Comparison Between Neck and Shoulder Stiffness Determined by Shear Wave Ultrasound Elastography and a Muscle Hardness Meter

Is musculoskeletal pain associated with increased muscle stiffness? Evidence map and critical appraisal of muscle measurements using shear wave elastography

INTRODUCTION AND AIMS

Approximately 21% of the world's population suffers from musculoskeletal conditions, often associated with sensations of stiff muscles. Targeted therapy requires knowing whether typically involved muscles are objectively stiffer compared to asymptomatic individuals. Muscle stiffness is quantified using ultrasound shear wave elastography (SWE). Publications on SWE-based comparisons of muscle stiffness between individuals with and without musculoskeletal pain are increasing rapidly. This work reviewed and mapped the existing evidence regarding objectively measured muscle stiffness in musculoskeletal pain conditions and surveyed current methods of applying SWE to measure muscle stiffness.

METHODS

A systematic search was conducted in PubMed and CINAHL using the keywords "muscle stiffness", "shear wave elastography", "pain", "asymptomatic controls" and synonyms. The search was supplemented by a hand search using Google Scholar. Included articles were critically appraised with the AXIS tool, supplemented by items related to SWE methods. Results were visually mapped and narratively described.

RESULTS

Thirty of 137 identified articles were included. High-quality evidence was missing. The results comprise studies reporting lower stiffness in symptomatic participants, no differences between groups and higher stiffness in symptomatic individuals. Results differed between pain conditions and muscles, and also between studies that examined the same muscle(s) and pathology. The methods of the application of SWE were inconsistent and the reporting was often incomplete.

CONCLUSIONS

Existing evidence regarding the objective stiffness of muscles in musculoskeletal pain conditions is conflicting. Methodological differences may explain most of the inconsistencies between findings. Methodological standards for SWE measurements of muscles are urgently required.

Local alternating heat and cold stimulation affects hemodynamics and oxygenation in fatigued muscle tissue and autonomic nervous activity: a single-arm interventional study

BACKGROUND

Local alternating heat and cold stimulation as an alternative to contrast bath may cause intermittent vasoconstriction and vasodilation, inducing a vascular pumping effect and consequently promoting increased tissue blood flow and oxygenation. This study aimed to examine the effects of local alternating heat and cold stimulation, using a wearable thermal device, on the hemodynamics of fatigued muscle tissue and autonomic nervous activity.

METHODS

Twenty healthy individuals experienced fatigue in the periarticular muscles of the shoulder joint due to a typing task. Local alternating heat and cold stimulations were then applied to the upper trapezius muscle. Muscle hardness was measured using a muscle hardness meter, and muscle tissue hemodynamics and oxygenation were evaluated using near-infrared spectroscopy before and after the stimulation. Autonomic nervous activity was also evaluated using heart rate variability.

RESULTS

Alternating heat and cold stimulation decreased muscle hardness of the fatigued trapezius muscle from 1.38 ± 0.15 to 1.31 ± 0.14 N (P < 0.01). The concentration of total hemoglobin in the trapezius muscle tissue increased from - 0.21 ± 1.36 to 2.29 ± 3.42 µmol/l (P < 0.01), and the tissue hemoglobin oxygen saturation also increased from 70.1 ± 5.4 to 71.1 ± 6.0% (P < 0.05). Additionally, the heart rate variability parameter, which is an index of sympathetic nervous activity, increased from 3.82 ± 2.96 to 6.86 ± 3.49 (P < 0.01). A correlation was found between increased tissue hemoglobin oxygen saturation and increased parameters of sympathetic nervous activity (r = 0.50, P < 0.05).

CONCLUSIONS

Local alternating heat and cold stimulation affected the hemodynamic response in fatigued muscle tissue and autonomic nervous activity. This stimulation is more efficient than conventional contrast baths in terms of mobility and temperature control and has potential as a new versatile therapeutic intervention for muscle fatigue.

TRIAL REGISTRATION

UMIN-CTR (UMIN000040087: registered on April 7, 2020, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000045710 . UMIN000040620: registered on June 1, 2020, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046359 ).

Levator Scapulae Stiffness Measurement Reliability in Individuals with and without Chronic Neck Pain by Experienced and Novel Examiners

The levator scapulae muscle is a key structure in the etiopathology of neck and shoulder musculoskeletal pain. Although previous studies used shear-wave elastography (SWE) for characterizing this muscle elasticity, limited evidence assessed the inter-examiner reliability of this procedure. This study aimed to analyze the inter-examiner reliability for calculating Young's modulus and shear wave speed in a cohort of participants with and without chronic neck pain. A diagnostic accuracy study was conducted, acquiring a set of SWE images at the C5 level in participants with and without neck pain (n = 34 and 33, respectively) by two examiners (one experienced and one novel). After blinding the participants' identity, examiner involved, and side, the stiffness indicators were calculated by an independent rater in a randomized order. Intra-class correlation coefficients (ICC), standard error of measurement, minimal detectable changes, and coefficient of variation were calculated. Both cohorts had comparable sociodemographic characteristics (p > 0.05). No significant levator scapulae elasticity differences were found between genders, sides, or cohorts (all, p > 0.05). Inter-examiner reliability for calculating Young's modulus and shear wave speed was moderate-to-good for assessing asymptomatic individuals (ICC = 0.714 and 0.779, respectively), while poor-to-moderate in patients with neck pain (ICC = 0.461 and 0.546, respectively). The results obtained in this study support the use of this procedure for assessing asymptomatic individuals. However, reliability estimates were unacceptable to support its use for assessing elasticity in patients with chronic neck pain. Future studies might consider that the shear wave speed is more sensitive to detect real changes in comparison with Young's modulus.

Usefulness of Ultrasound Shear Wave Elastography for Detection of Quadriceps Contracture in Immobilized Rats

Quadriceps contracture is an abnormal pathological shortening of the muscle-tendon unit. To improve the prognosis of quadriceps contracture, improvement of its diagnostic method is needed. In this study, we evaluated the diagnostic utility of ultrasound shear wave elastography in a rat model of quadriceps contracture induced by immobilization. Fifty Wistar rats were randomly divided into control and immobilization groups. During up to 4 weeks of joint immobilization, the quadriceps elastic modulus, muscle hardness, creatinine phosphokinase levels, joint range of motion, histopathologic parameters, and levels of fibrosis-associated mRNA expression were measured every week in the immobilization and control groups and compared. In the immobilization group, the elastic modulus gradually but significantly increased (p < 0.05) throughout the immobilization period. However, muscle hardness and serum creatinine phosphokinase levels only increased at 1 and 2 weeks after the start of immobilization, respectively. Muscle atrophy and shortening progressed throughout the immobilization group. Collagen type I and III, α-SMA protein, and mRNA expression of IL-1β and TGF-β1 significantly increased (p < 0.05) throughout in the immobilization group. Ultrasound shear wave elastography is the most useful method for clinical assessment of muscle contracture.

