Novel Muscle in Infraspinous Fossa

The infraspinatus muscle (IS) makes a minor contribution to lateral rotation of the arm but mainly serves to stabilize the glenohumeral (GH) joint as part of the rotator cuff. Although reports of variations in the rotator cuff muscles have been documented previously, specific discussions of IS variants are lacking. In this report, we present a novel case of an accessory muscle in the infraspinous fossa and its relationship to the IS, which was normally located. We describe the observed physical features of the muscles and their innervation patterns.

COVID-19 Vaccines and Axillary Nerve Dysfunction: A Case Report

COVID-19 resulted in a worldwide pandemic and the rapid introduction of vaccines in an attempt to mitigate it. Neuritis and neuropathy after intramuscular injection had been previously seen with influenza vaccines and appear to be a side effect of the COVID-19 vaccine as well. In the following report, we present the case of a 43-year-old female who developed axillary nerve symptoms after administration of the COVID-19 vaccine and her subsequent recovery.

Investigation of Deltoid Muscle Activation From Different Angles in Body Building Athletes

Objectives

It is known that bodybuilders suffer from shoulder injuries frequently. Therefore, it is important to determine the most appropriate form of movement during shoulder exercises. For this reason, this study was carried out to determine the most accurate form of movement by examining the deltoid muscle activation of bodybuilders from different angles.

Methods

The survey model, one of the quantitative research techniques, was used in this study. 53 athletes (44 men, 9 women) with an age of 25.77±9.13 years, height of 177.07±8.40 cm, body weight of 78.06±14.16 kg, and body mass index of 24.78±3.43 kg/m2 who regularly attended bodybuilding gyms were included in the study. The deltoid activations of the participants was measured, while the glenohumeral joint is at 90°, the cubital joint is in abduction at 180°, 150° and 120°. surface electromyography (sEMG) biofeedback was determined using the Neurotrac Myoplus Pro device. Joint angles were determined with a goniometer. Statistical analyses of the study were performed using the SPSS 25 package program. It was found that the data were normally distributed and the Repeated measures Anova test was applied for comparisons.

Results

As a result of statistical analysis, in male participants, mean deltoid sEMG values and maximum voluntary contraction (MVC [%]) significantly decreased with decreasing angle size (p<0.05). In female participants, the average sEMG and MVC (%) values did not change at different angles (p>0.05).

Conclusion

According to the research results, shoulder sEMG activations decrease in direct proportion to the angle in bodybuilders. When the glenohumeral joint is 90° and the cubital joint is 180°, the activation of the medial deltoid muscle is highest. It is suggested that bodybuilders should consider the results of our study when performing exercises to hypertrophy the deltoid muscle.

Influence of Vitamin D Deficiency on the Expression of Genes and Proteins in Patients With Medium Rotator Cuff Tears

BACKGROUND

Whether vitamin D deficiency is related to rotator cuff muscle and tendon physiology is controversial.

PURPOSE

To assess the relationship between vitamin D deficiency and various gene expression patterns in patients with rotator cuff tears.

STUDY DESIGN

Controlled laboratory study.

METHODS

During arthroscopic surgery, samples from the supraspinatus muscle, deltoid muscle, and supraspinatus tendon were acquired from 12 patients with vitamin D deficiency (serum 25-hydroxyvitamin D concentration <20 ng/dL) and 12 patients with sufficient vitamin D levels (control group, serum 25-hydroxyvitamin D concentration ≥30 ng/dL) who were matched for age, sex, and tear size. Alterations in the expression of genes and proteins associated with myogenesis, muscle atrophy, adipogenesis, inflammation, and apoptosis, as well as in vitamin D receptor expression, were assessed using quantitative reverse transcription polymerase chain reaction, Western blotting, and immunohistochemistry and were compared between the 2 groups.

RESULTS

Vitamin D receptor gene expression in the deltoid muscle was significantly lower in the vitamin D deficiency group than in the control group (P = .043). Additionally, in the deltoid muscle, myoDgene expression levels were lower and atrogin levels were higher in the vitamin D deficiency group than in the control group (P = .034 and P = .011, respectively). However, in the supraspinatus muscle, no differences were observed between groups in the expression of myogenesis- or atrophy-related genes (all P > .05). The expression of inflammation-related genes (interleukin (IL)-1β and IL-6) was significantly higher in the vitamin D deficiency group, in both the deltoid and supraspinatus muscles (all P < .05). The supraspinatus tendon tissue did not show any significant differences in any gene expression evaluated (all P > .05). A correlation between gene and protein expression was observed for atrogin and IL-1β in the deltoid muscle (P = .019 and P = .037, respectively) and for IL-6 in the supraspinatus muscle (P = .044).

