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

Age-Related Changes in Shear Wave Elastography Parameters of the Gastrocnemius Muscle in Association with Physical Performance in Healthy Adults

BACKGROUND/AIMS

to investigate new indicators for early recognition of physical performance decline. Shear wave elastrography, a new ultrasound technique, was discussed in this study.

METHODS

Gastrocnemius muscle thickness and muscle stiffness were detected by traditional ultrasound and shear wave elastrography in 108 Chinese aged 20-85 years, and then analyzed with physical performance together.

RESULTS

After 70 years old, the decline rate of muscle stiffness under contractive state was significantly faster than that of muscle thickness, muscle relaxed stiffness, and physical performance indicators. The correlation analysis showed that gastrocnemius contractive stiffness was positively related with handgrip strength, step length, and fast gait speed after adjusted by age and gender. Among physical performance variants, step length had closer relationship with muscle strength than repeated chair stands.

CONCLUSIONS

The detection of gastrocnemius muscle by shear wave elastography reflected the change of lower-limb muscle stiffness with aging. Muscle contractive stiffness and step length measurement supplied novel ways for muscle performance and motor function assessment.

Influence of transducer orientation on shear wave velocity measurements of the iliotibial band

Tissue anisotropy influences estimation of mechanical properties of connective tissues, such as the iliotibial band (ITB). This study investigated the influence of ultrasound transducer rotation and tilt on shear wave velocity (SWV, an index of stiffness) measurements of the ITB and the intra-rater repeatability of SWV measurements in the longitudinal direction. SWV was measured unilaterally (dominant limb) using ultrasound shear wave elastography in the middle region of the ITB in supine at rest (20-25° knee flexion) in ten healthy volunteers (4 females). A 3-dimensional video system provided real-time feedback of probe orientation with respect to the thigh. Measurements were made at 10° increments of probe rotation, from longitudinal to transverse alignment relative to the approximate direction of ITB fibres, and 5-10° tilts about the longitudinal and sideways axes of the transducer. One-way repeated measures ANOVA compared SWV between angles and tilts. Intraclass correlation coefficients (ICCs) and standard error of measurement (SEM) were used to calculate repeatability for two to five (longitudinal only) repetitions. SWV was greatest when the transducer was aligned to ITB fibres (longitudinal: 10.5 ± 1.7 m/s) and lowest when perpendicular (transverse: 5.8 ± 2.4 m/s). Compared to longitudinal alignment, SWV decreased significantly (p < 0.01) when the transducer was rotated 20° or more. Tilted measurements did not differ between angles. Intra-rater repeatability was excellent with the average of two measurements (ICC = 0.99, 95% CI 0.95, 0.99; SEM = 0.31 m/s). These findings show that SWV changes with orientation relative to fibre direction. Transducer orientation requires careful control to ensure comparable measures.

Shear wave elastography characteristics of upper limb muscle in rigidity-dominant Parkinson's disease

BACKGROUND

Rigidity is one of the major manifestations of Parkinson's disease (PD), but no quantitative and objective imaging method has been developed to measure rigidity. Ultrasound shear wave elastography (SWE) can reflect the stiffness of tissue by providing a quantitative index. Thus, we conducted this study to evaluate the potential clinical value of SWE in assessing rigidity in PD.

METHODS

A total of 63 subjects (44 patients with rigidity-dominant PD and 19 right-dominant-hand normal controls with matched age) were enrolled, and each underwent ultrasound SWE testing. The tests were conducted on the brachioradialis (BR) and biceps brachii (BB) on the more affected side in patients with PD and on the right side in normal controls. Differences in quantitative shear wave velocity (SWV) between patients with PD and normal controls were determined. The relationship of muscle SWV with joint rigidity, UPDRSIII, disease duration, sex, and age in patients with PD was analyzed. The intraclass correlation coefficient (ICC) was used to evaluate the reliability of SWE in assessing muscle stiffness in patients with PD.

RESULTS

The mean SWVs of the BB and BR were higher in the PD group (3.65±0.46 and 4.62±0.89 m/s, respectively) than in normal controls (2.79±0.37 and 3.26±0.40 m/s, respectively). Stiffness in BR and BB was correlated with the upper-limb joint rigidity, UPDRSIII, and disease duration but not with sex or age in the PD group. The intraobserver correlation coefficients (ICCs) for interobserver and intraobserver variations in measuring SWV were 0.85 (95% confidence interval 0.56-0.95) and 0.85 (95% confidence interval 0.58-0.95), respectively, for BR and 0.90 (95% confidence interval 0.73-0.97) and 0.86 (95% confidence interval 0.61-0.95), respectively, for BB.

CONCLUSIONS

SWV is associated with joint rigidity and disease duration, indicating that SWE can be potentially used as an objective and quantitative tool for evaluating rigidity.

Effects of body postures on the shear modulus of thoracolumbar fascia: a shear wave elastography study

This study is aimed to use shear wave elastography (SWE) to study the relationship between shear modulus and different body postures of the thoracolumbar fascia (TLF) and acquire physiologically meaningful information from the stiffness-posture graph to better quantify passive flexion responses. Seven passive postures were defined to evaluate the shear modulus of right side TLF at the third and fourth lumbar vertebra levels (L3 and L4) in twenty healthy male subjects. The TLF stiffness was significantly different among different postures (p < 0.001), and the TLF stiffness at L3 was always less than that at L4 (p < 0.001). As the forward tilt increased from 0 to 60°, the TLF stiffness increased in sitting and standing postures by 54.01% and 192.84%. In the neutral postures, the TLF stiffness in standing and sitting postures was 66.98% and 165.48% higher than that in rest posture. The above results show that the elastic properties of TLF play an important role in maintaining body static posture and that the forward tilt and sitting postures are likely to induce low back pain (LBP). In conclusion, this study provides preliminary in vivo data for the relationship between body postures and TLF stiffness.

