Radial nerve entrapment by the lateral head of the triceps

High radial nerve entrapment neuropathy: an anatomical cadaver study and case report

BACKGROUND

The pathogenetic mechanism of high radial nerve entrapment neuropathy involves the fibrous arch of the lateral head of the triceps brachii and lateral intermuscular septum. However, the details of these anatomical structures remain unknown. We described the anatomical course of the radial nerve in the upper arm and its relationship with the lateral head of the triceps brachii and lateral intermuscular septum.

METHODS

Eleven freshly frozen cadavers (22 limbs, 7 females, and mean age: 87.3 years) were used. The elbow joint was placed at 90° flexion and a lateral incision was made. Specifically, the tendons of the lateral head of the triceps brachii, deep fascia, and lateral intermuscular septum are continuous at the attachment and form a complex. The radial nerve runs obliquely through the fibrous tunnel formed by this complex, and the entry and exit portions form fibrous arches. Additionally, the distance from the lateral humeral epicondyle to the entrance (X1) and exit (X2) of the fibrous tunnel and fibrous tunnel length were measured. The tunnel was incised and the radial nerve was exposed. Specifically, the radial nerve was observed from the lateral aspect of the humerus. R1, R2, and R3 were defined as the points where the radial nerve crosses the posterior aspect, lateral center, and anterior aspect of the humeral shaft, respectively. Their distances from the lateral humeral epicondyle were also measured.

RESULTS

The distance from the lateral humeral epicondyle to X1 and X2 was 145 ± 15 (121-185) and 91 ± 14 (72-122) mm, respectively, while the fibrous tunnel length was 55 ± 12 (28-83) mm. Additionally, the distances from the lateral epicondyle to R1, R2, and R3 were 143 ± 18 (103-177), 107 ± 13 (75-142), and 79 ± 14 (59-105) mm, respectively. No significant correlation was found between the humeral and tunnel lengths.

CONCLUSION

The lateral head of the triceps brachii and lateral intermuscular septum form a complex that creates a fibrous tunnel. Additionally, the radial nerve traverses obliquely within this fibrous tunnel on the humerus, forming fibrous arches at both its entrance and exit. The lateral head of the triceps brachii-lateral intermuscular septum complex can be a source of compression in cases of high radial nerve entrapment neuropathy. Such neuropathy may result from a plane of compression. Therefore, we advocate for surgery in high radial nerve entrapment neuropathy cases that are resistant to conservative treatment. Dissecting the entire length of the fibrous tunnel is also important during surgery.

Radial nerve compression: anatomical perspective and clinical consequences

The radial nerve is the biggest branch of the posterior cord of the brachial plexus and one of its five terminal branches. Entrapment of the radial nerve at the elbow is the third most common compressive neuropathy of the upper limb after carpal tunnel and cubital tunnel syndromes. Because the incidence is relatively low and many agents can compress it along its whole course, entrapment of the radial nerve or its branches can pose a considerable clinical challenge. Several of these agents are related to normal or variant anatomy. The most common of the compressive neuropathies related to the radial nerve is the posterior interosseus nerve syndrome. Appropriate treatment requires familiarity with the anatomical traits influencing the presenting symptoms and the related prognoses. The aim of this study is to describe the compressive neuropathies of the radial nerve, emphasizing the anatomical perspective and highlighting the traps awaiting physicians evaluating these entrapments.

Radial nerve recovery following closed nailing of humeral shaft fractures without radial nerve exploration: A retrospective study

BACKGROUND

Radial nerve palsy due to humeral shaft fracture is the most common peripheral nerve injury associated with long bone fractures. An antegrade nailing surgical technique is becoming popular for the fixation of these fractures with minimal invasiveness. We analyzed nerve recovery in patients with humeral shaft fracture and radial nerve palsy treated with humeral nail fixation without nerve exploration.

AIM

To assess the radial nerve recovery rate and time from humeral shaft fracture with surgical treatment using close nailing.

METHODS

We retrospectively collected data of patients who underwent undergone surgical nail fixation for humeral shaft fractures between October 1, 2016, and March 31, 2020. Subsequently, we analyzed the primary or secondary radial nerve palsy recovery rate and radial nerve motor function recovery time.

RESULTS

The study included 70 patients who underwent surgical treatment for closed- or Gustilo type I open humeral shaft fractures using a nail fixation technique without radial nerve exploration. The patients suffered from primary (n = 5) and secondary (n = 5) radial nerve palsy. A 100% radial nerve recovery rate was achieved. The mean recovery time was 4.3 mo.

CONCLUSION

The study results indicate full recovery of radial nerve palsies from humeral shaft fracture using close nailing treatment. Surgeons need not be concerned about the occurrence of permanent nerve palsies.

