Deltoid Muscle Research Articles

Structural and Functional Alterations of the Deltoid Muscle After Arthroscopic Rotator Cuff Repair: A 2-Year Longitudinal Observation Study.

Deltoid muscle detachment and atrophy have been reported to occur after shoulder surgery. To investigate the 2-year changes in deltoid muscle structure and function after arthroscopic rotator cuff repair (ARCR) using magnetic resonance imaging (MRI) and electrophysical examination. Case series; Level of evidence, 4. A total of 72 patients (72 shoulders) who underwent ARCR between 2015 and 2020 were enrolled. Whole deltoid muscle volume and regional (anterior, lateral, and posterior) muscle thicknesses were determined on T2-weighted MRI scans of both shoulders taken preoperatively and at 1, 3, 6, 12, and 24 months postoperatively, and their correlations with compound muscle action potentials (CMAPs), shoulder abduction muscle strength, and Constant scores were investigated. Comparison between groups was performed using paired or Student t tests, and the relationship between deltoid muscle volume and various factors was determined using Pearson correlation analysis. The volume of the deltoid muscle on the affected side decreased from 44,369 ± 12,371 mm3 preoperatively to 38,139 ± 10,615 mm3 at 1 month postoperatively (P < .05), representing a 14% decrease. The deltoid muscle volume of the contralateral side also significantly decreased during the same time frame, from 43,278 ± 12,248 to 40,273 ± 11,464 mm3 (P < .05), representing a 7% decrease at 1 month postoperatively. Subsequently, the deltoid muscle volume on both sides recovered to preoperative levels at 12 months and was maintained at 24 months. Only the thickness of the anterior part of the deltoid was markedly decreased, from 13.9 ± 3.7 mm preoperatively to 12.0 ± 3.2 mm at 1 month postoperatively (P < .05), representing a 14% reduction. The CMAP amplitude showed a significant decrease at 1 month postoperatively; however, no significant difference was observed after 12 months when compared with the preoperative values or the values on the contralateral side. Positive correlations were found between deltoid muscle volume and CMAP amplitude at 24 months as well as between deltoid muscle volume and shoulder abduction muscle strength (R 2 = 0.698; P < .05) and Constant score (R 2 = 0.133; P < .05). Our study demonstrated that the early structural and functional decline of the deltoid muscle after ARCR was fully recovered within 1 year, confirming that this procedure does not negatively affect the deltoid muscle.

Isolated humeral distalization in reverse total shoulder arthroplasty: a biorobotic shoulder simulator study

BackgroundHumeral distalization is inherent to reverse total shoulder arthroplasty (rTSA) and is often produced with concomitant humeral lateralization via the level of the humeral head cut, implant positioning, implant neck shaft angle, and polymer insert thickness. Biomechanical data on the isolated effects of humeral distalization remain limited but could be important to consider when optimizing postoperative rTSA shoulder function. This study investigated the effects of isolated humeral distalization on shoulder biomechanics using a biorobotic shoulder simulator. MethodsEight fresh-frozen cadaveric shoulders were tested using custom polymer inserts that translated the bearing surface 0, +5, +10, and +15 mm along the humeral stem axis, producing isolated distalization without lateralization. Specimens underwent passive elevation in the scapular plane with a static scapula to assess glenohumeral range of motion. Scapular plane abduction motion trajectories were then performed, driven by previously collected scapulothoracic and glenohumeral kinematics from rTSA patients. The effect of isolated distalization on passive elevation was tested using mixed-effects linear regression and the effect on muscle force, joint reaction force, and muscle excursion during active scapular-plane abduction was tested using statistical parametric mapping random effects analysis. ResultsMaximum passive scapular plane elevation increased with humeral distalization (4° per 5 mm distalization). During active elevation, deltoid and rotator cuff muscle forces, and joint reaction forces, increased up to 37% per 5 mm of distalization. Simulated deltoid muscle excursion was altered with increasing distalization but amounted to no more than 0.8 mm change from baseline per 5 mm of distalization. Rotator cuff muscles were consistently lengthened throughout abduction, up to 1.6 mm per 5 mm of distalization. These trends were observed across various patient motions. ConclusionsIsolated humeral distalization caused dramatic increases in the muscle forces required to perform scapular-plane abduction. Joint reaction forces increased correspondingly. These results suggest that implant and surgical strategies to generate deltoid muscle tension without humeral distalization may promote better active range of motion and more durable long-term outcomes over approaches that rely on distalization.

