Upper extremity peripheral nerve anatomy: current concepts and applications

Multimodality imaging review of ulnar nerve pathologies

The ulnar nerve is the second most commonly entrapped nerve after the median nerve. Although clinical evaluation and electrodiagnostic studies remain widely used for the evaluation of ulnar neuropathy, advancements in imaging have led to increased utilization of these newer / better imaging techniques in the overall management of ulnar neuropathy. Specifically, high-resolution ultrasonography of peripheral nerves as well as MRI has become quite useful in evaluating the ulnar nerve in order to better guide treatment. The caliber and fascicular pattern identified in the normal ulnar nerves are important distinguishing features from ulnar nerve pathology. The cubital tunnel within the elbow and Guyon's canal within the wrist are important sites to evaluate with respect to ulnar nerve compression. Both acute and chronic conditions resulting in deformity, trauma as well as inflammatory conditions may predispose certain patients to ulnar neuropathy. Granulomatous diseases as well as both neurogenic and non-neurogenic tumors can also potentially result in ulnar neuropathy. Tumors around the ulnar nerve can also lead to mass effect on the nerve, particularly in tight spaces like the aforementioned canals. Although high-resolution ultrasonography is a useful modality initially, particularly as it can be helpful for dynamic evaluation, MRI remains most reliable due to its higher resolution. Newer imaging techniques like sonoelastography and microneurography, as well as nerve-specific contrast agents, are currently being investigated for their usefulness and are not routinely being used currently.

CLINICAL AND FUNCTIONAL EVALUATION OF WRISTS AND HANDS OF SPINAL CORD INJURED PATIENTS

Introduction

The inability of the spinal cord to propagate sensory and motor stimuli as a result of the disruption of the nerve tracts is called spinal cord injury.

Objective

This study analyzes clinically and radiologically the hands and wrists of spinal cord injured patients, evaluating their motor and sensitive functionality, in order to determine if these patients are more likely to develop degenerative alterations.

Methods

14 patients (8 paraplegics and 6 tetraplegics) were evaluated, undergoing anamnesis and clinical examination - a scale of muscular strength (MRC - Medical Research Council) and the amplitude measurement of the movement with a manual goniometer (ROM), were used for objective evaluation - and x-ray exams. The results were compared with pre-existing data from other studies.

Results

When asked, only one of the 14 observed patients complained about constant wrist pain, described as level 3 (weak to moderate), based on the visual analog scale (VAS). The motor evaluation, MRC and ROM divided the group of patients into two subgroups: paraplegic and tetraplegic patients. The x-ray analysis showed, based on Kellgren and Lawrence classification, that all exam images fit grades 1 or 2 of osteoarthritis and osteoarthrosis.

Conclusion

In conclusion, spinal cord injured patients showed none or minimal clinical and radiological signs of osteoarthritis on hands or wrists. Overall, the hands and wrists of spinal cord-injured patients behave similarly to noninjured patients. Level of Evidence III; Retrospective Comparative Study.

Radial neuropathy

Radial neuropathy is the third most common upper limb mononeuropathy after median and ulnar neuropathies. Muscle weakness, particularly wrist drop, is the main clinical feature of most cases of radial neuropathy, and an understanding of the radial nerve's anatomy generally makes localizing the lesion straightforward. Electrodiagnosis can help confirm a diagnosis of radial neuropathy and may help with more precise localization of the lesion. Nerve imaging with ultrasound or magnetic resonance neurography is increasingly used in diagnosis and is important in patients lacking a history of major arm or shoulder trauma. Radial neuropathy most often occurs in the setting of trauma, although many other uncommon causes have been described. With traumatic lesions, the prognosis for recovery is generally good, and for patients with persistent deficits, rehabilitation and surgical techniques may allow substantial functional improvement.

Radial Tunnel Syndrome: Review and Best Evidence

Radial tunnel syndrome (RTS) is caused by compression of the posterior interosseous nerve and consists of a constellation of symptoms that have previously been characterized as aspects of other disease processes, as opposed to a distinct diagnosis. First described in the mid-20th century as "radial pronator syndrome," knowledge regarding the anatomy and presentation of RTS has advanced markedly over the past several decades. However, there remains notable controversy and ongoing research regarding diagnostic imaging, nonsurgical treatment options, and indications for surgical intervention. In this review, we will discuss the anatomic considerations of RTS, relevant physical examination findings, potential diagnostic modalities, and outcomes of several treatment options.

Role of dynamic ultrasound in assessment of the snapping elbow and distal biceps tendon injury

Introduction

Ultrasound is useful in assessing patients with snapping syndromes around the elbow joint. The dynamic nature of the examination allows for direct visualisation of the underlying causative factor.Topic description: We discuss the role of dynamic ultrasound in assessing various snapping syndromes around the elbow, such as ulnar nerve instability, snapping triceps and less commonly, snapping brachialis. Ultrasound is also useful in evaluating the distal biceps tendon, particularly in differentiating partial from complete tendon injury.

Discussion

Ulnar nerve instability and snapping triceps can be assessed via a medial approach with the transducer placed transversely between the medial epicondyle and the olecranon. In ulnar nerve instability, the nerve can be seen crossing over the medial epicondyle on elbow flexion. In snapping triceps syndrome, both the ulnar nerve and the distal triceps can be seen dislocating over the medial epicondyle. Dynamic assessment of the distal biceps tendon using a lateral approach minimises anisotropy artefact often seen on the anterior approach. Passive pronation and supination of the forearm will reveal little or no movement in a completely torn tendon whereas moving tendon fibres will be appreciated in partial tears. In a snapping brachialis, the medial portion of brachialis will be seen abnormally translocating anterolateral to the medial border of the trochlea during elbow flexion and snapping back into its normal position on elbow extension.

Conclusion

Dynamic ultrasound of the elbow is valuable in diagnosing patients with snapping sensations around the joint and in evaluating the integrity of the distal biceps tendon.

Radial Tunnel Syndrome

PURPOSE

Radial tunnel syndrome is defined as a compressive neuropathy of the posterior interosseus nerve. It is differentiated from posterior interosseus nerve compression by symptom profile. The purpose of this article is to review past and current literature on the topic and determine if there are any emerging treatment options for this condition.

