Guyon's Canal Research Articles

Variations of the ulnar nerve within the ulnar tunnel and palm in a select South African population

Variations of the ulnar nerve within the ulnar tunnel and palm in a select South African population

A Case Report of Proximal Palm Giant Lipoma Leading to Double Nerve Compression, with a Brief Literature Review

Summary: Lipomas are frequently found as benign neoplasms in humans, mainly in the head, neck, and upper limb regions. Because of their rare occurrence in hands and digits, such cases attract researchers’ attention. A case description of a 28-year-old Saudi male patient is presented with a large-size lipoma at the distal forearm, carpal tunnel, and Guyon canal area, with numbness of the central three digits and grip strength weakness of his left hand. The nature of the lesion was a benign, subcutaneous, multilobulated lipoma, removed surgically to prevent malignant transformation and deterioration in neuropathy.

Surgical Anatomy of the Supraretinacular Fat Pad: Sensory Innervation and Preservation in Open Carpal Tunnel Release

BACKGROUND AND OBJECTIVES: Postoperative pain may occur following open carpal tunnel release (OCTR). Various causes have been postulated. During OCTR, adipose tissue located between the palmar aponeurosis and the flexor retinaculum is exposed. It is unknown whether damage to this pad of supraretinacular fat (SRF) might contribute to postoperative palmar pain or tenderness. We studied the sensory innervation of the SRF exposed in OCTR to assess whether SRF damage could potentially generate pain. METHODS: A microanatomic dissection of the innervation and vascular supply of the SRF was performed in 25 embalmed human cadaveric upper limbs. Eight fat pads were removed en bloc for histological evaluation. Three-dimensional reconstructions were made based on immunohistochemically stained sections using computer-assisted microscopy. RESULTS: The SRF is the radial continuation of the hypothenar fat pad that covers the neurovascular bundle in the Guyon canal. The fat pad is richly innervated and contains Pacinian corpuscles. The sensory innervation originates exclusively from the ulnar nerve (palmar branch) and its vascular supply from the ulnar artery. The integrity of the SRF can be preserved by detaching it from the flexor retinaculum in a radial to ulnar fashion. CONCLUSION: The SRF, which is exposed during OCTR, is richly innervated by sensory fibers from the ulnar nerve. It is the radialmost extension of the hypothenar fat pad. In view of its rich innervation, damage to the SRF during OCTR might generate postoperative pain. Preserving its integrity during OCTR is technically possible and even simplifies the procedure. Clinical trials are needed to corroborate whether preservation of the SRF during OCTR indeed makes a clinical difference in postoperative pain generation.

Double entrapment neuropathy of the ulnar nerve at the elbow and the wrist : double crush syndrome?

BackgroundDouble crush syndrome refers to a nerve in the proximal region being compressed, affecting its proximal segment. Instances of this syndrome involving ulnar and cubital canals during ulnar neuropathy are rare. Diagnosis solely through clinical examination is challenging. Although electromyography (EMG) and nerve conduction studies (NCS) can confirm neuropathy, they do not incorporate inching tests at the wrist, hindering diagnosis confirmation. We recently encountered eight cases of suspected double compression of ulnar nerve, reporting these cases along with a literature review.MethodsThe study included 5 males and 2 females, averaging 45.6 years old. Among them, 4 had trauma history, and preoperative McGowan stages varied. Ulnar neuropathy was confirmed in 7 cases at both cubital and ulnar canal locations. Surgery was performed for 4 cases, while conservative treatment continued for 3 cases.ResultsIn 4 cases with wrist involvement, 2 showed ulnar nerve compression by a fibrous band, and 1 had nodular hyperplasia. Another case displayed ulnar nerve swelling with muscle covering. Among the 4 surgery cases, 2 improved from preoperative McGowan stage IIB to postoperative stage 0, with significant improvement in subjective satisfaction. The remaining 2 cases improved from stage IIB to IIA, respectively, with moderate improvement in subjective satisfaction. In the 3 cases receiving conservative treatment, satisfaction was significant in 1 case and moderate in 2 cases. Overall, there was improvement in hand function across all 7 cases.ConclusionTypical outpatient examinations make it difficult to clearly differentiate the two sites, and EMG tests may not confirm diagnosis. Therefore, if a surgeon lacks suspicion of this condition, diagnosis becomes even more challenging. In cases with less than expected postoperative improvement in clinical symptoms of cubital tunnel syndrome, consideration of double crush syndrome is warranted. Additional tests and detailed EMG tests, including inching tests at the wrist, may be necessary. We aim to raise awareness double crush syndrome with ulnar nerve, reporting a total of 7 cases to support this concept.

