The Prevalence of Anatomical Variations of the Median Nerve in the Carpal Tunnel: A Systematic Review and Meta-Analysis

Compressive Neuropathies of the Upper Extremity: Anatomy for the Peripheral Nerve Surgeon

Advance knowledge of anatomy is a prerequisite for the peripheral nerve surgeon. This article serves to provide an outline of anatomic regions where nerve entrapment or compression can occur. Each section is subdivided into anatomic regions where the etiology, indications, and relevant and aberrant anatomy are discussed, as well as common surgical approaches to the problematic anatomic site. The purpose is to provide an overview for the peripheral nerve surgeon and offer a valuable resource to provide a better understanding and optimal care for this patient population.

Warning Signs: Occult Diabetes and Dysglycemia in the Hand Surgery Patient Population

BACKGROUND

Diabetes mellitus often exists for many years prior to diagnosis, and very little is known about the role of the prediagnosis stage of metabolic impairment in contributing to hand and upper-extremity pathology. The goal of this study is to determine the prevalence of undiagnosed glucose dysregulation in patients presenting with the 2 most commonly treated conditions of the hand and wrist.

METHODS

A retrospective study was performed of hand surgery patients with no established diagnosis of prediabetes or diabetes referred for a 2-hour glucose tolerance test according to American Diabetes Association criteria. Patients were divided into 3 groups: peripheral neuropathies, trigger finger, and controls with various upper-extremity diagnoses. Rates of undiagnosed prediabetes and diabetes were compared between groups, including subgroup analysis of patients based on unilateral or bilateral presentation. Binary logistic regression analysis was also used to calculate odds ratios for multiple variables.

RESULTS

Patients with neuropathy had a significantly higher incidence of undiagnosed dysglycemia compared with the control group. Of those patients, 51.3% were prediabetic and 12.8% were diabetic. The control group had significantly lower rates. Within the bilateral neuropathy patients, 59.6% had prediabetes and 15.4% had diabetes, versus 34.6% with prediabetes and 7.7% with diabetes in the unilateral group.

CONCLUSIONS

Hand surgeons encounter a patient population with high rates of undiagnosed prediabetes and diabetes, with some presentations as much as 6 times higher than the general population. Certain patient presentations should prompt appropriate diagnostic testing and referral, especially those presenting with bilateral compression neuropathy and elevated body mass index.

High-Resolution Magnetic Resonance Neurography at 7T: A Pilot Study of Hand Innervation

The emergence of 7T clinical MRI technology has sparked our interest in its ability to discern the complex structures of the hand. Our primary objective was to assess the sensory and motor nerve structures of the hand, specifically nerves and Pacinian corpuscles, with the dual purpose of aiding diagnostic endeavors and supporting reconstructive surgical procedures. Ethical approval was obtained to carry out 7T MRI scans on a cohort of volunteers. Four volunteers assumed a prone position, with their hands (N = 8) positioned in a "superman" posture. To immobilize and maintain the hand in a strictly horizontal position, it was affixed to a plastic plate. Passive B0 shimming was implemented. Once high-resolution 3D images had been acquired using a multi-transmit head coil, advanced post-processing techniques were used to meticulously delineate the nerve fiber networks and mechanoreceptors. Across all participants, digital nerves were consistently located on the phalanges area, on average, between 2.5 and 3.5 mm beneath the skin, except within flexion folds where the nerve was approximately 1.8 mm from the surface. On the phalanges area, the mean distance from digital nerves to joints was approximately 1.5 mm. The nerves of the fingers were closer to the bone than to the surface of the skin. Furthermore, Pacinian corpuscles exhibited a notable clustering primarily within the metacarpal zone, situated on the palmar aspect. Our study yielded promising results, successfully reconstructing and meticulously describing the anatomy of nerve fibers spanning from the carpus to the digital nerve division, alongside the identification of Pacinian corpuscles, in four healthy volunteers (eight hands).

Improved visualization of median, ulnar nerves, and small branches in the wrist and palm using contrast-enhanced magnetic resonance neurography

Background

Magnetic resonance imaging of peripheral nerves in the wrist and palm is challenging due to the small size, tortuous course, complex surrounding tissues, and accompanying blood vessels. The occurrence of carpal palmar lesions leads to edema, swelling, and mass effect, which may further interfere with the display and identification of nerves.

Objective

To evaluate whether contrast-enhanced magnetic resonance neurography (ceMRN) improves the visualization of the morphology and pathology of the median, ulnar nerves, and their small branches in the wrist and palm.

Design

An observational study.

Methods

In total 57 subjects, including 36 volunteers and 21 patients with carpal palmar lesions, were enrolled and underwent ceMRN and non-contrast MRN (ncMRN) examination at 3.0 Tesla. The degree of vascular suppression, nerve visualization, diagnostic confidence, and lesion conspicuity was qualitatively assessed by two radiologists. Kappa statistics were obtained for inter-reader agreement. The signal-to-noise ratio, contrast ratio (CR), and contrast-to-noise ratio (CNR) of the median nerve were measured. The subjective ratings and quantitative measurements were compared between ncMRN and ceMRN.

Results

The inter-reader agreement was excellent (k > 0.8) for all qualitative assessments and visualization assessment of each nerve segment. Compared with ncMRN, ceMRN significantly improved vascular suppression in volunteers and patients (both p < 0.001). The ceMRN significantly enhanced nerve visualization of each segment (all p < 0.05) and diagnostic confidence in volunteers and patients (both p < 0.05). The ceMRN improved lesion conspicuity (p = 0.003) in patients. Quantitatively, ceMRN had significantly higher CRs of nerve versus subcutaneous fat, bone marrow, and vessels and CNR of nerve versus vessel than ncMRN (all p < 0.05).

Conclusion

The ceMRN significantly improves the visualization of peripheral nerves and pathology in the wrist and palm by robustly suppressing the signals of fat, bone marrow, and especially vessels in volunteers and patients.

Long-Term Outcomes of Ultrasound-Guided Thread Carpal Tunnel Release and Its Clinical Effectiveness in Severe Carpal Tunnel Syndrome: A Retrospective Cohort Study

Ultrasound-guided thread carpal tunnel release (TCTR) was proposed as an effective and safe surgical technique with faster recovery and fewer complications. This study was conducted to confirm the long-term outcomes after TCTR and verify its clinical effectiveness in severe carpal tunnel syndrome (CTS) for more insights into TCTR procedure. A total of 168 TCTR procedures were performed in 152 individual patients by two physiatrists during 36-month period. In an assessment of 82 hands, surgical outcomes of 2 years after TCTR could be obtained, and the grade 6 CTS group of 21 hands, classified as extremely severe grade by Bland's classification, was compared with other severity groups (grade 1-5). The Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) was used to assess surgical outcomes. No adverse events occurred in all cases including the case of severe CTS and anatomical variants. TCTR showed significant improvement in BCTQ scale within 1-2 weeks, which continued up to 2 years with no recurrence (p < 0.01). Although slower and more progressive than the other severity group, there was also significant improvement relative to the BCTQ scale around 4 weeks after procedure in the grade 6 CTS group (p < 0.05). With the familiarity of ultrasound, ultrasound-guided TCTR is an effective and reliable surgical treatment for CTS in long-term outcomes and in severe CTS.

