Motor branching patterns of the ulnar nerve in the forearms of fetal cadavers

Purpose

The aim of this study was to investigate the branches of the ulnar nerve given to forearm muscles [flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP)] and typing of ulnar nerve according to distribution of these branches to the muscles.

Methods

From the collection of Anatomy Department Laboratory, Faculty of Medicine, Suleyman Demirel University, 116 upper limbs of fetuses showing no external anomaly and aging between 12th and 40th weeks of pregnancy, were included in this study for anatomical dissection. Parameters about the branching of fetal ulnar nerve were set as follows: branch/branches to FCU muscle and branch/branches to FDP muscle.

Results

Ulnar nerve was typed according to number, sequence, and distribution of motor branches of ulnar nerve. As a result of this typing, eight type branching model of ulnar nerve was confirmed.

Conclusions

Our study is critically important for implementing successful surgical interventions and minimizing complications especially in ulnar nerve and forearm muscles surgery also in nerve replacement on this area.     

Anomalies of the flexor carpi ulnaris: Clinical case report and cadaveric study

Flexor carpi ulnaris (FCU) is an ever‐present muscle of the anterior flexor compartment of the forearm. Variations of FCU are uncommon, with additional slips or heads of muscles described, and only one reported case of an accessory muscle. We describe a unique clinical case report in which an accessory FCU was identified and describe the findings of 5,000 cadaveric dissections of the forearm, performed as part of an ongoing institutional study of anatomical variations. An aberrant accessory forearm flexor muscle was identified incidentally at the wrist during surgery for an anterior interosseous to ulnar nerve transfer for management of ulnar nerve palsy. This muscle was seen running superficial to the ulnar nerve and radial to the FCU proper, arising from the common flexor origin and inserting at the triquetral carpal bone. This was therefore suitably acknowledged as an “accessory FCU”. The anomaly was identified as bilateral using ultrasound imaging, and was found to be anomalously innervated by the median nerve with nerve conduction studies. A subsequent review of 5,000 cadaveric dissections of the forearm did not identify any such variations related to FCU, despite identifying a range of variations of the other forearm flexor musculature. While the scarcity of this anomaly is thus highlighted, consideration of an accessory FCU, and its aberrant innervation is important in a range of surgical approaches. Clin. Anat. 23:427–430, 2010. © 2010 Wiley‐Liss, Inc.     

Intermuscular aponeuroses between the flexor muscles of the forearm and their relationships with the ulnar nerve

Introduction

The aim of this study was to clarify the morphological characteristics of the intermuscular aponeurosis between the flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS; IMAS), and that between the FCU and flexor digitorum profundus (FDP; IMAP), and their topographic relationships with the ulnar nerve.

Materials and methods

Fifty limbs of 38 adult cadavers were studied.

Results

The IMAS extended along the deep surface of the FCU adjoining the FDS, having the appearance of a ladder, giving off “steps” that decreased in width from superficial to deep around the middle of the forearm. Its proximal part divided into two bands connected by a thin membrane, and was attached to the medial epicondyle and the tubercle (the most medial prominent part of the coronoid process of the ulna), respectively. The IMAP extended deep between the FCU and FDP from the antebrachial fascia, and its distal end was located on the posterior border of the FCU. The IMAP became broader toward its proximal part, and its proximal end was attached anterior and posterior to the tubercle and the olecranon, respectively. The ulnar nerve passed posterior to the medial epicondyle and then medial to the tubercle, and was crossed by the deep border of the IMAS at 58.3 ± 14.1 mm below the medial epicondyle.

Conclusion

The deep border of the IMAS and aberrant tendinous structure passing across the ulnar nerve, or the parts of the IMAS and IMAP passing posterior to the ulnar nerve are potential causes of ulnar nerve compression.

     

Martin-Gruber anastomosis revisited

Based on a study of 70 human cadavers (31 male, 39 female) and on cases described previously, we propose a new classification of the Martin-Gruber anastomosis, a neural connection between the median and ulnar nerves in the forearm. The anastomosis was found in 16 (22.9%) cadavers, being bilateral in three (18.7%) and unilateral in 13 (81.3%), five right and eight left. It occurred in eight (25.8%) of the 31 male cadavers and in eight (20.5%) of the 39 females. Therefore, the anastomosis was found in 19 (13.6%) of the 140 forearms. In Pattern I (89.5%) the anastomosis was made by only one branch, whereas in Pattern II (10.5%) it was made by two. The individual branches were classified as Types a, b, and c based on the nature of their origin from the median nerve. Type a (47.3%) arose from the branch to the superficial forearm flexor muscles, Type b (10.6%) from the common trunk, and Type c (31.6%) from the anterior interosseous nerve. Pattern II was a duplication of Type c (10.5%). The anastomotic branch took an oblique or arched course before joining the ulnar nerve, undivided in 15 cases, but divided into two branches in four cases. The anastomosis passed in front of the ulnar artery in four cases, behind it in six, and in nine cases it was related to the anterior ulnar recurrent artery.     

