Normal Palmar Anatomy and Variations That Impact Median Nerve Decompression

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.

Identifying anatomic landmarks and median nerve characteristics for the analysis of persistent carpal tunnel syndrome using magnetic resonance imaging (MRI)

OBJECTIVE

Carpal tunnel syndrome (CTS) is the most common nerve entrapment neuropathy in the USA. In this study, we define anatomical landmarks to assess symptomatic and asymptomatic cohorts with persistent CTS using MRI imaging.

MATERIALS AND METHODS

Distal vs proximal incomplete release was determined using the distal most aspect of the hook of hamate and the distal wrist crease. An incomplete release showed the transverse carpal ligament (TCL) intact at either boundary. Twenty-one patients with persistent CTS were analyzed for incomplete release, median nerve enlargement and T2 signal hyperintensity, and flattening ratio using postoperative wrist MRI. These findings were compared to a ten-patient asymptomatic persistent CTS control group. Fisher's exact and a Student's two-tailed t-tests were used to determine statistical significance.

RESULTS

In the symptomatic persistent CTS group, 13 (61.9%) incomplete releases were identified, 5 (38.5%) incomplete distally, and 1 (7.7%) incomplete proximally. There was no statistical significance in the rate of incomplete releases when compared to the asymptomatic group (p = 1.00). T2 signal hyperintensity and enlargement at the site of release showed no statistical significance, (p = 0.319 and p = 0.999, respectively). The mean flattening ratio at the site of release in the symptomatic group (2.45 ± 0.7) was statistically significant compared to the asymptomatic group (1.48 ± 0.46), (p = 0.007).

CONCLUSION

Utilizing the established landmarks, the full length of the TCL can be assessed via MRI. Additionally, evaluation of the median nerve flattening ratio at the level of the incomplete release may be utilized as an aid to the clinical management of persistent CTS.

Scoping review of the palmaris profundus muscle: anatomy of a rare variant and its role in carpal tunnel syndrome

The palmaris profundus muscle is a rare anatomical variation of the forearm muscles. It has been described in both cadaveric and clinical studies as a possible cause of carpal tunnel syndrome. We observed three cases of this variant in recent years and decided to perform a scoping review of this uncommon anatomical entity. Major databases were searched to identify all relevant clinical and anatomical studies containing anatomical descriptions of the muscle, including its origin, insertion, and concomitant presence of the proper palmaris longus muscle or the bifid median nerve. In clinical cases, we studied the surgical approach. Sixty-four articles met our inclusion criteria and contained 88 cases of palmaris profundus muscle. The most common origin was the ventral aspect of the radius in the area of insertion of the pronator teres muscle observed in 11 cases (12.5 %). We found 65 cases (73.3%) in which the tendon was inserted into the palmar aponeurosis or palmar fascia after entering the carpal canal. The concomitant presence of the proper palmaris longus muscle was described in 47 cases (53.4%). We identified 10 cases (10.8%) of the bifid median nerve. In 49 of 69 clinical cases (71%), the surgical approach was to resect the variant muscle. The importance of this variant should not be underestimated due to its potential to compress the median nerve. We found a significant disparity in the muscle origin sites, but uniformity of muscle insertion. In cases where the muscle is found during carpal canal surgery, it should be partially resected to ensure complete nerve decompression.

Effectiveness of therapeutic ultrasound for the treatment of carpal tunnel syndrome (the USTINCTS trial): study protocol for a three-arm, prospective, multicentre, randomised controlled trial

INTRODUCTION

There has no consensus on optimal management of carpal tunnel syndrome (CTS), the most common compression neuropathy. Conservative therapy is generally accepted as first-line intervention. Therapeutic ultrasound has been widely reported to be treatment beneficial in nerve regeneration and conduction, and further accelerate compression recovery. The purpose of this study is to investigate the effectiveness of therapeutic ultrasound for CTS treatment.

