Background Treatment of active myofascial trigger points includes both invasive and non-invasive techniques.
Objectives To compare the effects of upper trapezius trigger point dry needling (DN) and strain–counterstrain (SCS) techniques versus sham SCS.
Study design Randomised controlled trial.
Method 34 study subjects with active trigger points were randomly assigned to one of three treatment groups, and received either three sessions of DN (n=12), six sessions of SCS (n=10), or sham SCS (n=12) over a 3-week period. Subjective pain response and subjects’ own ratings of perceived disability were measured.
Results The analysis of variance mixed model showed a significant time effect for pain (p<0.001), elicited pain (p<0.001), pain pressure threshold (p<0.01), and neck disability index (p=0.016). Pain at rest decreased in all groups, as follows: DN 18.5 mm (95% CI 4.3 to 32.7 mm); SCS 28.3 mm (95% CI 12.4 to 44.1 mm); sham SCS 21.9 mm (95% CI 3.5 to 40.1 mm). Reductions in disability score (points) were significant in the SCS group (5.5, 95% CI 1.6 to 9.4) but not in the DN (1.4, 95% CI −4.9 to 2.1) or sham SCS (1.8, 95% CI −6.4 to 2.7) groups. There was no significant group×time interaction effect for any variables studied.
Conclusions There were no differences between the sham SCS, SCS, and DN groups in any of the outcome measures. DN relieved pain after fewer sessions than SCS and sham SCS, and thus may be a more efficient technique. Future studies should include a larger sample size.
Trial registration number NCT01290653.
- MYOFASCIAL PAIN
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According to the International Association for the Study of Pain, neck pain is one of the most common causes of absence from work.1 It has been suggested that myofascial trigger points (MTP) may be present in patients with insidious mechanical neck pain of musculoskeletal aetiology.2
MTPs are focal, discrete and hyper-irritable areas usually located over taut bands and identified using the clinician's palpation skills.3 MTPs located on the upper trapezius muscle are active with the greatest frequency.4
Treatment options for active MTPs include both invasive techniques, for example, dry needling (DN), and non-invasive techniques, for example, strain–counterstrain (SCS) or Jones technique. The physiological mechanism underlying SCS is unknown although Perreault et al5 have hypothesised that inhibition of muscle tone occurs through the stimulation of the Golgi tendon organ of the target muscle by physical approximation of muscular origin and insertion. This technique was originally described by Jones in 19816 with soft tissue structures responding to light palpation while achieving pain reduction in target muscles.
There is limited evidence regarding the effectiveness of SCS. Table 1 summarises the main characteristics of previous studies of SCS or DN. It is not known if the benefits of DN outweigh SCS. Furthermore, no previous study has directly compared the effectiveness and efficiency of SCS and DN techniques.
The primary aim of this study was to compare the immediate effects of DN and SCS techniques on pain perception and neck disability scores in subjects with symptomatic MTPs of the upper trapezius muscles. The secondary aim was to compare the efficiency of the two techniques, since manual techniques are applied more often than DN in clinical practice.
This was a double blind, randomised controlled trial (RCT). Six postgraduate programme physical therapists (PTs) were equipped to perform specific techniques and measures, and were extensively trained together before the study to achieve good reliability.11 PTs implementing the interventions were independent of those assessing the outcomes: two were assigned to DN treatment, three to SCS and sham treatment, and one to evaluate outcomes, blinded to group allocation. Study subjects were randomly assigned to different groups using blocked randomisation by gender and age (http://www.randomization.com) and the allocation was concealed. One of the researchers, who was not involved in either the baseline examination or the treatment, informed the therapist (blind to baseline evaluation) who treated the patients according to their group assignment.
A sample of participants suffering from neck pain was recruited from February to July 2011. Participation for this study was strictly voluntary and informed consent was obtained. The presence of active symptomatic MTPs in the upper trapezius was the main inclusion criteria (see below for detailed explanation of MTP localisation).
Exclusion criteria included a medical diagnosis of fibromyalgia, spinal radicular findings, blood coagulation disorders, chronic pain syndrome, cancer, allergies, aversion to needles, history of cervical spine or shoulder surgery within the preceding 3 years, use of anticoagulants, opioids or antiepileptic medications, daily alcohol intake over 27.4 g for men or 13.7 g for women,12 and pregnancy.
Subjects for this study agreed to participate willingly and without reservations. The study was approved by the CEU Cardenal Herrera University Ethical Committee and was also prospectively registered in the US National Instiutes of Health clinical trials registry at https://clinicaltrials.gov/ct2/show/NCT01290653.
