An anomalous case of the flexor carpi radialis with an excessive muscular bundle

A variation of the flexor carpi radialis with an excessive muscular bundle was found on the right forearm of a Japanese male cadaver. The flexor carpi radialis had two heads, medial one arising from the medial epicondyle of the humerus, and the other, a variant excessive muscular bundle, arising from the bicipital aponeurosis deep at the medial edge of the tendon of biceps brachii. There was also a muscular slip between the pronator teres and lateral head of flexor carpi radialis. The insertion of the ending tendon of the flexor carpi radialis was also variant, which was not only inserted into the base of the second metacarpal bone, but into the proximal surface of the scaphoid and the tubercle of trapezium. The excessive muscular bundle might be a residual muscular slip which connects between the distal part of the biceps brachii and the initial part of the flexor carpi radialis during the early embryonic development.     

A case of median nerve descended on the surface of the pronator teres muscle

We report a case in which the left median nerve passed downwards on the surface of the pronator teres muscle in a 70-year-old male cadaver examined during student dissection practice in 2001 at Nihon University School of Medicine. In the present case, the lateral cord of the median nerve is formed of only the middle trunk, C7 and did not include upper trunk, C5, 6. The upper trunk continued the musculocutaneous nerve, but it did not participate in the median nerve. In the cubital fossa, the median nerve descended on the surface of the pronator teres muscle. The pronator teres muscle had an additional head which arose from the medial intermuscular septum. The brachial artery passed between the humeral head and the additional head. It suggested the relevance that the first branch from the median nerve to the forearm flexor muscle group is the union covered with the common ensheathing epineurium. It consisted of the pronator teres muscle branch, the flexor carpi radialis muscle branch, and the branch to the proximal belly of the muscle bundle of the flexor digitorum superficialis muscle (FDS) for the second digit (II-p), which also supplies the palmaris longus muscle. The branch to the FDS for the third to the fifth digit and the anterior interosseous nerve branch arose from the back of the median nerve following the first branch, and the two branches connected mutually. And the median nerve had a branch to the distal belly of the muscle bundle of the FDS for the second digit (II-d) in its more distal part.     

Anomalous lumbrical muscles arising from the deep surface of flexor digitorum superficialis muscles in man.

During anatomy practice in 1999 at Kumamoto University School of Medicine, the anomalous lumbrical muscles originating in the forearm were observed in both arms of a cadaver. These muscles, originating from the intermediate tendon of the deep layer of the flexor digitorum superficialis for the index finger (FDS-II), passed through the carpal tunnel to join the insertion of the first lumbrical muscle, and formed a muscle belly near the origin in the left and at the insertion in the right. The left anomalous muscle was innervated by a branch of the median nerve just proximal to the carpal tunnel. The right one received a twig from the nerve to the first lumbrical muscle. Tracing the nerve fibers by peeling off the epi- and perineurium clarified that the nerve fibers supplying the left anomalous muscle formed a common bundle with the fibers to the first lumbrical muscle. Therefore, these anomalous muscles are considered to be the accessory lumbrical muscles arising from the forearm. The three accessory lumbricalis, including one case reported by Yamada (1986), received branches which had slightly different origins from proximally (nerve to the distal belly of FDS-II) to distally (nerve to the first lumbricalis). Accordingly the position of the muscle belly shifted distally. The occurrence of these unusual accessory lumbrical muscles indicates that the distal belly of FDS-III and the first lumbricalis are derived from a common muscle origin and presents an important clue to the phylogenetic origin of the flexor digitorum superficialis.     

儿童旋前圆肌及指浅屈肌的肌内神经分布模式:为BTX-A的注射提供解剖定位

目的探索儿童旋前圆肌和指浅屈肌的肌内终末神经密集区的分布范围,为注射BTX-A治疗脑瘫患儿前臂肌痉挛提供解剖定位。方法使用改良的Sihler`s肌内神经染色法观察儿童旋前圆肌和指浅屈肌的肌内神经分支分布模式。结果旋前圆肌的神经入肌点有上、下两个,下部的神经支较粗大、分布更广,其肌内神经分支呈扫帚状,相邻各神经分支末端可见明显的"O"和"Y"型吻合,该肌的肌内终末神经密集区位于肌腹中部;指浅屈肌的神经入肌点有上、中、下3个,肌内终末神经密集区可分上、中、下3部,其中以中部最为密集,各终末神经间可见"Y"、"O"吻合。结论鉴于两肌的肌内终末神经密集区均位于肌腹中部,当脑瘫患儿旋前圆肌、指浅屈肌痉挛时,使用BTX-A治疗肌痉挛的最佳注射靶区应选择在肌腹中部。     