Ergonomic differences in mesh placement and mesh fixation between laparoscopic and robotic inguinal hernia repair with mesh.

General differences in surgeon ergonomics between laparoscopic and robotic-assisted inguinal hernia repairs (LIHR vs. RIHR) have been previously studied. However, specific differences in the ergonomics of mesh placement (MP) and mesh fixation (MF) are undetermined. Our aim was to determine if there are differences in the ergonomics of MP and MF between the surgical approaches. We hypothesize that we will identify differences, with the potential for worse ergonomics during LIHR. Data was collected from fifteen LIHR and fifteen RIHR. All cases were elective, primary inguinal hernias completed by a fellowship-trained minimally invasive surgeon. Surface electromyography (EMG) of four upper extremity muscle groups, including the upper trapezius (UT), anterior deltoid (AD), flexor carpi radialis (FCR) and extensor digitorum (ED), was recorded bilaterally during MP and MF. Muscle activation as a percent of maximum voluntary contraction (%MVCRMS) and muscle fatigue denoted as the median frequency of muscle activations (Fmed) were calculated for each muscle. EMG analysis showed increased %MVCRMS in LIHR compared to RIHR cases, with significant findings in the left UT, right UT, ED, and FCR for MP and MF and the left FCR during MP. Muscle fatigue was decreased in LIHR compared to RIHR cases, with significant differences in left FCR and right ED and AD. Despite greater muscle activations during LIHR, RIHR had greater muscle fatigue. It is possible that short periods of high muscle activation are ergonomically protective during minimally invasive inguinal hernia repair. Identifying these differences may aid in development of procedure-specific interventions to improve ergonomics.

Increased Postoperative Deltoid Signal seen after Suprapectoral Biceps Tenodesis: Potential Risk to the Anterior Branch of the Axillary Nerve

BackgroundArthroscopic suprapectoral biceps tenodesis is a common procedure for lesions of the long head of the biceps in the setting of anterior shoulder pain. However, the distal portal poses a theoretical risk to the terminal branches of the axillary nerve as the nerve travels from posterior to anterior to innervate the anterior deltoid. The purpose of this retrospective cohort study was to assess for axillary nerve branch injury, identified by deltoid signal change in postoperative magnetic resonance imaging (MRI) in patients who underwent an arthroscopic suprapectoral biceps tenodesis. MethodsPatients who underwent rotator cuff repair with a concomitant arthroscopic suprapectoral biceps tenodesis, had a postoperative MRI, and at least 1 year of follow-up were included. The incidence of increased deltoid signal consistent with injury to an anterior branch of the axillary nerve on proton density fat saturated sequences was collected. Age, sex, body mass index (BMI), and patient reported outcome measures (PROMs) including the American Shoulder and Elbow Surgeons Shoulder Score (ASES) score, Patient-Reported Outcomes Measurement Information System (PROMIS) pain, physical function (PF), and upper extremity (UE) scores, and Single Assessment Numeric Evaluation (SANE) score were compared in patients with and without increased deltoid signal on postoperative MRI. P<0.05 was used for significance. ResultsTwenty-four patients were eligible for inclusion (9 female, average age 59.0±10.1, BMI 27.6±6.7). Edema-like signal within the anterior deltoid musculature was observed in 9 patients on postoperative MRI. Two patients had a second follow-up MRI performed which demonstrated resolution of signal, and one patient required a second surgery for release of adhesions. Patients with increased deltoid signal had higher BMI (p=0.03). There was no difference in any other demographic or postoperative PROM between patients with increased signal and those without at any follow-up time point. No patient demonstrated persistent weakness or numbness in the axillary nerve distribution at final follow-up. DiscussionOver one third of patients in our cohort had MRI evidence of axillary nerve branch injury as seen on proton density fat saturated MRI sequences postoperatively. The distal arthroscopic portal for a suprapectoral biceps tenodesis may place anterior terminal branches of the axillary nerve at risk for injury. Additional investigation and strategies for avoidance of nerve injury in this area should be pursued.

