Evaluation of the Reproducibility of MR Elastography Measurements of the Lumbar Back Muscles.

BACKGROUND: MR elastography (MRE) may provide quantitative imaging biomarkers of lumbar back muscles (LBMs), complementing MRI in spinal diseases by assessing muscle mechanical properties. However, reproducibility analyses for MRE of LBM are lacking. PURPOSE: To assess technical failure, within-day and inter-day reproducibility, robustness with the excitation source positioning, and inter-observer agreement of MRE of muscles. STUDY TYPE: Prospective. SUBJECTS: Seventeen healthy subjects (mean age 28 ± 4 years; 11 females). FIELD STRENGTH/SEQUENCE: 1.5 T, gradient-echo MRE, T1-weighted turbo spin echo. ASSESSMENT: The pneumatic driver was centered at L3 level. Four MRE were performed during two visits, 2-4 weeks apart, each consisting of two MRE with less than 10 minutes inter-scan interval. At Visit 1, after the first MRE, the coil and driver were removed, then reinstalled. The MRE was repeated. At Visit 2, following the first MRE, only the driver was moved down 5 cm. The MRE was repeated. Two radiologists segmented the multifidus and erector spinae muscles. STATISTICAL TESTS: Paired t-test, analysis of variance, intraclass correlation coefficients (ICCs). P-values <0.05 were considered statistically significant. RESULTS: Mean stiffness of LBM ranged from 1.44 to 1.60 kPa. Mean technical failure rate was 2.5%. Inter-observer agreement was excellent (ICC ranging from 0.82 [0.64-0.96] to 0.99 [0.98-0.99] in the multifidus, and from 0.85 [0.69-0.92] to 0.99 [0.97-0.99] in the erector spinae muscles). Within-day reproducibility was fair in the multifidus (ICC: 0.53 [0.47-0.77]) and good in the erector spinae muscles (ICC: 0.74 [0.48-0.88]). Reproducibility after moving the driver was excellent in both multifidus (ICC: 0.85 [0.69-0.93]) and erector spinae muscles (ICC: 0.84 [0.67-0.92]). Inter-day reproducibility was excellent in the multifidus (ICC: 0.76 [0.48-0.89]) and poor in the erector spinae muscles (ICC: 0.23 [-0.61 to 0.63]). DATA CONCLUSION: MRE of LBM provides measurements of stiffness with fair to excellent reproducibility and excellent inter-observer agreement. However, inter-day reproducibility in the multifidus muscles indicated that the herein used MRE protocol may not be optimal for this muscle. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 1.

Changes of trunk muscle stiffness in individuals with low back pain: a systematic review with meta-analysis.

BACKGROUND: Low back pain (LBP) is one of the most common musculoskeletal conditions. People with LBP often display changes of neuromuscular control and trunk mechanical properties, including trunk stiffness. Although a few individual studies have examined back muscle stiffness in individuals with LBP, a synthesis of the evidence appears to be lacking. Therefore, the aim of this systematic review with meta-analysis was to synthesize and evaluate the available literature investigating back muscle stiffness in association with LBP. METHODS: We conducted a systematic review of the literature according to the PRISMA guidelines. We searched Pubmed, Scopus, Web of Science and ScienceDirect for studies, that compared back muscle stiffness, measured either by ultrasound-based elastography or myotonometry, between individuals with and without LBP. Pooled data of the included studies were presented descriptively. Additionally, we performed two meta-analyses to calculate the standardized mean difference between the two groups for resting stiffness of the multifidus and erector spinae muscle. For both meta-analyses, the random effect model was used and the weight of individual studies was calculated using the inverse-variance method. The quality of the included studies was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional studies. Furthermore, the certainty of evidence was evaluated using the GRADE approach. RESULTS: Nine studies were included in our systematic review. Our results suggest that individuals with LBP have higher stiffness of the multifidus (SMD = 0.48, 95% CI: 0.15 - 0.81, p < 0.01; I2 = 48 %, p = 0.11) and erector spinae at rest (SMD = 0.37, 95% CI: 0.11 - 0.62, p < 0.01; I2 = 39 %, p = 0.14) compared to asymptomatic controls. On the other hand, the evidence regarding muscle stiffness during submaximal contractions is somewhat contradictory. CONCLUSIONS: Based on the findings of this systematic review we conclude that people with LBP may have higher back muscle stiffness compared to asymptomatic controls. Addressing muscle stiffness might represent an important goal of LBP treatment. Nevertheless, our findings should be interpreted with extreme caution due to a limited quality of evidence, small number of included studies and differences in measurement methodology.