Application of ultrasound for muscle assessment in sarcopenia: 2020 SARCUS update

PURPOSE

In 2018, the SARCUS working group published a first article on the standardization of the use of ultrasound to assess muscle. Recommendations were made for patient positioning, system settings and components to be measured. Also, shortcomings in knowledge were mentioned. An important issue that still required standardization was the definition of anatomical landmarks for many muscles.

METHODS

A systematic search was performed in Medline, SCOPUS and Web of Sciences looking for all articles describing the use of ultrasound in the assessment of muscle not described in the first recommendations, published from 01/01/2018 until 31/01/2020. All relevant terms used for older people, ultrasound and muscles were used.

RESULTS

For 39 muscles, different approaches for ultrasound assessment were found that likely impact the values measured. Standardized anatomical landmarks and measuring points were proposed for all muscles/muscle groups. Besides the five already known muscle parameters (muscle thickness, cross-section area, pennation angle, fascicle length and echo-intensity), four new parameters are discussed (muscle volume, stiffness, contraction potential and microcirculation). The former SARCUS article recommendations are updated with this new information that includes new muscle groups.

CONCLUSIONS

The emerging field of ultrasound assessment of muscle mass only highlights the need for a standardization of measurement technique. In this article, guidelines are updated and broadened to provide standardization instructions for a large number of muscles.

Shear modulus of multifidus and longissimus muscles measured using shear wave elastography correlates with muscle activity, but depends on image quality

Shear wave elastography (SWE) estimates shear modulus in muscle. This is interpreted as an index of muscle stiffness, but depends on muscle characteristics. This study evaluated relationship between shear modulus and myoelectric activity of lumbar multifidus and longissimus muscles to assess its validity. Intramuscular electromyography (EMG) of multifidus (deep [DM], superficial [SM] fibres) at L4/5, longissimus [LG] at L2, were recorded in nine healthy participants. Participants performed isometric trunk extension in side-lying from 0 to 30% maximal voluntary contraction (MVC) with EMG amplitude feedback. Using SWE, two regions of interest (ROI) were investigated in each muscle. Generally, shear modulus was moderately correlated with root mean squared (RMS) EMG (r = 0.50-0.78). Univariate and multiple regression analyses showed ultrasound/SWE features of 'B-mode quality' (24.5%), '%Void pixels' (17.9%) and 'Connective tissue' (16.2%) explained most variation in the shear modulus/EMG relationship. Regression prediction scores generated using imaging features were correlated with r-coefficients of shear modulus/EMG relationship. When analysis was restricted to high quality data (i.e., regression prediction score above an a priori defined threshold), the shear modulus/EMG relationship increased to r = 0.70-0.96. Although a linear relationship between shear modulus/EMG was confirmed, supporting validity of SWE measures in anatomically distinct back muscles, this depends on image quality.

Changes in Muscle Mass in Patients With Renal Transplants Based on Ultrasound: A Prospective Study

OBJECTIVES

This original research aimed to investigate the value of ultrasound (US), including grayscale US and shear wave elastography (SWE), in quantitatively evaluating muscle mass after kidney transplantation.

METHODS

A total of 52 patients and 54 healthy control participants were recruited. High-frequency US was used to evaluate the echo intensity and muscle morphologic features. Muscle stiffness in the rectus femoris was assessed with SWE. Interclass and intraclass correlation coefficients were used for evaluating measurement reliability. The diagnostic performance of SWE was determined by a receiver operating characteristic curve analysis.

RESULTS

The intraobserver and interobserver repeatability was excellent (all correlation coefficients >0.940; P < .05). The best evaluation point after right iliac fossa transplantation was at the lower third of the right leg. In patients, the skin (0.154 versus 0.192 cm) and rectus femoris (0.700 versus 0.905 cm) were thinner, and the pinnate angle (6.500° versus 8.000°) and area (0.965 versus 1.270 cm² ) were smaller (all P < .05). The US results showed that, compared with the controls, all patients' rectus femoris echo intensity (P < .001 in the transverse section) and elastic modulus (P < .001 in the Young modulus and shear wave speed) increased significantly. The cutoff values were 10.05 and 10.37, and the areas under the receiver operating characteristic curves were 0.843 and 0.845 for predicting kidney transplant and sarcopenia, respectively.

CONCLUSIONS

This noninvasive and convenient technique might be effective for objectively evaluating the muscle mass of patients after kidney transplantation.

Reliability of shear-wave elastography in assessing thoracolumbar fascia elasticity in healthy male

The objectives of this study were to examine the intra and inter-operator reliability of shear wave elastography (SWE) device in quantifying the shear modulus of thoracolumbar fascia (TLF) and the device’s abilities to examine the shear modulus of the TLF during upper body forward. Twenty healthy male subjects participated in this study (mean age: 18.4 ± 0.7 years). Two independent operators performed the shear modulus of TLF during upper body forward using SWE, and interclass correlation coefficient (ICC) and minimum detectable change (MDC) were calculated. The shear modulus of the TLF was quantified by operator A using SWE at upper body forward 60°. The intra-operator (ICC = 0.860–0.938) and inter-operator (ICC = 0.904–0.944) reliabilities for measuring the shear modulus of the TLF with the upper body forward 0° were rated as both excellent, and the MDC was 4.71 kPa. The TLF shear modulus of upper body forward 60°was increased 45.5% (L3) and 55.0% (L4) than that of upper body forward 0°. The results indicate that the SWE is a dependable tool to quantify the shear modulus of TLF and monitor its dynamic changes. Therefore, this device can be used for biomechanical study and intervention experiments of TLF.

