Superficial palmar communications between the ulnar and median nerves in Turkish cadavers

The superficial palmar communicating branch between the ulnar and median nerves, the ramus communicans (RC), has been investigated by anatomical dissections in 30 hands of 15 cadavers in the Turkish population. A communicating branch between the ulnar and median nerves was found in 18 hands (60%). It was classified into 4 types: Type 1-RC emerging from the ulnar 4th common digital nerve (CDN) and uniting with the median 3rd CDN, Type 2-RC emerging from the median 3rd CDN and uniting with the ulnar 4th CDN, Type 3-RC extending horizontally between the 3rd and 4th CDN, Type 4-a plexiform RC formed by multiple twigs. Twelve hands (40%) showed the Type 1 arrangement, one was Type 2 (3.3%), two were Type 3 (6.7%) and three (10%) were Type 4, based on the classification devised by Meals and Shaner ([1983] J Hand Surg Am 8:411-414) and modified by Bas and Kleinert ([1999] J Hand Surg Am 24:1171-1184). Knowledge of the anatomical characteristics of this branch is important for surgical interventions, especially in carpal tunnel release operations.     

Definition of a safe-zone in open carpal tunnel surgery: a cadaver study

Carpal tunnel decompression is one of the most common surgical procedures in hand surgery. Cutaneous innervation of the palm by median and ulnar nerves was evaluated to find a suitable incision preserving cutaneous nerves. A morphometric study was designed to define the safe-zone for mini-open carpal tunnel release. Sixteen fresh-frozen (8 right, 8 left) and 14 formalin-fixed (8 right, 6 left) cadaveric hands were dissected. Anatomy of the palmar cutaneous branch of the median and the ulnar nerve, motor branch of the median nerve, superficial palmar arch were evaluated relative to the surgical incision. We also identified the motor branch of the median nerve. Detailed measurements of the whole palmar region are reported in this study. The motor branch of the median nerve was extraligamentous as 60%, subligamentous as 34%, transligamentous as 6%. The palmar cutaneous branches of the median and the ulnar nerves in the palmar region were classified as Type A (34%), Type B (13%), Type C (13%), Type D (none), Type E (40%) according to forms of palmar cutaneous innervation originating from the ulnar and median nerves. Injury to the palmar cutaneous branch of the median nerve (PCBMN) is the most common complication of the carpal tunnel surgery. Various techniques were described to decrease post-operative morbidity. Based on these anatomic findings mini incision between the superficial palmar arch and the most distal part of the PCBMN in the palmar region is the safe-zone for carpal tunnel surgery.     

Stratification of the flexor retinaculum and the course and distribution of the ulnar, median, and palmar digital nerves: an anatomical study

A gross anatomic study of 169 hands from 94 human adult cadavers was carried out to define the morphology of the flexor retinaculum and the relationship of the flexor retinaculum to the course of the median and ulnar nerves and branching of the palmar digital nerves. The following results were obtained. Three parts of the flexor retinaculum were arranged like overlapping tiles on a roof, and in all cases, the median nerve passed deep to the flexor retinaculum, whereas the ulnar nerve passed through various parts of the flexor retinaculum in 19% of cases irrespective of its proximal form and branching of the palmar digital nerves.     

The clinical anatomy of the communications between the radial and ulnar nerves on the dorsal surface of the hand

Sensations of the dorsal surface of the hand are supplied by the radial and ulnar nerves with the boundary between these two nerves classically being the midline of the fourth digit. Overlap and variations of this division exist and a communicating branch (RUCB) between the radial and ulnar nerves could potentially explain variations in the sensory examination of the dorsal hand. The aim of this study was to examine the origin and distribution of the RUCB thereby providing information that may potentially decrease iatrogenic injury to this connection. We grossly examined 200 formalin-fixed adult human hands. A RUCB was found to be present in 120 hands (60%). Of the specimens with RUCBs, we were able to identify four notable types. Type I (71, 59.1%) originated proximally from the radial nerve and proceeded distally to join the ulnar nerve. Type II (23, 19.1%) originated proximally from the ulnar nerve and proceeded distally to join the radial nerve. Type III (4, 3.3%) traveled perpendicularly between the radial and ulnar nerves so that it was not possible to determine which nerve served as its point of origin. Type IV (18.3%) had multiple RUCBs arising from both the radial and ulnar nerves. With the continual development of new surgical techniques and the ongoing effort to decrease postoperative complications, it is hoped that this study will provide useful information to both anatomists and surgeons.     