Elastography of nerves in the wrists of cyclists.

This study aimed to investigate changes in the elasticity of the median and ulnar nerves in cyclists. The study included 30 cyclists and 2 non-biking reference groups that included 32 healthy volunteers and 32 individuals with ulnar nerve entrapment neuropathies. All participants underwent physical, ultrasonographic, and elastographic examinations including assessment of nerve cross-sectional area (CSA) and stiffness (SWE). The cyclists' group was tested before and after a 2-hour workout. The values of ulnar nerve CSA and stiffness in Guyon's canal in resting cyclists were 5.30 ± 1.51 mm2 and 49.05 ± 11.18 kPa, respectively. These values were significantly higher than in the healthy volunteers, but not higher than in the nerve entrapment group. Median nerve CSA and stiffness at rest were 9.10 ± 2.61 mm2 and 38.54 ± 14.87 kPa, respectively. Both values were higher than respective values in the healthy group. Cycling induced an increase in all these parameters, although the increase in nerve stiffness was more noticeable than in CSA. The elasticity of the median and ulnar nerve in cyclists remains within normal limits, questioning the belief that cyclists are at risk of nerve palsy in Guyon's canal. However, cycling workout does exert compression, resulting in transient oedema of both nerves. The dynamics of changes was more noticeable in SWE examination than in conventional ultrasound, which may depend on SWE sensitivity.

A clinical case of transthyretin amyloidosis with manifestations of seronegative arthritis

A clinical case of transthyretin amyloidosis with manifestations of seronegative arthritis

Simultaneous Versus Staged Surgery for Double Crush Syndrome of Cervical Radiculopathy and Peripheral Nerve Compression at the Wrist: A Retrospective Single-Center Study.

Retrospective single-center study. To evaluate the results of surgical treatment in patients with double crush syndrome associated with cervical radiculopathy and upper limb peripheral nerve compression after staged and simultaneous operations. Currently, choosing the optimal diagnostic and therapeutic modalities for treating patients with double crush syndrome remains unresolved. The study included 79 patients with double crush syndrome (cervical radiculopathy and syndrome of Guyon's canal or Carpal tunnel syndrome). Two independent groups were studied: In the Staged Group (n=35), we performed a cervical decompression with stabilization and peripheral nerve decompression at separate days due to ongoing clinical symptoms (average interval between interventions being 22 (18;26) days). In the simultaneous group (n=33), we performed both the cervical spine surgery as well as the peripheral nerve procedures in one surgical session. Total operative time, estimated blood loss, length of hospitalization, complications, and clinical data (NDI score, SF-36, VAS neck pain score, VAS arm pain score, Disabilities of Arm, Shoulder, and Hand (DASH) score, and Macnab scale) were compared. We used the Mann-Whitney (MW) test for intergroup comparisons, the Wilcoxon criterion for dependent samples, and the Fisher exact test for binomial parameters. There was a significantly lower operative time, duration of inpatient treatment, and temporary disability in the simultaneous group (P=0.01, P=0.04, and P=0.006, respectively). Comparative analysis did not reveal significant intergroup differences using NDI, VAS, and DASH ( P >0.05), whereas, at discharge, significantly better clinical parameters were appreciated for the simultaneous group using SF-36 and Macnab scores ( P =0.04 and P =0.03, respectively). At the last follow-up, an intra-group analysis revealed comparable clinical effectiveness between the two approaches ( P >0.05). Comparison of the effectiveness of simultaneous and staged surgery revealed comparable long-term clinical outcomes. However, simultaneous surgery conveys clinically important advantages in terms of surgical time, anesthesia duration, length of hospitalization, and patient disability. 3.