Usability and Pitfalls of Shear-Wave Elastography for Evaluation of Muscle Quality and Its Potential in Assessing Sarcopenia: A Review

Sarcopenia is age-related progressive and generalized loss of skeletal muscle mass and strength. Its prevalence is rising, which poses a burden for society because it increases disability and dependency and therefore raises health care costs. Muscle mass quality, however-an essential part of sarcopenia-is not easily diagnosable yet. Recent interest has risen for ultrasonographic evaluation of muscle. This review introduces muscle elastography as a possible, easy and cheap tool to evaluate qualitative muscle parameters. Basic principles of muscle elastography are described, as well as different elastography techniques and some technical considerations. Furthermore, a proposal for practical guidelines is offered and factors influencing muscle stiffness are highlighted.

Shear wave elastography of the saphenous nerve

The purpose of this study is to study sonoelastographic features of the saphenous nerve.The study included 72 saphenous nerves in 36 healthy subjects. High resolution ultrasound and Shearwave elastography were used to evaluate the saphenous nerve. Cross sectional area (CSA) and stiffness were measured.The mean CSA of the saphenous nerve was 5.7 mm. The mean shear elastic modulus of the saphenous nerve in the short axis was 29.5 kPa. The mean shear elastic modulus of the saphenous nerve in long axis was 29.9 kPa. The saphenous nerve elastic modulus also showed no correlation with CSA in neither the long axis nor short axis. Positive correlation between elasticity measurements in the long and short axes. Age, height, weight, and BMI showed no correlation with saphenous nerve elastic modulus in short or long axes.The elastic modulus of the saphenous nerve has been determined in healthy subjects and can serve as a reference for future assessment of the saphenous nerve before different procedures.

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.

High school male basketball athletes exhibit greater hamstring muscle stiffness than females as assessed with shear wave elastography

OBJECTIVE

The purpose of this study was to characterize lower extremity passive muscle stiffness in a young, healthy, athletic population. It was hypothesized that males would exhibit greater stiffness than females and that hamstring stiffness would increase with increased passive hamstring stretch.

METHODS

Male (n = 52, age 16.0 ± 1.3 years, height 180.3 ± 7.9 cm, weight 73.1 ± 11.8 kg) and female (n = 89, age 15.6 ± 1.3 years, height 169.7 ± 8.1 cm, weight 65.2 ± 13.2 kg) high school basketball athletes were recruited for this study. Shear wave elastography (SWE) was used to measure shear wave velocity (m/s) of the biceps femoris muscle at three leg positions (40%, 60%, and 80%) of the maximum passive 90-90 straight-leg raise position for each leg. Hamstring stiffness (kPa) was quantified from the SWE elastogram using custom processing software.

RESULTS

Hamstring stiffness was significantly greater for males than females at every position on both the dominant and non-dominant limbs (p < 0.05). Hamstring stiffness was greater on the non-dominant limb than the dominant for females at the 40% position. Stiffness at 60% was greater than stiffness at 40% for males on both the dominant and non-dominant limbs. However, stiffness at 60% was greater than stiffness at 80% on the male non-dominant limb. Females demonstrated higher stiffness at 40% than both 60% and 80% for the dominant and non-dominant limbs.

CONCLUSION

Healthy male basketball players had higher hamstring muscle stiffness than female players. Future studies may investigate what factors contribute to the large variability observed in muscle stiffness, resulting in mixed results on the effects of leg dominance and stretching positions.

A Novel, Reliable Protocol to Objectively Assess Scar Stiffness Using Shear Wave Elastography

The aim of this research was to investigate the use of shear wave elastography as a novel tool to quantify and visualize scar stiffness after a burn. Increased scar stiffness is indicative of pathologic scarring which is associated with persistent pain, chronic itch and restricted range of movement. Fifty-five participants with a total of 96 scars and 69 contralateral normal skin sites were evaluated. A unique protocol was developed to enable imaging of the raised and uneven burn scars. Intra-rater and inter-rater reliability was excellent (intra-class correlation coefficient >0.97), and test-retest reliability was good (intra-class correlation coefficient >0.85). Shear wave elastography was able to differentiate between normal skin, pathologic scars and non-pathologic scars, with preliminary cutoff values identified. Significant correlations were found between shear wave velocity and subjective clinical scar assessment (r = 0.66). Shear wave elastography was able to provide unique information associated with pathologic scarring and shows promise as a clinical assessment and research tool.

Shear-wave elastography for assessment of trapezius muscle stiffness: Reliability and association with low-level muscle activity

Purpose

Shear-wave elastography has been recognized a useful tool for quantifying muscle stiffness, commonly reported as shear modulus, however the reports on reliability are often limited to test-retest correlations. In this study, we explored the reliability of shear-wave elastography for assessment of the trapezius muscle stiffness and its relationship with low-level muscle activity.

Methods

Twenty participants were included in a two-session experiment. Measurements of shear modulus and muscle activity were performed at rest and during low-level activity, induced by shoulder abduction without additional external resistance.