Alternating Muscle Activation Patterns Across The Deltoid Muscles During Sustained Fatiguing Contractions

Alternating Muscle Activation Patterns Across The Deltoid Muscles During Sustained Fatiguing Contractions

Upper limb movement control strategy of top-tier elite male badminton players when smashing for different distances

PurposeMastering the skill of smashing in a game can be quite challenging. Unfortunately, it’s not always easy to control the distance of the smash. The present study investigated the impact of different smashing distances on muscle activation patterns and kinematics of the upper limbs.Material and methodsTen collegiate athletes from a top-ranked team in Korea participated in the present study with a mean age, weight, and height of 21 ± 1 years, 71.9 ± 9.1 kg, and 1.78 ± 2.24 m, respectively. Three valid data points for each subject at three different distances were analyzed using a one-way analysis of variance (ANOVA).ResultsThe results demonstrated that with increasing smashing distance, the internal rotation angle of the elbow and wrist joints decreased, while the angular velocity of flexion and internal rotation of the shoulder, elbow, and wrist joints increased. Muscle activation increased for all muscles except the biceps brachii (BICLO) with increasing distance. The greatest changes in activation levels were observed in the anterior deltoid (DELTA), extensor carpi radialis (ECR), and flexor carpi ulnaris (FCU).ConclusionsDuring tasks with different smashing distances, muscle activation in the upper limbs (except the biceps) increased with increasing distances. Additionally, the internal rotation angle of the upper limbs decreased with increased distances, while the angular velocity of flexion and internal rotation of the shoulder, elbow, and wrist joints increased.

The correlation of muscle morphology with variations of 10-repetition maximum bench press strength in resistance-trained subjects

The relationship between muscle mass and strength is complex as it can be influenced by several neurological factors. Variations in the type of training and its mechanisms involved, such as strength- or hypertrophy-oriented training, may influence this relationship in different ways (Carvalho et al., 2022). In addition, the relationship between muscle stiffness and strength remains unclear (Akagi et al., 2016; Mannarino et al., 2019). Thus, this research aimed to investigate the potential correlation between the strength levels, measured by the 10-repetition maximum (10RM), across different ranges of motion (ROM) in the barbell bench press exercise (BP) to the cross-sectional area (CSA) and shear modulus (= indication for stiffness) of the muscles primarily engaged in the exercise. Twenty-one resistance-trained participants (age 27.1 ± 3.4 years) volunteered in this study. The CSA and muscle shear modulus were assessed in a resting position with ultrasound imaging using an ultrasound system (Supersonic Imaging, Aix-en-Provence, France). CSA ultrasound images were captured with panoramic mode for the pectoralis major and the triceps brachii long head. Muscle shear modulus was measured for the pectoralis major, the anterior deltoid, and the triceps brachii long head using shear wave elastography (SWE). Additionally, participants were assessed for their 10RMs of the three types of BP variations, a full ROM and two partial ROMs, the upper half and lower half of the full movement. Data analyses revealed significant correlations between all BP variations and the medial and lateral CSA of the pectoralis major with correlations ranging from r = 0.775 to r = 0.832 (p = 0.001). Significant correlations were also found for the proximal CSA of the triceps brachii long head with the strength values of all tested BP variations with correlations ranging from ρ = 0.492 to ρ = 0.494 (p = 0.028 to p = 0.027). The distal CSA of the triceps brachii did only correlate significantly with the lower ROM BP (r = 0.484, p = 0.026). No significant correlations were found between the SWE of the measured muscles and the bench press variations tested. Additionally, no differences were observed in the correlations between the BP variations. Correlations between 10RM strength levels and the CSA of the pectoralis, and to a lesser extent, the triceps muscle, show the significance of muscle mass for strength in resistance-trained individuals. This finding aligns with a previous training study that examined the hypertrophic effects of bench press exercises on various muscles (Ogasawara et al., 2012). The study revealed that although both the pectoralis and triceps muscles increased in size, the triceps tended to plateau earlier. This suggests that the pectoralis muscle has a greater capacity for muscle volume growth and, consequently, a higher potential for force production. Finally, SWE measurements revealed no significant correlation with BP variations, implying that muscle stiffness may not play as critical a role in 10RM performance as muscle CSA does. This conclusion aligns with other studies that could not find significant changes in muscle stiffness using SWE following resistance training interventions (Dankel &amp; Razzano, 2020). References Akagi, R., Shikiba, T., Tanaka, J., &amp; Takahashi, H. (2016). A six-week resistance training program does not change shear modulus of the triceps brachii. Journal of Applied Biomechanics, 32(4), 373–378. https://doi.org/10.1123/jab.2015-0290 Carvalho, L., Junior, R. M., Barreira, J., Schoenfeld, B. J., Orazem, J., &amp; Barroso, R. (2022). Muscle hypertrophy and strength gains after resistance training with different volume-matched loads: A systematic review and meta-analysis. Applied Physiology, Nutrition, and Metabolism, 47(4), 357–368. https://doi.org/10.1139/apnm-2021-0515 Dankel, S. J., &amp; Razzano, B. M. (2020). The impact of acute and chronic resistance exercise on muscle stiffness: A systematic review and meta-analysis. Journal of Ultrasound, 23(4), 473–480. https://doi.org/10.1007/s40477-020-00486-3 Mannarino, P., Matta, T. T. D., &amp; Oliveira, L. F. D. (2019). An 8-week resistance training protocol is effective in adapting quadriceps but not patellar tendon shear modulus measured by Shear Wave Elastography. PLoS ONE, 14(4), Article e0205782. https://doi.org/10.1371/journal.pone.0205782 Ogasawara, R., Thiebaud, R. S., Loenneke, J. P., Loftin, M., &amp; Abe, T. (2012). Time course for arm and chest muscle thickness changes following bench press training. Interventional Medicine and Applied Science, 4(4), 217–220. https://doi.org/10.1556/imas.4.2012.4.7