Low origin of the radial artery: a case study including a review of literature and proposal of an embryological explanation

A low origin of the radial artery is a rare anatomical variation, with the incidence estimated at 0.2 %. This report presents a previously unrecorded case of an unusual distal origin of the radial artery, co-occurring with a double recurrent radial artery. The radial artery arose under the pronator teres muscle, 76 mm below the intercondylar line of the humerus. After emerging from under the tendon of the pronator teres muscle, the radial artery took a typical course and terminated in the deep palmar arch. Additionally, the double radial recurrent artery branched directly off the brachial artery, near the level of the radial neck. A well-developed muscular branch of the first radial recurrent artery ran beneath the brachioradialis muscle and supplied the brachioradialis, extensor carpi radialis longus and brevis, as well as supinator muscles. The second (accessory) radial recurrent artery took origin from the posterior aspect of the brachial artery, ran deep to the distal tendon of the biceps brachii muscle and terminated by joining the articular network of elbow. According to recent theories, the plexiform appearance of the arteries at early stages of upper limb development allows for formation of alternative pathways of blood flow, which may give rise to variations in the definitive arterial pattern.     

骨间前神经综合征的局部解剖学研究

目的 搪塞骨间前神经综合征的解剖学基础。方法 解剖４８例（左右各２４侧）成人防固定标本。结果 骨间前神经主干邻近腱性结构有旋前圆肌纤维桥（５８．３％），尺骨头浅面腱膜（９３．７％），联合腱板（８３．３％）和指浅屈肌纤维弓（９１．２％），横过骨间前神经的拇长岂副头（６６．７％），及少 尺侧血管、小束肌肉或纤维结构。７７％骨间前神经干走在桡骨颈前方结论 骨间的神经主干邻近的腱性结构及距离桡骨颈近可能是     

骨间掌侧神经受压综合征的解剖学研究

在32具成人尸体的64侧上肢中解剖了骨间掌侧神经及其发出的肌支共510支,对其分支平面,分支数目,长度及其走行过程中的受压因素进行了观察和测量,旋前圆肌尺骨头的纤维弓,指浅屈肌腱弓,拇长屈肌的异常肌束和骨间掌侧血管的分支血管束是造成骨间掌侧神经受压的主要因素.     

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.     

Anatomical study of the motor branches of the median nerve to the forearm and guidelines for selective neurectomy

Purpose

The median nerve is responsible for the motor innervation of most of the muscles usually involved in upper limb spasticity. Selective neurectomy is one of the treatments utilized to reduce spasticity. The purpose of this study was to describe the variations of the motor branches of the median nerve in the forearm and draw recommendations for an appropriate planning of selective neurectomy.

Materials and methods

The median nerve was dissected in the forearm of 20 fresh cadaver upper limbs. Measurements included number, origin, division, and entry point of each motor branch into the muscles.

Results

One branch for the pronator teres was the most common pattern. In 9/20 cases, it arose as a common trunk with other branches. A single trunk innervated the flexor carpi radialis with a common origin with other branches in 17/20 cases. Two, three or four branches innervated the flexor digitorum superficialis, the first one frequently through a common trunk with other branches. They were very difficult to identify unless insertions of pronator teres and flexor digitorum superficialis were detached. The flexor digitorum profundus received one to five branches and flexor pollicis longus one to two branches from the anterior interosseous nerve.

Conclusions

There is no regular pattern of the motor branches of the median nerve in the forearm. Our findings differ in many points from the classical literature. Because of the frequency of common trunks for different muscles, we recommend the use of peroperative electrical stimulation. Selective neurotomy of flexor digitorum superficialis is technically difficult, because the entry point of some of their terminal branches occurs just below the arch and deep to the muscle belly.

     

Muscle variations and abnormal branching and course of the ulnar nerve in the forearm and hand

During dissection of the right forearm of a 27-year-old female cadaver, variations in the form and insertion of the palmaris longus muscle were observed. The tendon of the palmaris longus muscle, which demonstrated a centrally placed belly, split into two tendons: one inserted into the palmar aponeurosis and the other into the proximal part of the flexor retinaculum. Additionally, we found an accessory muscle extending between the flexor retinaculum and the tendon of the abductor digiti minimi muscle. This accessory muscle was located deep to the ulnar artery but superficial to the superficial and deep branches of the ulnar nerve at the wrist. Finally, an aberrant branch of the ulnar nerve was identified in the forearm; it traveled distally alongside the ulnar artery and in the palm demonstrated communications with common palmar digital nerves from the ulnar and the median nerves. No variations were observed in the contralateral upper limb.     