CONCLUSION

Vitamin D deficiency was not associated with the expression of myogenesis-related or muscle atrophy-related genes in the supraspinatus muscle of patients with rotator cuff tears, unlike in the deltoid muscle; rather, vitamin D deficiency was associated with increased proinflammatory cytokine expression.

CLINICAL RELEVANCE

In patients with rotator cuff tears, vitamin D deficiency was observed to be associated with increased levels of proinflammatory cytokines in the rotator cuff muscles, without significant changes in gene expression related to myogenesis or muscle atrophy.

[Effect of critical shoulder angle on deltoid muscle strength reduction in patients with rotator cuff tears]

Objective

To investigate the synergistic interaction between the deltoid muscle and the rotator cuff muscle group in patients with rotator cuff tears (RCT), as well as the impact of the critical shoulder angle (CSA) on deltoid muscle strength.

Methods

A retrospective analysis was conducted on clinical data from 42 RCT patients who met the selection criteria and were treated between March 2022 and March 2023. There were 13 males and 29 females, with an age range of 42-77 years (mean, 60.5 years). Preoperative visual analogue scale (VAS) score was 6.0±1.6. CSA measurements were obtained from standard anteroposterior X-ray films before operation, and patients were divided into two groups based on CSA measurements: CSA>35° group (group A) and CSA≤35° group (group B). Handheld dynamometry was used to measure the muscle strength of various muscle group in the shoulder (including the supraspinatus, infraspinatus, subscapularis, and anterior, middle, and posterior bundles of the deltoid). The muscle strength of the unaffected side was compared to the affected side, and muscle imbalance indices were calculated. Muscle imbalance indices between male and female patients, dominant and non-dominant sides, and groups A and B were compared. Pearson correlation analysis was used to examine the relationship between muscle imbalance indices and CSA as well as VAS scores.

Results

Muscle strength in all muscle groups on the affected side was significantly lower than on the unaffected side ( P<0.05). The muscle imbalance indices for the supraspinatus, subscapularis, infraspinatus, and anterior, middle, and posterior bundles of the deltoid were 14.8%±24.4%, 5.9%±9.7%, 7.2% (0, 9.1%), 17.2% (5.9%, 26.9%), 8.3%±21.3%, and 10.2% (2.8%, 15.4%), respectively. The muscle imbalance indices of the anterior bundle of the deltoid, supraspinatus, and infraspinatus were significantly lower in male patients compared to female patients ( P<0.05); however, there was no significant difference in muscle imbalance indices among other muscle groups between male and female patients or between the dominant and non-dominant sides ( P>0.05). There was a positive correlation between the muscle imbalance indices of infraspinatus and VAS score ( P<0.05), and a positive correlation between CSA and the muscle imbalance indices of middle bundle of deltoid ( P<0.05). There was no correlation between the muscle imbalance indices of other muscle groups and VAS score or CSA ( P>0.05). Preoperative CSA ranged from 17.6° to 39.4°, with a mean of 31.1°. There were 9 cases in group A and 33 cases in group B. The muscle imbalance indices of the anterior bundle of the deltoid was significantly lower in group A compared to group B ( P<0.05), while there was no significant difference in muscle imbalance indices among other muscle groups between group A and group B ( P>0.05).

Conclusion

Patients with RCT have a phenomenon of deltoid muscle strength reduction, which is more pronounced in the population with a larger CSA.

Accessory part of the deltoid muscle

The shoulder and arm region has numerous morphological variations. The deltoid muscle usually consists of three parts: anterior, middle and posterior. This case report describes a very rare deltoid muscle variant, an addition to the spinal part that is attached proximally at the infraspinatus fascia and the spine of the scapula. The distal attachment transforms directly into the brachialis muscle. Additional parts can affect the biomechanics and function of the joints significantly.

Anterior deltoid muscle reflection using a deltopectoral approach is safe and does not influence outcome of reverse shoulder arthroplasty

BACKGROUND

The deltopectoral approach is well accepted for shoulder arthroplasty procedures. The extended deltopectoral approach with detachment of the anterior deltoid from the clavicle allows increased joint exposure and can protect the anterior deltoid from traction injury. The efficacy of this extended approach has been demonstrated in anatomical total shoulder replacement surgery. However, this has not been shown in reverse shoulder arthroplasty (RSA). The primary aim of this study was to evaluate the safety of the extended deltopectoral approach in RSA. The secondary aim was to evaluate the performance of the deltoid reflection approach in terms of complications, surgical, functional and radiological outcomes up to 24 months post-surgery.

