Intramuscular hemodynamics in bilateral erector spinae muscles in symmetrical and asymmetrical postures with and without loading

Automated quantification of the anatomic accuracy of muscle paths and its application in an image-based subject-specific modeling workflow for adult spinal deformity

BACKGROUND

Musculoskeletal models (MSKM) can non-invasively evaluate the effect of altered muscle geometry and physiology on locomotor function. Nevertheless, this requires anatomically accurate muscle paths throughout functional ranges of motion. However, reference data to evaluate such muscle paths is rarely available, including in adult spinal deformity (ASD). Although this degenerative disorder alters muscle geometry and physiology, these parameters are not available to inform clinical decision-making as generic MSKM cannot account for these alterations, and reliable ASD-specific modeling workflows do not currently exist.

RESEARCH QUESTION

Can an efficient workflow be developed for evaluating and optimizing the anatomic accuracy of dynamic muscle paths in personalized MSKM and applied for reliable spinal motion simulations in ASD?

METHODS

A workflow was developed to automatically analyze anatomic muscle accuracy throughout predefined ranges of motion in terms of muscle-bone penetration, muscle action, moment arm magnitude, and discontinuities. Erector spinae, multifidus, and psoas muscles were semi-automatically segmented in magnetic resonance images of one healthy and two ASD subjects. Next, their muscle representation, insertion sites, and complexity were iteratively refined with the above workflow to generate subject-specific MSKM and compare them against state-of-the-art generic MSKM.

RESULTS

All muscles in the subject-specific MSKM were anatomically accurate, except for discontinuities in 3.81 % (psoas) and 0.37 % (multifidus) of moment arm curves across motions and subjects. In contrast, scaled generic MSKM were consistently associated with muscle-bone penetration, decreased moment arm magnitude, and opposite muscle actions.

SIGNIFICANCE

This novel workflow is the first to allow for an efficient evaluation of the anatomic accuracy of dynamic muscle paths. Its application in MSKM of ASD patients resulted in subject-specific muscle paths, with an anatomically correct muscle geometry, while preventing bone penetration during the representative range of motions. The workflow is promising to enable biomechanical analyses of ASD with an accuracy beyond that of scaled generic models.

Electromyography and sonomyography analysis of the tibialis anterior: a cross sectional study

Background

Foot dorsiflexion plays an essential role in both controlling balance and human gait. Electromyography (EMG) and sonomyography (SMG) can provide information on several aspects of muscle function. The aim was to establish the relationship between the EMG and SMG variables during isotonic contractions of foot dorsiflexors.

Methods

Twenty-seven healthy young adults performed the foot dorsiflexion test on a device designed ad hoc. EMG variables were maximum peak and area under the curve. Muscular architecture variables were muscle thickness and pennation angle. Descriptive statistical analysis, inferential analysis and a multivariate linear regression model were carried out. The confidence level was established with a statistically significant p-value of less than 0.05.

Results

The correlation between EMG variables and SMG variables was r = 0.462 (p < 0.05). The linear regression model to the dependent variable “peak normalized tibialis anterior (TA)” from the independent variables “pennation angle and thickness”, was significant (p = 0.002) with an explained variance of R² = 0.693 and SEE = 0.16.

Conclusions

There is a significant relationship and degree of contribution between EMG and SMG variables during isotonic contractions of the TA muscle. Our results suggest that EMG and SMG can be feasible tools for monitoring and assessment of foot dorsiflexors. TA muscle parameterization and assessment is relevant in order to know that increased strength accelerates the recovery of lower limb injuries.

Mode of action of cupping--local metabolism and pain thresholds in neck pain patients and healthy subjects

OBJECTIVES

Cupping worldwide has been part of traditional medicine systems and is in the western world used as CAM therapy mainly for treating pain syndromes. The mode of action is up to now unclear. In order to investigate its mechanism we measured in parallel metabolic changes in the tissue under the cupping glass and pressure pain thresholds.

DESIGN AND INTERVENTIONS

In 12 volunteers (6 healthy subjects and 6 patients with chronic neck pain) a microdialysis system was implanted subcutaneously on both sides (left and right) above the trapezius muscle. After baseline measures cupping was performed at one randomly selected side (left or right), the other side served as control. Every 20 min during baseline measures and for 280 min after cupping, microdialysis probes for detection of lactate, pyruvate, glucose and glycerin were taken. In addition, pain thresholds were measured before and after cupping with algometry.

RESULTS

Cupping resulted in a strong increase of lactate (beginning 160 min after cupping until the end of the measurements) and the lactate/pyruvate ratio, indicating an anaerobe metabolism in the surrounding tissue. Baseline pain thresholds were non-significantly lower in neck pain patients compared to healthy controls and slightly increased immediately after cupping (p<0.05 compared to baseline close to the area of cupping in healthy subjects and on the foot in neck pain patients). After 280 min no more significant changes of pain thresholds were detected.

CONCLUSIONS

Cupping induces >280 min lasting anaerobe metabolism in the subcutaneous tissue and increases immediate pressure pain thresholds in some areas.

Back extensor muscle fatigue at submaximal workloads assessed using frequency banding of the electromyographic signal

BACKGROUND

Changes in the mean or median frequency of the electromyographic (EMG) power spectrum are often used to assess skeletal muscle fatigue. A more global analysis of the spectral changes using frequency banding may provide a more sensitive measure of fatigue than changes in mean or median frequency. So, the aim of the present study was to characterize changes in different power spectrum frequency bands and compare these with changes in median frequency.

METHODS

Twenty male subjects performed isometric contractions of the back muscles in an isometric dynamometer at 30%, 40%, 50% and 60% of maximum voluntary contraction. During each contraction, surface EMG signals were recorded from the right and left longissimus thoracis muscles, and endurance time was measured. The EMG power spectra were divided into four frequency bands (20-50 Hz; 50-80 Hz; 80-110 Hz; 110-140 Hz) and changes in power in each band with fatigue were compared with changes in median frequency.

FINDINGS

The percentage changes in 20-50 Hz band were greater than in all other and the rate of change in power, indicated by the slope, was also greatest in 20-50 Hz band. Also, 20-50 Hz band had a greater change in power than the median frequency.

INTERPRETATION

Power in the low frequency part of the EMG power spectrum increases with fatigue in a load-dependent manner. The rate of change in low frequency power may be a useful indicator of fatigue rate or "fatigability" in the back muscles. Also, changes in low frequency power are more evident than changes in the median frequency.