At-Risk Median Motor Branch to the Thenar Musculature Crossing Under the Flexor Carpi Radialis in the Forearm: A Case Report

CASE

A 77-year-old woman who sustained a distal radius and ulna fracture underwent open reduction internal fixation through a standard flexor carpi radialis (FCR) approach. On dissection, a proximal division of the median nerve was identified, with an aberrant motor branch crossing radial to ulnar deep to FCR and superficial to flexor pollicis longus.

CONCLUSION

Although many anatomic variants of the median nerve have been described, the current case demonstrates a particularly important median motor branch variant, imposing a substantial risk of iatrogenic injury during a standard FCR approach.

Carpal tunnel syndrome

Median neuropathy at the wrist, commonly referred to as carpal tunnel syndrome (CTS), is the most common entrapment neuropathy. It is caused by chronic compression of the median nerve at the wrist within the space-limited carpal tunnel. Risk factors that contribute to the etiology of compression include female gender, obesity, work-related factors, and underlying medical conditions, such as hypothyroidism, pregnancy, and amyloidosis. The diagnosis is made on clinical grounds, although these can be confounded by anatomical variations. Electrodiagnostic studies, which are specific and sensitive in diagnosing CTS, support the diagnosis; however, a subgroup may present with normal results. The advent of imaging techniques, including ultrasound and MRI, further assists the diagnostic process. The management of CTS is divided into the nonsurgical approaches that include hand therapy, splinting and corticosteroid injection, and surgical decompression of the carpal tunnel. Although several surgical techniques have been developed, no one method is more effective than the other. Each of these management approaches are effective at providing symptom relief and are utilized at different severities of the condition. There is, however, a lack of consensus on standardized diagnostic criteria, as well as when and to whom to refer patients for surgery.

Intraoperative Conversion From Endoscopic to Open Carpal Tunnel Release: A Systematic Review and Case Series

PURPOSE

The purpose of this study was to assess the incidence, outcomes, and complications associated with conversion from endoscopic carpal tunnel release (ECTR) to open carpal tunnel release (OCTR).

METHODS

A retrospective case review of all patients who underwent ECTR over 4 years by 2 fellowship-trained hand surgeons at a single academic center was performed. We recorded outcomes and the reason for conversion in patients who underwent conversion to an OCTR. Baseline demographics and surgical complications were compared between the 2 groups. A systematic review was performed to define the incidence and reasons for conversion from ECTR to OCTR. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we included clinical studies of ECTR from 2000 to 2021.

RESULTS

In the retrospective series, 9 of 892 (1.02%) ECTR cases underwent conversion to an OCTR at the time of the index procedure. One of 9 converted cases had transient neurapraxia involving the recurrent motor branch after surgery compared with 0 cases in the group that underwent ECTR without conversion. Improvements in the visual analog scale for pain and QuickDASH were noted at a mean of 46 weeks after surgery in the group that underwent conversion to OCTR. The systematic review identified an incidence of conversion of 0.62%. The most common reasons for conversion to OCTR in the case series and systematic review were poor visualization due to hypertrophic tenosynovium and aberrant nerve anatomy.

CONCLUSIONS

The overall incidence of intraoperative conversion from ECTR to OCTR during the index procedure was 1.02%, with the most common reasons for conversion being poor visualization due to hypertrophic tenosynovium and aberrant nerve anatomy. Patients who undergo conversion from ECTR to OCTR demonstrate improvements in pain and disability, similar to patients who undergo ECTR without conversion.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Role of high-resolution ultrasound and magnetic resonance neurography in the evaluation of peripheral nerves in the upper extremity

Upper extremity entrapment neuropathies are common conditions in which peripheral nerves are prone to injury at specific anatomical locations, particularly superficial regions or within fibro-osseous tunnels, resulting in pain and potential disability. Although neuropathy is primarily diagnosed clinically by physical examination and electrophysiology, imaging evaluation with ultrasound and magnetic resonance neurography are valuable complementary non-invasive and accurate tools for evaluation and can help define the site and cause of nerve dysfunction which ultimately leads to precise and timely treatment. Ultrasound, which has higher spatial resolution, can quickly and comfortably characterize the peripheral nerves in real time and can evaluate for denervation related muscle atrophy. Magnetic resonance imaging on the other hand provides excellent contrast resolution between the nerves and adjacent tissues, also between pathologic and normal segments of peripheral nerves. It can also assess the degree of muscle denervation and atrophy. As a prerequisite for nerve imaging, radiologists and sonographers should have a thorough knowledge of anatomy of the peripheral nerves and their superficial and deep branches, including variant anatomy, and the motor and sensory territories innervated by each nerve. The purpose of this illustrative article is to review the common neuropathy and nerve entrapment syndromes in the upper extremities focusing on ultrasound and magnetic resonance neurography imaging.

Anatomical considerations of US-guided carpal tunnel release in daily clinical practice

Carpal tunnel syndrome is the most frequent compression neuropathy with an incidence of one to three subjects per thousand. As specific anatomical variations might lead to unintended damage during surgical interventions, we present a review to elucidate the anatomical variability of the carpal tunnel region with important considerations for daily clinical practice: several variants of the median nerve branches in and around the transverse carpal ligament are typical and must - similarly to the variant courses of the median artery, which may be found eccentric ulnar to the median nerve - be taken into account in any interventional therapy at the carpal tunnel. Unintended interference in these structures might lead to heavy arterial bleeding and, in consequence, even underperfusion of segments of the median nerve or, if neural structures such as variant nerve branches are impaired or even cut, severe pain-syndromes with a profound impact on the quality of life. This knowledge is thus crucial for outcome- and safety-optimization of different surgical procedures at the volar aspect of the wrist and surgical therapy of the carpal tunnel syndrome e.g., US-guided carpal tunnel release, as injury might result in dysfunction and/or pain on wrist motion or direct impact in the region concerned. For most variations, anatomical and surgical descriptions vary, as official classifications are still lacking.

