Does improvement towards a normal cervical sagittal configuration aid in the management of cervical myofascial pain syndrome: a 1- year randomized controlled trial

A prospective, investigator-blinded, parallel-group, randomized clinical trial was conducted at one of our university’s research departments, the trial was registered with the Clinical Trial Registry PACTR201801002968301. Cairo university institutional review board approval was obtained prior to the study and all subjects were recruited from our institutions local outpatient clinic. Patients with cervical MPS were recruited from our university’s rehabilitation clinic. Patients were recruited and treated from March 2016 to October 2017 including a 1-year of follow-up.

Participants were screened prior to inclusion for alterations in two primary cervical alignment variables: loss of the cervical lordosis and anterior head translation. As part of our University’s IRB approved protocol, each participant was only to receive initial cervical spine radiography (with no follow up spine radiography) because a primary goal of the cervical denneroll orthotic is to restore the cervical lordosis, thus participants were necessarily screened for hypo-lordosis. Participants were included if their cervical lordosis was less than 25° as measured using the intersection of two lines drawn along the posterior body margins of C2 and C7 [12]. Initial cervical radiological assessment was important to identify the cervical curve apex to determine where a subject should properly place the apex of the denneroll in their cervical spine [16, 18].

Concerning anterior head translation, the participant had to have significant anterior head translation as measured by the craniovertebral angle (CVA). If the CVA was less than 50°, then a participant was referred to the study. Our selection of 50° as a reference angle was guided by the study of Yib et al. [19]. Consecutive patients were included if they had active, palpable MTrPs on a single side or both sides of the upper trapezius muscle. Diagnosis was made according to Travell and Simons’ criteria, whereby five major and at least one minor criteria are required for clinical diagnosis [20]. The major criteria are (1) localized neck pain; (2) pain or altered sensations in expected referred pain area for given trigger point; (3) taut band within the muscle; (4) exquisite tenderness in a point along taut band; (5) restricted range of motion. The minor diagnostic criteria for MPS are (1) reproduction of the patient’s chief pain complaint by manual pressure on MTrP nodule; (2) a local twitch response; and (3) pain relief obtained by muscular treatment. Participants were excluded if any signs or symptoms of medical “red flags” were present: tumor, fracture, rheumatoid arthritis, osteoporosis, and prolonged steroid use. Additionally, subjects were excluded with previous spine surgery and any exam findings consistent with neurological diseases and vascular disorders.

An independent research assistant performed a concealed permuted block randomization using a computer-generated randomization schedule with a random block size.

Both the control group and the intervention groups received the treatment interventions including: Integrated neuromuscular inhibition technique (INIT), Ischemic Compression, Strain Counterstrain (SCS), and muscle energy technique (MET). Additionally, the participants in the intervention group received the denneroll cervical traction. The control group was treated also with a placebo treatment using a small cervical towel applied in the supine position located in the mid cervical spine as an intervention to mimic the denneroll traction time; but without applying significant extension bending of the cervical spine.

Following 30 sessions, participants were re-evaluated a minimum of 24 h after their last session and then each subject was again followed for an additional 1-year time frame with no supervised treatment. The treating therapist (F.H), for both the control and intervention groups, was un-blinded to the treatment method but the subjects and assessor (A.I.M.M. and A.A.D.) who conducted the measurements were blinded.

The participants in the intervention group additionally received the denneroll cervical extension traction (Denneroll Industries, Sydney Australia; http://​www.​denneroll.​com) following previously published protocols [18, 21]. The patients were instructed to lie supine and keep their legs extended. Based on the apex of each participant’s cervical curvature on the initial radiograph, the therapist positioned the apex of the denneroll in one of two regions (mid cervical placement or lower cervical placement). The duration of the traction session started at 2–3 min and increased 1 min per session until reaching the goal of 20 min, the traction was repeated three times per week for 10 weeks. See Fig. 1.

The treating therapist first identified the TrPs to be treated within the upper trapezius muscle. The practitioner evaluated the fibers of the upper trapezius, making note of any active TrPs, by firmly pinching using the thumb and the forefinger. Ischemic compression was applied by placing the thumb and index finger over the active TrP. The therapist applied slow, increasing levels of sustained pressure to the area until a relaxation of the tissue barrier was felt. Following a release of pressure, the therapist again applied increased pressure until a new barrier was felt. This process was repeated until the patient indicated the area was no longer tender or until 90 s had elapsed; whichever came first. All identified TrPs were treated in the above manner per generally accepted methodology reported in the literature [6‐8].