METHODS

A prospective non-randomized comparative study was performed between January 2012 and October 2020 including 77 patients in the deltoid reflection group and 73 patients in the comparative group. Decision for inclusion was based on patient and surgeon factors. Complications were recorded. Patients were followed up for at least 24 months to evaluate their shoulder function and ultrasound evaluation. Functional outcome measures included the Oxford Shoulder Score (OSS), Disabilities of the Arm, Shoulder and Hand (DASH) score, American Shoulder Elbow Surgeons score (ASES), pain intensity (VAS 0-100), range of motion (forward flexion (FF), abduction (AD), and external rotation (ER)). A regression analysis was performed to evaluate any factors of influence on the VAS.

RESULTS

There were no significant differences in the rate of complications between the two groups (14.5% in the deltoid reflection group and 13.8% in the comparative group, p=0.915). Ultrasound evaluation was available in 64 (83.1%) patients, and no proximal detachment was observed. In addition, there were no significant differences in functional outcome measures both preoperatively and at 24 months post-surgery between the groups on Mean VAS pain, OSS, DASH, ASES, FF, ABD, and ER. Adjustment for possible confounders in a regression model indicated that only prior surgery significantly influenced the VAS pain (p=0.031, 95%CI 0.574 - 11.67) after surgery. Deltoid reflection (p=0.068), age (p=0.466), sex (p=0.936), glenoid graft (p=0.091), prosthesis manufacturer (p=0.382) and preop VAS score (p=0.362) were not of influence.

DISCUSSION

Results of this study show an extended deltopectoral approach for RSA is safe. Selected reflection of the anterior deltoid muscle improved exposure and prevents anterior deltoid muscle injury followed by re-attachment. Patients had similar functional scores preop and at 24 months compared to a comparative group. Furthermore, ultrasound evaluation showed intact re-attachments.

Defining postoperative C5 palsy and recovery: a systematic review

OBJECTIVE

Postoperative C5 palsy (C5P) is a well-recognized and often-delayed complication of cervical spine surgery. Most patients recover within 6 months of onset, but the prognosis of severe cases is poor. The clinical significance and natural history of mild versus severe C5P appear to differ substantially, but palsy severity and recovery have been poorly characterized in the literature.

METHODS

Owing to the varying prognoses and expanding treatment options such as nerve transfer surgery to reconstruct the C5 myotome, this systematic review attempted to describe how C5P severity is classified and how C5P and its recovery are defined, with the aim of proposing a postoperative C5P scale to support clinical decision-making. PubMed was searched for articles in English published since 2000 that offer a clear definition of postoperative C5P or its recovery. Only articles reporting exclusively on C5 palsy for patients undergoing surgery for degenerative disease were included. A single reviewer screened titles and abstracts and reviewed the full text of relevant articles, with consultation as needed from a second reviewer. Data collected included postoperative C5P definitions, classification of C5P severity, and definition and/or classification of C5P recovery. Qualitative analysis was performed.

RESULTS

Full-text reviews were conducted of 98 of 272 articles identified and screened, and 43 met the inclusion criteria. Postoperative C5P was most commonly defined as a reduction in deltoid muscle strength by ≥ 1 grade using manual muscle testing (MMT), with potential biceps involvement also noted by some studies. The few studies that stratified C5P on the basis of severity unanimously characterized severe C5P as MMT grade ≤ 2. Nine studies reported on C5P recovery. Deltoid muscle strength improvement of MMT grade 5 commonly defined complete recovery, with no MMT improvement considered partial recovery.

CONCLUSIONS

This review identified clear discrepancies in the definitions of C5P and its recovery, leading to heterogeneity in its evaluation and management. With the emergence of therapeutic procedures for severe C5P, standardization of the definitions of C5P and its recovery is critical. The authors propose MMT grades of 4, 3, and ≤ 2 to classify C5P as mild, moderate, and severe, respectively, and grades of 5, 4, and 3 to classify recovery as complete, sufficient, and useful, respectively.

