Peripheral Activation of Formyl Peptide Receptor 2/ALX by Electroacupuncture Alleviates Inflammatory Pain by Increasing Interleukin-10 Levels and Catalase Activity in Mice.

In the context of the electroacupuncture (EA) neurobiological mechanisms, we have previously demonstrated the involvement of formyl peptide receptor 2 (FPR2/ALX) in the antihyperalgesic effect of EA. The present study investigated the involvement of peripheral FPR2/ALX in the antihyperalgesic effect of EA on inflammatory cytokines levels, oxidative stress markers and antioxidant enzymes in an animal model of persistent inflammatory pain. Male Swiss mice underwent intraplantar (i.pl.) injection with complete Freund's adjuvant (CFA). Mechanical hyperalgesia was assessed with von Frey monofilaments. Animals were treated with EA (2/10 Hz, ST36-SP6, 20 minutes) for 4 consecutive days. From the first to the fourth day after CFA injection, animals received i.pl. WRW4 (FPR2/ALX antagonist) or saline before EA. Levels of inflammatory cytokines (TNF, IL-6, IL-4 and IL-10), antioxidant enzymes (catalase and superoxide dismutase), oxidative stress markers (TBARS, protein carbonyl, nitrite/nitrate ratio), and myeloperoxidase activity were measured in paw tissue samples. As previously demonstrated, i.pl. injection of the FPR2/ALX antagonist prevented the antihyperalgesic effect induced by EA. Furthermore, animals treated with EA showed higher levels of IL-10 and catalase activity in the inflamed paw, and these effects were prevented by the antagonist WRW4. EA did not change levels of TNF and IL-6, SOD and MPO activity, and oxidative stress markers. Our work demonstrates that the antihyperalgesic effect of EA on CFA-induced inflammatory pain could be partially associated with higher IL-10 levels and catalase activity, and that these effects may be dependent, at least in part, on the activation of peripheral FPR2/ALX.

Exploring the effect of capsaicin-induced central sensitization on the upper limb nociceptive withdrawal reflex threshold.

The nociceptive withdrawal reflex (NWR) threshold is commonly employed in the lower limb to assess clinical and experimentally induced pain. However, no studies to date have investigated changes in spinal nociception in the upper limb, via the NWR threshold, following experimentally induced central sensitization (CS). We tested the hypothesis that experimentally induced CS of the C5-C6 spinal segment significantly reduces NWR thresholds in muscles of the upper limb. Upper limb NWR thresholds from 20 young, healthy adults were assessed by applying noxious electrical stimuli to the right index finger and recording muscle activity from the biceps brachii (BI), triceps brachii (TRI), flexor carpi ulnaris (WF), and extensor carpi radialis longus (WE) muscles via surface electromyography. Topical cream (either 0.075% capsaicin, or control) was applied to the C5-C6 dermatome of the lateral forearm (50 cm2). NWR thresholds were compared at baseline, and four 10-min intervals after topical application. WF muscle NWR thresholds were significantly reduced in the capsaicin session compared to control, while TRI muscle NWR thresholds were significantly reduced 40 min after capsaicin application only (p < 0.05). There were no significant differences for BI or WE muscle NWR thresholds. We observed poor to moderate test-retest reliability for all upper limb NWR thresholds, a key contributor to the selective reduction in NWR thresholds among muscles. Accordingly, while our findings demonstrate some comparability to previously reported lower limb NWR studies, we concurrently report limitations of the upper limb NWR technique. Further exploration of optimal parameters for upper limb NWR acquisition is needed.

Increased Substance P Immunoreactivity in Ipsilateral Knee Cartilage of Rats Exposed to Lumbar Spine Injury.

OBJECTIVE: The present study aimed to investigate whether experimentally induced lumbar facet-joint OA lead to degenerative changes and enhanced SP expression within the ipsilateral neurosegmentally linked tibiofemoral cartilage. METHODS: Adult male Sprague-Dawley rats were assigned to left side L5-L6 facet mechanical compression injury (surgery) (n = 6), L5-L6 facet exposure with no compression (sham) (n = 5), or naïve (no surgery) (n = 4) groups. The morphology of the tibiofemoral articular cartilage was assessed using a modified Mankin scoring system. Immunohistochemistry was used to examine the density of chondrocytes stained positive for SP (cells/cm2) in the ipsilateral tibiofemoral cartilage at 28 days postintervention. RESULTS: Tibiofemoral cartilage in the surgery group showed consistent loss of superficial zone chondrocytes, mild roughening of the articular surface and occasional chondrocyte clusters as well as a greater density of SP mainly in the superficial cartilage zone compared with sham and naïve groups, although they also had a basic SP-expression. CONCLUSION: Our results support the hypothesis that neurogenic mechanisms may mediate the spread of SP to neurosegmentally linked heterologous joints affecting the distal cartilage homeostasis. These findings contribute additional insight into the potential role of neurogenic inflammation with implications in the pathophysiology of chronic inflammatory joint disease and OA.