RECENT FINDINGS

Traditionally, conservative management of Radial Tunnel syndrome has been relatively unsuccessful. As a result, patients afflicted by this neuropathy require operative intervention. Effectiveness of surgical decompression is variable and can range from 67 to 92% but currently remains the standard treatment. However, there are some conservative treatment options that have been recently reported that show promising results. Such treatments include dry needling of the affected area and ultrasound guided corticosteroid injections to hydro dissect around the posterior interosseus nerve at sites of compression. Radial tunnel syndrome is an uncommon and unique peripheral neuropathy. It involves the posterior interosseus nerve however it can be differentiated from PIN syndrome based on the symptom profile. There are various compressive etiologies that can cause a patient to become symptomatic; therefore it is important to critically assess the patient and their symptoms and use appropriate imaging to determine the cause and appropriate treatment. Typically, conservative treatments are attempted first. Traditionally, conservative therapy is unsuccessful and operative decompression is necessary. However, current literature highlights various new nonsurgical options that suggest some promise and could be alternatives to surgical decompression.

The Branching and Innervation Pattern of the Radial Nerve in the Forearm: Clarifying the Literature and Understanding Variations and Their Clinical Implications

BACKGROUND

This study attempted to clarify the innervation pattern of the muscles of the distal arm and posterior forearm through cadaveric dissection.

METHODS

Thirty-five cadavers were dissected to expose the radial nerve in the forearm. Each muscular branch of the nerve was identified and their length and distance along the nerve were recorded. These values were used to determine the typical branching and motor entry orders.

RESULTS

The typical branching order was brachialis, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, supinator, extensor digitorum, extensor carpi ulnaris, abductor pollicis longus, extensor digiti minimi, extensor pollicis brevis, extensor pollicis longus and extensor indicis. Notably, the radial nerve often innervated brachialis (60%), and its superficial branch often innervated extensor carpi radialis brevis (25.7%).

CONCLUSIONS

The radial nerve exhibits significant variability in the posterior forearm. However, there is enough consistency to identify an archetypal pattern and order of innervation. These findings may also need to be considered when planning surgical approaches to the distal arm, elbow and proximal forearm to prevent an undue loss of motor function. The review of the literature yielded multiple studies employing inconsistent metrics and terminology to define order or innervation.

Contraceptive subcutaneous device migration: what does an orthopaedic surgeon need to know? A case report and literature review

Subdermal contraceptive implant is approved in more than 60 countries and used by millions of women around the world. Although relatively safe in nature, their implantation and removal may be associated with potential complications, some of which may require surgical intervention. Two types of peripheral neurological complications are reported: complications related to compressive neuropathy caused by device decubitus and complications related to device improper removal. An healthy 35-year-old woman come to our attention for paresthesia from medial side of right elbow to fourth and fifth fingers. Tinel sign was positive on medial side of distal third of right arm, above the elbow, as well. Clinical history of patients revealed a subcutaneous placement of a etonogestrel implant 3 years before. Patients reported disappearing of tactile feeling of subcutaneous contraceptive implant since two months. At clinical examination, implant was not felt in its original subcutaneous place. X-rays control revealed its proximal and deep migration. Surgical exploration for subcutaneous contraceptive implant removal revealed it lying on the ulnar nerve. Patient referred immediate paresthesia disappearing after surgery. At 1 month follow up no motor or sensory alteration were evident. Removal of implants inserted too deeply must be carefully performed to prevent damages to nervous and vascular structures and it should be performed by operators who are very familiar with the anatomy of the arm. In case of chronic neuropathy caused by implant nerve compression only an appropriate patients information about rare but possible neuropathic symptoms related to device migration and a careful medical history collecting can avoid a mistaken diagnosis of canalicular syndrome.

Establishing Safe Zones to Avoid Nerve Injury in the Approach to the Humerus in Pediatric Patients: A Magnetic Resonance Imaging Study

BACKGROUND

The surgical anatomy of upper-extremity peripheral nerves in adults has been well described as "safe zones" or specific distances from osseous landmarks. In pediatrics, relationships between nerves and osseous landmarks remain ambiguous. The goal of our study was to develop a model to accurately predict the location of the radial and axillary nerves in children to avoid iatrogenic injury when approaching the humerus in this population.

METHODS

We conducted a retrospective review of 116 magnetic resonance imaging (MRI) scans of entire humeri of skeletally immature patients; 53 of these studies met our inclusion criteria. Two independent observers reviewed all scans. Arm length was measured as the distance between the lateral aspect of the acromion and the lateral epicondyle. We then calculated the distances (defined as the percentage of arm length) between the radial nerve and distal osseous landmarks (the medial epicondyle, transepicondylar line, and lateral epicondyle) as well between the axillary nerve and the most lateral aspect of the acromion.

RESULTS

The axillary nerve was identified at a distance equaling 18.6% (95% confidence interval [CI], ±0.62%) of arm length inferior to the lateral edge of the acromion. The radial nerve crossed (1) the medial cortex of the posterior part of the humerus at a distance equaling 63.19% (95% CI: ±0.942%) of arm length proximal to the medial epicondyle, (2) the middle of the posterior part of the humerus at a distance equaling 53.9% (95% CI: ±1.08%) of arm length proximal to the transepicondylar line, (3) the lateral cortex of the posterior part of the humerus at a distance equaling 45% (95% CI: ±0.99%) of arm length proximal to the lateral epicondyle, and (4) from the posterior to the anterior compartment at a distance equaling 35.3% (95% CI: ±0.92%) of arm length proximal to the lateral epicondyle. A strong linear relationship between these distances and arm length was observed, with an intraclass correlation coefficient of >0.9 across all measurements.

CONCLUSIONS

The positions of the radial and axillary nerves maintain linear relationships with arm lengths in growing children. The locations of these nerves in relation to palpable osseous landmarks are predictable.

CLINICAL RELEVANCE

Knowing the locations of upper-extremity peripheral nerves as a proportion of arm length in skeletally immature patients may help to avoid iatrogenic injuries during surgical approaches to the humerus.

