The anatomy of the distal ulnar tunnel

The distal ulnar tunnel is a region of the wrist 4-4.5 cm in length in which the ulnar nerve is particularly vulnerable to external compression. The relation of the internal topography of the nerve to the structures comprising the tunnel provides a basis for dividing the tunnel into three zones. Zone 1 is that portion of the tunnel proximal to the bifurcation of the ulnar nerve. Zone 2 encompasses the deep motor branch of the nerve, and Zone 3 surrounds the superficial branch. A review of the literature of ulnar nerve compression lesions confirmed expectations based on the regional anatomy. Zone 1 lesions included all (39) cases of combined motor and sensory deficits, one case of pure motor paralysis, and seven cases of sensory deficits. All Zone 2 lesions (36 cases) resulted in paralysis of the intrinsic muscles. Whether or not the hypothenar muscles were affected was dependent upon the location of the lesions within Zone 2. Zone 3 lesions caused sensory deficits only. Combined motor and sensory loss was most often caused by compression from deep to the nerve, while pure sensory deficits were a result of compression lesions lying superficial to the nerve.     

End-to-side nerve graft repair based on synergistic peripheral terminal motor branches: investigation in a nonhuman primate model

Summary BACKGROUND: Spinal nerve avulsion frequently occurs in brachial plexus injury, becoming irreparable lesions. Nerve transfer at the very proximal site within a limited time interval after injury leads to satisfactory functional results. Oberlin reported a neurotization technique at a more peripheral location. Hypothetically, there might be useful functional results performing very peripheral end-to-side nerve graft repair using synergistic tiny terminal motor branches. We created one possible application of such a peripheral synergistic terminal end-to-side nerve transfer in a median nerve defect model in nonhuman primates. An end-to-side nerve graft repair bridging from the terminal motor branch of deep branch of the ulnar nerve to the thenar motor branch of median nerve was performed. The purpose of this study was to investigate the efficacy of this hypothesis. METHODS: Seven adult baboons were used in this study. At baseline, we electrophysiologically demonstrated no variation in innervation of median- and ulnar-nerve-innervated thenar muscles. Transection of the median nerve was performed. Subsequently, the abductor pollicis brevis muscle could neither be stimulated by the median nerve nor by the ulnar nerve. Baboons underwent end-to-side coaptation of a nerve graft to the deep branch of the ulnar nerve and end-to-end coaptation to the thenar motor branch of the median nerve. Assessment of functional recovery was performed by electrophysiological evaluation, thenar muscle weight, and video slow-motion analysis. RESULTS: All animals recovered opposition of the thumb 3 months after surgery. The abductor pollicis brevis muscle, preoperatively innervated by the median nerve, did not respond to electrophysiological stimulation of the transected median nerve but to stimulation of the ulnar nerve via the nerve graft. Length of nerve graft (in average 2.3 cm) showed no correlation to muscle weight or electrophysiological parameters. CONCLUSIONS: The results in this series demonstrate the efficacy of end-to-side nerve graft repair at the level of tiny very peripheral terminal motor branches in a nonhuman primate median nerve defect model. Applications of this technique may enhance functional results by avoidance of time-dependent end organ failure.      

Isolated laceration to the deep motor branch of the ulnar nerve by a retained foreign body

This report describes an isolated laceration to the deep motor branch of the ulnar nerve by a retained foreign body. The patient sustained a laceration on the ulnar, volar aspect of his palm after a fall on gravel. He presented to the emergency room with motor deficits but a normal sensory examination. No foreign bodies were identified on initial wound exploration or review of plain radiographs, and the patient's wound was sutured closed without diagnosing the nerve injury or the retained foreign body. Confusion over the patient's intact sensory examination and lack of awareness of the complex distal anatomy of the ulnar nerve contributed to the misdiagnosed nerve lesion. Isolated injuries of the deep motor branch are very rare, but increased awareness and understanding of the complex ulnar nerve distal anatomy will help avoid future delays in diagnosis and treatment.     

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.     

Selective restoration of motor function in the ulnar nerve by transfer of the anterior interosseous nerve. An anatomical feasibility study

BACKGROUND: Proximal ulnar-nerve lesions have an unfavorable prognosis. The goal of the present study was to evaluate the feasibility of selective restoration of motor function of the ulnar nerve by the transfer of the anterior interosseous nerve or one of its branches to the motor branch of the ulnar nerve. METHODS: Ten cadaveric arms were used in the present study. The ulnar nerve and its motor and sensory branches as well as the anterior interosseous nerve and its branches were dissected. The widths of the motor branch of the ulnar nerve and the anterior interosseous nerve and its motor branches as well as the relevant distances from the points of divergence were measured. The axons were counted, and the distances from the end of the main anterior interosseous nerve, its motor branches, and the motor branch of the ulnar nerve to the level of the dorsal sensory branch of the ulnar nerve were measured. RESULTS: Our results indicate that the length, width, and number of axons of the branch of the anterior interosseous nerve to the pronator quadratus make it suitable for transfer to the motor branch of the ulnar nerve. The use of the main anterior interosseous nerve or its motor branches to the flexor pollicis longus and the flexor digitorum profundus is less feasible because of the need to graft a long segment and the longer distance from the level of transfer to the motor end points. CONCLUSIONS: The findings of the present study confirm the feasibility of motor-nerve transfer for reconstruction after an injury of the ulnar nerve. Nerve-grafting would be needed for injuries distal to the level of the dorsal sensory branch of the ulnar nerve.     

