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.     

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.

     

Biometry of the muscular branches of the median nerve to the forearm

The aim of this study was to determine the biometry of the muscular branches of the median nerve to the forearm in ten embalmed upper limbs. We measured the length of the forearm and the level of origin of each muscular branch of the median nerve to the forearm from the middle of a line between the medial and lateral epicondyles. The level of origin of each branch was then calculated as a percentage of the length of the forearm. Mean length of the forearm was 25 ± 2.36 cm (range: 22-29 cm). Although the levels of origin of the proximal and distal nerves to pronator teres, and of the nerves to palmaris longus, flexor carpi radialis and flexor digitorum superficialis, were quite variable (coefficient of variation: CV > 48.61%), the level of origin of the anterior interosseous nerve (CV = 31.24%) and its branches (nerves to flexor pollicis longus and flexor digitorum profundus, CV = 20.06%) was less variable. These results suggest that the anterior interosseous nerve of the forearm is probably the nerve to connect in muscular free transfers in order to restore flexion of the fingers after damage to the flexor tendons to the forearm. We observed Martin-Gruber communications in six out of ten dissections. Clin. Anat. 11:239–245, 1998. © 1998 Wiley-Liss, Inc.     

成人前臂前群肌的神经入肌点定位及意义

目的 准确定位成人前臂前群肌神经入肌点（NEP）的体表位置和深度。 方法 成人尸体12具,仰卧。紧贴皮肤连接肱骨外上髁和内上髁间的曲线为横向参考线(H),肱骨外上髁和桡骨茎突间的曲线为纵向参考线(L)。解剖暴露NEP,硫酸钡标记,螺旋CT扫描与三维重建。将NEP在体表上的投影点记为P点,P点通过NEP后投射至前臂后体表上的点为P'点。P点投射到H线与L线上的位置分别记为PH和PL。Syngo系统下确定PH和PL在H和L线上的位置及NEP的深度。 结果 旋前圆肌、桡侧腕屈肌、掌长肌、尺侧腕屈肌、指浅屈肌、拇长屈肌、指深屈肌（正中神经支）、指深屈肌（尺神经支）、旋前方肌NEP的PH分别位于H线上的58.08%、64.17%、75.14%、61.14%、62.26%、52.07%、50.81%、63.38%和51.37%处;PL分别位于L线上的9.79%、3.97%、16.37%、4.42%、17.88%、34.17%、30.27%、11.48%和75.32%处;穿刺深度分别位于PP'线的26.80%、25.06%、27.68%、28.13%、37.30%、39.85%、49.26%、70.86%和44.25% 处。以上数据均为平均值。 结论 这些NEP的体表穿刺位置与深度的界定可为提高前臂前群肌痉挛肌外神经溶解术靶点阻滞的效率、手术切断神经肌支治疗肌痉挛的微创切口设计、作为供肌的功能评估、以及肌移植术中对神经的保护等提供形态学指导。     

A case of an accessory palmaris longus muscle and a duplicate palmaris longus muscle with special reference to their nerve supply--morphologic significance of a common innervation trunk

During a dissection of the forearm and hand, a duplicate palmaris longus muscle with an accessory palmaris longus muscle was observed on the right side of a 73-year-old Japanese male cadaver. Duplications of the palmaris longus muscle have been reported by many authors. Humphry (1872) suggested the presence of radial, intermediate, and ulnar sectors in the superficial layers of the forearm flexor muscular angulus, based on a comparison of fore- and hind limbs and comparative anatomical theory. The palmaris longus muscle usually differentiates from the intermediate sector but differentiation from the other two sectors may also be possible. Some authors have asserted that a common innervation trunk is critical for determining an ontogenetic relation between the muscles (Fuchino, 1960; Honma, 1980; Yamada, 1986). We examined the nerve supply in addition to scrutinize these anomalous palmaris longus muscles. In our case, the ramification of the innervating nerves was specific. The branches to the second palmaris longus muscle and the flexor carpi radialis arose as a common trunk from the median nerve. The branches to the first palmaris longus muscle and the accessory palmaris longus muscle originated as another common trunk from the median nerve. From these observations, we speculated that the second palmaris longus muscle has differentiated from the flexor carpi radialis, while the accessory palmaris longus muscle has differentiated from the first palmaris longus muscle, based on Humphry's suggestion.     

