Ultrasound Imaging Analysis of the Lumbar Multifidus Muscle Echo Intensity: Intra-Rater and Inter-Rater Reliability of a Novice and an Experienced Rater

The effects of exercise therapy on lumbar muscle structure in low back pain: A systematic review and meta-analysis

BACKGROUND

Changes in muscle structure are observed in people with low back pain (LBP). Although exercise therapy is arguably one of the most commonly used methods to treat LBP, evidence regarding its effects on muscle structure is still lacking.

OBJECTIVES

To answer the following questions: (1) What are the effects of exercise therapy on lumbar muscle structure in people with LBP and (2) which type of exercise intervention has the greatest effects?

METHODS

Six electronic databases were systematically searched. The RoB 2 tool and the ROBINS-I tool were used to blindly assess the Risk of bias (RoB), and the RevMan 5 tool was used for the meta-analysis. Due to heterogeneity, the various exercise interventions were classified into 4 groups. Interventions that could not be classified into 1 of these 4 groups were not included in the meta-analyses and were qualitatively analysed.

RESULTS

In total, 984 records were retrieved, of which 34 articles were included. The meta-analyses showed that when considering the overall effect size per muscle structural outcome in chronic LBP (cLBP), exercise therapy showed significant positive effects on Lumbar Multifidus (LM) muscle thickness (MT) and LM cross-sectional area (CSA), but not on Lumbar Erector Spinae (LES) CSA and Quadratus Lumborum CSA. Considering the different intervention groups, significant positive effects were observed for: (1) "Motor control + stabilization" with small effect on LM MT, (2) "Stabilization" with medium effect on LM MT, and large effect on LM CSA, and (3) "Motor control + Stabilization + Lumbar strengthening" with large effect on LM MT and LES CSA. There were no significant effects observed for "Lumbar strengthening".

CONCLUSIONS

Overall, exercise therapy has a positive effect on lumbar muscle structural properties in a cLBP population, with a combination of Motor control + Stabilization + Lumbar strengthening giving the best results.

DATABASE REGISTRATION

This systematic review was registered on PROSPERO (CRD42021232583).

Examiner experience moderates reliability of human lower extremity muscle ultrasound measurement - a double blinded measurement error study

Structural muscle properties are critical in health and athletic settings, with magnetic resonance imaging considered the gold standard assessment procedure under static conditions due to its reliability and objectivity. Practical limitations, including cost and accessibility, have led to the increasing use of ultrasound as an alternative for skeletal muscle morphological parameters. However, ultrasound measurements are sensitive to evaluation conditions and assessor experience, which has not been sufficiently explored, yet. Therefore, this study investigated the influence of assessor experience on the reliability of ultrasound measurements. A double-blind design was used, involving an experienced assessor (> 12,000 images for several years) and multiple inexperienced assessors (< 100 images) to collect data from 39 recreationally active participants. Measurements of muscle architecture were conducted in the leg muscles over two consecutive days, generating 1,248 ultrasound images. Relative and absolute reliability were analyzed using intraclass correlation coefficients (ICCs), standard error of measurement, minimal detectable change, mean absolute error (MAE), mean absolute percentage error (MAPE) and Bland-Altman analyses. Relative reliability was good to excellent in all measurement spots and time-points for muscle thickness (ICC = 0.76-0.98) irrespective of assessor experience, except for the inter-day comparison for the gastrocnemius lateralis by the inexperienced assessors, (ICC = 0.58). The pennation angle assessment ranged from insufficient to excellent reliability (ICC = 0.18-0.94) and experience contributed greatly to better results. The random error for the inexperienced assessors was reflected in two- to three-times higher MAEs/MAPEs and limits of agreement in the Bland-Altman analyses, respectively. The findings emphasize the importance of experience and standardization in achieving reliable ultrasound data, particularly for (a) sensitive parameters like the pennation angle and/or (b) inter-day, intra-subject comparisons.

Reliability of Panoramic Ultrasound in Assessing Rectus Femoris Size, Shape, and Brightness: An Inter-Examiner Study

Extended field-of-view ultrasound (US) imaging, also known as panoramic US, represents a technical advance that allows for complete visualization of large musculoskeletal structures, which are often limited in conventional 2D US images. Currently, there is no evidence examining whether the experience of examiners influences muscle shape deformations that may arise during the glide of the transducer in panoramic US acquisition. As no studies using panoramic US have analyzed whether two examiners with differing levels of experience might obtain varying scores in size, shape, or brightness during the US assessment of the rectus femoris muscle, our aim was to analyze the inter-examiner reliability of panoramic US imaging acquisition in determining muscle size, shape, and brightness between two examiners. Additionally, we sought to investigate whether the examiners' experience plays a significant role in muscle deformations during imaging acquisition by assessing score differences. Shape (circularity, aspect ratio, and roundness), size (cross-sectional area and perimeter), and brightness (mean echo intensity) were analyzed in 39 volunteers. Intraclass correlation coefficients (ICCs), standard error of measurements (SEM), minimal detectable changes (MDC), and coefficient of absolute errors (CAE%) were calculated. All parameters evaluated showed no significant differences between the two examiners (p > 0.05). Panoramic US proved to be reliable, regardless of examiner experience, as no deformations were observed. Further research is needed to corroborate the validity of panoramic US by comparing this method with gold standard techniques.

