Evaluation of peripheral nerve stimulation as an alternative to radiofrequency ablation for facet joint pain

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Project Summary It is estimated that 15% to 40% of chronic back pain cases involve the facet joints. Radiofrequency ablation (RFA) of the medial branch nerve is a widely used therapeutic intervention that is very effective in reducing facet joint pain. However, the medial branch nerve also provides motor signals to the multifidus muscle. Therefore, an unavoidable consequence of RFA is denervation of the multifidus. The multifidus muscle spans 2 to 4 spine levels, contributing significantly to the active, segmental stability of the spine. Recent reports have shown short- term adverse effects on the multifidus muscle following RFA, including multifidus atrophy and increased fat infiltration. Multifidus dysfunction causes abnormal loading and deformations of the intervertebral disc, leading to accelerated disc degeneration at the treated level. Patients also have 2 to 5 times increased risk of developing stenosis and other degenerative spine conditions or receiving a spine fusion in the 5 to 10 years after RFA, compared to other low-back pain patients. Therefore, although RFA is beneficial in the short term, it may predispose patients to other mechanisms of back pain in the future. A recently approved treatment for facet joint pain is peripheral nerve stimulation (PNS) of the medial branch. In this treatment, 1 or 2 fine‐wire leads are implanted near the medial nerve and connected to a wearable electrical stimulator. The system enables continuous delivery of electrical stimulation to the medial nerves for 40 days. After this period, the wires are removed. A recent study showed pain reduction of 70% lasting for up to 1 year, which is comparable to RFA for the medial nerve. However, the effect of PNS on the function of the multifidus muscle is known. Since the medial nerve is not damaged, it may be possible that motors signals still activate the multifidus preserving part or all its functionality. If the multifidus retains it functionality after PNS, the adverse effects observed after RFA could also be avoided. Therefore, the objective of this randomized clinical trial is to compare clinical outcomes and adverse biomechanical effects between RFA and PNS for facet joint pain. The study is divided in two aims. Aim 1 is to compare clinical and performance outcomes between RFA and PNS. Aim 2 is to quantify and compare biomechanical effects of RFA and PNS. Multifidus-sparing treatments for facet joint pain are of great interest. The multifidus muscle plays an important role in spine biomechanics. Consequently, multifidus denervation can lead to other mechanisms of spine degeneration and back pain. PNS is a promising alternative to RFA from the clinical point of view. This study will not only compare clinical outcomes between RFA and PNS, but also look at potential adverse effects in terms of spine biomechanics. If PNS doesn’t affect the multifidus function or increases the risk of spine degeneration, it can greatly change the current approach for treatment of facet joint pain.