Correlation between Muscular Activity and Vehicle Motion during Double Lane Change Driving.

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.

Analysis of Velocity, Power and Skin Temperature in Paralympic Powerlifting Athletes with Fixed and Variable Resistance.

To analyze the use of currents (VRT) and the traditional method (TRAD) on speed, power and temperature in a training session. Fourteen paralympic powerlifting (PP) athletes took part over three weeks. In week 1, familiarization and 1RM tests took place, and, in weeks 2 and 3, pre- and post-training took place, where the propulsive mean velocity and power and temperatures were assessed before and after, at 24 h and 48 h. There was a difference in the sternal pectoral temperatures before and after VRT (p = 0.040) and at 48 h for TRAD and VRT (p = 0.018); in the clavicular pectoralis before and after VRT and TRAD (p = 0.003); in the anterior deltoid after and at 48 h for TRAD and VRT (p = 0.026 and p = 0.017); and in the triceps after and at 24 h and 48 h between TRAD and VRT (p = 0.005). In the training series, the MPV was significant in TRAD between Set1 and Set5 (p = 0.003), in training (VRT) between Set1 and Set5 (p = 0.001) and in Set5 between the methods (p = 0.047). For power, there was a difference between Set1 and 5 in TRAD (p = 0.016) and VRT (p = 0.002). We conclude that training with currents (VRT) promoted greater muscle fatigue when compared to traditional training.

Free functional gracilis transfer for reconstruction of isolated anterior deltoid atrophy following surgical proximal humerus fixation

BackgroundPalsy of the clavicular head of the deltoid is a complication after surgical fixation of proximal humerus fractures. Flexion of the shoulder joint may be impaired as a result. Additionally, patients may complain of joint instability, visible atrophy and pain. Where nerve reconstruction is not possible, muscle transfers remain as secondary reconstructive procedures. MethodsThree patients suffering from anterior deltoid palsy after proximal humerus fixation received a free functional gracilis transfer to the shoulder. Postoperatively, patients underwent biofeedback-based rehabilitation. Before and after the intervention, subjective complaints, pain level and active range of motion (ROM) were recorded. At the final follow-up patients completed a Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire. ResultsThe surgery was successful in all patients with first muscle signals registered through sEMG approximately four months postoperatively. At the latest follow-up (> 3 years), the patients showed improved shoulder stability and pain scores. In two patients with preoperative restrictions, active ROM improved. The DASH score showed minimal to no disability in two patients and moderate disability in the third. Two patients voiced satisfaction with the restoration of the ventral bulk of the shoulder. ConclusionsThe free functional gracilis muscle transfer is a novel approach for secondary reconstruction in patients with anterior deltoid atrophy who don’t qualify for nerve intervention. It addresses shoulder instability and pain and may improve active ROM. The addition of fresh muscle tissue to the ventral shoulder can improve its natural contour and prevent protrusion of the humeral head.

