Topographical mapping and mechanical pain sensitivity of myofascial trigger points in the infraspinatus muscle

Objectives: To screen for the presence of latent and active myofascial trigger points (MTrPs) in patients with unilateral shoulder and arm pain and perform topographical mapping of mechanical pain sensitivity bilaterally in the infraspinatus muscles. Methods: Nineteen patients with unilateral musculoskeletal shoulder pain participated in the study. The area overlying the infraspinatus on each side was divided into 10 adjacent sub‐areas of 1cm², corresponding to the area of a pressure algometer probe. Pressure pain threshold (PPT) was measured in each sub‐area bilaterally in the infraspinatus muscles. Following PPT measurement, an acupuncture needle was inserted into each sub‐area five times in different directions in order to induce local twitch response and/or referred pain. Results: A significantly lower PPT level in the infraspinatus muscle was detected on the painful side compared with the non‐painful side (P=0.001). PPT at midfiber region of the infraspinatus muscles was lower than that at other muscle parts (P<0.05). Multiple, but not single, active MTrPs were found in the infraspinatus muscle on the painful side and there were also multiple latent MTrPs bilaterally in the infraspinatus muscles. PPT at active MTrPs was much lower than the latent MTrPs and again lower than the non‐MTrPs. Conclusions: There exists bilateral mechanical hyperalgesia in patients with unilateral shoulder pain. Further, the association of multiple active MTrPs with unilateral shoulder pain and the heterogeneity of mechanical pain sensitivity distribution suggest a crucial role of peripheral sensitization in chronic myofascial pain conditions. Additionally, the locations of MTrPs identified with dry needling correspond well to PPT topographical mapping, suggesting that dry needling and PPT topographical mapping are sensitive techniques in the identification of MTrPs.     

Short-term effect of myofascial trigger point dry-needling in patients with Adhesive Capsulitis

BackgroundAdhesive Capsulitis (AC) is a common disabling musculoskeletal pain condition of unknown etiology related to the shoulder joint. Literature reported the restricted range of motion (ROM) and pain could be the result of myofascial trigger points (MTrPs) in the muscles of the shoulder girdle. Hence, the objective of this study was to assess the short-term effectiveness of MTrP dry needling (DN) in improving ROM, pain, pressure pain threshold (PPT), and physical disability among patients having AC.MethodsIn a single group pre-post experimental study design, a total of 70 clinically diagnosed patients (both male & female, age group between 40 and 65 years) with AC were recruited from three multi-specialty hospitals. The informed consent forms were received from each patient before participating in the study. Each patient received DN for the MTrPs of shoulder girdle muscles for alternative six days. In addition to DN, each patient had received conventional physiotherapy for continuous twelve days which includes electrotherapy modalities and exercises. The pain intensity (visual analog scale), shoulder ROM (Goniometer), disability (shoulder pain and disability index) and PPT (Algometer) were the outcome measures assessed at the baseline and twelfth day of the intervention.ResultsThere was a statistically significant (p < 0.05) improvement in shoulder ROM, pain intensity, shoulder disability, and PPT at the end of the twelve days of intervention as compared to baseline assessment.ConclusionMTrPs-DN techniques may improve the pain, ROM, disability and PPT along with conventional physiotherapy management among patients with AC.     

Treatment of myofascial pain syndrome

Myofascial pain syndrome (MPS) is caused by myofascial trigger points (MTrPs) located within taut bands of skeletal muscle fibers. Treating the underlying etiologic lesion responsible for MTrP activation is the most important strategy in MPS therapy. If the underlying pathology is not given the appropriate treatment, the MTrP cannot be completely and permanently inactivated. Treatment of active MTrPs may be necessary in situations in which active MTrPs persist even after the underlying etiologic lesion has been treated appropriately. When treating the active MTrPs or their underlying pathology, conservative treatment should be given before aggressive therapy. Effective MTrP therapies include manual therapies, physical therapy modalities, dry needling, or MTrP injection. It is also important to eliminate any perpetuating factors and provide adequate education and home programs to patients so that recurrent or chronic pain can be avoided.     