Safe zone for lateral pin placement for external fixation of the distal humerus

External fixation is a common, efficient technique used for humeral shaft stabilization and elbow fractures. There are reports of radial nerve injuries associated with this procedure. In this study, we investigated the course and variability of the radial nerve along the lateral humerus in relation to the elbow joint to determine a relatively safe zone for lateral pin placement in external fixation. Twenty upper extremities from 10 cadavers were studied. The nerve branches and course of the radial nerve along the lateral humerus were carefully dissected. Straight lines (a, b, and c) were made connecting three landmarks (the acromion, coracoid process, and anterior wall of the axilla) in the proximal upper extremity to the lateral condyle (LC) of the humerus; their intersections with the radial nerve (A, B, and C) were marked. We analyzed whether the intersection positions were correlated with the connecting line lengths. The mean lengths of the connecting lines were (a) 27.24 ± 2.57, (b) 26.18 ± 2.79, and (c) 20.95 ± 1.44 cm; the distance between the intersection points and the LC of the humerus were (Aa) 7.56 ± 1.31, (Bb) 6.90 ± 2.27, and (Cc) 5.01 ± 0.83 cm; and the measured intersection points of the radial nerve in the lateral aspect of the humerus were (A) 18.48%-34.82%, (B) 13.48%-40.00%, and (C) 19.27%-28.05% of the lengths of lines a, b, and c, respectively. Our data provide a more reliable reference to predict the course of the radial nerve on the lateral humerus and define a safe zone for pin placement. Clin. Anat., 33:637-642, 2020. © 2019 Wiley Periodicals, Inc.

A Prospective Evaluation of the Anatomy of the First Dorsal Compartment in Patients Requiring Surgery for De Quervain's Tenosynovitis

Background  We prospectively evaluated the surgical anatomy during first dorsal compartment release for De Quervain's tenosynovitis, with special attention to the superficial branch of the radial nerve (SBRN). Additionally, the incidence of tendon instability during surgery was assessed. Methods  This prospective cohort study consisted of 130 De Quervain's patients undergoing first dorsal compartment release. The treating surgeons recorded the type of incision used, the number of abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendon slips, the number of SBRN branches encountered, additional subcompartments created by any septations, and active/passive tendon stability. Results  A singular first dorsal compartment was found in 37% of cases, whereas 55% of patients had two subcompartments and 8% had three. Multiple APL tendon slips (range: 1-4) were identified in 78% of patients. In contrast, a single EPB tendon was found in 92% of patients (range: 0-2). At least one SBRN was encountered in 61% of cases. Following surgery, instability was evident in 9% of patients, who had tendons perch with passive wrist flexion. In one of these patients (<1%), the tendons dislocated volarly out of the first dorsal compartment during active flexion. Conclusions  The anatomical findings in our relatively large, prospective study of De Quervain's patients undergoing first dorsal compartment release are consistent with previous smaller and/or retrospective studies. Overall, we expect to encounter the SBRN during first dorsal compartment release in more than 50% of patients but are unconcerned if it is not visualized during a careful approach. Tendon instability has an incidence of 9%; however, dislocation is rare (<1%).

Effects of the Elbow Flexion Angle on the Radial Nerve Location around the Humerus: A Cadaver Study for Safe Installation of a Hinged External Fixator

Background: This study aimed to investigate whether the distance between the radial nerve and rotational center of the elbow joint when observing from the lateral surface of the humerus changes according to passive elbow joint flexion for safe external fixation with a hinged fixator of the elbow joint.

Methods: Twenty fresh-frozen cadaveric arms were dissected. The points where the radial nerve crosses over the posterior aspect of the humerus, crosses through the lateral center, and crosses over the anterior aspect of the humerus were defined in the lateral view of the elbow joint, using fluoroscopy, as R1, R2, and R3, respectively. The distances between the rotational center and each point on the radial nerve were measured when the flexion angle of the elbow joint was 10°, 50°, 90°, and 130°.

Results: The distances between the rotational center and R1, R2, and R3 were 118 mm, 94 mm, and 65 mm, respectively, when the flexion angle was 10°; 112 mm, 93 mm, and 74 mm, respectively, for 50°; 108 mm, 93 mm, and 77 mm, respectively, for 90°; and 103 mm, 94 mm, and 83 mm, respectively, for 130°. The distance between the rotational center and R2 was constant regardless of the flexion angle. With elbow joint extension, the distances between R1 and R3 increased; the safe zone, a region where the radial nerve would not be located on the humerus, was the smallest in extension. When the elbow joint was flexed, the distances between R1 and R3 decreased; the safe zone was the largest in flexion.

Conclusions: This study showed that the radial nerve location on the humerus varied based on the flexion angle of the elbow joint; the safe zone may change. A half-pin can be likely inserted safely, avoiding the elbow joint extension position.

Distance of the Posterior Interosseous Nerve from the Radial Head during Elbow Arthroscopy: An Anatomical Study

Purpose  The aims of this study were to measure the distance of the posterior interosseous nerve (PIN) from the radial head (RH) and its variations with forearm movements.

Methods  Five fresh frozen cadaver specimens were dissected under arthroscopy. An anterior capsulectomy extended to the entire lateral compartment was performed. The need of soft tissue dissection to isolate the nerve in the extracapsular space was recorded. The distance between the nerve and the anterior part of the RH was then measured with a graduated caliper inserted via the midlateral portal with the forearm in neutral position, full pronation, and full supination.

Results  The PIN was identifiable in all the specimens. In four cases, it was surrounded by a thick layer of adipose tissue, and further dissection was necessary to isolate it. Damage of the PIN during dissection occurred in one case, in which the proximal part of the nerve was accidentally cut. In three of the remaining cases, an increased distance was measured with the forearm in supination, as compared with neutral and full pronation position.

Conclusion  This anatomical study suggests that in most of the cases, the PIN does not lay just extracapular at the level of the radiocapitellar joint, but is surrounded by a thick layer of adipose tissue. Furthermore, its distance from the RH appears to increase with forearm supination. This position could increase the safe working space between RH and PIN.

