Current concepts of surgical approach for radial nerve entrapment around the elbow.

Radial nerve entrapment is an uncommon diagnosis. The entrapment can occur at any location within the course of the nerve distribution, but the most frequent location of entrapment occurs around the elbow and involves the posterior interosseous nerve. Several potential sites of radial nerve entrapment around the elbow are identified: the capsular tissue of the radiocapitellar joint; hypertrophic crossing branches of leash of henry; the leading proximal tendinous and medial edge of extensor carpi radialis brevis; the arcade of Frohse and distal border of the supinator between its two heads. The arcade of Frohse is the most common site of compression. The aim of this manuscript is to describe the common surgical methods to approach the radial nerve entrapments around the elbow and define the preferred surgical approach based on the site of compression.

Deep branch of the radial nerve: effect of pronation/supination on longitudinal nerve alignment.

OBJECTIVE: To evaluate the effect of maximal pronation and supination of the forearm on the alignment and anatomic relationship of the deep branch of the radial nerve (DBRN) at the superior arcade of the supinator muscle (SASM) by using high-resolution ultrasound (HRUS). MATERIALS AND METHODS: In this cross-sectional study, HRUS in the long axis of the DBRN was performed in asymptomatic participants enrolled from March to August 2021. DBRN alignment was evaluated by measuring angles of the nerve in maximal pronation and maximal supination of the forearm independently by two musculoskeletal radiologists. Forearm range of motion and biometric measurements were recorded. Student t, Shapiro-Wilk, Pearson correlation, reliability analyses, and Kruskal-Wallis test were used. RESULTS: The study population included 110 nerves from 55 asymptomatic participants (median age, 37.0 years; age range, 16-63 years; 29 [52.7%] women). There was a statistically significant difference between the DBRN angle in maximal supination and maximal pronation (Reader 1: 95% CI: 5.74, 8.21, p < 0.001, and Reader 2: 95% CI: 5.82, 8.37, p < 0.001). The mean difference between the angles in maximal supination and maximal pronation was approximately 7° for both readers. ICC was very good for intraobserver agreement (Reader1: r ≥ 0.92, p < 0.001; Reader 2: r ≥ 0.93, p < 0.001), as well as for interobserver agreement (phase 1: r ≥ 0.87, p < 0.001; phase 2: r ≥ 0.90, p < 0.001). CONCLUSION: The extremes of the rotational movement of the forearm affect the longitudinal morphology and anatomic relationships of the DBRN, primarily demonstrating the convergence of the nerve towards the SASM in maximal pronation and divergence in maximal supination.

Radiographic and computed tomographic evaluation of supinator sesamoid bones in dogs.

BACKGROUND: The present study evaluated the frequency of supinator sesamoid bones (SSB) on radiography and computed tomography (CT). Interobserver agreement was evaluated in the detection of the SSBs in both methods. A correlation between the existence of SSBs and elbow diseases (ED) was assessed. For these purposes, radiographs, and CT scans of 100 dogs were scored by 3 observers. RESULTS: The SSB was identified as a round to oval-shaped opacity and measured 0.5-6.56 mm × 0.5-6.2 mm. SSBs were reported in an average of 8,33% of dogs on radiographs and 26% of dogs on CT; a bilateral sesamoid bone was present in 43,52% and 76,92% of these dogs, respectively. Seventy-two percent of the SSBs was identified on CT were not detected on radiographs. The Kappa test showed a substantial agreement (κ = 0.691) and a perfect agreement (κ = 1) between the observers in the detection of SSBs on radiography and on CT scans respectively. Additionally, a weak positive correlation was detected between ED and the existence of SSBs. CONCLUSION: A supinator sesamoid bone can be detected occasionally in the evaluation of the canine elbow joints by routine radiography. CT is superior to radiography for assessing SSBs with a higher interobserver agreement. The correlation of the existence of the SSBs and ED, needs further evaluations to prove a probable pathophysiological connection.

Role of the supinator muscle in the pathophysiological mechanism of a pulled elbow.

A pulled elbow is a common childhood orthopaedic injury that is usually caused by longitudinal traction on the hand. The pathophysiological mechanism of a pulled elbow involves interposition of the annular ligament into the radiohumeral joint. Recent ultrasonographic studies have shown that both the supinator muscle and annular ligament were trapped into the radiohumeral joint. This paper discusses why pulled elbows can occur during pronation and how a pulled elbow can be reduced either by hyperpronation or supination followed by elbow flexion based on the function of the supinator muscle.

The arcade of Frohse: a systematic review and meta-analysis.