The Acute Effect of Skin Preheating on Capsaicin-Induced Central Sensitization in Humans.

INTRODUCTION: Topical capsaicin is commonly employed to experimentally induce central sensitization (CS) in humans. While previous studies have investigated the effect of skin preheating on the sensitizing effect of capsaicin, no studies have compared the synergistic effect of skin preheating on the magnitude of sensitization via topical capsaicin within the first 30 minutes of application. We tested the hypothesis that skin preheating potentiates the sensitizing effect of topical capsaicin by evoking a larger region of secondary hyperalgesia vs. topical capsaicin alone. METHODS: Twenty young, healthy subjects each received topical capsaicin (Zostrix HP 0.075%) only (CAP), topical capsaicin with preheating (CAP + HEAT), and topical nonsensitizing placebo cream (CON) in a crossover design. Capsaicin and placebo creams were applied to a 50 cm2 area of the dorsal forearm. The CAP + HEAT session also included a 10-minute preheating session. Regions of secondary hyperalgesia were assessed using mechanical brush allodynia testing, and skin temperature was assessed via infrared thermography. Outcomes were normalized to baseline and compared at 10, 20, and 30 minutes after cream application. RESULTS: The CAP + HEAT session led to a significantly larger area of secondary hyperalgesia compared to the CAP session as measured by brush allodynia (CON: 0 ± 0 cm; CAP: 2.08 ± 0.45 cm; CAP + HEAT: 3.70 ± 0.46 cm; P < 0.05) and skin temperature (CON: -2.92% ± 0.03%; CAP: -0.63% ± 0.09%; CAP + HEAT: 2.50% ± 0.11%; ( of baseline) P < 0.05). CONCLUSION: Preheating amplifies the sensitizing effect of topical capsaicin within 30 minutes of application. The heat-capsaicin technique may be employed to assess differing magnitudes of CS induction and enables future studies investigating the development and progression of CS in humans.

Association between naturally occurring spine osteoarthritis in geriatric rats and neurogenic inflammation within neurosegmentally linked skeletal muscle.

OBJECTIVE: This study aimed to investigate the association between naturally occurring spinal osteoarthritis (OA) (L3-L5), the expression of substance P (SP) centrally (L4-L5) and the presence of neurogenic inflammation within the neurosegmentally linked quadriceps (L2-L5) in elderly rats versus young controls. DESIGN: Eight aged (27 ±â€¯3.2 months) and six young (4 ±â€¯0.0 months) male Wistar Kyoto rats were euthanized and submitted to micro-computerized tomography for determination of spine OA. SP expression (% area) at the dorsal horn of the spinal cord as well as the relative expression of SP and protease-activated receptor 2 (PAR2) to alpha-tubulin within quadriceps muscle were determined by immunohistochemistry and Western Blot. RESULTS: Spine osteoarthritis was confirmed in all aged rats but no young controls. Aged rats expressed significant increase of SP protein expression within the dorsal horn (MD = 0.086; 95% CI [0.026 to 0.145]; p = 0.0094) and quadriceps (MD = 1.209; 95% CI [0.239 to 2.179]; p = 0.0191) and PAR2 (MD = 0.797; 95% CI [0.160 to 1.435]; p = 0.0187) compared to young controls. CONCLUSION: These observations provide novel insight into the potential role of neurogenic inflammation in the pathophysiology of myofascial pain syndrome in the naturally occurring spinal OA in elderly population.

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

BACKGROUND: 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. METHODS: Thirty-three participants were randomly recruited from the local university community. PPT measures were recorded from a clinically identified myofascial trigger point within the right infraspinatus muscle during pressure algometry. A total of 2 PPT measures were recorded using each of 3 different RoAs, including low (15 N/s), medium (35 N/s), and high (55 N/s). Three baseline trials were also conducted at 30 N/s. The Pearson's correlation coefficient between RoA and PPT was calculated for each subject and averaged across participants. RESULTS: The mean(SD) correlation between subjects was 0.77 (0.19), and the mean (SD) slope of the linear regression was 0.13 (0.09). CONCLUSION: Our results demonstrate that there is a strong, linear relationship between the RoA and PPT when using the pressure algometry technique. The low slope between RoA and PPT suggests clinicians can rely on PPT assessments despite small RoA fluctuations. Future research should explore this relationship further in a clinical population and in other muscles affected by chronic myofascial pain. Advancing cost-effective, reliable, and clinically feasible tools such as algometry is important to enhancing the diagnosis and management of chronic myofascial pain.