Clinical Relevance  Knowledge of PIN position in relation to the anterior elbow capsule and its changes with forearm movements can help reduce the iatrogenic injuries during elbow arthroscopy.

Clarification of Eponymous Anatomical Terminology: Structures Named After Dr Geoffrey V. Osborne That Compress the Ulnar Nerve at the Elbow

BACKGROUND

In 1957, Dr Geoffrey Osborne described a structure between the medial epicondyle and the olecranon that placed excessive pressure on the ulnar nerve. Three terms associated with such structures have emerged: Osborne's band, Osborne's ligament, and Osborne's fascia. As anatomical language moves away from eponymous terminology for descriptive, consistent nomenclature, we find discrepancies in the use of anatomic terms. This review clarifies the definitions of the above 3 terms.

METHODS

We conducted an extensive electronic search via PubMed and Google Scholar to identify key anatomical and surgical texts that describe ulnar nerve compression at the elbow. We searched the following terms separately and in combination: "Osborne's band," "Osborne's ligament," and "Osborne's fascia." A total of 36 papers were included from 1957 to 2016.

RESULTS

Osborne's band, Osborne's ligament, and Osborne's fascia were found to inconsistently describe the etiology of ulnar neuritis, referring either to the connective tissue between the 2 heads of the flexor carpi ulnaris muscle as described by Dr Osborne or to the anatomically distinct fibrous tissue between the olecranon process of the ulna and the medial epicondyle of the humerus.

CONCLUSIONS

The use of eponymous terms to describe ulnar pathology of the elbow remains common, and although these terms allude to the rich history of surgical anatomy, these nonspecific descriptions lead to inconsistencies. As Osborne's band, Osborne's ligament, and Osborne's fascia are not used consistently across the literature, this research demonstrates the need for improved terminology to provide reliable interpretation of these terms among surgeons.

High-resolution ultrasound visualization of the recurrent motor branch of the median nerve: normal and first pathological findings

Purpose

To evaluate in a prospective study the possibility of visualization and diagnostic assessment of the recurrent motor branch (RMB) of the median nerve with high-resolution ultrasound (HRUS).

Materials and methods

HRUS with high-frequency probes (18–22 MhZ) was used to locate the RMB in eight fresh cadaveric hands. To verify correct identification, ink-marking and consecutive dissection were performed. Measurement of the RMB maximum transverse-diameter, an evaluation of the origin from the median nerve and its course in relation to the transverse carpal ligament, was performed in both hands of ten healthy volunteers (n = 20). Cases referred for HRUS examinations for suspected RMB lesions were also assessed.

Results

The RMB was clearly visible in all anatomical specimens and all volunteers. Dissection confirmed HRUS findings in all anatomical specimens. Mean RMB diameter in volunteers was 0.7 mm ± 0.1 (range, 0.6–1). The RMB originated from the radial aspect in 11 (55%), central aspect in eight (40%) and ulnar aspect in one (5%) hand. Nineteen (95%) extraligamentous courses and one (5%) subligamentous course were detected. Three patients with visible RMB abnormalities on HRUS were identified.

Conclusion

HRUS is able to reliably visualize the RMB, its variations and pathologies.

Key Points

• Ultrasound allows visualization of the recurrent motor branch of the median nerve.

• Ultrasound may help clinicians to assess patients with recurrent motor branch pathologies.

• Patient management may become more appropriate and targeted therapy could be improved.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-016-4671-1) contains supplementary material, which is available to authorized users.

High Median Nerve Injury: Motor and Sensory Nerve Transfers to Restore Function

This article describes the clinically significant motor and sensory deficits that follow high median nerve injuries and addresses the indications, limitations, and outcomes of nerve transfers, when striving to overcome the deficits these patients' experiences. Preferred surgical reconstructive strategy using motor and sensory nerve transfers, and surgical techniques used to perform these transfers, are described.

Complications of Carpal Tunnel Release

Carpal tunnel release for compression of the median nerve at the wrist is one of the most common and successful procedures in hand surgery. Complications, though rare, are potentially devastating and may include intraoperative technical errors, postoperative infection and pain, and persistent or recurrent symptoms. Patients with continued complaints after carpal tunnel release should be carefully evaluated with detailed history and physical examination in addition to electrodiagnostic testing. For those with persistent or recurrent symptoms, a course of nonoperative management including splinting, injections, occupational therapy, and desensitization should be considered prior to revision surgery.

Reappraisal of Clinical Deficits Following High Median Nerve Injuries

PURPOSE

To describe clinically apparent motor and sensory deficits in a cohort of 11 patients with isolated injury of the median nerve above the elbow and compare them against similar cases reported in the literature.

METHOD

Eleven patients of mean age 30 years (SD ± 14 years; 6 males, 5 females) were examined a mean of 21 weeks (SD ± 16 weeks) after an isolated high median nerve injury. Pronation, wrist flexion, and finger flexion range of motion and strength (British Medical Research Council scale) were evaluated. Grasp and lateral pinch strength were assessed bilaterally using a dynamometer. Thumb opposition was evaluated using the Kapandji score. Sensory impairment was considered significant when there was no perception of a 2.0-g Semmes-Weinstein filament.

RESULTS

Pronation was largely preserved in all patients to a mean range of motion of 52° (SD ± 13°), and pronation strength was M4 in 10 of 11 patients. Wrist flexion scored M5 in all patients. Thumb and index distal interphalangeal joint flexion were absent in all patients. In all patients, middle, ring, and little finger flexion was complete and scored M5. Thumb function scored above 5 in all patients, averaging 7.5 (SD ± 1.2) on the Kapandji scale. Grasp and pinch strength were 43% (SD ± 12%) and 36% (SD ± 11%) of the contralateral (normal) limb, respectively. Impaired sensation of a 2.0-g monofilament was found only in the palmar region over the middle and distal phalanges of the index and middle fingers and the distal phalanx of the thumb.

CONCLUSIONS

Noteworthy discrepancies were identified between the clinical motor and sensory deficits described in the literature and those observed in our patients.

