Skeletal Muscle Depletion and Major Postoperative Complications in Locally-Advanced Head and Neck Cancer: A Comparison between Ultrasound of Rectus Femoris Muscle and Neck Cross-Sectional Imaging

Skeletal muscle mass (SMM) depletion has been validated in many surgical fields as independent predictor of complications through cross-sectional imaging. We evaluated SMM depletion in a stage III-IV head and neck cancer cohort, comparing the accuracy of CT/MRI at C3 level with ultrasound (US) of rectus femoris muscle (RF) in terms of prediction of major complications. Patients submitted to surgery were recruited from 2016 to 2021. SMM was estimated on CT/MRI by calculating the sum of the cross-sectional area (CSA) of the sternocleidomastoid and paravertebral muscles at C3 level and its height-indexed value (cervical skeletal muscle index, CSMI) and on US by computing the CSA of RF. Specific thresholds were defined for both US and CT/MRI according to ROC curve in terms of best prediction of 30-day major complications to detect sarcopenic subjects (40–53%). Sixty-five patients completed the study. At univariate analysis, major complications were associated to lower RF CSA, lower CSA at C3 level and lower CSMI, together with previous radiotherapy, higher ASA score and higher modified frailty index (mFI). At multivariate analysis RF CSA (OR 7.07, p = 0.004), CSA at C3 level (OR 6.74, p = 0.005) and CSMI (OR 4.02, p = 0.025) were confirmed as independent predictors in three different models including radiotherapy, ASA score and mFI. This analysis proved the value of SMM depletion as predictor of major complications in a head and neck cancer cohort, either defined on cross-sectional imaging at C3 or on US of RF.

Muscle Fatigue Revisited – Insights From Optically Pumped Magnetometers

So far, surface electromyography (sEMG) has been the method of choice to detect and evaluate muscle fatigue. However, recent advancements in non-cryogenic quantum sensors, such as optically pumped magnetometers (OPMs), enable interesting possibilities to flexibly record biomagnetic signals. Yet, a magnetomyographic investigation of muscular fatigue is still missing. Here, we simultaneously used sEMG (4 surface electrode) and OPM-based magnetomyography (OPM-MMG, 4 sensors) to detect muscle fatigue during a 3 × 1-min isometric contractions of the left rectus femoris muscle in 7 healthy participants. Both signals exhibited the characteristic spectral compression distinctive for muscle fatigue. OPM-MMG and sEMG slope values, used to quantify the spectral compression of the signals, were positively correlated, displaying similarity between the techniques. Additionally, the analysis of the different components of the magnetic field vector enabled speculations regarding the propagation of the muscle action potentials (MAPs). Altogether these results show the feasibility of the magnetomyographic approach with OPMs and propose a potential alternative to sEMG for the study of muscle fatigue.

Rectus femoris muscle thickness and cross-sectional area on ultrasonography may predict isometric and isokinetic knee extension strength: A cross-sectional study

Objective: To examine the relationship between knee extensor strength and quadriceps muscle architecture evaluated with ultrasonography during relaxed and contracted situations. Materials and Methods: A total of 40 healthy participants (age range 18-40), doing sports at a recreational level were included. Pennation angle, muscle thickness, and cross-sectional area of the vastus medialis, vastus lateralis, and rectus femoris muscles were measured firstly during rest while participants are sitting on an isokinetic dynamometer with their knees at 0° and 60° of flexion. Thereafter, ultrasound evaluations were performed during maximal isometric contraction at 60° knee flexion and maximal isokinetic contraction at 30°/sec and 60°/sec speeds. The architectural parameters were correlated with peak isometric (measured at 60° knee flexion) and isokinetic (measured at 30°/sec and 60°/sec angular velocities) torque values. Results: Pennation angle (p<0.001), muscle thickness (p<0.001) and muscle cross-sectional area (p<0.001) of the vastus medialis muscle during rest, and isometric and isokinetic maximal contractions were higher than the vastus lateralis and rectus femoris muscles. Pennation angle, muscle thickness and muscle cross-sectional area parameters measured during rest, and isometric and isokinetic maximal contractions in the vastus medialis (r=0.39-0.64, p<0.05-0.01) and vastus lateralis (r=0.36-0.68, p<0.05-0.01) showed weak to moderate correlations with isometric and isokinetic peak torque. In rectus femoris muscle, on the other hand, except the weak correlation in pennation angle (r=0.35-0.49, p<0.05-0.01), muscle thickness (r=0.74-0.80, p<0.001) and cross-sectional area (r=0.71-0.80, p<0.001) had a moderate to strong correlation with isometric and isokinetic strength. Stepwise regression analysis indicated that rectus femoris cross-sectional area measured during knee relaxed at 60° flexion (R2=0.532-0.610) and rectus femoris muscle thickness measured during isometric and isokinetic contraction modes (R2=0.538-0.600) were decisive to predict the isometric and isokinetic strength of the quadriceps muscle. Conclusion: Contrary to pennation angle, muscle thickness and cross-sectional area of the rectus femoris measured during relaxed and contracted conditions may be determinative in predicting isometric and isokinetic strength.

