Search Results (101)

Background: The occlusal angle (OA), influenced by pillow height, may affect muscle tension in the head and neck. However, its optimal range for minimizing muscle activation has not been clearly defined. Objective: This study aimed to investigate the effects of OA on the resting muscle activity of masticatory and cervical muscles and to identify an optimal OA range using cluster analysis and linear mixed-effects modeling. Methods: The resting muscle activities of the masseter (MAS), temporalis (TEM), sternocleidomastoid (SCM), and posterior vertebral muscles (PVM) were measured at OA conditions modulated by pillow heights of 0, 5, and 10 cm at 0, 1, and 5 min in the supine position. Intraclass correlation coefficients (ICCs) assessed measurement reliability. Statistical analyses included ANOVA, ROC curve analysis, k-means clustering, and linear mixed-effects models. Results: MAS and TEM resting muscle activity ratio (RMR) significantly increased with larger OA values (p < 0.001), while SCM showed decreased activation (p = 0.001). An OA range of 105°–111° was identified as the center of a low-activity cluster, and an upper cut-off of 138° was associated with potential muscular overload. ICC values for MAS and SCM ranged from 0.82 to 0.89, indicating excellent test–retest reliability. Conclusions: OA modulated by pillow height is a modifiable factor that influences muscle activity. An OA of 105°–111° may serve as a practical comfort zone, especially for individuals at risk of TMDs. Full article

Medical Infrared Thermography (MIT) is a safe, non-invasive technique for assessing temperature changes on the skin’s surface that may reflect pathological processes in the underlying tissues. In temporomandibular joint disorders (TMDs), which are often associated with reduced mobility and muscle overactivity, tissue metabolism and blood flow may be diminished, resulting in localized hypothermia. Aim: The purpose of this study was to evaluate muscle tone in the masseter, suprahyoid, and sternocleidomastoid muscles following the application of two types of occlusal splints, a Michigan splint and a double repositioning splint, based on temperature changes recorded using a Fluke Ti401 PRO thermal imaging camera. Materials and Methods: Sixty dental students diagnosed with TMDs were enrolled in this study. After applying the inclusion and exclusion criteria, participants were randomly assigned to one of two groups. Group M received a Michigan splint, while group D was treated with a double repositioning splint. Results: The type of occlusal splint influenced both temperature distribution and muscle tone. In the double repositioning splint group, temperature decreased by approximately 0.8 °C between T1 and T3, whereas in the Michigan splint group, temperature increased by approximately 0.7 °C over the same period. Conclusions: Occlusal splint design has a measurable impact on temperature distribution and muscle activity. The double repositioning splint appears to be more effective in promoting short-term muscle relaxation and may provide relief for patients experiencing muscular or myofascial TMD symptoms. Full article

Background: This study aimed to investigate the acute changes in muscle and tendon viscoelastic properties in response to a progressive treadmill VO₂max test among professional male soccer players. Methods: Bilateral assessments at five sites—the Achilles tendon (AT), biceps femoris, semitendinosus, rectus femoris (RF), and sternocleidomastoid (SCM)—measured tone (oscillation frequency), dynamic stiffness, logarithmic decrement (elasticity), stress relaxation time, and creep. Each site was probed five times and values averaged. Repeated-measures ANOVA (Time × Side) with Bonferroni correction tested pre- to post-exercise changes; Pearson’s r examined associations with VO₂max. Results: Significant Time effects (all p < 0.05) were observed for RF frequency (η_p² = 0.226), RF creep (η_p² = 0.144), AT stiffness (η_p² ≈ 0.035), AT frequency (η_p² = 0.035), and SCM frequency (η_p² = 0.037). Post-exercise, right AT stiffness fell by 65 ± 14 N/m (p = 0.015), while left AT stiffness rose by 22 ± 9 N/m (p = 0.015). RF stiffness decreased by 28 ± 6 N/m (p < 0.001) and tone by 1.2 ± 0.3 Hz (p < 0.001), with creep (+0.08 ± 0.02; p < 0.001) and relaxation time (+1.5 ± 0.7 ms; p < 0.001) increasing. SCM tone declined by 0.8 ± 0.4 Hz (p = 0.010). Baseline RF properties—frequency (r = −0.597), stiffness (r = −0.59), relaxation time (r = 0.53), and creep (r = 0.48)—correlated moderately with VO₂max (all p < 0.05). Conclusions: These findings suggest that viscoelastic adaptations to exhaustive aerobic exercise are tissue- and side-specific, and that rectus femoris viscoelastic properties may serve as potential indicators of endurance readiness. Full article