CLINICAL RELEVANCE

In most patients with a high median nerve injury, only thumb and index flexion and palmar sensation warrant surgical reconstruction. Decreased grasp and pinch strength was a major finding that should also be addressed by surgery.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

Complications of compressive neuropathy: prevention and management strategies

Compressive neuropathies of the upper extremity are common and can result in profound disability if left untreated. Nerve releases are frequently performed, but can be complicated by both iatrogenic events and progression of neuropathy. In this review, we examine the management of postoperative complications after 2 common nerve compression release procedures: carpal tunnel release and cubital tunnel release.

Radial nerve measurements in nonsymptomatic upper extremities of Filipinos: A cross-sectional study

INTRODUCTION

Despite reports on the association of radial nerve (RN) size and lateral epicondylalgia (LE), Filipino normative values on RN size in healthy elbows are not established. An association with upper extremity anthropometric measurements is likewise not reported.

METHODS

Musculoskeletal ultrasound measurements of the RN at the level of the lateral epicondyle (RN-LE), posterior interosseous nerve at the level of the radial head and supinator (PIN-RH and PIN-sup), and superficial RN (SRN) in the elbows of healthy Filipinos were made in Manila from January-September 2011.

RESULTS

A total of 198 elbows of 99 healthy participants aged 43 years (range, 33-48 years) [median(IQR)] were investigated. Men have larger PIN-RH, PIN-sup, and SRN compared with women. Arm length was associated with PIN-RH, PIN-sup, and SRN (P < 0.05). Activities and elbow circumference measurements (at 2 levels) were associated with PIN-RH.

CONCLUSIONS

RN reference values can now be used for comparison in elbows with LE.

Aberrant radial-ulnar nerve communication in the upper arm presenting as an unusual radial nerve palsy: a case report

An unusual communication between the radial and ulnar nerves was observed during repair of a fracture of the humerus in an adult patient who presented with unusual physical exam findings. The patient had loss of radial and ulnar nerve motor function, as well as decreased sensation in both nerve distributions. Radial nerve injury following fracture of the humerus is a common condition, and anatomic variations are therefore of importance to clinicians. Communications between branches of the brachial plexus are also not uncommon findings; however there is very little mention of communication between the radial and ulnar nerves in the literature. An appreciation of unusual nerve anatomy is important in explaining unusual finding in patients.

Safe zone for superolateral entry pin into the distal humerus in children: an MRI analysis

BACKGROUND

The radial nerve is at risk for iatrogenic injury during placement of pins, screws, or wires around the distal humerus. Unlike adults, detailed anatomic information about the relationship of the nerve to the distal humerus is lacking in children.

QUESTION/PURPOSES

This study evaluates the relationship of the radial nerve to the distal humerus in a pediatric population on conventional MRI and proposes an anatomic safe zone using easily identifiable bony landmarks on an AP elbow radiograph.

METHODS

To determine the course of the radial nerve at the lateral distal humerus, we reviewed 23 elbow radiographs and MRIs of 22 children (mean age, 9 ± 4 years; range, 3-12 years) obtained as part of their workup for various elbow conditions. We described a technique using distance ratios calculated as a percentage of the patient's own transepicondylar distance, defined as the distance measured between the apices of the medial and lateral epicondyles, on the AP elbow radiograph and the midcoronal MR image. The cross-reference tool on a Picture Archiving and Communication System was then used to identify axial MR image at the level where the transepicondylar distance was measured. On this axial image, a line was drawn connecting the medial and lateral epicondyles (the transepicondylar axis) and its midpoint was determined. The radial nerve angle was measured by a line from the radial nerve to the midpoint of the transepicondylar axis and a line along the lateral half of the transepicondylar axis. On this axial slice, the closest distance from the nerve to the underlying cortex of the distal humerus was measured. To further localize the nerve along the distal humerus, predetermined percentages of the transepicondylar distance were projected proximally from the level of the transepicondylar axis along the longitudinal axis of the humerus on the midcoronal MR image. At these designated heights, the corresponding axial MR image was identified using the cross-reference tool and the nerve was mapped in a similar fashion. We then proposed a simpler method using a best-fit line drawn along the lateral supracondylar ridge on the AP radiograph to define the safe zone for lateral pin entry.

RESULTS

On axial MR images, the radial nerve was located in the anterolateral quadrant with a mean radial nerve angle of 54° (range, 35°-87) at 0% transepicondylar distance (23 MRIs), 41° (range, 24°-63°) at 50% transepicondylar distance (23 MRIs), and ≥ 10° at 75% transepicondylar distance (on the 13 MRIs that extended this far cephalad). The mean closest distance between the radial nerve and the underlying humeral cortex was 10 mm (range, 3-26 mm) at 0% transepicondylar distance and 7 mm (3-16 mm) at 50% transepicondylar distance. On the AP elbow radiograph, the height of the lateral supracondylar ridge, determined by a best-fit line drawn along the lateral cortex of the ridge, diverged from the most proximal extent of the ridge at a point located at 60% transepicondylar distance (range, 51%-76%). At the corresponding location on the axial MR image, the nerve was located anterolaterally with a mean radial nerve angle of 39° (range, 15°-61°) and a mean distance of 6 mm (range, 2-10 mm) from the underlying humerus.

CONCLUSIONS

Our data suggest that percutaneous direct lateral entry Kirschner wires and half-pins can be safely inserted in the distal humerus in children along the transepicondylar axis, either at or slightly posterior to the lateral supracondylar ridge, when placed caudal to the point located where the lateral supracondylar ridge line diverges from the proximal extent of the supracondylar ridge on AP elbow radiograph.

Is there a safe zone to avoid superficial radial nerve injury with Kirschner wire fixation in the treatment of distal radius? A cadaveric study

AIM OF THE STUDY

To determine the relation of the superficial radial nerve to bony land-marks and to identify a safe zone for K-wire pinning in the distal radius.

METHOD

The superficial radial nerve was dissected in sixteen upper extremities of preserved cadavers.

RESULTS

We found that the superficial radial nerve emerged from under brachioradialis at a mean distance of 8.45 (±1.22) cm proximal to the radial styloid. The mean distance from the first major branching point of the superficial radial nerve to the radial styloid were 4.8 ± 0.4 cm. All branches of the superficial radial nerve were found to lie in the radial half of an isosceles triangle formed by the radial styloid, Lister's tubercle and the exit point of the superficial radial nerve. There is an elliptical area just proximal to the Lister's tubercle. This area is not crossed by any tendons or nerve. It is bounded by the extensor carpiradialis brevis, extensor pollicis longus.

