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Abstract Background We report two cases of biceps brachii and brachialis paralysis due to musculocutaneous nerve injury in which elbow joint flexion was reconstructed using rotational transfer of the latissimus dorsi muscle with sutures to the radial and ulnar tuberosities, thereby enabling flexion by simultaneous activation of the humeroradial and humeroulnar joints. In cases of associated brachialis paralysis, weaker flexion strength can be expected when the forearm is in a pronated position than when it is in a supinated state. To the best of our knowledge, no previous study has reported the rotational position of the forearm during elbow joint flexion reconstruction. Case presentation Case 1 involved a 30-year-old Asian male who presented with a rupture of the musculocutaneous, median, radial, and ulnar nerves. Reconstruction was performed by rotational transfer of the latissimus dorsi muscle. In this case, the supination and pronation flexion forces were equal. Case 2 involved a 50-year-old Asian man who presented with partial loss of the musculocutaneous nerve, biceps brachii, and pectoralis major due to debridement. Reconstruction was performed by rotational transfer of the latissimus dorsi muscle. In this case, supination and pronation flexion strengths were demonstrated to be equal. Our reconstruction method used the rotational transfer of the latissimus dorsi muscle; the distal muscle flap was divided into radial and ulnar sides to allow elbow joint flexion by simultaneously activating the humeroradial and humeroulnar joints. These sides were then fixed to the anchors at the radial and ulnar tuberosities. Finally, they were wrapped around the myotendinous junction of the biceps brachii or brachialis and secured using sutures. Conclusions Although larger studies are required to verify these methods, this case study successfully demonstrates the following: (1) the flexion strength in the supinated position was equal to that in the pronated position; (2) the stability of the humeroradial and humeroulnar joints was unaffected by the forearm's rotational position; and (3) a satisfactory range of motion of the elbow joint was obtained, with no complications.

Background: We report two cases of biceps brachii and brachialis paralysis due to musculocutaneous nerve injury in which elbow joint flexion was reconstructed using rotational transfer of the latissimus dorsi muscle with sutures to the radial and ulnar tuberosities, thereby enabling flexion by simultaneous activation of the humeroradial and humeroulnar joints. In cases of associated brachialis paralysis, weaker flexion strength can be expected when the forearm is in a pronated position than when it is in a supinated state. To the best of our knowledge, no previous study has reported the rotational position of the forearm during elbow joint flexion reconstruction. Case presentation: Case 1 involved a 30-year-old Asian male who presented with a rupture of the musculocutaneous, median, radial, and ulnar nerves. Reconstruction was performed by rotational transfer of the latissimus dorsi muscle. In this case, the supination and pronation flexion forces were equal. Case 2 involved a 50-year-old Asian man who presented with partial loss of the musculocutaneous nerve, biceps brachii, and pectoralis major due to debridement. Reconstruction was performed by rotational transfer of the latissimus dorsi muscle. In this case, supination and pronation flexion strengths were demonstrated to be equal. Our reconstruction method used the rotational transfer of the latissimus dorsi muscle; the distal muscle flap was divided into radial and ulnar sides to allow elbow joint flexion by simultaneously activating the humeroradial and humeroulnar joints. These sides were then fixed to the anchors at the radial and ulnar tuberosities. Finally, they were wrapped around the myotendinous junction of the biceps brachii or brachialis and secured using sutures. Conclusions: Although larger studies are required to verify these methods, this case study successfully demonstrates the following: (1) the flexion strength in the supinated position was equal to that in the pronated position; (2) the stability of the humeroradial and humeroulnar joints was unaffected by the forearm's rotational position; and (3) a satisfactory range of motion of the elbow joint was obtained, with no complications. [ABSTRACT FROM AUTHOR]

Congenital lack of elbow flexion results in significant disability and may be seen in conjunction with syndromes, plexopathies, neuromuscular disorders, or as an isolated muscular agenesis of elbow flexors. There are many tendon transfer options to address this issue, but there is a lack of data on the functional results in the pediatric population. In this series, we present 1 patient with isolated muscular agenesis of the biceps and brachialis musculotendinous units and another with this same muscular agenesis in the setting of arthrogryposis. They were treated with anterior ulnar nerve transposition and transfer of the long head of triceps tendon around 2 years of age resulting in functional elbow flexion in both patients. [ABSTRACT FROM AUTHOR]

