Ultrasound-Based Rectus Femoris and Parasternal Intercostal Muscle Thickness and Weaning Outcomes in Critically Ill Patients

Fatigue and muscle weakness are common complaints in COVID-19 survivors. However, little is still known about the skeletal muscle qualitative and quantitative characteristics after hospitalization due to moderate and severe COVID-19. To assess rectus femoris and vastus intermedius muscle thickness (MT) and rectus femoris echo intensity (EI) and to establish its association with demographic, clinical, functional, and inflammatory parameters in long COVID patients after hospital discharge. Cross-sectional study with 312 COVID-19 patients (53.53% male; age: 54.59 ± 13.50 years), with a laboratory-confirmed diagnosis of COVID-19. Patients were assessed 3-11 months after hospital discharge. We evaluated MT of the right rectus femoris and vastus intermedius and EI of the right rectus femoris using a portable ultrasound system, 6-13 MHz, broadband linear transducer. We corrected EI using the subcutaneous fat thickness. Ultrasonographic parameters were tested in association with demographic (sex and age); functional (Handgrip strength measurement, Timed Up and Go, 1 min Sit-to-Stand test, EuroQoL-5 Dimensions-5 Levels, World Health Organization Disability Assessment Schedule (WHODAS 2.0), Post-COVID-19 Functional Status, Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT), Medical Research Council (MRC) sum score, Borg Dyspnea Scale, MRC Dyspnea score, Visual Analogue Scale (VAS), Epworth Sleepiness Scale, Insomnia Severity Index, Functional Independence Measurement (FIM), and Functional Oral Intake Scale); clinical (length of hospital stay, intubation, and presence of comorbidities such as systemic hypertension, diabetes, obesity, chronic obstructive pulmonary disease, asthma), and inflammatory data assessed by the C-reactive protein and D-dimer serum concentrations. Rectus femoris MT was associated with age, handgrip strength, Epworth Sleepiness Scale, and subcutaneous fat thickness (r2 = 27.51%; p < 0.0001). Vastus intermedius MT was associated with age, pain intensity, handgrip strength, Epworth Sleepiness scale, FIM, and time since hospital discharge (r2 = 21.12%; p < 0.0001). Rectus femoris EI was significantly associated with the male sex, TUG, Epworth Sleepiness Scale, and C-Reactive Protein levels (r2 = 44.39%; p < 0.0001). Mean MT of rectus femoris and vastus intermedius are significantly different (p < 0.001). After hospital discharge, long COVID patients present qualitative and quantitative skeletal muscle characteristics associated with a combination of demographic, clinical, and functional parameters.

Current evidence suggests that the eccentric action of the quadriceps during load acceptance is essential for shock attenuation. Using Ultrasound imaging (US), rectus femoris (RF) muscle thickness can be successfully quantified in real time during a gait task. PURPOSE: To characterize the RF thickness changes during the loading and terminal phase of gait. METHODS: Eighteen healthy participants (23±2yrs; 1.7±0.1m; 65.9±9.4kg) completed 3 gait trials at a self-selected pace (1.06±0.17 m/s). Lower extremity kinematics and RF thickness values were assessed concurrently during the stance phase of gait. High-speed motion analysis cameras sampling at 200 Hz were used to track marker trajectory for kinematic data. US was collected at 87 Hz with a 16-mm 5-14 MHz linear array transducer placed 60% of the distance between the anterior superior iliac spine and base of the patella. US measures were collected in a longitudinal view. The ultrasound cart traveled alongside the participant over a custom-built track system. USI images were processed on MATLAB using custom software. Time of peak knee flexion from kinematic data was used to split stance into loading phase and terminal stance. Paired t-tests were used to compare peak and average values of RF thickness during loading phase and terminal stance. Alpha level was set a priori at p<0.05. RESULTS: RF had a significantly greater (p<0.05) peak muscle thickness during terminal stance (4.8±1.98mm) than loading phase (3.9±2.23mm). However, no significant difference (p>0.05) was noted in average RF muscle thickness between terminal stance (2.8±1.10mm) and loading phase (3.2±2.10mm). CONCLUSIONS: Peak architectural changes of the RF muscle during the loading phase of stance were significantly different from the values present during the terminal stance. This finding suggests that an early and most likely stronger contraction of the RF muscle is associated with load acceptance. Our findings are the first to our knowledge to characterize RF thickness changes during stance in a healthy population. Some traumatic injuries may impair RF muscle function specifically during the loading phase, and consequently lead to joint damage. Future studies should characterize muscle properties and function in individuals with pathological conditions (e.g. post-traumatic osteoarthritis).

