Effectiveness of a specific manual approach to the suboccipital region in patients with chronic mechanical neck pain and rotation deficit in the upper cervical spine: study protocol for a randomized controlled trial

A randomized, prospective, double-blind (patient and evaluator) clinical trial. The therapist cannot be blinded due to the use of manual techniques. Figure 1 shows a diagram with the different phases of the study.

The required calculation of the sample size was performed for all outcome variables, for a two-tail test, using a web application (Granmo v7.12) from the Mar Institute of Medical Research Foundation (https://​www.​imim.​es/​ofertadeserveis/​software-public/​granmo/​). The statistics needed for the calculation were determined based on three studies: the pilot study by González-Rueda et al. [16] provided statistical data about pain intensity in a similar population and with similar techniques to those used in this study, and those by Izquierdo et al. [17] and Dunning et al. [18] comparing different manual techniques in patients with chronic mechanical neck pain provided statistical data about Neck Disability Index (NDI), range of active mobility an Headache Impact Test. The highest value obtained, using an alpha risk of 0.05 and a beta risk of 0.20 with an estimated follow-up loss of 15%, was 26 subjects per group. As there will be three study groups (the Control Group, the Mobilization Group and the Pressure Group) the total sample size will be 78 subjects.

The subjects for this study will be recruited in the Sant Ildefons Rehabilitation Service in Cornellà de Llobregat (Barcelona), a public Primary Care centre of the Catalan Institut of Health. All patients referred to this service must be seen by a specialist in Physical Medicine and Rehabilitation before receiving treatment. All those diagnosed with chronic mechanical neck pain (of more than 3 months duration) and classified in Grade I or Grade II according to the classification of the Neck Pain Task Force [19] during that appointment will be referred to a physiotherapist, who will check whether they meet the other inclusion and exclusion criteria before offering them the opportunity to participate in the study.

The inclusion criteria will be: subjects diagnosed with chronic mechanical neck pain, who are over 18 years old and with a positive result in the flexion-rotation test corresponding to a rotation deficit. The flexion-rotation test (FRT) will be considered as positive if in a position of maximum cervical flexion, there is a difference of 10 degrees or more in the rotation in one direction compared to the contralateral direction, or if there is a cervical rotation of less than 32 degrees measured with the CROM [12, 20].

The exclusion criteria will be: contraindication to manual therapy, post-traumatic neck pain or red flags according to Rushton et al. [13], an inability to maintain the supine position, use of pacemakers, an inability to perform the FRT, language difficulties that hinder understanding of informed consent or completion of the questionnaires necessary for this study, and subjects with litigation or lawsuits pending.

Patients who meet all inclusion criteria and none of the exclusion criteria will be offered the opportunity to participate in the study and provided with all the relevant information verbally and in writing. They will be told that they will be randomly distributed among the study groups and that each group will be treated with different techniques, all of which are appropriate for their condition, and that the objective of the study is to determine which technique produces the best results. The patients will not be informed about which group they have been assigned to in order to maintain blinding in this regard.

If they decide to participate they will be asked to sign an informed consent form and the same physiotherapist responsible for recruitment will perform the baseline assessment.

A list of consecutive numbers (from 1 to 78) will be generated prior to recruitment, and each of these numbers will be assigned randomly to one of the three study groups (Control Group, Mobilization Group and Pressure Group) using a computer program (www.​random.​org).

Without any prior knowledge of the list generated, the physiotherapist responsible for recruitment and initial assessment will assign a consecutive number to each subject participating in the study.

The physiotherapist performing the intervention will be the only one with access to the list generated by the computer program. This physiotherapist cannot be blinded due to using manual techniques and he/she will know which group the subject has been assigned to by referring to the number assigned by the evaluator.

The concealment and blinding of the assignment will therefore be assured, since the physiotherapist performing the recruitment will not know which group the subject will be assigned to.

The physiotherapist responsible for recruitment (Master’s Degree in Orthopaedic Manual Therapy and 7 years of experience in this field) will perform all the evaluations for this study, and will remain blinded as regards the group that the subject has been assigned to at all times.

Table 1 shows the sociodemographic variables and the values that each one may have. The following variables: age, sex, duration of symptoms, work, work with lifting, work with sustained focal distance, housework, use of mouthguard, presence of dental prosthesis, visual problems, presence and frequency of headaches and analgesic and anti-inflammatory medication will be recorded at the beginning of treatment by anamnesis.

Table 2 shows the outcome variables, the evaluation period for each one and the measuring instrument used. All evaluations will be performed by a single physiotherapist, who will also be responsible for the recruitment, and who will be blinded throughout the evaluation period as regards the group assigned to each subject.

Main outcome will be the intensity of pain in the cervical region measured with a visual analog scale (VAS) from 0 to 100 mm in length, with the extremes defined as “no pain” (0) and “the worst pain imaginable” (100) and without any intermediate points. The test-retest reliability has proven to be good (ICC 0.92) [21].