An unusual termination of the ulnar nerve in the palm.

During the dissection of the left forearm and hand of a 57-year old male cadaver fixed in 10% formalin, it has been noted that the medial proper palmar digital nerve to the little finger arose from the dorsal branch of the ulnar nerve, instead of the superficial branch of the same nerve. The dorsal branch, given off by the ulnar nerve in the forearm, coursed distally and dorsally deep to the flexor carpi ulnaris muscle. Some 2 cm proximal to the pisiform, it pierced the deep fascia on the posteromedial side of the muscle to become superficial. At this point, one of the three branches given off travelled distally on the palmar-ulnar side of the hand to the skin of the little finger. There were connections between this branch and the branches of the superficial branch of the ulnar nerve which innervated the skin of the hypothenar eminence. Further, another branch of the superficial branch of the ulnar nerve passed under the fibrous arch of the flexor digiti minimi brevis muscle origin and the opponens digiti minimi muscle to re-unite with its parent nerve.     

尺动脉腕背支升支皮瓣的应用解剖学研究

目的　为临床应用尺动脉腕背支升支皮瓣修复手部创面 ,提高治疗效果提供解剖学基础。方法　用新鲜成人男性上肢标本 1 6侧 ,采用显微解剖学技术 ,对尺动脉腕背支升支的起始、走行、分支及分布进行解剖学观察和测量。结果　尺动脉腕背支起始于尺动脉的尺侧 ,距豌豆骨上方 4 2 .6 0± 8.2 0mm ,起始处外径1 .4 6± 0 .32mm ,长 1 1 .4 6± 8.2 0mm。尺动脉腕背支与尺神经手背支伴行 ,穿过尺侧腕屈肌腱的深面 ,从掌侧向后内侧斜行 ,两者成锐角 ,平均 38.6 0± 8.2 0°,行至 1 1 .4 6mm处分为升支与降支。升支穿深筋膜进入皮下组织 ,沿前臂内侧缘上行 1 2 2 .4 0± 1 3.80mm处再分为细小分支 ,升支起始部的外径为 0 .6 2± 0 .2 8mm。结论　尺动脉腕背支升支皮瓣是以尺动脉腕背支升支为蒂 ,可在前臂尺侧设计大面积岛状皮瓣 ,通过转位修复腕部和手部创伤及挛缩瘢痕切除术后的创面 ,不牺牲前臂主要血管 ,手术操作易于掌握     

Applied anatomy of the superficial branch of the radial nerve

The superficial branch of the radial nerve (SBRN) is highly vulnerable to trauma and iatrogenic injury. This study aimed to map the course of the SBRN in the context of surgical approaches and identify a safe area of incision for de Quervain's tenosynovitis. Twenty-five forearms were dissected. The SBRN emerged from under brachioradialis by a mean of 8.31 cm proximal to the radial styloid (RS), and remained radial to the dorsal tubercle of the radius by a mean of 1.49 cm. The nerve divided into a median of four branches. The first branch arose a mean of 4.92 cm proximal to the RS, traveling 0.49 cm radial to the first compartment of the extensor retinaculum, while the main nerve remained ulnar to it by 0.64 cm. All specimens had branches underlying the traditional transverse incision for de Quervain's release. A 2.5-cm longitudinal incision proximal from the RS avoided the SBRN in 17/25 cases (68%). In 20/25 specimens (80%), the SBRN underlay the cephalic vein. In 18/25 (72%), the radial artery was closely associated with a sensory nerve branch near the level of the RS (SBRN 12/25, lateral cutaneous nerve of the forearm (LCNF) 6/25.) A longitudinal incision in de Quervain's surgery may be preferable. Cannulation of the cephalic vein in the distal third of the forearm is best avoided. The close association between the radial artery and first branch of the SBRN or the LCNF may explain the pain often experienced during arterial puncture. Particular care should be taken during radial artery harvest to avoid nerve injury.     

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.     