Trigger Point Needling: Techniques and Outcome

In this review we provide the updates on last years' advancements in basic science, imaging methods, efficacy, and safety of dry needling of myofascial trigger points (MTrPs). The latest studies confirmed that dry needling is an effective and safe method for the treatment of MTrPs when provided by adequately trained physicians or physical therapists. Recent basic studies have confirmed that at the site of an active MTrP there are elevated levels of inflammatory mediators, known to be associated with persistent pain states and myofascial tenderness and that this local milieu changes with the occurrence of local twitch response. Two new modalities, sonoelastography and magnetic resonance elastography, were recently introduced allowing noninvasive imaging of MTrPs. MTrP dry needling, at least partially, involves supraspinal pain control via midbrain periaqueductal gray matter activation. A recent study demonstrated that distal muscle needling reduces proximal pain by means of the diffuse noxious inhibitory control. Therefore, in a patient too sensitive to be needled in the area of the primary pain source, the treatment can be initiated with distal needling.     

Management of myofascial trigger point pain

Successful management of myofascial trigger point (MTrP) pain depends on the practitioner finding all of the MTrPs from which the pain is emanating, and then deactivating them by one of several currently used methods. These include deeply applied procedures, such as an injection of a local anaesthetic into MTrPs and deep dry needling (DDN), and superficially applied ones, including an injection of saline into the skin and superficial dry needling (SDN) at MTrP sites. Reasons are given for believing that DDN should be employed in cases where there is severe muscle spasm due to an underlying radiculopathy. For all other patients SDN is the treatment of choice. Following MTrP deactivation, correction of any postural disorder likely to cause MTrP reactivation is essential, as is the need to teach the patient how to carry out appropriate muscle stretching exercises. It is also important that the practitioner excludes certain biochemical disorders.     

Post-needling soreness after myofascial trigger point dry needling: Current status and future research

Post-dry needling soreness is a common complication of myofascial trigger point (MTrP) dry needling treatment. The prevention, management and relevance of this complication remain uncertain. This paper examines the current state of knowledge and suggests directions for further studies in this area. MTrPs are hypersensitive nodules in skeletal muscles' taut bands, present in several pain conditions. Dry needling has been recommended for relieving MTrP pain. MTrP dry needling procedures have shown to be associated with post-needling soreness, which is thought to be a consequence of the neuromuscular damage, and hemorrhagic and inflammatory reaction generated by the needle. Postneedling soreness is a very frequent effect after deep dry needling, usually lasting less than 72?h. It may not be especially distressing for most patients. However, patients presenting with higher levels of post-needling soreness, not perceiving dry needling effectiveness in the first session, or not having high myofascial pain intensity before treatment, could be the most likely to find post-needling soreness more distressing, functionally limiting and to abandon treatment. Future research should assess the clinical relevance of post-needling soreness. Post-needling soreness should be considered when investigating dry needling effectiveness since it could overlie the original myofascial pain and influence the patients’ pain ratings.     

Superficial versus deep dry needling

Ninety percent of my patients with myofascial trigger point (MTrP) pain have this alone and are treated with superficial dry needling. Approximately 10% have concomitant MTrP pain and nerve root compression pain. These are treated with deep dry needling. SUPERFICIAL DRY NEEDLING (SDN): The activated and sensitised nociceptors of a MTrP cause it to be so exquisitely tender that firm pressure applied to it gives rise to a flexion withdrawal reflex (jump sign) and in some cases the utterance of an expletive (shout sign). The optimum strength of SDN at a MTrP site is the minimum necessary to abolish these two reactions. With respect to this patients are divided into strong, average and weak responders. The responsiveness of each individual is determined by trial and error. It is my practice to insert a needle (0.3mm x 30mm) into the tissues immediately overlying the MTrP to a depth of 5-10 mm and to leave it in situ long enough for the two reactions to be abolished. For an average reactor this is about 30secs. For a weak reactor it is several minutes. And for a strong reactor the insertion of the needle and its immediate withdrawal is all that is required. Following treatment muscle stretching exercises should be carried out, and any steps taken to eliminate factors that might lead to the reactivation of the MTrPs. DEEP DRY NEEDLING (DDN): This in my practice is only used either when primary MTrP activity causes shortening of muscle sufficient enough to bring about compression of nerve roots. Or when there is nerve compression pain usually from spondylosis or disc prolapse and the secondary development of MTrP activity. Unlike SDN, DDN is a painful procedure and one which gives rise to much post-treatment soreness.     