Anatomical and molecular analyses of the deltoid muscle in chimpanzees (Pan troglodytes) and modern humans (Homo sapiens): Similarities and differences due to the uses of the upper extremity

In the deltoid muscles of Pan troglodytes and Homo sapiens, we have analyzed the muscle architecture and the expression of the myosin heavy chain (MHC) isoforms. Our aim was to identify differences between the two species that could be related to their different uses of the upper limb. The deltoid muscle of six adult Pan troglodytes and six adult Homo sapiens were dissected. The muscle fascicle length (MFL) and the physiological cross-sectional area (PCSA) of each muscle were calculated in absolute and normalized values. The expression pattern of the MHC-I, MHC-IIa and MHC-IIx isoforms was analyzed in the same muscles by real-time polymerase chain reaction. Only the acromial deltoid (AD) presented significant architectural differences between the two species, with higher MFL values in humans and higher PCSA values in chimpanzees. No significant differences in the expression pattern of the MHC isoforms were identified. The higher PCSA values in the AD of Pan troglodytes indicate a greater capacity of force generation in chimpanzees than in humans, which may be related to a greater use of the upper limb in locomotion, specifically in arboreal locomotion like vertical climbing. The functional differences between chimpanzees and humans in the deltoid muscle are more related to muscle architecture than to a differential expression of MHC isoforms.

111In-Pentetreotide Uptake Due to COVID-19 Vaccination

ABSTRACT

A 72-year-old woman was referred for whole-body 111In-pentetreotide scintigraphy with SPECT/CT. There was increased uptake of lymphadenopathy in the left axilla and left deltoid muscle. The patient's history revealed that the patient received the first dose of the COVID-19 vaccine 3 days before the 111In-pentetreotide scintigraphy with SPECT/CT. This case demonstrates that the COVID-19 vaccine can cause 111In-pentetreotide uptake in the lymph nodes and the deltoid muscle.

Efficacy and safety of botulinum toxin injection in reducing deltoid muscle hypertrophy

With the increasing demand for body contouring, botulinum toxin (BTX) injection is being widely used off-label for muscular hypertrophy. However, to the best of our knowledge, no study has investigated the clinical efficacy of BTX type A (BTX-A) in deltoid muscle hypertrophy. This study was conducted to evaluate the efficacy and safety of intramuscular injection of BTX in reducing deltoid muscle hypertrophy. Overall, 10 patients with bilateral deltoid muscle hypertrophy were treated with an intramuscular injection of prabotulinum toxin A, with a total of 50 units [U] administered per patient. As measured by ultrasonography, the thickness of the deltoid muscles was significantly decreased at weeks 2 and 12. In addition, the clinical assessment score by blinded investigators was improved after the treatment; however, patients' satisfaction scores were relatively low. No major complications were reported. Therefore, intramuscular injection of BTX-A seems to be a candidate for novel treatment option for deltoid muscle hypertrophy. Further larger clinical studies are warranted to confirm the efficacy of BTX-A.

Morphology of the Undersurface of the Anterolateral Acromion and Its Relationship to Surrounding Structures

Background:

A better understanding of the morphology underneath the acromion is needed to prevent complications after arthroscopic subacromial decompression. The precise correlations between the morphologic features underneath the acromion and the surrounding structures including the attachment of the coracoacromial ligament (CAL) and the origin of the deltoid middle head have not yet been determined in the absence of artifacts on the bony surface caused by dissection techniques. Moreover, anatomic findings in previous studies using only older-aged cadavers or dried bones may not reflect the morphologic features of younger and healthy specimens.

Purpose:

To characterize the anterolateral structures morphologically in the inferior aspect of the acromion, assess the relationships of these structures with surrounding structures without dissection artifacts on the bony surface, and verify the cadaveric data in the asymptomatic shoulders of living middle-aged patients.

Study Design:

Descriptive laboratory study.

Methods:

We initially analyzed the relationship between the morphology of the anterolateral structures and surrounding structures in 18 cadaveric shoulders (mean age, 81.8 years), 15 of which were subjected to macroscopic investigation of the CAL attachment and 3-dimensional micro—computed tomography investigation with radiopaque markers and 3 of which were subjected to histologic examination. We also analyzed the morphology underneath the anterolateral acromion in 24 asymptomatic shoulders of middle-aged patients (mean age, 54.8 years) to verify the cadaveric data. In both the cadaveric shoulders and the asymptomatic shoulders of live patients, the long axis, width, and height of the anterolateral prominence were measured by use of 3-dimensional CT imaging.

Results:

In cadavers, the anterolateral prominence underneath the acromion corresponded to the attachment of the CAL. Histologic evaluation revealed that the CAL was continuous to the deep layer of the deltoid middle head in the lateral acromion. The study in asymptomatic shoulders of middle-aged patients revealed bony prominences similar to those observed in cadavers.

