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Concept: Muscles of the upper limb

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BACKGROUND: Variations in the major arteries of the upper limb are estimated to be present in up to one fifth of people, and may have significant clinical implications. CASE PRESENTATION: During routine cadaveric dissection of a 69-year-old fresh female cadaver, a superficial brachioulnar artery with an aberrant path was found bilaterally. The superficial brachioulnar artery originated at midarm level from the brachial artery, pierced the brachial fascia immediately proximal to the elbow, crossed superficial to the muscles that originated from the medial epicondyle, and ran over the pronator teres muscle in a doubling of the antebrachial fascia. It then dipped into the forearm fascia, in the gap between the flexor carpi radialis and the palmaris longus. Subsequently, it ran deep to the palmaris longus muscle belly, and superficially to the flexor digitorum superficialis muscle, reaching the gap between the latter and the flexor carpi ulnaris muscle, where it assumed is usual position lateral to the ulnar nerve. CONCLUSION: As far as the authors could determine, this variant of the superficial brachioulnar artery has only been described twice before in the literature. The existence of such a variant is of particular clinical significance, as these arteries are more susceptible to trauma, and can be easily confused with superficial veins during medical and surgical procedures, potentially leading to iatrogenic distal limb ischemia.

Concepts: Blood pressure, Muscle, Ulna, Forearm, Median nerve, Brachial artery, Muscles of the upper limb, Ulnar artery

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PURPOSE: It is commonly stated that supraspinatus initiates abduction; however, there is no direct evidence to support this claim. Therefore, the aims of the present study were to determine whether supraspinatus initiates shoulder abduction by activating prior to movement and significantly earlier than other shoulder muscles and to determine if load or plane of movement influenced the recruitment timing of supraspinatus. METHODS: Electromyographic recordings were taken from seven shoulder muscles of fourteen volunteers during shoulder abduction in the coronal and scapular planes and a plane 30° anterior to the scapular plane, at 25%, 50% and 75% of maximum load. Initial activation timing of a muscle was determined as the time at which the average activation (over a 25ms moving window) was greater than three standard deviations above baseline measures. RESULTS: All muscles tested were activated prior to movement onset. Subscapularis was activated significantly later than supraspinatus, infraspinatus, deltoid and upper trapezius, while supraspinatus, infraspinatus, upper trapezius, lower trapezius, serratus anterior and deltoid all had similar initial activation times. The effects of load or plane of movement were not significant. CONCLUSIONS: Supraspinatus is recruited prior to movement of the humerus into abduction but not earlier than many other shoulder muscles, including infraspinatus, deltoid and axioscapular muscles. The common statement that supraspinatus initiates abduction is therefore, misleading.

Concepts: Humerus, Shoulder, Rotator cuff, Supraspinatus muscle, Deltoid muscle, Muscles of the upper limb, Scapula, Serratus anterior muscle

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McAllister, MJ, Schilling, BK, Hammond, KG, Weiss, LW, and Farney, TM. Effect of grip width on electromyographic activity during the upright row. J Strength Cond Res 27(1): 181-187, 2013-The upright row (URR) is commonly used to develop the deltoid and upper back musculature. However, little information exists concerning muscle recruitment during variations of this exercise. Sixteen weight-trained men completed 2 repetitions each in the URR with 3 grip conditions: 50, 100, and 200% of the biacromial breadth (BAB). The load was the same for all grip conditions and was equal to 85% of the 1RM determined at 100% BAB. Repeated measures analyses of variance were used to compare the maximal activity of the anterior deltoid (AD), lateral deltoid (LD), posterior deltoid (PD), upper trapezius (UT), middle trapezius (MT), and biceps brachii (BB) during the 3 grip widths for eccentric and concentric actions. Significant differences (p < 0.05) were noted in concentric muscle activity for LD (p < 0.001) and PD (p < 0.001), and in eccentric muscle activity for AD (p = 0.023), LD (p < 0.001), UT (p < 0.001), MT (p < 0.001), and BB (p = 0.003). Bonferroni post hoc analysis revealed significant pairwise differences in the concentric actions from the LD (50% vs. 200% BAB and 100% vs. 200% BAB) and PD (50% vs. 200% BAB and 100% vs. 200% BAB), and eccentric actions of the LD (all comparisons), UT (all comparisons), MT (50% vs. 200% BAB and 100% vs. 200% BAB), and BB (50% vs. 200% BAB), with large-to-very-large effect sizes (ESs). Moderate-to-large ESs were noted for several nonsignificant comparisons. The main findings of this investigation are increased deltoid and trapezius activity with increasing grip width, and correspondingly less BB activity. Therefore, those who seek to maximize involvement of the deltoid and trapezius muscles during the URR should use a wide grip.