Biometric study of the relationships between palmar neurovascular structures, the flexor retinaculum and the distal wrist crease

During surgical exposure of the carpal tunnel it is possible to injure the neurovascular structures closely related to the flexor retinaculum, such as the superficial palmar arch and the communicating branch between the ulnar and median nerves. Because of the importance of these structures and with the purpose of increasing knowledge of anatomical details concerning to their location, a biometric study was performed on the retinaculum and the communicating branch, and between the communicating branch and the distal wrist crease, as well as between the retinaculum and the superficial palmar arch. We dissected 56 hands from 28 Brazilian formalin‐preserved cadavers of both sexes (24 male) at the Federal University of São Paulo–Escola Paulista de Medicina, Brazil. The communicating branch was observed in 96.4% of cases and the superficial palmar arch in 78.6%. The communicating branch was found between the common palmar digital nerve of the 4th interosseous space (from the ulnar nerve) to the homonymous nerve of the 3rd interosseous space (from the median nerve). In males, the distance between the distal wrist crease and the site where the communicating branch originates from the ulnar component had an average of 33.9±5.5 mm on the right side and 30.2±8.2 mm on the left. The distance between the distal wrist crease and the junction of the communicating branch with the common palmar digital nerve of the 3rd interosseous space was 43.6±6.9 mm on the right and 40.2±6.2 mm on the left side. Conversely, in 14.8% of cases (1 female), the communicating branch was observed to emerge from the common palmar digital nerve of the 3rd interosseous space. The distance between the retinaculum and the superficial palmar arch in the axial line of the 4th metacarpal bone was on average 7.3±4.3 mm on the right and 8.3±3.5 mm on the left side. At the same level, the distance between the retinaculum and the communicating branch was 6.2±3.7 mm on the right side and 5.1±2.8 mm on the left. These results can be used as a reference during surgical procedures in the palmar region.     

断掌再植的神经解剖学基础

目的：为断掌再植的神经修复提供解剖学基础。方法：对30侧成人手标本掌部浅、深两层的主要神经分支进行解剖。以远侧腕横纹为横坐标，以掌中线为纵坐标对掌部主要神经分支的起、止点进行坐标测量。将手掌部划分为64个正方形小区，按照掌部主要神经分支起、止坐标对各神经进行小区定位，确定各神经分支的体表投影。模拟不同平面断掌，确定各断掌平面应修复的神经。结果：R1T3、R1T4、R2T2、R2T3、R2T45个小区集中了正中神经返支、正中神经分叉处及尺神经深支的大鱼际肌段，此区域神经分支较多，是断掌时神经修复的重要区域。U2T1、U2T2、U3T33个小区有尺神经深支通过，通过此三小区的断掌应仔细修复尺神经深支。结论：本文结果可供对断掌及其他手掌外伤的神经损伤修复作出较为准确的定位，并根据预测结果对掌部损伤神经进行有目的的修复。     

Ulnar nerve cutaneous distribution in the palm: Application to surgery of the hand

The ulnar nerve (UN) was classically described as supplying most of the intrinsic muscles of the hand, and the cutaneous innervation of the ulnar one and half digits, by dividing into superficial sensory and deep motor branches in Guyon's canal. Variations of this pattern have been reported in the literature. This study investigated the cutaneous distribution of the UN in the palm following the dissection of 144 cadaveric hands. The UN was examined and the distances from branching points of the superficial branch to the proximal edge of the pisiform were measured. The UN bifurcated (80.4%) into one deep trunk and one superficial trunk, which further divided distally into the proper digital (PDN) and common digital (CDN) nerves or trifurcated (19.6%) into one deep trunk, a PDN and a CDN in Guyon's canal. It received fibers from the median nerve in four cases and from the dorsal branch of the UN in six cases. A classification scheme based on the nerves contributing to the sensory innervation of the ulnar side of the palm was suggested. Understanding the cutaneous distribution of the UN in the palm and appreciating possible communicating branches can help clinicians to assess hand pathologies better and avoid injuries during surgical interventions. Clin. Anat. 28:1022–1028, 2015. © 2015 Wiley Periodicals, Inc.     