A blinded investigator was assigned to collect the following outcome data at baseline and 3 weeks post-intervention.
Neck disability index
Study subjects were instructed to complete the Spanish version of the neck disability index (NDI) questionnaire to assess their own perceived level of disability as a result of neck pain.13 The maximal NDI score is 50 points. The minimal detectable change calculated for the NDI is 7.5 points.14
Pain intensity under basal conditions
Pressure pain threshold
Pressure pain threshold (PPT) is the amount of direct pressure needed to elicit a pain response on a selected area.17 An analogue algometer (Wagner, FDK 20; Wagner Instruments, Greenwich, Connecticut, USA), which has been shown to be reliable at quantifying pain threshold when applying direct pressure to MTPs, was used to quantify pain threshold.18–20
Symptomatic MTPs were located according to referred pain patterns.3 To elicit referred pain, study subjects were placed on a treatment table in a prone position. Investigators used their first, second and third digits in a pincer grip to locate tender points over taut bands. Investigators confirmed the presence of symptomatic MTPs by requesting a sub-maximal upper trapezius isometric contraction from the study subject and, immediately afterwards, applying a sub-maximal stretch on the subject's upper trapezius muscle. Although not essential, this was used by investigators in this study to confirm the presence of symptomatic MTPs since isometric contraction and stretch of muscles containing MTPs have been found to trigger pain responses.21 Gerwin and Sciotti previously reported good inter-examiner reliability in identifying taut bands, MTPs and referred pain.11 ,22 Investigators located an MTP in the left and right upper trapezius muscles, and chose the one with the lowest pain threshold to pressure.
Once an MTP was located, the algometer was used to measure the PPT. Progressive pressure at a rate of 1 kg/s was applied. Study subjects were asked to indicate when pain was elicited. The mean values from three measurements (kPa) were recorded. The minimal detectable change calculated for the PPT is 14.4 N/cm2 (0.014 kPa).23 All investigators were trained in the location of MTPs and use of the algometer before the study's inception.
Investigators assessed subjective pain response to controlled pressure over an active MTP using an algometer and VAS. Progressive pressure up to 4.0 kg/cm2 for women and 5.5 kg/cm2 for men was applied over the target MTP.5 Study subjects were instructed to indicate the degree of pain elicited by the application of controlled pressure by the investigator over an active MTP using the VAS.
Study subjects underwent twice weekly sessions of SCS and sham SCS or once weekly sessions of DN over a 3-week period. During treatment, study subjects were placed in a prone position with their arms alongside their bodies.
Stainless steel acupuncture needles (0.25 mm diameter, 25 mm length. Suzhou Tianxie Acupuncture Instruments Co. Agu-punt, Barcelona, Spain) were used. The surrounding soft tissue was handled using a pincer technique and the tissues were compressed to ensure optimal target tissue response. A quick ‘in and out’ technique was preferred to ensure an upper trapezius local twitch response and to promote effectiveness.3 ,24 ,25 Needling at the specific MTP was continued until the local twitch response was exhausted.24 Study subjects were instructed to perform eight repetitions of active shoulder abduction and shoulder shrugging after the needling technique was completed. Finally, investigators applied a passive upper trapezius stretch, as tolerated by the subject.
Patients were asked to report any adverse events that they experienced. In this study, an adverse event was defined as a sequela of medium-term duration with any symptom perceived as unacceptable to the patient and requiring further treatment.26
Investigators placed the selected upper trapezius muscle in a shortened position for 90 s5 and the subject's cervical spine in lateralisation ipsilateral to and rotation contralateral to the symptomatic MTP. Once palpation of the selected MTP no longer elicited a pain response, investigators passively maintained that position for 90 s.
Sham SCS technique
No therapeutic intervention was intended for this group. Study subjects were placed in a supine position while an MTP was located on the subject's upper trapezius muscle. Investigators were careful to only apply slight digital pressure below the pain threshold over the selected MTP. Gentle, slow lateral and circular digital motions were performed over the MTP over 90 s.5 Pain response was not elicited.
Sample size determination
The sample size was calculated using http://www.openepi.com. It was estimated that 11 subjects per group would be required to detect a between-group difference (DN vs SCS) in the PPT of 69 kPa, assuming a standard deviation of 49 kPa (data derived from a previous study comparing DN and a manual therapy technique10) at a two-tailed α level of 0.05 and 90% power.
The three intervention groups were compared using an analysis of variance (ANOVA) mixed model for repeated variables and Bonferroni post-hoc test. Confidence levels were set at 95%. Data were analysed with the Statistical Package for the Social Sciences (SPSS) V.18.0 (SPSS Inc, Chicago, Illinois, USA).