Atraumatic proximal radial nerve entrapment. Illustrative cases and systematic review of literature

PURPOSE

The aims of the present study were to describe atraumatic proximal radial nerve entrapment (PRNE) and potential strategies for management.

MATERIALS AND METHODS

We performed a comprehensive search of 4 electronic databases for studies pertaining to patients with atraumatic PRNE. Studies published between 1930 and 2020 were included. Clinical presentation, nerve conduction studies, electromyography, and treatment methods were reviewed. In order to outline management strategies, 2 illustrative cases of acute PRNE were presented.

RESULTS

We analyzed 12 studies involving 21 patients with 22 PRNE (15 acute and 7 progressive). Sudden or repetitive elbow extension with forceful muscle contraction (n = 16) was the primary mechanism of injury. The two main sites of entrapment were the fibrous arch (n = 7) and hiatus of the lateral intermuscular septum (n = 7). Conservative treatment was performed in 4 patients and allowed for complete clinical recovery in all cases. The remaining 18 patients underwent epineurolysis (n = 16) or resection/repair of hourglass-like constriction (n = 2) between 1.5- and 120-months following diagnosis. Twelve patients experience complete recovery, while partial or no clinical recovery was reported in 1 and 4 cases, respectively; the outcome was unknown in 1 case.

CONCLUSIONS

Atraumatic PRNE is rare and remains challenging with respect to diagnosis and treatment. Current literature suggests that primary sites of entrapment are the fibrous arch and hiatus of the radial nerve at the time of forceful elbow extension.

LEVEL OF EVIDENCE

Case series (IV) & systematic review (I).

Surgical treatment of hourglass-like radial nerve constrictions

INTRODUCTION

Spontaneous radial nerve palsy with the surgical revelation of an hourglass-like constriction is a complicated condition. In general, the surgical strategy is decided in accordance with the results of surgical exploration. This study aimed to investigate the efficacies of various choices of surgical methods in the treatment of hourglass-like radial nerve constrictions.

MATERIAL AND METHODS

Ten patients with spontaneous radial nerve palsy undergoing surgical exploration with the revelation of hourglass-like constrictions between November 2010 and December 2018 were reviewed in our hospital. Preoperative physical, electrophysiological and ultrasound examinations were performed for all patients. Varying levels, degrees and numbers of radial nerve constrictions were shown by surgical exposure. Epineurectomy and interfascicular neurolysis were performed in 4 cases with incomplete constrictions; resection and primary suture repair in 2 radial nerves with neurotmesis; resection and autologous nerve grafting in 4 patients with nerve defect>2cm. Both motor and sensory evaluations were performed at a follow-up visit.

RESULTS

Ten patients underwent different history before the onset of symptom. Nerve ultrasound demonstrated swelling as well as constrictions of the radial nerve. All patients who were followed up presented with good to excellent recovery of motor function. The effectiveness of suture and autograft repair tended to be better than that of simple neurolysis.

CONCLUSION

The etiology of hourglass-like fascicular constrictive neuropathy of radial nerve involve with torsional factors. Nerve ultrasound is an important and useful measurement in diagnosing the pathology of spontaneous radial nerve palsy and in helping determine surgical approach. The surgical intervention is beneficial for the patients who do not recover in 4 weeks after onset of symptoms and for severe hourglass-like constrictions that are confirmed by preoperative ultrasound imaging. We recommend that nerve grafting be a suitable method in confrontation of nerve defect>2cm.

Spontaneous Radial Nerve Palsy due to an Unrecognized Myofibroma: A Case Report

CASE

A 33-year-old woman presented with a six-month history of spontaneous radial nerve palsy and no identified lesion on imaging. She underwent operative exploration where an hourglass deformity was seen and resected. Pathology returned as a rare tumor, a myofibroma. The patient regained full radial nerve function.

CONCLUSIONS

A trial of observation is often indicated in the cases of isolated nerve palsy where anatomic lesions have been eliminated. This case highlights that imaging studies can miss a tumor involving nerve and that painless, spontaneous nerve palsy may be a time where early surgical intervention offers a better chance of recovery.

Injury of the Radial Nerve in the Arm: A Review

Compression of the radial nerve is most commonly described at the supinator muscle (i.e., arcade of Frohse). However, radial nerve compression can occur in the arm. Therefore, the purpose of this article is to review both etiologies of radial nerve entrapment and the sites at which this can occur in the arm. The clinical presentation of radial nerve entrapment in the arm and how it differs from that of entrapment at other sites is reviewed and the conditions potentially predisposing to nerve entrapment are described. Particular attention is paid to the nerve’s course and potential variants of the anatomical structures in the arm. In each case, the recommended course of management for the neuropathy is described. Injury of the radial nerve can arise from a varied set of pathologies including trauma, tumors, anomalous muscles, and intramuscular injections. Physicians should have a good working knowledge of the anatomy and potential mechanisms for radial nerve injury.