Results

Good to excellent intra-session repeatability (ICC > 0.80) and moderate inter-rater and inter-session reproducibility (ICC = 0.66–0.74) were observed. Typical errors were acceptable (7.6% of the mean value) only for intra-session measurements in resting conditions, but not acceptable for all conditions with low-level muscle activity (10.2–16.6% of the mean value). Inverse relationships between shear modulus and muscle activity at 40° and 60° of shoulder abduction (r = -0.53 and -0.57) were observed on a group level. We also found higher shear modulus in males compared to females, for the parallel probe position compared to the perpendicular position (in relation to muscle fiber orientation), and for the dominant side of the body compared to the non-dominant side.

Conclusions

This study showed an inverse relationship between muscle activity in low-level range and shear modulus on a group level, suggesting inherent passive stiffness could account for a larger portion of the variance (compared to muscle activity) in shear modulus when the muscle activity is low. Our results imply that shear-wave elastography can be used in research exploring muscle stiffness, however, caution is needed since only intra-session examination in resting conditions showed acceptable within-participant typical errors. The secondary analyses of the study showed higher shear modulus for males, for the non-dominant side of the body and for the parallel orientation of the ultrasound probe.

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.

Evaluation of effects of aging on skeletal muscle elasticity using shear wave elastography

PURPOSE

To evaluate the effects of aging on skeletal muscle stiffness in relaxed and contracted status using shear wave elastography (SWE).

MATERIALS AND METHODS

A total of 57 participants were enrolled to this institutional review board approved prospective study. Medial head of the gastrocnemius muscle (GM) of all participants were examined bilaterally by a single radiologist in prone position. Muscle thickness, stiffness values in both relaxed and contracted status were measured. Stiffness increase rate (SIR) was calculated for all muscles. The Spearman's correlation test was used for correlation analyses. Mann-Whitney U test was used to compare subgroups.

RESULTS

The mean age of the participants was 41.15 ± 16.19 (range, 18-74). The means of stiffness values of medial head of GM were 12.51 ± 2.56 kPa and 81.74 ± 15.77 kPa in relaxed and contracted status, respectively. The mean of SIR values was 5.62 ± 1.05 (range, 3.18-8.66). The stiffness values of relaxed and contracted medial head of GM had moderate to strong inverse correlations with age for both dominant and non-dominant extremities (r range: -0.703 to -0.590). Age subgroup analyses revealed significant differences in muscle thickness and stiffness values, whereas no significant difference was found in SIR values.

CONCLUSION

In conclusion, despite the decrease in stiffness of skeletal muscle with advancing age, SIR remained similar. Any improvement in stiffness values of skeletal muscle in relaxed status may play pivotal role in the management of sarcopenia.

Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function.

Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function.

Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function.

Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function.

Great potential of ultrasound elastography for the assessment of the masseter muscle in patients with temporomandibular disorders. A systematic review

Objective:

To summarize the available evidence on the use of elastography in the assessment of the masseter muscle in healthy individuals and patients with masseter muscle disorders.

Methods:

Systematic literature review has been performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.

Results:

16 of 142 studies identified were analyzed. Elastography was used in seven studies. Heterogeneity was observed in terms of study protocols, devices, patients, units of measure, and results. Elasticity values showed a correlation between the left and right masseter muscle side in healthy people, but not in patients with temporomandibular disorders (TMDs). Elasticity values increased in TMD and were correlated with the severity of TMD symptoms. Phantom studies proved the high reliability of elastography.

Conclusion:

Elastography is a promising tool for the assessment of the masseter muscle elasticity, but the evidence is insufficient. Studies on larger groups are needed to determine the accuracy of elastography to characterize masticatory muscle disorders.

Influence of limb position on assessment of nerve mechanical properties by using shear wave ultrasound elastography

INTRODUCTION

Evaluation of nerve mechanical properties has the potential to improve assessment of nerve impairment. Shear wave velocity, as measured by using shear wave (SW) ultrasound elastography, is a promising indicator of nerve mechanical properties such as stiffness. However, elucidation of external factors that influence SW velocity, particularly nerve tension, is required for accurate interpretations.

METHODS

Median and ulnar nerve SW velocities were measured at proximal and distal locations with limb positions that indirectly altered nerve tension.

RESULTS

Shear wave velocity was greater at proximal and distal locations for limb positions that induced greater tension in the median (mean increase proximal 89.3%, distal 64%) and ulnar (mean increase proximal 91.1%, distal 37.4%) nerves.

DISCUSSION

Due to the influence of nerve tension when SW ultrasound elastography is used, careful consideration must be given to limb positioning.

Effect of acquisition depth and precompression from probe and couplant on shear wave elastography in soft tissue: an in vitro and in vivo study

Background

Shear wave elastography is a promising method to diagnose early musculoskeletal lesions. We aimed to explore the feasible depth and acceptable precompression applied by probe and couplant for soft tissues in the present system.

Methods

Ex-vivo muscles were evaluated at depths of 0.5-6 cm by 3 operators, using 1-5 mm couplant thickness and 0-3.0 kPa probe pressure. We compared the shear wave speed (SWS) and used intraclass correlation coefficients to assess reproducibility. In vivo skin and subcutaneous superficial fascia from volunteers were tested at depths ranging from 0.1-0.5 cm with 1-20 mm couplant thickness.

Results

The SWS of ex-vivo muscles varied and increased with depth, and could not be acquired at 6 cm because the shear wave failed to be detected. Furthermore, while the SWS of ex-vivo muscles were not affected by the couplant thickness, it was affected by probe pressure. Most cases demonstrated a satisfactory agreement degree of the intraoperator reproducibility (ICC, 0.81-0.95) and a substantial interoperator reproducibility (ICC >0.60). Inter- and intra-operator reproducibility was better at a depth of 0.5-4 cm than at 5 cm. In the in vivo study, when tissues within a 0.2 cm depth were evaluated, the SWS that was acquired using a couplant thickness of >10 mm was different from that acquired using other thicknesses.