Defining and measuring objective and subjective spinal stiffness: a scoping review

PURPOSE

Examine and identify the breadth of definitions and measures of objective and subjective spinal stiffness in the literature, with a focus on clinical implications.

METHODS

A scoping review was conducted to determine what is known about definitions and measures of the specific term of spinal stiffness. Following the framework by Arksey and O'Malley, eligible peer-reviewed studies identified using PubMed, Ebsco health, and Scopus were included if they reported definitions or measures of spinal stiffness. Using a data abstraction form, the studies were classified into four themes: biomechanical, surgical, pathophysiological, and segmental spinal assessment. To identify similarities and differences between studies, sixteen categories were generated.

RESULTS

In total, 2426 records were identified, and 410 met the eligibility criteria. There were 350 measures (132 subjective; 218 objective measures) and 93 indicators of spinal stiffness. The majority of studies (n = 69%) did not define stiffness.

CONCLUSION

This review highlights the breadth of objective and subjective measures that are both clinically and methodologically diverse. There is no consensus regarding a standardised definition of stiffness in the reviewed literature.

Viscoelasticity in trapezius myofascial pain syndrome: quantitative assessment using Real-Time Shear-Wave Elastography

OBJECTIVE

To investigate the differences in the viscoelastic properties between normal trapezius muscles and those in patients with trapezius myofascial pain syndrome (MPS) using real-time shear-wave elastography (SWE).

MATERIALS AND METHODS

This study included 31 patients with trapezius MPS and 31 volunteers. Sixty-one trapezius muscles (41 and 20 on the affected and non-affected side, respectively) of patients with MPS and 62 normal trapezius muscles in volunteers were assessed. Conventional ultrasonic parameters, including skeletal muscle thickness, resistance index (RI), and mean shear wave velocity (SWVmean) of trapezius muscles, were obtained in the seated position with the shoulders and neck relaxed. The daily neck leaning time (unit:hours) of all participants was obtained using a questionnaire.

RESULTS

Ultrasound showed no statistically significant differences in thickness or RI of the trapezius muscles of the affected and non-affected sides in MPS patients versus normal trapezius muscles (p = 0.976 and 0.106, respectively). In contrast, the SWVmean of trapezius muscles in patients with MPS was significantly higher than that of normal trapezius muscles in both the affected and non-affected sides (4.41 ± 1.02 m/s vs. 3.35 ± 0.79 m/s, p < 0.001; 4.05 ± 0.63 m/s vs. 3.35 ± 0.79 m/s, p = 0.002). There was no significant difference between the SWVmean of the trapezius muscles on the affected and non-affected sides in patients with MPS (4.41 ± 1.02 m/s vs. 4.05 ± 0.63 m/s, p = 0.225). Correlation analysis showed that daily neck forward time was positively correlated with the SWVmean of the trapezius muscles on the affected and non-affected sides in patients with MPS (r = 0.635, p < 0.001; r = 0.576, p = 0.008).

CONCLUSION

SWE can quantitatively evaluate stiffness of trapezius muscles in patients with trapezius MPS. The stiffness of both affected and non-affected trapezius muscles increased in patients with trapezius MPS, and the degree of increase positively correlated with the time of cervical forward leaning.

Specification of Neck Muscle Dysfunction through Digital Image Analysis Using Machine Learning

Everyone has or will have experienced some degree of neck pain. Typically, neck pain is associated with the sensation of tense, tight, or stiff neck muscles. However, it is unclear whether the neck muscles are objectively stiffer with neck pain. This study used 1099 ultrasound elastography images (elastograms) obtained from 38 adult women, 20 with chronic neck pain and 18 asymptomatic. For training machine learning algorithms, 28 numerical characteristics were extracted from both the original and transformed shear wave velocity color-coded images as well as from respective image segments. Overall, a total number of 323 distinct features were generated from the data. A supervised binary classification was performed, using six machine-learning algorithms. The random forest algorithm produced the most accurate model to distinguish the elastograms of women with chronic neck pain from asymptomatic women with an AUC of 0.898. When evaluating features that can be used as biomarkers for muscle dysfunction in neck pain, the region of the deepest neck muscles (M. multifidus) provided the most features to support the correct classification of elastograms. By constructing summary images and associated Hotelling's T² maps, we enabled the visualization of group differences and their statistical confirmation.

Assessment of the Ulnar Collateral Ligament of the Elbow Using Ultrasonic Shear Wave Elastography in Professional Baseball Players

BACKGROUND

Injury to the ulnar collateral ligament (UCL) of the elbow can cause chronic pain and loss of throwing ability. Ultrasonic shear wave elastography (SWE) is a new imaging method that can be used for quantitative assessment of tissue elasticity.

PURPOSE

To evaluate the properties of the UCL in professional baseball players using SWE.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

This study included 35 professional baseball players (mean age, 23.0 years) without elbow injuries. Both elbows of each player were examined using ultrasound, and comparisons between the dominant and nondominant arms were conducted. The thickness of the anterior bundle of the UCL at its midportion was measured in the resting position on ultrasound. We also measured the difference in the ulnohumeral joint space with and without gravity stress on the forearm. Tissue elasticity was evaluated using a built-in software program. The relationship between UCL elasticity and ultrasound findings was analyzed using the Pearson correlation coefficient.

RESULTS

The mean ± SD thickness of the UCL was significantly greater in the dominant arm versus the nondominant arm (6.0 ± 1.4 vs 5.3 ± 1.3 mm; P = .004). The mean joint space difference was significantly wider in the dominant arm as compared with the nondominant arm (0.81 ± 0.42 vs 0.52 ± 0.31 mm; P = .002), and the mean UCL elasticity was lower in the dominant arm than in the nondominant arm (34.9 ± 11.6 vs 43.3 ± 10.6 kPa; P = .002). UCL elasticity was negatively correlated with UCL thickness (r = -0.27; P = .02) and joint space difference (r = -0.34; P = .003).

CONCLUSION

In professional baseball players, the elbow UCL of the dominant arm demonstrated increased thickness, with a larger joint space gap on gravity stress and lower elasticity in SWE as compared with the nondominant arm. Greater medial joint laxity can be predicted by assessing the elasticity of the UCL using SWE.

Characteristics of Surface Electromyograph Activity of Cervical Extensors and Flexors in Nonspecific Neck Pain Patients: A Cross-Sectional Study

Background and Objectives: We identified typical surface electromyogram (sEMG) activities of the cervical extensors and flexors during motions in the three anatomical planes in healthy adults. The aim of this study was to explore characteristics of sEMG activities of these cervical muscles in nonspecific neck pain (NSNP) patients based on healthy adults. Materials and Methods: Participants were 24 NSNP patients (NSNP group, mean ± SD of age, 47.5 ± 15.5) and 24 healthy adults (control group, 20.5 ± 1.4). For each participant, sEMG of the cervical extensors and flexors was recorded during neck flexion, extension, bilateral lateral flexion, bilateral rotation, and at the neutral position in Phase I (the neck from the neutral position to the maximum range of motion), Phase II (at the maximum range of motion), and Phase III (from the maximum range of motion to the neutral position), yielding a total of 42 phases. A percentage of maximum voluntary contraction to normalize muscle activity in each phase was calculated to obtain the ratio of muscle activities in the extensors and flexors in each of 36 phases of the motions to the neutral position and ratio of the flexors to extensors in activity for 21 phases. Results: In 28 of 36 phases of the motions, the ratios of muscle activities in the extensors and flexors to the neutral position in the NSNP group were significantly larger than the control group (p < 0.05). In 6 of 21 phases, the ratios of the flexors to extensors in activity in the NSNP group were significantly larger than in the control group (p < 0.05). Conclusions: In NSNP patients, the activity of the cervical extensors and flexors associated with neck motion increased with an imbalance in activity between these muscles compared to their activity in healthy adults. The results of this study will be useful in understanding the pathogenesis of NSNP and in constructing an objective evaluation of the treatment efficacy on NSNP patients.

