A study, published ahead-of-print in Neuromodulation, and led by Jean-Pierre Van Buyten, AZ Nikolaas, St Niklaas, Belgium, has examined the use of high-frequency spinal cord stimulation for the treatment of chronic back pain patients or patients with failed back surgery syndrome.
The trial was a prospective, open-label, multicentre European trial and the authors aimed to assess the Senza rechargeable spinal cord stimulation system (Nevro), which is capable of delivering stimulation pulse rates up to 10kHz without producing paraesthesia.
The authors, therefore, enrolled patients who fulfilled the criteria: 18 years or over at times of enrolment, primary diagnosis of chronic back pain with or without leg pain (intensity 5 out of 10 over the last 30 days on the visual analogue scale), previous failed response to six months of conventional treatment, and able to comply with the follow-up requirements of the study.
“Between August 2009 and February 2011, a total of 83 patients were enrolled and entered the trial phase of the study, with one patient withdrawing from the study during this phase,” said van Buyten and colleagues. “Of the 82 patients who completed the trial [phase], 88% (72 patients) had a successful trial and, consequently, underwent permanent implant.”
The patients underwent a baseline evaluation and at 30 days they were implanted with either a percutaneous trial (UK) or tunnelled trial (Belgium). At the end of the trial phase period, according to Van Buyten et al, only those patients with a successful outcome (50% reduction in pain intensity and ability to cope with the spinal cord stimulation requirements) were included in the second part of the study and were implanted with a permanent pulse generator.
The authors reported that in the patients implanted pulse generator, the device was then connected to the leads and implanted subcutaneously. After permanent implantation the patients were followed up at one, three and six months. “At six months, the reported visual analogue scale for back pain was 2.7 compared with 8.4 at baseline, a 78% median reduction. Visual analogue scores corresponding to leg pain also decrease from 5.4 at baseline to 1.4 at six months yielding an 83% median decrease,” they said.
“The reduction in back pain is statistically significant (p=0.001). Seventy four per cent of patients had greater than 50% pain relief and 47% of the patients had greater than 80% pain relief,” they added.
The Owestry Disability Index (ODI) and sleep disturbances were reported at six months to be significantly lower compared to baseline. Van Buyten and colleagues said that ODI values decreased from 55 at baseline down to 37 (p=0.001). They added that 57% patients had an improvement of 14 points or more, and mean sleep disturbances decreased from 3.7 at baseline to 1.3 at six months.
In the study, it was also reported that, previous to implantation, there was widespread use of opioids but this was reduced in 62% of patients at implantation and, at follow-up, a further 38% discontinued use.
“Eighty five per cent of patients were satisfied or very satisfied with the high-frequency spinal cord stimulation system, and 85% of them would recommend or highly recommend it to others with similar pain,” said van Buyten et al.
In all patients (83) who underwent trial and/or implantation 51 adverse effects were reported in 38 patients. According to the authors, the most commonly occurring adverse effects were pocket pain (31%), and lead migration (22%) and, because of these events, 13 patients underwent re-intervention.
“The results from this clinical study demonstrated that patients with chronic, intractable back and leg pain had significant pain relief after six months with the high-frequent spinal cord stimulation system,” concluded van Buyten and others. “The high-frequency spinal cord stimulation system appears to be efficacious in many back pain patients that fail to benefit from conventional stimulation.”