正中神经指浅屈肌肌支移位修复尺神经运动支的应用解剖

目的 通过对正中神经指浅屈肌肌支和尺神经运动支的解剖学研究,为正中神经指浅屈肌肌支移位修复尺神经运动支,恢复手内在肌功能的临床应用提供解剖学基础.方法 选用20例40侧近期经福尔马林浸泡固定的成人上肢标本,暴露正中神经、尺神经,测量正中神经指浅屈肌肌支各项解剖学数据;应用图像分析系统对组织切片做定量分析,测算该肌支有髓神经纤维数目.临床模拟操作正中神经指浅屈肌肌支移位修复尺神经运动支.结果 正中神经第4肌支发出部位距离桡骨茎突和尺骨茎突连线(48.4±2.4)mm,入肌部位距离桡骨茎突和尺骨茎突连线(21.4±1.8)mm,可分离长度(27.1±1.2)mm,横径(1.2±0.2)mm,前后径(0.7±0.1)mm;尺神经的运动支和感觉支之间自然分束无损伤分离.长度为(7.1±0.70)cm;组织切片及图片系统测得正中神经指浅屈肌第4肌支有髓神经纤维数目为(1378.9±107.9)条.结论 正中神经指浅屈肌第4肌支可修复尺神经运动支,以期恢复手内在肌的功能.     

Ulnar Nerve Innervation of the Triceps Muscle: Real or Apparent? An Anatomic Study

Background

Since the 18th century, the existence of ulnar nerve innervation of the medial head of the triceps brachii muscle has been controversial. The evidence for or against such innervation has been based on macroscopic dissection, an unsuitable method for studying intraneural topography or intramuscular branching. The study of smaller specimens (embryos or fetuses) by means of serial histologic sections may resolve the controversy.

Questions/Purposes

Using fetal specimens and histology we determined the contributions of the ulnar and radial nerves to innervation of the triceps brachii muscle.

Methods

We histologically examined 15 embryonic and fetal arms. Radial nerve branches obtained from six adult arms were analyzed immunohistochemically to determine motor fiber content.

Results

The medial head of the triceps brachii muscle was always innervated by the radial nerve (ulnar collateral branch). The branches seeming to leave the ulnar nerve at elbow level were the continuation of the radial nerve that had joined the ulnar nerve sheath via a connection in the axillary region. Immunohistochemistry revealed motor and nonmotor fibers in this radial nerve branch.

Conclusions

A connection between the radial and ulnar nerves sometimes may exist, resulting in an apparent ulnar nerve origin of muscular branches to the medial head of the triceps, even though in all our specimens the fibers could be traced back to the radial nerve.

Clinical Relevance

Before performing or suggesting new muscle and nerve transpositions using this apparent ulnar innervation, the real origin should be confirmed to avoid failure.     

Case report: Double nerve transfer of the anterior and posterior interosseous nerves to treat a high ulnar nerve defect at the elbow

Double neurotization of the deep branch of ulnar nerve (DBUN) and superficial branch of ulnar nerve using the anterior interosseous nerve (AIN) and the recurrent (thenar) branch of the median nerve was first described by Battiston and Lanzetta. This article details the postoperative results after 18 months of a patient who underwent this technique using the posterior interosseous nerve (PIN) instead of the recurrent branch of the median nerve for sensory reconstruction. A 35-year-old, right-handed man suffered major trauma to his right upper limb following a serious motor vehicle accident. One year later, a pseudocystic neuroma of the ulnar nerve was evident on ultrasound examination and MRI. After the neuroma had been resected, the nerve defect was estimated at 8 cm. One and a half years after the initial trauma, with the patient still at M0/S0, we transferred the AIN and PIN onto the deep and superficial branches of the ulnar nerve respectively. Nerve recovery was monitored clinically every month and by electromyography (EMG) every three months initially and then every six months. At 18 months postoperative, 5th digit abduction/adduction was 28 mm. Sensation was present at the base of the 5th digit. The patient was graded M3/S2. Clear re-innervation of the abductor digiti minimi was demonstrated by EMG (motor conduction velocity 50 m/s). Given that the ulnar nerve could not be excited at the elbow, this re-innervation had to be the result of the double nerve transfer. Neurotization of the DBUN using the AIN produces functional results as early as 1 year after surgery. Using PIN for sensory neurotization is easy to perform, has no negative consequences for the donor site, and leads to good recovery of sensation (graded as S2) after 18 months.     