Effects of alternating heat and cold stimulation at different cooling rates using a wearable thermo device on shoulder muscle stiffness: a cross-over study

Background

A small, wearable thermo device that uses Peltier elements for programmed heat and cold stimulation has been developed recently and is expected to be applied in conventional contrast bath therapy. This study was aimed to examine improvements in trapezius muscle hardness and subjective symptoms resulting from alternating heat and cold stimulation, with different rates of cooling.

Methods

This cross-over study included four conditions. Twenty healthy young male individuals (age, 22.3 ± 4.5 years) participated in this study. These four interventions targeted the unilateral trapezius muscle of the dominant arm after a 15-min typing task. Specifically, heat and cold stimulations were applied at different ratios (the heating/cooling rate of 3:1, 3:2, and 3:3) or not applied. Each intervention was separated by at least one week. Skin temperature at the stimulation area was recorded using a data logger. Outcome measures included muscle hardness (measured using a portable tester) and subjective symptoms (muscle stiffness and fatigue). Each item was assessed at three time points: baseline, after typing, and after the intervention.

Results

Two-way analysis of variance with repeated measures found an interaction effect for muscle hardness between four conditions (3:1, 3:2, 3:3, and no) and three time points (p < 0.05). Only in the 3:1 condition were the post-intervention values lower than those after typing (p < 0.01). There was also an interaction effect for subjective muscle stiffness (p < 0.05); the values after the intervention in the 3:1 condition were lower than those after intervention in the no stimulation condition (p < 0.01). There was no significant relationship between changes in muscle hardness and changes in subjective symptoms in the 3:1 condition.

Conclusions

Our results demonstrate that alternating heat and cold stimulations with a different cooling rate could affect the degree of improvement in muscle hardness and subjective symptoms. In particular, the 3:1 condition has the possibility to improved muscle hardness within the condition and subjective muscle stiffness between conditions.

Trial registration

UMIN000040620. Registered 1 June 2020, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046359

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05623-z.

Clinical features of neck and shoulder pain (Katakori) in Japanese hospital workers

Background:

Non-specific pain or discomfort in the neck and shoulder girdle, called katakori in Japanese, is a common, chronic musculoskeletal condition worldwide. However, its various clinical features are incompletely characterized, even among medical professionals. We aimed to clarify factors affecting katakori and to investigate objectively the associated neck muscle stiffness and skeletal muscle volume.

Methods:

All staff members at our private hospital were surveyed about their lifestyle, physical and mental status, and katakori symptoms, using a self-administered questionnaire. Multiple logistic regression analysis was used to explore possible katakori risk factors. On secondary assessment, ultrasound elastography of the trapezius muscle as well as limb/trunk muscle mass were compared between subjects with severe symptoms and subjects without katakori, using propensity score matching.

Results:

Of 359 participants enrolled, nearly 75% had katakori to some degree. Spending time on a computer during work (adjusted odds ratio [aOR]: 1.82 for 3-6 hours, aOR: 2.48 for > 6 hours), being female (aOR: 3.75), and having unsatisfactory sleep (aOR: 2.92) were potential risk factors for katakori. Comparison of 13 matched pairs showed a significantly stiffer trapezius in subjects with severe katakori symptoms, but no apparent differences in limb/trunk muscle mass.

Conclusions:

Katakori was particularly prevalent in our hospital staff. Possible risk factors for disabling katakori were doing long-term computer work, being female, and having unsatisfactory sleep. Symptoms seem to be associated with elevated neck muscle stiffness. These findings could guide working condition improvements to mitigate katakori.

Scapular Dynamic Muscular Stiffness Assessed through Myotonometry: A Narrative Review

Several tools have been used to assess muscular stiffness. Myotonometry stands out as an accessible, handheld, and easy to use tool. The purpose of this review was to summarize the psychometric properties and methodological considerations of myotonometry and its applicability in assessing scapular muscles. Myotonometry seems to be a reliable method to assess several muscles stiffness, as trapezius. This method has been demonstrated fair to moderate correlation with passive stiffness measured by shear wave elastography for several muscles, as well as with level of muscle contraction, pinch and muscle strength, Action Research Arm Test score and muscle or subcutaneous thickness. Myotonometry can detect scapular muscles stiffness differences between pre- and post-intervention in painful conditions and, sometimes, between symptomatic and asymptomatic subjects.

Comparison of Surgeon Muscular Properties between Standard Operating Microscope and Digitally Assisted Vitreoretinal Surgery Systems

PURPOSE

To quantitatively analyze surgical ergonomics between standard operating microscope (SOM) and digitally assisted vitreoretinal surgery (DAVS) systems.

METHODS

The surgeon conducted procedures on 110 patients; 52 patients underwent a combined phacoemulsification and pars plana vitrectomy (Phaco-PPV group, 24 using SOM and 28 using DAVS), and 58 patients underwent phacoemulsification (Phaco group, 30 using SOM and 28 using DAVS). The surgeon's muscle tone and stiffness in the sternocleidomastoid (SCM) and the two positions of the upper trapezius (UT), which are 2 cm intervals along the UT muscle fibers, UT1 and UT2, were measured at preoperative, intraoperative, and postoperative time points.

RESULTS

In the Phaco-PPV group using the SOM, intraoperative muscle tone and stiffness were higher than pre- and postoperative values in the SCM (P<0.001, respectively), UT1 (P<0.001, respectively), and UT2 (P<0.001 and P<0.01, respectively). In the Phaco group using the SOM, intraoperative muscle tone and stiffness were higher than pre- and postoperative values in the SCM (P<0.001, respectively) and UT1 (P<0.001 and P<0.01, respectively). By contrast, when the surgeon used the DAVS, there were no differences in muscle properties at any measurement site or during any time point in the Phaco-PPV and Phaco groups (P>0.05).

CONCLUSIONS

This study provides quantitative measurement of retina surgeon ergonomics, suggesting that compared with a SOM, the DAVS can reduce intraoperative muscle fatigue.