Potential of a New, Flexible Electrode sEMG System in Detecting Electromyographic Activation in Low Back Muscles during Clinical Tests: A Pilot Study on Wearables for Pain Management.

BACKGROUND: While low back pain (LBP) is the leading cause of disability worldwide, its clinical objective assessment is currently limited. Part of this syndrome arises from the abnormal sensorimotor control of back muscles, involving increased muscle fatigability (i.e., assessed with the Biering-Sorensen test) and abnormal muscle activation patterns (i.e., the flexion-extension test). Surface electromyography (sEMG) provides objective measures of muscle fatigue development (median frequency drop, MDF) and activation patterns (RMS amplitude change). This study therefore assessed the sensitivity and validity of a novel and flexible sEMG system (NSS) based on PEVA electrodes and potentially embeddable in textiles, as a tool for objective clinical LBP assessment. METHODS: Twelve participants wearing NSS and a commercial laboratory sEMG system (CSS) performed two clinical tests used in LBP assessment (Biering-Sorensen and flexion-extension). Erector spinae muscle activity was recorded at T12-L1 and L4-L5. RESULTS: NSS showed sensitivity to sEMG changes associated with fatigue development and muscle activations during flexion-extension movements (p < 0.05) that were similar to CSS (p > 0.05). Raw signals showed moderate cross-correlations (MDF: 0.60-0.68; RMS: 0.53-0.62). Adding conductive gel to the PEVA electrodes did not influence sEMG signal interpretation (p > 0.05). CONCLUSIONS: This novel sEMG system is promising for assessing electrophysiological indicators of LBP during clinical tests.

The dominance of dorsal scapular artery as the blood supply to muscles of the back in the absence of two primary vessels: a cadaveric case report.

PURPOSE: Understanding of rare or unknown anatomical variations of the vasculature of the neck is critical to reduce the risk of complications during surgeries and other invasive procedures in the neck and shoulder regions. METHODS: Bilateral dissection of the neck and muscles of the back of an 87-year-old Caucasian male donor was performed to demonstrate the origin, course and termination of the arteries that arise in the neck. RESULTS: Several anatomical variations were noted on the right side of the neck of the donor body - (i) only inferior thyroid and ascending cervical arteries originated from the thyrocervical trunk (TCT), from the first part of the subclavian artery (SA), whereas the transverse cervical (TCA) and suprascapular (SSA) arteries were entirely absent, (ii) Dorsal scapular artery (DSA) emerged normally from the third part of the SA. However, after supplying the rhomboids and levator scapulae muscles, DSA provided two additional branches to the trapezius muscle and a branch to the supraspinatus muscle. Interestingly, the branches to the trapezius muscle from the DSA were the only sources of blood supply to the muscle. CONCLUSION: We report a unique anatomical variation involving the absence of the TCA and SSA from the TCT. The unilateral absence of these major vessels and the branches of DSA supplying the trapezius and supraspinatus muscles have not been reported previously in the literature in a single case report. This case study may provide useful information for head and neck reconstruction and shoulder repair surgeries.

Flexible sensor-based biomechanical evaluation of low-back exoskeleton use in lifting.

This study aimed to establish an ambulatory field-friendly system based on miniaturised wireless flexible sensors for studying the biomechanics of human-exoskeleton interactions. Twelve healthy adults performed symmetric lifting with and without a passive low-back exoskeleton, while their movements were tracked using both a flexible sensor system and a conventional motion capture (MoCap) system synchronously. Novel algorithms were developed to convert the raw acceleration, gyroscope, and biopotential signals from the flexible sensors into kinematic and dynamic measures. Results showed that these measures were highly correlated with those obtained from the MoCap system and discerned the effects of the exoskeleton, including increased peak lumbar flexion, decreased peak hip flexion, and decreased lumbar flexion moment and back muscle activities. The study demonstrated the promise of an integrated flexible sensor-based system for biomechanics and ergonomics field studies as well as the efficacy of exoskeleton in relieving the low-back stress associated with manual lifting.

