Internal anatomy of the communicating branch between the ulnar and median nerves in the hand and its relevance to volar digital sensibility.

We studied the microanatomy of the communicating branch between the ulnar and median nerves in 26 adult cadaver hands to explain diminished sensibility in the fourth and fifth fingers we had observed in 2 patients after complete transection of the median nerve. Two new variations of the communicating branch were observed. In the first variation the communicating branch originated proximally from the third common digital nerve to distally join the ring finger ulnar digital nerve and the small finger radial digital nerve. In the second variation the ramus communicans traversed perpendicularly between the third and fourth common digital nerves with a crossover of nerve fibers.     

Anatomic study of the ramus communicans between the ulnar and median nerves

The communicating branch between the fourth and third common digital nerves in the palm of the hand was studied. The incidence and branching pattern were studied in 53 dissected cadaveric hands. The "danger zone" in which the nerve is at risk during surgery was established using morphometric data. A communicating branch was found in 50 hands. It originated proximally from the fourth common digital nerve to join the third common digital nerve distally in 44 hands and traversed perpendicularly between the third and fourth common digital nerves in 4 hands. In the 2 remaining hands the branch left the third common digital nerve proximally to join the fourth digital common nerve distally. In 90% of the hands the ramus communicans crossed over in the middle third of the palm of the hand. As a cautious measure, hand surgeons should take into account that this structure could cross over anywhere in the middle three fifths of the palm.     

Sensory communication of the median and ulnar nerves in the palm

A communicating branch between the median and superficial ulnar nerve in the palm of the hand has been described, but its relationship to the cutaneous anatomy of the hand has had little emphasis. Fifty preserved cadaveric hands were dissected. A communicating branch was found in 37 of 50 specimens. In 34 specimens, the connecting branch proceeded from the ulnar nerve to enter the median nerve distally; in three specimens it proceeded from the median nerve to reach the ulnar nerve distally. This study describes the communicating branch in relation to the distal crease of the wrist with the axis of the third webspace and fifth ray as the radial and ulnar borders, respectively. This study may aid surgeons in determining the likelihood of injury in trauma or during various surgical procedures.     

Anatomic variations in sensory innervation of the hand and digits

Anatomic dissections under microscopic magnification were performed on 30 fresh cadaveric hands to depict the course and interconnections of the sensory nerves to the digits. The dissections included the median nerve, the ulnar nerve, the superficial branch of the radial nerve, the dorsal branch of the ulnar nerve, and the dorsal branch of the proper digital nerve. The communicating branches between the median and ulnar nerves in the palm were found in 20 of the 30 (67%) specimens. The dorsal branch of the proper digital nerve was found to arise at or proximal to the A1 pulley zone in 62% of the long digits, more proximally than previously reported. The dorsal sensory nerves (the terminal branch of radial or ulnar sensory nerves) extending to the nail bed area were found in 46% of the digits, thus confirming that sensory supply to the dorsum of the distal phalanx and nail bed also arises from the dorsal sensory nerves. Four types of palmar-dorsal interconnections, located in the middle of the proximal phalanx, were found in the digits but not in the thumb. The presence of these branches indicates dual innervation of the dorsal and palmar side of the distal areas of the digits. These anatomic findings may help hand surgeons interpret discrepancies in sensory loss after either dorsal or palmar injuries.     

Anatomic study of variations of hypothenar muscles and arborization patterns of the ulnar nerve in the hand

