Unusual variation of a third head of the biceps brachii muscle

A human cadaver was studied which presented a biceps brachii with three heads of origin in the left arm. The third or humeral head presented an unique area of insertion into the bicipital aponeurosis (lacertus fibrosus).     

Triceps brachii muscle demonstrating a fourth head

Variations of the triceps brachii muscle are apparently rare. We report an additional attachment site of the medial head of the triceps brachii found on the left side of a male cadaver. This head originated from the posterior aspect of the surgical neck of the humerus. Clinicians diagnosing or treating patients with weakness or pain of the posterior arm should consider anomalous muscles in this region that may result in neurovascular compression.     

Supernumerary humeral heads of the biceps brachii muscle revisited

Supernumerary humeral heads of the biceps brachii muscle were found in 27 (15.4%) of 175 cadavers. They were bilateral in five cadavers and unilateral in 22 (8 left, 14 right), giving a total of 32 examples in 350 arms (9.1%). Depending on their origin and location, the supernumerary heads were classified as superior, infero-medial, and infero-lateral humeral heads. Previous studies were reviewed using this classification. The infero-medial humeral head was observed in 31 of 350 (9%) arms and was therefore the most common variation. The superior humeral head was observed in five (1.5%). The infero-lateral humeral head was the least common variation, observed only in one (0.3%) of 350 arms. A biceps brachii with three heads was observed in 27 of 350 (7.7%) arms and with four heads in five (1.4%) arms.     

Muscle architecture of biceps brachii, triceps brachii and supraspinatus in the horse

Three muscles from the proximal equine forelimb were dissected in order to investigate their potential to contribute to proximal limb mechanics. Muscle mass, fibre length, tendon mass and tendon length were measured from biceps brachii, triceps brachii, supraspinatus and lacertus fibrosus (biceps lateral head mass 171-343.4 g and fibre length 0.5-0.8 cm; biceps medial head mass 283-500 g and fibre length 2.2-4 cm; biceps tendon mass 121.8-260 g and tendon length 35-44 cm; triceps long head mass 3200-6663 g and fibre length 19-26.3 cm; triceps lateral head mass 513.8-1240 g and fibre length 17.5-24 cm; triceps medial head mass 85.2-270.6 g and fibre length 9-16.8 cm; supraspinatus mass 793-1546 g and fibre length 4.7-12.4 cm; lacertus fibrosus mass 4.6-12.4 g and length 10-16 cm). Physiological cross-sectional area (PCSA) and maximum isometric force were estimated for each muscle, and moment arm measurements were taken at the shoulder and elbow joints. Biceps has a greater isometric force-generating capacity than supraspinatus. It also appears to have a larger shoulder moment arm, so could therefore have the potential to make a greater contribution to the shoulder moment than supraspinatus. Supraspinatus is likely to function primarily as a shoulder stabilizer rather than a shoulder extensor. Biceps also functions as an elbow flexor and data here indicate that it has a greater PCSA and isometric force-generating capacity than its antagonist triceps brachii. Calculation of tendon forces showed that the biceps tendon can withstand much greater forces than lacertus fibrosus. This study will enable further investigation into the interaction between energy recycling in elastic tissues and the generation and absorption of mechanical work by adjacent muscle groups in the equine forelimb.     

Role of the long head of the biceps brachii muscle in axial humeral rotation control

This anatomical and biomechanical study focuses on the specific influence of the long head of biceps brachii muscle in controlling axial humeral rotation. The tendon of the long head of the biceps brachii (biceps tendon) is shown to either facilitate or restrict axial humeral rotation. Its effect on axial humeral rotation is strongly related to firstly the amount of biceps tendon load, secondly glenohumeral scapular plane elevation, and thirdly the rotatory position of the humerus. At 0° glenohumeral elevation, biceps tendon load caused an increase of internal humeral rotation, from 0° at 2.25 N biceps tendon load to 23° at 82.25 N. Under 45° glenohumeral elevation, biceps tendon load can restrict and facilitate as well internal and external axial humeral rotation, increasing the rotatory range of motion. Above 45° glenohumeral elevation biceps tendon load restricts internal and external axial humeral rotation, increasing actively joint stability by increasing torsional rigidity. These findings on the function of the biceps tendon could have consequences for the clinical interpretation. In the elevated arm position, extreme rotation loads the long head of the biceps tendon and may turn out to biceps or bicepslabrum complex injuries.     