Pilot Cadaveric Study of Anatomical Variations of the Median Nerve at the Wrist in the Lithuanian Population

INTRODUCTION

 Carpal tunnel syndrome (CTS) is known as one of the most common neurological disorders in the human body. Nowadays, the prevalence in the general population ranges between 1% and 5%. Due to its high prevalence and increasing incidence of carpal tunnel surgery, the anatomical variations of the median nerve at the wrist are important to know to avoid iatrogenic injury of the nerve.

PURPOSE

The objective of this study was to evaluate the anatomical variation of the median nerve at the level of the wrist in the Lithuanian population with a focus on its thenar motor branch based on the classifications of Lanz.

MATERIAL AND METHODS

A cadaveric study was performed, and 30 wrists of 15 adult Lithuanian cadavers ranging from 70 to 89 years of age were dissected and examined. Eight female and seven male cadavers were included in the study. Any anatomical finding was documented, and the results were compared with the classification of Lanz as well as with the data found in the literature.

RESULTS

All hands showed different patterns in comparison to the standard anatomical variation Lanz type 0. The most common result was dedicated to Lanz group 4A. Nineteen out of 30 hands (63%, p<0.01) had an accessory branch proximal to the carpal tunnel, while one of these hands showed a third thenar motor branch. Five hands (16%) were dedicated to Lanz group 2 with an accessory branch distal to the carpal tunnel. One hand (3%) showed a variation close to Lanz group 2, but in this case, the thenar motor branch had its origin under the flexor retinaculum instead of proximal to it. Two hands each (6%) were classified by Lanz groups 1B and 3A. Additionally, one variation showed a pattern of a combination of Lanz types 3A and 3B. The bifid median nerve had a connecting branch in between which started distal to the flexor retinaculum. Two anatomical variations (6%) were not described by the classification of Lanz.

Imaging of Anatomical Variants Around the Wrist and Hand

Wrist and hand anatomy may present several clinically relevant variants that involve bones, muscles, tendons, and nerves. Thorough knowledge of these abnormalities and their appearance in imaging studies is useful for proper management. In particular, it is necessary to differentiate the incidental findings that do not represent a trigger for a specific syndrome from those anomalies causing symptoms and functional impairment. This review reports the most common anatomical variants encountered in clinical practice and briefly discusses their embryogenesis, related clinical syndrome if present, and their appearance using different imaging techniques. The information each diagnostic study (ultrasonography, radiographs, computed tomography, and magnetic resonance imaging) may provide is described for each condition.

Minimally Invasive Carpal Tunnel Release Using a Hook Knife through a Small Transverse Carpal Incision: Technique and Outcome

Background

Compared to the classic open technique, limited exposure techniques have the advantages of less scar pain, more grip and pinch strength, and earlier return to daily life. We evaluated the effectiveness and safety of our novel method of minimally invasive carpal tunnel release using a hook knife through a small transverse carpal incision.

Methods

This study included 111 carpal tunnel decompressions in 78 patients who underwent carpal tunnel release from January 2017 to December 2018. We performed carpal tunnel release using a hook knife through a small transverse incision just proximal to the wrist crease under local infiltration of lidocaine with tourniquet inflation in the upper arm. All patients were tolerable during the procedure and discharged following the procedure on the same day.

Results

At an average of 29.4 months of follow-up (range, 12-51 months), all but one patient (99%) revealed complete or near complete symptomatic recovery. The average of the symptom severity score on the Boston questionnaire was 1.31 ± 0.30 and the average of the functional status score was 1.19 ± 0.26. The final mean Quick Disabilities of the Arm, Shoulder, and Hand questionnaire (QuickDASH) score was 8.66 (range, 2-39). There was no superficial palmar arch injury or nerve injury of the palmar cutaneous branch, recurrent motor branch, or median nerve itself as a complication of the procedure. No patient showed any wound infection or wound dehiscence.

Conclusions

Our carpal tunnel release using a hook knife through a small transverse carpal incision performed by an experienced surgeon is a safe and reliable method that is expected to have the benefits of simplicity and minimal invasiveness.

Accessory Hand Muscles Over the Transverse Carpal Ligament: An Obstacle in Carpal Tunnel Surgery

BACKGROUND

Carpal tunnel syndrome (CTS) is an entrapment neuropathy caused by compression of the median nerve throughout the carpal tunnel. It is the most common entrapment neuropathy, with an estimated prevalence of 4%-7%. Surgical management is more effective in moderate to severe and severe CTS. CTS recurs in approximately 20% of patients, and up to 12% of these patients require reoperation. Knowledge of normal anatomy and variations would improve the success rate of the index surgery. Atypical causes of CTS were reported, including ganglion cysts, synovial hypertrophy, lipomas, bone fracture, bone fragments, tumor of soft tissues or bones, neurofibromas, neuromas, vascular malformations, and accessory muscles. Accessory muscles are commonly detected in upper limbs. However, their concomitant presentation with CTS has rarely been reported. We aimed to present different accessory muscles diagnosed during CTS surgery through a systematic review of the literature with our exemplary case.

METHODS

A systematic review/meta-analysis was performed concomitant with a case presentation.

RESULTS

Accessory muscles associated with CTS were as follows: palmaris longus, 28.6%; lumbrical muscles, 19.3%; palmaris profundus, 17.8%; flexor digitorum superficialis, 16.1%; transverse carpal muscle, 5%; flexor digitorum indicis, 4.2%; flexor superficialis indicis, 4.2%; flexor sublimis, 0.8%; accessory superficialis longus, 0.8%; flexor pollicis longus, 0.8%; abductor digiti minimi, 0.8%; abductor digiti quinti, 0.8%; and flexor digitorum superficialis brevis, 0.8%. Accessory muscles were mostly noticed during CTS surgery (88.2%).

CONCLUSIONS

Knowledge of possible variations within the carpal tunnel would improve the surgeon's capability during CTS surgery.

The position of the median nerve in relation to the palmaris longus tendon at the wrist: a study of 784 MR images

Iatrogenic injury of the median nerve has been reported after endoscopic carpal tunnel release and corticoid injection. In 784 MR images of the wrist, the position of the median nerve in relation to the palmaris longus tendon was analysed. The ulnar edge of the median nerve was found medial to the palmaris longus tendon in 14% and 36% of patients at the proximal wrist crease and entrance of the carpal tunnel, respectively, compared with 23% and 40% of patients with carpal tunnel syndrome (88 patients). The position of the median nerve in relation to the palmaris longus tendon varies widely. It is suggested that the palmaris longus tendon may not be considered a safe landmark to locate the position of the median nerve and care should be taken when introducing an endoscopic instrument or during steroid injection for carpal tunnel syndrome.Level of evidence: IV.

