Outcomes
This clinical study was designed to include the following general outcome measures: pain, overall improvement, back-specific functional status, well being (quality of life), and disability. The questionnaires that will be used to collect data from the participants are: visual analog scale (VAS) for pain [12], Roland Morris Disability Questionnaire (RMDQ) for effectiveness, specifically back-specific disability [12], and Euro Qol-5D questionnaire (EQ-5D) for quality of life, which is one of the most used and suitable questionnaires for QALY calculation [5]. These questionnaires were chosen by considering the major systematic reviews regarding physical and rehabilitory interventions for sub-acute and chronic non-specific LBP [2, 4, 9, 10, 12, 15]. Participants will complete the VAS at T2, T3, T4, TF1, TF2, TF3, TF4, and TF5; RMDQ at T1, T2, T3, T4, TF1, TF2, TF3, TF4, and TF5; and EQ-5D at T2, T4, TF1, TF2, and TF5.
Primary outcome
The primary outcome of the trial is represented by the clinical effectiveness of the SMATH® system versus sham therapy after 4 weeks of treatment in patients with sub-acute and chronic non-specific LBP, determined by evaluating self perceived physical function with RMDQ scores. The status of physical function in participants treated with SMATH® interventions will be compared with the status achieved in participants in the sham control arm at the end of treatment (T4) [12].
Secondary outcomes
The secondary outcomes of the trial are: 1) Effectiveness of SMATH® determined by evaluating self perceived physical function comparing RMDQ scores between end of treatment and baseline. 2) Pain perception change from baseline (T2) to end-treatment (T4), evaluated by VAS scores. 3) Quality of life at different steps of the study (T2 and T4), evaluated by EQ-5D scores (QALY). 4) Verified general feasibility of the medical device compared to sham therapy in terms of methodology, sample size, and drop-out rate, among other measures, to constitute a real pilot study and act as a possible reference for future generations of RCTs involving the medical device, conforming to the evidence-based medicine (EBM) criteria for LBP therapy [13] according to the CONSORT statement based on new methodological evidence and to the International Placebo Symposium Working Group recommendations [19].
Observational follow-up and duration of the study
Observational follow-up will start at TF1 (T4) and cover 11 months. During this period, all of the participants will come to the treatment centre to attend clinic visits one month after TF1 (TF2), 3 months after TF2 (TF3), 3 months after TF3 (TF4), and 4 months after TF4 (TF5). Figure 2 shows the design of the observational follow-up period. The estimated study duration for enrollment, execution and observational follow-up will be 18 months.
Assessment of outcomes
Four steps of participant examination are planned in this RCT (T1, T2, T3, and T4); during which, general clinical data will be collected about the persistence of LBP symptoms, previous treatment, morphological data, patient activity, blood chemistry tests, anamnesis, and eventual clinically important imaging investigations that were recently done. The effectiveness of SMATH® versus sham will be determined by evaluating self-perceived physical function with RMDQ scores at T4. The secondary outcome of SMATH® therapy effectiveness will be determined by evaluating improvements in patients' motion functionality between T2 and T4 using RMDQ scores. The evolution of pain perception during the study will be measured by VAS scores submitted by the participants at T2, T3, and T4. Quality of life for participants will be estimated by the comparing the EQ-5D questionnaires submitted at the beginning and end of treatment (T2 and T4). During the observational follow-up period all participants will be examined at TF1, TF2, TF3, TF4, and TF5 for general patient status: anamnesis, blood pressure, heart rate in beats per minute, and morphological variables (height, weight, Body Mass Index [BMI]). The RMDQ and VAS questionnaires will be given on the participants at TF1, TF2, TF3, TF4, and TF5, and EQ-5D will be given at TF1, TF2, and TF5. All of the data collected during the study and follow-up will be reported to the CRF.
Sample size calculation
Due to the difficulty of finding solid references in the literature regarding the probability of success for different arms of RCTs comparing therapy with medical devices versus sham therapy [19], some basic statistical assumptions have been made in regards to the level of inhibition technically introduced into the SMATH® active principles to obtain a sham device. The therapeutic effect induced by the sham device has been estimated to be 10% of the effect induced by the SMATH® system. Consequently, the probability of SMATH® therapy success has been fixed at 50% (P1) [2], whereas a probability of 10% (P2) has been fixed for success with sham therapy. Thus, the success difference between the two study arms (P1 - P2) is 40%. This important delta has been fixed to be statistically significant also in the case of unexpected placebo effect of sham. The false-positive risk factor α (type I error rate) has been fixed at 0.05 (5%). The probability of discovering a difference between the two study arms has been fixed at 90% (study's power). Based on the study's power, (1 - β) = 0.9, the false-negative risk factor rate β is 0.1 (10%). The value of the function f (α, β) was calculated by Geigy's tables [23]. Thus, the sample size in each arm of the study (n) should be n = 26. Drop-out has been considered to prevent having an insufficient sample at the end of the study due at the high risk of drop-out of participants in sham arm. A drop-out rate of 15% (0.15) has been estimated based on the literature concerning RCT versus sham in PRM [19]. The sample adjusting factor μ was calculated using the formula μ = 1/(1 - R)2[24–26], where R represents the drop-out rate. Therefore, μ = 1/(1 - 0.15)2 = 1.3841, and the sample size after correcting for drop-out will be:n# = nμ = 36. The sample of each group will be 36 participants for a total study group of 72 subjects.
Statistics and quality
The accuracy and completeness of the collected and registered data will be checked daily by clinical investigators to provide a suitable level of quality for the study. The external monitor will be responsible for arranging random periodic tests of quality throughout the study. In particular, controls will involve the quality and completeness of the CRFs, the treatment execution modalities, the drop-out rate, and correct respect of enrollment criteria application. Data analysis will be conducted using IBMSPSS 19 [21, 22]. The morphological and clinical status of participants will be analyzed statistically. Motion functionality, level of pain perception, and quality of life will be evaluated through statistical analysis of the questionnaire scores. Short-term results will be evaluated to elaborate VAS and RMDQ scores, and medium and long-term results will be evaluated by EQ-5D scores, which will also be used to calculate the QALY and incremental cost effectiveness ratio (ICER) index [5, 22], which is the most used and suitable index for analyzing the cost/effectiveness of PRM therapies [5]. Pain perception measured by VAS in the different phases and its severity analysis will be evaluated by analysis of variance using SPSS 19. Event incidence (SMATH® versus sham) will be estimated using Kaplan-Meier curves, which will be compared using the log-rank test. Multivariable analysis will be performed using the Cox model.
Patient information material
Correct involvement and informed participant processes are key issues for the success and credibility of the study. Clinical investigators will be responsible for informing participants and involving them in the most appropriate way. This goal will be pursued by discussing the study objectives, risks, benefits, and modalities with participants at T1. Each participant will make a decision as to whether they will participate in the study, which will have to be clearly checked by investigators and documented. In this study, clinical investigators will submit and explain to each participant the following documents: (1) signed informed consent, (2) information module, (3) authorization to use personal sensitive data based on privacy law, (4) information letter that will be delivered to the family physician, (5) the dedicated educational booklet. This booklet must be considered a part of the SMATH® treatment module.
Adverse events
Adverse events will be managed to conform with good clinical practice and actual normative rules, listed in additional file 1. All adverse events will be reported to the regulatory authority and ethics committee in accordance with applicable regulations. The report will specify the types of events, and whether they were device related or non-device related, that shall be reported and the timing for such reporting.