Conclusion:

The anterolateral prominence, which corresponds to the attachment of the CAL below the acromion, may be a native structure below the acromion. Moreover, the CAL is continuous to the deep layer of the deltoid middle head in the lateral acromion.

Different Shoulder Exercises Affect the Activation of Deltoid Portions in Resistance-Trained Individuals

The aims of this study were to compare muscle activity of the anterior deltoid, medial deltoid, and posterior deltoid in the bench press, dumbbell fly, shoulder press, and lateral raise exercises. Thirteen men experienced in strength training volunteered for the study. Muscle activation was recorded during maximum isometric voluntary contraction (MVIC) for data normalization, and during one set of 12 repetitions with the load of 60% 1RM in all exercises proposed. One-way repeated-measures ANOVA with Bonferroni’s posthoc was applied using a 5% significance level. For anterior deltoid, the shoulder press (33.3% MVIC) presented a significantly higher level of activation when compared to other exercises. Also, no significant difference was found between the bench press (21.4% MVIC), lateral raise (21.2% MVIC), and dumbbell fly (18.8% MVIC). For the medial deltoid, the lateral raise (30.3% MVIC) and shoulder press (27.9% MVIC) presented a significantly higher level of activity than the bench press (5% MVIC) and dumbbell fly (3.4% MVIC). Besides, no significant difference was found between the bench press and the dumbbell fly. For the posterior deltoid, the lateral raise (24% MVIC) presented a significantly higher level of activation when compared to other exercises. For the posterior deltoid portion, the shoulder press (11.4% MVIC) was significantly more active than the bench press (3.5% MVIC) and dumbbell fly (2.5% MVIC). Moreover, no significant difference was found between the bench press and the dumbbell fly. In conclusion, the shoulder press and lateral raise exercises showed a higher level of muscle activation in the anterior deltoid and medial deltoid when compared to the bench press and dumbbell fly exercises.

Functional evaluation following deltoid muscle resection in patients with soft tissue sarcoma

BACKGROUND

The present study aimed to determine functional outcomes in patients undergoing deltoid muscle resection for soft tissue sarcoma.

METHODS

Between 2002 and 2014, 18 patients with soft tissue sarcoma of the shoulder who underwent wide resection including the deltoid muscle, and were followed up for more than 12 months, were retrospectively included in the study. In all, 11 patients were male and 7 were female. The median age was 59 years, median follow-up duration was 37 months. The extent of resection of deltoid muscle, with or without rotator cuff damage, reconstruction methods, adjuvant therapy, oncological outcomes, and the International Society of Limb Salvage (ISOLS) score as functional outcomes were analyzed.

RESULTS

Six patients underwent total resection, and twelve underwent partial resections of deltoid muscle. The rotator cuff was resected in four patients. Soft tissue reconstruction was performed in 17 patients using a pedicled latissimus dorsi muscle flap. Two local recurrences and three distant metastases occurred during follow-up. Median overall survival was 72 months. The mean ISOLS score was 25.0 points (±4.6points). Univariate analysis revealed that there was no significant difference in ISOLS score regarding the extent of deltoid muscle resection. Multivariate analysis identified only combined resection of the rotator cuff as a significant prognostic factor for poor functional outcomes (P < 0.001).

CONCLUSIONS

The extent of resection of the deltoid muscle might not affect the functional outcomes determined by ISOLS score. If the rotator cuff is resected concurrently, satisfactory functional outcomes might not be obtained.

The effects of ball impact position on shoulder muscle activation during spiking in male volleyball players

Background

The ball impact position during spiking in volleyball may influence the pattern of activation of shoulder girdle muscles and, therefore, could be a significant risk factor for shoulder injury.

Methods

Activation of 10 muscles in the dominant shoulder was evaluated using surface electromyography (EMG) in 11 male volleyball players, during spiking in a static standing position, with the goal being to precisely control the specified ball impact positions, without a run-up or ball setting. The following 4 ball impact positions were evaluated: standard, posterior, medial, and lateral. The EMG amplitude, normalized to the maximal voluntary isometric contraction of the respective muscles, was compared for each phase of the spiking movement between the standard position and the other 3 different impact positions, using the Dunnett test.

Results

The following between-position differences were noted for the deltoid muscle: increased activation of the anterior deltoid during the acceleration phase for the posterior position (P = .041), increase in the posterior deltoid during the acceleration phase for the lateral position (P = .04), and increase in the middle deltoid during the deceleration phase for the lateral position (P = .005).