The humeral origin of the brachioradialis muscle: an unusual site of high radial nerve compression

Radial nerve compression is seldom encountered in the upper arm, and most commonly described compression syndromes have their anatomical cause in the forearm. The teres major, the triceps muscle, the intermuscular septum region and the space between the brachialis and brachioradialis muscles have all been identified as radial nerve compression sites above the elbow. We describe the case of a 38-year-old male patient who presented with dorso-lateral forearm pain and paraesthesias without neurological deficit. Surgical exploration revealed radial nerve compression at the humeral origin of the brachioradialis muscle. Liberation of the nerve at this site was successful at relieving the symptoms. To our knowledge, this compression site has not been described in the literature.

Compression and entrapment neuropathies

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

Surgical anatomy of the radial nerve at the elbow

An anatomical study of the brachial portion of the radial nerve with surgical implications is proposed. Thirty specimens of arm from 20 fresh cadavers (11 male, 9 female) were used to examine the topographical relations of the radial nerve with reference to the following anatomical landmarks: acromion angle, medial and lateral epicondyles, point of division between the lateral and long heads of the triceps brachii, lateral intermuscular septum, site of division of the radial nerve into its superficial and posterior interosseous branches and entry and exit point of the posterior interosseous branch into the supinator muscle. The mean distances between the acromion angle and the medial and lateral levels of crossing the posterior aspect of the humerus were 109 (+/-11) and 157 (+/-11) mm, respectively. The mean length and calibre of the nerve in the groove were 59 (+/-4) and 6 (+/-1) mm, respectively. The division of the lateral and long heads of the triceps was found at a mean distance of 126 (+/-13) mm from the acromion angle. The mean distances between the lateral point of crossing the posterior aspect of the humerus and the medial and lateral epicondyles were 125 (+/-13) and 121 (+/-13) mm, respectively. The mean distance between the lateral point of crossing the posterior aspect of the humerus and the entry point in the lateral intermuscular septum (LIS) was 29 (+/-6) mm. The mean distances between the entry point of the nerve in the LIS and the medial and lateral epicondyles were 133 (+/-14) and 110 (+/-23) mm, respectively. Our study provides reliable and objective data of surgical anatomy of the radial nerve which should be always kept in mind by surgeons approaching to the surgery of the arm, in order to avoid iatrogenic injuries.

Radial nerve compression between the brachialis and brachioradialis muscles in a manual worker: a case report

We report a case of high right radial nerve palsy in which the nerve was compressed between the brachialis and brachioradialis muscles.

Triceps brachii muscle demonstrating a fourth head

Variations of the triceps brachii muscle are apparently rare. We report an additional attachment site of the medial head of the triceps brachii found on the left side of a male cadaver. This head originated from the posterior aspect of the surgical neck of the humerus. Clinicians diagnosing or treating patients with weakness or pain of the posterior arm should consider anomalous muscles in this region that may result in neurovascular compression.

Anatomy of nerve entrapment sites in the upper quarter

The purpose of this article is to review the anatomical features of the most common nerve entrapment sites of the brachial plexus and major peripheral nerves of the upper limb. In this account, the term "entrapment" is considered to be caused by compression, tension, or friction, or any combination of these factors. The anatomy, including important relationships of the brachial plexus, is reviewed and the points of potential entrapment of the plexus are described. Entrapment of the suprascapular and long thoracic nerves is also included. Particular attention is paid to the five major peripheral nerves that result from the brachial plexus and supply the peripheral aspect of the upper limb, i.e., the median, ulnar, musculocutaneous, radial, and axillary nerves. In each case, the nerve's course is described and the anatomical details of the entrapment points described. Where possible, the sites of entrapment are illustrated in cadaveric photographs.

Radial nerve palsy associated with humeral shaft fracture: evaluation with US--initial experience

PURPOSE

To determine the feasibility of using ultrasonography (US) for evaluation of a radial nerve injury associated with humeral shaft fracture.

MATERIALS AND METHODS

In a prospective study, 11 consecutive patients with sensorimotor radial deficiency after distal humeral fracture were evaluated with conventional radiography, US, electroneurography, and electromyography. Surgical repair of the fracture and nerve inspection were performed in five patients. The remaining six patients were successfully treated conservatively. The US appearance of the radial nerve was studied in 10 healthy volunteers and in the noninjured arm of the 11 patients for comparison.