Point-of-care ultrasound can be used to assess muscle thickness. However, its reliability has not been fully evaluated. This study aimed to assess the intrarater and inter-rater reliability of point-of-care ultrasound for the estimation of quadriceps and rectus femoris thickness in patients from a rehabilitation setting. This is a cross-sectional study. This study was conducted at the Department of Physical Medicine and Rehabilitation of a tertiary care hospital. Twenty-nine inpatients consecutively selected after admission. Four observers, two trained and two untrained, used point-of-care ultrasound to measure quadriceps femoris and rectus femoris thickness. Each observer performed two measurements followed by a second set of two measurements three hours later. Intraclass correlation coefficients (ICC) were then calculated. Both intrarater and inter-rater ICC were higher than 0.888 for both quadriceps and rectus femoris measurements. Reliability was highest when ICC were calculated based on the average of two measurements, with the intrarater ICC being of 0.956 (95% CI: 0.937-0.970) for rectus femoris and of 0.966 (95% CI: 0.951-0.976) for quadriceps femoris; and with the inter-rater ICC being of 0.919 (95% CI: 0.863-0.957) for rectus femoris and 0.945 (95% CI: 0.907- 0.971) for quadriceps femoris. Trained and untrained observers did not have significantly different ICC values. These results suggest that point-of-care ultrasound is a reliable option to measure muscle thickness of knee extensors by the same or different observers. Measuring knee extensors thickness may aid to adequately modulate treatment choices in patients with disability. This study suggests that quadriceps and rectus femoris muscle thickness measured after a short training course, by either an experienced or inexperienced clinician, presents high reliability. Reliability can be increased if the average of two measurements is used. Besides being inexpensive and portable, point-of-care ultrasound is a reliable tool for measuring knee extensors' thickness, rendering it potentially adequate to be used in clinical practice.

The purpose of this study was to examine the effect of subcutaneous adipose tissue (SCAT) thickness and rectus femoris (RF) muscle thickness on RF and vastus intermedius (VI) echo intensity using human cadavers. The echo intensity of the RF and VI was measured in 11 legs of seven cadavers under three conditions: intact condition (Model 1), SCAT removed (Model 2), and SCAT and RF removed (Model 3). RF echo intensity in Model 1 (69.2 ± 20.3 a.u.) was significantly lower than that in Model 2 (83.4 ± 15.9 a.u.) (P = 0.003). VI echo intensity in Models 1 to 3 showed similar results to RF echo intensity (P = 0.003 to 0.001). Regarding the relationship between VI echo intensity and VI muscle thickness, the regression lines shifted upward in a parallel fashion in the order Model 1, Model 2, and Model 3. Multiple regression analysis revealed that the variation in RF echo intensity was explained by RF muscle thickness (P = 0.036) and SCAT thickness (P = 0.001), while the variation in VI echo intensity was explained by RF muscle thickness (P = 0.035). These results suggest that SCAT thickness and RF muscle thickness induce lower RF echo intensity, while RF muscle thickness induces lower VI echo intensity.