Investigation of musculoskeletal symptoms, work postures, quantification of muscle activity, and estimation of grip/push forces among sonographers

AbstractDue to the physical nature of their work, sonographers are exposed to many musculoskeletal disorder risk factors, including awkward posture, repetitive movements, forceful manual exertion, and static muscle contractions, especially in the upper limbs. The current study is an investigation of musculoskeletal disorders among sonographers, caused by various occupational risk factors via different sonographic scan types. During the first phase of this study, the musculoskeletal symptoms and work postures of 29 subjects were investigated. During the second phase, muscle activity was quantified, and grip/push forces were estimated using the data obtained from 10 volunteer sonographers. 82% of sonographers experienced musculoskeletal symptoms. Based on the final scores and action levels obtained via rapid upper limb assessment, while performing scans of left regions; ergonomic changes and interventions were found necessary, to relieve stress on the sonographer's body. The results of muscular activity per muscle and scan type, showed that the mean muscle activity of the middle deltoid muscle was significantly higher during the right abdominal scan (17.64% maximum voluntary contraction [MVC]), compared to those of thyroid (12.54% MVC) and left abdominal (7.32% MVC) scans. Additionally, mean grip and push forces during both abdominal scans were significantly higher than those during the thyroid scan. Despite an injury risk during all scans, risk factor impact was different among scan types. This groundbreaking study represents the first that captures and measures both grip and push forces simultaneously, which may prove helpful while investigating corrective interventions or optimizing design of sonography robots and ergonomic probes in future studies.

Effects of victim's body posture and attacker's gender on slashing attacks: a biomechanical study.

Sharp force injury has been and will remain to be a major cause of violent death; however, scientific evaluations on the impact of body posture of the victim and gender of the perpetrator on sharp force injury have been scarce. The purpose of this study was to evaluate the biomechanical characteristics found in individuals (male and female) when using a Chinese kitchen knife to slash the neck of a dummy while it was in the standing and supine positions. This work offers a solid basis for forensic identifications, criminal investigations, and court trials. A total of 12 male and 12 female college students participated in this study. Kinematic, kinetic, and surface electromyography (sEMG) data were evaluated when slashing the neck of a dummy while it was in the standing and supine positions using a Chinese kitchen knife. When slashing the neck of a standing dummy, participants showed shorter contact time (19.5%) and slower shoulder velocities (30.9%) as well as higher hip velocity (26.0%) and increased root mean square (RMS) and integral electromyography (iEMG) for the anterior deltoid (51.3% and 51.2%, respectively) compared to those while the dummy was in the supine position (all p < 0.05), regardless of gender. When slashing a dummy's neck while it was in standing and supine positions, male participants showed higher shoulder, elbow, and wrist velocities (22.6%, 22.7%, and 24.4%, respectively) and higher slashing velocity (19.8%), slashing force (24.2%), and energy (46.2%) than female participants (all p < 0.05). In addition, male participants showed shorter contact time (17.8%), and the values of RMS and iEMG of the anterior deltoid, biceps brachii, extensor carpi radialis longus, and flexor carpi ulnaris were less than those of female participants (98.9%, 47.3%, 65.6%, and 33.4% for RMS and 115.1%, 59.4%, 80.1%, and 47.8% for iEMG, respectively). There was no difference in slashing speed, slashing force, and energy when using a Chinese kitchen knife to slash the dummy's neck while it was in different body postures (standing and supine), suggesting a similar level of injury severity. However, there were significant differences in slashing action patterns between the two body postures, with longer contact time, smaller hip velocity, greater shoulder velocity, and less muscle activation level of the deltoid exertion when slashing the dummy's neck in the supine position. Gender may have a greater effect on the severity of slashing, and the gender difference may be partly related to the body weight difference. The findings from this study may provide quantitative indicators and references for analyzing the motive behind the crime, as well as for case reconstruction, and for the court's conviction and sentencing processes.

Which muscle is the external rotation compensator after superior capsular reconstruction?