Variations of the brachialis muscle are uncommon in the literature. During regular cadaveric dissection, we observed the unilateral presence of an accessory muscle in the front of the right arm of a female cadaver, taking its origin from the medial aspect of the brachialis and the adjacent intermuscular septum. The muscle belly descended downwards, crossed the neurovascular bundle in the cubital fossa and merged with the fibres of the pronator teres. There is no doubt regarding its significance in the etiogenesis of numerous compression syndromes due to its close topographical relationship with the neurovascular bundle. In our report, we consider the potential developmental process and therapeutic implications of this variation, which can aid surgeons in their strategy and management. [ABSTRACT FROM AUTHOR]

Introduction: Variations within musculocutaneus nerve (MCN) are very frequent. Such cases should be discussed extensively to reduce the risk of iatrogenic damage during surgery. Aim: In this paper, we wanted to present the unusual variability within the brachial plexus, which is the double MCN. Case study: We present a case of accesory MCN found during the cadaveric dissection. Results and discussion: In this paper we encountered two musculocutaneous nerves, of which MCN proper runs as standard innervating the biceps brachii and the coracobrachialis muscle, while MCN accessory extending distally from MCN proper and innervates the brachialis. Conclusions: The case analysed by us is rare in the literature. Brachial plexus variations are very common and clinically important. [ABSTRACT FROM AUTHOR]

Introduction: Ultrasound is useful in assessing patients with snapping syndromes around the elbow joint. The dynamic nature of the examination allows for direct visualisation of the underlying causative factor. Topic description: We discuss the role of dynamic ultrasound in assessing various snapping syndromes around the elbow, such as ulnar nerve instability, snapping triceps and less commonly, snapping brachialis. Ultrasound is also useful in evaluating the distal biceps tendon, particularly in differentiating partial from complete tendon injury. Discussion: Ulnar nerve instability and snapping triceps can be assessed via a medial approach with the transducer placed transversely between the medial epicondyle and the olecranon. In ulnar nerve instability, the nerve can be seen crossing over the medial epicondyle on elbow flexion. In snapping triceps syndrome, both the ulnar nerve and the distal triceps can be seen dislocating over the medial epicondyle. Dynamic assessment of the distal biceps tendon using a lateral approach minimises anisotropy artefact often seen on the anterior approach. Passive pronation and supination of the forearm will reveal little or no movement in a completely torn tendon whereas moving tendon fibres will be appreciated in partial tears. In a snapping brachialis, the medial portion of brachialis will be seen abnormally translocating anterolateral to the medial border of the trochlea during elbow flexion and snapping back into its normal position on elbow extension. Conclusion: Dynamic ultrasound of the elbow is valuable in diagnosing patients with snapping sensations around the joint and in evaluating the integrity of the distal biceps tendon. [ABSTRACT FROM AUTHOR]

Elbow dislocation is the second most common type of joint dislocation in adults and the most common joint dislocation in children. These dislocations are commonly associated with significant soft tissue injury and/or fractures. Anterior dislocation of the radio‐capitellar articulation is uncommon. Failure of relocation of the radial head due to soft tissue imposition requiring open reduction is rare, however, is extremely important to recognise clinically and radiologically. This case report describes a case of anterior dislocation of the radio‐capitellar joint due to entrapment of the brachialis tendon lateral to the radial head and discusses the radiological assessment and the spectrum of causes of a clinically irreducible radio‐capitellar joint. Misdiagnosis of a dislocation or failed reduction may result in long‐term functional sequelae for the patient. [ABSTRACT FROM AUTHOR]