The effect of dry needling & muscle energy technique separately and in combination in patients suffering shoulder impingement syndrome and active trigger points of infraspinatus

ObjectiveThe aim of this study was to investigate the effects of a combination of dry needling (DN) and muscle energy technique (MET) on pain intensity (PI), pressure pain threshold (PPT) and shoulder active range of motion (ROM) in patients with shoulder impingement syndrome and active trigger points in the infraspinatus muscle.Methods39 patients, aged 20–50 participated in this study. All the cases were randomly assigned into three groups: group 1 (n = 13) received DN, group 2 (n = 13) received MET, and group 3 (n = 13) received DN & MET. The patients were treated for three sessions in a one-week period with at least a two-day break between sessions.ResultsThe results showed a significant improvement in visual analog scale (VAS), PPT and shoulder ROM over time (P < 0.001) in all three groups. There were no significant differences BETWEEN VAS (P = 0.406) PPT (P = 0.293), external rotation(EXT.ROT) (0.476), internal rotation (INT.ROT)(P = 0.476) and extension(EXT) (P = 0.574) ROMs in the three groups; however, DN group was significantly more effective on abduction(ABD) (P = 0.003) and flexion(FLEX) (0.012) ROM compared with other two groups.ConclusionIn line with previous studies, the present study found that the application of DN, MET and combined of these treatment on active trigger points in the infraspinatus muscle of patients with shoulder impingement syndrome helps reduce pain, increase PPT and enhance the shoulder ROM. Both techniques are effective in the treatment of trigger points. Nevertheless, DN is more effective in enhancing the ROM of flexion & abduction.     

Immediate effects of various physical therapeutic modalities on cervical myofascial pain and trigger-point sensitivity

OBJECTIVE: To investigate the immediate effect of physical therapeutic modalities on myofascial pain in the upper trapezius muscle. DESIGN: Randomized controlled trial. SETTING: Institutional practice. PATIENTS: One hundred nineteen subjects with palpably active myofascial trigger points (MTrPs). INTERVENTION: Stage 1 evaluated the immediate effect of ischemic compression, including 2 treatment pressures (P1, pain threshold; P2, averaged pain threshold and tolerance) and 3 durations (T1, 30s; T2, 60s; T3, 90s). Stage 2 evaluated 6 therapeutics combinations, including groups B1 (hot pack plus active range of motion [ROM]), B2 (B1 plus ischemic compression), B3 (B2 plus transcutaneous electric nerve stimulation [TENS]), B4 (B1 plus stretch with spray), B5 (B4 plus TENS), and B6 (B1 plus interferential current and myofascial release). MAIN OUTCOME MEASURES: The indexes of changes in pain threshold (IThC), pain tolerance (IToC), visual analog scale (IVC), and ROM (IRC) were evaluated for treatment effect. RESULTS: In stage 1, the IThC, IToC, IVC, and IRC were significantly improved in the groups P1T3, P2T2, and P2T3 compared with the P1T1 and P1T2 treatments (P<.05). In stage 2, groups B3, B5, and B6 showed significant improvement in IThC, ItoC, and IVC compared with the B1 group; groups B4, B5, and B6 showed significant improvement in IRC compared with group B1 (P<.05). CONCLUSIONS: Ischemic compression therapy provides alternative treatments using either low pressure (pain threshold) and a long duration (90s) or high pressure (the average of pain threshold and pain tolerance) and short duration (30s) for immediate pain relief and MTrP sensitivity suppression. Results suggest that therapeutic combinations such as hot pack plus active ROM and stretch with spray, hot pack plus active ROM and stretch with spray as well as TENS, and hot pack plus active ROM and interferential current as well as myofascial release technique, are most effective for easing MTrP pain and increasing cervical ROM.     

Dry needling of the trapezius muscle in office workers with neck pain: a randomized clinical trial

Background: Neck pain is a frequent complaint in office workers. This pain can be caused by myofascial trigger points (MTrPs) in the trapezius muscle. This study aimed to determine the effectiveness of deep dry needling (DDN) of active MTrPs in the trapezius muscle.

Methods: A randomized, single blinded clinical trial was carried out at the Physical Therapy Department at Physiotherapy in Women's Health Research Group at Physical Therapy Department of University of Alcalá, in Alcalá de Henares, Madrid, Spain. Forty-four office workers with neck pain and active MTrPs in the trapezius muscle were randomly allocated to either the DDN or the control group (CG). The participants in the DDN group were treated with DDN of all MTrPs found in the trapezius muscle. They also received passive stretch of the trapezius muscle. The CG received the same passive stretch of the trapezius muscle only. The primary outcome measure was subjective pain intensity, measured using a visual analogue scale (VAS). Secondary outcomes were pressure pain threshold (PPT), cervical range of motion (CROM) and muscle strength. Data were collected at baseline, after interventions and 15?days after the last treatment.