CONCLUSION

Pinning through the radial styloid is unsafe as the branches of the superficial radial nerve passé close to it. The ulnar half of the isosceles triangle is safe regarding the nerve. The elliptical zone just proximal to the Lister's tubercle is safe regarding the tendons and nerve.

Exposures of the humerus for fracture fixation

The care of humeral shaft fractures is undergoing a transition to more aggressive treatment methods with more frequent operative fixation. The upper arm has an extensive network of nerves, arteries, and veins that must be protected during any operative exposure. The ultimate goal of fixation of a humerus fracture is rigid stabilization to allow early range of motion, protection of the neurovascular structures, and preservation of the triceps mechanism posteriorly and the anterior elbow flexor muscles.

Peripheral nerve injuries: advancing the field through research, collaboration, and education

The Andrew J. Weiland Medal is presented each year by the American Society for Surgery of the Hand and the American Foundation for Surgery of the Hand for a body of work related to hand surgery research. This essay, awarded the Weiland Medal in 2013, focuses on advancing the field of peripheral nerve injuries through research, collaboration, and education.

Invasive neural interfaces: the perspective of the surgeon

BACKGROUND

By implanting electrodes inside peripheral nerves, amputee's intentions are picked up and exploited to control novel dexterous sensorized hand prostheses. Under the pretext of presenting surgical technique and clinical outcomes of the implant of invasive peripheral neural interfaces in a human amputee, this article critically comments, from the point of view of the surgeon, strengths and weaknesses of the procedure.

MATERIALS AND METHODS

Four multielectrodes were implanted in the medial and ulnar nerves of a young volunteer, which, following a car-crash, had a left transradial amputation. Both nerves were approached with a single incision in the medial aspect of the upper arm. Four weeks later, the electrodes were removed.

RESULTS

Even if the trauma and the postamputation plastic processes altered the anatomy, electrodes were proficiently implanted with an overall success of 66%. Looking at the procedure from the surgeon's viewpoint unveils few still open issues. Electrodes weaknesses were related to the absence of stabilizing structures, the cable transit through the skin, the implant angle, and the unproven magnetic resonance imaging compatibility. Future investigations are needed to definitely address the better anesthesia, number and sites of incisions, the nerves to implant, and the convenience of performing epineural microdissection.

CONCLUSIONS

Invasive neural interfaces developmental process almost completely relies on the efforts of bioengineers and neurophysiologists; however, the surgeon is responsible for intra and perioperative factors. Therefore, he deserves to play a major role also at the stage of specifying the requirements, to satisfy the requisites of a safe, stable, and long-lasting implant.

Dorsal locked plate fixation of distal radius fractures

Distal radius fractures are common, and internal fixation for operative management of these injuries is widely accepted. Although use of the volar approach for plate fixation has become more popular, benefits of the dorsal surgical approach include the potential for direct reduction and assessment of articular alignment, evaluation and management of concomitant intrinsic intercarpal ligament injury, and initiation of early range of motion. For certain fracture patterns, dorsal plate fixation is the preferred surgical technique. Improvements in implant design, in particular the use of low-profile dorsal plates, has decreased the rate of complications seen previously with this technique. Here, we provide an overview of the evaluation of patients with distal radius fractures, as well as the surgical indications and contraindications, techniques, and complications after dorsal locked plate fixation of intra-articular distal radius fractures.

The double intramedullary cortical button fixation for distal biceps tendon repair

PURPOSE

This study was designed to present the novel technique of intramedullary cortical button fixation for distal biceps tendon repair via a single-limited anterior portal.

METHODS

To reattach the ruptured biceps tendon at the radial tuberosity, two Bicepsbutton(™) (Arthrex, Naples, FL, USA) were intramedullary positioned to the anterior cortex. The surgical procedure is described in detail. This technique has been performed in a first series of 3 patients with acute distal biceps tendon ruptures.

RESULTS

All patients were very satisfied after surgery and would undergo the same surgical procedure again. All patients regained full range of elbow motion with comparable strength of forearm supination and elbow flexion measured against the uninjured arm at 6 months of follow-up. No neurovascular complications have been occured.

CONCLUSION

Double intramedullary cortical button repair has shown to be a safe and reliable fixation method for distal biceps tendon rupture in a small series of patients. Preliminary results are encouraging.

Intra-individual variations in the bifurcation of the radial nerve and the length of the posterior interosseous nerve

Anatomical literature on the radial nerve predominantly features inter-individual variations, with comparatively few studies investigating intra-individual variations. The radial nerve has a complex and variable course, particularly in relation to the location at which the nerve bifurcates to form the superficial branch of the radial nerve and the posterior interosseous nerve. Variations of the radial nerve may change the way the nerve and its branches, their blood supply and nerve transmission respond to forces. This study investigated the presence of intra-individual differences in the bifurcation point of the radial nerve and the length of the posterior interosseous nerve from the bifurcation to the radial tunnel. Eighteen embalmed human cadavers were dissected to reveal the radial nerve. Measurements were taken from the level of the lateral humeral epicondyle to the bifurcation of the radial nerve, and from the bifurcation to the radial tunnel. All cadavers presented with intra-individual variations between the left and right limbs. Significant differences were found between the left and right limbs for the measurement from the lateral humeral epicondyle to the bifurcation (median difference = 18.0 mm; p = 0.016) but not for the measurement from the bifurcation to the radial tunnel (median difference = 7.0 mm; p = 0.396). In conclusion, the location of the radial nerve bifurcation is subject to both intra- and inter-individual variations. Its specific relationship to the lateral humeral epicondyle also varies, occurring both distal and proximal to the level of the epicondyle. Clinical implications of these findings warrant further investigation.