Conclusions

The SWS acquired at a depth of ≤3 cm with a suitable amount of couplant is recommended.

Modulation in the elastic properties of gastrocnemius muscle heads in individuals with plantar fasciitis and its relationship with pain

The objectives of this study were (1) to investigate the passive stiffness of the medial gastrocnemius (MG) and lateral gastrocnemius (LG) in patients with and without plantar fasciitis (PF), (2) to explore the correlation between gastrocnemius stiffness and plantar fascia thickness (PFT) as well as the intensity of pain in patients with PF, (3) to detect optimal cut-off points for stiffness of the MG and LG for identifying patients with PF. Forty patients (mean age = 51.1 years ± 12.9) participated in this study. The elastic properties of the MG and LG were quantified using shear wave elastography ultrasound. The thickness of the plantar fascia was measured by B-mode imaging. The intensity of pain was assessed using a visual analogue scale. The results showed that when the ankle was in the relaxed position, patients with PF had increased passive stiffness in the MG (P < 0.05) but not in the LG. Significant correlations were found between pain and the stiffness of the MG (middle, distal; all P-values < 0.05) and no correlation was observed between pain and PFT (P = 0.416). The initial cut-off point for the stiffness of the MG was 29.08 kPa when the ankle was in the relaxed position. The findings from the present study show that an increase in muscle stiffness is not the same in the individual muscles of the gastrocnemius muscle. Traditional treatment of the whole gastrocnemius muscle might not be targeted at the tight muscle.

Real-time shear wave ultrasound elastography: a new tool for the evaluation of diaphragm and limb muscle stiffness in critically ill patients

BACKGROUND

Muscle weakness following critical illness is the consequence of loss of muscle mass and alteration of muscle quality. It is associated with long-term disability. Ultrasonography is a reliable tool to quantify muscle mass, but studies that evaluate muscle quality at the critically ill bedside are lacking. Shear wave ultrasound elastography (SWE) provides spatial representation of soft tissue stiffness and measures of muscle quality. The reliability and reproducibility of SWE in critically ill patients has never been evaluated.

METHODS

Two operators tested in healthy controls and in critically ill patients the intra- and inter-operator reliability of the SWE using transversal and longitudinal views of the diaphragm and limb muscles. Reliability was calculated using the intra-class correlation coefficient and a bootstrap sampling method assessed their consistency.

RESULTS

We collected 560 images. Longitudinal views of the diaphragm (ICC 0.83 [0.50-0.94]), the biceps brachii (ICC 0.88 [0.67-0.96]) and the rectus femoris (ICC 0.76 [0.34-0.91]) were the most reliable views in a training set of healthy controls. Intra-class correlation coefficient for inter-operator reproducibility and intra-operator reliability was above 0.9 for all muscles in a validation set of healthy controls. In critically ill patients, inter-operator reproducibility and intra-operator 1 and 2 reliability ICCs were respectively 0.92 [0.71-0.98], 0.93 [0.82-0.98] and 0.92 [0.81-0.98] for the diaphragm; 0.96 [0.86-0.99], 0.98 [0.94-0.99] and 0.99 [0.96-1] for the biceps brachii and 0.91 [0.51-0.98], 0.97 [0.93-0.99] and 0.99 [0.97-1] for the rectus femoris. The probability to reach intra-class correlation coefficient greater than 0.8 in a 10,000 bootstrap sampling for inter-operator reproducibility was respectively 81%, 84% and 78% for the diaphragm, the biceps brachii and the rectus femoris respectively.

CONCLUSIONS

SWE is a reliable technique to evaluate limb muscles and the diaphragm in both healthy controls and in critically ill patients.

TRIAL REGISTRATION

The study was registered (ClinicalTrial NCT03550222).

Shear wave elastography potential to characterize spastic muscles in stroke survivors: Literature review

BACKGROUND

Post-stroke spasticity contributes to impairments, disabilities and decline in quality of life. Quantitative measurements of spasticity are needed in order to assess the impact of specific treatments and to choose the more accurate technique for each patient. The aim of this review is to examine the use of shear wave ultrasound elastography as a quantitative tool for monitoring biomechanical muscle properties such as stiffness and to determine whether it is a reliable method to assess spastic muscle in stroke survivors.

METHODS

Studies were sought from Academic Search Complete, CINAHL, PubMed/Medline, Scopus and SportDiscus with the following keywords: shear wave elastography, spasticity, stiffness, elasticity, hardness, stroke, cerebrovascular accident, cerebral vascular event and transient ischaemic attack. Titles and abstracts were screened, and relevant full-text articles were retrieved for further review.

FINDINGS

Of the 76 screened studies, nine captured elastography data of the spastic biceps brachii (n = 6) or the plantar flexors (n = 3) with stroke victims. All consulted studies had a different way of utilizing this technology which was expected considering no guidelines had been developed. Shear wave speed values obtained are compared and discussed with clinical measures. Reliability of the devices is also discussed.

INTERPRETATION

Shear wave ultrasound elastography can provide useful quantitative information on the mechanical properties of the spastic muscles in post-stroke patients. Nevertheless, new studies using common terminology and parameters are needed to develop reliable methods that could help in assessing treatment efficiency.