[Trifid median nerve. A rare anatomical variant in sonographic evaluation of carpal tunnel]

The ultrasound study for the diagnosis of carpal tunnel syndrome can reveal different anatomical variants. A rare variant is the presence of a trifid median nerve. The visualization of this anatomical variant may be of importance in the surgical planning of carpal tunnel syndrome. Fifty-two-year-old male, with a clinic compatible with bilateral carpal tunnel syndrome. In the ultrasound examination, a bifid median nerve appears as a finding in the right wrist and a trifid median nerve in the left wrist as anatomical variants. It is important to distinguish a trifid median nerve from a persistent median artery at the level of the carpal tunnel, much more frequent than the first. For this, the ultrasound visualization of the study area using the Doppler function is essential.

Repair of severed recurrent thenar branch of median nerve after open carpal tunnel release

An anatomical understanding of median nerve variation is essential for successful decompression of carpal tunnel syndrome (CTS). Although iatrogenic injury of the thenar branch after carpal tunnel release (CTR) has not been reported in many cases, it can cause serious damage to the patient. In case of rapidly progressing thenar atrophy after CTS surgery, thenar branch of median nerve injury should be suspected. Nerve conduction examination and ultrasound before surgery can be a useful tool for diagnosis.

Prevalência de variações anatômicas encontradas em pacientes com síndrome do túnel do carpo submetidos a liberação cirúrgica por via aberta clássica

Objective  To evaluate the prevalence of anatomical variations encountered in patients with carpal tunnel syndrome who underwent carpal tunnel classical open release.

Methods  A total of 115 patients with a high probability of clinical diagnosis for carpal tunnel syndrome and indication for surgical treatment were included. These patients underwent electroneuromyography and ultrasound for diagnostic confirmation. They underwent surgical treatment by carpal tunnel classical open release, in which a complete inventory of the surgical wound was performed in the search and visualization of anatomical variations intra- and extra-carpal tunnel.

Results  The total prevalence of anatomical variations intra- and extra-carpal tunnel found in this study was 63.5% (95% confidence interval [CI]: 54.5–72.4). The prevalence of the carpal transverse muscle was 57.4% (95% CI: 47.8–66.6%), of the bifid median nerve associated with the persistent median artery was 1.7% (95% CI: 0.0–4.2%), and the median bifid nerve associated with the persistent median artery and the transverse carpal muscle was 1.7% (95% CI: 0.0–4.2%).

Conclusion  The most prevalent extra-carpal tunnel anatomical variation was carpal transverse muscle. The most prevalent intra-carpal tunnel anatomical variation was median bifid nerve associated with the persistent median artery. The surgical finding of an extra-carpal tunnel anatomical variation, such as the transverse carpal muscle, may indicate the presence of other associated carpal intra tunnel anatomical variations, such as the bifid median nerve, persistent median artery, and anatomical variations of the recurrent median nerve branch.

[Differential therapeutic Approaches in Treatment of Carpal Tunnel Syndrome]

Carpal tunnel syndrome (CTS) is one of the most common compression neuropathies. The therapeutic concept should be tailored to each patient individually, with initial non-surgical treatment being the standard of care for early CTS. Primary surgical intervention should be considered in more advanced diseases stages, in case of concomitant pathologies (including space-occupying lesions, complex regional pain syndrome or diabetic neuropathy), if non-surgical strategies have failed or in pregnancy-related CTS. This work aims to discuss common surgical approaches, their clinical application as well as benefits and disadvantages in a pragmatic style. Further, we highlight surgical strategies to address recurrent CTS following failed primary surgery. In view of the recently updated S3 guidelines "Diagnosis and Therapy of Carpal Tunnel Syndrome", this topic is timely and relevant for hand and nerve surgeons.

Ultrasonographic evaluation of the median nerve: normal and variant anatomy and appearance

The median nerve is a mixed sensory and motor nerve that innervates part of the flexor muscles in the anterior compartment of the forearm and muscles in the lateral part of the hand; palmar cutaneous and digital cutaneous nerves branch from the median nerve, which provides sensory innervation to the skin on the radial side of the palm. Also, the median nerve is an object of interest because neuropathy of the median nerve at the level of the carpal tunnel is the most common entrapment neuropathy which increases dramatically in patients with diabetes. Neuromuscular ultrasound provides extensive diagnostic information and has proved itself as a useful complementary test to electrodiagnostic examinations in cases involving median nerve neuropathy. It often happens that the cause of nerve entrapment and neuropathy are variants of several anatomical structures along the course of the median nerve. It is important to be aware and report such anatomical variations of the median nerve in order to avoid damaging the nerve during surgical treatment. Despite the frequently documented abnormalities in the pathway of the brachial plexus and the median nerve, the anatomical variations are unusual to see and are rarely reported. Moreover, there are variations that do not fit under any of the classifications described in the literature.

Suprafascial plane endoscopy versus open carpal tunnel release for idiopathic carpal tunnel syndrome: Use of the Accordion Severity Grading System

This study aimed to assess the safety and effectiveness of modified endoscopic technique with a single portal from an external carpal tunnel approach for surgical operations in a suprafascial plane superficial to the transverse carpal ligament. Reversible nerve injury risk is threefold greater with a conventional endoscopic method than with open carpal tunnel release (OCTR), and this suprafascial plane endoscopic release (SPER) should circumvent the problem of hardware in the carpal tunnel encountered with the conventional endoscopic method and liable to cause iatrogenic damage to the median nerve. However, the surgical consequences of the new technique have not been studied. To fill this gap, a retrospective therapeutic study was conducted to compare negative outcomes versus open surgery. The Accordion Severity Grading System was used to grade complications from 0 to 3 according to necessity of treatment. Sequela and failure rates were also compared between the SPER and OCTR groups. Eighty-eight cases in 72 patients with idiopathic carpal tunnel syndrome (ICTS) met the inclusion criteria. SPER was performed in 28 hands in 27 patients, and OCTR in 60 hands in 49 patients. The results showed no significant difference in complication, sequela, or failure rates between groups (p > 0.05). Suprafascial plane endoscopic release, has certain advantages over the open method and was validated as a safe and effective method of treating ICTS.

Demographical, Anatomical, Disease-Related, and Occupational Risk Factors for Carpal Tunnel Syndrome

Background: Carpal tunnel syndrome (CTS) is the most common focal mononeuropathy. It causes characteristic symptoms, including numbness and paresthesia in hand due to median nerve compression at the wrist. Objectives: We aimed to investigate CTS prevalence and personal, psychosocial, biomedical, and occupational factors related to it comprehensively, according to scattered publications, without the simultaneous evaluation of all CTS risk factors. Methods: A total of 345 patients referred to a hand clinic with a complaint of paresthesia in upper extremities and suspected CTS. The patients underwent neurological assessment and electrodiagnostic (EDX) tests to confirm the diagnosis. The demographic information, past medical history, past trauma history, and occupational history of all the patients were recorded and finally analyzed with SPSS software. Results: Of the patients, 213 (67.1%) met the criteria for CTS, of whom 160 (75%) were female. Females were significantly more affected by CTS than males (P < 0.05). The mean age was higher in the CTS patients (53.80 ± 11.57 years) than in non-patients (42.39 ± 12.31 years, P < 0.001). No statistical relevance was found between CTS prevalence with occupational history, underlying medical conditions, positive Tinel’s and Phalen's tests, and muscle atrophy. Conclusions: We recognized age and gender as main determinants in developing CTS. We also found that older age was related to higher CTS intensity.