A rare anatomical variation of the Berrettini anastomosis and third common palmar digital branch of the median nerve

Variations in the origin and distribution of Berrettini anastomosis between the digital branches of the ulnar and median nerves exist and are well described in the literature. During regular dissections by medical students, we encountered a rare variation in the left hand of an approximately 50-year-old male cadaver. Berrettini anastomosis connecting the third common palmar digital branch of the median nerve with the fourth common palmar and proper palmar digital branches of the ulnar nerve presented a plexiform nature. This communicating branch and the third common palmar digital branch of the median nerve were perforated by the superficial palmar arch. Further, the superficial palmar arch was incomplete, and it was solely formed by the superficial branch of the ulnar artery. The unusual relationship of Berrettini anastomosis with the superficial palmar arch is very rare, and knowledge about such a variation is important when performing carpal tunnel release, flexor tendon surgery, and Dupuytren’s fasciectomy and when dealing with arterial repairs and vascular graft applications in the hand.     

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.     

Homology of the adductor pollicis and contrahentes muscles: a study of monkey hands

The deep palmar muscles in monkey hands were studied. The contrahentes muscles mainly arose from the capitate bone, descended palmar to the deep palmar branch of the ulnar nerve and the palmar metacarpophalangeal nerves, and attached to the proximal phalanges or wing tendons of the second, fourth and fifth fingers. In relation to the deep palmar branch of the ulnar nerve and the palmar metacarpophalangeal nerves, the contrahentes muscles are homologous with the adductor pollicis and flexor indicis radialis muscles. The contrahentes muscles occasionally gave off some accessory slips which blended with the interosseous muscles. These findings suggest that the human adductor pollicis muscle is a well-developed remnant of a contrahens muscle, and that the human interosseous muscles contain some remnant of the contrahentes muscle. In fact, a well-developed remnant of a contrahens muscle was found in the fourth finger of a human hand. It is further considered that the human adductor pollicis muscle contains an element of the interosseous muscle of the thumb.     

Anatomic variations of the median nerve within the carpal tunnel

Two hundred seventy-five consecutive carpal tunnel releases were reviewed to identify anomalies of median nerve anatomy. High division of the median nerve was observed in nine cases; in two of these the nerve divided proximally and then rejoined distally as a “closed loop.” In 42 cases the motor branch passed through the flexor retinaculum. Multiple motor branches were present in 13 cases. The palmar cutaneous branch passed through the flexor retinaculum in seven cases. In three cases, the distal communicating sensory ramus between the medial and ulnar nerves arose proximal to the superficial arch. Median nerve anomalies within the region of the carpal tunnel are common. Knowledge of such anomalies is important to avoid iatrogenic injury.     

吻合指神经的指动脉逆行岛状皮瓣修复指腹缺损

目的：报道吻合指神经的指动脉逆行岛状皮瓣修复指腹缺损的解剖学基础及其临床应用。方法：对20具成人尸体40例手的指掌侧固有神经直径和分支进行了测量；并对39例患者的39指指腹缺损行吻合指掌侧固有神经的指动脉逆行岛皮瓣修复术。结果：（1）指掌侧固有神经平近节指横纹处理1．4－2．0mm，厚0．8－1．0mm；平末节指横纹处宽1．0－1．4mm，厚0．6－0．8mm。（2）近节掌侧支为4．4－5．3支，背侧支为3．8－4．0支；中节掌侧支为3．5－4．6支，背侧支为3．4－4．1支；末节终支为3．8－4．6支。（3）39例患指中38例一期成活，指腹饱满，外观理想，耐磨性好，两点辨别觉达5mm内，指腹感觉达S3以上。结论：吻合指神经的指动脉逆行岛状皮瓣修复指腹缺损，优于未吻合神经的术式。     

The brachial plexus of the Japanese serow (Capricornis crispus)

The brachial plexus of the Japanese serow was macroscopically studied. It was composed of nerves derived from the sixth (C6), seventh (C7) and eighth (C8) cervical nerves and the first (T1) thoracic nerve (98.1%). Rarely, the second T2) thoracic nerve joined it (1.9%). C6 joined C7 and made up the cranial trunk. C8 and T1 (+T2) united to form the caudal trunk. Each trunk split into dorsal and ventral divisions. The dorsal divisions from C6-T1 formed the dorsal cord which gave off the thoracodorsal, axillary and radial nerves. The manner of union of ventral divisions and their divergence was classified into 4 types. Type I was that the ventral cord was formed by cranial and caudal ventral divisions and sprouted the musculocutaneous, median and ulnar nerves. It was found in 67.3%. Type II was that the proximal muscular ramus of the musculocutaneous nerve emerged from the median nerve and the ulnar nerve appeared from the caudal ventral division from C8-T1. It was observed in 19.2%. Type III was that the proximal muscular ramus and ulnar nerve were derived from the cranial and caudal ventral divisions, respectively. It was seen in 11.6%. Type IV was quite different from type I to III. The cranial ventral division from C6-C7 was not observed. The caudal ventral division from C8-T1 alone formed the ventral cord giving off the nerves. It was encountered in one case (1.9%) and probably represented rare variation. These findings indicate that the brachial plexus of the Japanese serow is chiefly similar to that of other ruminants.     