Conclusion

A posterior or lateral shift in the position of ball impact may cause an increase in the activity of the deltoid muscle that would cause a decrease in the centripetal force of the humeral head through the acceleration and deceleration phases. As such, neuromuscular exercises, combined with strengthening of the rotator cuff muscle, might reduce the risk of shoulder injury during performance of the volleyball spiking movement.

Shoulder Muscle Strength and Neuromuscular Activation 2 Years after Reverse Shoulder Prosthesis-An Experimental Case Control Study

Although reverse shoulder arthroplasty (RSA) has shown successful postoperative outcomes, little is known about compensatory activation patterns of remaining shoulder muscles following RSA. The purpose of this experimental case control series was to investigate shoulder muscle strength and neuromuscular activation of deltoid and teres minor muscles 2 years after RSA. Humerus lengthening, center-of-rotation medialization, maximal voluntary strength, and electromyographic (EMG) activity were compared between the operated and the non-operated side of 13 patients (mean age: 73 years). Shoulder muscle strength was significantly lower on the operated side for external rotation (−54%), internal rotation (−20%), and adduction (−13%). Agonist deltoid EMG activity was lower on the operated side for shoulder flexion, extension, and internal and external rotation (p < 0.05). Antagonist deltoid coactivation was higher on the operated side for external rotation (p < 0.001). Large correlation coefficients were observed between shoulder adductor strength asymmetry and both center-of-rotation medialization (r = −0.73) and humerus lengthening (r = 0.71). Shoulder abduction strength and neuromuscular activation were well preserved 2 years after RSA, while persistent strength and activation deficits were observed for shoulder adduction and internal and external rotation. Additional studies are required to elucidate shoulder neuromuscular activation patterns before and after RSA to support decision making for surgical, implant design, and rehabilitation choices.

Intramuscular myxoma of the deltoid muscle in a swimmer: A rare case report and literature review

Intramuscular myxoma (IM) is a rare mesenchymal neoplasm with the incidence of one per 1 000 000 people and is reported greater among women. Our case reports an IM of a deltoid muscle in a young man. Differential diagnosis with sarcoma is important. Surgery is the treatment of choice usually without recurrence.

Posterior and inferior glenosphere position in reverse total shoulder arthroplasty supports deltoid efficiency for shoulder flexion and elevation

BACKGROUND

For humeral flexion and elevation, most relevant for daily activities with reverse total shoulder arthroplasty, the anterior and lateral deltoid muscles are most important. However, how this direction of movement is best supported with the glenosphere position is not fully understood. We hypothesized that both inferior positioning and posterior positioning of the glenosphere may best support this direction of movement.

METHODS

A validated, anatomic biomechanical shoulder model was modified to host a reverse shoulder prosthesis. The glenoid baseplate was altered to allow inferior, lateral, and posterior center-of-rotation (COR) offsets. An optical tracking system was used to track the excursion of ropes simulating portions of various shoulder muscles during humeral abduction, elevation, and flexion.

RESULTS

The inferior COR offset resulted in a significant increase in the deltoid moment arm in all 3 planes of motion. The lateral COR offset showed a significantly lower posterior deltoid moment arm during humeral abduction and a significantly lower lateral deltoid moment arm during humeral elevation. The posterior offset showed significantly larger anterior and lateral deltoid moment arms during humeral flexion.

DISCUSSION AND CONCLUSION

Owing to the oblique direction of the deltoid muscle across the shoulder joint, an inferior offset of the COR in reverse total shoulder arthroplasty increases the deltoid moment arm during abduction, elevation, and flexion, whereas it mainly supports humeral flexion at a posterior offset. For humeral elevation and flexion, favorable positioning of the glenosphere may, therefore, be defined by a more inferior and posterior placement compared with the non-offset position.