BackgroundSuperior capsular reconstruction (SCR) is a surgical option for massive irreparable rotator cuff tears, particularly involving the supraspinatus and infraspinatus. In this procedure, the torn infraspinatus is not repaired or reconstructed. However, an improvement in postoperative external rotation (ER) angle and strength is observed. There is a lack of studies explaining how ER is restored after SCR. The aim of this study is to identify the ER compensator by assessing the muscle volume of the posterior deltoid and teres minor. MethodsSixty-eight patients with massive rotator cuff tears underwent SCR during 2016-2021. Of these patients, 28 who met the following inclusion criteria were retrospectively reviewed: (1) massive rotator cuff tears including the supraspinatus and infraspinatus; (2) severe muscle atrophy and fatty change; (3) intact or reparable subscapularis tendon; (4) Hamada of grade 3 or lower. Posterior deltoid and teres minor volume were measured by using an open-source medical image processing software preoperatively and 1-year postoperatively. The percentage of the posterior deltoid and teres minor muscle volume change was compared between patients with 1-year postoperative ER manual motor testing (MMT) of grade 5 and of grade < 5. The relationship between grade of fatty change, percentage of the muscle volume change, and ER angle and strength were evaluated. ResultsThere was a significant increase in the 1-year postoperative teres minor volume compared with the preoperative volume (24.6±10.3 cm³ versus 20.9±8.3 cm³, p<0.000), while the posterior deltoid volume remained unchanged (178.1±48.3 cm³ versus 178.8±47 cm³). Patients with ER MMT of grade 5 had a greater teres minor volume compared to those with an ER MMT grade of less than 5 (22.3% versus 9.4%), although this difference was not significant (p=0.074, 95% CI=-1.3–27.0). The posterior deltoid volume showed no significant change. The percentage of teres minor volume change had a weak positive correlation with ER strength (r=0.308, p=0.055, 95% CI=-0.02–1.0). There was a significant negative correlation between ER strength and the severity of both preoperative and postoperative fatty changes in the teres minor (r=-0.258, p=0.065, 95% CI=-1.0–-0.042 and r=-0.323, p=0.028, 95% CI=-1.0–-0.113, respectively). The pre- and postoperative fatty changes in the teres minor were negatively correlated with the percentage of teres minor volume change (r=-0.298, p=0.062, 95% CI=-1.0–0.031 and r=-0.413, p=0.015, 95% CI=-1.0–-0.1, respectively). ConclusionThe teres minor may serve as a potential compensator for ER in patients with massive rotator cuff tears following SCR.

Intraoperative Electromyogram Analysis of Postural Musculature With Three-dimensional Screen Display Versus Operating Microscope in Ophthalmic Surgery: A Clinical Methods Study.

To objectively analyze the effect of three-dimensional screen-based surgery (3D SBS) versus traditional operating microscope (TOM) on operating surgeon posterior chain postural musculature during ophthalmic surgery. We hypothesized an increase in median amplitude of electromyography (EMG) signals when using a TOM compared to 3D SBS. The goal was to assess surgical ergonomics that may contribute to cervical and lumbar spine pathology. EMG analysis was conducted at the University of Cincinnati Medical Center Epilepsy Monitoring Unit. Data were collected in the private practice setting at Cincinnati Eye Institute. This was an institutional review board exempt, nonrandomized, prospective, single center, n = 1 clinical methods study. EMG surface electrodes were affixed to the bilateral splenius capitis, sternocleidomastoid, upper trapezius, anterior deltoid, and quadratus lumborum musculature. EMG data were collected across four sessions consisting of one day each using 3D SBS or a TOM, and two cross-over days. A survey regarding surgeon comfort was administered before, during, and after each surgery, and at the end of each day. EMG cross-over data demonstrated an increase in muscle activation in all measured muscles except the anterior deltoids and right quadratus lumborum with use of a TOM. Survey data showed increased fatigue when using a TOM relative to 3D SBS. EMG demonstrated increased postural muscle activation when utilizing TOM relative to 3D SBS. Similar to previous studies, our survey data suggest inferior ergonomics of TOM relative to 3D SBS. [Ophthalmic Surg Lasers Imaging Retina 2024;55:628-636.].

Utility of the Repetitive Nerve Stimulation Test and Needle EMG in the Trapezius Muscle for the Early Diagnosis of ALS.

To document the utility of decremental responses in the repetitive nerve stimulation test (RNS) and spontaneous activities in needle electromyography (EMG) in the trapezius muscle for the diagnosis of amyotrophic lateral sclerosis. Subjects were retrospectively identified from our EMG database. Cervical spondylosis was represented as a disease control group. We investigated the sensitivity and specificity of RNS and EMG in the trapezius muscle and those of diagnostic criteria including the Gold Coast criteria (GCC). We reviewed 120 patients with amyotrophic lateral sclerosis and 17 patients with cervical spondylosis. "RNS or EMG" achieved the highest sensitivity (85%). The specificity was the highest for RNS (94%). Addition of RNS of the deltoid muscle achieved 98% sensitivity in the upper-limb onset amyotrophic lateral sclerosis. The sensitivity of the GCC was very high (88%). Neurophysiological parameters investigated in this study having close to 100% specificities or sensitivities are useful as complements to the GCC.