Purpose: Flexion contracture of the elbow is a common deformity associated with brachial plexus birth palsy and is often managed with preventive night orthoses. For severe cases, however, surgical interventions may become necessary. This study evaluated the effectiveness of surgically releasing elbow flexion contractures exceeding 30° through partial tenotomy of the brachialis and biceps brachii muscles, along with a division of the lacertus fibrosus., Methods: We performed 36 anterior elbow releases on patients with injury to the upper trunk (C5-C6) of the brachial plexus and elbow flexion contractures between 30° and 80°. All releases involved lacertus fibrosus section and partial lengthening of the distal portion of the brachialis tendon. In severe cases, biceps brachii tenotomy was also performed. All participants had a minimum follow-up of 12 months and preoperative elbow flexion strength of at least grade 4 on the British Medical Research Council scale, with no deformities in the shape of the ulnohumeral joint or radial head subluxation., Results: Following a mean follow-up of 41 months, the average extension gain was 31° (range, 10°-50°). All patients maintained their flexion strength. Except for two participants with weaker triceps, the mean elbow extension gain was sustained throughout the follow-up period. There were no major or minor complications or reinterventions in the study., Conclusions: Partial tenotomy of the brachialis and biceps brachii muscles, coupled with lacertus fibrosus section, is an effective treatment for elbow contractures exceeding 30° flexion. This method is successful in individuals with a functioning triceps brachii and elbow extension strength of at least grade 3 on the British Medical Research Council scale., Type of Study/level of Evidence: Therapeutic IV., Competing Interests: Conflicts of Interest No benefits in any form have been received or will be received related directly to this article., (Copyright © 2024 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

We describe the patterns of motor branches to the elbow flexors in 106 fresh-frozen cadaveric upper extremities from 53 donors of the Latin American mestizo race. We identified a 20% incidence of an accessory biceps head. The innervation patterns to this accessory head were specifically described and added to the Yang classification as Type IV for the biceps and Type III for the brachialis. The patterns arising from the musculocutaneous nerve to the biceps brachii were of Type I in 69%, Type II in 9%, Type III in 7% and Type IV in 11%, and to the brachialis of Type I in 77%, Type II in 11% and Type III in 9%. In 4%, the branches did not originate from the musculocutaneous nerve. We hypothesize that the branch to the accessory biceps head might be considered as a donor for nerve transfer in selected brachial plexus injuries. [ABSTRACT FROM AUTHOR]

Introduction: Preventing nerve injury is critical in elbow surgery. Distal extension of medial approaches, required for coronoid fracture fixation and graft-replacement, may endanger the median nerve. This study aims to describe an easily identifiable and reproducible anatomical landmark to localize the median nerve distal to the joint line and to delineate how its relative position changes with elbow flexion and forearm rotation. Materials and methods: The median nerve and the ulnar insertion of the brachialis muscle were identified in eleven fresh-frozen cadaveric specimens after dissection over an extended medial approach. The elbow was brought first in full extension and then in 90° flexion, and the shortest distance between the two structures was measured while rotating the forearm in full pronation, neutral position and full supination. Results: The distance between the median nerve and the brachialis insertion was highest with the elbow flexed and the forearm in neutral position. All distances measured in flexion were larger than those in extension, and all distances measured from the most proximal point of the brachialis insertion were larger than those from the most distal point. Distances in pronation and in supination were smaller than to those in neutral forearm position. Conclusions: The ulnar insertion of the brachialis is a reliable landmark to localize and protect the median nerve at the level of the coronoid base. Elbow flexion and neutral forearm position increase significantly the safety margins between the two structures; this information suggests some modifications to the previously described medial elbow approaches. Level of evidence: Basic Science Study. [ABSTRACT FROM AUTHOR]

To investigate the effect of muscle selection for botulinum neurotoxin A (BoNT-A) treatment on spasticity in patients with post-stroke elbow flexor muscle over-activity. Chronic stroke patients with a deforming spastic paresis in the upper limb (elbow flexion with forearm pronation) who were injected BoNT-A into at least one of elbow flexor muscles (brachialis, brachioradialis, and biceps brachii) were included in this prospective observational study. The main outcome measure was spasticity angle by Tardieu Scale recorded at pre-treatment and week 4 after treatment. Three muscle selection groups with sufficient sample size for statistical analysis were able to be created; brachialis (n = 14), biceps brachii (n = 21), and brachialis plus brachioradialis (n = 11). Although there was a significant improvement in spasticity angle within all groups over time (p < 0.05), the change in spasticity angle was not different between the groups (p > 0.05 for each pairwise comparison). However, the magnitude of the change in spasticity angle was larger in the groups in which brachialis was preferred. In stroke patients with a spontaneous spastic posture of elbow flexion and forearm pronation, targeting brachialis for BoNT-A injection seems more effective in reducing the severity of spasticity. NCT04036981 [ABSTRACT FROM AUTHOR]