Repetitive Peripheral Magnetic Stimulation (rPMS) in Subjects With Migraine-Setup Presentation and Effects on Skeletal Musculature

Purpose: Repetitive peripheral magnetic stimulation (rPMS) has been successfully applied recently in migraineurs to alleviate migraine symptoms. Symptom relief has been achieved by stimulating myofascial trigger points (mTrPs) of the trapezius muscles, which are considered part of the trigemino-cervical complex (TCC). However, effects on musculature have not been assessed in detail, and the specificity of effects to muscles considered part of the TCC yet has to be elucidated. Against this background, this study presents the setup of rPMS in migraine and evaluates effects on skeletal musculature. Materials and Methods: Thirty-seven adults (mean age: 25.0 ± 4.1 years, 36 females) suffering from migraine and presenting mTrPs according to physical examination underwent rPMS either to mTrPs in the trapezius muscles (considered part of the TCC; n = 19) or deltoid muscles (considered not part of the TCC; n = 18) during six sessions over the course of 2 weeks. Standardized questionnaires were filled in to assess any adverse events and experience with rPMS as well as satisfaction and benefits from stimulation. Algometry was performed to evaluate changes in pressure pain thresholds (PPTs). Results: All stimulation sessions were successfully performed without adverse events, with 84.2% of subjects of the trapezius group and 94.4% of subjects of the deltoid group describing rPMS as comfortable (p = 0.736). Muscular pain or tension improved in 73.7% of subjects of the trapezius group and in 61.1% of subjects of the deltoid group (p = 0.077). PPTs of the trapezius muscles clearly increased from the first to the last stimulation sessions-regardless of the stimulated muscle (rPMS to the trapezius or deltoid muscles). However, depending on the examined muscles the increase of PPTs differed significantly (subjects with stimulation of trapezius muscles: p = 0.021; subjects with stimulation of deltoid muscles: p = 0.080). Conclusion: rPMS is a comfortable method in migraineurs that can improve local muscular pain or tension. Furthermore, it is able to increase directly and indirectly the PPTs of the trapezius muscles (considered part of the TCC) when applied over mTrPs, supporting the role of the TCC in migraineurs.

Muscle Activity in Upper-Body Single-Joint Resistance Exercises with Elastic Resistance Bands vs. Free Weights

Elastic resistance bands require little space, are light and portable, but their efficacy has not yet been established for several resistance exercises. The main objective of this study was to compare the muscle activation levels induced by elastic resistance bands versus conventional resistance training equipment (dumbbells) in the upper-body resistance exercises flyes and reverse flyes. The level of muscle activation was measured with surface electromyography in 29 men and women in a cross-over design where resistance loadings with elastic resistance bands and dumbbells were matched using 10-repetition maximum loadings. Elastic resistance bands induced slightly lower muscle activity in the muscles most people aim to activate during flyes and reverse flies, namely pectoralis major and deltoideus posterior, respectively. However, elastic resistance bands increased the muscle activation level substantially in perceived ancillary muscles, that is deltoideus anterior in flyes, and deltoideus medius and trapezius descendens in reverse flyes, possibly due to elastic bands being a more unstable resistance modality. Overall, the results show that elastic resistance bands can be considered a feasible alternative to dumbbells in flyes and reverse flyes.

Establishing a new appropriate intramuscular injection site in the deltoid muscle

It is becoming increasingly important for clinicians to identify a safer intramuscular (IM) injection site in the deltoid muscle because of possible complications following the vaccine administration of IM injections. We herein examined 4 original IM sites located on the perpendicular line through the mid-acromion to establish a safer IM injection site. Thirty healthy volunteers participated in this study and the distances from our 4 IM sites to some anatomical landmarks on their left arms were measured. Ultrasonography (US) was also performed to measure the thickness of the deltoid muscle and identify the posterior circumflex humeral artery (PCHA) along the course of the axillary nerve. Subcutaneous thickness was measured using 2 methods: measuring the skin thickness with caliper after pinching the skin, and with US. The results obtained revealed that the intersection between the anteroposterior axillary line (the line between the upper end of the anterior axillary line and the upper end of the posterior axillary line) and the perpendicular line from the mid-acromion was the most appropriate site for IM injections because it was distant from the axillary nerve, PCHA, and subdeltoid/subacromial brusa. At this site, depth of needle insertions was 5 mm greater than the subcutaneous thickness at a 90° angle, which was sufficient to penetrate subcutaneous tissue in both sexes. Subcutaneous thickness can be assessed with almost the same accuracy by US or measuring with calipers after pinching the skin. The results of the present study support the improved vaccine practice for safer IM injections.

How sensitive is the deltoid moment arm to humeral offset changes with reverse total shoulder arthroplasty?

BACKGROUND

Reverse total shoulder arthroplasty commonly treats cuff-deficient or osteoarthritic shoulders not amenable to rotator cuff repair. This study investigates deltoid moment arm sensitivity to variations in the joint center and humeral offset of 3 representative reverse total shoulder arthroplasty subjects. We hypothesized that a superior joint implant placement may exist, indicated by muscle moment arms, compared with the current actual surgical implant configuration.