Rare nerve compression neuropathies

In regard to the complex anatomical relationship of peripheral nerves and muscles, tendons, fasciae as well as their long course within those anatomical structures and additional close contact to bony structures, they are prone to suffer from local compression syndromes. Hence creating a vast majority of entrapment syndromes - well described in literature for almost every single nerve. The purpose of this article is to give an overview of symptoms, signs, diagnostic studies and treatment options, addressing especially the less known syndromes. Compression syndromes of the upper arm and shoulder region include the suprascapular nerve syndrome the compression of the axillary nerve within the spatium quadrilaterale and the compression of the long thoracic nerve at the chest wall. The upper extremity offers a variety of infrequent entrapment syndromes, as the pronator teres syndrome and anterior interosseus syndrome, both resulting from pressure to the median nerve in the forearm. Compression neuropathy in the course of the radial nerve in the distal upper extremity is also known as supinator syndrome. Guyon's canal syndrome is the ulnar side equivalent to the well-known carpal tunnel syndrome. In the case of a Cheiralgia paresthetica, a compression of a sensory branch of the superficial radial nerve can be seen. In the lower extremities, a variety of nerves especially in the groin and thigh area can be compressed as they pass through the narrow spaces between the abdominal muscles or underneath the inguinal ligament. Compression of the lateral femoral cutaneous nerve is the most common syndrome. Compression syndromes of the femoral and obturator nerves are most often iatrogenic. Pain around the knee, especially the lateral part and following orthopedic procedures of the knee, can arise from a compression or a lesion of a small infrapatellar branch of the saphenous nerve. Another probably underdiagnosed syndrome is piriformis syndrome, resulting from an entrapment of the sciatic nerve as it passes through certain muscular structures. In the distal lower extremity, the peroneal and tibial nerves can be compressed at multple sites, clinically known as peroneal nerve paralysis resulting from nerve compression around the fibular head, the anterior and posterior tarsal tunnel syndrome, and Morton's metatarsalgia.

Radiofrequency Ablation of Palmar Digital Branches of Ulnar Nerve in a Patient with Ulnar Neuropathy

Ulnar Tunnel Syndrome (UTS) is ulnar neuropathy at the wrist or hand typically caused by ganglion cysts, lipomas, wrist or hand compression, carpal bone fractures, carpal tunnel syndrome, or anything else that can impinge on the nerve. The symptoms of UTS can be uncomfortable and debilitating, with numbness and tingling of the 4th and 5th digits being the most common. Weakness of the ulnar portion of the hand can lead to decreased grip strength. UTS is typically managed with conservative treatment including anti-inflammatory oral medications, splinting, physical therapy, activity modification, acupuncture, and stretching. Second line treatment includes corticosteroid injections, although these have shown to have little efficacy. Surgery is also an option but may lead to iatrogenic ramifications. Radiofrequency ablation (RFA) is a treatment modality used for chronic pain, which utilizes heat to target nociceptive fibers. Traditionally, RFA is used in treating cervical and lumbar radiculopathy, but it is less studied in peripheral nerve areas. This case report examines a patient who had clinically significant pain relief after RFA to the palmar digital branches of the ulnar nerve. The patient was 63-year-old male who presented with left ulnar neuropathy that had been ongoing for 3 years. Despite conservative management, his symptoms of pain, paresthesia, and weakness persisted. The patient then elected to have a left cubital tunnel release at the elbow with anterior subcutaneous transposition. The surgery provided relief for three months but then led to worsening contractures and pain in the 4th and 5th digits of the left hand. Due to persistent symptoms after conservative management and surgical intervention, he was referred to interventional pain clinic. A decision was made to trial a digital nerve block of the left medial and lateral digital palmar nerves. Following the nerve block, the patient reported 100% improvement in pain and increased range of motion and function. Four weeks later, the patient returned for a radiofrequency ablation of the same nerves. In the week following the procedure, the patient reported that the pain in the little finger was entirely resolved. While radiofrequency ablation has become increasingly popular for the treatment of chronic back pain, its use in peripheral nerve pain has been limited to case reports and few randomized control trials. This case report highlights the successful use of radiofrequency ablation in the treatment of little finger pain and ulnar neuropathy by targeting the median and lateral branches of the palmar digital nerve.

High-resolution ultrasound and magnetic resonance imaging of ulnar nerve neuropathy in the distal Guyon tunnel