Results: Differences were found between the DDN group and the CG for the VAS (P?P?P?P?Discussion: Deep dry needling and passive stretch seems to be more effective than passive stretch only. The effects are maintained in the short term. The results support the use of DDN in the management of trapezius muscle myofascial pain syndrome in neck pain.     

A comparison between different modes of real-time sonoelastography in visualizing myofascial trigger points in low back muscles

Objective: Currently, there is a lack of objective means to quantify myofascial trigger points (MTrPs) and their core features. Our research compares (1) MTrPs and surrounding myofascial tissue using two-dimensional grayscale ultrasound (2DGSUS) and vibration sonoelastography (VSE); (2) the accuracy of both modes in visualizing MTrPs; (3) ‘active’ and ‘latent’ MTrPs, using VSE; and (4) the accuracy of both modes in visualizing deep and superficially located MTrPs.

Methods: Fifty participants with more than two MTrPs in their quadratus lumborum, longissimus thoracis, piriformis, and gluteus medius muscles were assigned to an active MTrP (low back pain) group or a latent (currently pain free) MTrP group. MTrP identification was based on their essential criteria. An electronic algometer measured repeatedly the tenderness of MTrPs with reference to pressure pain threshold values. A handheld vibrator was applied over MTrPs, while VSE and 2DGSUS readings were taken using an EUB-7500 ultrasound scanner.

Results: There was a significant difference between MTrP strain and that of the immediately surrounding myofascial tissue, as measured using VSE (P?=?0·001). VSE visualized all superficial and deep MTrPs with an accuracy of 100% (for both groups); the blinded results obtained using 2DGSUS achieved 33% and 35% accuracy, respectively. There was no significant difference found between the tissue strain ratios of active and latent MTrPs (P?=?0·929).

Discussion: Sonoelastography can visualize superficial and deep MTrPs, and differentiate them from surrounding myofascial structure through tissue stiffness and echogenicity. VSE was more accurate than 2DGSUS in visualizing and imaging MTrPs.     

Comparison of two different techniques of electrotherapy on myofascial pain

This study was designed to compare the effects of Transcutaneus Electrical Nerve Stimulation (TENS) and Electrical Muscle Stimulation (EMS) on myofascial trigger point (MTrP) of the upper trapezius muscle. A total of 40 patients were randomly divided into three groups. All patients had active MTrP in one side of the upper trapezius muscles. Group I was treated with TENS and trapezius-stretching exercises; Group II was treated with EMS and trapezius-stretching exercises and Group III, the control group, had only trapezius-stretching exercises. Subjective pain intensity with VAS, range of motion (ROM), and pain threshold (PT) were assessed before, immediately after two week treatment and 3 months after treatment. Group I had a statistically significant reduction in VAS (P<0.01), increase in PT and ROM (p<0.05) at end of the treatment when compared with the control group. Only VAS was significantly improved (p<0.05) in the Group II patients. At the end of the third month, both groups showed highly significant improvement (p<0.01) in VAS and PT (but not ROM). There was no statistical difference in none of parameters between EMS and TENS groups in any time (p>0.05). In conclusion, TENS seem to be more effective immediately after treatment but in long term evaluation there is no significant superiority of two electrotherapy techniques on each other.     

Effects of myofascial trigger point dry cupping on pain and function in patients with plantar heel pain: A randomized controlled trial

ObjectiveTo investigate the effects of dry cupping on calf muscle myofascial trigger points (MTrPs) on pain and function in patients with plantar heel pain.MethodsSeventy-one patients were randomly divided into an intervention group or control group. Both groups performed stretching exercises for the calf muscle and plantar fascia and ankle dorsiflexion exercises. The intervention group also received dry cupping. The primary outcome measures were visual analogue scale (VAS), pressure pain threshold (PPT), and patient-specific functional scale (PSFS). The secondary outcomes were ankle dorsiflexion range of motion (ROM) and ankle plantar flexor strength. These measurements were performed at baseline, immediately after intervention, and after 2 days.ResultsCurrent VAS significantly decreased immediately in the intervention group (p = 0.002), but not in the control group (p ≥ 0.220). Morning VAS decreased significantly in both groups (p < 0.001) after 2 days, but decreased more in the intervention group (p = 0.006). Trigger point PPT significantly improved immediately in the intervention group (p = 0.003), but not in the control group (p = 0.112). Both groups improved significantly in PSFS (p < 0.001) and ankle dorsiflexion ROM (p < 0.001). Plantar flexor strength significantly increased immediately in the intervention group (p < 0.001), but not in the control group (p = 0.556).ConclusionAdding dry cupping on calf MTrPs to self-stretching and ankle dorsiflexion exercises for patients with plantar heel pain was superior to only self-stretching and active ankle dorsiflexion exercises in pain, ankle dorsiflexion ROM, and plantar flexor strength.     

