Introduction: This study investigates the efficacy of long term follow-up of subcutaneous stimulation (SubQ) as an additional therapy for patients with failed back surgery syndrome (FBSS) with chronic refractory pain, for whom spinal cord stimulation (SCS) alone was unsuccessful to treat low back pain.
Materials/Methods: FBSS patients with chronic back and leg pain, whose conventional therapies had failed, received a combination of SCS (Octad lead) and/or SubQ (4-contact Quad Plus lead(s). Initially SCS trial stimulation was given to assess response to suppression of leg and/or low back pain. In case SCS alone was insufficient to treat low back, SubQ lead(s) were placed in the subcutaneous tissue of the lower back in the middle of the pain area. We investigated the long term effect of neuromodulation on pain with the visual analogue scale (VAS) and disability using the Quebec Pain Disability Scale. The results after 12 and 46 months are presented.
Results: Ten patients (age 51+/−8 years) were included in this study.
Baseline scores for leg (n = 8) and low back pain (n = 10) were VASbl: 59+/−15 and VASbl: 63+/−14, respectively. Mean follow up period was 46+/−4 months. Although leg pain scores increased over time, SCS significantly reduced this pain after 12 months (VAS12: 20+/−11, p12 = 0.001) and 46 months (VAS46: 37+/−17, p46 = 0.027). Similarly, although low back pain scores worsened over time compared to baseline, also SubQ significantly reduced this pain after 12 months (VAS12: 33+/−16, p12 = 0.001) and 46 months (VAS46: 40+/−21, p46 = 0.013). At 12 months the QPDS was 49+/−12 and after 46 months 53+/−15. Both at 12 and 46 months QPDS values were statistically significant better (p12 = 0.001, p46 = 0.04) compared to baseline values (QPDSbl: 61+/−15).
In one patient the effect of SCS/SubQ has disappeared completely over time and the pain scores returned to pre-stimulation values. Two patients who returned to work after onset of SCS/SubQ are still at work after 43 and 50 months follow up.
In 4 patients back pain scores increased over time due to new diagnoses (SI-joint problems, degenerative spine problems, disc problems and hip pain) unrelated to FBSS and for which SCS/SubQ was not targeted or a reason for implantation.
Discussion: This is the first prospective report on the combined use of SCS and SubQ with a follow up period of 4 years. These data show that SCS and/or SubQ provide long term pain relief for leg and back pain in patients with FBSS. One should take into account that in this chronic back pain population new back/leg pain causes, unrelated to FBSS, may evolve.
Conclusions: SCS plus SubQ can be considered as an effective long term treatment for back pain in patients with FBSS for whom SCS alone is insufficient in alleviating their pain symptoms. Pain scores for back pain can be significantly influenced by new indications unrelated to FBSS.
Keywords: peripheral nerve field stimulation, chronic pain, failed back surgery syndrome