This study established and tested a flexible sensor-based ambulatory system for biomechanical evaluation of human-exoskeleton interactions and as a promising new tool for field ergonomics studies in practical or naturalistic settings.Abbreviations: MoCap: motion capture; WMSD: Work-related musculoskeletal disorders; EMG: electromyography; IMU: inertial measurement unit; TES: thoracic erector spinae; LES: lumbar erector spinae; WITH: tasks performed with wearing the exoskeleton; WITHOUT: tasks performed without wearing the exoskeleton; RMS: root mean square; RMSE: root-mean-square error; r: Pearson's correlation coefficient; ASIS: anterior superior iliac spine.

Low back pain and biomechanical characteristics of back muscles in firefighters.

Firefighters often experience low back pain (LBP), but their back muscle characteristics are not well studied. This study aimed to 1) compare the biomechanical characteristics of back muscles and self-reported back disabilities in frontline firefighters with and without LBP history, and 2) examine the relationships between back disability and biomechanical measurements. We recruited 42 male firefighters and assessed their perceived pain and disabilities, maximum isometric back extension strength, passive stiffness, and fatigability of the longissimus. 54.8% of the participants experienced LBP within the past year. Those indicating higher pain intensity also had greater disability as indicated by the Oswestry Disability Index. There were no significant differences in strength, stiffness or fatigability of the back muscles between firefighters with and without LBP history. Multiple linear regression analysis revealed no significant relationship between the back disability and any biomechanical or demographic measures, likely due to the high functional abilities of the participants.

Approximately 50% of the firefighters who participated in the study experienced low back pain in the past 12 months. Since the pain level was mild to moderate, most of them continued to report to work. Biomechanically, there were no differences in back muscle strength, stiffness, resistance to fatigue, or left-right symmetry between firefighters with and without back pain history. Back disabilities were not related to any biomechanical measures or demographics including age and body mass index. Overall, despite experiencing some back pain, these frontline firefighters are highly functional and did not show diminished physical or neuromuscular responses.

Adaptability of the load sharing between the longissimus and components of the multifidus muscle during isometric trunk extension in healthy individuals.

PURPOSE: Redundancy of the musculoskeletal system implies multiple strategies are theoretically available to coordinate back extensor muscles. This study investigated whether coordination between back muscles during a tightly constrained isometric trunk extension task varies within and between individuals, and whether this changes following brief exposure to activation feedback of a muscle. METHODS: Nine healthy participants performed three blocks of two repetitions of ramped isometric trunk extension in side-lying against resistance from 0-30% of maximum voluntary contraction over 30 s (force feedback). Between blocks, participants repeated contractions with visual feedback of electromyography (EMG) from either superficial (SM) or deep multifidus (DM), in two conditions; 'After SM' and 'After DM'. Intramuscular EMG was recorded from SM, DM, and longissimus (LG) simultaneously with shear wave elastography (SWE) from SM or DM. RESULTS: In the 'Natural' condition (force feedback only), group data showed incremental increases in EMG with force, with minor changes in distribution of activation between muscles as force increased. SM was the most active muscle during the 'Natural' condition, but with DM most active in some participants. Individual data showed that coordination between muscles differed substantially between repetitions and individuals. Brief exposure to EMG feedback altered coordination. SWE showed individual variation, but findings differed from EMG. CONCLUSION: This study revealed substantial variation in coordination between back extensor muscles within and between participants, and after exposure to feedback, in a tightly constrained task. Shear modulus revealed similar variation, but with an inconsistent relationship to EMG. These data highlight highly flexible control of back muscles.

Effect of age on shear modulus, muscle thickness, echo intensity of the upper limb, lower limb, and trunk muscles in healthy women.

