John Srbely

Stimulation of myofascial trigger points with ultrasound induces segmental antinociceptive effects: a randomized controlled study.

Abstract Musculoskeletal pain affects a significant proportion of the general population. The myofascial trigger point is recognized as a key factor in the pathophysiology of musculoskeletal pain. Ultrasound is commonly employed in the treatment and management of soft tissue pain and, in this study, we set out to investigate the segmental antinociceptive effect of ultrasound. Subjects (n = 50) with identifiable myofascial trigger points in the supraspinatus, infraspinatus and gluteus medius muscles were selected from an outpatient rehabilitation clinic and randomly assigned to test or control groups. Test subjects received a therapeutic dose of ultrasound to the right supraspinatus trigger point while control groups received a sham (null) exposure. Baseline pain pressure threshold (PPT) readings were recorded at the ipsilateral infraspinatus and gluteus medius trigger‐point sites prior to ultrasound exposure. The infraspinatus point was chosen due to its segmental neurologic link with the supraspinatus point; the gluteus medius acted as a segmental control point. Following the ultrasound intervention, PPT readings were recorded at 1, 3, 5, 10 and 15 min intervals at both infraspinatus and gluteus medius trigger points; the difference between infraspinatus and gluteus medius PPT values, PPTseg, represents the segmental influence on the PPT. The ultrasound test group demonstrated statistically significant increases in PPTseg (decreased infraspinatus sensitivity) at 1, 3 and 5 min, when compared with PPTseg in the sham ultrasound group. These results establish that low‐dose ultrasound evokes short‐term segmental antinociceptive effects on trigger points which may have applications in the management of musculoskeletal pain.

DRY NEEDLE STIMULATION OF MYOFASCIAL TRIGGER POINTS EVOKES SEGMENTAL ANTI-NOCICEPTIVE EFFECTS

OBJECTIVE To test the hypothesis that dry needle stimulation of a myofascial trigger point (sensitive locus) evokes segmental anti-nociceptive effects. DESIGN Double-blind randomized controlled trial. SUBJECTS Forty subjects (21 males, 19 females). METHODS Test subjects received intramuscular dry needle puncture to a right supraspinatus trigger point (C4,5); controls received sham intramuscular dry needle puncture. Pain pressure threshold (PPT) readings were recorded from right infraspinatus (C5,6) and right gluteus medius (L4,5S1) trigger points at 0 (pre-needling baseline), 1, 3, 5, 10 and 15 min post-needling and normalized to baseline values. The supraspinatus and infraspinatus trigger points are neurologically linked at C5; the supraspinatus and gluteus medius are segmentally unrelated. The difference between the infraspinatus and gluteus medius PPT values (PPTseg) represents a direct measure of the segmental anti-nociceptive effects acting at the infraspinatus trigger point. RESULTS Significant increases in PPTseg were observed in test subjects at 3 (p = 0.002) and 5 (p = 0.015) min post-needling, compared with controls. CONCLUSION One intervention of dry needle stimulation to a single trigger point (sensitive locus) evokes short-term segmental anti-nociceptive effects. These results suggest that trigger point (sensitive locus) stimulation may evoke anti-nociceptive effects by modulating segmental mechanisms, which may be an important consideration in the management of myofascial pain.

Randomized controlled study of the antinociceptive effect of ultrasound on trigger point sensitivity: novel applications in myofascial therapy?

Objective : To investigate whether therapeutic ultrasound modulates the pain sensitivity of myofascial trigger points. Design : Repeated measures, single-blinded randomized controlled trial of ultrasound treatment of trigger points. Setting : Outpatient injury rehabilitation clinic. Subjects : Forty-four patients (22 males, 22 females) with trigger points identified within the trapezius muscle. Interventions : Five-minute therapeutic intensity of ultrasound versus 5-min low-intensity application of ultrasound to a trapezius myofascial trigger point locus. Main measures : Pain pressure threshold readings were measured at the trapezius trigger point site before and after exposure to the ultrasound intervention. Results : Pain pressure threshold scores increased an average of 44.4 (14.2)% after therapeutic exposure to ultrasound (pre-ultrasound test 35.4 (8.5) N, post-ultrasound test 51.1 (12.8) N). No significant difference in pain pressure threshold scores was observed with low-intensity ultrasound exposures (pre-ultrasound 36.1 (6.1) N, post-ultrasound 36.6 (4.8) N). Conclusions : Therapeutic exposures to ultrasound reduce short-term trigger point sensitivity. Ultrasound may be a useful clinical tool for the treatment and management of trigger points and myofascial pain syndromes.