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。     

The proximal origins of the flexor–pronator muscles and their role in the dynamic stabilization of the elbow joint: an anatomical study

Purpose

The purpose of this study was to anatomically investigate the proximal origin of flexor–pronator muscles (FPMs) and clarify their contribution to dynamic stabilization of the elbow joint during valgus stress.

Methods

52 elbows from 26 donated formalin-fixed cadavers were examined. The pronator teres muscle (PT), flexor carpi radialis muscle (FCR), palmaris longus muscle (PL), flexor digitorum superficialis muscle (FDS), and flexor carpi ulnaris muscle (FCU) were identified, and their proximal origin and relationship to the anterior bundle of the medial ulna collateral ligament (AOL) were macroscopically and histologically investigated.

Results

The PT, FCR, PL, and FDS converged and formed a common tendon at their proximal origin (the anterior common tendon: ACT). The ACT was attached to the medial epicondyle and the joint capsule, just anterior and parallel to the AOL. The histological morphology of the ACT was quite similar to that of the AOL. The ulnar head of the PT was observed in 48 of 52 elbows (92.3 %), just behind the humeral head of PT. It mainly originated from the anterior edge of the sublime tubercle, while the upper part of ulnar head transitioned directly into the thickened joint capsule just anterior to the AOL.

Conclusion

The proximal attachment of the FPMs had a characteristic morphology. According to our results, the ACT and PT might assist the AOL by sharing static and dynamic traction forces applied to the medial elbow joint.     

Anomalous flexor digiti minimi brevis in Guyon's canal

In an adult male cadaver, the flexor digiti minimi brevis, a muscle of the hypothenar eminence, was found to arise from the superficial transverse septum (between the superficially placed flexor carpi ulnaris, palmaris longus, and flexor carpi radialis muscles, and the deeply placed flexor digitorum superficialis muscle) in the distal fourth of the flexor aspect of the left forearm. The muscle exhibited two strata of muscle fibers at its origin. The superficial stratum was a thin layer of transversely running fibers confined to the forearm, which has not been previously reported. The deep stratum, a thick layer of longitudinally running fibers, formed the bulk of the muscle. It traversed Guyon's canal superficial to the ulnar nerve and vessels to reach the hypothenar eminence. Its course through Guyon's canal could be a cause for ulnar tunnel syndrome. The ulnar nerve trunk innervated not only the anomalous flexor digiti minimi brevis muscle, but also abductor digiti minimi and palmaris brevis. This may be due to the common phylogeny of these three muscles from the same muscle mass.     

A Case of the Bilateral Duplicate Palmaris Longus Muscles Coupled with the Palmaris Profundus Muscle

The palmaris longus muscle is one of the most variable muscles in human anatomy. During a routine anatomical dissection for medical students at Tottori University, we found duplicate palmaris longus muscles in the bilateral forearms together with the palmaris profundus muscle in the right forearm. The bilateral aberrant palmaris longus muscles were observed at the ulnar side of the palmaris longus muscle and their distal tendons were attached to the flexor retinaculum. The palmaris profundus muscle found in the right forearm was located at the radial side of the flexor digitorum superficialis muscle. The proximal tendon was originated from the anterior surface in the middle of the radius, while the distal tendon coursed radial to the median nerve through the carpal tunnel, finally inserting into the distal part of the flexor retinaculum. Both the palmaris longus and aberrant palmaris longus muscles were innervated by the median nerve. The palmaris profundus muscle was presumably supplied by the median nerve.     

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.     

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.     