Concepts: Muscle, Biceps brachii muscle, Electromyography, Muscle contraction, Deltoid muscle, Muscles of the upper limb, Clavicle, Glenohumeral joint

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/st> The influence of the muscular response elicited by neurostimulation on the success rate of interscalene block using a catheter (ISC) is unknown. In this investigation, we compared the success rate of ISC placement as indicated by biceps or deltoid, triceps, or both twitches.

Concepts: Muscle, Biceps brachii muscle, Triceps brachii muscle, Muscles of the upper limb

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Abstract Immediate breast reconstruction with tissue expander has become an increasingly popular procedure. Complete coverage of the expander by a musculofascial layer provides an additional well-vascularised layer, reducing the rate of possible complications of skin necrosis, prosthesis displacement, and the late capsular contracture. Complete expander coverage can be achieved by a combination of pectoralis major muscle and adjacent thoracic fascia in selected patients. Seventy-five breast mounds in 59 patients were reconstructed, in the first stage a temporary tissue expander inserted immediately after mastectomy and a musculofascial layer composed of the pectoralis major muscle, the serratus anterior fascia, and the superficial pectoral fascia were created to cover the expander. The first stage was followed months later by implant insertion. Minor and major complications were reported in a period of follow-up ranging from 24-42 months (mean 31 months). Complete musculofascial coverage of the tissue expander was a simple and easy to learn technique providing that the patient has a well-formed and intact superficial pectoral and serratus anterior fascia. From a total of 75 breast mounds reconstructed, major complications rate was 4% (overall rate of 19.8%), including major seroma (n = 4), haematoma (n = 1), partial skin loss (n = 3), wound dehiscence (n = 1), major infection (n = 2), severe capsule contracture (n = 1), and expander displacement (n = 3). The serratus anterior fascia and the superficial pectoral fascia flaps can be effectively used as an autologous tissue layer to cover the lower and the lateral aspect of tissue expanders in immediate breast reconstruction after mastectomy.

Concepts: Plastic surgery, Breast, Breast reconstruction, Muscles of the upper limb, Pectoralis major muscle, Medial pectoral nerve, Tissue expansion

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Dunnick, DD, Brown, LE, Coburn, JW, Lynn, SK, and Barillas, SR. Bench press upper-body muscle activation between stable and unstable loads. J Strength Cond Res 29(12): 3279-3283, 2015-The bench press is one of the most commonly used upper-body exercises in training and is performed with many different variations, including unstable loads (ULs). Although there is much research on use of an unstable surface, there is little to none on the use of an UL. The purpose of this study was to investigate muscle activation during the bench press while using a stable load (SL) vs. UL. Twenty resistance-trained men (age = 24.1 ± 2 years; ht = 177.5 ± 5.8 cm; mass = 88.7 ± 13.7 kg) completed 2 experimental conditions (SL and UL) at 2 different intensities (60 and 80% one repetition maximum). Unstable load was achieved by hanging 16 kg kettlebells by elastic bands from the end of the bar. All trial lifts were set to a 2-second cadence with a slight pause at the bottom. Subjects had electrodes attached to 5 muscles (pectoralis major, anterior deltoid, medial deltoid, triceps brachii, and latissimus dorsi) and performed 3 isometric bench press trials to normalize electromyographic data. All 5 muscles demonstrated significantly greater activation at 80% compared with 60% load and during concentric compared with eccentric actions. These results suggest that upper body muscle activation is not different in the bench press between UL and SL. Therefore, coaches should use their preference when designing training programs.