Anterior cruciate ligament reconstruction induces deleterious neuromuscular alterations. Musculoskeletal ultrasonography provides an accessible method to quantify muscle size and quality in patients with anterior cruciate ligament reconstruction who suffer from persistent skeletal muscle atrophy. This study compares rectus femoris and vastus intermedius muscle thicknesses and echo intensities using extended field-of-view ultrasonography in individuals with a history of anterior cruciate ligament reconstruction versus non-injured controls. Twenty-six individuals with previous anterior cruciate ligament reconstruction and 20 controls were participated in this study. Extended field-of-view ultrasonography was used to analyze the muscle thickness in the proximal, middle, and distal regions of the thigh, while the echo intensity was measured to assess the muscle quality. Findings indicate significant asymmetries in the muscle thickness (p<0.01 and η p 2=0.312) and echo intensity (p=0.024 and η p 2=0.111) for the anterior cruciate ligament reconstruction group, favoring the uninvolved leg, with no site-specific differences between groups. Results show muscle-specific size differences, with greater vastus intermedius muscle thickness than rectus femoris muscle thickness in controls (p<0.01 and d=0.609), but no difference between muscles in either leg of the anterior cruciate ligament reconstruction group (p>0.05 and d=0.094). Overall, these results highlight unique skeletal muscle changes between the biarticular rectus femoris and the monoarticular vastus intermedius following anterior cruciate ligament reconstruction, likely reflecting postoperative deficiencies in knee extensor function.

Rectus femoris and vastus intermedius muscle thickness as a predictor of mortality in elderly patients with pneumonia.

Background: The purpose was to investigate the content, construct, and criterion validity of muscle ultrasound in a mixed cohort of participants recovering from mild and critical COVID-19.Methods: A secondary analysis of a prospective cross-sectional study was conducted on data obtained from a battery of muscle and physical function assessments including a muscle biopsy and muscle ultrasonography (US). Rectus femoris (RF) muscle thickness (mT), quadricep complex (QC) mT, RF muscle cross-sectional area (CSA) using 2D freeform trace and estimated from Feret’s diameter, and RF echo intensity (EI) were assessed with US. Muscle fiber CSA, fiber type, protein content in muscle fibers, extracellular matrix content (ECM; wheat-germ agglutin), and percent area of collagen in ECM (picrosirius red) were examined from vastus lateralis muscle biopsies. Spearman rho correlations (r) were performed to assess validity of ultrasound parameters.Results: Thirty-three individuals participated including 11 patients surviving critical COVID-19, 15 individuals recovering from mild-COVID, and 7 controls. There were several significant correlations between RF mT, QC mT, RF CSA, and RF EI with age, comorbid burden, body-mass index, and measures of muscle strength, muscle power, and physical function (range r = 0.35–0.83). RF Feret’s CSA correlated to CSA of type II muscle fibers (r = 0.41, p = 0.022) and the average size of all muscle fibers (r = 0.39, p = 0.031). RF EI was correlated with collagen in muscle ECM (r = 0.53, p = 0.003) and protein content in muscle tissue (r = −0.52, p = 0.012).Conclusion: Muscle size and quality measured using US has moderate content and construct validity, and to lesser extent, fair to moderate criterion validity in a mixed cohort of individuals recovering from COVID. Muscle ultrasound quality (EI) appears to be sensitive at detecting muscle dysfunction as it is associated with strength, power, physical function, and collagen distribution in a mixed group of individuals recovering from COVID-19.

Association of baseline diaphragm, rectus femoris and vastus intermedius muscle thickness with weaning from mechanical ventilation

Ultrasound is a useful tool for assessing muscle status. Estimation equations based on ultrasound measurements have been used to approximate appendicular skeletal muscle mass (ASM). However, age-related changes in skeletal muscle may influence the accuracy of ultrasound-based measurements, as compared to other established techniques. This study aimed to examine these associations across various age groups and to determine whether age-specific models are required for ASM estimation. A total of 265 subjects were analyzed and divided into three age groups: young (Group A, n = 94), middle-aged (Group B, n = 84), and older (Group C, n = 87). Rectus femoris (RF) muscle thickness (MT) was measured using ultrasound and ASM assessed using bioelectrical impedance analysis, which served as the reference method. Multivariate linear regression models were developed for each age group and for total group (Groups A+B+C) using RF MT as the primary predictor. All models showed high adjusted R2 values (0.881-0.955). Group-specific models demonstrating greater accuracy than total group model, based on lower root mean square error, the mean absolute error, and higher adjusted R2. These findings highlight the clinical relevance of using group-specific models to enhance the accuracy of ultrasound-based ASM estimation, thereby improving the screening and early identification of sarcopenia. Future validation in diverse populations and clinical settings is warranted.