The Effect of Abdominal Muscle Activation Techniques on Trunk and Lower Limb Mechanics During the Single-Leg Squat Task in Females.

CONTEXT: Females suffer 4 to 6 times more noncontact anterior cruciate ligament (ACL) injuries than males due to neuromuscular control deficits of the hip musculature leading to increases in hip adduction angle, knee abduction angle, and knee abduction moment during dynamic tasks such as single-leg squats. Lateral trunk displacement has been further related to ACL injury risk in females, leading to the incorporation of core strength/stability exercises in ACL preventative training programs. However, the direct mechanism relating lateral trunk displacement and lower limb ACL risk factors is not well established. OBJECTIVE: To assess the relationship between lateral trunk displacement and lower limb measures of ACL injury risk by altering trunk control through abdominal activation techniques during single-leg squats in healthy females. DESIGN: Interventional study setting: movement and posture laboratory. PARTICIPANTS: A total of 13 healthy females (21.3 [0.88] y, 1.68 [0.07] m, and 58.27 [5.46] kg). INTERVENTION: Trunk position and lower limb kinematics were recorded using an optoelectric motion capture system during single-leg squats under differing conditions of abdominal muscle activation (abdominal hollowing, abdominal bracing, and control), confirmed using surface electromyography. MAIN OUTCOME MEASURES: Lateral trunk displacement, peak hip adduction angle, peak knee abduction angle/moment, and average muscle activity from bilateral internal oblique, external oblique, and erector spinae muscles. RESULTS: No differences were observed for peak lateral trunk displacement, peak hip adduction angle, or peak knee abduction angle/moment. Abdominal hollowing and bracing elicited greater muscle activation than the control condition, and bracing was greater than hollowing in 4 of 6 muscles recorded. CONCLUSION: The lack of reduction in trunk, hip, and knee measures of ACL injury risk during abdominal hollowing and bracing suggests that these techniques alone may provide minimal benefit in ACL injury prevention training.

A Comparison of the Sensitivity of Brush Allodynia and Semmes-Weinstein Monofilament Testing in the Detection of Allodynia Within Regions of Secondary Hyperalgesia in Humans.

BACKGROUND: Two of the most common Quantitative Sensory Techniques (QST) employed to detect allodynia include mechanical brush allodynia and Semmes-Weinstein monofilaments. However, their relative sensitivity at detecting allodynia is poorly understood. The purpose of this study was to compare the sensitivity of brush allodynia against Semmes-Weinstein monofilament technique for detecting allodynia within regions of secondary hyperalgesia in humans. METHODS: Twenty subjects (10 males, 10 females; 21.1 ± 0.9 years) were recruited and randomly allocated to allodynia or monofilament groups. Topical capsaicin (Zostrix 0.075%) was applied to a target region defined by C4-C7 dermatomes. Allodynia testing was performed at 0- (baseline) and 10 minutes postcapsaicin. The Semmes-Weinstein group assessed changes in skin sensitivity 8 cm inferior to target region and 2 cm lateral to the spinous process, while brush allodynia was employed to detect the point inferior to the target region where subjects reported changes in skin sensitivity. The distance (cm) from this point to the inferior border of the target region was termed the Allodynia Score. RESULTS: Statistically significant increases in the Allodynia Score were observed at 10 minutes postcapsaicin compared to baseline (P < 0.001). No differences in monofilament scores were observed between 10 minutes postcapsaicin and baseline (P = 0.125). Brush allodynia also demonstrated superior sensitivity, detecting allodynia in 100% of cases compared to 60% in the Semmes-Weinstein group. CONCLUSION: Brush allodynia is more sensitive than Semmes-Weinstein monofilaments for detecting mechanical allodynia in regions of secondary hyperalgesia. Brush allodynia may be preferred over Semmes-Weinstein monofilaments for clinical applications requiring reliable detection of allodynia.

A narrative review of new trends in the diagnosis of myofascial trigger points: diagnostic ultrasound imaging and biomarkers.

