Surgical anatomy of the radial nerve in the arm: practical considerations of the branching patterns to the triceps brachii

Radial Nerve Fascicular Transfer Preserving Long Head through Anterior Incision for Transhumeral Targeted Muscle Reinnervation

New developments in targeted muscle reinnervation promise better options for treatment of neuropathic pain and improved prosthetic control. For transhumeral amputations, the traditional approach involves an anterior incision to access the median and ulnar nerves and a second posterior incision to access the radial nerve. This is necessitated as exposure of motor branches of the radial nerve distal to the branch to the long head of the triceps is difficult from the anterior approach. Herein, we describe a technique for transferring the radial nerve proper distal to the long head branch to a motor branch to the medial or lateral head of the triceps through internal neurolysis and fascicular transfer. This allows all surgical steps to be performed through a single incision while preserving native motor branches to the biceps and triceps muscles.

Radial Nerve Sensory Branch Anatomical Variant: A Case Report and Literature Review

CASE

Two patients sustained comminuted extra-articular distal humerus fractures. One patient was neurovascularly intact preoperatively. The other patient had a complete radial motor palsy with preserved sensation. Intraoperatively, both exhibited anatomic variants of the radial sensory nerve of the arm that pierced the triceps rather than branching from the distal third of the radial nerve proper, as is traditionally reported.

CONCLUSIONS

Although rare, variations in the radial nerve may exist about the distal humerus. Surgeons should be aware of these variations to avoid iatrogenic injury.

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.

Anatomical Study of the Ulnar Nerve Variations at High Humeral Level and Their Possible Clinical and Diagnostic Implications

Background. Descriptive evaluation of nerve variations plays a pivotal role in the usefulness of clinical or surgical practice, as an anatomical variation often sets a risk of nerve palsy syndrome. Ulnar nerve (UN) is one amongst the major nerves involved in neuropathy. In the present anatomical study, variations related to ulnar nerve have been identified and its potential clinical implications discussed. Materials and Method. We examined 50 upper limb dissected specimens for possible ulnar nerve variations. Careful observation for any aberrant formation and/or communication in relation to UN has been carried out. Results. Four out of 50 limbs (8%) presented with variations related to ulnar nerve. Amongst them, in two cases abnormal communication with neighboring nerve was identified and variation in the formation of UN was noted in remaining two limbs. Conclusion. An unusual relation of UN with its neighboring nerves, thus muscles, and its aberrant formation might jeopardize the normal sensori-motor behavior. Knowledge about anatomical variations of the UN is therefore important for the clinicians in understanding the severity of ulnar nerve neuropathy related complications.

The tricipital aponeurosis--a reliable soft tissue landmark for humeral plating

This study aims to identify the relationship of the radial nerve as it descends across the humerus with reference to a reliable soft tissue landmark, the tricipital aponeurosis. Following cadaveric dissection of 10 adult humerii, the radial nerve was located as it crossed the lateral midsagittal point of the humeral diaphysis. A horizontal line was then subtended medially from this point to another line subtended vertically from the lateral border of the tricipital aponeurosis. The vertical distance from this intersection to the lateral apex of the aponeurosis was recorded in three positions (full flexion, 90° of flexion and full extension). The location of the radial nerve on the posterior aspect of the humeral diaphysis to the medial apex of the tricipital aponeurosis was also noted. In 90° of flexion the radial nerve at the lateral midsagittal point of the humerus was 0.9 mm proximal to the lateral apex of the tricipital aponeurosis. Flexion and extension of the elbow changed the interval to 16.3 mm (nerve proximal) in full flexion and 7.1 mm in full extension (nerve distal). On the posterior aspect of the humerus the radial nerve was 21.8 mm proximal to the medial aspect of the tricipital aponeurosis. The aponeurosis provides a reference point from which the nerve can be easily located on the lateral aspect of the humerus intraoperatively in a range of positions, whilst the medial apex provides a guide to the location of the nerve on the posterior aspect of the arm.

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.

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

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

Outcomes of nerve reconstruction for radial nerve injuries based on the level of injury in 244 operative cases

We report a single surgeon series of 244 patients with radial nerve injuries who had nerve repair, neurolysis, or nerve graft over a 17-year period. 44 patients had a Level I or infraclavicular injury, 37 had a Level II injury within the spiral groove of the humerus, 104 had a Level III injury from the lateral arm to antebrachial fossa and 64 had a Level IV injury affecting the posterior interosseous nerve. Nerve grafting was used most frequently in all groups, and was the only method of reconstruction for level II injury. At 21.5 months follow up, Level IV injuries had significantly better outcome of finger and thumb extension, while wrist extension recovered in at least 80% of the patients irrespective of the level of injury. The radial nerve recovered better if repaired or reconstructed within 5 months of injury.