Effects of alternating heat and cold stimulation using a wearable thermo-device on subjective and objective shoulder stiffness

BACKGROUND

Technological innovations have allowed the use of miniature apparatus that can easily control and program heat and cold stimulations using Peltier elements. The wearable thermo-device has a potential to be applied to conventional contrast bath therapy. This study aimed to examine the effects of alternating heat and cold stimulation (HC) using a wearable thermo-device on subjective and objective improvement of shoulder stiffness.

METHODS

Twenty healthy young male individuals (20.3 ± 0.6 years) participated in this study. The interventions were randomly conducted under four conditions, including HC, heat stimulation, cold stimulation, and no stimulation on their bilateral trapezius muscle, after a 30-min typing task. Each intervention was administered at least 1 week apart. The analyzed limb was the dominant arm. Muscle hardness was assessed using a portable muscle hardness meter, as well as the skin temperature over the stimulated area. After each condition, the participants were asked for feedback regarding subjective improvement in refreshed feelings, muscle stiffness, and muscle fatigue using an 11-point numerical rating scale.

RESULTS

With regard to muscle hardness, only the HC condition significantly decreased from 1.43 N to 1.37 N (d = 0.44, p < 0.05). Additionally, reduced muscle hardness in HC condition was associated with the degree of skin cooling during the intervention (cold max: r = 0.634, p < 0.01; cold change: r = -0.548, p < 0.05). Subjective improvement in refreshed feelings, muscle stiffness, and muscle fatigue was determined in the HC and heat stimulation conditions compared with the no stimulation condition (p < 0.01 and p < 0.05, respectively). Moreover, the HC condition showed significantly greater improvements in muscle stiffness and fatigue compared to the cold stimulation condition (p < 0.05).

CONCLUSIONS

The current study demonstrated that HC promoted not only better subjective symptoms, such as muscle stiffness and fatigue, but also lesser muscle hardness. Furthermore, an association was observed between the degree of skin temperature cooling and reduced muscle hardness during HC. Further investigations on the ratio and intensity of cooling should be conducted in the future to establish the optimal HC protocol for muscle stiffness or fatigue.

TRIAL REGISTRATION

UMIN000040620 . Registered 1 June 2020.

Convergent Validity and Test-Retest Reliability of Multimodal Ultrasonography and Related Clinical Measures in People With Chronic Stroke

OBJECTIVE

To assess the test-retest reliability of diagnostic ultrasonography measurements of the bilateral biceps brachii (BB), brachial artery, medial gastrocnemius (MG), and popliteal artery in survivors of stroke and their convergent validity with related clinical comparators.

DESIGN

Cross-sectional study.

SETTING

All procedures were conducted in a university laboratory.

PARTICIPANTS

Sixty-five community dwelling adults (N=65; 26 women, 39 men) with an average age of 60.9±7.7 years and stroke duration of 5.7±3.9 years participated in this study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Measures of muscle structure (ie, thickness, cross-sectional area, fascicle length, pennation angle), stiffness, and intramuscular blood perfusion were conducted using B-mode, elastography and color flow Doppler ultrasonography modes, respectively. Convergent validity was assessed by examining correlations between ultrasonography measures and assessments of related constructs (ie, dynamic stiffness, isometric peak torque, spasticity, and systemic vascular function using myotonometry, dynamometry, the Composite Spasticity Scale, and the Ankle-Brachial Index, respectively). A 2-way random-effects intraclass correlation coefficient (ICC) model (ICC_2,3) was used to determine agreement between intersession measures among a smaller cohort of participants with stroke (n=20).

RESULTS

ICC estimates ranged from moderate to excellent for muscle stiffness (paretic: ICC=0.74-0.89; nonparetic: ICC=0.66-0.88), structure (paretic: ICC=0.87-0.99; nonparetic: ICC=0.81-0.98), and blood perfusion measures (paretic: ICC=0.74-0.84; nonparetic: ICC=0.73-0.88). Weak to moderate associations were found between myotonometry and elastography measures of the bilateral BB (r=0.29-0.52, P≤.05) and MG muscles (r=0.31-0.69, P≤.05). The correlations between elastography measures and spasticity scores for the paretic upper (r=0.35-0.63, P≤.05) and lower limbs (r=0.25-0.37, P≤.05) were also weak to moderate.

CONCLUSIONS

Elastography demonstrated mostly weak to moderate correlation with measures of stiffness using myotonometry as well as scores of paretic upper and lower limb spasticity. The results also indicate acceptable intersession reliability for muscle and vascular measures using several ultrasonography modalities among individuals with chronic stroke.

Quantitative assessment of normal middle deltoid muscle elasticity at various arm abduction using ultrasound shear wave elastography

The objective of this study is to assess the change in the normal MD elasticity using shear wave elastography (SWE) through measuring the middle deltoid (MD) elasticity in healthy participants at various arm abduction (with bilateral arms at 0 degrees abduction and 90 degrees active abduction) and analyzing the factors affecting normal MD elasticity. Mean shear wave velocity (SWV) of the MD in healthy right-handed participants were evaluated using SWE at different arm abduction, and potential factors (gender, MD thickness, age, body mass index) affecting MD elasticity were analyzed. Different arm abduction positions of each participant were as follows: (i) 0° abduction of bilateral arm (L0° and R0°), (ii) 90° active abduction of bilateral arm (L90° and R90°). Mean SWV was significantly higher at L90° than L0°, higher at R90° than R0°, higher at R0° than L0°, and higher at R90° than L90° (all P < 0.0001). SWV was significantly higher in males at both L0° (P < 0.05) and R0° (P < 0.01) than in females. Neither MD thickness, age nor body mass index influenced MD elasticity. Reference ranges of normal MD elasticity were 2.4–3.1 m/s in males and 2.2–2.9 m/s in females at L0° and 2.5–3.3 m/s in males and 2.4–3.2 m/s in females at R0°, and were 4.9–6.7 m/s at L90°, 5.2–7.1 m/s at R90° for both males and females. SWE is a feasible technique to assess normal MD elasticity at various arm abduction. Our results suggest that normal MD elasticity at L0°, R0°, L90°, and R90° with SWE are different. Moreover, these reference ranges may serve as quantitative baseline measurements for assessment of normal MD elasticity in the future.

Reliability of Trapezius Muscle Hardness Measurement: A Comparison between Portable Muscle Hardness Meter and Ultrasound Strain Elastography

Prolonged computer work and smartphone use can cause stiffness of the neck and shoulder muscles, including the trapezius muscle. Hence, muscle hardness quantification is clinically beneficial. The present study aimed to examine the reliability of trapezius muscle hardness measurement using a portable muscle hardness meter and ultrasound strain elastography. Overall, 20 healthy young men participated in this study. Prior to measurement, the participant’s subjective symptoms, particularly shoulder muscle stiffness, were rated using an 11-point verbal scale. Furthermore, hardness of the right and left upper trapezius muscles was assessed. In the strain elastography assessment, muscle hardness was evaluated using strain ratio. Results showed that, in quantifying upper trapezius muscle hardness, both portable muscle hardness meter and strain elastography had an excellent intra-tester reliability (>0.9). However, the correlation coefficients between muscle hardness values assessed using a muscle hardness meter and those evaluated with strain elastography did not significantly differ, and the scores for subjective shoulder stiffness did not correspond to muscle hardness values. Therefore, the hardness of the trapezius muscle does not directly reflect the subjective shoulder stiffness. Future studies should thoroughly examine the location of the shoulder stiffness, and check whether it is accompanied by local pain or tenderness.