[Babysitter nerve transfer from the thenar branch to the deep terminal branch of the ulnar nerve : An option to preserve the intrinsic hand muscles in proximal lesions of the ulnar nerve]

Operationsziel

Ziel dieser Operation ist eine frühzeitige Innervation der intrinsischen Handmuskulatur durch Fasern des N. medianus, um einer irreversiblen Atrophie des Muskelgewebes vorzubeugen. Der Nerventransfer erfolgt mittels Babysitter-Interponat, welches jeweils End-zu-Seit an Spender- und Empfängernerv koaptiert wird. Der Eingriff wird kombiniert mit einer proximalen Rekonstruktion des N. ulnaris.

Indikationen

Hochgradige Läsionen des N. ulnaris ohne spontane Regeneration, insbesondere bei proximaler Läsionshöhe und/oder später Patientenvorstellung.

Kontraindikationen

Irreversible Denervation der intrinsischen Muskulatur; Schwäche oder Ausfall des R. thenaris.

Operationstechnik

Der Zugang erfolgt über dem beugeseitigen Handgelenk durch eine longitudinale Inzision. Der R. profundus des N. ulnaris sowie der R. thenaris des N. medianus werden nach Spalten des Retinaculum flexorum dargestellt. Es erfolgt eine Verbindung der beiden Nerven über ein autologes Interponat, welches jeweils in End-zu-Seit-Manier über ein epineurales Fenster an den Spender- (R. thenaris) und den Empfängernerv (R. profundus) koaptiert wird. Dies ermöglicht die zeitgerechte Regeneration einiger motorischer Medianusaxone in die intrinsische Muskulatur, um einer irreversiblen Degeneration vorzubeugen. Aufgrund der End-zu-Seit-Nervennaht wird der Schaden des Spendernervs auf ein Minimum reduziert. Durch die gleichzeitig durchgeführte Rekonstruktion des N. ulnaris auf Höhe der Läsion wird im späteren Verlauf auch eine autochthone Reinnervation der intrinsischen Muskulatur ermöglicht.

Weiterbehandlung

Postoperativ werden Laschen eingebracht und ein steriler Handverband angelegt. Erster Verbandswechsel und Zug der Laschen am ersten postoperativen Tag, Nahtentfernung in der Regel nach 2 Wochen. Bereits nach 1 Woche kann die ergotherapeutische Beübung zum Erhalt der Gelenkbeweglichkeit erfolgen. Nach den ersten Zeichen der motorischen und/oder sensiblen Reinnervation erfolgt eine zielgerichtete Physiotherapie zum Wiedererlernen der alltäglichen Handfunktion.

Ergebnisse

Diese Technik wurde bisher an 3 Patienten mit hochgradiger Läsion des N. ulnaris vorgestellt. Bei einer Follow-up-Zeit von 6 Jahren konnten alle Patienten Muskelkraft von ≥ M3 erlangen, mit allgemein gutem bis exzellentem Ergebnis anhand der modifizierten Bishop Rating Scale.

"Million dollar nerve" magnetic resonance neurography: first normal and pathological findings

OBJECTIVES

To evaluate prospectively the feasibility of magnetic resonance neurography (MRN) in identifying the anatomical characteristics of thenar muscular branch (TMB) of the median nerve, also known as the "million dollar nerve," in patients and controls.

METHODS

Thirteen patients affected by carpal tunnel syndrome (CTS) and four healthy controls had their hands scanned on a 3-T MR imaging scanner for TMB visualization. Median nerve anatomical variations were classified into four groups according to Poisel's classification system modified by Lanz. TMB signal intensity and diameter were assessed for the diagnosis of neuropathy.

RESULTS

TMB was successfully identified in all patients and subjects by using MRN. The most suitable pulse sequences to identify and measure nerve diameter were 3D DW-PSIF and T2-FS-TSE. The axial oblique and sagittal oblique planes are complementary in demonstrating its entire course. TMB had mostly an extraligamentous course with radial side origin (93.8%, each). All patients experienced increased T2 signal intensity (p < 0.001) and thickened nerves. Mean TMB diameters were 1.27 ± 0.21 mm (range, 1.02-1.74 mm) and 0.87 ± 0.16 mm (0.73-1.08 mm) (p = 0.008) in the patient and control groups, respectively.

CONCLUSION

MRN is a reliable imaging technique for identification and anatomical characterization of TMB in patients affected by CTS. This innovative imaging workup may therefore be included in the preoperative evaluation of patients scheduled for carpal tunnel release, especially in CTS with TMB involvement or even in isolated TMB neuropathy.

KEY POINTS

• Magnetic resonance neurography allows precise visualization of the thenar muscular branch of the median nerve. • Thenar muscular branch anatomical variations can be correctly identified. • Preoperative scanning can contribute to reducing the risk of iatrogenic injuries during carpal tunnel release, especially in carpal tunnel syndrome with thenar muscular branch involvement or even in isolated thenar muscular branch neuropathy.

Revision Peripheral Nerve Surgery of the Upper Extremity

Peripheral nerve injuries of the upper extremity can result from a wide array of etiologies, with the two most common being compression neuropathy and traumatic injuries. These types of injuries are common and can be psychologically, functionally, and financially devastating to the patient. A detailed preoperative evaluation is imperative for appropriate management. Traumatic injuries can typically be treated with local burial techniques, targeted muscle reinnervation, and regenerative peripheral nerve interfaces. Median nerve compression is frequently managed with complete release of the antebrachial fascia/transverse carpal ligament and/or use of flap coverage such as the hypothenar fat pad flap and local muscle flaps. Ulnar nerve compression is commonly managed via submuscular transposition, subcutaneous transposition, neurolysis, and nerve wrapping. In this review, we discuss the preoperative evaluation, surgical techniques, and advantages and disadvantages of each treatment modality for patients with compressive and traumatic upper extremity nerve injuries.

Electrodiagnostic, Sonographic, and Clinical Features of Carpal Tunnel Syndrome with Bifid Median Nerve

Purpose

A bifid median nerve (BMN) is not a rare variant. This study aimed to investigate the features of carpal tunnel syndrome (CTS) accompanied by BMN.