METHODS

Moment arms for the anterior, lateral, and posterior aspects of the deltoid muscle were determined for 1521 perturbations of the humeral offset location away from the surgical placement in a subject-specific musculoskeletal model with motion defined by subject-specific in vivo abduction kinematics. The humeral offset was varied from its surgical position ±4 mm in the anterior/posterior direction, ±12 mm in the medial/lateral direction, and -10 to 14 mm in the superior/inferior direction.

RESULTS

The anterior deltoid moment arm varied in humeral offset and center of rotation up to 20 mm, primarily in the medial/lateral and superior/inferior directions. The lateral deltoid moment arm varied in humeral offset up to 20 mm, primarily in the medial/lateral and anterior/posterior directions. The posterior deltoid moment arm varied up to 15 mm, primarily in early abduction, and was most sensitive to humeral offset changes in the superior/inferior direction.

DISCUSSION

High variations in muscle moment arms were found for all 3 deltoid components, presenting an opportunity to dramatically change the deltoid moment arms through surgical placement of the reverse shoulder components and by varying the overall offset of the humerus.

LEVEL OF EVIDENCE

Basic Science Study; Computer Modeling.

Best vaccination practice and medically attended injection site events following deltoid intramuscular injection

Analysis of medically attended injection site events data provides a vehicle to appreciate the inadequacies of vaccination practice for deltoid intramuscular injection and to develop best practice procedures. These data can be divided into 3 groups; nerve palsies, musculoskeletal injuries and cutaneous reactions and reflect inappropriate site of injection, needle over or under penetration, local sepsis and vascular complications. The aim of this review is to formulate best vaccination practice procedures for deltoid intramuscular injection of vaccines through the collation and analysis of medically attended injection site events.

An unusual cause of mass in the shoulder: A primary hydatid cyst

A hydatid cyst is a zoonotic infection which may affect any organ and tissue, particularly the liver and the lung. Primary muscular hydatid cysts comprise less than 0.7-3% of the cases. The hydatid cysts must be kept in mind to avoid a diagnostic puncture in cystic lesions to avoid the spreading of the disease. In this case report, we present an exceptionally rare case with an unusual localization of a primary hydatid cyst in the left deltoid muscle.

Limb function after excision of a deltoid muscle sarcoma

BACKGROUND

Limb function after excision of deltoid muscle sarcomas has not been thoroughly investigated, although a large defect of soft tissue often causes some degree of dysfunction after wide excision. We formulated a hypothesis that the limb functional results depend on the volume of the excised deltoid muscle and examined the clinical outcomes in patients with a sarcoma in the deltoid muscle treated by surgical resection.

METHODS

The clinical outcomes of 8 patients with a malignant soft tissue tumor in the deltoid muscle were retrospectively reviewed. The following items were evaluated: type of excision of the deltoid muscle, including total excision, subtotal excision, and partial excision; surgical margins; reconstruction procedure used; postoperative complications; local recurrence; metastasis; survival; and functional results (determined by the Musculoskeletal Tumor Society scoring system).

RESULTS

After surgical resection, reconstruction in 6 of 8 patients was performed by pedicled latissimus dorsi musculocutaneous or muscle flap or pedicled trapezius musculocutaneous flap. Two patients did not undergo reconstruction because skin closure was possible. The partial excision group had a Musculoskeletal Tumor Society score of 100.0%, and the subtotal excision case and the total excision group had scores of 76.6% and 82.2%, respectively. None of the patients has demonstrated any evidence of local recurrence.

CONCLUSION

We conclude that the functional results may depend on the volume of the excised deltoid muscle. Latissimus dorsi and trapezius musculocutaneous flaps were found to be useful for covering a defect of the deltoid muscle, although these flaps did not contribute to function of the shoulder.

An unusual variation of deltoid muscle

An unusual anatomic variation of the deltoid muscle was found in a 45-year-old female cadaver during dissection of the right upper extremity. The posterior fibers of the right deltoid muscle were enclosed in a distinct fascial sheet and the deltoid muscle was seen to arise from the middle 1/3 of the medial border of the scapula. There was no accompanying vascular or neural anomaly of the deltoid muscle. To the best of our knowledge, unilateral posterior separation of the deltoid muscle with a distinct fascia has not been described previously. While dissecting deltoid, posterior deltoid, or scapular flaps, the surgeon needs to look out for this variation because it may cause confusion.