Bilateral four-headed biceps brachii muscles: The median nerve and brachial artery passing through a tunnel formed by a muscle slip from the accessory head

Bilateral four-headed biceps brachii muscles were observed in the dissected cadaver of a 95-year-old Japanese woman. The third head on both sides originated from the humerus at the insertion of the coracobrachialis and inserted into the distal part of the biceps brachii and the proximal part of the common biceps tendon on the ipsilateral side. The fourth head on both sides arose from a thin fibrous origin from the intertubercular sulcus and the insertion of the pectoralis major, and inserted into the confluence of the biceps brachii and the third head. This anomaly is relatively rare. Moreover, the left third head gave off a muscle slip into the posterior fascia of the pronator teres, forming a tunnel. The median nerve and the brachial artery passed through the tunnel, where the nerve and artery seemed to be compressed. The possible production of clinical symptoms, given the anatomy, is discussed. Clin. Anat. 11:209–212, 1998. © 1998 Wiley-Liss, Inc.     

Differential activation of regions within the biceps brachii muscle during fatigue

Aim: To examine the occurrence of repeated differential activation between the heads of the biceps brachii muscle and its relation to fatigue prevention during a submaximal contraction. Methods: Thirty‐nine subjects carried out an isometric contraction of elbow flexion at 25% of maximal voluntary contraction (MVC) until exhaustion. A grid of 13 by 10 electrodes was used to record surface electromyographic signals from both heads of the biceps brachii. The root‐mean‐square of signals recorded from electrodes located medially and laterally was used to analyse activation differences. Differential activation was defined as periods of 33% different activation level between the two heads of the biceps brachii muscle. Results: Differential muscle activation was demonstrated in 30 of 33 subjects with appropriate data quality. The frequency of differential activation increased from 4.9 to 6.6 min^?1 at the end of the contractions with no change in duration of the differential activations (about 1.4 s). Moreover, the frequency of differential activation was, in general, negatively correlated with time to exhaustion. Conclusion: The observed differential activation between the heads of the biceps brachii can be explained by an uneven distribution of synaptic input to the motor neurone pool. The findings of this study indicate that differential activation of regions within a muscle does not prevent fatigue at a contraction level of 25% of MVC.     

Four-headed biceps and triceps brachii muscles,with neurovascular variation

Anatomical variations of the biceps brachii and triceps brachii have been described by various authors, but the occurrence of four-headed biceps brachii and triceps brachii in an ipsilateral arm is rare and has not been reported before in the literature. During routine cadaveric dissection in the department of anatomy, Kasturba Medical College, Mangalore, India, various unusual variants were noted in the left arm of a cadaver of a 67-year-old man. The variants include a four-headed biceps, a four-headed triceps, communication between the musculocutaneous and median nerves, and a high origin of deep brachial artery from the axillary artery. The occurrence of these anomalies and the clinical and morphological significance are discussed.     

Unusual formation of the median nerve associated with the third head of biceps brachii

Unilateral variations in the formation of the median nerve, with the presence of the third head of the biceps brachii entrapping the nerve are very rare. These variations were observed on the right side, of a 30‐year‐old male cadaver during routine dissection at the Department of Human Anatomy, University of Nairobi. The median nerve was formed by the union of three contributions; two from the lateral cord and one from the medial cord. An additional head of the biceps brachii looped over the formed median nerve. On the left side, the median nerve was formed classically by single contributions from the medial and the lateral cords. These variations are clinically important because symptoms of high median nerve compression arising from similar formations are often confused with more common causes such as radiculopathy and carpal tunnel syndrome. Clin. Anat. 25:961–962, 2012. © 2012 Wiley Periodicals, Inc.     

Two bellies of the coracobrachialis muscle associated with a third head of the biceps brachii muscle.

Reports that describe the abnormalities and complexities of the anatomy of the arm are important with regard to surgical approaches. This case study reports a combined abnormal form of the coracobrachialis and biceps brachii muscles of the left arm of an adult male cadaver that was detected during the educational gross anatomy dissections of embalmed cadavers. The coracobrachialis muscle demonstrated two bellies which formed shortly inferior to its origin from the coracoid process of the scapula. One belly inserted into the middle of the antero-medial surface of the humerus, whereas the other belly inserted into the medial head of the triceps brachii muscle. The musculocutaneous nerve passed between the two bellies, giving a separate branch to each. We suggest that the two bellies of the coracobrachialis muscle may represent the incompletely fused short heads of the ancestral muscle. The biceps brachii muscle showed a third head, which originated mainly from the antero-medial surface of the humerus and partially from an aponeurosis belonging to the medial head of the triceps brachii muscle. These observations were confined to the left upper limb and were not accompanied by any other abnormality.     