Introduction: Brachial plexus are the main nerve supply to the muscles of upper limb and the muscles of the flexor compartment arm are supplied by Musculocutaneous Nerve (McN). Any variations in the nerve innervation of the flexor muscles of arm should be documented as they have clinical implications. Aim: To observe and document the variations in the innervation of muscles of the front of arm and discuss its clinical implications with the help of available literature. Materials and Methods: This cross-sectional descriptive study was done in the Department of Anatomy, Siddhartha Medical College for a period of three years that is from October 2017 to October 2020 on 50 upper limbs, from 25 cadavers. The upper limbs were dissected to observe the innervations of muscles of front of arm. Contents of front of arm were observed. Incidence and percentage of variation in the population was tabulated. Results: Variations in the nerve supply of muscles of front of arm were noticed in 6% of the cases. In two cadavers (4%), all the muscles of right arm except coracobrachialis were innervated by a trifurcated branch from Median Nerve (MN) and the latter was supplied by a separate branch from lateral cord. In another left upper limb two separate branches innervated from lateral cord and supplied all the muscles of arm. In the present study, observed variations were more common on right side than on the left side. Conclusion: Knowledge of such variations are important for the surgeons during surgical exploration of axilla, nerve block in supraclavicular, infraclavicular or axillary region and also during nerve grafting. Also, the study highlights the incidence of variations in a particular region.

Background. The dual innervation of the brachialis muscle by musculocutaneous and radial nerves has been described and adopted, despite being traditionally known to have singular innervation as other flexors in the anterior compartment of the arm. However, the prevalence, course and patterns of distribution of its radial innervation varies in different population, and in the Ghanaian population, no information has been described. Methods. Thirty-eight (n = 38) cadaveric upper limbs (18 paired and 2 single), routinely used by medical students at the Department of Anatomy and Cell Biology, University of Cape Coast, Ghana, were dissected. The brachialis muscle was exposed in its entire length, and the radial nerve exposed in its course from the spiral groove to the elbow, noting the presence or absence of radial branches to the muscle, number of branches, nature and pattern of branching, level at which the branching occurred, and the level at which branches pierced the muscle. Results. All specimens were innervated by the musculocutaneous nerve, 76.3% had dual innervation. The radial nerve originated and pierced the muscle at varying levels. Sixty nine percent had solitary radial nerve fibre, and 31.0% had multiple branching patterns. None had more than 2 branches of the radial nerve. The prevalence of dual innervation of the brachialis muscle in the Ghanaian population appears to be high, and the pattern of branching and distribution of the radial nerve fibres differ from those reported in earlier studies. Conclusions. This knowledge is invaluable in choosing surgical approaches so as to minimize denervation of the brachialis muscle. [ABSTRACT FROM AUTHOR]

Elbow stiffness secondary to trauma or surgical reconstruction can sometimes result in a severe contracture with restricted joint space, and arthroscopic access to the joint is difficult. Previous surgery and severe stiffness can also alter the position of neurovascular structures and iatrogenic injury is possible with an inside-out arthroscopic approach. To overcome these technical difficulties, an endoscopic approach to the anterior capsule can be performed as an alternative to open approach. The endoscopic approach utilises the sub-brachialis space for an outside-in capsular resection under vision. Identification of standard anatomic landmarks is useful as a guide for safe resection in a central to peripheral direction., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Associate Editor JSES International., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Antecubital pain can be caused by a myriad of pathologies. Abnormalities of the brachialis, in particular, tendinopathy at its insertion, are extremely rare, with no case report in the literature. We report the first case of tendinopathy of the brachialis tendon at its insertion in a 42-year-old male who presented with a year-long history of antecubital pain. The anatomy of the brachialis and the technique for ultrasound-guided steroid injection of the brachialis will also be described. [ABSTRACT FROM AUTHOR]

