(I-575) Effect Modifiers of Outcomes After Transforaminal Endoscopic Discectomy versus Microdiscectomy for Sciatica: Subgroup Analyses of the PTED-study

Introduction: Full endoscopic procedures are becoming increasingly popular to treat spine pathology. Recently, we published the results of a randomized controlled trial comparing Percutaneous Transforaminal Endoscopic Discectomy (PTED) with microdiscectomy and showed non-inferiority of PTED in leg pain reduction. Based on previous studies and on the surgical route of PTED (transforaminal versus dorsal during microdiscectomy), some type of disc herniations and some patient groups are hypothesized to be more suitable for one technique over the other. Compelling evidence on this, however, is lacking.

Methods: Data were used from a multicenter, non-inferiority, RCT comparing the effectiveness of PTED with microdiscectomy. Patients with at least 6 weeks of radiating leg pain and an MRI-confirmed lumbar disc herniation, were randomized between PTED or microdiscectomy. The primary outcome was leg pain as measured from a 0 to 100 visual analogue scale (VAS). Secondary outcomes include the ODI, VAS back pain and self-perceived recovery. Outcomes were measured longitudinally with the main evaluation point at 12 months. A priori three subgroups analyses were planned: (1) (para)median disc herniations; (2) (extra)foraminal disc herniations; and (3) disc herniations at L5-S1.

Results: Twelve months after surgery, 96% of the 530 patients had follow-up data available according to the per protocol analysis. Regardless of the allocated treatment, patients with (extra)foraminal disc herniations tended to have a higher VAS leg pain (mean difference 7.4, 95%CI 1.4 to 13.3), higher ODI (5.1, 95%CI 1.3 to 8.7) and lower odds for recover (odds ratio 0.5, 95%CI 0.3 to 0.8) than patients with (para)median disc herniations at 12 months. Patients with disc herniations at L5-S1 had similar clinical outcomes as patients with disc herniations at other levels.

Conclusion : The hypothesis that PTED is less suitable than microdiscectomy to treat (para)median discs or disc herniations above L5-S1, are not supported by this data. (Extra)foraminal disc herniations, however, might have slightly worse outcomes than (para)median disc herniations. These differences were, however, small and may not be clinically relevant.

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