Comparison of multifidus muscle intramuscular fat by ultrasound echo intensity and fat-water based MR images in individuals with chronic low back pain

PURPOSE

The aim of this observational cross-sectional study was to examine correlations of intramuscular fat content in lumbar multifidus (LM) by comparing muscle echo intensity (EI) and percent fat signal fraction (%FSF) generated from ultrasound (US) and magnetic resonance (MR) images, respectively.

METHODS

MRI and US images from 25 participants (16 females, 9 males) selected from a cohort of patients with chronic low back pain (CLBP) were used. Images were acquired bilaterally, at the L4 and L5 levels (e.g., 4 sites). EI measurements were acquired by manually tracing the cross-sectional border of LM. Mean EI of three US images per site were analyzed (e.g., raw EI). A correction factor for subcutaneous fat thickness (SFT) was also calculated and applied (e.g., corrected EI). Corresponding fat and water MR images were used to acquire %FSF measurements. Intra-rater reliability was assessed by intraclass coefficients (ICC). Pearson correlations and simple linear regression were used to assess the relationship between %FSF, raw EI and corrected EI measurements.

RESULTS

The intra-rater ICCs for all measurements were moderate to excellent. Correlations between %FSF vs. raw EI and corrected EI were moderate to strong (0.40 < r < 0.52) and (0.40 < r < 0.51), respectively. Moderate correlations between SFT and EI were also identified.

CONCLUSION

US is a low-cost, non-invasive, accessible, and reliable method to examine muscle composition, and presents a promising solution for assessing and monitoring the effect of different treatment options for CLBP in clinical settings.

Correlation between Body Composition and Inter-Examiner Errors for Assessing Lumbar Multifidus Muscle Size, Shape and Quality Metrics with Ultrasound Imaging

Ultrasound imaging (US) is widely used in several healthcare disciplines (including physiotherapy) for assessing multiple muscle metrics such as muscle morphology and quality. Since measuring instruments are required to demonstrate their reliability, accuracy, sensitivity, and specificity prior to their use in clinical and research settings, identifying factors affecting their diagnostic accuracy is essential. Since previous studies analyzed the impact of sociodemographic but not body composition characteristics in US errors, this study aimed to assess whether body composition metrics are correlated with ultrasound measurement errors. B-mode images of the lumbar multifidus muscle at the fifth lumbar vertebral level (L5) were acquired and analyzed in 49 healthy volunteers by two examiners (one experienced and one novel). Cross-sectional area, muscle perimeter and mean echo intensity were calculated bilaterally. A multivariate correlation matrix was calculated for assessing the inter-examiner differences with body composition metrics. Results demonstrated excellent reliability (intraclass correlation coefficient, ICC > 0.9) for assessing the muscle cross-sectional area and perimeter, and good reliability for assessing the muscle shape and mean echo intensity (ICC > 0.7). Inter-examiner errors for estimating muscle size were correlated with participants' age (p value, p < 0.01), weight (p < 0.05), total and trunk lean mass (both, p < 0.01) and water volume (p < 0.05). Greater shape descriptors and mean brightness disagreements were correlated with older ages (p < 0.05) and total lean mass (p < 0.05). No correlations between age and body composition metrics were found (p > 0.05). This study found US to be a reliable tool for assessing muscle size, shape and mean brightness. Although aging showed no correlations with body composition changes in this sample, it was the main factor correlated with US measurement errors.

Effects of Virtual Reality Exercises versus Isokinetic Exercises in comparison with Conventional Exercises on the Imaging Findings and Inflammatory Biomarker Changes in Soccer Players with Non-Specific Low Back Pain: A Randomized Controlled Trial

Chronic non-specific low back pain (CNLBP) is the most common musculoskeletal problem. The purpose of this study was to investigate the effects of advanced physiotherapeutic exercise programs on imaging findings and inflammatory biomarkers in soccer players with CNLBP. In total, 60 CNLBP participants were divided into virtual reality exercise (VRE; n = 20), isokinetic exercise (IKE; n = 20), and conventional exercise (n = 20) groups. Pain intensity, imaging findings (muscle cross-sectional area (CSA) and muscle thickness), and changes in inflammatory biomarkers (CRP, TNF-α, IL-2, IL-4, and IL-6) were measured at baseline and after four weeks. After four weeks of intervention, there was a significant improvement (p = 0.001) in pain intensity for the VRE vs. IKE (0.7; CI 95% 0.38 to 1.07) and VRE vs. conventional (3.0 CI 95% 2.68 to 3.31) groups. The IKE group showed a greater number of significant changes in muscle CSA and muscle thickness than the other two groups (p < 0.001). Moreover, the VRE group showed significant improvement in inflammatory biomarker measures compared with the other two groups (p < 0.001). In CNLBP, virtual and isokinetic exercises had equal effects on reducing pain intensity. Isokinetic exercise is beneficial in increasing the muscle CSA and thickness, and virtual exercises are helpful for attenuating the inflammation process in soccer players with CNLBP.