Background: Myositis ossificans is an uncommon complication of trauma and surgery, defined as ossifying changes in a non-osseous tissue such as muscles. It happens after tissue injury, with or without fractures. When myositis ossificans occurs around a joint, it can cause ankylosis, leading to complete dysfunction of the joint. Though it has been described in most parts of the body, bridging myositis ossificans involving the elbow joint were scarcely reported.Case Presentation: We report a severe case of myositis ossificans after a supracondylar humerus fracture in a 9-year-old child. In this case a palpable painless mass appeared following the fracture and surgical trauma. Ultrasound or X-ray is of significant diagnostic value. The brachialis was completely ossified and formed a bony bridge around the elbow, causing complete ankylosis. The bone mass was surgically removed through a bilateral less-invasive approach with less surgical trauma 9 months after initial presentation. we applied bone wax to the fresh bone wounds to prevent the formation of hematocele. Indomethacin, a non-steroidal anti-inflammatory drug, was administered after the operation to suppress bone proliferation in our case. Our patient had the best possible functional status and no recurrence at 2 years' follow-up.Conclusion: Elbow myositis ossificans in children may mainly affects the brachialis. A bilateral less-invasive approach is sufficient to remove the bone mass with less surgical trauma. This case also provides a new reference for the treatment of myositis ossificans after the elbow injuries.

Tendon injuries at the elbow affect mostly the distal biceps and can progressively degenerate over time or rupture in an acute event. The degree of retraction may depend on the integrity of the lacertus fibrosus, a fibrous expansion that merges with the forearm flexor fascia. Biceps disorders are frequently associated with fluid or synovitis of the adjacent bicipital bursa; primary bursal disorders (primary inflammatory synovitis) can also be observed. Distal triceps is less frequently injured than the distal biceps, and tears usually manifest as distal ruptures with avulsion of a small flake of bone from the tip of the olecranon. Brachialis injuries are uncommon and the consequence of sudden muscle stretching during forced elbow hyperextension, as in posterior elbow luxation. [ABSTRACT FROM AUTHOR]

Background: The Southern Karaman sheep, which is very fertile in terms of meat and milk production and is often preferred in livestock raising, is known as a domestic sheep breed. The Hasak sheep is a breed formed by the triple crossbreeding of the German Black-headed, Hampshire and Akkaraman breeds. Arterial feeding of the forelimb is provided by arteria axillaris, a continuation of arteria subclavia. In this study, it was aimed to examine the forelimb arteries in Southern Karaman and Hasak sheep breeds.Materials and Methods: Totally, 8 Southern Karaman and 8 Hasak sheep were obtained from Konya Bahri Dagdas International Agricultural Institute. The sheep were anesthetised with xylazine and ketamine and extravasated by cutting the arteria carotis communis in the neck area of the sheep. The forelimbs of the sheep separated from the body were fixed in 10% formaldehyde solution and then dissections were made and the course and branching of the arteries were examined.Results: It was determined that the arteria brachialis was divided into two main branches as distal arteria brachialis and proximal arteria subscapularis at the articulatio humeri level of the arteria axillary. Arteria mediana, which is a continuation of arteria brachialis, was also examined in different parts of antebrachium and ended by splitting into branches.Conclusions: According to the findings of the Southern Karaman and Hasak sheep breeds, it was determined that the forelimb arteries had some anatomical differences but were similar in structure to many sheep breeds. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine in vivo moment arm lengths (MAs) of three elbow flexors at rest and during low- and relatively high-intensity contractions, and to examine the contraction intensity dependence of MAs at different joint positions. At 50°, 80° and 110° of elbow flexion, MAs of the biceps brachii, brachialis and brachioradialis were measured in 10 young men using sagittal images of the right arm obtained by magnetic resonance imaging, at rest and during 20% and 60% of isometric maximal voluntary elbow flexion. In most conditions, MAs increased with isometric contractions, which is presumably due to the contraction-induced thickening of the muscles. This phenomenon was especially evident in the flexed elbow positions. The influence of the contraction intensities on the increases in MAs varied across the muscles. These results suggest that in vivo measurements of each elbow flexor MA during contractions are essential to properly examine the effects on the interrelationships between elbow flexion torque and individual muscle forces. [ABSTRACT FROM AUTHOR]

Isolated traumatic brachialis muscle tears are uncommonly reported – leading to occasional misdiagnosis and misdirected treatment. The rarity of brachialis muscle tear may promote misdiagnosis or mistreatment of this injury. We report an isolated brachialis muscle tear in a young female, possibly caused by strenuous exercise in the gymnasium. The diagnosis was made clinically and confirmed by magnetic resonance imaging. The patient was subsequently managed adequately with conservative treatment. We herein present a 35-year-old woman who was diagnosed with an acute brachialis muscle tear being diagnosed with a combination of clinical signs and imaging and successfully managed non-operatively. A chronologically arranged review of literature is also presented.