Patients and Methods

In this retrospective study, we defined a BMN group as CTS with BMN and a non-bifid median nerve (NMN) group as CTS without BMN. All hands were assigned to four severity grades according to the findings of electrodiagnosis (EDx): very mild, mild, moderate, and severe. The cross-sectional area (CSA) of the median nerve, palmar bowing of the flexor retinaculum, and persistent median artery (PMA) were assessed by ultrasonography. Numerical pain rating scale (NRS) and symptom duration were assessed as clinical variables.

Results

Sixty-four hands (57 patients) and 442 hands (341 patients) were enrolled in the BMN and the NMN groups, respectively. BMN was prevalent in 12.6% of all CTS hands. The distribution of EDx severity grade was milder in the BMN group than in the NMN group (P<0.001). The CSA of the BMN group was 16.2±4.1 mm², slightly larger than 15.1±4.2 mm² in the NMN group (P=0.056). The BMN group showed higher NRS than the NMN group (5.5±1.5 and 4.4±1.7, respectively; P<0.001). In the subgroup analysis, NRS was significantly higher in the BMN group than in the NMN group at all EDx severity grades. In the BMN group, the PMA group showed greater EDx severity (P=0.037) and higher NRS (6.0 and 5.0, respectively; P=0.012) than the non-PMA group. The radial side branch's CSA was larger than that of the ulnar side branch (10.0 mm² and 6.0 mm², respectively; P<0.001).

Conclusion

CTS with BMN presented more severe symptoms and relatively milder EDx severity. When assessing the severity of CTS with BMN, the clinical symptoms should primarily be considered, as well as we should complementarily evaluate the EDx and ultrasonography.

Novel steroid infiltration technique of the carpal tunnel

This report describes a novel technique of steroid infiltration of the wrist to treat symptomatic carpal tunnel syndrome. Our approach potentially reduces direct trauma to the median nerve when compared with current conventional techniques. The use of a cannula allows infiltration directly into the carpal tunnel and advancement of the blunt tip minimises the risk of sharp trauma to the median nerve and adjacent tendons. This avoids the unpleasant, shooting pain frequently experienced by patients using traditional needle infiltration. We anticipate this would be of particular benefit in reducing pain associated with the procedure.

Carpal tunnel syndrome caused by the entrapment of a bifid Lanz IIIA Type anatomical variant of median nerve: A case report and systematic literature review

Background:

Carpal tunnel syndrome (CTS) is the most common entrapment peripheral neuropathy. Median nerve may present several anatomical variations such as a high division or bifid median nerve (BMN). A thorough knowledge of the normal anatomy and variations of the median nerve at the wrist are fundamental to reduce complications during carpal tunnel release.

Case Description:

A 63-year-old man with CTS underwent preoperative ultrasound that showed the entrapment of the median nerve and disclosed a BMN Lanz IIIA Type anatomical variation at the carpal tunnel. During the surgery, the anatomical variant of a BMN at the wrist has been visualized. Both nervous rami entirely occupied the carpal canal and this may have predisposed to the development of the entrapment syndrome. Nor persistent median artery, or other associated abnormalities, have been identified. At the 6 months follow-up control, the patient referred a good surgical recovery with complete resolution of the preoperative symptoms of the median nerve entrapment.

Conclusion:

A rare case of Lanz IIIA BMN Type at the wrist has been encountered in a patient with a CTS and a systematic review and practical considerations have been presented with the aim of raising awareness to the neurosurgical community of a such rare variant that could be encountered during carpal tunnel release procedures. CTS may be caused by the entrapment of a BMN Lanz IIIA Type anatomical variant of median nerve. Preoperative US would help to identify such patients to reduce risk of iatrogenic injuries.

A mini-incision carpal tunnel release technique to prevent pillar pain: A technical note

Pillar pain represents one of the most common complications of classic open carpal tunnel release (CTR). This complication causes a sense of discomfort worse than the compression syndrome itself. We, herein, introduce a new treatment method for CTR through a mini-incision, which allows subcutaneously cutting the transverse carpal ligament (TCL) and releasing the median nerve without neurovascular complications. This mini-incision approach can allow the direct visualization and preservation of the thenar motor branch in those rare cases where it has an aberrant origin. For the past 10 years, we have consecutively performed this technique in the surgical treatment of 318 patients with the diagnosis of primary CTS, without developing any neurovascular and tendon injuries as well as pillar pain.

[Selective nerve transfers for thenar branch reconstruction]

OPERATIVE

Reconstruction of thump opposition with selective nerve transfer of the motor branch of the abductor digiti minimi muscle (ADM) to the thenar motor branch.

INDICATIONS

Injury of the median nerve or thenar motor branch and resulting loss of thumb opposition.

CONTRAINDICATIONS

Combined median and ulnar nerve injuries or brachial plexus lesions of C8-Th1, or a time interval >12 months since denervation of the thenar branch.

SURGICAL TECHNIQUE

The ADM motor branch is microsurgically dissected and transferred to the thenar branch.

POSTOPERATIVE MANAGEMENT

After successful reinnervation, regular follow-ups and intensive physiotherapy are important for operative outcome.

RESULTS

Reconstruction of the opposition of the thumb results in improved range of motion as well as a gain of grip and pinch force.

High Division of the Median Nerve with Unusually High Origin of the 3rd Space Common Digital Nerve

BACKGROUND

Median nerve (MN) variation in the carpal tunnel has been well documented by Lanz. Encountering rarely documented variants, that do not fit into existing classifications, increases the risk of iatrogenic injury.

METHODS

The random occurrence of two unclassifiable anatomical variants of the MN in the carpal tunnel gives motivation to search the literature for similar and identical cases.

CASE REPORTS

This article presents two cases of very rare anatomical variants of high division of the MN. First case is a pure high branching of the 3rd space common digital nerve (CDN). The second case is a high division of the MN to a thicker lateral component and a thinner medial component. The lateral component of the MN gives off the palmar cutaneous branch (PCB), the thenar motor branch (TMB), the 1^st and 2^nd space CDN's and contributes medially with a branch to the 3^rd space CDN. The medial component of the MN bifurcates distally into a medial and lateral branch. The lateral branch from the medial component of the MN distally unites with the medial branch of the lateral component of the MN to form the 3^rd space CDN. The medial branch from the medial component of the MN has a major contribution to the 4^th space CDN from the ulnar nerve. In both cases, the medial component of the MN has a transmuscular course through the flexor digitorum superficialis (FDS) muscle.

DISCUSSION

Finding similar case reports from worldwide suggests the need to improve current classification of the MN variants in the carpal tunnel.

