1. Prospective study to evaluate the effectiveness of DRG stimulation
for treating discogenic low back pain
J. Kallewaard, MD1; M. van Kleef, MD, PhD2; J. van Susante, MD1; C. Edelbroek1; J. Geurts2; William Cusack, PhD3; Jeffery Kramer, PhD3
1Rijnstate Ziekenhuis, Velp, The Netherlands; 2Maastricht University Medical Center, Maastricht, The Netherlands;3St. Jude Medical, Inc., Sunnyvale, CA, USA.
BACKGROUND
PRELIMINARY RESULTS
PRELIMINARY RESULTS
Low back pain (LBP) has a lifetime prevalence of 70%1. Chronic low back pain (CLBP) is generally defined by symptoms lasting for more than 3 months; often leading to a low quality of life due to pain, disability and loss of work productivity2-3. Previous studies suggest that approximately 40% of CLBP is caused by internal disc disruption and involves vascularized granulation tissue containing sensitized nociceptive nerves4. Despite promising results in anti-inflammatory and ablation methods, the ideal interventional treatment has yet to be found5-6.
Stimulation of the dorsal root ganglia (DRG) is a safe and effective treatment for a variety of chronic pain conditions including failed back surgery syndrome (FBSS) and general CLBP7. Those diagnosed with the latter represent a heterogeneous population. The dorsal aspects of the lumbar (L4-L5) intervertebral discs are known to be a source of discogenic low back pain. These areas are innervated by sensory afferents that project through somatic spinal nerves, as well as by sympathetic nerves; both of which converge in the L1-L2 DRGs.
Thus, DRG stimulation at these levels may be effective for low back pain by recruiting both segmental and non-segmental neural pathways that are not otherwise accessible via traditional SCS. The purpose of this study is to evaluate the effectiveness of DRG stimulation in a homogenous sub-population consisting of those with discogenic CLBP.
For the 12 subjects that were tracked following a successful DRG neurostimulator trial, baseline NPRS in the primary area of pain (back) was reduced from 7.19±1.47 to 2.29±2.27 at the end-of-trial follow-up, for an average pain relief of 68.20%. At the 2-week follow-up, 11/12 subjects (91.67%) reported ≥50% pain reduction in the primary area of pain (back).
This effect proved preliminarily durable, as NPRS at the 6-month follow-up in the 6 available subjects remained low at 1.67±2.34, a pain reduction of 76.81%. Further, 3/6 subjects (50.00%) reported NPRS scores of zero in the primary area of pain (back).
Concomitant short-term and long-term improvements in secondary clinical outcomes were also demonstrated. Average quality of life was increased by 61.79% and 54.57% over baseline at the 2-week and 6-month follow-ups, respectively. Similarly, average disability and total mood disturbance were decreased compared to baseline by 60.00% and % at the 6-month follow-ups, respectively. * *
Figure 1: Consort diagram showing the inclusion/exclusion criteria, subject selection process and follow-up consistency for subjects receiving DRG stimulation.
Figure 2: Pain ratings in the primary area of pain (back) were reduced in subjects with DRG stimulation. Compared to baseline, significant pain reduction was achieved at the end-of-trial follow-up (t(22)=7.88, p<0.001) and was sustained at the 6-month follow-up (t(16)=5.88, p<0.001). * *
DISCUSSION *
These results suggest that DRG stimulation at the L2 level may be an effective treatment option for discogenic low back pain in a strictly selected group of patients that are inadequately responsive to medication, conservative therapy, or minimally invasive pain treatments. Further randomized controlled trials are required to affirm effectiveness, as the position of this modality in the discogenic low back pain treatment algorithm is unclear.
METHODS
This is a prospective, single-arm, multi-center, post-market, observational pilot study to collect data on pain relief (Numerical Pain Rating Scale, NPRS), subject satisfaction (Patient Global Impression of Change, PGIC), quality of life (EuroQol Five Dimensions Questionnaire, EQ-5D), and physical functioning (Oswestry Disability Index, ODI). Inclusion criteria for the study included:
- Chronic low back pain of at least 6 months
- History consistent with discogenic low back pain (e.g. Pain produced on lumbar motion, significant functional limitation in sitting duration and tolerance)
- Neurologic exam without marked motor deficit.
- Definite/Highly Probable/Discogenic Pain as confirmed by provocative discography according to IASP/ISIS guidelines
- Low Back Pain intensity should be 6 or higher measured on a NPRS at baseline
A total of sixteen subjects were consented and enrolled, with 14 continuing on to a trial phase. Twelve subjects experienced a positive stimulation trial and proceeded to permanent implantation at the L2 spinal level (85.7% responder rate). Data were collected at baseline, and at the 2-week, 3-month, and 6-month follow-ups. Primary and secondary clinical outcome measurements at each follow-up were compared to those at baseline using a repeated measures analysis of variance, followed by post-hoc pairwise comparisons adjusted with the Bonferroni correction (α=0.05).
Figure 3: Overall quality of life ratings were increased in subjects with DRG stimulation. Compared to baseline, significant quality increase was achieved at the 2-week follow-up (t(22)=-6.33, p<0.001) and was sustained at the 6-month follow-up (t(16)=-4.17, p<0.001).
Figure 4: Overall disability ratings were decreased in subjects with DRG stimulation. Compared to baseline, significant disability decrease was achieved at the 6-month follow-up (t(2.12)=3.36, p<0.01).
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Figure 5: Overall total mood disturbance ratings were decreased in subjects with DRG stimulation at the 6-month follow-up, but were not statistically different (t(16)=1.82, p=0.08).
Figure 6: Overall subject satisfaction ratings with pain relief and the therapy in general were high at each of the follow-ups across the three dimensions measured.
This work was supported by St. Jude Medical.
NANS 2017