Introduction: Masseter vestibular evoked myogenic potentials (M-VEMPs) are a recent tool for assessing a vestibulo-trigeminal pathway departing from the saccule, similarly to cervical VEMPs (C-VEMPs), that evaluate saccular function via the sternocleidomastoid muscle. M-VEMPs may offer a complementary diagnostic value in vestibular neuritis (VN). Methods: This retrospective study analysed M-VEMPs and C-VEMPs in 28 monolateral patients and 1 bilateral (30 ears) diagnosed with VN between 2023 and 2024. Diagnostic evaluation included video head impulse tests (VHIT), caloric tests, ocular VEMPs, and, in a few cases, electromyography (EMG) of the sternocleidomastoid muscle. M-VEMPs were elicited using 500 Hz tone bursts at 97 dB nHL. Results were compared based on the topography of vestibular involvement and muscle response concordance. Results: M-VEMPs were always present in patients with superior VN and intact saccular function, showing consistent results with normal C-VEMPs. In some cases, with saccular dysfunction, M-VEMPs were preserved despite the absence of C-VEMPs, suggesting greater robustness. One patient with herpes zoster (HZ) involving both the VIII and trigeminal nerves showed absent M-VEMPs, indicating trigeminal pathway involvement. Edentulous patients showed reduced or absent M-VEMPs due to compromised masseter muscle electromyography activity. Conclusions: M-VEMPs are reliable and often concordant with C-VEMPs in VN but may reveal additional diagnostic information in discordant or complex cases. They are particularly useful in identifying trigeminal involvement but are limited in patients with poor masseter muscle function. Further studies are needed to clarify their full diagnostic potential. Full article

Background and Objectives: This study aimed to discuss positional changes in the sternocleidomastoid (SCM) muscle and vagus nerve with head position, their effect on the surgical path, positional variations, the selection of an appropriate position for surgery, their effects on the surgical procedure, and complications by using peroperative ultrasonography. Materials and Methods: Vagal nerve stimulation surgery patients over the age of 18 years were included. Peroperative ultrasonography images were scanned, and changes in head position and anatomical and positional variations in the SCM muscle and vagus nerve at the surgical incision level were examined. Results: SCM localization was most frequently observed in the lateral aspect of the carotid sheath (n:16) in neutral position, while it was mostly observed in the medial aspect of the carotid sheath (n:16) at a 15 degree rotation. The vagus nerve was mostly observed between the jugular vein and carotid artery in neutral position (n:21), and it was observed at the same position at a 15 degree rotation (n:17). The positional change of the SCM muscle with head position was found to be statistically significant (p < 0.001), while the positional change of the vagus nerve was not (p:0.198). Conclusions: The SCM muscle closes the surgical path with head rotation by either deviating over the carotid sheath or increasing its deviation. In addition to its anatomical variations, the vagus nerve shows different positional changes with head rotation. Deciding on the head position in vagal nerve stimulation surgery, using peroperative ultrasonography rather than a routine position, may be effective in reducing surgical time and possible complications. Full article