Purpose: The brachialis (BM) is a complex muscle with a long-running controversy regarding its morphology and innervation. The primary objective of this study was to elucidate the detailed gross morphology of BM in an adult Sri Lankan population.Method: Cadaveric upper limbs (n = 240) were examined for the proximal and distal attachments, length, width, thickness of BM, and innervations by the musculocutaneous (MCN) and radial nerve (RN).Results: In all cases, the BM consisted of two heads: superficial head (SHB) and deep head (DHB). Proximally SHB and DHB originated from the lateral, anterior, and medial aspects of the middle and distal thirds of the shaft of the humerus and inserted onto the coronoid process and the tuberosity of ulna, respectively, as two separate entities. Statistically significant (P < 0.05) gender differences were observed between the mean values (mm) of muscle length (male: 188.03 ± 10.54; female: 166.14 ± 7.97), width (male: 26.57 ± 4.80; female: 25.28 ± 4.67), thickness (male: 10.73 ± 1.74; female: 9.74 ± 1.28), and tendon length (male: 44.44 ± 7.73; female: 33.40 ± 5.09). In all cases, MCN innervated the BM, while the model site of piercing was in the middle third of the muscle. The incidence of RN contribution to BM was 83.33% and in the vast majority it pierced the inferior third of the BM.Conclusion: Present study provides a comprehensive anatomical overview of the BM. An in-depth knowledge of the anatomy of BM may aid in comprehending functional characteristics, enhance the accuracy of imaging modalities, and provide new insight to the current surgical approaches around the elbow joint which in turn will invariably minimize the potential complications encountered during clinical procedures. [ABSTRACT FROM AUTHOR]

Abstract This study tested the hypothesis that the ratio of changes in muscle fascicle and tendon length that occurs with joint movement scales linearly with the ratio of the slack lengths of the muscle fascicles and tendons. We compared the contribution of muscle fascicles to passive muscle‐tendon lengthening in muscles with relatively short and long fascicles. Fifteen healthy adults participated in the study. The medial gastrocnemius, tibialis anterior, and brachialis muscle‐tendon units were passively lengthened by slowly rotating the ankle or elbow. Change in muscle fascicle length was measured with ultrasonography. Change in muscle‐tendon length was calculated from estimated muscle moment arms. Change in tendon length was calculated by subtracting change in fascicle length from change in muscle‐tendon length. The median (IQR) contribution of muscle fascicles to passive lengthening of the muscle‐tendon unit, measured as the ratio of the change in fascicle length to the change in muscle‐tendon unit length, was 0.39 (0.26–0.48) for the medial gastrocnemius, 0.51 (0.29–0.60) for tibialis anterior, and 0.65 (0.49–0.90) for brachialis. Brachialis muscle fascicles contributed to muscle‐tendon unit lengthening significantly more than medial gastrocnemius muscle fascicles, but less than would be expected if the fascicle contribution scaled linearly with the ratio of muscle fascicle and tendon slack lengths.

To confirm the existence of epimuscular myofascial force transmission in humans, this study examined if manipulating joint angle to stretch the muscle can alter the shear modulus of a resting adjacent muscle, and whether there are regional differences in this response. The biceps brachii (BB: manipulated muscle) and the brachialis (BRA: resting adjacent muscle) were deemed suitable for this study because they are neighboring, yet have independent tendons that insert onto different bones. In order to manipulate the muscle length of BB only, the forearm was passively set at supination, neutral, and pronation positions. For thirteen healthy young adult men, the shear modulus of BB and BRA was measured with shear-wave elastography at proximal and distal muscle regions for each forearm position and with the elbow joint angle at either 100° or 160°. At both muscle regions and both elbow positions, BB shear modulus increased as the forearm was rotated from a supinated to pronated position. Conversely, BRA shear modulus decreased as function of forearm position. The effect of forearm position on shear modulus was most pronounced in the distal muscle region when the elbow was at 160°. The observed alteration of shear modulus of the resting adjacent muscle indicates that epimuscular myofascial force transmission is present in the human upper limb. Consistent with this assertion, we found that the effect of muscle length on shear modulus in both muscles was region-dependent. Our results also suggest that epimuscular myofascial force transmission may be facilitated at stretched muscle lengths. [ABSTRACT FROM AUTHOR]