Ulnar neuropathy at the elbow: a review and single case cadaveric study

Introduction

Ulnar neuropathy at the elbow (UNE) causes sensory and motor dysfunction of the ulnar nerve and can lead to permanent loss of hand function. Hand therapists frequently encounter this pathology and are required to be cognisant of symptoms, diagnosis, therapeutic and surgical management. A detailed understanding of the anatomical structures will give the therapist greater expertise in managing this pathology.

Methods

A single case cadaveric study was undertaken to investigate known sites of ulnar nerve compression and observe the mechanisms by which compression occurs. A literature review reports on knowledge relating to the pathology, diagnosis, therapeutic and surgical management of UNE.

Results

Anatomic structures compressing the ulnar nerve are the Arcade of Struthers, the medial intermuscular septum, the cubital tunnel and the deep flexor aponeurosis. UNE is attributable to mechanical compression from fibrous and bony structures at these sites and to traction on the ulnar nerve from elbow flexion. Provocative tests are a useful tool in the diagnosis of UNE but should be used cautiously due to limitations in statistical accuracy. Conservative treatment approaches of splintage, ergonomic adaptations, education and neural mobilizations lack high-quality evidence but may have benefit primarily for early or mild to moderate disease. There is some evidence in support of conservative management in longer standing disease.

Discussion

Therapists play an important role in the diagnosis and management of UNE and should have a sound understanding of the relevant anatomy, pathology, diagnosis and treatment. Conservative treatment may be efficacious for UNE but lacks evidence from randomized, controlled trials. Further research is needed to verify current precepts and traditional approaches.

Magnetic resonance imaging of the long bones of the upper extremity

The long bones of the upper extremity are often overlooked in favor of addressing their intervening joints. However, there are a wide variety of pathologic processes that can involve these anatomic segments. To better understand the complex anatomy of the upper extremity, this article is divided into sections describing the osseous, muscular, and neurovascular anatomy of the arm and forearm using a compartmental approach. The discussion touches on a few common normal variants and their potential functional consequences. The upper extremity joints of the shoulder, elbow, and wrist are addressed separately.

Restoration of elbow extension after primary reconstruction in obstetric brachial plexus palsy

BACKGROUND

Elbow extension is important for the elbow joint, and it is more difficult to restore with microsurgery than elbow flexion. The purpose of this article is to describe the experience of the authors with elbow extension reconstruction in obstetric brachial plexus palsy patients. The outcomes were analyzed in relation to the type of brachial plexus lesion, timing of surgery, and the type of nerve reconstruction.

METHODS

Fifty-five children with obstetric brachial plexus palsy who underwent nerve reconstruction for elbow extension restoration were studied. The mean follow-up period was 6.4 years (range, 2-22 y). Reinnervation of the triceps muscle was accomplished with indirect neurotization of the posterior cord from intraplexus donors or with direct neurotization from extraplexus donors, such as the contralateral C7 and the intercostal nerves.

RESULTS

Thirty-seven (67%) of the 55 cases showed good or excellent results (>or=M3+). The average postoperative muscle grading for the triceps was 3.34+/-0.99 compared with 1.19+/-1.29 preoperatively (P<0.0001). Patients with C5 to C7 palsy achieved significantly stronger elbow extension than those with C5 to T1 palsy. In addition, the timing of surgery significantly influenced the final outcome.

CONCLUSIONS

Elbow extension is one of big challenges to be restored, especially in obstetric brachial plexus palsy. In early cases (within 6 mo) intraplexus reconstruction of the posterior cord can give excellent results. In later cases, or in cases of multiple avulsions, extraplexus motor donors, which selectively targeted the triceps, can give variable results.

Vein wrapping at cubital tunnel for ulnar nerve problems

BACKGROUND

Recurrent compression of the ulnar nerve in the cubital tunnel is a difficult problem and many solutions have been tried with variable success. Autologous vein graft wrapping is an alternative technique and it is recommended for the treatment of recalcitrant ulnar nerve compression in which 2 or more previous surgical procedures have failed to resolve the problem.

METHODS

Seventeen patients with recurrent cubital tunnel syndrome were treated with autologous saphenous vein wrapping. These patients had previously undergone simple decompression, decompression combined with medial epicondylectomy, anterior submuscular, or intramuscular transposition with internal neurolysis and had persistence of symptoms. Each patient underwent both subjective and objective evaluation.

RESULTS

Our clinical results on 17 patients have been encouraging. All patients reported significant pain relief, while improvements in grip strength and 2-point discrimination were also observed. There were no complications, other than transient leg swelling secondary to harvesting the saphenous vein graft from the leg.

CONCLUSION

This technique is not technically demanding, has low donor site morbidity, and leads to pain relief and high patient satisfaction.

An investigation of somatosensory profiles in work related upper limb disorders: a case-control observational study protocol

Background

Work related upper limb disorders constitute 45% of all occupational diseases and are a significant public health problem. A subgroup, non specific arm pain (NSAP), remains elusive in terms of understanding its pathophysiological mechanisms with its diagnosis based on the absence of specific clinical findings. One commonly proposed theory is that a neural tissue disorder is the primary dysfunction in NSAP and findings from previous studies lend some support to this theory. However, it is not clear if changes identified are simply a consequence of ongoing pain rather than due to specific neural changes. The presence of neuropathic pain has been investigated in several other musculoskeletal conditions but currently, there is no specific diagnostic tool or gold standard which permits an unequivocal diagnosis of neuropathic pain. The purpose of this study is to further describe the somatosensory profiles in patients with NSAP and to compare these profiles to a group of patients with MRI confirmed cervical radiculopathy who have been previously classified as having neuropathic pain.

Methods/Design

Three groups of participants will be investigated: Groups 1 and 2 will be office workers with either NSAP or cervical radiculopathy and Group 3 will be a control group of non office workers without upper limb pain. Participants will undergo a clinical assessment, pain questionnaires (LANSS, Short Form McGill, DASH and TSK) and quantitative sensory testing comprising thermal detection and pain thresholds, vibration thresholds and pressure pain thresholds.

Discussion

The spectrum of clinically suspected neuropathic pain ranges from more obvious conditions such as trigeminal neuralgia to those with vague signs of nerve disorder such as NSAP. A thorough description of the somatosensory profiles of NSAP patients and a comparison with a more defined group of patients with evidence of neuropathic pain will help in the understanding of underlying neurophysiology in NSAP and may influence future classification and intervention studies relating to this condition.