ObjectiveThe aim of the present study is to describe the ultrasound (US) and magnetic resonance imaging (MRI) findings in patients with neuropathies affecting the deep (DB) and superficial (SB) branches of the Ulnar nerve (UN) and to investigate the potential role of imaging modalities in the diagnostic workup of these conditions.Materials and methodsWe screened our institutional imaging database to identify patients with a diagnosis of UN mononeuropathy, and among them, we reviewed the cases where US disclosed pathological findings affecting the UN terminal divisions. In this latter subgroup, we retrieved available data on MRI and electrodiagnostic tests performed by the patients during the diagnostic workup. All the patients were evaluated with US machines equipped with 17–5-MHz, 18–4-MHz, 24–8-MHz, or 22–8-MHz probes. MRI exams were performed on a 3-T unit equipped with a 64-channel head RF coil.ResultsAmong 166 patients with UN mononeuropathy, we retrieved 15 patients (9%) for which US detected pathological findings affecting the UN terminal divisions, consisting of 7 cases of DB neuropathy, 4 cases of SB neuropathy, and 4 cases of combined neuropathy involving both nerves. Seven (46.7%) patients were submitted to MRI to integrate US findings. Among patients with SB and DB neuropathies, imaging allowed the identification of 7 traumatic nerve injuries, 2 nerve tumors, and 6 entrapment neuropathies, including 4 cases of nerve compression by a ganglion cyst.ConclusionHigh-resolution US and MRI are accurate modalities for the investigation of patients with SB/DB neuropathy, can provide critical information on the cause of nerve damage, and guide therapeutic decisions.Critical relevance statementHigh-resolution US and MRI are accurate modalities for the investigation of patients with superficial/deep branch of the ulnar nerve neuropathy. In the proper setting, US may be regarded as a first-line approach in patients with suspected neuropathies affecting these small branches.Key points• Neuropathies affecting the distal ulnar nerve often require multimodal investigations.• US and MRI can provide detailed morphological information about the terminal branches of the ulnar nerve.• US may be considered as a first-line approach in suspected distal ulnar nerve neuropathies.Graphical

Recurrence of ulnar tunnel syndrome: Long-term clinical and functional results of surgical management using revision neurolysis and subcutaneous anterior transposition

ObjectiveRecurrence after primary ulnar tunnel syndrome surgery is observed in 1.4%–25% of patients. However, the outcome of revision surgery is uncertain and limited. This study aimed to assess the clinical and functional outcomes of neurolysis combined with anterior subcutaneous transposition in cases of recurrence. Patients and methodsThis retrospective single-center study included patients who were operated on for iterative ulnar tunnel syndrome at the elbow between January 1996 and December 2020, with a minimum follow-up of 24 months. Demographic data, pre- and post-operative clinical evaluations, surgical details, and satisfaction levels were collected. ResultsTwenty-eight patients were reviewed. Mean follow-up was 11.7 years (range, 2.1–26.4 years). The secondary procedure led to significant improvement in mean Quick-DASH score, from 25.3 (range, 11–50) to 20.0 (range, 11–49) (p = 0.023), with a satisfaction rate of 78.5%. Symptoms of pain (p = 0.033), amyotrophy (p = 0.013), hypoesthesia (p < 0.01), and paresthesia (p < 0.001) also showed significant improvement. There were 7 cases of failure (25.0%). ConclusionThe combination of neurolysis and anterior subcutaneous transposition was a reliable technique, improving clinical outcome in recurrent ulnar tunnel syndrome after previous surgery. Level of evidenceIV — retrospective study.

Demographic heterogeneity in valgus angulation of the proximal ulnar canal in relation to the flexion-extension axis.

The long-term outcome of total elbow arthroplasty remains unsatisfactory because of loosening and polyethylene wear, which could be caused by malpositioning of the ulnar component. When introducing an ulnar component, 2 different angles should be considered in the coronal plane: the valgus angulation of the proximal ulna in relation to the flexion-extension axis (FE-axis) and the intramedullary varus angulation in relation to the FE-axis. Currently, available TEA designs may not always be able to reconstruct the FE-axis because of the morphologic variability of the ulna. This study aimed to determine the demographic variability of the ulna and the relation between the 2 angulations in the frontal plane based on 3-dimentional computed tomography (CT) reconstructions of the elbow joint of healthy volunteers. Computed tomography scans of 36 left elbows of healthy volunteers were obtained (20 men and 16 women). The scans were segmented and analyzed using the Mimics Research 20.0 software. A local coordinate system was created based on the FE-axis of the elbow and the ulna's longitudinal axis. The measurements were conducted using the 3-Matic Research 12.0 software. The valgus angulation of the proximal medullary canal was on average 16° in men but 12° in women and ranged between 5° and 21°. The varus angulation of the medullary cavity could be determined at 57 mm in men and 64 mm in women from the FE-axis. This angulation was on average 10° in men and 7° in women. There was no significant correlation between this angle and the length of the ulna or the point of varus angulation. This study found a wide range of valgus angulation of the proximal ulnar canal in relation to the FE-axis. The available elbow implant designs are discordant with the mean valgus angulation of the proximal ulna found in this study, and the valgus laxity of the implants does not cover the variability in the population.