Capsaicin-Induced Central Sensitization Evokes Segmental Increases in Trigger Point Sensitivity in Humans

UNLABELLED This study investigated whether inducing central sensitization evokes segmental increases in trigger point pressure sensitivity. We evoked central sensitization at the C(5) segment and validated its presence via mechanical cutaneous sensitivity (brush allodynia) testing. Trigger point pressure sensitivity was quantified using the pain pressure threshold (PPT) value. A 50 cm(2) area of the C(5) dermatome at the right lateral elbow was pretreated with 45 degrees heat for 10 minutes. Test subjects (n = 20) then received topical capsaicin cream (0.075%; Medicis, Toronto, Canada) to the C(5) dermatome, whereas control subjects (n = 20) received a topical placebo cream (Biotherm Massage, Montreal, Canada). PPT readings were recorded from the infraspinatus (C(5,6)) and gluteus medius (L(4,5)S(1)) trigger points at zero (pre-intervention), 10, 20, and 30 minutes after intervention; all PPT readings were normalized to pre-intervention (baseline) values. The difference between the PPT readings at the 2 trigger point sites represents the direct influence of segmental mechanisms on the trigger point sensitivity at the infraspinatus site (PPT(seg)). Test subjects demonstrated statistically significant increases in Total Allodynia scores and significant decreases in PPT(seg) at 10, 20, and 30 minutes after application, when compared with control subjects. These results demonstrate that increases in central sensitization evoke increases in trigger point pressure sensitivity in segmentally related muscles. PERSPECTIVE Myofascial pain is the most common form of musculoskeletal pain. Myofascial trigger points play an important role in the clinical manifestation of myofascial pain syndrome. Elucidating the role of central sensitization in the pathophysiology of trigger points is fundamental to developing optimal strategies in the management of myofascial pain syndrome.

New Trends in the Treatment and Management of Myofascial Pain Syndrome

Myofascial pain syndrome presents a significant physical and financial burden to society. In view of the aging demographics, myofascial pain promises to be an even greater challenge to health care in the future. Myofascial trigger points have been identified as important anatomic and physiologic phenomena in the pathophysiology of myofascial pain. While their pathophysiologic mechanisms are still unclear, emerging research suggests that trigger points may be initiated by neurogenic mechanisms secondary to central sensitization, and not necessarily by local injury. A variety of treatments are employed in the management of trigger points, including manual therapy, electrotherapy, exercise, and needle therapy. Therapeutic ultrasound demonstrates significant potential as a safe, cost-effective, and relatively noninvasive therapeutic alternative in the treatment and management of this modern day medical enigma.

Immediate Effects of Spinal Manipulative Therapy on Regional Antinociceptive Effects in Myofascial Tissues in Healthy Young Adults

OBJECTIVE The purpose of this study was to investigate if spinal manipulative therapy (SMT) can evoke immediate regional antinociceptive effects in myofascial tissues by increasing pressure pain thresholds (PPTs) over myofascial trigger points in healthy young adults. METHODS A total of 36 participants (19 men, 17 women; age, 28.0 [5.3] years; body mass index, 26.5 [5.7] kg/m(2)) with clinically identifiable myofascial trigger points in the infraspinatus and gluteus medius muscles were recruited from the University of Guelph, Ontario, Canada. Participants were randomly allocated to 2 groups. Participants in the test group received chiropractic SMT targeted to the C5-C6 spinal segment. Participants in the control group received sham SMT. The PPT was recorded from the right infraspinatus and gluteus medius muscles at baseline (preintervention) and 1, 5, 10, and 15 minutes postintervention. RESULTS Three participants were disqualified, resulting in a total of 33 participants analyzed. Significant increases in the PPT (decreased pain sensitivity) were observed in the test infraspinatus group when compared with test gluteus medius, control infraspinatus, and control gluteus medius groups (P < .05). No significant differences in PPT were observed at any time point when comparing test gluteus medius, control infraspinatus, and control gluteus medius groups (P > .05). CONCLUSIONS This study showed that SMT evokes short-term regional increases in PPT within myofascial tissues in healthy young adults.