Cortical brain mapping of peripheral nerves using functional magnetic resonance imaging in a rodent model

The regions of the body have cortical and subcortical representation in proportion to their degree of innervation. The rat forepaw has been studied extensively in recent years using functional magnetic resonance imaging (fMRI), typically by stimulation using electrodes directly inserted into the skin of the forepaw. Here we stimulate the nerve directly using surgically implanted electrodes. A major distinction is that stimulation of the skin of the forepaw is mostly sensory, whereas direct nerve stimulation reveals not only the sensory system but also deep brain structures associated with motor activity. In this article, we seek to define both the motor and sensory cortical and subcortical representations associated with the four major nerves of the rodent upper extremity. We electrically stimulated each nerve (median, ulnar, radial, and musculocutaneous) during fMRI acquisition using a 9.4-T Bruker scanner (Bruker BioSpin, Billerica, MA). A current level of 0.5 to 1.0 mA and a frequency of 5 Hz were used while keeping the duration constant. A distinct pattern of cortical activation was found for each nerve that can be correlated with known sensorimotor afferent and efferent pathways to the rat forepaw. This direct nerve stimulation rat model can provide insight into peripheral nerve injury.     

The cutaneous innervation of the dorsal hand: detailed anatomy with clinical implications

PURPOSE: Detailed knowledge of the anatomy of the cutaneous innervation to the dorsal surface of the hand is valuable information. Because surgical access to the wrist often is obtained via the dorsal skin it would be helpful particularly to delineate an area where surgical incisions would not injure underlying nerves. METHODS: Thirty cadaver forearms were dissected carefully to examine in detail the anatomy of the lateral antebrachial cutaneous nerve, the superficial branch of the radial nerve, and the dorsal branch of the ulnar nerve. Each hand then was evaluated for an area free of any major nerve branches over the dorsal wrist. RESULTS: Although the innervation to the dorsal hand varies certain patterns exist. The innervation pattern between the superficial branch of the radial nerve and the dorsal branch of the ulnar nerve is distributed evenly, dual innervation is frequent between the 2 nerves, and the lateral antebrachial cutaneous nerve is a common contributor to the innervation of the thumb. The superficial branch of the radial nerve and the dorsal branch of the ulnar nerve have identifiable branching patterns and have been classified according to a system developed for this study. CONCLUSIONS: Two classification systems based on detailed dorsal hand cutaneous innervation patterns can be used to specify the placement of a safe dorsal skin incision away from major nerve branches.     

A variant of Kaplan's accessory branch of the dorsal cutaneous branch of the ulnar nerve: a case report and review of the literature

Kaplan's accessory branch is an aberrant branch of the dorsal cutaneous branch of the ulnar nerve that arises proximal to the styloid process of the ulna and courses ulnar to the pisiform. Variations of this anomaly have been described as having an end point of connection to the sensory branch of the ulnar nerve, to the motor branch of the ulnar nerve (rare), to the digital nerve at the level of the midhypothenar eminence, or to the proximal interphalangeal joint of the small finger or as running as an independent branch to the volar aspect of the small finger. We report a variant of Kaplan's accessory branch that coursed through the insertion of the flexor carpi ulnaris, a groove on the ulnar aspect of the pisiform, and connected to the ulnar nerve trunk proximal to its bifurcation into its motor and sensory branch. Based on the findings of the case presented and a review of the literature we offer a classification system for this anomaly.     

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.     

A neural loop of the deep motor branch of the ulnar nerve: an anatomic study

A motor neural loop of the deep branch of the ulnar nerve was encountered on three occasions during neurolysis of the ulnar nerve through Guyon's canal. An anatomic study of the course of the deep motor branch of the ulnar nerve at the wrist was done to define the incidence of this neural loop. Seventy-seven cadaveric upper extremities were examined and seven (9%) cases of a neural loop were encountered. One of these cases was bilateral. This variation should be considered when there is an atypical clinical presentation after penetrating injuries or compression neuropathy of the ulnar nerve at the wrist. In addition, care must be taken not to injure this branch during decompression of Guyon's canal or excision of an ununited of the hook of the hamate.     