Anatomical variations of the pronator teres muscle in a Central European population and its clinical significance

The pronator teres (PT) muscle is a forearm flexor with radial and ulnar heads. It is innervated by the median nerve (MN), which passes between these heads. Nerve entrapment, known as “PT syndrome”, may occur in this passage. Anatomical variations in this region may be potential risk factors of this pathology. Therefore, the aim of the study was to determine the relationship between morphologic variations of the PT and the MN. In 50 isolated, formalin-fixed upper limbs, the cubital region and the forearm were dissected. The following measurements were taken: origin of the PT muscle heads, the length of these heads, the length of the forearm, diameter of the MN and the number of its muscular branches to the pronator teres muscle. The forearms with the humeral head originating from the medial humeral epicondyle and medial intermuscular septum (72%) were significantly shorter (p = 0.0088) than those where the humeral head originated only from the medial humeral epicondyle. Moreover, in these specimens, the MN was significantly thinner (p = 0.003). The ulnar head was present in 43 limbs (86%). The MN passed between the heads of the PT muscle (74%) or under the muscle (26%). In the majority of cases, it provided two motor branches (66%). There is an association between the morphologic variation of the PT muscle heads and the course and branching pattern of the MN. Both are related to differences in forearm length. This may have an impact on the risk of PT syndrome and the performance of MN electrostimulation.     

Applied anatomy of the musculus flexor carpi ulnaris and its clinical application

The blood vessels and nerves supplying 50 specimens of musculi flexor carpi ulnaris (FCU) in 25 Chinese male adult cadavers were investigated. The majority of the muscles were supplied by four to six blood vessels and by two branches of the ulnar nerve. The diameters of the second to fourth arteries were larger than 0.9 mm, which would allow them to be anastomosed to recipient vessels. As the arteries to the muscle were derived directly and/or indirectly from the ulnar artery, they could therefore be used as the arterial pedicles. The nerves were broad enough (1.18–1.05 mm) to act as nerve pedicles. These findings suggest that the FCU might be suitable for use as a free transplantation flap. Since the vessels and nerves to the FCU enter the muscle in its superior half, transposition in the reversed position is also possible. Eight patients have been treated by reversed transplantation of the FCU to restore lost function of the elbow joint. Follow-up studies showed uniformly good results.     

Vascular branches from cutaneous nerve of the forearm and hand: Application to better understanding raynaud's disease

Cutaneous nerves have branches called vascular branches (VBs) that reach arteries. VBs are thought to be involved in arterial constriction, and this is the rationale for periarterial sympathectomy as a treatment option for Raynaud's disease. However, the branching patterns and distribution areas of the VBs remain largely unclear. The aim of the present study was to investigate the anatomical structures of the VBs of the cutaneous nerves. Forty hands and forearms were examined to assess the branching patterns and distribution areas of the VBs of the superficial branch of the radial nerve (SBRN), the lateral antebrachial cutaneous nerve (LACN), the medial antebrachial cutaneous nerve (MACN), and the palmar cutaneous branch of the ulnar nerve (PCUN). VBs reaching the radial and ulnar arteries were observed in all specimens. The branching patterns were classified into six types. The mean distance between the radial styloid process and the point where the VBs reached the radial artery was 34.3 ± 4.8 mm in the SBRN and 38.5 ± 15.8 mm in the LACN. The mean distance between the ulnar styloid process and the point where the VBs reached the ulnar artery was 60.3 ± 25.9 mm in the MACN and 43.8 ± 26.0 mm in the PCUN. This study showed that the VBs of the cutaneous nerves have diverse branching patterns. The VBs of the SBRN had a more limited distribution areas than those of the other nerves. Clin. Anat. 31:734–741, 2018. © 2017 Wiley Periodicals, Inc.     

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.     

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.     

Location of nerve entry points of flexor digitorum profundus

The aim of this study was to elucidate the anatomical location of nerve entry points of Flexor digitorum profundus (FDP) and its implications for non-surgical neurolysis. A total of 21 amputated forearms of 11 Korean fresh cadavers were dissected. Two transverse x-axes joined the medial and lateral epicondyles and the radial and ulnar styloid processes. The longitudinal y-axis joined the midpoints of the proximal and distal transverse x-axes. The locations of the points were marked relative to the forearm length (x) and forearm width (y). The number of nerve entry points from median nerve and ulnar nerve were average 3.91 ± 0.62 (range 3–5, median 4) and 2.14 ± 0.65 (range 1–3, median 2) respectively. Most (82.9%) nerve entry points of FDP from the median nerve were within two circles, with 15 mm diameter. The two circles were on medial 1/10 of forearm width from the y-axis, and on proximal 1/3 (1:2) and 2/5 (2:3) of forearm length on x-axis. Most (80.0%) nerve entry points of the ulnar nerve innervating FDP were within a 15 × 30 mm rectangle. Its center was located at +26.5% on x-axis and −36.0% on y-axis. The nerve entry points used to be selected in performing non-surgical neurolysis with either ethyl alcohol (50%) or phenol (5–12%).     

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.     