Trifurcated radial nerve in the spiral groove of the humerus

A 62-year-old man presented with a nonunion of the humerus shaft. Using a standard triceps splitting approach, a longitudinal incision along the posterior aspect of the arm was created. Three independent radial nerves coursed posteriorly and inferolaterally around the humerus were identified in spiral groove. Three nerves resembled in the size, color, and course in the operative field. Although the prevalence of the anomaly is probably quite low, the possibility of identification of this anomalous condition of radial nerve should be kept in mind when performing posterior approach on the humerus.

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.

Triceps Motor Nerve Branches as a Donor or Receiver in Nerve Transfers

Objective:

The pattern of triceps innervation is complex and, as yet, has not been fully elucidated. The purposes of this study were 1) to clarify the anatomy of the triceps motor branches, and 2) to evaluate their possible uses as a donor or receiver for nerve transfer.

Methods:

The radial nerve and its motor and cutaneous branches were bilaterally dissected from the axilla and posterior arm regions of 10 embalmed cadavers.

Results:

A single branch innervates the triceps long head, whereas double innervation was identified for the lateral and medial heads. The upper branch to the lateral head originated from the radial nerve, whereas the lower branch to the lateral head stemmed from the lower medial head motor branch, which ultimately innervated the anconeus muscle. Both the long head and the upper medial head motor branches originated in the axillary region in the vicinity of the latissimus dorsi tendon.

Conclusion:

Each of the triceps’ motor branches might be used as a donor for transfer. The triceps long head motor branch should be used preferentially when the intention is to establish triceps reinnervation.

Axillary nerve repair by triceps motor branch transfer through an axillary access: anatomical basis and clinical results

Object

Grafting or nerve transfers to the axillary nerve have been performed using a deltopectoral approach and/or a posterior arm approach. In this report, the surgical anatomy of the axillary nerve was studied with the goal of repairing the nerve through an axillary access.

Methods

The axillary nerve was bilaterally dissected in 10 embalmed cadavers to study its variations. Three patients with axillary nerve injuries then underwent surgical repair through an axillary access; the axillary nerve was repaired by transfer of the triceps long head motor branch.

Results

At the lateral margin of the subscapularis muscle, the axillary nerve was found in the center of a triangle bounded medially by the subscapular artery, laterally by the latissimus dorsi tendon, and cephalad by the posterior circumflex humeral artery. At the entrance of the quadrangular space, the axillary nerve divisions were loosely connected to each other, and could be clearly separated and correctly identified. Surgery for the axillary nerve repair through the axillary access was straightforward. Eighteen months after surgery, all three patients had recovered deltoid strength to a score of M4 on the Medical Research Council scale and had improved abduction strength by 50%. No deficit was evident in elbow extension.

Conclusions

The axillary nerve and its branches can be safely dissected and repaired by triceps motor nerve transfer through an axillary access.

The combined olecranon osteotomy, lateral paratricipital sparing, deltoid insertion splitting approach for concomitant distal intra-articular and humeral shaft fractures

Fractures of the distal humerus involving the articular surface can be challenging. The complexity of these fracture patterns increases when the distal fracture is associated with a concomitant humeral shaft fracture with significant proximal extension. The combined exposure technique described here allows for consistent and controlled posterior humeral exposure proximally from the traverse of the axillary nerve to the distal trochlear tip. It is especially useful for complex segmental fracture patterns where distal intra-articular involvement is present and a single approach is desired.

Does the motor branch of the long head of the triceps brachii arise from the radial nerve?

Anatomy textbooks say that the motor branch of the long head of the triceps brachii (LHT) arises from the radial nerve. Some clinical observations of traumatic injuries of the axillary nerve with associated paralysis of the LHT have suggested that the motor branch of the LHT may arise from the axillary nerve. This anatomic study was performed, using both cadaver anatomical dissections and a surgical study, to determine the exact origin of the motor branch of the LHT. From the adult cadaver specimens (group I), 20 posterior cords were dissected from 10 subjects (eight embalmed, two fresh) using 3.5x magnification. The axillary nerve was followed from its onset to the posteromedial part of the surgical neck of the humerus and the radial nerve. We looked for the origin of the proximal branch of the LHT by a meticulous double anterior and posterior dissection. From the surgical group (group II), 15 posterior cords were dissected from 15 patients suffering from a C5-C6 injured paralysis, without paralysis of the LHT. During the surgical procedure, we looked for the origins of the motor branch of the LHT with a nerve stimulator. In group I, the motor branch of the LHT arose in 13 cases from the axillary nerve near its origin, in five cases from the terminal division of the posterior cord itself, and in two cases from the posterior cord 10 mm before its terminal division into the radial and axillary nerves. In no case did we find the motor branch of the LHT arising from the radial nerve. In eight cases, we found some accessory branches that arose near the principal branch. In group II, the motor branch of the LHT arose in 11 cases from the axillary nerve near its origin and in four cases from the terminal division of the posterior cord itself. The motor branch of the LHT never originated from the radial nerve. In four cases, we found some accessory branches that arose near the principal branch of the LHT. These results reveal that the motor branch of the LHT seems to originate most often from the axillary nerve. This contribution could be relevant for surgical treatment of traumatic nerve injuries.