PURPOSE: The structure of the proximal margin of the superficial layer of the supinator muscle is of high interest to many researches. Its tendinous appearance, called the arcade of Frohse, may be clinically important because of its close relationship to the deep branch of the radial nerve passing beneath it and is considered to be the cause of several syndromes. Given the importance of this structure, we aimed to provide a comprehensive and evidence-based review with meta-analytic techniques. MATERIALS AND METHODS: The meta-analysis was performed in adherence to the PRISMA guidelines. Three medical databases were searched in order to identify all potentially eligible articles. Included studies were assessed for quality and the extracted morphological and morphometric data from the relevant articles was analyzed with the use of random effects meta-analysis. RESULTS: A total of 20 studies were included into this meta-analysis. The pooled prevalence of the arcade of Frohse was calculated to be 66% within the adult population and 0% in the fetuses. Other variations regarding the arcade of Frohse were identified as very rare. Analysis of the morphometric parameters revealed the average proportions to be 23.22 mm for the length, 11.05 mm for the width and the mean thickness is 0.67 mm. CONCLUSIONS: The arcade of Frohse is a commonly found structure in adults and thoughtful knowledge of its texture and morphology is especially useful in neurology, neurosurgery, orthopedics, trauma surgery and hand surgery, because it is considered to be the most common source of compression for the deep branch of the radial nerve.

Comparison of maximal isometric forearm supination torque in two elbow positions between subjects with and without limited forearm supination range of motion.

Study Design: Cross-sectional comparison. Introduction: Forearm supination range of motion is often limited by short or stiff pronators. Many studies have examined maximal isometric forearm supination torque (MIFST). However, there is little research comparing MIFST in two elbow positions between subjects with and without limited forearm supination range of motion (LSR). Purpose of the Study: The purpose of this study was to compare MIFST in two elbow positions (90º flexed elbow, extended elbow) between subjects with and without LSR. Methods: Thirteen right-handed subjects (seven men, six women) with LSR and 13 age- and gender-matched healthy controls participated in this study. The forearm supination range of motion and MIFST were measured using a Smart KEMA system. Two-way repeated-measures analysis of variance was used to compare MIFST in two elbow positions between subjects with and without LSR. Results: No significant difference between groups (p > .05) was found. However, there was an interaction effect between elbow position and group on MIFST (p < .05). Independent t-tests were used to confirm the simple effects. In the LSR group, the value of MIFST was significantly lower in the elbow-extended position than in the group without LSR (p < .05). Conclusions: These findings indicate that elbow position should be considered when assessing the strength or increasing the strength of the supinator muscle, especially in patients with LSR.

Evaluation of the supinator muscle and deep branch of the radial nerve: impact on nerve compression.

PURPOSE: The aim of this study was to investigate the superficial head of supinator muscle (SM) and deep branch of the radial nerve (DBRN) course in SM to see whether the texture characteristics of the superficial head of SM might have a potential compressive effect on the nerve. MATERIALS AND METHODS: Elbow and proximal forearm region of 20 preserved cadavers (n 40, 12 M, 8 F) were dissected in order to measure total and part of DBRN lengths between some reference points. The texture characteristics of both the proximal (where DBRN enters SM) and distal arcade (where DBRN exits SM) of the superficial head of SM were evaluated based on its structure's being muscular, musculotendinous, tendinous, or membranous. RESULTS: The total length of DBRN between sexes without taking side (L/R) into consideration (P = 0.030) and left radiocapitellar joint (RCJ)-arcade of Frohse (AF) length between sexes (P = 0.050) were statistically significant. There was a gradual increase in caliber getting more flattened in every consecutive level which was statistically significant when every two consecutive levels were compared. When compared according to the texture type, there were also significant differences. CONCLUSIONS: Flattening of DBRN in the supinator canal suggests a chronic compression on the nerve. Differences in the texture of the superficial head of the supinator might facilitate this compression. An understanding of the anatomy and nerve topography is of utmost importance in the accurate diagnosis and effective management of peripheral nerve compression.

Posterior interosseous nerve of the elbow at the arcade of Frohse: Ultrasound appearance in asymptomatic subjects.