Supraspinatus Muscle and Tendon Stiffness Changes After Arthroscopic Rotator Cuff Repair: A Shear Wave Elastography Assessment

Re-tearing after arthroscopic rotator cuff repair (ARCR) frequently occurs, and high stiffness of the rotator cuff may be one of the factors. We investigated changes in stiffness of the supraspinatus muscle and tendon after ARCR as measured by shear wave elastography (SWE) with B-mode ultrasound, and compared the supraspinatus muscle stiffness of patients with recurrent tears and patients with healed rotator cuffs. Sixty patients with supraspinatus tears requiring ARCR underwent serial SWE of their supraspinatus muscles and repaired tendons. SWE was performed before surgery (Pre-Op) and at 1 week, 1 month, 2 months, 3 months, 4 months, 5 months, and 6 months after surgery. Additionally, the repaired rotator cuffs were evaluated using magnetic resonance imaging at 6 months after surgery to classify patients into a healed rotator cuff group and a recurrent tear group. Differences in SWE values between the groups were assessed at each time point. The SWE value of the repaired tendon at 1 week after ARCR was significantly greater than at 3 and 6 months. The SWE value for the supraspinatus muscle at 1 month after ARCR surgery in the healed group was lower than at Pre-Op and 4, 5, and 6 months after surgery, and it was also lower than that at 1 month after surgery in the re-tear group. There were no significant differences between time points in the SWE values of the supraspinatus muscle in the re-tear group. The SWE value of the muscle in the re-tear group was greater than in the healed group at 1 month after surgery (p < 0.05). Increased SWE values at 1 month after ARCR may predict recurrent rotator cuff tears after surgery rather than evaluating the tendon. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:219-227, 2020.

Lumbar muscles biomechanical characteristics in young people with chronic spinal pain

Background

The prevalence of low back pain is rising among the young adult population. Altered lumbar muscle tone was suggested to be associated with underlying pathologies and symptoms. To date, there is minimum information available on the repeatability of lumbar spine muscle mechanical properties in the young adults who experienced low back pain. This study aimed to assess the reproducibility of mechanical properties of lumbar spinal muscle in young adults with spinal pain by myotonometer and explored the difference in reproducibility when different number of indentations was used.

Methods

Participants who aged between 18 to 25 and reported chronic LBP were recruited. Lumbar muscle tone (Hz) and stiffness (N/m) were assessed by myotonometer on one occasion by two assessors. Parameters were recorded by triple scans and 5-scans mode. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), smallest real difference (SRD), Bland and Altman analysis were used to assess agreement between two measurements. The relationship between muscle mechanical properties and pain score and disability level were assessed by Spearman’s rank correlation coefficient.

Results

The results of ICCs indicated excellent repeatability in triple scans and 5-scans mode for each lumbar level bilaterally (ICC > 0.75). SEM and SRD were smaller in triple scans than 5-scans mode for most levels. Bland and Altman analysis revealed no systematic bias. Spearman’s rank correlation analysis indicated significant high correlations between muscle tone and disability level (r = 0.80, p < 0.05), and between muscle stiffness and disability level (r = 0.81, p < 0.05).

Conclusions

This study found that lumbar spinal muscle tone and stiffness were repeatable parameters when measured by myotonometer. The reproducibility of muscle mechanical parameters did not appear to differ between the two scanning modes with different number of indentations. Muscle tone and stiffness measured by myotonometer may therefore be reliable as outcome measures to assess intervention induced changes. The lack of significant association between intensity of pain and mechanical properties of paraspinal muscles may suggest that muscle properties measured at rest might not be related to pain level at rest but more related to pain elicited during movement.

Regional Elastic Properties of the Achilles Tendon Is Heterogeneously Influenced by Individual Muscle of the Gastrocnemius

Background

Anatomical studies and the mechanical property studies showed that there is a strong correlation between Achilles tendon (AT) elasticity and individual gastrocnemius muscle (the medial head of gastrocnemius (MG) and the lateral head of gastrocnemius (LG)) elasticity. Limited ankle dorsiflexion range of motion has been correlated with decreased flexibility of the MG/LG/AT complex. However, no studies have been conducted to examine the exact correlation between the Achilles tendon and the individual muscle of the gastrocnemius.

Purposes

The purposes of the present study were (1) to evaluate intra- and interoperator reliabilities of elastic property measurements in the gastrocnemius muscle-Achilles tendon complex by using the shear wave elastography (SWE) and (2) to examine the correlation between the regional elastic properties of the AT and the individual muscle of the gastrocnemius.

Methods

Twenty healthy subjects (mean age: 22.50 (3.02) years) were recruited in this study. The elastic properties of the AT and the individual muscle of the gastrocnemius were quantified using the SWE.

Findings

The SWE has comparatively high reliability in quantifying the elastic properties of the muscle-tendon range from good to excellent. The intraoperator ICC of the gastrocnemius muscle-Achilles tendon complex was 0.77 to 0.95, while the interoperator ICC was 0.76 to 0.94. The minimal detectable change (MDC) of the muscle was 1.72 kPa, while the AT was 32.90 kPa. A significant correlation was found between the elastic modulus of AT and the elastic modulus of the MG (r = 0.668 and p = 0.001 at the relaxing position and r = 0.481 and p = 0.032 at the neutral position).

Conclusions

The SWE has the potential to assess localized changes in muscle-tendon elastic properties, provide more intuitive relations between elastic properties of the muscle tendon and function, and evaluate the therapeutic effect of the muscle tendon. A significant correlation between the AT and the MG was found, and it may provide a new treatment idea (targeted to the tight muscle heads) for the clinical setting to treat subjects with AT disorders.