A total of 34 subjects were accepted for this study (table 2 and figure 1). Despite having aversion to needles as an exclusion criteria, two participants randomised to the DN group withdrew from the study because they did not want to be dry needled.
There were no significant differences in any of the subject demographics, including compensation claims at work or outcome measures between the groups at baseline. Post-intervention, the results of the mixed ANOVA revealed no differences between the three groups for any of the variables studied (p=0.412, p=0.261, p=0.771, and p=0.739 for VAS, elicited VAS, PPT, and NDI, respectively; table 3). Nevertheless, a significant time effect was observed for VAS, elicited VAS, PPT, and NDI (baseline vs post intervention: p<0.001, p<0.001, p<0.01, and p=0.016, respectively). There was no significant group×time interaction effect for any of the variables studied.
Levels of pain, measured by VAS, decreased in all groups (DN 18.5 mm, 95% CI 4.3 to 32.7 mm; SCS 28.3 mm, 95% CI 12.4 to 44.1 mm; sham SCS 21.9 mm, 95% CI 3.5 to 40.1 mm). The decrease in evoked pain was 19 mm (95% CI 3.7 to 34.3 mm) in the SCS group, 24.3 mm (95% CI 6.7 to 41.9 mm) in the sham SCS group, and 11.9 mm (95% CI −1.7 to 25.5 mm) in the DN group, respectively. NDI scores were significantly reduced by 5.5 (95% CI 1.6 to 9.4) in the SCS group but did not change significantly in the sham SCS or DN groups (1.8 (95% CI −6.4 to 2.7) and 1.4 (95% CI −4.9 to 2.1), respectively). Moreover, there were no significant differences between the three groups in the change in VAS, evoked pain or NDI scores (p>0.05).
To the best of our knowledge this is the first rigorous study to have compared the effects of DN and SCS.
Our results suggest that the DN and SCS interventions decrease pain response, in agreement with previous reports,5 ,8–10 although no significant differences between groups were found, including comparisons against the sham group. This suggests that the manual contact associated with the sham technique may have had a non-specific therapeutic effect on MTP pain. There were no statistically significant differences in the magnitude of pain improvement following real or sham SCS herein, which is consistent with previous studies of SCS. A single session of both real and sham SCS in patients with upper trapezius tightness resulted in an improvement in pain at rest.5 Conversely, neither sham nor real SCS in patients with tender points in the low back significantly affected pain levels.7 Previous studies comparing the effect of a single session of DN in the upper trapezius versus control are consistent with our results, with a significant improvement of pain immediately after treatment of 1.9 cm on an 11-point numeric pain rating scale.9 However, we did not replicate the levels of improvement seen after applying two sessions of DN (4.3 cm) in patients with chronic mechanical pain,10 or after three sessions of trigger point acupuncture in patients with chronic pain (1.9–6.7 cm).8 Furthermore, the significant differences in pain at rest and elicited pain that were achieved were not clinically relevant (<3.3 cm on the VAS score).27
At present, the mechanism by which SCS and DN cause an improvement of pain at rest and evoked pain is under debate. The gate control theory could explain how inhibitory controls modulate the sensory relay system at the level of the spinal cord.28 Peripheral sensitisation is the process by which nociceptive nerve endings exhibit an enhanced response to substances released when pain persists for a few days.29 Central sensitisation is defined as an augmentation of the responsiveness of central neurons to input from nociceptive endings.29 Central sensitisation can change, distort or amplify nociceptive information in a manner that no longer directly reflects the specific quality and quantity of peripheral noxious stimuli but rather the particular functional states of circuits in the central nervous system (CNS). C fibres carry nociceptive information, but mechanical allodynia is transferred to the CNS by low threshold Aβ myelinated fibres. Sustained nociceptive stimulation of MTPs could induce a widespread central sensitisation response since MTPs are peripheral sources of persistent nociceptive input, which can excite muscle nociceptors, and thereby induce neuroplastic changes in the spinal dorsal horn and brainstem. Therefore both SCS and DN may reverse neuropathic changes by removing a constant and intense nociceptive source.30 Since all groups received palpation of MTPs (including the sham group) it is possible that this resulted in reduced pain, as diagnostic palpation per se may raise trigger point pain threshold and result in pain reduction.