PURPOSE: To show the variations in the hypothenar muscles and the arborization patterns of the ulnar nerve and to investigate the relationship between the hypothenar muscles and the ulnar nerve. METHODS: We performed an anatomic study of 35 hands from embalmed cadavers. After dissecting the ulnar side of the hand we recorded the number of hypothenar muscles and their variations, the site of the hiatus for the deep branch of the ulnar nerve, and the branching patterns of the ulnar nerve in each hand. We then investigated the relationship between the variations in the hypothenar muscles and the arborization patterns of the ulnar nerve. RESULTS: The abductor digiti minimi (ADM) had 1 belly in 6 hands, 2 bellies in 28 hands, and 3 bellies in 1 hand. The flexor digiti minimi brevis was absent in 8 hands, had 1 belly in 24 hands, and had 2 bellies in 3 hands. The opponens digiti minimi had 2 layers of origin and the deep branch of the ulnar nerve passed between these 2 layers in all hands. We classified the structural patterns of the hiatus into 3 types, the arborization patterns of the ulnar nerve into 5 types, and the branching patterns of the motor branch to the ADM into 4 types according to their morphologic characteristics. We found variations of the arborization pattern in which the deep branch originated from the ulnar trunk of the ulnar nerve distal to bifurcation in 3 hands, a communicating branch was present between the 2 sensory branches to the fingers in 3 hands, and the ulnar sensory branch pierced the ADM in 2 hands. CONCLUSIONS: We confirmed that the anatomic relationship between the ulnar nerve and the hypothenar muscle is complex and that the formation of the hiatus varies. This knowledge can assist the surgeon in the diagnosis and treatment of conditions associated with the ulnar aspect of the hand.     

Unusual anatomic variation of palmar sensory branches of the ulnar nerve: a case report.

Variant sensory branches of the ulnar nerve were encountered during a routine dissection of the palmar aspects of a cadaver hand. The variant branches were distributed to the ulnar half of the index, ulnar half of the middle, and radial half of the ring fingers. The communicating branch between the superficial ulnar branch and the third common digital branch of the median nerve was absent. Distribution of the median nerve sensory branches was normal. The clinical significance of this variation is discussed.     

Multiple neurilemmomas of the median and ulnar nerves with a communicating branch in the same upper extremity.

A 30-year-old woman presented with multiple neurilemmomas in the same upper extremity. One originated from the main trunk of the ulnar nerve and two others from the sensory branch of the median nerve. A communicating branch in the palm from the ulnar nerve to the median nerve was confirmed. All the tumours were successfully enucleated and she made a satisfactory recovery.     

Multiple Neurilemmomas of the Median and Ulnar Nerves with a Communicating Branch in the Same Upper Extremity

A 30-year-old woman presented with multiple neurilemmomas in the same upper extremity. One originated from the main trunk of the ulnar nerve and two others from the sensory branch of the median nerve. A communicating branch in the palm from the ulnar nerve to the median nerve was confirmed. All the tumours were successfully enucleated and she made a satisfactory recovery.     

Autogenous nerve pedicle graft in the forearm

We report our experience during a 15-year period with three patients who had severe segmental loss of more than 10 cm of both the median and ulnar nerves in the arm and forearm. The procedure was described by St. Clair Strange and by Silverstone in 1947. A modification of the procedure was used in our three patients. In two patients, the proximal stumps of the median and ulnar nerves were sutured together in the proximal forearm. The ulnar nerve was transected high in the axilla, leaving its blood supply intact. Several months later the ulnar nerve was transposed distally, and a juncture with the distal median nerve was created. The third patient had a significant segmental loss in the arm of both the median and ulnar nerves. The distal stumps of the median and ulnar nerves were sutured together, and at a later stage the ulnar nerve was transposed proximally and sutured to the median nerve in the axilla. In all three patients, an advancing Tinel sign was observed. Subjectively, all three patients believed there was a definite improvement in sensibility. Objective testing was, however, less convincing. This operation has limited applicability but definitely has a place in situations where direct sutures or nerve grafting are impossible.     

The anatomy of the Berrettini branch: implications for carpal tunnel release

OBJECT: Dissections were performed in 100 fresh cadaver palms to determine the frequency with which superficial palmar communication between the median and ulnar nerves occurs and to what extent it might incur iatrogenic injury during endoscopic carpal tunnel release. METHODS: Superficial palmar communication between the median and ulnar nerves was present in 81% of the dissected hands. Superficial palmar communication, also known as the Berrettini branch, has been classified into four distinct types by Ferrari and Gilbert. Twelve hands were classified as Group 1 (communication in an oblique course from the ulnar to the median nerve originating >4 mm above the distal margin of the transverse carpal ligament [TCL]), 16 hands were classified as Group 2 (communication parallel to the distal margin of the TCL), and 53 hands were classified as Group 3 (communication in an oblique course from the ulnar nerve to the third common digital nerve, originating below the distal margin of the TCL). No hand fit the Group 4 classification (atypical communication). CONCLUSIONS: The Berrettini branch can be considered a normal anatomical finding. In 28% of the hands in this study, the branch was proximal to the edge of the distal ligament and, therefore, prone to iatrogenic injury in both one-portal and two-portal endoscopic surgery.     