The thenar muscles

Examination of the thenar muscles in 30 anatomical preparations of the hand have shown that the abductor pollicis brevis, the opponens pollicis, and the adductor pollicis muscles are made up of several muscle bellies. The number and insertions of these bellies are varied. Both heads of flexor pollicis brevis do not originate from any particular muscle belly. The superficial head of this muscle always inserted into the head of the thumb metacarpal, either completely, or, some of the fibres of the dorsal aponeurosis of the thumb were attached to the base of the proximal phalanx. Furthermore the anatomy of the abductor pollicis brevis muscle was related to the presence of a tendinous slip from abductor pollicis longus. These variations could have an influence on proprioception in the thumb ray.     

Occurrence of three supernumerary muscles in adult human hand supporting recent developmental concept of muscle layers in the autopodium

The authors report on the simultaneous occurrence of short supernumerary muscles on the palmar and dorsal sides of an adult human hand. The supernumerary muscle on the palmar side of the hand took its origin from the tendon of the m. flexor digitorum superficialis in the distal third of the forearm, sharing its insertion with that of the m. lumbricalis primus, and taking its innervation from the n. medianus. With regard to its origin, the muscle may be a supernumerary belly of the m. flexor digitorum superficalis which failed to make its way to the forearm during development. With regard to its insertion, though, it can just as well represent a detached part of the m. lumbricalis primus whose tendon became attached to the m. flexor digitorum superficialis at the time of simultaneous development of those muscles of the hand. By their origin, insertion, innervation and position, the muscles on the dorsal side of the hand were identified, in part, as mm. interossei dorsales accessorii in the 2nd and 3rd intermetacarpal spaces which are constantly found in man as a developmental feature to become rudimentary in some cases later on, in part, as an anomalous m. extensor digitorum brevis of the 2nd and 3rd fingers.     

Morphological study, by teasing examination, of the communication from the musculocutaneous to median nerves

Nine specimens with communications from the musculocutaneous to the median nerves were investigated, by teasing examination, from their origins in the brachial plexus to their final destinations in nerve fibers. The nerve fibers of the communications were derived from the sixth and seventh cervical ventral rami of the spinal nerves. The distributions of the nerve fibers of the communications were divided into four types. In Type A, the nerve fibers reached the thenar muscles and the lateral digital nerves. In Type B, they reached the pronator teres or flexor carpi radialis muscles in addition to Type A. In Type C, they reached the anterior interosseous nerve area in addition to Type B. Finally in Type D, they also reached the distal muscle belly of the index of the flexor digitorum superficialis. It was revealed that there was a definite rule in the distribution of the nerve fibers in the communications from the musculocutaneous to median nerves. The area of the distributions was expanded in order from the thenar muscles to the flexor muscles of the forearm. The results in this study are useful for proper diagnosis and treatment of the peripheral nerve injuries involving the musculocutaneous and median nerves.     

An uncommon form of the rare extensor carpi radialis accessorius.

Two accessory muscles were found in the lateral compartment of the forearm while dissecting a 92-year-old female cadaver. One of these originated from the extensor carpi radialis brevis, became tendinous and travelled between the two radial extensor tendons. It inserted independently into the second metacarpal bone, and may be regarded as an extensor carpi radialis intermedius. The other accessory muscle originated from the extensor carpi radialis longus, passed superficially over the parent tendon and inserted into the abductor pollicis brevis. This variation appeared to be a rare extensor carpi radialis accessorius, an additional muscle, which usually arises from below the extensor carpi radialis longus and inserts into the first metacarpal bone. Various forms of the accessorius have been described previously, including one that inserts into the abductor pollicis brevis. The tendon of the accessory muscle described in this study passed through its own dorsal tunnel under the extensor retinaculum, making it an uncommon form of the rare accessorius.     

