Low-Frequency Versus Combined High-Frequency Spinal Cord Stimulation for Failed Back Surgery Syndrome: A Single-Centre Retrospective Comparative Cohort Study from Belgium

Spinal cord stimulation (SCS) is an established therapy for Failed Back Surgery Syndrome (FBSS). The relative long-term performance of tonic low-frequency SCS (LF-SCS) and of combined high-frequency SCS (HFc-SCS), in which 10-kHz and tonic stimulation are delivered simultaneously, remains uncertain. We reviewed our own single-centre experience with both at one and two years.

Single-centre retrospective cohort study (Cliniques Universitaires Saint-Luc, Brussels). All patients permanently implanted for FBSS since 2019 were reviewed. Twenty-two were eligible: 13 LF-SCS and 9 HFc-SCS. Outcomes were pain (Visual Analogue Scale, VAS), responder rate (≥50% VAS reduction), opioid and neuropathic pain medication use at one and two years, and satisfaction (modified MacNab criteria) and disability (Oswestry Disability Index) at last follow-up. Non-parametric methods were used throughout.

At one year the two modalities were indistinguishable: median VAS reduction differed by 0 points (95% CI -2 to 2), with 85% and 78% responders. At two years (n = 16) the median individual improvement was 50% with LF-SCS and 13% with HFc-SCS (difference 38 percentage points, 95% CI 7 to 66), and 7 of 10 LF-SCS patients remained responders against 0 of 6. Median follow-up differed between groups (57 versus 33 months), a structural confound. Seven of 30 patients trialled developed trial-phase infection (23%); none followed permanent implantation.

In our cohort the two modalities performed equivalently at one year and diverged at two. Given the sample size, unequal follow-up and heterogeneous HFc programming, this divergence is an observation from our practice and is hypothesis-generating.