Insights into the Medial Pectoral Nerve Transfer for Shoulder Abduction in Brachial Plexus Injuries: A Retrospective Case Series Analysis

Treatment priority in C5, C6, and C7 brachial plexus root avulsion is the recovery of shoulder function through reinnervation of shoulder muscles. The medial pectoral nerve is a potential donor for axillary nerve transfer, but outcomes are sparsely reported. This study reports the results of medial pectoral nerve transfer to the axillary nerve. We conducted a retrospective analysis of 12 patients with traumatic brachial plexus injury (C5, C6, and C7 root avulsion) who underwent medial pectoral nerve transfer to the axillary nerve. Sociodemographic and clinical characteristics, including electromyography findings, were documented. We assessed postoperative shoulder abduction strength and range of motion. Statistical analyses compared presurgery and postsurgery outcomes and contrasted our results with those from a study using spinal accessory nerve transfer to the suprascapular nerve. Postsurgery, the mean shoulder abduction range of motion was 65.45°, with a median strength of M2. Significant improvement was noted compared to preoperative values. However, outcomes did not significantly surpass those from spinal accessory nerve transfer. Electromyography showed a low incidence of motor unit action potentials in the deltoid. Medial pectoral nerve transfer to the axillary nerve did not yield superior results in shoulder abduction and deltoid reinnervation in our group of patients. At present, different nerve donors may also need to be considered for deltoid muscle reinnervation in patients with C5, C6, and C7 root avulsion to achieve better shoulder abduction recovery.

Comparing Access to Engaging Hill-Sachs Lesions Between the Modified Posterior Deltoid Split Approach and Standard Deltopectoral Approach for Bone Grafting.

Hill-Sachs lesions are common after shoulder instability, and treatment options vary but include remplissage or implantation of structural bone graft. Large Hill-Sachs lesions not addressed by remplissage are challenging to manage and may frequently require an open surgical approach for bone filling treatment options. The optimal approach to maximize visualization of the humeral head during these procedures remains unclear. The purpose of this study was to compare the area of the humeral head accessed using a modified posterior deltoid split approach versus a standard deltopectoral approach without surgical dislocation, with particular attention to access of engaging Hill-Sachs lesions for the purpose of bone grafting in the setting of anterior shoulder instability. It was hypothesized that both approaches would provide equal access to a simulated Hill-Sachs lesion. Controlled laboratory study. Four human cadaveric shoulders were mounted in the beach-chair position. The modified posterior deltoid split approach and nonextensile deltopectoral approaches were performed. A typical Hill-Sachs lesion was simulated on the humeri. The percentage of the total surface area of the humeral head that was accessed, including access to the simulated Hill-Sachs lesion, was mapped using 3-dimensional digitizing software. The deltopectoral approach provided 45% ± 15.2% access (range, 24% to 58%) to the humeral head versus 22.2% ± 6.1% (range, 17% to 30%) for the modified posterior deltoid split approach (P = .057). The modified posterior deltoid split approach enabled 100% access of the simulated Hill-Sachs lesion compared with 0% for the nonextensile deltopectoral approach. The angle of access to the articular surface was direct and perpendicular with the modified posterior deltoid split approach. The overall surface area of the humeral head accessed via the modified posterior deltoid split approach was less compared with the deltopectoral approach; however, the entire area of a typical Hill-Sachs lesion was able to be accessed from the modified posterior deltoid split approach, whereas this area was not well visualized from the standard deltopectoral approach. The modified posterior deltoid split approach provided sufficient access to the humeral head for the purposes of grafting an engaging Hill-Sachs lesion in the setting of anterior shoulder instability.

Analysis of Muscles Electrical Activities During Bench Press

The primary objective of the study was to compare the muscle electrical activity during Benchpress for the different muscle groups. The amount of contribution of each mentioned muscle duringbench press was also analyzed.For the purpose of the present investigation, total of 10 male power lifterswere chosen as the sample forthe study.The analysis showed that there is a significant difference in the muscle electrical activity during Benchpress for the different muscle groups. The results pertaining to EMG data of 1RM bench pressrevealed maximum muscle electrical activity in case of Pectoralis Major. Hence the Pectoralis Majordisplayed better muscle electrical activity than the Anterior deltoid and Triceps

Comparative analysis of biomechanical characteristics between the new Tai Chi elastic band exercise for opening and closing movement and elastic band resistance training for the reverse fly movement.