A Cadaveric Study of Ulnar Nerve Innervation of the Medial Head of Triceps Brachii

The presence of a separately innervated muscle unit of the triceps may have possible surgical importance and can be used for motor reconstructions. The ulnar nerve is closely situated to the triceps muscle and rarely examined above the elbow. The aim of this cadaveric study was to explore a possible contribution of the ulnar nerve to motor innervation of the medial head of the triceps. We dissected 18 limbs from axillae to midforearm. The path of the ulnar nerve was followed, and examination was conducted of attachments to the triceps. Gross photographs were taken and samples histologically stained. Seventeen limbs had ulnar nerve branches proximal to the epicondyles that inserted on the medial head. Eleven of these branches were from the ulnar nerve trunk. The other six were nerve branches from the ulnar collateral branch of the radial nerve. The ulnar nerve and the ulnar collateral branch of the radial nerve are previously unrecognized sources of innervation of the medial head of the triceps brachii. These motor branches must be carefully preserved during the medial surgical approach above the elbow. The ulnar innervated part of the medial head of the triceps muscle may be used like an independent motor unit. Each author certifies that he or she has no commercial association (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.     

Distal anterior interosseous nerve transfer to the deep motor branch of the ulnar nerve for reconstruction of high ulnar nerve injuries

Proximal ulnar nerve injuries can result in loss of intrinsic muscle function of the hand, and distal nerve transfers provide nerve coaptation close to the target muscle. This retrospective chart review evaluated patient outcome following a distal nerve transfer of the anterior interosseous nerve (AIN) to the deep motor branch of the ulnar nerve. There were eight patient charts reviewed, three women, and five men. The mean patient age was 38 years (standard deviation: 22 years). The mean time from injury to surgery was 3 months (standard deviation: 3 months), and mean postoperative follow-up time was 18 months (standard deviation: 11 months). All patients had reinnervation of the ulnar nerve intrinsic hand muscles with improved postoperative lateral pinch and grip strength. One patient had a secondary tendon transfer. No functional deficit in performing tasks in pronation was reported. The distal nerve transfer of the AIN to the deep motor branch of the ulnar nerve provides good reinnervation of the ulnar-nerve-innervated intrinsic muscles of the hand.     

Case report: intraneural ganglion cyst of the ulnar nerve at the wrist

We report a case of a 69-year-old male who presented with pain, weakness, and clumsiness of his right hand. Initial evaluation suggested possible neoplastic process affecting his cervical spine, which was fortunately ruled out by bone biopsy. Subsequent electrodiagnostic studies and magnetic resonance imaging confirmed a lesion of the deep ulnar motor branch. Exploration of Guyon’s canal was performed, and an intraneural ganglion involving the deep motor branch of the ulnar nerve was found and excised. Despite more than 14 months of symptomatic duration, the patient made a near-complete recovery with virtually no functional limitations. This provides supporting evidence for a functional benefit of intraneural ganglion excision and nerve decompression even in cases of chronic muscle atrophy.     

Mononeuropathy of the deep motor palmar branch of the ulnar nerve: report of two unusual cases

Abstract Two female patients with lesions of the deep motor branch of the ulnar nerve are presented. In the first, a 40-year-old woman, the lesion was provoked by the stereotyped professional activity (screwing lids). In the second, aged 50 years, the nerve was damaged by a strike from a tennis ball. In both patients, we observed atrophy of the dorsal interosseous muscle. Hypothenar muscles and sensitivity were spared. Motor and sensory conduction velocities of the ulnar nerve were normal. Both patients recovered well in a few months.     

Muscle preservation by prolonged sensory protection

The functional recovery of a muscle target following nerve repair is inversely related to the denervation time: i.e., the longer the muscle denervation, the poorer the functional outcome following nerve reconstruction. The trophic and protective effects of sensory innervation to a motor nerve, following prolonged denervation (greater than 6 months), have been studied. Following proximal transection of the musculocutaneous nerve (MC) close to its C6 origin in 10 adult male Sprague-Dawley rats, the severed nerve was coapted to supraclavicular purely sensory nerves originating from C3 and C4 (sensory protection [SP] group). In another 10 Sprague-Dawley rats, the transected MC nerve was not protected by coaptation to sensory nerves (control group). After prolonged denervation or "sensory protection" (6 months), the MC nerve was then coapted in both groups to the purely motor medial pectoral nerve. Behavioral testing (grooming test) was performed on a weekly basis during the reinnervation time, which lasted 4 weeks. Statistically significant differences (p<0.05) favoring the SP group, were found at the second week of the reinnervation period, but not at the end of the experiment. Evaluation also included intraoperative electrical stimulation of the MC nerve, biceps muscle dry weights, motor endplate counts, and nerve axon counts of the MC nerve. The biceps muscle dry weights were statistically higher in the SP group, along with a trend for a higher number of motor endplates. No statistically significant difference was found in the nerve axon counts of the MC nerve between the two groups. Statistically better intraoperative electrical stimulation results were also encountered in the sensory protection group. An interpretation of the results favors the hypothesis that sensory reinnervation of a motor target may provide the necessary trophic environment to minimize muscle atrophy, until a motor donor nerve becomes available.