PURPOSE: This study aimed to examine the effect of age on the mechanical properties, muscle size, and muscle quality in the upper and lower limb and trunk muscles. METHODS: We evaluated the shear modulus (G), muscle thickness (MT), and echo intensity (EI) of the upper and lower limb and trunk muscles of 83 healthy women (21-83-year-old). The G values of some limb muscles were measured in relaxed and stretched positions. RESULTS: Regarding the effect of age on G at the distinct positions, the G of the upper limb muscles were not significantly correlated with age in the relaxed and stretched positions. In contrast, the G of the iliacus showed a significant negative correlation in both positions. Additionally, the G of the rectus femoris had a significant negative correlation only in the relaxed position. Regarding differences among body parts, the G of the lower limb and oblique abdominal muscles showed a significant negative correlation, but no correlation in the upper limb, rectus abdominis, and back muscles. Moreover, MT showed a significant negative correlation with age in the lower limb, abdominal, and erector spinae muscles, but no correlation was detected in the upper limb and lumbar multifidus muscles. EI had a significant positive correlation in all the muscles. CONCLUSION: The effect of age on G depended on body parts, and the G of the lower limb and oblique abdominal muscles negatively associated with age. Additionally, G in the relaxed position may be more susceptible to aging than G in the stretched position.

Do MRI-derived muscle moment-arms in patients with chronic low back pain differ from healthy individuals? A comparative study.

OBJECTIVES: The present study aimed to estimate the trunk muscles moment-arms in low back pain (LBP) patients and compare this data to those of healthy individuals. This research further explored whether the difference of the moment-arms between these two is a contributing factor to LBP. METHODOLOGY: Fifty patients with CLBP (group A) and 25 healthy controls (group B) were enrolled. All participants were subjected to magnetic resonance imaging of lumbar spine. Muscle moment-arms were estimated on a T2W axial section parallel to the disc. RESULTS: There was statistically significant differences (p < 0.05) in the sagittal plane moment-arms at L1-L2 for right erector spinae (ES), bilateral psoas and rectus abdominis (RA), right quadratus lumborum (QL), and left obliques; bilateral ES, QL, RA, and right psoas at L2-L3; bilateral QL, RA, and obliques at L3-L4; bilateral RA and obliques at L4-L5; and bilateral psoas, RA, and obliques at L5-S1. There was no statistically significant difference (p < 0.05) in the coronal plane moment-arms except for left ES and QL at L1-L2; left QL and right RA at L3-L4; right RA and obliques at L4-L5; and bilateral ES and right RA at L5-S1. CONCLUSIONS: There was a significant difference in muscle moment-arms of the lumbar spine's prime stabilizer (psoas) and primary locomotors (rectus abdominis and obliques) between LBP patients and healthy individuals. This difference in the moment-arms leads to altered compressive forces at intervertebral discs and may be one of the risk factors for LBP.

A preliminary study on degenerate characteristics of lumbar and abdominal muscles in middle-aged and elderly people with varying bone mass.

BACKGROUND: With the wide application of QCT in the clinical assessment of osteoporosis and sarcopenia, the characteristics of musculoskeletal degeneration in middle-aged and elderly people need to be further revealed. We aimed to investigate the degenerate characteristics of lumbar and abdominal muscles in middle-aged and elderly people with varying bone mass. METHODS: A total of 430 patients aged 40-88 years were divided into normal, osteopenia, and osteoporosis groups according to quantitative computed tomography (QCT) criteria. The skeletal muscular mass indexes (SMIs) of five muscles [abdominal wall muscles (AWM), rectus abdominis (RA), psoas major muscle (PMM), posterior vertebral muscles (PVM), and paravertebral muscles (PM)] included in lumbar and abdominal muscles were measured by QCT. Differences in SMIs among three groups, as well as the correlation between SMIs and volumetric bone mineral density (vBMD) were analyzed. The areas under the curves (AUCs) for SMIs for prediction of low bone mass and osteoporosis were calculated. RESULTS: In male group, SMIs of RA and PM in osteopenia group were significantly lower than those in the normal group (P = 0.001 and 0.023, respectively). In female group, only SMI of RA in osteopenia group was significantly lower than that in the normal group (P = 0.007). SMI of RA was positively correlated with vBMD with the highest coefficients in male and female groups (r = 0.309 and 0.444, respectively). SMIs of AWM and RA had higher AUCs varying from 0.613 to 0.737 for prediction of low bone mass and osteoporosis in both genders. CONCLUSIONS: The changes of SMIs of the lumbar and abdominal muscles in patients with varying bone mass are asynchronous. SMI of RA is expected to be a promising imaging marker for predicting abnormal bone mass. TRIAL REGISTRATION: ChiCTR1900024511 (Registered 13-07-2019).