Background: Ectopic fat deposition refers to lipid accumulation that affects metabolic function and tissue characteristics. Japanese Black cattle are distinguished by their high intramuscular fat content, which contributes to their distinctive character. However, the genetic mechanisms underlying these traits remain unclear. This study compared gene expression patterns in different muscle regions to identify genes associated with intramuscular fat accumulation. First, we conducted RNA sequencing to analyze differences in gene expression profiles among the sternocleidomastoid, pectoralis minor, and pectoralis major muscles. In addition, single-cell nuclear RNA sequencing was conducted to investigate the cellular composition of these muscle tissues. Results: Distinct gene expression patterns were observed among the different muscles. In the pectoralis, which contains a high proportion of intramuscular fat, adipocyte-related genes such as FABP4, SCD, and ADIPOQ were highly expressed. In addition, lipases such as PNPLA2, LPL, MGLL, and LIPE were predominantly expressed in intramuscular fat, whereas PLA2G12A, PLD3, and ALOX15 were specifically expressed in myofibers. Moreover, a subclass of fibro–adipogenic progenitor cells that differentiate into intramuscular adipocytes was found to express genes related to microenvironment formation, including ICAM1, TGFBRs, and members of the COL4A family. Conclusions: This study provides novel insight into the genetic regulation of intramuscular fat accumulation. It improves our understanding of the molecular mechanisms underlying their distinctive meat characteristics. Full article

Background/Objectives: The present study aimed to investigate the relationship between forward head posture (FHP) and the mechanical properties of muscles as well as the influence of FHP on them. Methods: To define participants with FHP, craniovertebral angle (CVA) was measured. All participants were divided into two groups in accordance with their CVA: the experimental group (FHP) consisting of participants with a CVA below 50°, and the control group (CON) consisting of participants with a CVA above 50°. The tone, stiffness, and elasticity of the upper trapezius muscle (UT), the middle trapezius muscle (MT), the lower trapezius muscle (LT), the sternocleidomastoid muscle (SCM), the splenius capitis muscle (SC), the pectoralis major muscle (PM), and the serratus anterior muscle (SA) were measured using MyotonPro (Myoton AS, Tallinn, Estonia). Results: Both tone and stiffness in the UT were statistically significant (p < 0.05). In addition, stiffness in the LT was statistically significant (p < 0.05). No significant differences were found in tone, stiffness, and elasticity of the MT, SCM, SC, PM, and SA muscles (p > 0.05). A significant correlation was found between FHP and both tone and stiffness in the UT (r = −0.731, p = 0.000; r = −0.749, p = 0.000, respectively). No significant correlation was found between FHP and tone, stiffness, and elasticity of the MT, LT, SCM, SC, PM, and SA muscles. Conclusions: Since the UT was the muscle in which changes in mechanical properties were first induced by FHP, an approach targeting UT is necessary as a priority when treating patients with FHP. Full article

Background: The prolonged use of smartphones may lead to cervical posture deformities and other associated issues. Among these conditions, cervical extension type is one of the most commonly observed, characterized by increased cervical lordosis, forward head posture, and thoracic kyphosis. These biomechanical changes may lead to neck pain, a restricted range of motion (ROM), and heightened cervical muscle tone. The purpose of this study was to evaluate the impact of combining cervical stabilization exercises with either scapular stabilization or thoracic exercises on the mechanical properties of cervical muscles, the pressure pain threshold (PPT), and the ROM in individuals with cervical extension type. Methods: This study included 32 subjects with cervical extension type who were randomly divided into two groups: 16 subjects were placed in either the cervical and scapular stabilization exercises group (CSG) or the cervical stabilization with thoracic exercises group (CTG). After four weeks of exercise intervention, the following assessments were conducted: measurement of muscle tone, stiffness, and elasticity of the sternocleidomastoid (SCM) and upper trapezius (UT) muscles using Myoton PRO; evaluation of the PPT of the SCM and UT muscles using a pressure pain threshold meter; and assessment of cervical ROM (extension, flexion, and rotation) using motion analysis equipment. Results: Both groups showed significant differences in muscle tone, stiffness, elasticity, PPT, and cervical ROM (p < 0.05). The PPT of the UT muscle was significantly improved in the CSG compared to the CTG (p < 0.05). Conclusions: There were significant improvements in muscle tone, stiffness, elasticity, pain, and cervical ROM after exercise intervention in both groups of subjects with cervical extension. Cervical stabilization exercises, along with scapular stabilization, have better effects on improving UT muscle pain. Full article