Architectural properties of the neuromuscular compartments in selected forearm skeletal muscles

The purposes f this study were to (i) explore the possibility of splitting the selected forearm muscles into separate compartments in human subjects; (ii) quantify the architectural properties of each neuromuscular compartment; and (iii) discuss the implication of these properties in split tendon transfer procedures. Twenty upper limbs from 10 fresh human cadavers were used in this study. Ten limbs of five cadavers were used for intramuscular nerve study by modified Sihler''s staining technique, which confirmed the neuromuscular compartments. The other 10 limbs were included for architectural analysis of neuromuscular compartments. The architectural features of the compartments including muscle weight, muscle length, fiber length, pennation angle, and sarcomere length were determined. Physiological cross-sectional area and fiber length/muscle length ratio were calculated. Five of the selected forearm muscles were ideal candidates for splitting, including flexor carpi ulnaris, flexor carpi radials, extensor carpi radialis brevis, extensor carpi ulnaris and pronator teres. The humeral head of pronator teres contained the longest fiber length (6.23 ± 0.31 cm), and the radial compartment of extensor carpi ulnaris contained the shortest (2.90 ± 0.28 cm). The ulnar compartment of flexor carpi ulnaris had the largest physiological cross-sectional area (5.17 ± 0.59 cm²), and the ulnar head of pronator teres had the smallest (0.67 ± 0.06 cm²). Fiber length/muscle length ratios of the neuromuscular compartments were relatively low (average 0.27 ± 0.09, range 0.18–0.39) except for the ulnar head of pronator teres, which had the highest one (0.72 ± 0.05). Using modified Sihler''s technique, this research demonstrated that each compartment of these selected forearm muscles has its own neurovascular supply after being split along its central tendon. Data of the architectural properties of each neuromuscular compartment provide insight into the ‘design’ of their functional capability. In addition to improving our understanding of muscle anatomy and function, elucidation of forearm neuromuscular compartments architecture may ultimately provide information useful for selection of muscle subdivisions used in tendon transfer.     

Epifascial accessory palmaris longus muscle

In hand reconstructive surgery the palmaris longus muscle is one of the most utilized donor site for tendon reconstruction procedures. However, its anatomic position is variable and anatomic variations may be responsible for median nerve compression. We report the case of a 40-year-old, right-handed woman, who presented with numbness and paresthesias in the palm and in the flexor aspect of the first, second, and third fingers of her right hand for the preceding 5 months, coinciding with increase of office work (typing). The clinical examination and radiological investigations (ultrasound and magnetic resonance) revealed a subcutaneous mass (15 mm x 2.3 mm x 6 cm), with a lenticular shape and definite edges at the level of the volar aspect of the distal third of the forearm. The fine-needle aspiration biopsy revealed the presence of striated muscle fibers. During surgery, a muscle belly was found in the epifascial plane. This muscle originated from subcutaneous septa in the middle forearm and inserted on to the superficial palmar aponeurosis with fine short tendon fibers. Exposure of the antebrachial fascia did not reveal any area of weakness or muscle herniation. The palmaris longus tendon, flexor digitorum superficialis tendons, and flexor carpi radialis tendon showed usual topography under the antebrachial fascia. The accessory muscle was excised and histology revealed unremarkable striated muscle fibers, limited by a thin connective sheath. The presence of an accessory palmaris longus (APL) located in the epifascial plane could be ascribed to an unusual migration of myoblasts during the morphogenesis. Although extremely rare, APL is worth bearing in mind as a possible cause of median nerve compression and etiology of a volar mass in the distal forearm.     

The accessory heads of flexor pollicis longus and flexor digitorum profundus: Incidence and morphology

Kiloh-Nevin syndrome caused by compressive neuropathy of the anterior interosseous nerve in the forearm is believed to occur because of its compression by the accessory head of flexor pollicis longus (FPLah). Gantzer described two accessory muscles, the more frequent is the FPLah and the less frequently observed is the flexor digitorum profundus accessory head (FDPah). Many studies have reported the prevalence, origin, insertion, nerve supply, and relations of these accessory muscles, most of them focusing on the FPLah. This study was designed to investigate the prevalence, morphology, relation to median and anterior interosseous nerve, and also the coexistence of both the accessory heads. A total of 126 upper limbs of the embalmed cadavers were examined in this study. Fifty-eight limbs (46.03%) showed the presence of the FPLah and 18 limbs (14.28%) had the FDPah. The most common origin of both the accessory muscle bellies was from the under surface of the flexor digitorum superficialis. The FPLah inserted into the FPL muscle at varying levels with 80% inserting into the proximal third of FPL, whereas the FDPah in all cases ended near the level of the wrist joining with one or more tendons of the FDP. Clinical implication of the variation is discussed.     