Neck disability will be measured using the Neck Disability Index (NDI). This is a self-applied questionnaire consisting of 10 sections with 6 possible answers representing six progressive levels of functional disability, rated from 0 to 5, with 0 being the first level and 5 the last level of each section. The total score ranges from 0 to 50 points, with higher scores indicating greater disability. At least 8 of the 10 sections must be answered for the score to be calculated. The test-retest reliability has proven to be adequate (ICC 0.97) and it has been validated for the Spanish language [22].

The overall range of active mobility in the cervical region will be evaluated in a sitting position with the vertical back resting on the backrest of the chair [23]. Flexion, extension, right and left inclination and left and right rotation will be measured. A CROM device with good intra- and interexaminer reliability (ICC > 0.80) [24] will be used in all the measurements. Two measurements will be made for each movement, and the result will be the mean of the two measurements.

The range of active mobility in flexion and extension of the upper cervical region will be measured in a standing position with the back against a wall. The flexion-rotation test [25, 26], which has proven to have high levels of intra- and interexaminer reliability (ICC 0.98) [27] will be used to measure the range of motion in rotation in the upper cervical region. To perform the FRT, the subjects position themselves in the supine position and the evaluator passively takes the patient’s cervical spine to its maximum flexion and then rotates the head to the right and left side with the occiput resting against the evaluator abdomen. The movement stops at whichever situation occurs first, either the subject presents symptoms, or the evaluator reaches the end of the range of motion and finds a hard end feel [12]. As in the measurement of overall cervical mobility, a CROM device will be used for all the movements of the upper cervical region, and two measurements will be performed for each movement, with the result being the mean of the two measurements.

Headache intensity is measured by the validated Spanish version of the HIT-6 (Headache Impact Test) questionnaire [28]. This questionnaire consists of 6 items (intensity of pain, social functioning, role functioning, vitality, cognitive functioning and psychological disorder), which each have five response options (Never: 6 points, Rarely: 8 points, Sometimes: 10 points, Very often: 11 points, Always: 13 points), with a score range of 36-78 points. It has proven to have good test-retest reliability (ICC 0.80) [29, 30].

The patient’s rating of clinical change will be evaluated with a Global Rating of Change Scale (GROC scale) [31]. This is a scale of 15 items, of which 7 are improvement and 7 are deterioration, and with 1 central item with no clinical change. Values from the fourth item of improvement or deterioration will be considered clinically significant, values between the three item of improvement and the three item of deterioration will be considered as no clinically significant changes [32]. The test-retest reliability has proven to be good (ICC 0.90) [33].

Additionally, changes in medication (more, less or the same dose) and the presence of exacerbations and/or recurrence will be recorded by anamnesis 3 months after the treatment period. Exacerbation is considered the isolated process of increased pain which patients control themselves using the patterns learned, and exacerbations requiring further medical advice will be considered recurrences.

Intervention will be provided by a different physiotherapist (PhD, with more than 13 years of experience in the field of Orthopaedic Manual Therapy) who was the only person having the random allocation list and implemented the treatment according to the group assigned to the participant’s number by the computer program, blinded to the results of the assessment.

The three groups will receive a common protocolized treatment and additionally, the translatory dorsal glide mobilization technique (TDGM) will be applied to the Mobilization Group and the pressure maintained suboccipital inhibition technique (PMSIT) will be applied to the Pressure Group.

The data analysis will be performed after the data for the entire sample has been collected, using the SPSS Stadistic® v.20.0 software package. The significance level is established at 0.05 and the limits of the confidence interval at 95%.

A descriptive analysis of the baseline characteristics of the sample will be performed. All the quantitative variables will be analysed using the Kolmogorov-Smirnov test with Lilliefors corrections, to ascertain whether they follow a normal distribution. The initial homogeneity between the groups will be also analysed (ANOVA or Kruskal-Wallis depending of the normality of data distribution). According to the results of the homogeneity and normality analysis, parametric or non-parametric statistics will be used for the within and between-group analysis.

Within-group results will be analysed using repeated measures ANOVA (when initial homogeneity and normality of data distribution were found), Friedman test (when initial homogeneity but not normality of data distribution were found), or a linear mixed model adjusted for the baseline values when not initial homogeneity were found.

Between-group results will ve analysed using ANOVA with Bonferroni post hoc statistic (when initial homogeneity and normality of data distribution were found), Kuskall-Wallis test (when initial homogeneity but not normality of data distribution were found) or a linear mixed model adjusted for the baseline values, when not inicial homogeneity were found.

The principles of intention-to-treat analysis will be used. In the event of follow-up losses, the outcome variables that have not been recorded will be completed with the last data recorded for each of these variables (Last-Observation-Carried-Forward-Analysis).