Concepts: Biceps brachii muscle, Triceps brachii muscle, Muscle contraction, Trigraph, Bench press, Muscles of the upper limb, Pectoralis major muscle, Barbell

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DeQuervain’s tenosynovitis is a common cause of radial-sided wrist pain. Symptoms result from a narrow first dorsal compartment and associated tendinosis of the enclosed extensor pollicis brevis and/or abductor pollicis longus (APL). Surgical intervention, offered when conservative measures fail to adequately relieve symptoms, requires a detailed understanding of potentially aberrant anatomy in order to avoid persistence or recurrence of symptoms. We describe a case whereby the patient presented with complaints of thumb triggering in extension and associated disabling first dorsal compartment tendinosis. Intraoperatively, after supernumerary tendons were identified and addressed, the APL was at risk for subluxation over a prominent fibroosseous ridge. Routine first dorsal compartment release alone may have failed to address all of this patient’s pathology.

Concepts: Surgery, Failure, Extension, Extensor pollicis brevis muscle, Muscles of the upper limb, Tendinitis, Adductor pollicis muscle

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To provide a quantitative and qualitative anatomic analysis of the pectoralis major, teres major, and latissimus dorsi on the humerus, as well as the deltoid tendinous attachments on the proximal humerus and acromion, and to quantitatively characterize the humeral course of the axillary nerve.

Concepts: Humerus, Qualitative research, Shoulder, Rotator cuff, Teres minor muscle, Deltoid muscle, Muscles of the upper limb, Axillary nerve

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Study Design Laboratory study. Background The activity of the rotator cuff muscles has not previously been measured with indwelling electromyography activity (iEMG) comparing ambulation and other movements. Knowledge of the relative contribution of these muscles during various tasks will help guide rehabilitation progression. Objective To measure activity of the rotator cuff muscles and other shoulder muscles during normal ambulation, shirt and sling donning and doffing, and rehabilitation tasks commonly performed after rotator cuff surgery. Methods In 28 volunteers (15 men, 13 women; mean age, 32.2 years), iEMG activity was measured in the supraspinatus, infraspinatus, teres minor, and subscapularis muscles during various tasks; sEMG activity was measured in the middle deltoid, biceps, and upper trapezius muscles. Results Using median EMG activity, in general, donning and doffing a shirt or sling recruited the rotator cuff muscles more than the other 7 tasks tested. Self-ranging motion using pulleys, especially in the scapular plane, was also consistently associated with greater recruitment of the shoulder muscles. Pendulum exercises, passive range of motion (PROM) by a physical therapist (PT), and self-ranging motion with a dowel recruited the shoulder muscles to a lesser extent. Conclusion Our results demonstrate that rehabilitation tasks such as pendulum exercises, PROM by a PT, and self-ranging motion with a dowel show low EMG activity, whereas pulleys in the sagittal plane and scapular plane show greater activity with scapular plane activity consistently higher than sagittal plane, and ambulation without a sling and donning and doffing a sling and a shirt consistently show still higher activity. J Orthop Sports Phys Ther, Epub 6 Apr 2016. doi:10.2519/jospt.2016.6090.

Concepts: Electromyography, Shoulder, Rotator cuff, Teres minor muscle, Supraspinatus muscle, Deltoid muscle, Infraspinatus muscle, Muscles of the upper limb

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Due to the versatility of the press-up it is a popular upper extremity strengthening and rehabilitation exercise. Press-up programmes are often progressed by increasing weight-bearing load and using unstable bases of support. Despite the popularity of the press-up research examining press-up variations is limited. The aim of the study was to examine the influence of common press-up exercises on serratus anterior, infraspinatus, anterior deltoid, pectoralis major and latissimus dorsi muscles overall EMG activity. Twenty-one healthy individuals participated in this study. Surface electrodes were placed on pectoralis major, anterior deltoid, infraspinatus, serratus anterior and latissimus dorsi muscles. Participants were tested under 7 static press-up conditions that theoretically progressively increase weight-bearing load and proprioceptive challenge while surface electromyographic activity was recorded. There was a high correlation between increased weight-bearing load and increased EMG activity for all muscles in stable base conditions. The introduction of the unstable base conditions resulted in an activation decline in all muscles. Within the two-armed press-up the Swiss ball resulted in decreased activation in all muscles except pectoralis major. Serratus anterior demonstrated the greatest activation as a percentage of maximum isometric contraction across all exercises. The findings of this study indicate that by varying the weight-bearing load and base of support whilst in the press-up position results in significantly different demands on shoulder and scapula muscles.

Concepts: Electromyography, Shoulder, Rotator cuff, Supraspinatus muscle, Muscles of the upper limb, Clavicle, Glenohumeral joint, Scapula