SYNDROME DU TUNNEL CUBITAL DUE AU MUSCLE ANCONEUSEPITROCHLEARIS : A PROPOS DUN CAS

Ulnar tunnel syndrome in the elbow is a common ductal neuropathy of the upper limb. The discovery of the anconeusepitrochlearis muscle may be an etiology of this compressive neuropathy, whose management in the event of failure of medical treatment consists of resection of this muscle to relieve the ulnar nerve and avoid sometimes dramatic functional consequences.

Compression of the Ulnar Nerve Following Carpal Tunnel Release

Given the proximity and shared structures of Guyon's canal and the carpal tunnel, compression of the ulnar nerve is a rarely observed but possible complication of carpal tunnel release. In this case report, a patient underwent previous carpal tunnel release and immediately experienced ipsilateral hand weakness in keeping with an ulnar nerve compression syndrome. Clinical, electrodiagnostic, and magnetic resonance imaging findings after carpal tunnel release demonstrated a compression or injury to the deep motor branch of the ulnar nerve not previously present. Subsequent release of Guyon's canal identified a separate compartment of the deep motor branch of the ulnar nerve within the ulnar leaflet of the transverse carpal ligament. After the release of the motor branch from this compartment, the patient experienced recovery from their neuropathic symptoms. This case report outlines the relevant anatomy and clinical data surrounding an anomalous compartment of the deep motor branch of the ulnar nerve.

Radially Displaced Perilunate Injuries: A Report of Two Cases.

We present two unusual cases of radially displaced perilunate dislocations, one of which involved acute ulnar nerve compression requiring Guyon's canal release. The first case underwent closed reduction and cast immobilization but developed scapholunate instability, necessitating secondary ligament reconstruction. The second case, treated with open reduction and fixation, resulted in persistent volar intercalated segment instability of the proximal row and ulnar nerve paresthesia 1 year after surgery.

Neurectomy of the Nerve of Henle Associated with Periarterial Sympathectomy for Management of Intractable Raynaud Phenomenon.

In periarterial sympathectomy for intractable Raynaud phenomenon, the extent of adventitectomy and postoperative outcomes and hand perfusion assessment tools remain debatable. The authors evaluated the outcome of neurectomy of the nerve of Henle combined with ulnar tunnel release and periarterial adventitectomy in the treatment of refractory Raynaud phenomenon using objective measurements and patient-reported outcomes. Nineteen patients with 20 affected hands were prospectively enrolled and underwent the proposed procedures from 2015 to 2021. Relevant data, including Michigan Hand Outcomes Questionnaire and 36-Item Short Form health questionnaire scores, were documented for analysis during a 3-year follow-up. The average ingress value of the three measured fingers (index, long, and ring) on indocyanine green angiography increased after surgery ( P = 0.02). The median number of ulcers decreased ( P < 0.001), and the median digital skin temperature increased ( P < 0.001). Questionnaire scores showed improvement in physical aspects, such as overall hand function ( P ≤ 0.001), activities of daily living ( P = 0.001), work performance ( P = 0.02), pain ( P < 0.001), physical function ( P = 0.053), and general health ( P = 0.048), and mental aspects, such as patient satisfaction ( P < 0.001) and mental health ( P = 0.001). The average indocyanine green ingress value of the three measured fingers significantly correlated with the patient-reported outcomes, including overall hand function ( r = 0.46, P = 0.04), work performance ( r = 0.68, P = 0.001), physical function ( r = 0.51, P = 0.02), and patient satisfaction ( r = 0.35, P= 0.03). The proposed surgical procedures provided satisfactory outcomes, both subjectively and objectively, over a follow-up period of up to 3 years. Indocyanine green angiography may provide rapid and quantitative measurements for perioperative hand perfusion assessment. Therapeutic, IV.

Anterior Interosseus to Ulnar Motor Nerve Transfers: A Canadian Perspective.