Aim: The aim of this study was to compare balance performance and electromyographic activity in individuals with COPD, with and without sarcopenia. Method: Thirty-five patients with COPD were classified with and without sarcopenia according to EWGSOP criteria. Balance was assessed using a force platform under four conditions: standing with feet apart and eyes opened (FHEO), eyes closed (FHEC), on an unstable surface (US), and on one leg (OLS). The surface electromyography activity of lower limb muscles and trunks was recorded. Additionally, the timed up and go test (TUG) and the Brief Balance Evaluation Systems Test (Brief-BESTest) were also utilized. Results: Under the FHEO, FHEC, and US conditions, individuals with sarcopenia demonstrated increased velocities, larger oscillation amplitudes, and greater center of pressure displacements under the US condition (p ≤ 0.02). They also showed a higher activation of the scalene, sternocleidomastoid, and abdominal muscles during OLS, along with a reduced activation of the tibialis anterior during OLS and US, and a decreased activation of the vastus medialis during FHEC and US (p ≤ 0.04). Furthermore, sarcopenic COPD patients exhibited poorer performance on the TUG and Brief-BESTest compared to their non-sarcopenic counterparts (p ≤ 0.02). Conclusions: Individuals with COPD and sarcopenia demonstrated greater instability in both bipedal stances and on unstable surfaces, as well as poorer performance in both dynamic and static balance assessments. Furthermore, these individuals exhibited reduced muscular activation in the lower limbs compared to those without sarcopenia. Full article

The haptic fidelity of biomimetic materials used in the design of procedural task trainers is of growing interest to the medical community. Shore hardness has been proposed as a method for assessing tissue biomechanics and replicating the results as a way to increase the fidelity of biomimetics to tissues. However, there is limited research on the reliability of human tissue measurements using Shore scales. Using human tissues (internal carotid artery [ICA], internal jugular vein [IJV], vagus nerve [VN], sternocleidomastoid muscle [SCM], and overlying skin [skin]), this study evaluates (1) the inter-rater reliability of Shore hardness measurements, (2) examines the relationship between tissue thickness and hardness, and (3) investigates the impact of a measurement method (freehand vs. durometer stand). Preserved tissues, specifically a liver and components of the anterior triangle of the neck, were extracted from cadavers and measured by three independent raters using digital Shore durometers. Testing revealed that although Shore A demonstrated better inter-rater reliability compared to Shore OO, both scales exhibited poor-to-moderate reliability. ICC values for Shore A ranged from 0.21 to 0.80 and were statistically significant (p < 0.05) for all tissue types except the SCM. In contrast, Shore OO demonstrated poorer reliability, with ICC values ranging from 0.00 to 0.41. The ICC values were only significant for the ICA, IJV, and VN (p < 0.05). An inverse correlation between tissue thickness and hardness on the Shore A scale was found for all tissues and was significant (p < 0.05) for ICA, VN, and skin. There were mixed results for the correlation between tissue thickness and hardness on the Shore OO scale (−0.06–0.92), and only IJV had a statistically significant correlation (p < 0.05). Finally, the median hardness values on the Shore OO scale were significantly greater when measured using a durometer stand vs. freehand (Z = 4.78, p < 0.05). In summary, when using appropriate standards and addressing the challenges of tissue thickness and variability in freehand measures, Shore hardness has the potential to be used by clinicians in the clinical setting and in the selection of biomimetic materials in the design of task trainers. Full article