Biceps brachii muscle hardness assessed by a push-in meter in comparison to ultrasound strain elastography

This study investigated the relationship between push-in meter (PM) and ultrasound strain elastography (USE) for biceps brachii (BB) muscle hardness. BB hardness of 21 young men was assessed by PM and USE during rest and isometric contractions of six different intensities (15, 30, 45, 60, 75, 90% of maximal voluntary contraction: MVC) at 30°, 60° and 90° elbow flexion. Muscle hardness (E) was calculated from the force-displacement relationship in PM, and strain ratio (SR) between an acoustic coupler (elastic modulus: 22.6 kPa) and different regions of interest (ROIs) in BB was calculated and converted to Young's modulus (YM) in USE. In resting muscle, E was 26.1 ± 6.4 kPa, and SR and YM for the whole BB was 0.88 ± 0.4 and 30.8 ± 12.8 kPa, respectively. A significant (p < 0.01) correlation was evident between E and logarithmical transformed SR (LTSR) for the ROI of whole BB (r = - 0.626), and E and converted YM (r = 0.615). E increased approximately ninefold from resting to 90% MVC, and E and LTSR (r = - 0.732 to - 0.880), and E and converted YM for the SR above 0.1 were correlated (r = 0.599-0.768, p < 0.01). These results suggest that muscle hardness values obtained by PM and USE are comparable.

Determination of reference ranges for normal upper trapezius elasticity during different shoulder abduction using shear wave elastography: a preliminary study

The purpose of this study was to determine the reference ranges of normal upper trapezius (UT) elasticity during different shoulder abduction using shear wave elastography (SWE). Mean shear wave velocity (SWV) of UT elasticity in eighty healthy participants were measured at left and right shoulder 0° abduction and 90° passive abduction (L0°, R0°, L90°, R90°) with SWE. The effects of potential factors (gender, UT thickness, age, and body mass index) on UT elasticity were analyzed. The reference ranges of normal UT elasticity were calculated by using the normal distribution method. UT elasticity was significantly different among various shoulder abduction (P < 0.0001). UT elasticity was significantly higher in males at both L90° (P < 0.05) and R90° (P < 0.01) than in females. The reference ranges of normal UT elasticity were 2.90-4.01 m/s at L0° and 3.01-4.29 m/s at R0°, and were 4.90-6.40 m/s in males and 4.40-6.20 m/s in females at L90°, 5.20-7.02 m/s in males and 4.71-6.80 m/s in females at R90°. Our results suggest that gender should be considered when determining the reference ranges of normal UT elasticity at L90° and R90° with SWE. These values may provide quantitative baseline measurements for the assessment of UT muscle strain in the future.

Detection of early changes in the muscle properties of the pectoralis major in breast cancer patients treated with radiotherapy using a handheld myotonometer

OBJECTIVE

The primary aim was to investigate serial changes in the mechanical properties of the pectoralis major (PM), upper trapezius (UT), and sternoclavicular mastoid muscle (SCM) in breast cancer patients undergoing radiotherapy (RT) using a hand-held myotonometer. The secondary aims were to determine changes in subjective symptoms and to identify correlation with subjective results.

DESIGN

A total of 42 breast cancer patients were enrolled in this longitudinal prospective study. Muscle properties of the PM, UT, and SCM were evaluated before RT, immediately after RT, and 4 months post-RT. Subjective symptom scales of pain and stiffness at rest/stretch of each muscle were evaluated.

RESULTS

The PM showed significant side-to-side differences; the affected PM showed increased tone, stiffness, and decreased elasticity compared with the unaffected PM. The affected PM and UT showed significant time-dependent interactions. Stiffness of the affected PM at stretching was significantly higher 4 months post-RT than baseline. Only the tone and elasticity of the affected PM were correlated with subjective symptoms.

CONCLUSION

In breast cancer patients who received RT after surgery, increased tone, stiffness, and decreased elasticity were observed in the affected PM compared with the unaffected side, which sustained four months post-RT. Change in muscle properties immediately after RT preceded subjective stiffness, which worsened significantly 4 months post-RT compared with baseline.

Eccentric Exercise Reduces Upper Trapezius Muscle Stiffness Assessed by Shear Wave Elastography and Myotonometry

In this study, we tested the hypotheses that unaccustomed eccentric exercise (ECC) would reduce the elastic modulus and dynamic stiffness of the upper trapezius muscle and that these changes would correlate with increases in muscle thickness, reflecting muscle edema. Shear wave elastography was used to measure elastic modulus, dynamic stiffness was assessed using myotonometry, and muscle thickness was measured using ultrasonography. All measurements were performed at four locations over the upper trapezius before and 24 h after a single bout of ECC. Fourteen healthy participants (11 males and 3 females; 23.2 ± 3.0 years; height 175.1 ± 10.4 cm; body mass 73.8 ± 11.3 kg) took part in the study. Overall, ECC resulted in decreased elastic modulus (from 45.8 ± 1.6 to 39.4 ± 1.2 kPa, p < 0.01) and dynamic muscle stiffness (from 369.0 ± 7.3 to 302.6 ± 6.0 N/m, p < 0.01). Additionally, ECC resulted in increased muscle thickness (from 6.9 ± 0.4 to 7.3 ± 0.4 mm, p < 0.01). Spatial changes (across the four locations) were found for elastic modulus, stiffness and thickness. No significant correlations were found between changes in measures of muscle stiffness, or between changes in stiffness and changes in thickness. In conclusion, the present pilot study showed that ECC altered biomechanical muscle properties, reflected by decreased elastic modulus and dynamic muscle stiffness 24 h after ECC.

Eccentric Training Changes the Pressure Pain and Stiffness Maps of the Upper Trapezius in Females with Chronic Neck-Shoulder Pain: A Preliminary Study

OBJECTIVE

Between 50% and 67% of adults suffer from neck-shoulder pain, which may be associated with increased stiffness of neck muscles. We assessed pressure pain sensitivity and muscle stiffness maps of the upper trapezius in female computer users with and without chronic neck-shoulder pain and investigated the effects of eccentric training on females with neck-shoulder pain.

DESIGN

Cross-sectional (part 1) and open-label (part 2) study.

SETTING

University.

SUBJECTS

Twenty females with neck-shoulder pain were compared with 20 controls (part 1). In part 2, neck-shoulder pain participants followed a five-week unilateral upper trapezius eccentric training program.

METHODS

Topographical maps of pressure pain thresholds (pressure algometer) and muscle stiffness (myotonometer), using a 15-point grid covering myotendinous and muscle belly sites, and shoulder elevation force and range of elevation (dynamometer) were assessed at baseline and after training.