Which Confounders Have the Largest Impact in Shear Wave Elastography of Muscle and How Can They be Minimized? An Elasticity Phantom, Ex Vivo Porcine Muscle and Volunteer Study Using a Commercially Available System

The goal of the study was to investigate the quantitative impact of region of interest (ROI), software choice, muscle fiber orientation and preload tension on shear wave velocity (SWV). First, SWV was assessed in an isotropic elasticity phantom and ex vivo porcine muscle using a commercially available clinical ultrasound system. Secondly, SWV was acquired in relaxed and stretched calf muscles of healthy volunteers (dorsal extension of the talocrural joint), for both parallel and transverse probe direction to the fibers, as well as for different ROIs and software versions. The effect of intermediate probe-fiber alignments was also analyzed. Finally, the impact of confounding factors on SWV reproducibility was minimized with a second force-controlled volunteer study, in which the calf was isometrically loaded, and fiber orientation and ROI were well-defined. 2046 in vivoSWE images were acquired to analyze SWV reproducibility with different confounder settings. In healthy volunteers, the main variance-contributing factors were in order of importance muscle tension, fiber orientation, horizontal ROI size and insertion depth. Regression analysis showed significantly reduced SWV with increasing insertion depth for each study material. Parallel probe-fiber orientation, muscle stretch and increasing horizontal ROI size led to significantly higher SWV. Based on the results of the study, we provide recommendations to minimize the impact of confounders in musculoskeletal elastography and discuss the main confounding mechanisms and trade-offs between confounding variables. Coefficients of variation can be significantly reduced with a controlled protocol, if the confounders are clinically taken into account.

Sonoelastography of the trunk and lower extremity muscles in a case of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a rare genetic disorder typically presenting with muscle weakness and reduced tone of trunk and lower extremities. The sonoelastographic properties of DMD are poorly understood. We describe sonoelastographic characteristics of a patient's trunk and lower extremity musculature. An 8-year-old male presented with a 5-year history of DMD. Sonoelastographic measures of the gluteus maximus and medius, lumbar erector spinae, rectus abdominis, rectus femoris, biceps femoris, tibialis anterior, medial and lateral gastrocnemius muscles were obtained. Sonoelastography demonstrated increased elasticity by elevated kiloPascals (kPa) across all muscles, except the lumbar erector spinae. Patient values were compared to an age-matched healthy control. These abnormal sonoelastographic findings reflected the pathological mechanical properties of DMD. Sonoelastography was valuable for characterizing the mechanical properties of normal and abnormal muscle tissue. There is limited information on the sonoelastography application to DMD. Sonoelastography may serve as a useful measure for diagnosis and monitoring clinical outcomes for DMD.

Ultrasound imaging for sarcopenia, spasticity and painful muscle syndromes

PURPOSE OF REVIEW

On the basis of its various advantages and the relevant awareness of physicians, ultrasound imaging has overwhelmingly taken its place in the scientific arena. This is true both from the side of daily clinical applications and also from the side of research. Yet, ultrasound provides real-time (diagnostic) imaging and (interventional) guidance for a wide spectrum of muscle disorders. In this regard, this review aims to discuss the potential/actual utility of ultrasound imaging in particular muscle disorders, that is, sarcopenia, spasticity and fibromyalgia/myofascial pain syndrome.

RECENT FINDINGS

Due to the aging population worldwide and the importance of functionality in the older population, mounting interest has been given to the diagnosis and management of sarcopenia in the recent literature. Likewise, several articles started to report that ultrasound imaging can be used conveniently and effectively in the early diagnosis and quantification of sarcopenia.For spasticity, aside from ultrasound-guided botulinum toxin injections, intriguing attention has been paid to sonographic evaluation of muscle architecture, echogenicity and elasticity in the follow-up of these chronic conditions.As regards painful muscle syndromes, quantitative ultrasound techniques have been shown to detect statistically significant differences between healthy controls and patients with myofascial pain syndrome.

SUMMARY

Ultrasound imaging seems to be a promising tool that indisputably deserves further research in the management of a wide range of muscle disorders. VIDEO ABSTRACT: http://links.lww.com/COSPC/A17.

Spatial-Temporal Changes of Mechanical Microenvironment in Skin Wounds During Negative Pressure Wound Therapy

Cell migration, proliferation, and differentiation are regulated by mechanical cues during skin wound healing. Negative pressure wound therapy (NPWT) reduces the healing period by optimizing the mechanical microenvironment of the wound bed. Under NPWT, it remains elusive how the mechanical microenvironment (e.g., stiffness, strain gradients) changes both in time and space during wound healing. To illustrate this, the healing time of full-thickness skin wounds under NPWT, with pressure settings ranging from -50 to -150 mm Hg, were evaluated and compared with gauze dressing treatments (control group), and three-dimensional finite element models of full-thickness skin wounds on days 1 and 5 after treatment were developed on the basis of MR 3D imaging data. Shear wave elastography (SWE) was applied to detect the stiffness of wound soft tissue on days 1 and 5, and nonlinear finite element analysis (FEA) was used to represent the spatial-temporal environment of the 3D strain field of the wound under NPWT vs the control group. Compared with the control group, NPWT with -50, -80, and -125 mm Hg promoted wound healing. SWE showed that the elastic modulus of wounded skin increased during healing. Meanwhile, the elastic modulus in wounded skin under NPWT was significantly smaller than in the control group. Strain and its gradient decreased under NPWT during wound healing, while no significant change was observed in the control group. This study, which is based on MR 3D imaging, shear wave elastography, and nonlinear FEA, provides an in-depth understanding of changes of the skin mechanical microenvironment under NPWT in the time-space dimension and the associated wound healing.