CONCLUSIONS

One cannot rely entirely on the existing anatomical classifications of the MN in the carpal tunnel. There is an underappreciated risk of iatrogenic injury, especially in endoscopic carpal tunnel release, and a chance of missing out on repair of important anatomical structures in trauma cases. There is a possibility of augmenting group 3 of Lanz's classification by adding subgroup "3D High division of the MN with the medial component having a transmuscular course through the FDS muscle", stating the different distal branching patterns.

A Preligamentous Variant of the Thenar Motor Branch of the Median Nerve

We report a rare variant of the thenar motor branch (TMB) of the median nerve. A preligamentous TMB was discovered during revision carpal tunnel release in a 49-year-old man. The prevalence and characteristics of TMB variations are discussed. The literature describing iatrogenic injury to the TMB variants, surgical treatment, and preoperative screening tools is reviewed. Recognition of anatomic variants of the TMB is essential considering notable consequences of iatrogenic injury.

Endoscopic Carpal Tunnel Release: Indications, Technique, and Outcomes

Carpal tunnel is the most common peripheral compressive neuropathy. Nonoperative management may provide temporary alleviation of symptoms, but in most cases surgical decompression is warranted. There are a multitude of approaches ranging from open release under general anesthesia to wide awake in-office endoscopic carpal tunnel release. The present article describes the technical considerations for the single incision, antegrade approach to endoscopic carpal tunnel release using the SEGWay system and technique.

Sonography before and after carpal tunnel release: video article

Carpal tunnel release for compression of the median nerve at the wrist is a common procedure, often resulting in good clinical outcomes. There are, however, many anatomical variations in and around the carpal tunnel and it is important to be aware of these during carpal tunnel release. After surgery, recurrent carpal tunnel syndrome is uncommon, but difficult to diagnose and treat. Ultrasonography is often necessary for the evaluation of the anatomical variations before carpal tunnel release and to evaluate the most common complications after carpal tunnel release.

The superficial anatomical landmarks are not reliable for predicting the recurrent branch of the median nerve

PURPOSE

The variability of the recurrent branch (RB) of the median nerve lends itself to an increased risk of injury when performing the minimally invasive approach for carpal tunnel release without its direct visualization. This risk is less so when it is released via the more invasive open approach as the RB can be easily identified, but the drawback is that of longer postoperative patient recovery time. Therefore, performing these releases via the less invasive approach should be more favorable for patients providing it could be done safely. Hence with there being a positive link between the hypertrophy of the thenar musculature and the course of RB according to previous studies.

METHODS

We dissected 28 hands of 14 donated bodies fixed using Thiel's method to try to demonstrate these findings of the associations among the RB, palmar creases and other superficial anatomical landmarks. Fisher's exact test was conducted to verify the relationship between those structures statistically.

RESULTS

Statistically significant links were found between the type of the RB and the type of the palmar creases (p value = 0.0094) and between the RB type and the palmaris longus muscle presence (p value = 0.028).

CONCLUSION

It was inferred that palmar creases and other superficial anatomical landmarks listed in the text could not be used to predict the variability of the RB and the choice of mini-invasive approach should not be based on their course.

Incidental bifid median nerve with a wandering ulnar division separated by the third flexor digitorum superficialis muscle: importance of ultrasound evaluation

Ultrasound evaluation of the median nerve is commonly performed in patients with suspected carpal tunnel syndrome. Radiologists should be familiar with variant anatomy of the median nerve to assist clinicians in the management of these patients, particularly when surgery is being considered. A 63-year-old female was being evaluated for a ganglion cyst and was incidentally found to have a bifid median nerve with wandering ulnar division which coursed superficial to the third digit flexor digitorum superficialis (FDS) muscle belly. The patient did not have any symptoms of carpal tunnel syndrome so surgery has not been performed; however this case highlights the importance of ultrasound evaluation to avoid potential perioperative complications.

Comparison of two approaches for carpal tunnel release: Extended versus mini-open technique

Objectives

This study aims to describe a retrospective study using prospectively gathered data to compare mini-open and extended open release techniques for moderate to severe carpal tunnel syndrome (CTS).

Patients and methods

The data of 198 consecutive patients (139 males, 59 females; mean age 57.0±4.5 years; range, 44 to 75 years) treated for CPS were used. For matching, age, gender and severity of the compression, the Greathouse Ernst Halle Schaffer neurophysiological classification system was used. After matching, 63 observations in each group (group 1: mini-open and group 2: extended open) were used for analysis. A Jamar hydraulic hand dynamometer was used to measure pre- and postoperative third month grip strengths. The key pinch test was performed also at third month. Patients completed the Boston Carpal Tunnel Questionnaire at the last follow-up.

Results

Symptom severity and functional status were improved up to half fold in both groups at final follow-up; however, there was no statistically significant clinical difference between the groups (p>0.05). There were totally six patients with paresthesia symptoms (three in each group; 4.7%), which improved in three months. Eight patients (6.3%, one in group 1 and seven in group 2, p=0.032) had dysesthesia and pillar pain.

Conclusion

Mini-open and extended open carpal tunnel release have similar clinical outcomes without any major complications.

Ultrasonography of the Peripheral Nerves of the Forearm, Wrist and Hand: Definition of Landmarks, Anatomical Correlation and Clinical Implications

BACKGROUND

 Peripheral nerve pathologies of the upper extremity are increasingly assessed by high-resolution ultrasonography (HRUS), yet rapid identification of nerve segments can be difficult due to small nerve diameters and complex regional anatomy. We propose a landmark-based approach to speed up and facilitate evaluation and intervention in this region.

METHOD

 Relevant landmarks and section planes for eleven nerve segments of the forearm, wrist and hand were defined by ultrasonography in cadaver arms before cryosection and topographical neurovascular preparation. Information on all nerve segments and a pictorial guide including anatomical cross-sections, topographical preparations and HRUS images are provided. The identification rates of these nerve segments were then assessed in 20 healthy volunteers.

RESULTS AND CONCLUSION

 Sonographic landmarks and guidelines for the rapid identification and assessment of nerves of the forearm, wrist and hand are presented in pictorial and tabular form, including discussion of normal variants. Utilizing this overview should facilitate training, diagnostic examinations and intervention for nerves of the upper extremity.

KEY POINTS

  · High-resolution ultrasound enables assessment of peripheral nerves of the forearm, wrist and hand.. · A landmark-based approach can facilitate and speed up nerve evaluation in these regions.. · High detection rates could be reproduced using the proposed landmark-based approach..

CITATION FORMAT

· Gruber L, Loizides A, Peer S et al. Ultrasonography of the Peripheral Nerves of the Forearm, Wrist and Hand: Definition of Landmarks, Anatomical Correlation and Clinical Implications. Fortschr Röntgenstr 2020; 192: 1060 - 1072.