Safety of carpal tunnel release with a short incision. A cadaver study

The standard long incision technique for carpal tunnel release causes inevitable damage to skin sensation, the inter-thenar plexus and especially the distal branches of the palmar cutaneous branch of the median nerve (PCM), and may cause long-term disabling pain and scar tenderness. There are many variations in the distal branches of the median nerve at the wrist. Anatomic studies of this region also have important clinical implications to prevent injury to important anatomic structures. The purpose of this study was to evaluate the short-incision carpal tunnel release in cadavers. Several important anatomic structures, with possible anatomic variations, pass through the carpal tunnel, and blind percutaneous transection of the transverse ligament seems to be a high risk procedure. Sixty hands from 40 fresh cadavers were evaluated. Both the transverse ligament and the distal third of the deep forearm fascia were released using a Smillie knife. At the end of each procedure, the hand was explored for injury to tendinous and neurovascular structures of the wrist. In all cases the release of the carpal tunnel and the distal third of the forearm fascia was found to be complete. The superficial palmar arterial arch, flexor tendons, ulnar nerve and vessels, digital nerves, median nerve and its recurrent accessory branches, the flexor tendons, and even the subcutaneous tissue over the transverse ligament were damaged in no instance. Guyon's canal was entered in 6 (10%) hands without damage to its components. The distal branches from the ulnar side of the palmar cutaneous branch of the median nerve (PCM) were injured in 8 (13.6%) hands, an injury that is almost unavoidable with the classic open technique.     

Quantitation of and landmarks for the muscular branches of the ulnar nerve to the forearm for application in peripheral nerve neurotization procedures

OBJECT: In neurotization procedures, donor nerves--either whole or in part-with relatively pure motor function can be carefully chosen to provide the optimal nearby motor input with as little donor site morbidity as possible. In this context, the ulnar nerve branches to the forearm muscles are relatively dispensable; however, quantitation of and landmarks for these branches are lacking in the literature. METHODS: The ulnar branches to the flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP) muscles in 20 upper extremities obtained in adult cadaveric specimens were dissected and quantified. In the forearm, a mean of four nerve branches led to the FCU and FDP muscles. A mean of 3.4 branches led to the FCU muscle; of these, one to three were medial branches and zero to two were lateral. Medial branches to the FCU muscle originated a mean of 2.7 cm inferior to the medial epicondyle. Lateral branches to the FCU muscle originated at a mean of 3.3 cm inferior to the medial epicondyle. The mean length of the medial branches was 3.2 cm, whereas the mean length of the lateral branches was 3.3 cm. All nerves had a single trunk for the FDP muscle, and in all specimens this branch was located deep to the main ulnar nerve trunk, originating from the ulnar nerve a mean of 2.7 cm inferior to the medial epicondyle. These branches had a mean length of 5.6 cm. The mean diameter of all medial and lateral branches to the FCU muscle was 1 mm, and the mean diameter of the branch to the FDP muscle was 2.1 mm. All branches to both the FCU and FDP muscles arose from the ulnar nerve, over its first approximately 5 cm from the level of the medial epicondyle. Additionally, all branches could be easily lengthened by gentle proximal dissection from the main ulnar nerve. CONCLUSIONS: Ulnar branches to the forearm can be easily localized and used for neurotization procedures. The branch to the FDP muscle had the greatest diameter and longest length, easily reaching the median nerve and posterior interosseous nerve via a transinterosseous membrane tunneling procedure. Furthermore, this branch could be teased away from the main ulnar nerve trunk and made to reach the distal branches of the musculocutaneous nerve in the arm.     