The anterior interosseus nerve (AIN) to ulnar motor nerve transfer has been popularized as an adjunct to surgical decompression in patients with severe cubital tunnel syndrome (CuTS) and high ulnar nerve injuries. The factors influencing its implementation in Canada have yet to be described. An electronic survey was distributed to all members of the Canadian Society of Plastic Surgery (CSPS) using REDCap software. The survey examined 4 themes: previous training/experience, practice volume of nerve pathologies, experience with nerve transfers, and approach to the treatment of CuTS and high ulnar nerve injuries. A total of 49 responses were collected (12% response rate). Of all, 62% of surgeons would use an AIN to ulnar motor supercharge end-to-side (SETS) transfer for a high ulnar nerve injury. For patients with CuTS and signs of intrinsic atrophy, 75% of surgeons would add an AIN-SETS transfer to a cubital tunnel decompression. Sixty-five percent would also release Guyon's canal, and the majority (56%) use a perineurial window for their end-to-side repair. Eighteen percent of surgeons did not believe the transfer would improve outcomes, 3% cited lack of training, and 3% would preferentially use tendon transfers. Surgeons with hand fellowship training and those less than 30 years in practice were more likely to use nerve transfers in the treatment of CuTS (P < .05). Most CSPS members would use an AIN-SETS transfer in the treatment of both a high ulnar nerve injury and severe CuTS with intrinsic atrophy.

Ultrasound Imaging and Guidance for Distal Peripheral Nerve Pathologies at the Wrist/Hand.

Ultrasound has emerged as a highly valuable tool in imaging peripheral nerve lesions in the wrist region, particularly for common pathologies such as carpal tunnel and Guyon's canal syndromes. Extensive research has demonstrated nerve swelling proximal to the entrapment site, an unclear border, and flattening as features of nerve entrapments. However, there is a dearth of information regarding small or terminal nerves in the wrist and hand. This article aims to bridge this knowledge gap by providing a comprehensive overview concerning scanning techniques, pathology, and guided-injection methods for those nerve entrapments. The median nerve (main trunk, palmar cutaneous branch, and recurrent motor branch), ulnar nerve (main trunk, superficial branch, deep branch, palmar ulnar cutaneous branch, and dorsal ulnar cutaneous branch), superficial radial nerve, posterior interosseous nerve, palmar common/proper digital nerves, and dorsal common/proper digital nerves are elaborated in this review. A series of ultrasound images are used to illustrate these techniques in detail. Finally, sonographic findings complement electrodiagnostic studies, providing better insight into understanding the whole clinical scenario, while ultrasound-guided interventions are safe and effective for treating relevant nerve pathologies.

Load analysis of hands and feet while using different types of crutches with various leg's weight bearing.

The study aimed to define the load on hands using various commonly used types of crutches while walking with a full load on both legs (FL), with 20 kg partial load (PL), or with the left leg wholly unloaded (UL). Twenty-six healthy subjects used crutches with ergonomic handles, with anatomic handles (wider and softer bearing surface), and arthritis crutches (horizontal supporting area for the forearm). Sensor mats between hand and handles continuously measured the load transmitted, while sensor soles in the shoes recorded the ground reaction forces simultaneously. The load on the palm and separately the radial and ulnar halves of the palm were analyzed. With arthritis crutches, significantly lower load was transferred to the hands compared to forearm crutches (FL 3% vs. 25% of body weight, PL 8% vs. 87%, UL 12% vs. 103%). The load on hands increased significantly from FL to PL and UL for both types of crutches. The ipsilateral left hand had to bear significantly more load than the right hand. However, the feet's time-ground reaction curves showed more irregularities, and PLon the left leg was significantly higher with arthritis crutches. Anatomic handles reduced the load on the ulnar half of the palm (FL 3% vs. 5%, PL 13% vs. 18%, UL 17% vs. 23%); the radial half of the palm had a similar load to bear with both types of handles (11/11%, 31/32%, 34/35%). Arthritis crutches allow unburdening hands at the expense of gait stability. Anatomic handles reduce the load on the Guyon's canal.

Ultra-high-definition (22 MHz) ultrasound of the ulnar nerve: additional value and normative data.

We studied 30 healthy volunteers (60 arms), categorized into three age groups with equal numbers to verify if a 22 MHz compared with a 15 MHz ultrasound transducer has additional value for studying the intraneural architecture of the ulnar nerve throughout its course. At six sites, there were no differences in cross-sectional area measurements between the two transducers. With both, the cross-sectional area was significantly larger at the medial epicondyle compared with the other sites and smaller at the mid-forearm and Guyon's canal compared with the mid-upper arm. With higher age the cross-sectional area significantly increased. Significantly more fascicles were visible distal to the medial epicondyle compared with more proximal sites, as well as in men compared with women. Finally, higher body weight was related to a significantly smaller number of fascicles being seen. A 22 MHz transducer depicts more details of the intraneural architecture than a 15 MHz transducer. Our data can be used as normative data or reference values in analysing ulnar nerve pathology.Level of evidence: II.