Clinical Results of Ultrasound-Guided Carpal Tunnel Release Performed by a Primary Care Sports Medicine Physician

OBJECTIVES

The purpose of this study was to determine the safety and efficacy of ultrasound-guided carpal tunnel release (USCTR) in a consecutive group of patients treated by a single primary care sports medicine physician.

METHODS

The study group consisted of 35 USCTRs performed on 22 consecutive patients for whom clinical outcomes were available before USCTR and at 1 to 2 weeks, 1 month, and 3 months after USCTR. All procedures were performed by the same operator using a single USCTR technique. Outcomes included complications, Quick Disabilities of the Arm, Shoulder, and Hand scores, Boston Carpal Tunnel Questionnaire symptom severity and functional status scores, and a 5-point global satisfaction score.

RESULTS

The 22 patients included 13 female and 9 male patients (ages 31-82 years). Eleven patients (22 wrists) had bilateral simultaneous USCTRs; 2 patients (4 wrists) had staged bilateral USCTRs; and 9 patients had unilateral USCTRs. No complications occurred in any patient. Statistically and clinically significant reductions in Quick Disabilities of the Arm, Shoulder, and Hand scores and Boston Carpal Tunnel Questionnaire symptom severity and functional status scores occurred by 1 to 2 weeks after USCTR (mean 1- to 2-week changes, -29.23, -1.74, and -1.18, respectively), and further improvements occurred during the 3-month follow-up period (mean 3-month changes, -51.11, -2.29, and -1.91; P < .0001 for all values versus before USCTR). Mean global satisfaction scores at 1 to 2 weeks and 3 months were 4.63 and 4.66.

CONCLUSIONS

Ultrasound-guided CTR is a safe and effective procedure that can be performed by an experienced primary care sports medicine physician and typically results in significant improvements within the first 2 weeks after the procedure. Furthermore, bilateral simultaneous USCTRs are feasible and may provide significant advantages for patients who are candidates for bilateral CTRs.

Median Nerve Variation: A Complete Spin before Terminal Branching

Median nerve anatomy is of great interest to clinicians and scientists given the importance of this nerve and its association with diseases. A rare anatomical variant of the median nerve in the distal forearm and wrist was discovered during a cadaveric dissection. The median nerve was deep to the flexor digitorum superficialis (FDS) in the carpal tunnel. It underwent a 360-degree spin before emerging at the lateral edge of FDS. The recurrent motor branch moved from medial to lateral on the deep surface of the median nerve, as it approached the distal carpal tunnel. This variant doesn't fall into any of Lanz's four groups of median nerve anomalies. We propose a fifth group that involves variations in the course of the median nerve. This report underscores the importance of recognizing variants of the median nerve anatomy in the forearm and wrist during surgical interventions, such as for carpal tunnel syndrome.

Report of a Transligamentous Ulnar Nerve Sensory Branch

Background: Several anatomical variations of the median nerve recurrent motor branch have been described. No previous reports have described the anatomical variation of the ulnar nerve with respect to transverse carpal ligament. In this article, we present a patient with symptomatic compression of the ulnar nerve found to occur outside the Guyon canal due to a transligamentous course through the distal transverse carpal ligament. Methods: A 59-year-old, right-hand-dominant male patient presented with right hand pain, subjective weakness, and numbness in both the ulnar and the median nerve distributions. Electromyography revealed moderate demyelinating sensorimotor median neuropathy at the wrist and distal ulnar sensory neuropathy. At the time of planned carpal tunnel and Guyon canal release, a transligamentous ulnar nerve sensory common branch to the fourth webspace was encountered and safely released. Results: There were no surgical complications. The patient's symptoms of numbness in the median and ulnar nerve distribution clinically improved at his first postoperative visit. Conclusions: We have identified a case of transligamentous ulnar nerve sensory branch encountered during carpal tunnel release. To our knowledge, this has not been previously reported. While the incidence of this variant is unknown, hand surgeons should be aware of this anatomical variant as its location puts it at risk of iatrogenic injury during open and endoscopic carpal tunnel release.

Evaluation and Management of Unsuccessful Carpal Tunnel Release

Carpal tunnel release (CTR) is a routine and effective surgical treatment for carpal tunnel syndrome. Dissatisfied patients after CTR are uncommon but present diagnostic and therapeutic challenges. This article discusses the most common reasons for unsuccessful CTR, the appropriate ensuing workup, and current evidence regarding revision surgery. The authors' preferred treatment algorithm for the surgical management of the unsuccessful CTR is presented.

Anatomic Landmarks to Locate the Median Nerve for Safe Wrist Block or Carpal Tunnel Steroid Injection

Introduction: Carpal tunnel syndrome is the most common entrapment neuropathy involving the upper extremity. As such, various nonoperative techniques have been developed to aid in management of mild to moderate disease, including local steroid injection. However, definitive guidelines for needle/injection location have not been defined, especially in relation to diminishment of iatrogenic injury to the median nerve. Methods: A cadaveric study was designed to determine the average width of the median nerve, as well as its location specifically in relation to the palmaris longus (if present), the flexor carpi radialis, and the midpoint of the wrist. All measurements were obtained at the radial tip of the interstyloid line. Results: Data demonstrated that the average width of the median nerve was 7.85 mm and that it lies ulnar in location to the palmaris longus (3 mm), as well as the midpoint of the wrist at the radial tip of the interstyloid line (0.43 mm). Furthermore, the distance between the median nerve and the flexor carpi radialis was measured to be 9.57 mm. Outcomes: Therefore, injection location should be radial with respect to the palmaris longus and the midline of the wrist. It can be just ulnar to the flexor carpi radialis tendon or between 8 and 10 mm radial to the midpoint of the wrist in order to prevent median nerve injection and direct trauma to the nerve.

Palmar Digital Neuropathy With Anatomical Variation of Median Nerve: Usefulness of Orthodromic Technique: A Case Report

Anatomic variation of palmar digital nerve pathways were reported in several cases. Selective exploration of palmar digital nerves with a nerve conduction study has been challenging, because of technical issues. We report a patient who received bilateral carpal tunnel release operation, complaining of a tingling sensation, and hypoesthesia on the middle and ring fingers. An electrodiagnostic study revealed a sensory neuropathy of palmar digital nerve of the left median nerve, supplying the ulnar side of the middle finger, and radial side of the ring finger. She underwent re-operation of open left carpal tunnel release, and a branching site of common digital nerves of the median nerve was identified not at the palm, but at a far proximal site around the distal wrist crease. Usefulness of an orthodromic sensory conduction study was clarified to eliminate volume conducted response or co-activation of nearby nerves in the patient with selective involvement of palmar digital nerve.