Cortical Characterization and Inter-Dipole Distance Between Unilateral Median Versus Ulnar Nerve Stimulation of Both Hands in MEG

Summary Contralateral somatosensory evoked fields (SEF) by whole head MEG after unilateral median and ulnar nerve stimulation of both hands were studied in 10 healthy right-handed subjects. Major parameters describing cortical activity were examined to discriminate median and ulnar nerve evoked responses. Somatic sensitivity showed high similarity in the 4 study conditions for both hand and nerve. The brain SEFs consisted of 7–8 major peak stages with consistent responses in all subjects at M20, M30, M70 and M90. Comparable inter-hemispheric waveform profile but high inter-subject variability was found. Median nerve induced significantly shorter latencies in the early activities than those of the ulnar nerve. The 3D cortical maps in the post stimulus 450 ms timeframe showed for both nerves two polarity reversals, an early and a late one which is a new finding. Dipole characteristics showed differential sites for the M20 and M30 in the respective nerve. Higher dipole moments evoked by the median nerve were noticed when compared to the ulnar. Furthermore, the results of the dipole distances between both nerves for M20 were calculated to be at 11.17 mm ± 4.93 (LH) and 16.73 mm ± 5.66 (RH), respectively after right hand versus left hand stimulation. This study showed substantial differences in the cortical responses between median and ulnar nerve. Especially the dipole distance between median and ulnar nerve on the cortex was computed accurately for the first time in MEG. Little is known however of the cortical responses in chronic pain patients and the parameter(s) that may change in an individual patient or a group. These results provide precise basis for further evaluating cortical changes in functional disorders and disease sequelae related to median and ulnar nerves.     

Unusual vascularization and nerve supply of the fifth finger.

During a dissection course, an unusual variation in vascularization and nerve supply of the fifth finger of the right hand was found in a 73-year-old human male cadaver. The proper digital palmar artery arose from the superficial branch of the ulnar artery distel to the Guyon's canal. The proper digital palmar artery coursed first palmar to the ulnar nerve then between the abductor minimi and flexor digiti minimi muscles to reach the ulnar side of the fifth finger. Besides this, the ulnar border of the fifth finger was supplied on its palmar side by the dorsal branch of the ulnar nerve, which gave off two tiny twigs for the sensory innervation on the dorsal side of the same finger.     

The communicating branch of the 4th cervical nerve to the brachial plexus: the double constitution, anterior and posterior, of its fibers

Twenty-four adult cadavers (48 sides) were used to investigate the incidence of a branch arising from the ventral ramus of the fourth cervical nerve (C4) with the phrenic nerve and subsequently joining the brachial plexus. Six brachial plexuses with spinal cords and phrenic nerves were dissected under a surgical microscope to investigate localization of fibers contained in the C4 branch to the brachial plexus. The incidence of the C4 branch was 23% (11/48 sides). Branches from C4 to the brachial plexus divided into anterior and posterior divisions on four sides (4/6 sides). On two sides, the branch did not divide but consisted entirely of an anterior division (2/6 sides). In the brachial plexus, anterior division fibers of the C4 branch were intertwined with fibers from the anterior divisions of the ventral rami of the fifth and sixth cervical nerves. They then passed to the suprascapular nerve and the anterior division of the superior trunk (6/6 sides). On the other hand, posterior division fibers of the C4 branch were intertwined with fibers from the posterior divisions of the ventral rami of the fifth and sixth cervical nerves. They then passed to the suprascapular nerve (2/6 sides) and the posterior division of the superior trunk (4/6 sides). The anterior division of the C4 branch received fibers from the ventral rootlets of the entire fourth cervical segment, whereas the posterior division received fibers from the ventral rootlets of the caudal half of the fourth cervical segment only. The fact that the suprascapular nerve received fibers from both the anterior and posterior divisions of the C4 branch was considered to support our claim that the human suprascapular nerve belongs to both the anterior and posterior divisions of the brachial plexus.     