METHODS AND ANALYSIS

This study protocol entails a three-arm, prospective, multicentre, randomised controlled trial. 162 eligible adult participants diagnosed with mild to moderate CTS by using criteria developed from a consensus survey by the UK Primary Care Rheumatology Society will be assigned to either (1) therapeutic ultrasound, (2) night splint or (3) therapeutic ultrasound +night splint (combined) group. Primary outcome will be difference in Symptom Severity Scale of Boston Carpal Tunnel Questionnaire (BCTQ-SSS) at 6-week between night splint and therapeutic ultrasound +night splint groups. Secondary outcomes include Functional Status Scale of BCTQ, sleep questionnaire for interrupted sleep, EuroQol-5D for general health, Hospital Anxiety and Depression Scale for mental status, Work Limitations Questionnaire-25 for functional limitations at work, Global Rating of Change for treatment success and recurrence rate, physical examination, electrophysiological and ultrasound parameters. Intention-to-treat analyses will be used.

ETHICS AND DISSEMINATION

Ethics committees of all clinical centres have approved this study. The leading centre is Shanghai Sixth People's Hospital, whose approval number is 2021-152. New versions with appropriate amendments will be submitted to the committee for further approval. Final results will be published in peer-reviewed journals and presented at local, national and international conferences.

TRIAL REGISTRATION NUMBER

ChiCTR2100050701.

The effect of median nerve mobilization on two point discrimination

[Purpose] Two-point discrimination (TPD) is expressed as the minimum distance at which two mechanical stimuli applied simultaneously to the skin can be perceived as two separate points. The aim of this study was to investigate the effect of median nerve mobilization on TPD in healthy adults. [Participants and Methods] This study included 120 healthy adults. Participants were randomized according to their gender into the Neural Mobilization Group (NMG) and Control Group (CG). Demographic data of the participants (gender, age, height, weight, BMI, smoking) were recorded and TPD measurement was performed with baseline aesthesiometer on the palm with distal phalanges of the thumb, index and middle finger on the right-left hand. After the baseline TPD test, participants in the NMG performed Median Nerve Mobilization for 14 days. Measurements were taken before and after training. [Results] A statistically significant difference was found in all other measurements in both groups, except for the right and left palm TPD measurements in the control group. [Conclusion] It is thought that it would be beneficial to investigate the healing effects of the neural mobilization applications, which include all parts of the nerve line in disease conditions.

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.

The Myth of Median Nerve in Forearm and Its Role in Double Crush Syndrome: A Cadaveric Study

Purpose: This study aims to histologically compare the median nerve in the arm, forearm, and wrist, to help understand how cervical radiculopathy in a double crush phenomenon causes distal nerve dysfunction at the carpal tunnel and median nerve with concurrent absence of symptoms at the forearm.

Methods: The study was performed on 12 fresh cadaveric upper limbs free from any injury or operation. Male cadavers in the age range of 35–40 years were used. The dissection of the median nerve and the histological examination of the specimens from the arm, forearm, and wrist were conducted to evaluate variations in the epineurium thickness (μm), perineurium thickness (μm), number of fascicles per nerve trunk, area percent of myelin covering, and area percent of neurolemmal sheath.

Results: Morphometric and statistical results of the cadaveric median nerve trunk revealed that the mean epineurium and perineurium thickness measured in H&E-stained sections in the forearm were significantly greater than those in the arm and wrist specimens. Further, the mean percent area of the myelin covering in the forearm was significantly lower than that in the arm and wrist specimens in the sections stained with osmium oxide (p < 0.001). There were, however, no significant differences in the neurolemmal sheath among the arm, forearm, and wrist specimens in the silver-stained sections.

Conclusion: The histological differences explained the high concomitant occurrence of carpal tunnel syndrome (CTS) and cervical radiculopathy and the concurrent absence of symptoms at the forearm. Hence, we suggest cautious evaluation of patients with upper limb symptoms, since the management of these conditions requires a different approach.

CT angiography and MRI of hand vascular lesions: technical considerations and spectrum of imaging findings

Vascular lesions of the hand are common and are distinct from vascular lesions elsewhere because of the terminal vascular network in this region, the frequent hand exposure to trauma and microtrauma, and the superficial location of the lesions. Vascular lesions in the hand may be secondary to local pathology, a proximal source of emboli, or systemic diseases with vascular compromise. In most cases, ischaemic conditions are investigated with Doppler ultrasonography. However, computed tomography angiography (CTA) or dynamic contrast-enhanced magnetic resonance angiography (MRA) is often necessary for treatment planning. MR imaging is frequently performed with MRA to distinguish between vascular malformations, vascular tumours, and perivascular tumours. Some vascular tumours preferentially affect the hand, such as pyogenic granulomas or spindle cell haemangiomas associated with Maffucci syndrome. Glomus tumours are the most frequent perivascular tumours of the hand. The purpose of this article is to describe the state-of-the-art acquisition protocols and illustrate the different patterns of vascular lesions and perivascular tumours of the hand.