PURPOSE: To assess the normal values of the antero-posterior (AP) diameter of the posterior interosseous nerve (PIN) of the elbow as it passes beneath the arcade of Frohse and to search for PIN-diameter differences between the upstream, entry point and downstream of the arcade. MATERIAL AND METHODS: Thirty asymptomatic patients prospectively underwent bilateral B-mode ultrasound of the PIN of the elbow. There were 15 men and 15 women with a mean age of 30.2±5.31 (SD) years (range: 26-43 years). Of these, 23 patients were right-handers (23/30; 77%) and 7 were left handers (7/30; 23%). AP diameter of the PIN was measured in long axis at three different locations including the entry point of the arcade, 5-mm upstream and 5-mm downstream the arcade. A comparison between the three measurements was performed using paired t-test. RESULTS: The mean AP diameters of the PIN were 0.83±0.21 (SD) mm (range: 0.43-1.31mm), 0.6±0.17 (SD) mm (range: 0.29-1.16mm) and 0.49±0.13 (SD) mm (range: 0.26-0.86mm) at 5-mm upstream, entry point of the arcade and 5-mm downstream the arcade of Frohse, respectively. Significant drops in PIN diameter were found between upstream and the arcade (-0.23mm; 27%; P<0.001), between the arcade and downstream (-0.11mm; 17%; P<0.001), and between upstream and downstream the arcade (-0.34mm; 40%; P<0.001). CONCLUSION: Disparity in AP diameter of the PIN of the elbow in the arcade of Frohse is a normal finding and should not be erroneously interpreted as entrapment when present alone.

Intramuscular Myxoma in the Supinator Muscle with Transient Postoperative Posterior Interosseous Nerve Palsy: A Case Report.

BACKGROUND: Intramuscular myxomas are rare, benign mesenchymal tumors in the musculoskeletal system, and usually, the tumors arise in the large muscles of the thigh, buttocks, shoulder, and upper arm. However, a tumor of the forearm is very rare. Herein, we describe the case of an intramuscular myxoma in the supinator muscle of a 56-year-old female patient. CASE PRESENTATION: Magnetic resonance imaging showed a well-defined mass that was hypointense with the peritumoral fat ring sign. The differential diagnoses might have been myxoma, schwannoma, or intramuscular hemangioma. The histopathological image showed abundant myxoid tissue, hypocellularity, and poor vascularization. The cells of the tumor were spindle and stellate-shaped with normochromic nuclei. Based on these findings, the pathological diagnosis was an intramuscular myxoma. After excising the tumor, the patient had transient posterior interosseous nerve palsy. CONCLUSION: This tumor is curative by resection in toto; however, when the tumor exists in the forearm, surgeons should be careful to avoid damaging surrounding tissues because the tumor is very hard and relatively large compared to the forearm.

The relationship of the posterior interosseous nerve to the supinator muscle in the dorsal approach to the proximal radius: A descriptive and quantitative anatomic study of Filipino cadavers

BACKGROUND AND OBJECTIVE:The posterior interosseous nerve (PIN) is vulnerable to injury in the dorsal approach to the proximal radius. The goal of this study is to describe the quantitative relationship of the PIN to the supinator muscle in the context of anatomic landmarks. Knowledge of superficial landmarks related to the PIN would hopefully minimize iatrogenic injury to the posterior interosseous nerve.METHODS: 12 cadavers (22 forearms) were dissected and analyzed. The length of the supinator muscle was determined. The oblique distances of the PIN entry and exit points to the proximal and distal borders of the supinator muscle as well as their perpendicular distances to the lateral epicondyle-Lister's tubercle (LE-LT) reference line were measured and recorded. The number of PIN branches inside the supinator substance was recorded. Mean and median values were determined and subjected to statistical analysis.RESULTS: Mean supinator length was 5 centimeters. Ninety-one percent of the cadaveric forearms had PIN branches inside the supinator muscle substance. Twelve of the 22 forearms (55%) had 2 branches. The mean oblique distances of the PIN from the lateral epicondyle to the entry and exit points in the proximal and distal borders of the supinator muscle was 3.52 and 7.31 centimeters, respectively. The mean perpendicular distances of the PIN from LE-LT reference line to the entry and exit points in the proximal and distal borders of the supinator muscle was 1.13 and 1.26 centimeters, respectively. An imaginary danger-zone 4 centimeters wide overlying the LE-LT reference line depicts the possible area where the PIN and its branches may most likely be located.CONCLUSION: The dorsal approach to the proximal radius may allow a safe exposure without causing iatrogenic injury to the posterior interosseous nerve through the use of superficial anatomic landmarks and reference lines in combination with mean measurements from our study.