Innervation of the medial epicondylar muscles: an anatomic study in 50 cases

The median nerve is classically distributed to the medial epicondylar muscles by two branches (superior and inferior) for the pronator teres muscle, a common trunk for the flexor carpi radialis and palmaris longus muscles, and a branch for the flexor digitorum superficialis muscle. The 50 dissections were made by two workers on 30 upper limbs of formolized cadavers and 20 limbs from fresh-frozen cadavers. The innervation of the pronator teres m. was classical in only 26% of cases, and the “normal” pattern for the flexor carpi radialis and palmaris longus mm. was found in only 40% of cases. The innervation of the flexor digitorum superficialis m. was the least subject to variations, a single branch being observed in 68% of cases. We found a solitary medio-ulnar anastomosis of Martin-Gruber to the flexor carpi ulnaris muscle. This study confirmed the great variability of the branches of the median nerve at the elbow, and the importance of identifying them in surgical procedures for transposition of the medial epicondyle.     

Variation in the hypothenar muscles and its impact on ulnar tunnel syndrome

Compression of the ulnar nerve at Guyon’s canal can be caused not only by tumor-like structures, a fibrotic arch, a ganglion, lipoma, aneurysm or thrombosis but also by anomalous hypothenar muscles which are reviewed here. For the search of relevant papers, PubMed and crucial anatomical textbooks were consulted. The abductor digiti minimi is the most variable hypothenar muscle. It can possess one to three muscle bellies. Additional heads can arise from the flexor retinaculum, the palmaris longus tendon, the pronator quadratus tendon or the deep fascia of the palmar side of the forearm. Our own case of an aberrant abductor digiti minimi appearing like connective tissue and originating in the antebrachial fascia is included here. Hematoxylin and eosin staining revealed that macroscopically non-muscle-like tissue contained skeletal muscle tissue. The muscle itself resembled other described cases. In addition, at the flexor digiti minimi accessory heads with origin from the flexor retinaculum, the antebrachial fascia or the long flexor muscles of the forearm can be detected. By contrast, the opponens digiti minimi mostly lacks variations and is sometimes missing. In our opinion, this is due to its hidden location. However, in few cases an additional head can arise from the lower arm aponeurosis. Furthermore, additional (fourth) hypothenar muscles might be expressed. These muscles are characterized by origins in the forearm and insertions on the head of the 5th metacarpal bone or on the 5th proximal phalanx. It must be noted that accessory hypothenar muscles might look like connective tissue at first glance. Often their origin extends to the antebrachial fascia. This can be explained by the phylogenetic fact that all intrinsic muscles of the hand are derived from muscle masses that originated in the forearm. In the opinion of several authors, ulnar nerve compression mostly is evoked by hyper trophied variant hypothenar muscles due to overuse as for example in carpenters. In some rare cases, an aberrant hypothenar muscle can also evoke median nerve compression.     

Anomalous muscle belly to the index finger.

An unusual variation of flexor digitorum superficialis was observed during the cadaver dissection. The flexor digitorum superficialis (FDS) had a normal origin and insertion, except to the index finger, where a muscle belly replaced the tendon of FDS. The unusual muscle belly originated as a continuation of FDS tendon in the carpal tunnel and inserted normally into the middle phalanx. A branch of the median nerve innervated the anomalous muscle belly. The anomalous muscle belly described here should be considered in the aetiology of carpal tunnel syndrome.     

足底中间群肌和足背肌肌内神经整体分布模式及意义

目的 揭示足底中间群和足背肌的肌内神经整体分布模式，探讨其意义。 方法 取下12具经福尔马林固定的成人尸体足底中间群肌和足背肌，改良的Sihler’s染色法显示肌内神经整体分布模式。 结果 接受足底内侧神经支配的趾短屈肌、第1和第2蚓状肌的神经支，分别从肌的内侧深面和浅面入肌；接受足底外侧神经支配的足底方肌、第3和第4蚓状肌的神经支从肌止端走向起端；骨间足底肌和骨间背侧肌的神经支从肌起端走向止端。趾短伸肌和母短伸肌的神经支共干。蚓状肌、第1和第2骨间足底肌、第1骨间背侧、母短伸肌和趾短伸肌仅在肌腹中部形成1个肌内神经密集区；趾短屈肌、足底方肌、第3骨间足底肌以及第2~4骨间背侧肌有2个肌内神经密集区，位于肌腹两侧，这些肌可分为2个神经肌亚部。 结论 这些结果可为外科手术免于神经损伤、肌移植的选材匹配，以及注射肉毒毒素A阻滞这些肌的痉挛提供形态学指导。