RESULTS

In five patients, US findings of a severely damaged radial nerve were confirmed at surgical nerve inspection. In one patient, the nerve was entrapped between fragments. One patient had a complete nerve dissection, one had a lacerated nerve from a loose compression plate, and one had a nerve riding on the edge of a bone fragment. In the fifth patient who underwent surgical inspection, the nerve was buried in the callus. In the six patients treated conservatively, US showed continuity of the nerve.

CONCLUSION

US may be useful for accurate evaluation of the radial nerve in patients with nerve palsy associated with humeral shaft fracture.

Radial nerve entrapment in the upper arm as a cause of lateral arm pain: a report of four cases

Four patients with no history of trauma presented with lateral arm pain, local tenderness, and a tingling sensation at the distal end of the arm when the radial nerve was percussed in the mid-third of the upper arm (Tinel's sign), but no clinical or subjective signs of muscular weakness. They were treated by decompression of the radial nerve in the fibrous canal proximal to the lateral intermuscular septum. Three of the patients had a complete or pronounced reduction in pain, while the fourth had only a slight improvement. Non-traumatic radial nerve entrapment in the upper arm may be the cause of lateral arm pain without clinical signs of muscular weakness.

Radial nerve palsy caused by spontaneously occurring nerve torsion. Case report

An 18-year-old man presented with a spontaneously occurring radial nerve palsy that spared the triceps muscle. At surgery, the portion of the radial nerve located at the midarm level had an hourglass-like appearance. Under magnification, an external-internal neurolysis of the narrowed portion of the hourglass-shaped portion revealed nerve torsion. Straightening of the twisted nerve and fixation accomplished using epiperineurium-fascia stitches to avoid a new torsion resulted in complete functional recovery of the radial nerve.

Variation in the triceps brachii muscle: a fourth muscular head

Routine cadaver dissection has resulted in the identification of a fourth head of the triceps brachii muscle on the left side in one specimen. This novel arrangement demonstrated a single tendon arising from the proximal posteromedial aspect of the humeral shaft, distal to the shoulder capsule. The tendon of this fourth head passed along the medial aspect of the humerus and gave way to a muscle belly on the medial surface of the distal one-third of the humerus. The tendon of the fourth head passed directly over the neurovascular bundle containing the radial nerve and deep brachial artery at approximately the point where the neurovascular bundle entered the radial sulcus. This close positional relationship between the tendon of the fourth head, the radial nerve, and the deep brachial artery has prompted us to speculate on the possible clinical significance of this finding in relation to radial nerve palsy and arterial compression. Additionally, the position of the muscle belly, lying in close proximity to the ulnar groove, invites speculation on the role of the fourth head in cases of snapping elbow. To the authors' knowledge, a description of the muscular fourth head of the triceps as seen in the present work has not been noted in previous literature.

Radial neuropathy

The radial nerve is the largest branch of the brachial plexus, and is commonly involved in upper extremity mononeuropathies. The radial nerve is primarily responsible for motor innervation of the upper extremity extensors, as well as receiving cutaneous innervation from most of the posterior arm, forearm, and hand. There are a variety of sites at which the radial nerve is susceptible to trauma and entrapment. Localizing radial nerve lesions is dependent on clinical knowledge of radial nerve anatomy, and sensory and motor examination.

Radial tunnel syndrome. A retrospective review of 30 decompressions of the radial nerve

Radial tunnel syndrome results from compression of the radial nerve by the free edge of the supinator muscle or closely related structures in the vicinity of the elbow joint. Despite numerous reports on the surgical management of this disorder, it remains largely unrecognized and often neglected. The symptoms of radial tunnel syndrome can resemble those of tennis elbow, chronic wrist pain or tenosynovitis. Reliable objective criteria are not available to differentiate between these pathologies. These difficulties are discussed in relation to 29 patients who underwent 30 primary explorations and proximal decompressions of the radial nerve. Excellent or good results were obtained in 70%, fair results in 13% and poor results in 17% of patients. The results can be satisfactory despite the prolonged duration of symptoms. We believe that a diagnosis of radial tunnel syndrome should always be born in mind when dealing with patients with forearm and wrist pain that has not responded to more conventional treatment. Patients with occupations requiring repetitive manual tasks seem to be particularly at risk of developing radial tunnel syndrome and it is also interesting to note that 66% of patients with on-going medico-legal claims had successful outcomes following surgery.

[Radial paralysis of the arm after muscular effort. 4 case reports. Clinical and physiopathological study]

Radial palsy following muscular effort is uncommon and often related to a fibrous arch at the lower part of the humeral groove; they usually resolve spontaneously. In the absence of improvement, operation consists of neurolysis and resection of the fibrous arch; nerve graft is rarely necessary even in cases of severe hourglass compression.