Posture-related stiffness mapping of paraspinal muscles

The paraspinal compartment acts as a bone-muscle composite beam of the spine. The elastic properties of the paraspinal muscles play a critical role in spine stabilization. These properties depend on the subjects' posture, and they may be drastically altered by low back pain. Supersonic shear wave elastography can be used to provide quantitative stiffness maps (elastograms), which characterize the elastic properties of the probed tissue. The aim of this study was to challenge shear wave elastography sensitivity to postural stiffness changes in healthy paraspinal muscles. The stiffness of the main paraspinal muscles (longissimus, iliocostalis, multifidus) was measured by shear wave elastography at the lumbosacral level (L3 and S1) for six static postures performed by volunteers. Passive postures (rest, passive flexion, passive extension) were performed in a first shear wave elastography session, and active postures (upright, bending forward, bending backward) with rest posture for reference were performed in a second session. Measurements were repeated three times for each posture. Sixteen healthy young adults were enrolled in the study. Non-parametric paired tests, multiple analyses of covariance, and intra-class correlations were implemented for analysis. Shear wave elastography showed good to excellent reliability, except in the multifidus at S1, during bending forward, and in the multifidus at L3, during bending backward. Yet, during bending forward, only poor quality was recorded for nine volunteers in the longissimus. Significant intra- and inter-muscular changes were observed with posture. Stiffness significantly increased for the upright position and bending forward with respect to the reference values recorded in passive postures. In conclusion, shear wave elastography allows reliable assessment of the stiffness of the paraspinal muscles except in the multifidus at S1 and longissimus, during bending forward, and in the multifidus at L3, during bending backward. It reveals a different biomechanical behaviour for the multifidus, the longissimus, and the iliocostalis.

Ulnar nerve instability in the cubital tunnel of asymptomatic volunteers

PURPOSE

Ulnar nerve instability (UNI) in the cubital tunnel is defined as ulnar nerve subluxation or dislocation. It is a common disorder that may be noted in patients with neuropathy or in the asymptomatic. Our prospective, single-site study utilized high-resolution ultrasonography (US) to evaluate the ulnar nerve for cross-sectional area (CSA) and measures of shear-wave elastography (SWE). Mechanical algometry was obtained from the ulnar nerve in the cubital tunnel to assess pressure pain threshold (PPT).

METHODS

Forty-two asymptomatic subjects (n = 84 elbows) (25 males, 17 females) aged 22-40 were evaluated. Two chiropractic radiologists, both with 4 years of ultrasound experience performed the evaluation. Ulnar nerves in the cubital tunnel were sampled bilaterally in three different elbow positions utilizing US, SWE, and algometry. Descriptive statistics, two-way ANOVA, and rater reliability were utilized for data analysis with p ≤ 0.05.

RESULTS

Fifty-six percent of our subjects demonstrated UNI. There was a significant increase in CSA in subjects with UNI (subluxation: 0.066 mm² ± 0.024, p = 0.027; dislocation: 0.067 mm² ± 0.024, p = 0.003) compared to controls (0.057 mm² ± 0.017) in all three elbow positions. There were no significant group differences in SWE or algometry. Inter- and intra-observer agreements for CSA of the ulnar nerves within the cubital tunnel were assessed using intraclass correlation coefficient (ICC) and demonstrated moderate (ICC 0.54) and excellent (ICC 0.94) reliability.

CONCLUSIONS

Most of the asymptomatic volunteers demonstrated UNI. There was a significant increase in CSA associated with UNI implicating it as a risk factor for ulnar neuropathy in the cubital tunnel. There were no significant changes in ulnar nerve SWE and PPT. Intra-rater agreement was excellent for the CSA assessment of the ulnar nerve in the cubital tunnel. High-resolution US could be utilized to assess UNI and monitor for progression to ulnar neuropathy.

Imaging in the diagnosis of idiopathic inflammatory myopathies; indications and utility

INTRODUCTION

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of muscle diseases that carry a significant morbidity and mortality risk. The utilization of imaging in the diagnostic pathway of IIM is therefore important to obtain early diagnosis and even monitor patients over time. Areas covered: Magnetic resonance imaging (MRI) has been the main imaging modality used to detect myositis but limitations include cost and accessibility, leading to delays in time to scan, and patient contraindications. This has led to the exploration of other imaging techniques to diagnose and monitor response to therapy. This article is based primarily on a literature search via PubMed using Boolean terms 'myositis' and the various imaging modalities. Expert opinion: Imaging is sensitive to pathology in IIM and may contribute to the diagnostic process. Learning how specific imaging features can distinguish different forms of IIM may allow more rapid diagnosis of myositis subtype and treatment planning, and to monitor disease activity particularly in patients who respond poorly to treatment. However, more work is needed to investigate the validity and relative utility of these imaging modalities.

Cancer invasion into musculature: Mechanics, molecules and implications

Tumor invasion along structural interphases of surrounding tumor-free tissue represents a key process during tumor progression. Much attention has been devoted to mechanisms of tumor cell migration within extracellular matrix (ECM)-rich connective tissue, however a comprehensive understanding of tumor invasion into tissue of higher structural complexity, such as muscle tissue, is lacking. Muscle invasion in cancer patients is often associated with destructive growth and worsened prognosis. Here, we review biochemical, geometrical and mechanical cues of smooth and skeletal muscle tissues and their relevance for guided invasion of cancer cells. As integrating concept, muscle-organizing ECM-rich surfaces of the epi-, peri- and endomysium provide cleft-like confined spaces along interfaces between dynamic muscle cells, which provide molecular and physical cues that guide migrating cancer cells, forming a possible contribution to cancer progression.