To develop a predictive model based on preoperative quadriceps ultrasound measurements to determine frailty status in elderly patients undergoing abdominal surgery. The clinical data of 148 elderly patients who underwent abdominal surgery from July 2018 to June 2022 were retrospectively analyzed. The patients were assessed for frailty using the Fried Frailty Phenotype Assessment Scale after operation and divided into a no-frailty group (n=89) and a frailty group (n=59). The differences in the patient's clinical data, perioperative indexes, and imaging indexes were compared. The risk factors affecting the frailty status of elderly patients undergoing abdominal surgery were analyzed by logistic regression. The efficacy of the prediction model was evaluated by receiver operating characteristic (ROC) curve, with model validity confirmed through calibration curves and decision curve analysis (DCA). The proportion of patients with age ≥80 and BMI ≥23 kg/m2 in the frailty group was significantly higher than that in the no-frailty group (both P<0.01). The operation duration and postoperative hospital stay in the frail group were significantly longer the non-frail group, and the complication rate within postoperative 7 days was significantly higher than that in the non-frail group (all P<0.05). The cross-sectional area of rectus femoris muscle, vastus medialis muscle thickness, vastus intermedius muscle thickness, rectus femoris muscle thickness, and lateral femoris muscle thickness were significantly less in the frail group than those of the no-frail group (all P<0.001). Multifactorial logistic regression analysis showed that BMI, surgical duration, vastus medialis muscle thickness, vastus intermedius muscle thickness, rectus femoris muscle thickness, and lateral femoral muscle thickness were independent risk factors affecting frailty status in elderly patients undergoing abdominal surgery (all P<0.05). The predictive model demonstrated high accuracy with an AUC of 0.926. BMI and thickness of all quadriceps muscle components were significant factors affecting the frailty status of elderly patients undergoing abdominal surgery. In addition, the developed model, with excellent accuracy, offers a potential tool for preoperative risk assessment in this patient population.

Ultrasound measurement of rectus femoris muscle thickness as a quick screening test for sarcopenia assessment

BackgroundFrailty is a geriatric syndrome that is characterized by increased vulnerability to intrinsic and extrinsic stressors due to decreased biologic reserves. Muscle ultrasound (US) is a valid and reliable method for assessing muscle quantity in older adults. The study aims to examine the relationship between frailty definitions and US-derived muscle parameters.MethodsWe conducted a cross-sectional study with type 2 diabetes mellitus outpatients in a tertiary hospital, and all participants underwent a comprehensive geriatric assessment. For frailty assessment, the Fried Frailty Phenotype (FFP), the Clinical Frailty Scale (CFS), and the Edmonton Frailty Scale (EFS) were performed. Muscle US measurements included Gastrocnemius Medialis (GM) muscle thickness, GM fascicle length, GM pennation angle, Rectus Femoris (RF) muscle thickness, Rectus Femoris cross-sectional area (RFCSA), Rectus Abdominis (RA) muscle thickness, External Oblique (EO) muscle thickness, Internal Oblique (IO) muscle thickness, and Transverse Abdominis (TA) muscle thickness.ResultsIn all, 373 participants were included in the study. The median age of participants was 72.7 ± 5.9 years, and 64.6% of them were female. According to the FFP, 18.2% of the participants were living with frailty, 56% of them were pre-frail; 57.4% of them were living with frailty according to the CFS; 25.2% of them were living with frailty, and 20.6% of them were pre-frail according to the EFS. The FFP, CFS, and EFS scores were related to muscle thickness of GM, RF, and RA, fascicle length of GM, and pennation angle of GM and RFCSA. Particularly, GM pennation angle, RF muscle thickness, and RFCSA were associated with an increased risk of frailty. Besides muscle thickness of GM, RF, and RA, fascicle length of GM, pennation angle of GM, and RFCSA were significant for predicting the presence of frailty.ConclusionsUS-derived regional muscle measurements are associated with frailty definitions (in both physical, cumulative deficit, and multidimensional models) in a diabetic geriatric population.