Potential of whole-body dual-energy X-ray absorptiometry to predict muscle size of psoas major, gluteus maximus and back muscles.

BACKGROUND: Measurement of trunk muscle cross-sectional area (CSA) using axial magnetic resonance imaging (MRI) is considered clinically meaningful for understanding several spinal pathologies, such as low back pain and spinal sagittal imbalance. However, it remains unclear whether trunk muscle mass (TMM) measured using dual-energy X-ray absorptiometry (DXA) can predict the trunk muscle CSA. The aim of this study is to determine if DXA-derived TMM is associated and predicts with CSA of paraspinal muscles and gluteus maximus measured using MRI in healthy volunteers. METHODS: A total of 48 healthy volunteers underwent whole-body DXA and MRI of the spinopelvic region. The CSA of the psoas major, back muscles, and gluteus maximus were measured on axial MRI. Correlations and linear regressions between the TMM measured using DXA and the CSA of each musculature were investigated. RESULTS: There was a weak correlation between TMM and CSA of the psoas major in men (r = 0.39, P = 0.0678), and the linear regression was y = 301.74x - 401.24 (R2 = 0.2976, P = 0.0070). A moderate correlation was found in women (r = 0.58, P = 0.0021), and the linear regression was y = 230.21x - 695.29 (R2 = 0.4445, P = 0.0003). Moderate correlations were observed between TMM and CSA of the back muscles in both men (r = 0.63, P = 0.0012) and women (r = 0.63, P = 0.0007), the linear regression was y = 468.52x + 3688.5 (R2 = 0.5505, P < 0.0001) in men and y = 477.39x + 2364.1 (R2 = 0.564, P < 0.0001) in women. There was a strong correlation between TMM and CSA of the gluteus maximus in men (r = 0.72, P < 0.0001), and the linear regression was y = 252.69x - 880.5 (R2 = 0.6906, P < 0.0001). A moderate correlation was found in women (r = 0.69, P < 0.0001), and the linear regression was y = 230.74x - 231.32 (R2 = 0.6542, P < 0.0001). CONCLUSIONS: The DXA-derived TMM was able to predict the CSA of the psoas major, back muscles, and gluteus maximus, and significantly correlated with the CSA of the back muscles and gluteus maximus. It might be a safer and cheaper alternative for evaluating the size of the back muscles and gluteus maximus.

Muscle synergy patterns as altered coordination strategies in individuals with chronic low back pain: a cross-sectional study.

BACKGROUND: Chronic low back pain (CLBP) is a highly prevalent disease with poorly understood underlying mechanisms. In particular, altered trunk muscle coordination in response to specific trunk tasks remains largely unknown. METHODS: We investigated the muscle synergies during 11 trunk movement and stability tasks in 15 healthy individuals (8 females and 7 males, aged 21. 3 (20.1-22.8) ± 0.6 years) and in 15 CLBP participants (8 females and 7 males, aged 20. 9 (20.2-22.6) ± 0.7 years) by recording the surface electromyographic activities of 12 back and abdominal muscles (six muscles unilaterally). Non-negative matrix factorization was performed to extract the muscle synergies. RESULTS: We found six trunk muscle synergies and temporal patterns in both groups. The high similarity of the trunk synergies and temporal patterns in the groups suggests that both groups share the common feature of the trunk coordination strategy. We also found that trunk synergies related to the lumbar erector spinae showed lower variability in the CLBP group. This may reflect the impaired back muscles that reshape the trunk synergies in the fixed structure of CLBP. Furthermore, the higher variability of trunk synergies in the other muscle regions such as in the latissimus dorsi and oblique externus, which were activated in trunk stability tasks in the CLBP group, represented more individual motor strategies when the trunk tasks were highly demanding. CONCLUSION: Our work provides the first demonstration that individual modular organization is fine-tuned while preserving the overall structures of trunk synergies and temporal patterns in the presence of persistent CLBP.