Topographical anatomy of the radial nerve and its muscular branches related to surface landmarks

Understanding of the anatomy of the radial nerve and its branches is vital to the treatment of humeral fracture or the restoration of upper extremity function. In this study, we dissected 40 upper extremities from adult cadavers to locate the course of the radial nerve and the origins and insertions of the branches of the radial nerve using surface landmarks. The radial nerve reached and left the radial groove and pierced the lateral intermuscular septum, at the levels of 46.7, 60.5, and 66.8% from the acromion to the transepicondylar line, respectively. Branches to the long head of the triceps brachii originated in the axilla, and branches to the medial and lateral heads originated in the axilla or in the arm. The muscular attachments to the long, medial, and lateral heads were on average 34.0 mm proximal, 16.4 mm distal, and 19.3 mm proximal to the level of inferior end of the deltoid muscle, respectively. The radial nerve innervated 65.0% of the brachialis muscles. Branches to the brachioradialis and those to the extensor carpi radialis longus arose from the radial nerve above the transepicondylar line. Branches to the extensor carpi radialis brevis usually arose from the deep branch of radial nerve (67.5%); however, in some cases, branches to the extensor carpi radialis brevis arose from either the radial nerve (20.0%) or the superficial branch of the radial nerve (12.5%). Using these data, the course of the radial nerve can be estimated by observing the surface of the arm. Clin. Anat. 26:862–869, 2013. © 2012 Wiley Periodicals, Inc.     

An accessory belly of the abductor digiti minimi muscle: a case report and embryologic aspects

Accessory fasciculi of the hypothenar muscles have been involved in vascular and nerve compressions. During a routine dissection an accessory belly of the abductor digiti minimi muscle arising from the tendon of the palmaris longus muscle was found in the lower third of the forearm. The accessory fasciculus ran through Guyon’s canal enclosing the ulnar nerve and vessels. It was attached by means of two tendons where the fibres of the abductor digiti minimi muscle ended in a single pennate form. This anatomic variation was associated with a marked reduction of the caliber of the fourth tendon of the flexor digitorum superficialis muscle and a split of the median nerve. The nerve supply arose from the ulnar nerve. A fibrous band originating from this accessory muscular belly was found covering the median nerve. Based on the development of muscles and fibrous structures within the hand and forearm, as well as on our results, we consider the present anomalies as an unusual persistence of an undifferentiated group of mesenchymal cells. These belong to the superficial muscular anlagen layer of the hand, just between the flexor digitorum superficialis muscle blastema (which has the capacity of migration) and that for the abductor digiti minimi muscle.     

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.     

掌长肌内神经血管的解剖学观察及其临床意义

目的：观察掌长肌肌内神经血管解剖分布,探讨该肌肉能否被分割为若干个功能单位,以提供新的功能性骨骼肌游离移植供区.方法：解剖10具10%福尔马林固定的成人尸体共20侧掌长肌,观察其肌外神经血管的分布形式.10具新鲜成人尸体标本共20侧掌长肌,一侧的掌长肌完整剥离后用Sihler＇s染色法行肌内神经的染色,另一侧掌长肌用30%硫酸钡、乳胶混悬液血管灌注并行X线钼靶摄片.而后对照观察神经、血管在肌内分布及其关系.结果：掌长肌血供多为尺侧返动脉和尺动脉肌支,4侧出现肱动脉肌支.其神经支配来自正中神经发出的神经支.该支在进入肌肉前多为1支,有动脉伴行,构成神经血管束.尺侧返动脉肌支和正中神经分支在肌内的分布区域大致吻合.结论：根据掌长肌肌内神经血管在肌内分布的不同情况,可将其分为一个近端和两个远端的3个功能单位,供节段性游离肌肉移植.     

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