Carpal tunnel ultrasound: is the "safe zone" on the ulnar side of the median nerve really avascular?

INTRODUCTION

Numerous publications have studied the regional anatomy of the carpal tunnel to define a "safe zone" to reduce the risk of perioperative neurovascular complications. This zone, located between the ulnar neurovascular bundle and the median nerve, is considered to be safe mainly because of the absence of vascular structures. This study aims to assess the presence of arterioles within this area using superb microvascular imaging (SMI).

MATERIALS AND METHODS

The images from patients who underwent a bilateral routine wrist ultrasound with SMI, between January 28 and February 28, 2019, were retrospectively reviewed by two radiologists to evaluate the presence and location of arterioles in the safe zone. In addition, cadaveric wrists injected with intra-arterial red latex underwent dissection of the carpal tunnel.

RESULTS

The images from 27 patients (54 wrists) were reviewed. In the safe zone, arterioles were seen superficial to the retinaculum in 36 wrists (36/54; 66.7%) and deep to the retinaculum in 21 wrists (21/54; 38.9%). The arterioles located deep to the retinaculum were more frequently found close to the median nerve (21/54; 38.9%) than to the ulnar artery (9/54; 16.7%). In five cadaveric wrists, arterioles were detected superficial to the retinaculum in 3 wrists (3/5; 60%) and deep to the retinaculum in 2 wrists (2/5; 40%).

CONCLUSION

Arterioles can be seen in the safe zone both superficial and deep to the flexor retinaculum. Deep to the retinaculum, they are mainly observed in the proximal aspect of the carpal tunnel and more frequently close to the median nerve.

KEY POINTS

• Superb microvascular imaging (SMI) enables the visualization of arterioles within the "safe zone" of the carpal tunnel (visible both superficial and deep to the flexor retinaculum). • Arterioles were more frequently observed in the proximal aspect of the carpal tunnel. • Deep to the retinaculum, arterioles were more frequently seen in proximity to the median nerve.

Management of Recalcitrant Carpal Tunnel Syndrome

Recalcitrant carpal tunnel syndrome presents a clinical challenge. Potential etiologies of persistent or recurrent symptoms after primary carpal tunnel release include incomplete nerve decompression, secondary sites of nerve compression, unrecognized anatomic variations, irreversible nerve pathology associated with chronic compression neuropathy, perineural adhesions, conditions associated with secondary nerve compression, iatrogenic nerve injury, or inaccurate preoperative diagnosis. Understanding the pertinent surgical anatomy and pathophysiology is essential toward developing an effective diagnostic and treatment strategy. A thorough clinical history and examination guide a comprehensive diagnostic evaluation that includes serial examinations, neurophysiologic testing, and imaging studies. Conservative treatment may provide symptomatic relief; however, surgical management involving revision neuroplasty, neurolysis, nerve reconstruction, and/or local soft-tissue flap augmentation may be indicated in refractory cases.

[Acute carpal tunnel syndrome regarding clinico-anatomical point of view in personified medicine]

Carpal tunnel syndrome (CTS) requires special attention due to its different reasons and course. Knowledge about the variability of median nerve (MN) topography in carpal canal region, features of diagnosis and treatment extends outlooks on this pathology. Aggregating rare clinical cases from the Medline and Pubmed databases is useful to form personified approach. There are 3 types of topographic variations which should be considered to prevent false-positive diagnosis of pathology: recurrent branch location, early bi- and trifurcations of MN, anastomoses. Since acute CTS is treated only by surgery, every surgical approach is aimed at minimally invasiveness and fast recovery. Endoscopic decompression (ED) is more favorable regarding these aspects. However, this method cannot be considered as perfect due to available data about incomplete decompression and certain incidence of recurrences. The last ones are absent after microsurgical decompression as a rule. It can be concluded that only individual approach is advisable for complete release of CTS without iatrogenic damage and recurrences.