Myofascial pain syndrome (MPS) is one of the most common conditions of chronic musculoskeletal pain encountered by primary healthcare practitioners on a daily basis. It is generally accepted amongst the broad profile of healthcare practitioners treating MPS that the presence of discrete, palpable and tender nodules within the muscle, known as myofascial trigger points (MTrP), is necessary to confirm the diagnosis of MPS. Manual palpation is currently the most common technique used to detect MTrP, however, previous research has shown that the reliability of manual palpation for detecting MTrP is poor, and in our opinion unacceptably poor, leading to inconsistent diagnosis of MPS and poor patient outcomes. There are currently no objective accepted diagnostic criteria for the clinical detection of MTrP, nor are there standardized diagnostic criteria for MPS. Two promising areas of research with potential for enhancing the diagnosis of MPS include the use of diagnostic ultrasound and biomarkers. Further research is needed to advance the development of composite diagnostic criteria employing ultrasound imaging, biomarker assessments and physical assessment to enhance the accuracy and objectivity of MTrP detection and diagnosis of chronic MPS disorder.

Le syndrome algique myofascial (SAM) est l'une des conditions les plus fréquentes de douleurs musculo-squelettiques chroniques rencontrées par les praticiens de soins de santé primaires tous les jours. Il est généralement admis, parmi un large segment de professionnels de la santé traitant le SAM, que la présence de nodules discrets, palpables et tendres dans le muscle, connus sous le nom de points déclencheurs myofasciaux (PDM), est nécessaire pour confirmer le diagnostic de SAM. La palpation manuelle est actuellement la technique la plus couramment utilisée pour détecter les PDM. Cependant, des recherches antérieures ont montré que la fiabilité de la palpation manuelle pour détecter les PDM est faible, et à notre avis inacceptable, ce qui se traduit par des diagnostics incohérents du SAM et de mauvais résultats pour les patients. Actuellement il n'y a aucun critère diagnostique objectif accepté pour la détection clinique des PDM, ni de critères diagnostiques normalisés pour le SAM. Deux domaines prometteurs de recherche ayant un potentiel pour améliorer le diagnostic du SAM comprennent l'utilisation de l'échographie diagnostique et les biomarqueurs. D'autres recherches sont nécessaires pour faire avancer le développement de critères de diagnostic composites employant l'échographie, l'évaluation des biomarqueurs et l'évaluation physique pour améliorer l'exactitude et l'objectivité de la détection des PDM et le diagnostic de troubles de SAM chronique.

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.

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.

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.

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.

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.

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.

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

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, PPT seg, represents the segmental influence on the PPT. The ultrasound test group demonstrated statistically significant increases in PPT seg (decreased infraspinatus sensitivity) at 1, 3 and 5 min, when compared with PPT seg 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.

Ultrasound in the management of osteoarthritis: part I: a review of the current literature.

BACKGROUND: Ultrasound has been widely used in clinical settings for the management of various ailments but many authors still question its efficacy. An accumulating body of literature demonstrates that ultrasound evokes a broad spectrum of bioeffects which may be therapeutically beneficial in the management of a variety of clinical conditions. OBJECTIVE: A critical review the current research investigating the use of therapeutic ultrasound in the treatment and/or management of osteoarthritis. Specific emphasis is placed on interpreting the literature in the context of its strengths and weaknesses, with particular attention placed on study protocols and technical parameters used in the trials. Relevant basic science is also introduced and meaningful inter-study comparisons are highlighted with suggestions for future research. DESIGN: Literature Review. METHODS: A Pubmed search of the literature was performed from 1985 to present using the key words "ultrasound" and "osteoarthritis" retrieved a total of 313 publications. Experimental, clinical and animal studies that directly assessed applications of therapeutic ultrasound in the clinical management of osteoarthritis and/or its underlying physiologic mechanisms were accepted. Studies that evaluated ultrasound in combination with other modalities were accepted but their conclusions were interpreted in the context of their methodological strengths and limitations. RESULTS: A total of 17 articles met our search criteria; one study was excluded due to poor methodology. Of a total of five review papers, two concluded that ultrasound had positive therapeutic effects, two did not demonstrate any benefit and one was inconclusive. The remaining nine studies consistently reported that ultrasound has therapeutically beneficial effects on pain and functional outcomes. Five studies reported that ultrasound has positive cartilage healing properties and one experimental study demonstrated increased intra-articular absorption of high molecular weight molecules (hyaluronan) using ultrasound phonophoresis. Only one randomized controlled trial reported no effect on pain or active range of motion when ultrasound is used in combination with exercise. CONCLUSIONS: Ultrasound demonstrates the ability to evoke a broad range of therapeutically beneficial effects which may provide safe and effective applications in the management of osteoarthritis.

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.