gms | German Medical Science

Objective: Failed back surgery syndrome (FBSS) has become the mainstay indication for spinal cord stimulation (SCS) for refractory back and leg pain. Defining FBSS has been controversial but most authors define FBSS as one or more previous spine surgeries yielding inadequate pain relief. Physiological sagittal balance has been shown to correlate with quality of life (QOL) and physical health. Spinal alignment was not assessed in any of the widely cited RCTs demonstrating short-term efficacy of SCS. We analyzed spinal alignment in patients undergoing SCS to examine a) the frequency of severe spinal malalignment in this cohort, and b) the effect of spinal malalignment on the efficacy of SCS.

Methods: This is a retrospective analysis of patients undergoing SCS surgery between 2010 and 2014 after prior spinal surgery procedures at a large university medical center. Only patients with standing lumbar spine x-rays were included in this analysis. Surgimap software (Nemaris, Inc., USA) was used to assess spinopelvic (SP) parameters, including pelvic incidence (PI) and lumbar lordosis (LL). PI minus LL within 10 degrees was considered to reflect a balanced state. Pain levels at last follow-up were used to gauge SCS efficacy.

Results: 40 patients (20 f, 20 m; mean age: 60.5 yrs) met eligibility criteria and were included in this study. On average, patients had undergone 1.69 prior surgical treatments (range: 1 to 5). Lumbopelvic alignment (PI minus LL) was considered normal (±10°) in 16 patients (40%), imbalanced (within 10-20°) in 13 patients (32.5%), and severely imbalanced (>20°) in 11 patients (27.5%). At final follow-up (mean: 32±26 months), SCS showed significant pain reduction in 15 patients (37.5%) only. Average spinopelvic disharmony was 14.4 degrees in subjects with significant pain reduction, and 15.4 degrees in those without. These differences did not reach statistical significance.

Conclusion: In this cohort, 60% of patients undergoing SCS displayed spinopelvic malalignment in pre-operative x-rays. Overall clinical efficacy was not satisfactory in 62.5% of individuals, reporting no significant pain reduction after SCS. Differences in spinopelvic alignment in those patients benefiting from SCS and those without meaningful pain reduction did not reach statistical significance in this cohort. Lumbopelvic alignment is likely not relevant for SCS efficacy. Other alignment parameters correlating with QOL could better help identify those benefitting from SCS treatment and those requiring corrective surgery.