Here, moderate pressure was applied by the therapist to the identified MTrP while each patient rated their level of pain on a scale from 1 to 10. Once the patient’s pain was reproduced, the therapist maintained pressure over the active MTrP and located a position that eased the patient’s perception of pain. This position of ease was generally identified as positioning the affected muscle in a shortened/relaxed state; where a reduction in pain intensity of 70% was indicated by the patient. Once identified, the position of ease was held for 20–30 s and this was repeated for three to five repetitions by the therapist; similar to other generally accepted methodology reported in the literature [6‐8].

Following SCS, the participants received MET applied to the affected upper trapezius. Here, an isometric contraction was held for 7–10 s and was followed by further cervical spine contralateral side bending, flexion, and ipsilateral rotation to maintain and increase the soft tissue stretch as the muscle belly relaxes. The MET stretch position was repeated three to five times per treatment session and was maintained for 30 s. This protocol is similar to other generally accepted methodology reported in the literature [6‐8].

All the participant received the treatment by the same physiotherapist, who had 15 years of experience in manual therapy.

Participants were advised to perform a home exercise program once daily. The program included strengthening exercises for scapular retractors, deep cervical flexors, and neck extensors. This protocol has been previously reported [18, 21]. The participants were instructed to practice the same home exercise program at least twice a week during the 1 year follow up period. During the follow up period, participants were followed up by telephone interviews every 3 months.

The participants underwent a series of assessments at three time intervals: prior to treatment, after 10 weeks of intensive treatment, and at 1 year of follow-up. The order of measurements was the same for all participants.

Descriptive statistics were calculated including mean ± standard deviation (SD) for age, height and weight. The outcome measures of NDI, pain intensity, algometric score, CROM, CV angle and SH angle were measured using repeated measures one-way analysis of variances (ANOVA) to compare measurements made before treatment, after the 10 weeks of treatment, and at 1-year follow up. Tukey’s post-hoc multiple comparisons was implemented when necessary. The baseline score for outcomes were used as covariates in a one-way analysis of covariance (ANCOVA) when baseline differences are substantial enough to influence the study outcomes. We considered a mean difference of more than 10.5 points on the NDI as a MCID. Effect sizes measured using Cohen’s d were calculated to examine the average impact of the intervention [27]. According to the method of Cohen, d ≈ 0.2 indicates a small effect and negligible clinical importance, d ≈ 0.5 indicates a medium effect and moderate clinical importance and d ≈ 0.8 indicates a large effect and high clinical importance [24]. For all statistical tests the level of significance was set at p < 0.05. Correlations (Pearson’s r) were used to examine the relationships between the amount of changes in CV and SH (in the study group) and the amount of change in NDI, pain intensity, ROM, and pressure algometry.

A sample size of 100 patients provided a 90% power of detecting minimal clinically important change (MCIC) on the Neck Disability Index (NDI) of 10.5 points (scale range 0–50. To account for possible participant drop-outs, the sample size was increased by 20% in each group.

Missing values were addressed by using multiple regression models. Model parameters were estimated with multiple regression applied to each imputed data set separately. These estimates and their standard errors were combined into one overall estimate using Rubin’s rules.

The amount of change in the CV angle (anterior head translation) at baseline vs. 10 weeks in the intervention group receiving the denneroll significantly correlated with the amount of change in NDI (p<0.032), pain intensity (p<0.05), pressure algometry (p<0.033) and all ROM measures. Whereas, the amount of change in the SH angle at baseline vs. 10 weeks in the intervention group correlated only with pain intensity (p<0.015), and algometry (p<0.012). The significant correlations were maintained at 1-year follow up with no significant differences in the findings from 10-weeks to 1-year indicating stability. Table 5 presents this data.

It is interesting that the application of an integrated neuromuscular inhibition technique alone or in conjunction with an intervention program for forward head posture reduction (denneroll orthotic) seem roughly equally successful in improving neck disability status after 10 weeks of treatment. However, our 1-year follow up data revealed a significant decline in the neck disability index for the control group. The temporal improvement in the control group may be attributed to the strong association between pain relief in both groups and functional status. However, over time, the continuous increased and / or asymmetrical loading from forward head posture may be the possible explanation for the decline in functional disability status for the control group at 12 months follow up. This concept of biomechanical dysfunction resulting from anterior head translation is supported by predictions from experimental and biomechanical spine-posture modeling studies [15, 19, 32, 33] as well as from post-surgical outcomes [34, 35] and large scale cross-sectional investigations [36].

Specifically, Tang et al. [34] identified that anterior translation distance of C2 relative to C7 (termed the SVA) on lateral cervical radiographs positively correlated with the neck disability index in 113 patients receiving posterior cervical spine fusions. Similar results were identified in a prospective sample of 49 patients by Roguski et al. [35]. In a large cross sectional analysis of 656 subjects, Oe et al. [36] identified strong correlations between activities of daily living on the EuroQOL questionnaire and the C2-C7 SVA. These three studies [34‐36] are supported by the results of the current investigation where we identified a statistically significant correlation between our experimental groups improvement in their anterior head translation (CV angle) and their consequent improvement in NDI 10-weeks post treatment and at long term follow up.

