Abstract
In the rapidly evolving field of spinal cord stimulation (SCS), measures of treatment effects are needed to help understand the benefits of new therapies. The present article elaborates the number needed to treat (NNT) concept and applies it to the SCS field. We reviewed the basic theory of the NNT, its calculation method, and its application to historical controlled trials of SCS. We searched the literature for controlled studies with ≥20 implanted SCS patients with chronic axial back and/or leg pain followed for ≥3 months and a reported responder rate defined as ≥50% pain relief. Relevant data necessary to estimate the NNT were extracted from the included articles. In total, 12 of 1616 records were eligible for inclusion. The records reported 10 clinical studies, including 7 randomized controlled trials, 2 randomized crossover trials, and 1 controlled cohort study. The studies investigated traditional SCS and more recently developed SCS modalities, including 10 kHz SCS. In conclusion, the NNT estimate may help SCS stakeholders better understand the effect size difference between compared treatments; however, interpretation of any NNT should take into account its full context. In addition, comparisons across trials of different therapies should be avoided since they are prone to interpretation biases.
Highlights
Chronic pain is a common problem among adults, with prevalence studies suggesting that one in five are affected [1,2]
We provide an overview of the definition, calculation, and interpretation of the number needed to treat (NNT), as well as an evaluation of the metric for historical controlled trials of the therapy in chronic axial back and/or leg pain patients
Our analysis of historical controlled trials of Spinal cord stimulation (SCS) suggests that the NNT concept can be applied in this medical discipline and may support clinical decision-making, costeffectiveness studies, and healthcare policymaking
Summary
Chronic pain is a common problem among adults, with prevalence studies suggesting that one in five are affected [1,2]. Despite considerable advances in our understanding, diagnosis, and management of pain, many patients report inadequate pain control [2,3,4,5]. Effective pain management strategies are needed to address unrelieved pain among this population. Spinal cord stimulation (SCS) has been used for over 50 years to treat various refractory chronic pain syndromes. During SCS, an implanted device delivers low-level electrical pulses to the spinal cord via an array of electrodes placed into the epidural space either percutaneously or surgically via laminotomy or laminectomy. In traditional SCS (t-SCS), perceptible paresthesia is elicited over the area of pain by individual pulses delivered continuously at a fixed low frequency (40–50 Hz), pulse width (150–500 μs), and amplitude [6]
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