Background/Objectives: Posterior neck, trapezius, and interscapular pain, exacerbated by poor posture such as forward head and rounded shoulders, is common. In this study, we aimed to assess the clinical outcomes of isotonic saline injections at nerve entrapment points (NEPs) within the sternocleidomastoid (SCM) and scalenus medius (SM) muscles for alleviating spinal accessory nerve (SAN) and dorsal scapular nerve (DSN) compression in patients suffering from posterior neck, trapezius, and interscapular pain. Methods: In this retrospective study, 68 patients were included, with 34 receiving isotonic saline injections and 34 undergoing Extracorporeal Shock Wave Therapy (ESWT) as a control. The clinical outcomes were evaluated using the Visual Analog Scale (VAS) and Percent Pain Intensity Difference (PPID) before and after therapy. The effectiveness of isotonic saline injections targeting NEPs in the SCM and SM muscles in relieving pain associated with SAN and DSN entrapment was assessed. Results: Both treatments significantly reduced VAS and PPID scores, with injection therapy showing a larger treatment effect size (Cohen’s d: 3.521 for VAS and 3.521 for PPID) compared to ESWT (Cohen’s d: 1.379 for VAS and 1.710 for PPID). The mean clinically important difference observed for VAS was 4.2, exceeding the expected value of 2.6, indicating a substantial improvement in pain and patient quality of life. Conclusions: Isotonic saline injections at the NEPs of SAN and DSN within the SCM and SM muscles might potentially reduce posterior neck, trapezius, and interscapular pain associated with possible nerve entrapment, without causing complications. Further research is needed to validate these findings in larger, controlled trials. Full article

Background: This paper presents the outcomes of employing the inferiorly based rotated sternocleidomastoid muscle flap in complex tracheal reconstruction/repair scenarios, focusing on the key objectives of ensuring stable airway, functional digestive tract and patient survival. Methods: A retrospective analysis was performed for patients treated at two medical centers (A.O. San Camillo Forlanini, Rome, and A.O.U. Careggi, Florence) from 2011 to 2023, in which the sternocleidomastoid muscle (SCM) flap, detached from the mastoid and basicranium, was rotated on the lower pivot directly onto the repair site and pedicled to the sternal origin to ensure the continuity of the airway. Average postoperative hospital stay, follow-up period and patient survival were analyzed. Follow-up assessments encompassed bronchoscopies and CT scans conducted at intervals of 15 and 28 days, and subsequently at 3 and 9 months. Results: A total of five patients were enrolled in this study. These cases included one patient with anterior tracheal wall lesions with abundant tissue loss, one patient with an anterior wall necrosis due to descending cervical mediastinitis and three patients with extra-long tracheoesophageal fistulas (TEFs) (greater than 4.5 cm or >30% of the total tracheal length). In the case of the direct repair of a TEF with a proximal tracheal stenosis, the sternocleidomastoid muscle was used to reconstruct the tissue deficit caused by extensive loss of substance in the left lateral side of the tracheal wall. In case of repair through exclusion of the TEF, the sternocleidomastoid muscle was interposed between the visceral sutures after exclusion of the TEF by an endomechanical device, in one case even substituting the membranous part of the tracheal wall. Our technique allows rotation on the sternal head of the sternocleidomastoid muscle with the lowest rotation radius, pedicled to the sternal origin, detached from the mastoid process and superior nuchal line, thus providing optimal vascularization from the superior thyroid artery/external carotid artery and accessory vasculature from the suprascapular artery. Patients exhibited uneventful postoperative recovery concerning airway and digestive patency. The mean postoperative hospitalization duration was 41 days. The follow-up assessments were negative for postoperative complications. Conclusions: The use of sternocleidomastoid muscle flap was proposed to ensure repair and protection of the suture margin or to constitute a portion, as a scaffold, of the wall by leveraging the muscle’s vascularization and thickness. This technique may be considered a leading component in managing complex situations in tracheal surgery. Full article

