Nerve root block versus surgery (NERVES) for the treatment of radicular pain secondary to a prolapsed intervertebral disc herniation: study protocol for a multi-centre randomised controlled trial

Sciatica is broadly defined as leg pain in the distribution of a lumbosacral nerve root [1]. It is a common condition affecting over 3% of the population at any one time and over 90% of sciatica is due to a prolapsed intervertebral disc (PID) [2]. Patients affected are typically young, working adults and it can be helpful to consider three categories of sciatica: (1) acute sciatica – lasts less than 6 weeks and may be self-limiting with little or no impact on the patient’s ability to perform usual activities; (2) chronic sciatica – persists beyond 6 weeks and has a tremendous impact upon the patient’s working ability and (3) resistant sciatica – persists beyond 12 months [3]. Although the duration of pain may vary considerably, and the natural history of sciatica is favourable within 1 year, many patients have pain that persists beyond 6 weeks which could have considerable impact upon the employment market and patients’ lives [4]. It is generally accepted that pain persisting beyond 6 weeks is unlikely to get better imminently and requires further investigation and treatment [1‐4]. There is no current accepted treatment paradigm for sciatica within the UK [1]. Treatment options are largely uproven but include analgesic drugs of various categories including antiepileptics and antidepressants, injections of drug combinations into the spine and surgical techniques to remove the prolapsed disc [1] Recent evidence has suggested that the commonly used neuromodulator drug pregabalin may not have a strong benefit in the treatment of sciatica in the community [5]. Epidural steroid injections (ESI) are another treatment modality for sciatica and involve the administration of a mixture of local anaesthetic and steroid into the spine via one of three main routes; through the base of the spine (caudal epidural), through the back of the spine (inter-laminar) or through the nerve tunnel directly adjacent to the prolapsed disc (transforaminal epidural steroid injection (TFESI) [6]. Randomised controlled trials (RCTs) have looked at ESI for acute sciatica but these have not included comparisons between TFESI and inter-laminar ESI [7‐10]. However, prospective and case control studies have compared these and demonstrated a superior efficacy of TFESI [6‐9]. One recent study of TFESI ([9]; n = 238) reported that 65% of injections were effective at follow-up greater than 6 months (based on patient-reported measures) suggesting that the administration of drug closer to the disc prolapse may improve efficacy when compared to other methods of administration. Moreover, efficacy is improved if symptom duration is less than 6 months prior to injection [9]. Only one trial [10]; n = 100) has directly compared inter-laminar ESI to surgery for sciatica secondary to PID and suggested that ESI could prevent 50% of surgical interventions. Although this specific use of steroid is outside the marketing authorisation (off-label) it is commonly used and a widely accepted treatment for sciatica. Of the surgical techniques, microdiscectomy to remove the prolapsed disc is considered the ‘gold standard’ with reported success rates of 90% [11]. As sciatica has a good natural history there is potential that the treatment administered in the form of injection may render surgery as excessive, but results from other studies have shown that ESI only have a small short-term effect on leg pain and disability compared with placebo, and no effect in the long term [12]. These poor medium- to long-term results have given ESI poor perceived efficacy and hence they are widely ignored in the treatment of acute sciatica [13]. Perhaps because of this at the time of trial conception no care pathway in the National Health Service (NHS) suggests any particular treatment over another [1]. No direct comparison exists between surgical microdiscectomy to treat sciatica secondary to lumber disc prolapse and nerve root blocks such as TFESI. In the UK in 2010/2011 over 25,000 therapeutic ESIs were administered and over 9000 surgical procedures were performed to remove herniated lumbar disc prolapses for sciatica (HES data). The costs to the NHS in the United Kingdom (UK) are £600 per ESI and approximately £4000 for surgical microdiscectomy (which requires an average of two nights in hospital per patient) [14].

The NERVES (NErve Root block VErsus Surgery) trial is funded to compare surgical microdiscectomy to local steroid and anaesthetic administered accurately to the source of leg pain in terms against various clinical and quality of life (QOL) outcomes to determine if there should be a recommended treatment pathway for patients with sciatica secondary to a PID. Surgical microdiscectomy and TFESI will be performed as per local NHS policy. Given the cost differential between the interventions being evaluated, and the potential for differences in clinical benefit and health outcomes, an economic evaluation will be conducted alongside the trial to determine which treatment option is the best use of health-care resources.The primary objective is to compare the clinical effectiveness of TFESI and surgical microdiscectomy for sciatica secondary to PID. Secondary objectives are to compare the cost-effectiveness of TFESI and microdiscectomy for the treatment of sciatica secondary to PID and to compare QOL outcomes for both treatments.

Surgical microdiscectomy for removal of PIDs has been shown to successfully relieve symptoms in the majority of patients [6, 11]. Disadvantages of surgery are the resource implications for the NHS due to the requirement for hospitalisation and the high skill level required of the treating physician. Surgery also carries the highest level of risk of all treatments for sciatica. Injections are relatively cheap and low risk in comparison to sciatica; they are delivered as a day-case procedure and the range of treatment providers is large, ranging from radiologists to surgeons or pain physicians. There is potential that treatment administered in the form of an injection may circumvent the need for surgery. However, the true success rate of spinal injections is largely unknown and there is no evidence comparing TFESI to surgical microdiscectomy that could be used to advise one treatment pathway over another. This protocol describes the design of a RCT to evaluate the clinical effectiveness and cost-effectiveness of TFESI to surgical microdiscectomy to treat sciatica secondary to a PID. It is the first randomised trial to address this issue to date.