Digital innervation patterns following median or ulnar nerve laceration and their correlation to anatomic variations of the communicating branch between these nerves

The midline of the ring finger is classically considered as the neural watershed between the median and ulnar nerve sensory territories on the palmar surfaces of the fingers. Variations of this division exist and may be explained by a communicating branch between the third and fourth common digital nerves. The palmar sensibility patterns of fingers were assessed with Semmes Weinstein filaments after either a complete median or an ulnar nerve transection in 43 patients. Eight out of nine observed sensibility patterns could be explained by known anatomic types and subtypes of the communicating branch. The type of communicating branch, but not its subtype, could be established in the one remaining pattern.     

The importance of internal anatomy of the peripheral nerves to nerve repair in the forearm and hand

We have completed and analyzed recent studies on the internal topography of the median and ulnar nerves of the forearm and hand. These findings have been compared with the classic studies of Sir Sydney Sunderland and more recent work by other authors has been included. Our studies confirm that there is a complex interfascicular relationship between the various components of the median and ulnar nerves in the forearm and hand, but, with careful dissection, several anatomic relationships can be defined. Individual branches and bundles can be traced within the main nerve trunks for considerable distances without significant trauma to the conducting fibers. These include the recurrent branch of the median nerve, the branches to the lumbrical muscles, the motor and sensory components of the ulnar nerve, and the dorsal sensory branch of the ulnar nerve. These findings have a direct relationship to the clinical repair of fresh nerve injuries as well as those injuries that require nerve grafting for significant gaps in the neural tissue. Intraneural neurolysis can be safely performed if detailed knowledge of the internal topography of the peripheral nerves is understood. This knowledge may also be applied to the dissection and management of neuromas in continuity. The increased awareness of the interfascicular relationships of the peripheral nerves may well influence a more favorable outlook in the care of patients with nerve injuries.     

Ultrasound examination of peripheral nerves in the forearm

BACKGROUND AND OBJECTIVES: We examined in a volunteer population whether nerves in the forearm could be seen consistently using ultrasound imaging and whether this new information could have implications for the way we perform regional anesthesia of the median, radial, and ulnar nerves. METHODS: Eleven volunteers underwent ultrasound examination of both forearms. The median, ulnar, and radial nerves were followed and images were obtained at the elbow, proximal forearm, mid forearm, distal forearm and wrist levels. In addition the radial nerve was followed proximally to a point 5 cm above the elbow. Images were compared for consistency of location of the nerves and depth from skin and width was calculated for each nerve at each level. RESULTS: Anatomy of each nerve was consistent except for one forearm where the median nerve was lateral to the brachial artery at the elbow and one forearm where a superficial ulnar artery only joined the ulnar nerve at the wrist. A convenient location for blockade of both median and ulnar nerves is the midforearm combining ease of visualization, ability to block all terminal branches and minimal potential for vascular injury. The radial nerve is seen most easily at the elbow although blockade of the superficial radial nerve may spare radial motor function. CONCLUSIONS: Nerves in the forearm are consistently located using ultrasound. Further confirmation in clinical practice is required.     