RESULTS

There were no differences in pressure pain thresholds between sites (P = 0.243) or groups (P = 0.068), and there were significant differences in stiffness between myotendinous and muscle belly sites (P < 0.001) but not groups (P = 0.273). After training, pressure pain thresholds increased, stiffness decreased (P < 0.005), and shoulder elevation force and range of elevation improved (P < 0.001).

CONCLUSIONS

The lack of differences in upper trapezius pressure pain sensitivity and stiffness between females with or without neck-shoulder pain confirms no clear etiology among computer users reporting neck-shoulder pain. A five-week eccentric training protocol showed positive effects on pressure pain sensitivity, stiffness, shoulder force, and range of motion.

Relationship between trapezius muscle hardness and transverse cervical artery flow in association with neck and upper-back stiffness

Neck and upper-back stiffness is a common discomfort encountered occasionally in daily life among otherwise healthy subjects. The pathogenesis of this condition could be attributable to increased tension in muscles such as the trapezius muscle (TM). The transverse cervical artery (TCA) is one of the feeding arteries for the TM, and TCA flow is reportedly related to symptoms of neck and upper-back stiffness. This study quantitatively investigated relationships between TM hardness and TCA hemodynamics as evaluated on Doppler sonography. Questionnaires regarding neck and upper-back stiffness, muscle hardness measurements obtained using a muscle hardness meter and examinations of TCA hemodynamics using Doppler sonography were performed on 55 healthy young adults (25 males, 30 females; mean age, 22 ± 2 years). Subjects displaying neck and upper-back stiffness actually exhibited high muscle hardness (median, 14.0; interquartile range (IQR), 12.9-18.0) compared to those without the symptom (median, 12.0; IQR, 9.9-14.0; p = .002). Peak systolic velocity in the TCA on Doppler sonography was lower in subjects with the symptom (median, 65.1 cm/s; IQR 59.6-72.5 cm/s) than in those without the symptom (median, 72.5 cm/s; IQR 66.5-84.2 cm/s; p = .012). Resistive index in the TCA was high (r²  = .605, p = .014) with increasing TM hardness, particularly among male subjects with the symptom. The present study suggests that high resistance and low blood flow velocity in the TCA could be closely associated with the underlying pathogenesis of neck and upper-back stiffness.

Systematic Review of Instrumented Measures of Skeletal Muscle Mechanical Properties: Evidence for the Application of Shear Wave Elastography with Children

The aim of this review was to identify instrumented devices that quantify skeletal muscle mechanical properties and to evaluate their potential clinical utility and clinimetric evidence with respect to children. Four databases were searched to identify articles reporting original clinimetric data for devices measuring muscle stiffness or elastic modulus, along a muscle's main fibre direction. Clinimetric evidence was rated using the Consensus-Based Standard for the Selection of Measurement Instruments (COSMIN) checklist. Sixty-five articles provided clinimetric data for two devices meeting our criteria: the Aixplorer and the Acuson. Both are shear wave elastography devices that determine the shear modulus of muscle tissue. The Aixplorer had strong construct validity and reliability, and the Acuson, moderate construct validity and reliability. Both devices have sound clinical utility with non-invasive application at various joint positions and data acquisition in real time, minimizing fatigue. Further research is warranted to evaluate utility for children with specific disorders of abnormal muscle structure or function.

The Effect of Strength Training on Vastus Lateralis' Stiffness: An Ultrasound Quasi-Static Elastography Study

Ultrasound imaging allows the evaluation of musculoskeletal morphology and function. Ultrasound elastography can also offer semi-quantitative and/or quantitative assessment of tissue stiffness providing relevant information about adaptations of skeletal muscle mechanical properties. In this study we aimed to explore the feasibility of elastography ultrasound imaging in assessing the effect of strength training on vastus lateralis stiffness. Twenty-eight young male adults were separated in a control (n = 9) and strength-training (n = 20) groups. The strength-training group completed 15 weeks of either concentric (n = 10) or eccentric (n = 10) isokinetic training of the knee extensors. Ultrasound scans of the vastus lateralis for quasi-static elastography were collected. All image acquisitions and measurements were done by the same experienced sonographer. After 15 weeks, knee maximal extension isometric torque increased in the strength-training groups. After strength training, there was a decrease in the amount of red pixels in vastus lateralis region of interest [F_(1,18) = 25.490; p < 0.001; η² = 0.586], whereas the amount of green and blue pixels increased F_(1,18) = 17.179; p < 0.01; η² = 0.488; F_(1,18) = 6.522; p < 0.05; η² = 0.266], suggesting higher vastus lateralis stiffness. We conclude that concentric and eccentric strength training increases skeletal muscle stiffness, which can be evaluated by quasi-static elastography. Ultrasound elastography is suitable for non-invasive evaluation of skeletal muscle functional adaptations, which can be of importance for sports medicine and in designing optimal training and rehabilitation programs.

Thigh musculature stiffness during active muscle contraction after anterior cruciate ligament injury

Background

Altered motor unit (MU) activity has been identified after anterior cruciate ligament (ACL) injury, but its effect on muscle tissue properties is unknown. The purpose of this study was to compare thigh musculature muscle stiffness between control and ACL-injured subjects.

Methods

Thirty ACL-injured subjects and 25 control subjects were recruited. Subjects completed a randomized protocol of isometric contractions while electromyography (EMG) signals were recorded. Three maximum voluntary isometric contractions (MVIC) determined peak force for 10 and 25% MVIC trials. Shear wave elastography was captured during each 10 and 25% MVIC trials.

Results

Differences in muscle stiffness were assessed between limbs and groups. 12 months post-surgery had higher stiffness for VM 0% MVIC, VL 0 and 10% MVIC, and ST 10 and 25% MVIC (all p ≤ 0.04).

Conclusion

Thigh musculature stiffness changed throughout rehabilitation and remained altered at 12 months after ACL reconstruction.

Neck Muscle Stiffness Measured With Shear Wave Elastography in Women With Chronic Nonspecific Neck Pain

OBJECTIVE

Utilizing shear wave elastography, we compared the stiffness of the neck extensor muscles and the stiffness in muscle-specific regions between women with chronic nonspecific neck pain and asymptomatic controls.

DESIGN

Cross-sectional observational study.

METHODS

We measured the average muscle stiffness over multiple neck extensor muscles and in regions corresponding approximately to the trapezius, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles using ultrasound shear wave elastography in 20 women with chronic nonspecific neck pain and 18 asymptomatic women during multiple tasks. The measurements were automatically quality controlled and computer processed over the complete visible neck region or a large muscle-specific region.

RESULTS

Pooled over all tasks, neck muscle stiffness was not significantly different between those with neck pain and asymptomatic controls (neck pain median, 11.6 kPa; interquartile range, 8.9 kPa and control median, 13.3 kPa; interquartile range, 8.6 kPa; P = .175). The measure of neck muscle stiffness was not correlated with the intensity of neck pain or perceived disability.

