apart from the other minimally invasive posterior surgical options. To precisely target and safely access disc herniations at L5-S1, the authors attempted to stratify patients into trans and supra iliac approach groups and propose a simple surgical classification based on the radiographic findings.


Methods
A prospective study was performed on a cohort of 90 patients with L5-S1 disc herniation who underwent transforaminal endoscopic discectomy through suprailiac or transiliac approach depending on the best trajectory to access the herniated disc. Preoperative radiological assessment was done on anteroposterior and lateral radiographs of the lumbosacral spine by two independent observers. The proposed classification and approach guidelines were used to stratify patients for the preferred access route. The outcome was measured as mean VAS and ODI scores pre-operative and at 6 months post-operative and compared using the null hypothesis (P value) and the paired t-test. The interrater reliability was calculated as the percentage agreement between different observers.


Results
The L5-S1 disc herniation was treated with the transforaminal approach in 46 patients via the suprailiac and in the remaining 44 patients via the transiliac approach. There were statistically significant VAS and ODI reductions in patients of both groups (P<0.05). Interrater reliability of 92.5% using percent agreement shows strong level of agreement.


Conclusions
This surgical approach classification based on radiographs aids in the preoperative planning for selection of patients to either suprailiac or transiliac approach for transforaminal endoscopic surgery at L5-S1 level.