The objective of this study was to compare and analyze the representative opening and closing movement of Tai Chi elastic band exercise with the reverse fly movement of elastic band resistance training. The aim was to explore the biomechanical differences between the two exercises and provide theoretical support for the application of Tai Chi elastic band exercise in health intervention. A total of 26 male participants were recruited and randomly divided into two groups in a 1:1 ratio. There were 13 participants in each Tai Chi elastic band exercise group and elastic band resistance training group. Both groups of participants used an elastic band to perform movement in the experiment. Experimental data were collected using the Vicon infrared motion capture system and Delsys surface EMG system. The AnyBody software was utilized to simulate the creation of a musculoskeletal model for both exercises. The study found that the Tai Chi elastic band exercise group exhibited smaller horizontal abduction angle and flexion angle of the shoulder joint, as well as normalized RMS of the anterior deltoid and triceps brachii, compared to the elastic band resistance training group (P < 0.01); the Tai Chi elastic band exercise group exhibited greater elbow flexion angle, elbow flexion torque, and muscle strength of the infraspinatus, coracobrachialis, biceps brachii, brachialis and brachioradialis, compared to the elastic band resistance training group (P < 0.01); the Tai Chi elastic band exercise group exhibited smaller horizontal abduction angular velocity of the shoulder joint and a lower normalized RMS of the posterior deltoid, compared to the elastic band resistance training group (P < 0.05). (1) The opening and closing movement of Tai Chi elastic band exercise is characterized by a large elbow flexion angle, a small shoulder joint horizontal angle and flexion angle, and a slow and uniform speed of movement. The reverse fly movement of elastic band resistance training is characterized by a large horizontal abduction angle of the shoulder joint, a large flexion angle of the shoulder joint, a small flexion angle of the elbow joint, and a fast and uneven speed. (2) The opening and closing movement exerts a greater torque on the elbow flexion, while the reverse fly movement exerts a greater torque on the shoulder joint horizontal abduction and external rotation. (3) The opening and closing movement provide greater stimulation to the infraspinatus, coracobrachialis, and elbow flexor, while the reverse fly movement provides greater stimulation to the posterior deltoid, anterior deltoid, subscapularis, and elbow extensor. In summary, the variation in joint angle, joint angular velocity, and hand position could be the factor contributing to the differences in joint torque and muscle activity between the opening and closing movement of Tai Chi elastic band exercise and the reverse fly movement of elastic band resistance training.

Activation patterns of rotator-cuff muscles from quantitative IVIM DWI after physical testing

BackgroundThe diagnostic value of clinical rotator cuff (RC) tests is controversial, with only sparse evidence available about their anatomical specificity. We prospectively assessed regional RC muscle activation patterns by means of intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (MRI) after the execution of common clinical RC tests.MethodsTen healthy subjects (five males, five females) underwent three sessions of diffusion-weighted 3-T shoulder MRI before and after testing the supraspinatus (SSP, Jobe test, session 1), subscapularis (SSC, lift-off test, session 2, at least 1 week later), and infraspinatus muscle (ISP, external rotation test, session 3, another week later). IVIM parameters (perfusion fraction, f; pseudo-diffusion coefficient. D*; and their product, fD*) were measured in regions of interest placed in images of the SSP, SSC, ISP, and deltoid muscle. The Wilcoxon signed-rank test was used for group comparisons; p-values were adjusted using the Bonferroni correction.ResultsAfter all tests, fD* was significantly increased in the respective target muscles (SSP, SSC, or ISP; p ≤ 0.001). After SSP testing, an additional significant increase of fD* was observed in the deltoid, the SSC, and the ISP muscle (p < 0.001). After the SSC and ISP tests, no significant concomitant increase of any parameter was observed in the other RC muscles.ConclusionIVIM revealed varying activation patterns of RC muscles for different clinical RC tests. For SSP testing, coactivation of the deltoid and other RC muscles was observed, implying limited anatomical specificity, while the tests for the SSC and ISP specifically activated their respective target muscle.Relevance statementFollowing clinical RC tests, IVIM MRI revealed that SSP testing led to shoulder muscle coactivation, while the SSC and ISP tests specifically activated the target muscles.Key PointsIn this study, intravoxel incoherent motion MRI depicted muscle activation following clinical rotator cuff tests.After supraspinatus testing, coactivation of surrounding shoulder girdle muscles was observed.Subscapularis and infraspinatus tests exhibited isolated activation of their respective target muscles.Graphical