The relationship of the posterior interosseous nerve to the supinator muscle in the dorsal approach to the proximal radius: A descriptive and quantitative anatomic study of Filipino cadavers

@#<p style="text-align: justify;"><strong>BACKGROUND AND OBJECTIVE:</strong>The posterior interosseous nerve (PIN) is vulnerable to injury in the dorsal approach to the proximal radius. The goal of this study is to describe the quantitative relationship of the PIN to the supinator muscle in the context of anatomic landmarks. Knowledge of superficial landmarks related to the PIN would hopefully minimize iatrogenic injury to the posterior interosseous nerve.<br /><strong>METHODS:</strong> 12 cadavers (22 forearms) were dissected and analyzed. The length of the supinator muscle was determined. The oblique distances of the PIN entry and exit points to the proximal and distal borders of the supinator muscle as well as their perpendicular distances to the lateral epicondyle-Lister's tubercle (LE-LT) reference line were measured and recorded. The number of PIN branches inside the supinator substance was recorded. Mean and median values were determined and subjected to statistical analysis.<br /><strong>RESULTS:</strong> Mean supinator length was 5 centimeters. Ninety-one percent of the cadaveric forearms had PIN branches inside the supinator muscle substance. Twelve of the 22 forearms (55%) had 2 branches. The mean oblique distances of the PIN from the lateral epicondyle to the entry and exit points in the proximal and distal borders of the supinator muscle was 3.52 and 7.31 centimeters, respectively. The mean perpendicular distances of the PIN from LE-LT reference line to the entry and exit points in the proximal and distal borders of the supinator muscle was 1.13 and 1.26 centimeters, respectively. An imaginary danger-zone 4 centimeters wide overlying the LE-LT reference line depicts the possible area where the PIN and its branches may most likely be located.<br /><strong>CONCLUSION:</strong> The dorsal approach to the proximal radius may allow a safe exposure without causing iatrogenic injury to the posterior interosseous nerve through the use of superficial anatomic landmarks and reference lines in combination with mean measurements from our study.</p>

High resolution ultrasound in posterior interosseous nerve syndrome.

INTRODUCTION: Posterior interosseous nerve (PIN) syndrome is a rare compression neuropathy of the PIN in the region of the supinator muscle, most common by the arcade of Frohse. We aimed to specify ultrasonographic findings in patients with PIN syndrome in comparison to healthy volunteers. METHODS: Ultrasound images and clinical data of 13 patients with PIN syndrome confirmed by neurological examination and electrophysiological testing were evaluated retrospectively. Anteroposterior nerve diameters measured at the arcade of Frohse were compared with those of 20 healthy volunteers. The echotexture and the presence of a caliber change of the PIN were additionally assessed. RESULTS: Enlargement of the PIN was seen in all patients with PIN syndrome, but not in volunteers (statistically significant difference in mean diameter P < 0.05). Furthermore, edema and caliber change of the PIN were present in all patients. CONCLUSIONS: High-resolution ultrasound allows for differentiation between patients with PIN syndrome and healthy volunteers.

Influence of developing ligaments on the muscles in contact with them: a study of the annular ligament of the radius and the sacrospinous ligament in mid-term human fetuses.

The supinator muscle originates from the annular ligament of the radius, and the muscle fibers and ligament take a similar winding course. Likewise, the coccygeus muscle and the sacrospinous ligament are attached together, and show a similar fiber orientation. During dissection of adult cadavers for our educational curriculum, we had the impression that these ligaments grow in combination with degeneration of parts of the muscles. In histological sections of 25 human fetuses at 10-32 weeks of gestation, we found that the proximal parts of the supinator muscle were embedded in collagenous tissue when the developing annular ligament of the radius joined the thick intermuscular connecting band extending between the extensor carpi radialis and anconeus muscles at 18-22 weeks of gestation, and the anterior parts of the coccygeus muscle were surrounded by collagenous tissue when the intramuscular tendon became the sacrospinous ligament at 28-32 weeks. Parts of these two muscles each seemed to provide a mold for the ligament, and finally became involved with it. This may be the first report to indicate that a growing ligament has potential to injure parts of the "mother muscle," and that this process may be involved in the initial development of the ligament.