A rare case of a four-headed biceps brachii muscle with a double piercing by the musculocutaneous nerve

A rare case of a four-headed biceps brachii muscle associated with a double piercing of one of the supernumerary heads by the musculocutaneous nerve was observed in the right arm of an 87-year-old female cadaver. One of the supernumerary heads of the biceps brachii originated from the humerus, in the area between the lesser tubercle and the coracobrachialis and brachialis muscles and joined the long head at the level where the latter joined the short head. The second supernumerary head originated from the humerus at the point where the coracobrachialis muscle inserted and joined the biceps brachii tendon and its bicipital aponeurosis at the inferior third of the arm. The musculocutaneous nerve originated from the lateral cord of the brachial plexus and, after piercing the coracobrachialis muscle, coursed along one of the supernumerary heads of the biceps brachii muscle before piercing it from deep to superficial and then again from superficial to deep. It then adopted its normal position between the biceps brachii and brachialis muscles before exiting in the lateral aspect of the arm and continuing as the lateral cutaneous nerve of the forearm.

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Un cas rare de muscle biceps brachial à 4 chefs accompagné d'une double perforation par le nerf musculo-cutané

Résumé Un cas rare associant un muscle biceps brachial à 4 chefs à une double perforation de l'un des chefs surnuméraires par le nerf musculo-cutané a été observé sur le bras droit du cadavre d'une femme de 87 ans. Un des chefs surnuméraires du muscle biceps brachial naissait de l'humérus, d'une zone située entre le tubercule mineur et les muscles coraco-brachial et brachial et rejoignait le chef long au niveau où celui-ci rejoignait le chef court. Le second chef surnuméraire naissait de l'humérus à l'endroit où le muscle coraco-brachial s'insèrait et il rejoignait le muscle biceps brachial et l'aponévrose bicipitale au tiers inférieur du bras. Le nerf musculo-cutané naissait du faisceau latéral du plexus brachial et, après avoir percé le muscle coraco-brachial, cheminait le long d'un des chefs surnuméraires du muscle biceps brachial avant de le traverser, de la profondeur à la surface, puis à nouveau de la surface à la profondeur. Il adoptait alors un trajet normal, entre les muscles biceps brachial et brachial, avant de sortir dans le sillon bicipital latéral, se poursuivant sous forme du nerf cutané latéral de l'avant-bras.

     

Dissection of a rare accessory muscle of the leg: the tensor fasciae suralis muscle

We report a case of the rare tensor fascia suralis muscle. This muscle was found during the routine dissection of the lower extremity in an adult male cadaver. No other anomalies were noted in this specimen. The innervation of this muscle was via the tibial component of the sciatic nerve. Although seemingly rare, the tensor fascia suralis muscle may be considered by the clinician in the differential diagnosis of masses over the posterior lower extremity.     

An anomalous accessory flexor digiti minimi profundus muscle: A case study

A well-developed anomalous muscle within the forearm flexor compartment was discovered during a routine cadaveric dissection. The identified muscle originated from the intercompartmental septum on the medial side of the forearm just proximal to the wrist joint and inserted on the proximal phalanx of the fifth digit. When stressed, the tendon of the muscle produced flexion of the metacarpophalangeal joint of the fifth digit. Contiguous muscles, including the flexor digitorum profundus, displayed normal morphology. The muscle appeared to be an accessory belly of flexor digitorum profundus. The combination of an accessory flexor digitorum profundus muscle belly acting on the metacarpophalangeal joint of the little finger has not been previously reported. Based on its origin, insertion, and action we have named this variant accessory flexor digiti minimi profundus. This muscular variant could have clinical relevance, possibly affecting ulnar nerve function and circulation in the hand. Clin. Anat. 11:55–59, 1998. © 1998 Wiley-Liss, Inc.     

肱骨结节间沟形态在肱二头肌长头肌腱损伤中的作用

目的　提供详尽的肱骨结节间沟形态资料。方法　使用不同地区肱骨 80只 ,将结节间沟分为近侧水平段和远侧垂直段 ,用量角器和卡尺测量二段的长度及其移行处的角度 ;结节间沟的深度和宽度分五个部位测量 ;观察结节间沟的变异和异常。结果　结节间沟近侧段和远侧段的长度及移行处角度分别为 9.4mm、2 9.7mm和 119.9° ;总长度、深度和宽度分别为 39.2mm、0 .7mm和 2 .6mm ;结节上嵴出现率为 11.2 % ,内、外侧骨刺 16 .2 % ,钙化 45 %。结论　肱骨结节间沟的局部形态与肱二头肌长头腱损伤关系密切。