Peripheral nerve injuries of the pediatric hand: issues in diagnosis and management

Peripheral nerve injuries resulting in significant neural disruption frequently present complex management challenges. Typically the product of fracture, dislocation, or crush injuries, pediatric peripheral nerve injuries may be difficult to accurately characterize. Thorough clinical examination coupled with electromyogram and neurophysiologic studies are extremely useful. When possible, primary repair should be attempted. If, however, defect size precludes primary reanastomosis, use of a nerve graft may be advantageous. Alternatively, nerve conduits, such as veins, pseudosheaths, and bioabsorbable tubes, are also effective facilitators of nerve regeneration. Although nerve injuries of the pediatric hand often present complex challenges, a thorough knowledge of diagnostic methods and advances in surgical interventions offers better outcomes.

Anatomic relationship of the radial nerve to the elbow joint: clinical implications of safe pin placement

The percutaneous placement of lateral distal humeral pins risks injury to the radial nerve. We aimed to provide a reliable and safe parameter for the insertion of lateral distal humeral pins. A secondary aim of this study was to investigate the effect of pin/screw placement in the intended zone of fixation at the lateral distal humerus. We dissected 70 fresh cadaveric upper limbs and the radial nerve was identified and its course followed into the anterior compartment. The point where the radial nerve crosses humerus in mid lateral plane was identified and the distance between this point and lateral epicondyle was measured, as was the maximum trans-epicondylar distance, along with the olecranon fossa height. Statistical analysis was performed using the Pearson correlation coefficient. The average trans-epicondylar distance was measured at 62 +/- 6 mm (range 52-78 mm), and the average lateral radial nerve height was 102 +/- 10 mm (range 75-129 mm). The ratio of the lateral nerve height to the trans-epicondylar distance was an average of 1.7 +/- 0.2 (range 1.4-2.0). The Pearson correlation coefficient between the lateral nerve height and the trans-epicondylar distance was r = 0.95. A relative dimension, the trans-epicondylar distance is both reliable and easily accessible to the operating surgeon. The absolute safe zone for pin entry into the lateral distal humerus is that area lying within the caudad 70% of a line, equivalent in length to the patient's own trans-epicondylar distance, when projected proximally from the lateral epicondyle.

Ultrasonographic examination of the carpal canal in dogs

The aim of this study was to determine the course of the median nerve and its adjacent structures in the carpal canals of 8 healthy dogs by using high-frequency transducers. Before performing ultrasonography, the transverse and posteroanterior diameters as well as the perimeter of the carpus were measured at just proximal to the side of the carpal pad. The anatomical structures were then determined at two levels of the carpal canal, which were named the proximal and distal levels, on the transverse sonograms. The cross-sectional areas, perimeters and the transverse and posteroanterior diameters of the median nerve were measured at these levels. Although all the measurements were larger at the proximal level, significant differences between the proximal and distal levels were determined for the cross-sectional area, the perimeter and the transverse diameter of the median nerve. On the transverse sonogram, the deep digital flexor tendon was seen in almost the center of the carpal canal like a comma shape and also it had a small concavity on the caudal side. The superficial digital flexor tendon was seen as an ovoid shape on the transverse sonograms and it was located nearly at the posterior side of the carpal canal. Both tendons were seen as intermediate-grade echogenic structures. The median artery was located inside of the concavity of the deep digital flexor tendon. Also, the median nerve was seen at the posteromedial side of the median artery. As a result of this study, the cross-sectional areas of the median nerve ranged between 1.01-2.68 mm² at the proximal level and between 0.93-1.91 mm² at the distal level.

The effect of drilling angle on posterior interosseous nerve safety during open and endoscopic anterior single-incision repair of the distal biceps tendon

PURPOSE

The purpose of this study was to define a safe trajectory with regard to iatrogenic posterior interosseous nerve (PIN) injury when drilling the bicipital tuberosity for EndoButton repair (Smith & Nephew Endoscopy, Andover, MA) of distal biceps tendon ruptures.

METHODS

Ten cadaveric forearms were dissected. The bicipital tuberosity was exposed and the biceps tendon detached. The supinator and PIN were exposed dorsally. A K-wire was drilled perpendicular to the surface of the tuberosity. By use of digital calipers, the distance from the exit point of this wire to the PIN was measured. The length of the bone tunnel was also measured. This wire was removed, and a second was drilled from the same starting point but directed 30 degrees ulnarly. Measurements were repeated. A Wilcoxon signed rank test was used to compare the distances of the K-wire to the PIN and the tunnel lengths for both trajectories.

RESULTS

With the perpendicular wire, the mean distance to the PIN was 11.1 mm. When directed 30 degrees ulnarly, the mean distance was 16.4 mm. The difference was significant (P < .001). The mean bone tunnel lengths for the 2 trajectories were 17.8 mm and 18.1 mm; this was not found to be significant (P = .508).

CONCLUSIONS

When drilling the bicipital tuberosity, we advocate starting at a center-center position on the face of the tuberosity, holding the forearm in maximum supination, and aiming 30 degrees ulnarly to decrease the risk to the PIN. This trajectory does not decrease the bone tunnel length available for implants.

CLINICAL RELEVANCE

This cadaveric anatomic study establishes safety from iatrogenic PIN injury during drilling of the bicipital tuberosity for the purpose of open or endoscopic EndoButton repair of distal biceps tendon ruptures.

Anomalous median nerve position dorsal to the flexor tendons in a patient with spastic hemiplegia and wrist pain: case report

We report an anomalous dorsally positioned median nerve within the carpal tunnel in a 25-year-old spastic hemiplegic man associated with chronic wrist pain.

Normal MR imaging anatomy of the elbow

The functional complexity achieved at the elbow is a reflection of the sophisticated architecture that embodies this articulation. In addition to challenging anatomic relationships to conceptualize, there are many anatomic variations that exist in the osseous, capsular, and muscular structures. This article offers a detailed description of the structural and imaging anatomy of the elbow, information that establishes the foundation of imaging interpretation of internal derangements.