Proximal myofascial pain in patients with distal complex regional pain syndrome of the upper limb

BackgroundPatients suffering from complex regional pain syndrome (CRPS) endure myofascial-related pain in at least 50% of cases.AimsTo evaluate the association of upper limb CRPS with myofascial pain in muscles that might influence arm or hand pain, and to evaluate whether the paraspinal skin and subcutaneous layers’ tenderness and allodynia are associated with CRPS.MethodsA case-control study comprising 20 patients presenting with upper limb CRPS, and 20 healthy controls matched for sex and age, were evaluated in the thoracic paraspinal area and myofascial trigger points (MTrPs) (infraspinatus, rhomboids, subclavius, serratus posterior superior and pectoralis minor) via a skin rolling test.ResultsThe prevalence of MTrPs in the affected extremity of the subjects was significantly higher than in the right limb of the controls: 45% exhibited active and latent MTrPs in the infraspinatus muscle (χ² = 11.613, p = 0.001); 60% in active and latent MTrPs in the subclavius muscle (χ² = 17.143, p < 0.001); and in the pectoralis minor muscle (χ2 = 13.786, p < 0.001). In addition, 55% of the cases exhibited active and latent MTrPs in the serratus posterior superior muscle (χ² = 15.172, p < 0.001). Significant differences between the groups in skin texture and pain levels (p = 0.01, p < 0.001, respectively) demonstrated that CRPS patients felt more pain, and their skin and subcutaneous layers were much tighter than in the healthy controls.ConclusionThere is a high prevalence of MTrPs in the shoulder and upper thoracic area muscles in subjects who suffer from CRPS. We recommend adding an MTrPs evaluation to the standardized examination of these patients.     

Myofascial trigger point needling for whiplash associated pain – A feasibility study

Clinicians claim that myofascial trigger points (MTrPs) are a primary cause of pain in whiplash injured patients. Pain from MTrPs is often treated by needling, with or without injection. We conducted a placebo controlled study to test the feasibility of a phase III randomised controlled trial investigating the efficacy of MTrP needling in patients with whiplash associated pain.Forty-one patients referred for physiotherapy with a recent whiplash injury, were recruited. Patients were randomised to receive standardised physiotherapy plus either acupuncture or a sham needle control. A trial was judged feasible if: i) the majority of eligible patients were willing to participate; ii) the majority of patients had MTrPs; iii) at least 75% of patients provided completed self-assessment data; iv) no serious adverse events were reported and v) the end of treatment attrition rate was less than 20%.70% of those patients eligible to participate volunteered to do so; all participants had clinically identified MTrPs; a 100% completion rate was achieved for recorded self-assessment data; no serious adverse events were reported as a result of either intervention; and the end of treatment attrition rate was 17%.A phase III study is both feasible and clinically relevant. This study is currently being planned.     

Comparison of the effect of two different types of dry-needling techniques on subacromial impingement syndrome

IntroductionInfraspinatus is one of the main muscles that is involved in the subacromial impingement syndrome. Dry needling and routine physical therapy can improve this syndrome. However, the dry needling technique is not well defined.Designrandomized controlled clinical trial, single-blind study.MethodSixty-six patients diagnosed with shoulder impingement syndrome were recruited and randomly divided into three groups.InterventionsIn 1st group; patients received deep dry needling technique in addition to routine physical therapy, in Hong's group; patients received Hong's dry needling technique in addition to routine physiotherapy and in third group; patient just received routine physical therapy.Main outcome measure(s)Before, immediately after and 4 weeks after the intervention, pain, disability and the pressure pain threshold were measured.ResultsThe findings of this study indicated that in DDN group, pain and disability reduction was significantly more than two other groups. Although, the pressure pain tolerance increased in all three groups after treatment, but the increase between groups was not significantly different. All study groups showed reduction in pain, while there was no significant difference between the three groups.ConclusionPain and disability reduction in the DDN group compared to the other two groups may reveal the treatment with deep dry needling technique along with routine physiotherapy is more effective than receiving dry needling with Hong's technique or routine physiotherapy alone. However, there was no significant difference between the three groups in pressure pain tolerance threshold and pain reduction.     