Influence of developing ligaments on the muscles in contact with them: a study of the annular ligament of the radius and the sacrospinous ligament in mid-term human fetuses / 대한해부학회지

The supinator muscle originates from the annular ligament of the radius, and the muscle fibers and ligament take a similar winding course. Likewise, the coccygeus muscle and the sacrospinous ligament are attached together, and show a similar fiber orientation. During dissection of adult cadavers for our educational curriculum, we had the impression that these ligaments grow in combination with degeneration of parts of the muscles. In histological sections of 25 human fetuses at 10-32 weeks of gestation, we found that the proximal parts of the supinator muscle were embedded in collagenous tissue when the developing annular ligament of the radius joined the thick intermuscular connecting band extending between the extensor carpi radialis and anconeus muscles at 18-22 weeks of gestation, and the anterior parts of the coccygeus muscle were surrounded by collagenous tissue when the intramuscular tendon became the sacrospinous ligament at 28-32 weeks. Parts of these two muscles each seemed to provide a mold for the ligament, and finally became involved with it. This may be the first report to indicate that a growing ligament has potential to injure parts of the "mother muscle," and that this process may be involved in the initial development of the ligament.

Ultrasound assessment on selected peripheral nerve pathologies. Part I: Entrapment neuropathies of the upper limb - excluding carpal tunnel syndrome.

Ultrasound (US) is one of the methods for imaging entrapment neuropathies, post-traumatic changes to nerves, nerve tumors and postoperative complications to nerves. This type of examination is becoming more and more popular, not only for economic reasons, but also due to its value in making accurate diagnosis. It provides a very precise assessment of peripheral nerve trunk pathology - both in terms of morphology and localization. During examination there are several options available to the specialist: the making of a dynamic assessment, observation of pain radiation through the application of precise palpation and the comparison of resultant images with the contra lateral limb. Entrapment neuropathies of the upper limb are discussed in this study, with the omission of median nerve neuropathy at the level of the carpal canal, as extensive literature on this subject exists. The following pathologies are presented: pronator teres muscle syndrome, anterior interosseus nerve neuropathy, ulnar nerve groove syndrome and cubital tunnel syndrome, Guyon's canal syndrome, radial nerve neuropathy, posterior interosseous nerve neuropathy, Wartenberg's disease, suprascapular nerve neuropathy and thoracic outlet syndrome. Peripheral nerve examination technique has been presented in previous articles presenting information about peripheral nerve anatomy [Journal of Ultrasonography 2012; 12 (49): 120-163 - Normal and sonographic anatomy of selected peripheral nerves. Part I: Sonohistology and general principles of examination, following the example of the median nerve; Part II: Peripheral nerves of the upper limb; Part III: Peripheral nerves of the lower limb]. In this article potential compression sites of particular nerves are discussed, taking into account pathomechanisms of damage, including predisposing anatomical variants (accessory muscles). The parameters of ultrasound assessment have been established - echogenicity and echostructure, thickness (edema and related increase in the cross sectional area of the nerve trunk), vascularization and the reciprocal relationship with adjacent tissue.

Topographic Anatomy on the Supinator Muscle and the Deep Radial Nerve in Relation with its Entrapment Syndrome / 대한해부학회지

The deep radial nerve could be compressed by the medial border of the extensor carpi radialis brevis muscle, superior or inferior border of the superficial layer of the supinator muscle and pathologic structures between two layers of the supinator muscle. The aim of this study was to clarify the topographic relationships between the deep radial nerve and the supinator muscle in the place where the entrapment syndrome of the nerve could be occurred. Sixty-six Korean adult cadavers (124 arms) were used. The angles of the deep radial nerve with the radius were measured on the anteroposterior and lateral radiographs. The average distance between a line through the tips of both epicondyles of the humerus, and the division sites of the radial nerve into superficial and deep branches, was 16.8+/-12.8 mm in the cases where the division sites were proximal to the line, and 7.8+/-5.0 mm in the cases where the division sites were distal to the line. The arcade of Frohse was 32.2+/-6.6 mm apart from the line connecting both tips of humeral epicondyles. The average length of the deep radial nerve covered by the superficial layer of the supinator muscle was 35.1+/-8.0 mm. The arcade of Frohse was classified into two types; semi-circular type in 68.6% and dull curved line type in 31.4%. The lateral border of the arcade of Frohse was composed of muscle, tendon, and both muscle and tendon in 12.1%, 26.6%, and 61.3%, respectively. The muscle fibers of two layers of the supinator muscle were fused with each other, at the area where the deep radial nerve came out between two layers of the muscle. The average angles of the deep radial nerve with the radius, were 23.4+/-4.6 degrees and 13.7+/-5.3 degrees, on the anteroposterior and lateral radiographs, respectively. The inferior border of the superficial layer of the supinator muscle was composed of tendon, muscle, and both muscle and tendon in 61.5%, 12.5%, and 17.3%, respectively. We discussed about the morphologic variations which could cause the entrapment syndrome of the deep radial nerve in the proximal and distal portions of the supinator muscle, and between the superficial and deep layers of the muscle.