Anatomic study of arborization patterns of the ulnar artery in Guyon's canal

PURPOSE: To show variations in arborization patterns of the ulnar artery in Guyon's canal and to investigate the relationship between the hypothenar muscles and the ulnar artery. METHODS: Thirty-five embalmed cadaveric hands were dissected and the existence and course of the superficial and deep palmar branches of the ulnar artery and the site of feeding branches to the hypothenar muscles were recorded. The anatomic relationship between the ulnar artery and the hypothenar muscle variations also was investigated. RESULTS: Four arborization patterns were identified. In type 1UA (n = 17 hands), an artery accompanying the deep branch of the ulnar nerve (AADBUN) formed a deep palmar arch (DPA). In type 2UA (n = 11 hands) the AADBUN continued to the feeding artery of the abductor digiti minimi and the distal deep palmar branch of the ulnar artery (DDPBUA) branched off distally. This arterial structure formed a DPA. In type 3UA (n = 6 hands) both the AADBUN and DDPBUA formed DPAs. In type 4UA(n = 1 hand), the AADBUN continued to the feeding artery of the abductor digiti minimi with no DDPBUA and therefore no DPA. A dorsal perforating artery of the ulnar artery also was found in 4 hands. This branch came from the AADBUN at the level of the distal edge of the pisiform and merged with the dorsal carpal arterial arch. We also investigated the relationship between the structural pattern of the hiatus for the deep branch of the ulnar nerve and ulnar artery variation but found no association. The most common pattern observed was a type 1 hiatus with a type 1UA arborization pattern. CONCLUSIONS: Our study confirmed considerable variations in the arborization pattern of the ulnar artery in Guyon's canal. To avoid injury to the arterial branches during surgery in this region care must be taken with respect to variations of the ulnar artery in Guyon's canal.     

Quantitation of and superficial surgical landmarks for the anterior interosseous nerve

OBJECT: There are scant data regarding the anterior interosseous nerve (AIN) in the neurosurgical literature. In the current study the authors attempt to provide easily identifiable superficial osseous landmarks for the identification of the AIN. METHODS: The AIN in 20 upper extremities obtained in adult cadaveric specimens was dissected and quantified. Measurements were obtained between the nerve and surrounding superficial osseous landmarks. The AIN originated from the median nerve at mean distances of 5.4 cm distal to the medial epicondyle of the humerus and 21 cm proximal to the ulnar styloid process. The distance from the origin of the AIN to its branch leading to the flexor pollicis longus muscle and to the point it travels deep to the pronator quadratus (PQ) muscle measured a mean 4 and 14.4 cm, respectively. The mean distance from the AIN branch leading to the flexor pollicis longus muscle to the proximal PQ muscle was 12.1 cm, and the mean distance between this branch and the ulnar styloid process was 7.2 cm. The mean diameter of the AIN was 1.6 mm at the midforearm. CONCLUSIONS: Additional landmarks for identification of the AIN can aid the neurosurgeon in more precisely isolating this nerve and avoiding complications. Furthermore, after quantitation of this nerve, the AIN branches can be easily used for neurotization of the median and ulnar nerves, and with the aid of a transinterosseous membrane tunneling technique, passed to the posterior interosseous nerve.     

How to avoid operative injury to Martin-Grüber communicating branch in the transmuscular medial approach of the elbow?

The incidence of Martin-Grüber medio-ulnar communicating branch (MUCB), from median nerve to ulnar nerve, is about 20%. To avoid operative injury to MUCB, the authors suggest some modifications to the medial approach of the elbow. They suggest medial aponeurotomy of the anterior compartment of the forearm, disinsertion of the medial epicondylar muscles with dissection between the flexor carpi ulnaris (FCU) and the other medial epicondylar muscles, not exceeding 3 cm distally. This allows a valuable exposure of the elbow joint through a medial approach, with FCU disinsertion and ulnar nerve transposition preserving the ulnar nerve vascularization, without injury to the MUCB.     

指固有神经背侧支的应用解剖学研究

目的 为指固有神经背侧支的临床应用提供解剖学基础。方法 观测12只新鲜成人手标本48个手指指固有神经背侧支出的出现率、直径、走向及分支。结果 示、中、环指及小指桡侧指固有神经发出的单一分支形成背侧支者占92．86％（78．84）,背侧支缺如者占7．14％（6．84侧）。各指背侧支均在近节手指近、中1／3平面发出,并从指侧面斜向指背远端走行。在近指间关节桡背（或尺背）侧向背面及中节指背发出2－5条分支。除小指外,2－4指指桡、尺侧背侧支的直径粗细均有显著性差异（P＜0．05）,桡侧＞尺侧。小指飞侧无指固有神经背侧支。结论 示、中、环及小指的桡侧指固有神经背侧支走向恒定,可包含在同指逆行岛状皮瓣内,适用于修复指腹软组织缺损。