Interrater Reliability of Palpation of Myofascial Trigger Points in Three Shoulder Muscles

This observational study included both asymptomatic subjects (n=8) and patients with unilateral or bilateral shoulder pain (n=32). Patient diagnoses provided by the referring medical physicians included subacromial impingement, rotator cuff disease, tendonitis, tendinopathy, and chronic subdeltoid-subacromial bursitis. Three raters bilaterally palpated the infraspinatus, the anterior deltoid, and the biceps brachii muscles for clinical characteristics of a total of 12 myofascial trigger points (MTrPs) as described by Simons et al. The raters were blinded to whether the shoulder of the subject was painful. In this study, the most reliable features of trigger points were the referred pain sensation and the jump sign. Percentage of pair-wise agreement (PA) was ≥ 70% (range 63–93%) in all but 3 instances for the referred pain sensation. For the jump sign, PA was ≥ 70% (range 67–77%) in 21 instances. Finding a nodule in a taut band (PA = 45–90%) and eliciting a local twitch response (PA = 33–100%) were shown to be least reliable. The best agreement about the presence or absence of MTrPs was found for the infraspinatus muscle (PA = 69–80%). This study provides preliminary evidence that MTrP palpation is a reliable and, therefore, potentially useful diagnostic tool in the diagnosis of myofascial pain in patients with non-traumatic shoulder pain.Key Words: Myofascial Pain Syndrome, Myofascial Trigger Points, Interrater Reliability, Palpation, Shoulder PainShoulder complaints are very common in modern industrial countries. Recent reviews^1–4 have indicated a one-year prevalence ranging from 4.7 to 46.7%. These reviews have also reported a lifetime prevalence between 6.7 and 66.7%. This wide variation in reported prevalence can be explained by the different definitions used for shoulder complaints and by differences in the age and other characteristics of the various study populations. Because making a specific structure-based diagnosis for patients with shoulder complaints is considered difficult due to the lack of reliable tests for shoulder examination, recent guidelines developed by the Dutch Society of General Practitioners have recommended instead using the term “shoulder complaints” as a working diagnosis⁵. Shoulder complaints have been defined in a similarly non-specific manner as signs and symptoms of pain in the deltoid and upper arm region, and stiffness and restricted movements of the shoulder, often accompanied by limitations in daily activities⁶.Despite the absence of reliable diagnostic tests to implicate these structures, the currently prevailing assumption is that in non-traumatic shoulder complaints, mostly the anatomical structures in the subacromial space are involved, i.e., the subacromial bursa, the rotator cuff tendons, and the tendon of the long head of the biceps muscle^7–9. However, this assumption does not take into account that muscle tissue itself can also give rise to pain in the shoulder region¹⁰. In our clinical experience, myofascial trigger points (MTrPs) may lead to myofascial pain in the shoulder and upper arm region and contribute to the burden of shoulder complaints.The term myofascial pain was first introduced by Travell¹⁰, who described it as “the complex of sensory, motor, and autonomic symptoms caused by myofascial trigger points.” An MTrP is a hyperirritable spot in skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band. In addition, the spot is painful on compression and may produce characteristic referred pain, referred tenderness, motor dysfunction, and autonomic phenomena. Two different types of MTrPs have been described: active and latent. Active trigger points are associated with spontaneous complaints of pain. In contrast, latent trigger points do not cause spontaneous pain, but pain may be elicited with manual pressure or with needling of the trigger point. Despite not being spontaneously painful, latent MTrPs have been hypothesized to restrict range of motion¹¹ and to alter motor recruitment patterns¹².As noted above, referred pain is a key characteristic of myofascial pain. Referred pain is felt remote from the site of origin¹³. The area of referred pain may be discontinuous from the site of local pain or it can be segmentally related to the lesion, both of which may pose a serious problem for the correct diagnosis and subsequent appropriate treatment of muscle-related pain. The theoretical model for this phenomenon of referred pain was first proposed by Ruch¹⁴ and later modified by Mense^13–15 and Hoheisel¹⁴. Referred pain patterns originating in muscles have been documented using injection of hypertonic saline, electrical stimulation, or pressure on the most sensitive spot in the muscle^17–21. In the clinical setting, palpation is the only method capable of diagnosing myofascial pain. Therefore, reliable MTrP palpation is the necessary prerequisite for considering myofascial pain as a valid diagnosis²². Published interrater studies have reported poor to good reliability for MTrP palpation^23–29. However, only one study has included a muscle that could produce shoulder pain: Gerwin et al²⁷ reported a percent agreement (PA) of 83% for tenderness in the infraspinatus muscle (κ=0.48), 83% (κ=0.40) for the taut band, 59% (κ=0.17) for the local twitch response, and 89% (κ=0.84) for the referred pain.In light of this near absence of data, of the societal impact of shoulder complaints as noted above, and of the potential role of myofascial pain syndrome with regard to shoulder pain, the aim of this study was to determine the interrater reliability of MTrP palpation in three human shoulder muscles deemed by us to be clinically relevant, i.e., the infraspinatus, the anterior deltoid, and the biceps brachii muscles.     