CONCLUSION

Shear wave elastography revealed similar muscle stiffness in people with and without chronic neck pain, despite the sensation of increased neck stiffness in those with chronic neck pain. Therapeutic interventions aiming to reduce neck muscle tone are often based on the assumption that perceived neck stiffness corresponds to objective muscle stiffness. The current results question this assumption. J Orthop Sports Phys Ther 2020;50(4):179-188. Epub 6 Jan 2020. doi:10.2519/jospt.2020.8821.

Mechanical Properties of Muscles around the Shoulder in Breast Cancer Patients: Intra-rater and Inter-rater Reliability of the MyotonPRO

BACKGROUND

Patients with breast cancer typically experience changes in the properties of muscles around the shoulder. However, there is no appropriate evaluation tool for these changes.

OBJECTIVE

The primary objective was to investigate the inter-rater and intra-rater reliability of muscle-related parameters measured by the MyotonPRO, a myotonometer device. The secondary objective was to investigate differences in properties of muscle around the shoulder between the mastectomy side and the other side.

DESIGN

Cross-sectional reliability study.

SETTING

Outpatient clinic in a tertiary care university-affiliated hospital.

PARTICIPANTS

Twenty-two patients with breast cancer who underwent mastectomy.

METHODS

Muscle tone, stiffness, and elasticity of the pectoralis major (PM), sternocleidomastoid (SCM), and upper trapezius (UT) were measured using the MyotonPRO. Rater 1 performed two sets of measurements with a time interval of 30 minutes to determine intra-rater reliability. Rater 2 performed measurements during the interval between the two sets of rater 1. Reliability was assessed using intraclass correlation coefficients (ICCs) and Bland-Altman analysis. A paired t-test was used to compare muscle properties between the affected and unaffected sides.

MAIN OUTCOME MEASUREMENTS

Frequency (tone, Hz), stiffness (N/m), and decrement (elasticity).

RESULTS

Intra-rater reliability was excellent (ICC > 0.75, 0.85-0.98) for all parameters of the PM, SCM, and UT in the affected and unaffected upper limbs of patients with breast cancer. Inter-rater reliability was fair to excellent for all parameters except unaffected PM elasticity (ICC = 0.34). There were significant differences in all parameters of the PM between the affected and unaffected sides. There were no significant differences in the parameters of the SCM and UT between the two sides.

CONCLUSIONS

Our findings indicate that the MyotonPRO device is a feasible tool to quantify PM, UT, and SCM muscle properties (stiffness, tone, and elasticity) in patients with breast cancer.

LEVEL OF EVIDENCE

III.

Modulation in Elastic Properties of Upper Trapezius with Varying Neck Angle

Background

Neck and shoulder complaints caused by poor posture may influence upper trapezius stiffness. The relationship between the shear elastic modulus of the upper trapezius and cervical flexion angles is unknown. Therefore, it is essential to assess upper trapezius stiffness during cervical flexion. The objectives of this study were to (1) determine the intra- and interoperator reliabilities of evaluating upper trapezius stiffness and calculate the minimal detectable change (MDC); (2) examine the elastic modulus alterations of the upper trapezius during cervical flexion; and (3) explore the difference of upper trapezius stiffness between the dominant and nondominant sides.

Methods

Twenty healthy male participants were recruited in this study. The shear modulus of the upper trapezius was evaluated by two independent investigators using shear wave elastography (SWE) during cervical flexion at 0° and 50°.

Findings

The intraoperator (intraclass correlation coefficient (ICC) = 0.85–0.86) and interoperator (ICC = 0.94–0.98) reliabilities for measuring the shear elastic modulus of the upper trapezius during the cervical flexion ranged from good to excellent. An increase of 35.58% in upper trapezius stiffness was found at 0° to 50° of cervical flexion, and the MDC was 7.04 kPa. In addition, a significant difference was obtained in the elastic modulus of the upper trapezius muscle between the dominant and nondominant sides (P < 0.05).

Conclusions

Our findings revealed that SWE could quantify the elastic modulus of the upper trapezius and monitor its changes. Therefore, further studies are required to delineate the modulation in upper trapezius muscle stiffness among subjects with neck and shoulder pain.

Change in muscle hardness after trigger point injection and physiotherapy for myofascial pain syndrome

Assessment and treatment of masticatory myofascial pain syndrome (MPS) are not standardized and remain controversial. We examined whether muscle hardness was useful for evaluating masticatory MPS and analyzed the effectiveness of treatments such as stretching and massage (SM) and trigger point injection (TPI). Twenty healthy volunteers and 20 MPS patients were enrolled. MPS patients were divided into TPI and SM treatment groups. Hardness of masticatory muscle with a taut band (TB) and change in hardness were evaluated after SM and TPI treatments. Hardness values were significantly higher in muscle including a TB (TB point) than in the muscle of healthy controls. Visual analogue scale scores were significantly lower after SM and TPI treatments, and hardness of the TB point was significantly lower after SM but not after TPI. These results suggest that measurement of muscle hardness, including the TB, is useful for evaluating masticatory MPS. However, TPI analgesia might not be caused by change in muscle hardness. The mechanisms underlying the effects of SM and TPI on reducing pain in MPS may differ and thus warrant further research.

Assessing the elastic properties of skeletal muscle and tendon using shearwave ultrasound elastography and MyotonPRO

The purposes of this study were to compare Young’s modulus values determined by shear wave ultrasound elastography (SWUE) with stiffness index obtained using a hand-held MyotonPRO device on the resting stiffness of gastrocnemius muscle belly and Achilles tendon; and to examine the test-retest reliability of those stiffness measurement using hand-held MyotonPRO. Twenty healthy volunteers participated in the study. The measurement values of muscle and tendon was determined in dominant legs. Each marker point was assessed using MyotonPRO and SWUE, respectively. Intra-operator reliability of MyotonPRO was established in 10 of the subjects. The correlation coefficients between the values of muscle and tendon stiffness indices determined by MyotonPRO and SWUE were calculated. Significant correlations were found for muscle and tendon stiffness and Young’s modulus ranged from 0.463 to 0.544 (all P < 0.05). The intra-operator reliability ranged from good to excellent (ICC_(3,1) = 0.787~0.928). These results suggest that the resting stiffness of gastrocnemius muscle belly and Achilles tendon measured by MyotonPRO is related to the Young’s modulus of those quantified by SWUE. The MyotonPRO shows good intra-operator repeatability. Therefore, the present study shows that MyotonPRO can be used to assess mechanical properties of gastrocnemius muscle belly and Achilles tendon with a resting condition.

Muscle stiffness in tension-type headache patients with pericranial tenderness

Background:

Tension-type headache patients have previously been shown to have increased muscle tone, stiffness and tenderness in the trapezius muscle compared to healthy volunteers. Shear wave elastography is a non-invasive method to measure muscle stiffness. The aim of the study was to use shear wave elastography to investigate if tension-type headache patients had increased pericranial muscle stiffness and whether pericranial muscle stiffness correlated to muscle tenderness.

Methods:

Seventeen patients with very frequent or chronic tension-type headache associated with pericranial tenderness and 29 healthy volunteers were included. Muscle stiffness was measured using shear wave elastography and muscle tenderness was measured using local tenderness score and total tenderness score.