Several terminologies exist for a vestigial muscle connecting the clavicle to the cervical vertebrae; however, “levator claviculae muscle” and “cleidocervical muscle” are commonly found in the contemporary literature. The term “levator claviculae” does not determine the location of the superior insertion point, but rather describes a single function of the muscle. However, similar to the sternocleidomastoid muscle, the bilateral presence of this muscle could result not only in increased strength for elevating the clavicle, but also in enhanced neck flexion and greater neck stability. To provide anatomical precision, the muscle could be more accurately termed the cleidocervical muscle. This literature review was performed using “PubMed” as the search engine. Mesh terms such as levator AND claviculae, cleidocervicalis, cleidocervical, cleidoatlanticus, and cleidotrachelian were used. Our proposal for a precise methodology in addressing the terminology would be as follows: [Position 1: cleidocervical muscle] [Position 2: vertebra levels]. In this opinion paper, we advocate for the anatomical community to discontinue the use of the term “levator claviculae” and instead adopt the more appropriate “cleidocervical muscle” in academic discourse. Full article

The aim of this study was to compare the correlation between electromyography (EMG) activity and vehicle motion during double lane change driving. This study measured five vehicle motions: the steering wheel angle, steering wheel torque, lateral acceleration, roll angle, and yaw velocity. The EMG activity for 19 muscles and vehicle motions was applied for envelope detection. There was a significantly high positive correlation between muscles (mean correlation coefficient) for sternocleidomastoid (0.62) and biceps brachii (0.71) and vehicle motions for steering wheel angle, steering wheel torque, lateral acceleration, and yaw velocity, but a negative correlation between the muscles for middle deltoid (−0.75) and triceps brachii long head (−0.78) and these vehicle motions. The ANOVA test was used to analyze statistically significant differences in the main and interaction effects of muscle and vehicle speed. The mean absolute correlation coefficient exhibited an increasing trend with the increasing vehicle speed for the muscles (increasing rate%): upper trapezius (30.5%), pectoralis major sternal (38.7%), serratus anterior (13.3%), and biceps brachii (11.0%). The mean absolute correlation coefficient showed a decreasing trend with increasing vehicle speed for the masseter (−9.6%), sternocleidomastoid (−12.9%), middle deltoid (−5.5%), posterior deltoid (−20.0%), pectoralis major clavicular (−13.4%), and triceps brachii long head (−6.3%). The sternocleidomastoid muscle may decrease with increasing vehicle speed as the neck rotation decreases. As shoulder stabilizers, the upper trapezius, pectoralis major sternal, and serratus anterior muscles are considered to play a primary role in maintaining body balance. This study suggests that the primary muscles reflecting vehicle motions include the sternocleidomastoid, deltoid, upper trapezius, pectoralis major sternal, serratus anterior, biceps, and triceps muscles under real driving conditions. Full article

Background and Objectives: Many risk factors for postoperative C5 palsy (PC5P) have been reported regarding a “cord shift” after a posterior approach. However, there are few reports about shoulder traction as a possible risk factor of anterior cervical surgery. Therefore, we assessed the stretched nerve roots when shoulder traction was applied on cadavers. Materials and Methods: Eight cadavers were employed in this study, available based on age and the presence of foramen stenosis. After dissecting the sternocleidomastoid muscle of the cadaver, the shoulder joint was pulled with a force of 2, 5, 8, 10, 15, and 20 kg. Then, the stretched length of the fifth nerve root was measured in the extra-foraminal zone. In addition, the same measurement was performed after cutting the carotid artery to accurately identify the nerve root’s origin. After an additional dissection was performed so that the superior trunk of the brachial plexus could be seen, the stretched length of the fifth and sixth nerve roots was measured again. Results: Throughout the entire experiment, the fifth nerve root stretched out for an average of 1.94 mm at 8 kg and an average of 5.03 mm at a maximum force of 20 kg. In three experiments, the elongated lengths of the C5 nerve root at 8 kg and 20 kg were 1.69/4.38 mm, 2.13/5.00 mm, and 0.75/5.31 mm, respectively, and in the third experiment, the elongated length of the C6 nerve root was 1.88/5.44 mm. Conclusions: Although this was a cadaveric experiment, it suggests that shoulder traction could be the risk factors for PC5P after anterior cervical surgery. In addition, for patients with foraminal stenosis and central stenosis, the risk would be higher. Therefore, the surgeon should be aware of this, and the patient would need sufficient explanation. Full article