A Dynamic Procedure to Detect Maximum Voluntary Contractions in Low Back.

Surface electromyography (sEMG) is generally used to measure muscles' activity. The sEMG signal can be affected using several factors and vary among individuals and even measurement trials. Thus, to consistently evaluate data among individuals and trials, the maximum voluntary contraction (MVC) value is usually calculated and used to normalize sEMG signals. However, the sEMG amplitude collected from low back muscles can be frequently larger than that found when conventional MVC measurement procedures are used. To address this limitation, in this study, we proposed a new dynamic MVC measurement procedure for low back muscles. Inspired by weightlifting, we designed a detailed dynamic MVC procedure, and then collected data from 10 able-bodied participants and compared their performances using several conventional MVC procedures by normalizing the sEMG amplitude for the same test. The sEMG amplitude normalized by our dynamic MVC procedure showed a much lower value than those obtained using other procedures (Wilcoxon signed-rank test, with p < 0.05), indicating that the sEMG collected during dynamic MVC procedure had a larger amplitude than those of conventional MVC procedures. Therefore, our proposed dynamic MVC obtained sEMG amplitudes closer to its physiological maximum value and is thus more capable of normalizing the sEMG amplitude for low back muscles.

First dorsal interosseous muscle reconstruction: a systematic review of its attachments.

PURPOSE: The first dorsal interosseous (FDI) muscle, when impaired due to traumatic injuries or degenerative conditions, can be reanimated in various ways to restore pinch grip. These reconstructive techniques are planned based on a precise anatomical understanding of the FDI muscle. However, a review of the existing literature has brought to light controversy regarding its insertions. A systematic review of these descriptions is presented to appreciate these variations. METHODS: An electronic database search without exclusion by publication year and language was performed according to the Checklist for Anatomical Reviews and Meta-Analyses (CARMA) guidelines, using the PubMed, Scopus, Web of Science and Embase databases. An assessment of the methodological quality was performed. RESULTS: Thirteen studies were included in this article. There is general agreement that the FDI muscle contains two bellies and a bony insertion into the index finger proximal phalanx base. However, due to wide anatomic variation, differences were reported on whether there is a soft tissue insertion. When this was found, the included studies differed on how commonly this occurs (between 1.4% and 78%), where it inserts. Other sites of distal insertions reported include the metacarpophalangeal capsule, the interosseous hood and an assemblage nucleus on the volar plate. CONCLUSIONS: Our systematic review, focusing on the insertion of the FDI muscle, summarizes the existing knowledge on its anatomy and variations, thereby facilitating better understanding of its function and surgical planning for reconstruction.

Effect of office chair design features on lumbar spine posture, muscle activity and perceived pain during prolonged sitting.

Chair design features are typically compared using multiple seats, which can lead to confounding effects. Using a single chair, configurable to four designs (control, lumbar support, seat pan tilt and scapular relief), we investigated the effect of chair design on spine posture and movement, muscle activity and perceived pain in a sample of 31 asymptomatic adults. A total of 39% of the population were classified as pain developers, having significantly higher peak pain levels across most body regions. The lumbar support and seat pan tilt condition resulted in more neutral spine and pelvic postures. Greater muscle activity was found in the seat pan condition and non-pain developers displayed lower spine muscle activation levels overall. Despite some improvements in spine posture, sitting-induced pain was present in the study sample at similar proportions to those reported previously. Future studies may consider investigating interventions targeted to sitting-induced pain developers as opposed to the general population. Practitioner summary: Four office chair configurations were tested. The lumbar support and seat pan tilt conditions resulted in the most neutral back posture but did not mitigate the clinically significant levels of sitting-induced pain experienced by a large portion of the tested sample. Future work should target interventions to these individuals.

Imaging High-Risk Atherothrombosis Using a Novel Fibrin-Binding Positron Emission Tomography Probe.