Overall, our findings revealed a significant and stable decrease in pain intensity for the study group. This long lasting improvement of pain for the study group seems attributable to the restoration of normal posture. It is generally accepted that spinal function is directly related to spinal structure. Abnormal posture elicits abnormal stresses and strains in many structures, including bones, intervertebral discs, facet joints, musculotendinous tissues, and neural elements [13, 27, 32, 33], that can be considered as a predisposing factor for pain from an alteration in mechanical loading. Of interest, in FHP, reciprocal postural compensation was observed in the upper and lower cervical spine to maintain horizontal gaze. FHP caused flexion in the lower segments and extension in the atlanto-occipital and atlantoaxial segments. The transition between flexion and extension occurred in the C2–C4 region. These compensations have implications towards increased abnormal stresses and strains [37]. Thus, restoring the normal sagittal configuration is likely to minimize the abnormal stresses.

This mechanical relationship between prolonged abnormal postures and MPS has previously been identified in different studies [9, 10]. However, few studies have directly evaluated the relationship between forward head posture and MPS in neck and shoulder. Sun et al., examined the correlation between the presence of MPS and abnormal cervical sagittal alignment concluding that “there was no relationship between the forward head position and the presence, location, and number of trigger points” [38]. While Penas et al., highlighted the positive relationship between forward head posture and the presence of active trigger points [39].

The discrepancy and conflict regarding the relationship between abnormal forward head posture with MPS identified by earlier authors cannot be directly compared with our current study because earlier studies are cross-sectional correlation studies without an ability to ascribe cause and effect. In the current study, the significant correlations between the amount of change in the CV angle in the intervention group and neck disability, pain intensity, and algometry outcomes indicates that forward head posture reduction improves the outcomes of MPS.

Concerning the pain level outcomes in the control group, the temporal reduction of pain may be attributed to short term effects of integrated neuromuscular inhibition technique. For example, Hu et al. [40] reported that pain reduction, improvement of MTrP sensitivity, and increase in ROM after various modalities for cervical myofascial pain and trigger-point sensitivity may not be maintained long term. Similarly, the systematic review of Vernon and Schneider [41] provides moderately strong evidence to support the use of some manual therapies in the immediate relief of TrP tenderness. However, only limited evidence to support the use of manual therapies over longer courses of treatments in the management of TrPs and MPS was found.

One might speculate that the improvement of ROM is attributed to a decrease of pain intensity. However, the significant differences between our study and control groups at the two measurement intervals favoring the study group indicate that the loss in ROM is not or not only driven by the presence of myofascial pain [34, 42]. Other factors associated with restricted ROM besides increased muscle tension and pain need considered. Mechanically though, forward head translation alters the anatomic alignment of the cervical spine joints in the sagittal plane, alters the lever arms of the cervical spine muscles and thus this is the most plausible explanation for altered cervical spine ROM [35]. This statement is further supported by the significant correlation between the amount of change in the CV angle in the intervention group and all ROM outcomes. The current study results are logical and agree with those of four other studies [35, 36, 43, 44], each of which investigated the association between forward head and cervical ROM.

The current study has some potential limitations. First, our study lacked blinding of participants and treatment providers. Due to the nature of the interventions, it was not be possible to blind participants and treatment providers to the interventions provided. Second, we used a sample of convenience from 1 clinic; which may not be representative of the entire population of patients with CMCPS. Additionally, we chose selective but relevant patient outcome measures (NDI, pain scale, pain pressure thresholds, range of motion) to identify if changes in sagittal plane posture deviations are related to CMCPS improvement. It is possible that other measures of CMCPS outcomes would have different relationships (greater or less improved) with posture alignment changes and that different interventions than those tested herein may improve patients with CMCPS more considerably.

Third, although the correlations identified between our postural measures and patient outcomes were statistically significant, they would be classified in the moderate range. This indicates that there are other variables, not accounted for in the current study design, which have determining effects on neck disability, pain, and range of motion outcomes. Along this line, we were unable to obtain follow-up lateral cervical radiographs. Thus, we do not if know the cervical lordosis was improved in the experimental group receiving the denneroll and if this may have added any significance to the correlation to patient outcomes.

Within these limitations, the unique contribution of this study is that it evaluated the independent effect of structural rehabilitation of the cervical spine sagittal posture on the short and long term severity of the signs and symptoms associated with CMCPS; which to our knowledge has not been previously reported. A major strength of the present study is the information as to how long pain relief lasted after treatment; up to 1-year. Whereas additional post-treatment measurements with longer than a 1-year interval might have identified a waning effectiveness of treatment.