Bilateral activation of motor unit potentials with unilateral needle stimulation of active myofascial trigger points

OBJECTIVE: The objective of this study was to determine if there are electromyographic differences between active and latent myofascial trigger points (MTrPs) during trigger point needling. DESIGN: A total of 21 subjects were recruited prospectively. The experimental group consisted of 13 subjects who had active myofascial pain in the neck for >6 mos. The age-matched, control group consisted of eight subjects without neck pain but with taut bands in the cervical musculature. The active MTrPs (or latent MTrPs in the control group) were identified in the trapezius or levator scapulae muscles, then needle electrodes were inserted ipsilaterally into the muscle with the MTrPs and into the same muscle on the contralateral side. Electromyographic activity was recorded bilaterally with a dual-channel electromyographic machine, and local twitch responses were obtainedusinganacupuncturedryneedlingtechniqueonlyonthesideoftheactiveMTrPs. RESULTS: We demonstrated that in subjects with active MTrPs, bilateral motor unit activation could be obtained with unilateral needle stimulation of the trigger point. In contrast, in all the subjects with latent MTrPs, only unilateral motor unit activation could be obtained in the muscle on the same side of the needle stimulation. The motor unit potentials seen on the electromyograph were similar in morphology to a fasciculation potential but more complex. CONCLUSION: We demonstrated bilateral or mirror-image electromyographic activity associated with unilateral needle stimulation of active MTrPs. We have found no previous mention of this phenomenon in the literature. Our study supports the concept that the perpetuation of pain and muscle dysfunction in active MTrPs may be related to abnormal central nervous system processing of sensory input at the level of the spinal cord.     

Prevalence and sensitivity of trigger points in lumbo-pelvic-hip muscles in patients with patellofemoral pain syndrome

ObjectivesChanges in the activity of the lumbo-pelvic-hip muscles have been established as a major cause of patellofemoral pain syndrome (PFPS), a common orthopedic problem. The present study aimed to compare the prevalence and sensitivity of myofascial trigger points (MTrPs) in lumbo-pelvic-hip muscles in persons with and without PFPS.MethodsThirty women with PFPS and 30 healthy women 18–40 years old were recruited for this study. The prevalence of MTrPs was assessed by palpation, and pressure algometry was used to measure the pressure pain threshold. This study evaluated the areas where MTrPs are most commonly found in the lumbar muscles (internal oblique, erector spinae and quadratus lumborum), pelvic muscles (gluteus maximus, gluteus medius, gluteus minimus and piriformis), and hip muscles (hip adductor, quadriceps, hamstring, tensor fascia lata and sartorius). Independent t-tests were used to compare mean pressure pain thresholds between the two groups. Chi-squared tests were used to compare the prevalence of MTrPs.ResultsThe prevalence of MTrPs was significantly higher in most of the lumbo-pelvic-hip muscles in patients with PFPS compared to healthy persons. However, there were no significant differences between groups in the prevalence of MTrPs in the gluteus minimus or adductor muscles. The pressure pain threshold in lumbo-pelvic-hip muscles was lower in patients with PFPS compared to healthy participants.ConclusionIn patients with PFPS the prevalence of MTrPs in the lumbo-pelvic-hip region was higher, and the pressure pain threshold was lower, than in healthy people. Thus therapy to treat PFPS should target the lumbo-pelvic-hip muscles.