BACKGROUND AND PURPOSE: High-risk atherosclerosis is an underlying cause of cardiovascular events, yet identifying the specific patient population at immediate risk is still challenging. Here, we used a rabbit model of atherosclerotic plaque rupture and human carotid endarterectomy specimens to describe the potential of molecular fibrin imaging as a tool to identify thrombotic plaques. METHODS: Atherosclerotic plaques in rabbits were induced using a high-cholesterol diet and aortic balloon injury (N=13). Pharmacological triggering was used in a group of rabbits (n=9) to induce plaque disruption. Animals were grouped into thrombotic and nonthrombotic plaque groups based on gross pathology (gold standard). All animals were injected with a novel fibrin-specific probe 68Ga-CM246 followed by positron emission tomography (PET)/magnetic resonance imaging 90 minutes later. 68Ga-CM246 was quantified on the PET images using tissue-to-background (back muscle) ratios and standardized uptake value. RESULTS: Both tissue-to-background (back muscle) ratios and standardized uptake value were significantly higher in the thrombotic versus nonthrombotic group (P<0.05). Ex vivo PET and autoradiography of the abdominal aorta correlated positively with in vivo PET measurements. Plaque disruption identified by 68Ga-CM246 PET agreed with gross pathology assessment (85%). In ex vivo surgical specimens obtained from patients undergoing elective carotid endarterectomy (N=12), 68Ga-CM246 showed significantly higher binding to carotid plaques compared to a D-cysteine nonbinding control probe. CONCLUSIONS: We demonstrated that molecular fibrin PET imaging using 68Ga-CM246 could be a useful tool to diagnose experimental and clinical atherothrombosis. Based on our initial results using human carotid plaque specimens, in vivo molecular imaging studies are warranted to test 68Ga-CM246 PET as a tool to stratify risk in atherosclerotic patients.

The influence of experimental low back pain on neural networks involved in the control of lumbar erector spinae muscles.

Low back pain (LBP) often modifies spine motor control, but the neural origin of these motor control changes remains largely unexplored. This study aimed to determine the impact of experimental low back pain on the excitability of cortical, subcortical, and spinal networks involved in the control of back muscles. Thirty healthy subjects were recruited and allocated to pain (capsaicin and heat) or control (heat) groups. Corticospinal excitability (motor-evoked potential; MEP) and intracortical networks were assessed by single- and paired-pulse transcranial magnetic stimulation, respectively. Electrical vestibular stimulation was applied to assess vestibulospinal excitability (vestibular MEP; VMEP) and the stretch reflex for excitability of the spinal or supraspinal loop (R1 and R2, respectively). Evoked back motor responses were measured before, during, and after pain induction. Nonparametric rank-based ANOVA determined if pain modulated motor neural networks. A decrease of R1 amplitude was present after the pain disappearance (P = 0.01) whereas an increase was observed in the control group (P = 0.03) compared with the R1 amplitude measured at prepain and preheat period, respectively (group × time interaction, P < 0.001). No difference in MEP and VMEP amplitude was present during and after pain (P > 0.05). During experimental LBP, no change in cortical, subcortical, or spinal networks was observed. After pain disappearance, the reduction of the R1 amplitude without modification of MEP and VMEP amplitude suggests a reduction in spinal excitability potentially combined with an increase in descending drives. The absence of effect during pain needs to be further explored.NEW & NOTEWORTHY In the presence of experimental low back pain, spinal, subcortical, and cortical motor networks involved in the control of back muscles were not modified. However, once the pain disappeared, a reduction in motoneuronal excitability was observed without change in corticospinal and vestibulospinal excitability, suggesting a reduction in descending drive. Experimental low back pain may elicit long-term plasticity even after pain extinction.

Can training of a skilled pelvic movement change corticomotor control of back muscles? Comparison of single and paired-pulse transcranial magnetic stimulation.

Evidence suggests excitability of the motor cortex (M1) changes in response to motor skill learning of the upper limb. Few studies have examined immediate changes in corticospinal excitability and intra-cortical mechanisms following motor learning in the lower back. Further, it is unknown which transcranial magnetic stimulation (TMS) paradigms are likely to reveal changes in cortical function in this region. This study aimed to (1) compare corticospinal excitability and intra-cortical mechanisms in the lower back region of M1 before and after a single session of lumbopelvic tilt motor learning task in healthy people and (2) compare these measures between two TMS coils and two methods of recruitment curve (RC) acquisition. Twenty-eight young participants (23.6 ± 4.6 years) completed a lumbopelvic tilting task involving three 5-min blocks. Single-pulse (RC from 70% to 150% of active motor threshold) and paired-pulse TMS measures (ICF, SICF and SICI) were undertaken before (using 2 coils: figure-of-8 and double cone) and after (using double cone coil only) training. RCs were also acquired using a traditional and rapid method. A significant increase in corticospinal excitability was found after training as measured by RC intensities, but this was not related to the RC slope. No significant differences were found for paired-pulse measures after training. Finally, there was good agreement between RC parameters when measured with the two different TMS coils or different acquisition methods (traditional vs. rapid). Changes in corticospinal excitability after a single session of lumbopelvic motor learning task are seen, but these changes are not explained by changes in intra-cortical mechanisms.