This study was planned to determine the muscle architecture (pennation angle, muscle fiber length, and muscle thickness) and its relationship to lower extremity muscle strength in patients with Multiple Sclerosis (pwMS). The muscle architecture (pennation angle, muscle fiber length, and muscle thickness) and lower extremity muscle strength were assessed in 33 pwMS [13 Relapsing-Remitting MS (RRMS), 5 Primary Progressive MS (PPMS), 5 Secondary Progressive MS (SPMS), and 11 matched healthy controls (HC)]. Muscle architecture features were assessed with ultrasonography and muscle strength were assessed with a digital hand-held dynamometer. The rectus femoris muscle thickness and pennation angle, gastrocnemius muscle thickness, and the tibialis anterior pennation angle were significantly lower in pwMS compared to HC (p < 0.05). The strength of hip flexors, hip extensors, knee extensors, foot plantar, and foot dorsi flexors were lower in pwMS. In PPMS group, muscle strength of hip flexors was lower than RRMS and SPMS groups, and muscle strength of foot dorsi flexors was lower than RRMS (p < 0.05). In pwMS, positive correlations were found, between knee flexor strength and biceps femoris pennation angle. Also knee extensor strength and rectus femoris fiber length and muscle thickness were correlated positively (p < 0.05). According to our results the muscle architecture is affected in MS. The determination of architectural changes of lower extremity muscles may guide the arrangement of optimal strength exercises in functional rehabilitation programs.ClinicalTrials: NCT03766698.

Does Rest Time before Ultrasonography Imaging Affect Quadriceps Femoris Muscle Thickness, Cross-Sectional Area and Echo Intensity Measurements?

Objective This study aimed to investigate the association between vastus medialis obliquus (VMO), rectus femoris (RF), and vastus lateralis (VL) muscle thickness and quadriceps isokinetic strength, single-leg hop performance, and self-reported knee function in male athletes who had undergone anterior cruciate ligament reconstruction (ACLR). Methods Forty-two male athletes [mean ± standard deviation, age: 21.4 ± 3.4 years], who had undergone ACLR and had cleared to return to activity, were included in this study. Real-time ultrasound images of VMO, RF, and VL thicknesses were obtained from both reconstructed and contralateral limbs. Concentric quadriceps peak torque at 60°/s and 180°/s, single-leg hop for Distance (SLHD), and self-reported knee function scores were also assessed. Linear regression analysis and student t tests were used for statistical analysis. Results In reconstructed limb, greater VMO, RF, and VL thicknesses were associated with greater quadriceps peak torque at 60°/s (p = .008, r2 = 0.46) and at 180°/s (p = .006, r2 = 0.47). Greater quadriceps thickness was related to greater SLHD score in reconstructed limb (p = .002, r2 = 0.21). Self-reported knee function scores were not related to quadriceps thickness. VMO, RF, and VL thicknesses were smaller in reconstructed limb compared to contralateral limb (p < .001, p = .01, and p = .002, respectively). Conclusion Quadriceps thickness by using ultrasound was associated with concentric quadriceps strength and single-leg hop distance in individuals who had undergone ACLR. However, quadriceps thickness was not related to self-reported knee function. The ultrasonography may be included in the evaluation of the knee function after ACLR, and it may be a useful and easy method in the follow-up of the quadriceps strength recovery following ACLR.