Introduction: Major anatomical textbooks generally state that the biceps brachii muscle (BB) is composed of long and short heads, whereas the brachialis muscle (BR) consists of a single head. However, the numbers of heads comprising the BB and the BR are very variable. The purpose of this study was to investigate how the branching patterns of the musculocutaneous nerve (MC) influence the number of heads of the BB and the BR.Materials and methods: Morphological examinations of the BB and MC were conducted using cadavers of 22 Japanese individuals, and morphological examinations of the BR and the MC were conducted in 9 of those 22 individuals.Results: A three-headed BB was observed in 7 of the 22 specimens (31.8%). Most of these specimens showed a Type III branch pattern (after penetrating the long head or the short head, the MC innervated the supernumerary head or communicated with the main root again). The number of BR heads was categorized into three types: Type A, two heads (superficial and deep heads, 22.2%); Type B, three or four heads (two or three superficial heads and one deep head, 44.4%); and Type C, multiple heads (33.3%). Among these categories, branches of the MC in Type A specimens were most simple.Conclusion: A supernumerary head of the BB seemed to be present if the MC penetrates it. The BR basically consists of superficial and deep heads, and the number of superficial heads is affected by branches of the MC. [ABSTRACT FROM AUTHOR]

Supernumerary or accessory heads of the biceps brachii are persistent muscular structures which can vary in number and location in the arm. Variations in other arm muscles, such as the coracobrachialis, can accompany supernumerary biceps brachii musculature in the upper limb. In this case report, we describe two rare muscular variants in a single adult male: a four-headed biceps brachii and the muscular elevator of the latissimus dorsi tendon. Additionally, accessory muscles of the brachialis and flexor digiti minimi brevis were identified in the upper limb. To our knowledge, the muscular variants identified here are considered rare, and their co-occurrence in a single upper limb has not been described previously. Also, a four-headed biceps brachii consisting of both the infero-medial and infero-lateral humeral heads has not been described previously to our knowledge. We postulate that the simultaneous appearance of several muscular variations may indicate a signaling disruption in embryogenesis during muscle patterning of the ventral limb bud. Knowledge of variant musculature in the arm is important for surgeons and clinicians as these muscles and their aberrant innervation patterns can complicate surgical procedures and may compress arteries and nerves producing upper limb pain and paresthesia. The clinical, functional and embryological implications of the upper limb variants are discussed. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis that the ratio of changes in muscle fascicle and tendon length that occurs with joint movement scales linearly with the ratio of the slack lengths of the muscle fascicles and tendons. We compared the contribution of muscle fascicles to passive muscle-tendon lengthening in muscles with relatively short and long fascicles. Fifteen healthy adults participated in the study. The medial gastrocnemius, tibialis anterior, and brachialis muscle-tendon units were passively lengthened by slowly rotating the ankle or elbow. Change in muscle fascicle length was measured with ultrasonography. Change in muscle-tendon length was calculated from estimated muscle moment arms. Change in tendon length was calculated by subtracting change in fascicle length from change in muscle-tendon length. The median (IQR) contribution of muscle fascicles to passive lengthening of the muscle-tendon unit, measured as the ratio of the change in fascicle length to the change in muscle-tendon unit length, was 0.39 (0.26-0.48) for the medial gastrocnemius, 0.51 (0.29-0.60) for tibialis anterior, and 0.65 (0.49-0.90) for brachialis. Brachialis muscle fascicles contributed to muscle-tendon unit lengthening significantly more than medial gastrocnemius muscle fascicles, but less than would be expected if the fascicle contribution scaled linearly with the ratio of muscle fascicle and tendon slack lengths. [ABSTRACT FROM AUTHOR]