Construction of circRNA-related ceRNA networks in longissimus dorsi muscle of Queshan Black and Large White pigs.

Circular RNA (circRNA) is a class of non-coding RNA (ncRNA) that plays an important regulatory role in various biological processes of the organisms and has a major function in muscle growth and development. However, its molecular mechanisms of how it regulates pork quality remain unclear at present. In this study, we compared the longissimus dorsi (LD) muscle expression profiles of Queshan Black (QS) and Large White (LW) pigs to explore the role of circRNAs in meat quality using transcriptome sequencing. A total of 62 differentially expressed circRNAs (DECs), including 46 up- and 16 down-regulated, 39 differentially expressed miRNAs (DEmiRNAs), including 21 up- and 18 down-regulated and 404 differentially expressed mRNAs (DEMs), including 174 up- and 230 down-regulated were identified, and most circRNAs were composed of exons. Our results indicated that the DEC parent genes and DEMs were enriched in the positive regulation of fast-twitch skeletal muscle fiber contraction, relaxation of skeletal muscle, regulation of myoblast proliferation, AMPK signaling pathway, Wnt and Jak-STAT signaling pathway. Furthermore, circSETBP1/ssc-miR-149/PIK3CD and circGUCY2C/ssc-miR-425-3p/CFL1 were selected by constructing the competitive endogenous RNA (ceRNA) regulatory network, circSETBP1, circGUCY2C, PIK3CD and CFL1 had low expression level in QS, while ssc-miR-149 and ssc-miR-425-3p had higher expression level than LW, our analysis revealed that circSETBP1, circGUCY2C, ssc-miR-149, ssc-miR-425-3p, PIK3CD and CFL1 were associated with lipid regulation, cell proliferation and differentiation, so the two ceRNAs regulatory networks may play an important role in regulating intramuscular fat (IMF) deposition, thereby affecting pork quality. In conclusion, we described the gene regulation by the circRNA-miRNA-mRNA ceRNA networks by comparing QS and LW pigs LD muscle transcriptome, and the two new circRNA-associated ceRNA regulatory networks that could help to elucidate the formation mechanism of pork quality. The results provide a theoretical basis for further understanding the genetic mechanism of meat quality formation.

Impact of Skeletal Muscle Measurements by Chest Computed Tomography on Survival and Postoperative Complications in Patients with Soft Tissue Sarcoma.

This study aims to evaluate whether sarcopenia, measured by chest computed tomography (CT), affects survival outcomes and postoperative complications in soft tissue sarcoma (STS) patients undergoing surgery. In this retrospective study, CT scans of 79 patients were reviewed to measure pectoralis and T12 vertebra muscle area. Both were then adjusted for height (cm2/m2) as pectoralis muscle index (PMI) and T12 vertebra muscle index (TMI). Analyses were performed by dichotomizing muscle indices at gender-specific 50th percentile; PMI and TMI < 50th percentile were defined as low, and ≥50th percentile as high. Overall postsurgical complication rate (PCR) was 16%. Median length of hospital stay (LOHS) was 10 days (3-90). PMI and TMI were significantly lower in women (p = 0.02, p = 0.04). Median body mass index was significantly higher in high PMI and TMI groups (p = 0.01 for both). PCR and LOHS were similar between low and high PMI and TMI groups. Median follow-up was 29 months, 37 patients had recurrence and 23 died. No significant difference was noted between low and high PMI and TMI groups, in terms of disease-free or overall survival. PMI and TMI as measured by chest CT had no impact on survival outcomes or postoperative complications in localized STS.