PPT improved over time in all groups, but the magnitude was small. These results are in agreement with a study on the effect of SCS on tender points in the low back that showed a mean increase of 98.1 kPa in an SCS group, 39.2 kPa in a sham SCS group, and 29.4 kPa in a control group.7 It was suggested that some of the observed increase in local PPT may have been due to the manual pressure component of the measurement procedures in all three groups. Considering dosage, it should be noted that we only applied each manoeuvre for 90 s5 compared to 6 min per session in the aforementioned study.7 Inherent differences in measurement location (zygapophyseal joint vs spinous process) makes direct comparison questionable, but previous research shows that one9 or two10 sessions of DN on the upper trapezius immediately resulted in a significant increase in PPT. Although we did not achieve a clinically important change in PPT (1.2 kg/cm2 or 117.7 kPa)31 in this study, it should be noted that mean pain levels in our sample were similar to those of neck pain patients recruited from physiotherapy clinics.31 Furthermore, participants in the present study had lower pain at baseline compared with previous DN studies (table 1).
Our study suggests that DN is a safe technique with no major side effects. None of the subjects allocated to DN abandoned treatment due to aggravation of symptoms, which is in agreement with previous DN studies.9 ,10 ,32 By contrast, two patients allocated to sham SCS and one to real SCS discontinued treatment for this very reason. Unfortunately, two subjects assigned to the DN group dropped out due to aversion to needles, despite the initial consent procedure having incorporated this as a specific exclusion criterion.
NDI significantly decreased in the SCS group but not in the DN or sham SCS groups in this study, which contrasts somewhat with previous studies involving needling. For example, two sessions of DN over the upper trapezius trigger point decreased self-perceived disability,10 and three sessions of trigger point acupuncture significantly decreased NDI from 13 to 3.9 points.8 It is notable that, even in the SCS group, we did not achieve an improvement of 7.5 points, which is reported to be the minimal detectable change.14 ,33 Thus the changes in NDI observed in the SCS group herein might represent a type 1 error.
There are a number of limitations to this study that should be considered when designing future trials. Sample size calculation was based on a previous study comparing PPT between manual therapy and DN,10 but the measurement location was the C7 spinous process. We did not reveal any differences of this size (d=1.4) and, given that our sample size was very small, we were ultimately underpowered to detect more modest effects. We also lacked an untreated control group, and follow-up was not included in the study design. The disability level of the participants was mild to slight according to the NDI (<24%), which may have limited the therapeutic effect that could realistically be achieved. Intake of non-steroidal anti-inflammatory drugs and muscle relaxants during the study could not be prevented and may have altered the pain threshold in some of the study subjects. Furthermore, this study did not take into account the MTPs located at the lower trapezius, a muscle that has been shown to be important in the treatment of neck pain, and the length of the needle may have been too short to dry needle some of the MTPs effectively. DN was not applied alone, since this group included shoulder shrugs and abduction as aftercare. Outcome data were not available for dropouts (figure 1), and this could be a source of potential attrition bias, particularly in the sham SCS group (where attrition was 50%).
It must also be acknowledged that the SCS technique may not have been adequately applied in all cases since the investigators did not test if the technique achieved a two-thirds reduction in tenderness at tender points monitored by a verbal scale.7 Finally, it is possible that the duration of the intervention (90 s) was too short to achieve beneficial effects, as other investigators have applied the technique for 6 min.7
In summary, there were no differences between the SCS, sham SCS and DN groups in any of the outcome measures. SCS and DN techniques appeared equally effective at lowering MTP pain response in the subjects during a short-term post-interventional period. Arguably DN may be more efficient, since a similar degree of pain relief was achieved in fewer sessions than SCS and sham SCS. Reduced pain scores in subjects assigned to the sham SCS intervention group could be explained by the manual contact effect. Since our statistical power was limited, future studies are required to confirm where there are differences between the techniques studied.
We are grateful to Pablo Fuster-Aránega, Nuria Ferrer-Valls and Javier Gómez-Morcillo for their work during the implementation of this study. We would like to thank the managers of the 2010–2011 edition of the Master en Atención Fisioterápica en Actividad Física y Deporte, Universidad CEU Cardenal Herrera for the support to undertake this research, and also the volunteers that participated in the study.
Jia Li, SW and HT contributed equally.
Contributors ES-O, SP-V, LM-P, RV-M and JAP-T all made substantial contributions to the conception/design of the work and acquisition, analysis and/or interpretation of the data. All authors drafted and/or revised the work critically for important intellectual content, approved the final version for publication, and agreed to be accountable for all aspects of the work.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Institutional Review Board: The scientific and clinical basis for this study were reviewed and approved by the CEU Cardenal Herrera University Ethical Committee.
Public trials registry Study registered in the United States NHS Clinical Trials database as Dry Needling Versus Strain-counterstrain on the Upper Trapezius (DNJ) code NCT01290653.
Provenance and peer review Not commissioned; externally peer reviewed.
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