骨间后神经及其拇示指肌支的解剖学特征

目的　观察前臂骨间后神经及其拇示指肌支的解剖学特征。 方法　解剖43具尸体的86侧上肢部桡神经深支及其分支到腕背部,观测骨间后神经的行程与投影及其拇示指肌支起始部位横径、长度和骨性标志线与神经干间夹角关系等参数。 结果　骨间后神经及其各分支均呈扁薄的窄带状神经束,其主干和多数肌支都走行在前臂后面中2/4段浅、深层肌之间,终末支止于腕背侧的梭形膨大部;主干起始处横径为（3.79±0.64）mm,各分支在起始部的平均横径（除指伸肌支约2.0 mm外）均小于1.0 mm;在旋后位,它呈向桡侧开放的弓形线段投影在肱骨外上髁至尺骨茎突连线的尺侧,半旋前位时则投影于该连线上或其桡侧。 结论　前臂后面中2/4段是骨间后神经主干及其大多数拇示指肌支在临床上易被损伤、误伤发生的高风险区域。     

Relationship between the ulnar nerve and the branches of the radial nerve to the medial head of the triceps brachii muscle

One branch of the radial nerve to the medial head of the triceps brachii muscle (MHN) has been described as accompanying or joining the ulnar nerve. Mostly two MHN branches have been reported, with some reports of one; however, the topographical anatomy is not well documented. We dissected 52 upper limbs from adult cadavers and found one, two, and three MHN branches in 9.6%, 80.8%, and 9.6% of cases, respectively. The MHN accompanying the ulnar nerve was always the superior MHN. The relationship between the ulnar nerve and the MHN was classified into four types according to whether the MHN was enveloped along with the ulnar nerve in the connective tissue sheath and whether it was in contact with the ulnar nerve. It contacted the ulnar nerve in 75.0% of cases and accompanied it over a mean distance of 73.6 mm (range 36–116 mm). In all cases in which the connective tissue sheath enveloped the branch of the MHN and the ulnar nerve, removing the sheath confirmed that the MHN branch originated from the radial nerve. The detailed findings and anatomical measurements of the MHN in this study will help in identifying its branches during surgical procedures. Clin. Anat. 00:1–16, 2018. © 2018 Wiley Periodicals, Inc.     

Ramification pattern of the thenar branch of the median nerve entering the thenar fascia and the distribution of the terminal branches in the thenar musculature: Anatomic cadaver study in 144 hands

Knowledge of the anatomy of the median nerve is important in surgery of the palmar aspect of the hand. The purpose of our study was to investigate the ramification pattern of the thenar branch before entering the thenar fascia and the distribution of the terminal branches in the thenar musculature. The observations were carried out on 144 hands of 74 dissecting room cadavers. According to the number of the thenar branches entering the thenar fascia we classified our specimens into four types. In 121 hands (84%, Group I) the thenar branch piercing the thenar fascia was a single trunk. In 19 hands (13.2%, Group II) two branches; in three (2.1%; Group III), three branches; and in one hand (0.7%; Group IV), four branches were identified entering the thenar fascia. Accessory thenar nerve was found in 8.3% of hands. The further division of each branch to its terminal branches was investigated in detail. Our results show that the more the number of thenar branches entering the thenar fascia, the less the terminal branching. Because more than one branch was seen in 16% of the specimens, meticulous dissection is required for preventing injury of the thenar branches before entering the thenar fascia.     

桡,尺动脉肌,皮支的解剖学研究

目的:为手外科提供桡、尺动脉分出的肌、皮支.材料和方法:用福尔马林常规固定的成尸上肢69(男61,女8)侧,解剖观测桡、尺动脉分支的部位、支数及外径.主要结果:从尺、桡动脉壁两侧发出分支,大部分为不对称性分支间距不等,平均(3.0～15.0)mm.桡动脉平均分出15.8支,其中肌支10.3支,筋膜皮支5.5支.尺动脉平均分出12.4支,其中肌支7.6支,筋膜皮支4.8支.结论:桡、尺动脉分出肌、皮支,皮支为前臂筋膜瓣、皮瓣的血管蒂.     

An aberrant anatomic variation along the course of the ulnar nerve above the elbow with coexistent cubital tunnel syndrome

We report on a patient with an unusual anatomic variation along the course of ulnar nerve above the elbow who had cubital tunnel syndrome. The variation consisted of a cutaneous neural branch that was originating at a distance of approximately 40 mm proximal to the medial epicondyle, and from the radial aspect of the main trunk of ulnar nerve. The branch had a superficial course and it was passing distally, anterior to the medial epicondyle without penetrating the fascia of the flexor muscles origin. Anterior intramuscular transposition of the ulnar nerve was performed leaving the newly found branch over the fascia between the muscles and the adipose subcutaneous tissue.