A morphometric study on the superficial palmar arch of the hand

The vascular anatomy of the hand is a complex and challenging area and has been the subject of many studies. Knowledge of the vascular patterns and diameters of the hand gained more importance with improvements in microsurgical techniques in reconstructive hand surgery. We evaluated 50 hands (26 left, 24 right) of 26 formalin preserved cadavers to determine the superficial palmar arch, its branches and contributing vessels with special attention to the diameters. The symmetry of the types was also evaluated in detail for the first time in the literature. Measurements were made with the help of a digital caliper. The diameters of the ulnar, radial and median arteries were taken at the level of the wrist while the common palmar digital arteries, hypothenar branches and the superficial palmar branch of the radial artery were measured at their origin. Two types of superficial palmar arch were found and defined as complete (43/50 hands) and incomplete arches (7/50 hands). The complete arches were divided into four subgroups and incomplete arches into three subgroups. Most cases were found at the complete AI group (17 hands). Comparison of the arterial diameters showed the ulnar artery was the dominant vessel of the palm. The diameters of the common palmar digital arteries were not different with regard to complete or incomplete arches and between both sides. It looks safe to sacrifice one of the radial or ulnar arteries in some arterial interventions including radial artery cannulation, radial forearm flap and radial or ulnar artery harvesting for bypass grafting if the arch is complete. But we still recommend the noninvasive tests like modified Allen test or Doppler ultrasonography, before performing an invasive arterial intervention. We propose the radiologists to incorporate the median artery into the Doppler dynamic test in particular the existence or the absence of anastomoses between radial and ulnar arteries.This study was accepted as an oral presentation in the “IX National Congress of Anatomists, 7–10 September 2005, Kusadasi, Turkey”     

Deep palmar communications between the ulnar and median nerves

Innervation of the hand is supplied via the radial, median, and ulnar nerves. A common border of sensory distribution between the ulnar and median nerves is along the fourth digit. However, this sensory distribution may be affected by communication between these two nerves. Among the known communications between the median and ulnar nerves, the deep anastomotic branch in the hand is the least described and rarely illustrated in the literature. This study aims to provide data on the prevalence of a deep communicating branch via cadaveric dissection. We examined 50 hands taken from 25 adult cadavers. Communicating branches were found in 16% of the hands examined, with rami occurring bilaterally in two specimens. By describing the origin and pathway of this communicating branch, we hope to provide surgeons and clinicians with knowledge that may help avoid iatrogenic injuries.     

Symmetric lipofibromatous hamartoma affecting digital nerves

Lipofibromatous hamartoma of the nerve is a benign tumor, which affects the major nerves and their branches in the human body. It is often found in the median nerve of the hand and is commonly associated with macrodactyly, but it is rarely found in the digital nerves at the peripheral level. This tumor is often found in young adults and may go through a self- limiting course. However, operation is indicated when the tumor size is large or when the associated nerve compressive symptoms are present. We have experienced a rare case of lipofibromatous hamartoma that symmetrically involved the volar digital nerves of both index fingers on the ulnar side. With the aid of a microscope, we dissected and removed the tumor as much as possible without sacrificing the nerve. No sensory change occurred in both fingers and no sign of recurrence was observed upon follow-up.     

Anatomic basis of ulnar index metacarpal reverse flow vascularized bone graft for index distal bone loss

Well-known advantages of vascularized bone grafts led us to determine the anatomical basis of a metacarpal vascularized bone graft to find a solution for distal index bone loss. Seventeen adult human hands from fresh cadavers were dissected and analyzed. For each hand, we studied the second dorsal metacarpal artery, the ulnar dorsal proper digital artery of index, and the ulnar palmar proper digital artery of the index. Location, diameters, origins, and anastomoses were observed, and at the end, the vascularised bone graft was raised. The second dorsal metacarpal artery was present in all hands, always arising from the dorsal carpal arch with a 1-mm mean diameter. The ulnar dorsal proper digital artery of index was isolated on all dissections, with a subcutaneous location on the ulno-dorsal side of the proximal phalanx. The mean diameter of ulnar dorsal proper digital artery at the level of index proximal phalanx was 0.4 mm. We found anastomotic branches between the ulnar dorsal and palmar proper digital artery of index at the level of the proximal phalanx which permitted us to elevate a vascularised bone graft. We succeeded in removing the graft in all specimens. Its pivot point was always more distal than the middle of the proximal phalanx. The arc of rotation allowed the graft to reach the distal phalanx in 80% of the cases. This anatomical study has demonstrated the theoretical possibility of a reversed pedicled bone graft taken from the ulnar neck of the second metacarpal. This graft brings the following benefits: (a) the use of a minor vascular axis, (b) a surgical technique with a dorsal approach allowing the elevation and the use of the graft at the same time. It can be used on the index for failures of DIP joint arthrodesis, huge chondroma, or traumatology.