The Treatment of Neck Pain–Associated Disorders and Whiplash-Associated Disorders: A Clinical Practice Guideline

OBJECTIVE The objective was to develop a clinical practice guideline on the management of neck pain-associated disorders (NADs) and whiplash-associated disorders (WADs). This guideline replaces 2 prior chiropractic guidelines on NADs and WADs. METHODS Pertinent systematic reviews on 6 topic areas (education, multimodal care, exercise, work disability, manual therapy, passive modalities) were assessed using A Measurement Tool to Assess Systematic Reviews (AMSTAR) and data extracted from admissible randomized controlled trials. We incorporated risk of bias scores in the Grading of Recommendations Assessment, Development, and Evaluation. Evidence profiles were used to summarize judgments of the evidence quality, detail relative and absolute effects, and link recommendations to the supporting evidence. The guideline panel considered the balance of desirable and undesirable consequences. Consensus was achieved using a modified Delphi. The guideline was peer reviewed by a 10-member multidisciplinary (medical and chiropractic) external committee. RESULTS For recent-onset (0-3 months) neck pain, we suggest offering multimodal care; manipulation or mobilization; range-of-motion home exercise, or multimodal manual therapy (for grades I-II NAD); supervised graded strengthening exercise (grade III NAD); and multimodal care (grade III WAD). For persistent (>3 months) neck pain, we suggest offering multimodal care or stress self-management; manipulation with soft tissue therapy; high-dose massage; supervised group exercise; supervised yoga; supervised strengthening exercises or home exercises (grades I-II NAD); multimodal care or practitioners advice (grades I-III NAD); and supervised exercise with advice or advice alone (grades I-II WAD). For workers with persistent neck and shoulder pain, evidence supports mixed supervised and unsupervised high-intensity strength training or advice alone (grades I-III NAD). CONCLUSIONS A multimodal approach including manual therapy, self-management advice, and exercise is an effective treatment strategy for both recent-onset and persistent neck pain.

Acute Experimentally Induced Neck Pain Does Not Affect Fatigability of the Peripheral Biceps Brachii Muscle

Evidence has shown that upper limb muscles peripheral to the cervical spine, such as the biceps brachii, can demonstrate functional deficits in the presence of chronic neck pain. However, few studies have examined how neck pain can affect the fatigability of upper limb muscles; therefore we were motivated to investigate the effects of acutely induced neuropathic neck pain on the fatigability of the biceps brachii muscle during isometric contraction to exhaustion. Topical capsaicin was used to induce neck pain in 11 healthy male participants. Surface EMG signals were recorded from the biceps brachii during an isometric elbow flexion fatigue task in which participants held a weight equivalent to 30% of their MVC until exhaustion. Two experimental sessions, one placebo and one capsaicin, were conducted separated by two days. EMG mean power frequency and average normalized activation values were calculated over the course of the fatigue task. In the presence of pain, there was no statistically significant effect on EMG parameters during fatigue of the biceps brachii. These results demonstrate that acutely induced neuropathic neck pain does not affect the fatigability, under the tested conditions, of the biceps brachii.

The Relationship between Rate of Algometer Application and Pain Pressure Threshold in the Assessment of Myofascial Trigger Point Sensitivity

Pressure algometry is a commonly employed technique in the assessment of both regional and widespread musculoskeletal pain. Despite its acceptance amongst clinicians and scientists, the relationship between rate of pressure application (RoA) and pain pressure threshold (PPT) remains poorly understood. We set out to test the hypothesis that a strong, positive, linear relationship exists between the RoA and the PPT within the infraspinatus of young healthy subjects.

Experimentally induced central sensitization in the cervical spine evokes postural stiffening strategies in healthy young adults.

Dysequilibrium of cervicogenic origin can result from pain and injury to cervical paraspinal tissues post-whiplash; however, the specific physiological mechanisms still remain unclear. Central sensitization is a neuradaptive process which has been clinically associated with conditions of chronic pain and hypersensitivity. Strong links have been demonstrated between pain hypersensitivity and postural deficits post-whiplash; however, the precise mechanisms are still poorly understood. The purpose of this study was to explore the mechanisms of cervicogenic disequilibrium by investigating the effect of experimentally induced central sensitization in the cervical spine on postural stability in young healthy adults. Sixteen healthy young adults (7 males (22.6±1.13 years) and 9 females (22±2.69 years)) performed 30-s full-tandem stance trials on an AMTI force plate under normal and centrally sensitized conditions. The primary outcome variables included the standard deviation of the center of pressure (COP) position in medio-lateral (M-L) and antero-posterior (A-P) directions; sway range of the COP in M-L and A-P directions and the mean power frequency (MPF) of the COP and horizontal ground shear forces. Variability and sway range of the COP decreased with experimental induction of central sensitization, accompanied by an increase in MPF of COP displacement in both M-L and A-P directions, suggesting an increase in postural stiffening post-sensitization versus non-sensitized controls. Future studies need to further explore this relationship in clinical (whiplash, chronic pain) populations.