Central Tendon Injury Impairs Regional Neuromuscular Activation of the Rectus Femoris Muscle

We aimed to uncover which rectus femoris strain injury types affect regional activation within the rectus femoris. The rectus femoris has a region-specific functional role; the proximal region of the rectus femoris contributes more than the middle and distal regions during hip flexion. Although a history of strain injury modifies the region-specific functional role within the rectus femoris, it was not obvious which rectus femoris strain injury types affect regional activation within it. We studied 12 soccer players with a history of rectus femoris strain injury. Injury data were obtained from a questionnaire survey and magnetic resonance imaging. To confirm the region-specific functional role of the rectus femoris, surface multichannel electromyographic signals were recorded. Accordingly, eight legs had a history of central tendon injury, four had a history of myofascial junction injury, and four had a healed strain injury. When the injury was limited to the central tendon, the region-specific functional role disappeared. The region-specific functional role was confirmed when the injury was outside the central part. The neuromuscular function was also inhibited when the longitudinal range of the injured region was long. Our findings suggest that a central tendon injury with a long injury length impairs regional neuromuscular activation of the rectus femoris muscle.

One Session Effects of Knee Motion Visualization Using Immersive Virtual Reality in Patients with Hemophilic Arthropathy

(1) Background: Hemophilic knee arthropathy is characterized by a loss of muscle mass and decreased strength of the quadriceps muscle. The visualization of movement aims to favor the recruitment of the motor system in the same premotor and parietal areas, as would happen with the active execution of the observed action. The aim was to evaluate changes in quadriceps activation in patients with hemophilic knee arthropathy following immersive VR visualization of knee extension movements. (2) Methods: We recruited 13 patients with severe hemophilia A and knee arthropathy. Patients underwent a 15 min session of immersive VR visualization of knee extension movements. The quadriceps muscle activation was evaluated by surface electromyography. (3) Results: After the intervention, there were no changes in the muscle activation of vastus medialis, vastus lateralis, or rectus femoris muscles. There was a large effect size of changes in rectus femoris muscle activation. Age and knee joint damage did not correlate with changes in quadriceps activation. Dominance, inhibitor development, and type of treatment were not related with post-intervention muscle activation. (4) Conclusions: A session of immersive VR visualization of knee extension movement does not modify quadriceps muscle activation. A specific protocol for patients with hemophilic knee arthropathy may be effective in improving the activation of the rectus femoris muscle.

Rehabilitation after a Complete Avulsion of the Proximal Rectus Femoris Muscle: Considerations from a Case Report

Background: A complete avulsion of the proximal rectus femoris muscle is a rare but severity injury. There is a lack of substantial information for its operative treatment and rehabilitation; in particular there is a lack of biomechanical data to evaluate long-term outcomes. Case presentation: The case report presents the injury mechanism and surgical treatment of a complete avulsion of the proximal rectus femoris muscle in a 41-year-old recreational endurance athlete. Moreover, within a one-year follow-up period, different biomechanical tests were performed to get more functional insights into changes in neuromuscular control, structural muscle characteristics, and endurance performance. Within the first month post-surgery, an almost total neuromuscular inhibition of the rectus femoris muscle was present. A stepwise reduction in inter-limb compensations was observable (e.g., in crank torque during cycling) during the rehabilitation. Muscular intra-limb compensations were shown at six months post-surgery and even one year after surgery, which were also represented in the long-term adaption of the muscle characteristics and leg volumes. A changed motor control strategy was shown by asymmetric muscle activation patterns during ergometer cycling, while the power output was almost symmetric. During rehabilitation, there might be a benefit to normalizing neuromuscular muscle activation in ergometer cycling using higher loads. Conclusions: While the endurance performance recovered after six months, asymmetries in neuromuscular control and structural muscle characteristics indicate the long-term presence of inter- and intra-limb compensation strategies.

Muscle fatigue revisited - Insights from optically pumped magnetometers

Muscle fatigue is well characterized electromyographically, nevertheless only information about summed potential differences is detectable. In contrast, recently developed quantum sensors optically pumped magnetometers (OPMs) offer the advantage of recording both the electrical current propagation in the muscle as well as its geometry, by measuring the magnetic field generated by the muscular action potentials. Magnetomyographic investigation of muscle fatigue is still lacking and it is an open question whether fatigue is characterized similarly in magnetomyography (MMG) compared to electromyography (EMG). Herein, we investigated the muscle fatigue during a 3x1-min strong isometric contraction of the rectus femoris muscle of 12 healthy subjects using simultaneous EMG-MMG (4-channel surface EMG and 4 OPM along the rectus femoris muscle). Both EMG and MMG showed the characteristic frequency decrease in the signal magnitude during isometric contraction, which is typical for muscle fatigue. In addition, it was shown that the main part of this frequency decrease seems to occur in the circular component of the magnetic field around the muscle fibers and less longitudinally along the muscle fibers. Overall, these results show not only that magnetomyography is capable of reproducing the electromyographic standards in identifying muscular fatigue, but it also adds relevant information about the spatial characterization of the signal. Therefore, OPM-MMG offers new insights for the study of muscular activity and might serve as a new, supplementary neurophysiological method.