Results:

There was no statistically significant difference in muscle stiffness between tension-type headache patients and healthy volunteers. The local tenderness and total tenderness scores were higher in tension-type headache patients compared with healthy volunteers. There was no correlation between muscle stiffness and tenderness.

Conclusion:

We found no sign of increased pericranial muscle stiffness in tension-type headache patients compared with healthy volunteers using shear wave elastography. Our findings do not suggest a generalized pericranial increase in muscle tone in very frequent and chronic tension-type headache patients.

Shear wave sonoelastography of skeletal muscle: basic principles, biomechanical concepts, clinical applications, and future perspectives

Imaging plays an important role in the diagnosis and therapeutic response evaluation of muscular diseases. However, one important limitation is its incapacity to assess the in vivo biomechanical properties of the muscles. The emerging shear wave sonoelastography technique offers a quantifiable spatial representation of the viscoelastic characteristics of skeletal muscle. Elastography is a non-invasive tool used to analyze the physiologic and biomechanical properties of muscles in healthy and pathologic conditions. However, radiologists need to familiarize themselves with the muscular biomechanical concepts and technical challenges of shear wave elastography. This review introduces the basic principles of muscle shear wave elastography, analyzes the factors that can influence measurements and provides an overview of its potential clinical applications in the field of muscular diseases.

Assessing the viscoelastic properties of upper trapezius muscle: Intra- and inter-tester reliability and the effect of shoulder elevation

BACKGROUND

Increasing stiffness in the upper trapezius muscle may contribute to imbalance of scapular motion, and result in shoulder and neck discomfort during shoulder flexion. Therefore, it is essential to quantify upper trapezius stiffness in various shoulder positions in order to aid in the prevention of these disorders and to optimize rehabilitation.

OBJECTIVES

The objectives of the present study were to examine the intra and inter-tester reliability of MyotonPRO device in measuring upper trapezius stiffness and its ability to determine changes in stiffness during shoulder flexion.

METHODS

Twenty healthy male subjects (mean age: 28.3±4.8 years) were studied. The stiffness of upper trapezius was quantified using the MyotonPRO device.

RESULTS

The results revealed excellent intra and inter-tester reliability for measuring upper trapezius stiffness with the shoulder in a neutral position, and also found a 14.2% increase in stiffness upon shoulder flexion between 0° and 60° of flexion. Minimal detectable change (MDC) was 26.3 N/m.

CONCLUSIONS

Our findings indicate that MyotonPRO device is a feasible tool to quantify upper trapezius stiffness as well as changes in muscle stiffness. Thus, it is important to assess the changes in upper trapezius muscle stiffness due to pathology or treatments for future studies.

Shear wave velocity measurement of upper trapezius muscle by color Doppler shear wave imaging

PURPOSE

Skeletal muscle stiffness is thought to be the result of increased tissue hardness, but measurement accuracy has been dependent on operator technique. We have proposed a novel shear wave real-time imaging method (color Doppler shear wave imaging: CD SWI) with continuous shear waves excited from the tissue surface by a mechanical vibrator.

METHODS

Using the method, shear wave velocity was measured for the upper trapezius muscle. Adaptive shear wave velocity measurement by means of quality estimation of shear wave wavefront was adopted. We recruited 23 male volunteers with no history of orthopedic disease and recorded shear wave propagation to assess the intra- and inter-observer reliability. For intra-observer reliability, one observer took two measurements separated by a time delay, and the intra-class correlation coefficient (ICC) was calculated (1,1). For inter-observer reliability, ICC (2,1) was calculated from both observers' measurements.

RESULTS

Mean propagation speed was 3.75 ± 0.47 (first) and 3.71 ± 0.49 m/s (second) for Observer A (ICC (1,1) = 0.91 [95% CI 0.76-0.96]) and 3.80 ± 0.53 m/s for Observer B (ICC (2,1) = 0.83 [95% CI 0.56-0.94]).

CONCLUSIONS

This result suggests that our technique is satisfactorily reliable and has potential for future application in various fields, such as evaluation of muscle condition or the effects of rehabilitation.

Comparison of shear wave velocity measurements assessed with two different ultrasound systems in an ex-vivo tendon strain phantom

OBJECTIVE

The purpose of this study is to compare the reliability of SW velocity measurements of two different ultrasound systems and their correlation with the tangent traction modulus in a non-static tendon strain model.

MATERIALS AND METHODS

A bovine tendon was fixed in a custom-made stretching device. Force was applied increasing from 0 up to 18 Newton. During each strain state the tangent traction modulus was determined by the stretcher device, and SW velocity (m/s) measurements using a Siemens S3000 and a Supersonic Aixplorer US machine were done for shear modulus (kPa) calculation.

RESULTS

A strong significant positive correlation was found between SW velocity assessed by the two ultrasound systems and the tangent traction modulus (r = 0.827-0.954, p < 0.001), yet all SW velocity-based calculations underestimated the reference tissue tangent modulus. Mean difference of SW velocities with the S3000 was 0.44 ± 0.3 m/s (p = 0.002) and with the Aixplorer 0.25 ± 0.3 m/s (p = 0.034). Mean difference of SW velocity between the two US-systems was 0.37 ± 0.3 m/s (p = 0.012).

CONCLUSION

In conclusion, SW velocities are highly dependent on mechanical forces in the tendon tissue, but for controlled mechanical loads appear to yield reproducible and comparable measurements using different US systems.

Quantitative assessment of rotator cuff muscle elasticity: Reliability and feasibility of shear wave elastography

Ultrasound imaging has been used to evaluate various shoulder pathologies, whereas, quantification of the rotator cuff muscle stiffness using shear wave elastography (SWE) has not been verified. The purpose of this study was to investigate the reliability and feasibility of SWE measurements for the quantification of supraspinatus (SSP) muscle elasticity. Thirty cadaveric shoulders (18 intact and 12 with torn rotator cuff) were used. Intra- and inter-observer reliability was evaluated on an established SWE technique for measuring the SSP muscle elasticity. To assess the effect of overlying soft tissues above the SSP muscle, SWE values were measured with the transducer placed on the skin, on the subcutaneous fat after removing the skin, on the trapezius muscle after removing the subcutaneous fat, and directly on the SSP muscle. In addition, SWE measurements on 4 shoulder positions (0°, 30°, 60°, and 90° abduction) were compared in those with/without rotator cuff tears. Intra- and inter-observer reliability of SWE measurements were excellent for all regions in SSP muscle. Also, removing the overlying soft tissue showed no significant difference on SWE values measured in the SSP muscle. The SSP muscle with 0° abduction showed large SWE values, whereas, shoulders with large-massive tear showed smaller variation throughout the adduction-abduction positions. SWE is a reliable and feasible tool for quantitatively assessing the SSP muscle elasticity. This study also presented SWE measurements on the SSP muscle under various shoulder abduction positions which might help characterize patterns in accordance to the size of rotator cuff tears.