An anatomical study of the superficial palmar communicating branch between the median and ulnar nerves

Anatomical variations of the brachial plexus in adult cadavers: A descriptive study and clinical significance

BACKGROUND

Brachial plexus injury is recognized as one of the most severe clinical challenges due to the complex anatomical configuration of the brachial plexus and its propensity for variation, which complicates safe clinical interventions. This study aimed to ascertain the prevalence and characterize the types of brachial plexus variations, and to elucidate their clinical implications.

MATERIALS AND METHODS

We conducted meticulous dissections of 60 formalin-fixed cadavers' upper arm, axilla and lower neck to reveal and assess the roots, trunks, divisions, cords, and branches of the brachial plexus. The pattern of branching was noted by groups of dissecting medical students and confirmed by the senior anatomists. The variations discovered were record and photographed using a digital camera for further analysis.

RESULTS

Variations in the brachial plexus were identified in 40 of the 60 cadavers, yielding a prevalence rate of 66.7%. These variations were classified into root anomalies (2.1%), trunk anomalies (8.5%), division anomalies (2.1%), and cord anomalies (4.3%). Notably, anomalies in communicating branches were observed in 39 cadavers (83.0%): 14 with bilateral anomalies, 14 with anomalies on the left side, and 11 on the right side. These communicating branches formed connections between the roots and other segments, including trunks, cords, and terminal nerves, and involved the median, musculocutaneous, and ulnar nerves.

CONCLUSION

The frequency and diversity of brachial plexus variations, particularly in communicating branches, are significant in cadavers. It is imperative that these variations are carefully considered during the diagnostic process, treatment planning, and prior to procedures such as supraclavicular brachial plexus blocks and nerve transfers, to mitigate the risk of iatrogenic complications.

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.

Density mapping of nerve endings in the skin of the palm and flexor retinaculum of the hand. Application to open carpal tunnel release

In order to re-evaluate the safest area to incise skin and the flexor retinaculum (FR) when performing a carpal tunnel release (CTR), we carried out a mapping study of the nerve endings in the skin and FR on cadaver specimens, which, unlike previous studies for the first time, includes histomorphometry and image digital analysis. After dividing the skin and FR into 20 and 12 sections, respectively, we carried out a histomorphological analysis of nerve endings. The analysis was performed by two neutral observers on 4-μm histological sections stained with hematoxylin-eosin (H-E), and Klüver-Barrera with picrosirius red (KB + PR) methods. A semi-automatic image digital analysis was also used to estimate the percentage of area occupied per nerve. We observed a lower quantity of nerve endings in the skin of the palm of the hand in line with the ulnar aspect of the 4th finger. The ulnar aspect of the FR was the most densely innervated. However, there are no statistically significant differences between sections in the percentage of area occupied per nerve both in the skin and in the FR. We concluded that there is not a safe area to incise when performing carpal tunnel surgery, but taking into account the quantity of nerve endings present in skin and FR, we recommend an incision on the axis of the ulnar aspect of 4th finger when incising skin and on the middle third of the FR for CTR.

The Berrettini palmar neural communicating branch: a study of 27 cadaveric specimens and determination of a high-risk surgical zone

In this cadaveric study, we analysed digital images of dissected palms to define the location and length of superficial connections between the median and the ulnar nerves (Berrettini communicating branches). We found the connections present in 12 of 27 hands. We used a coordinate model to define their location relative to seven specified landmarks. The model revealed that the Berrettini communicating branches were positioned consistently, and we defined a high-risk zone in the palm that fully contained seven of the 12 connections, while others had minor projections outside the zone. We conclude that awareness of this high-risk zone in the palm can be of some help to reduce the risk of iatrogenic nerve injury, however, any operation in the palm must always be done with great care to visualize and protect any possible anatomically unusual structures.

Carpal tunnel release with a new mini-incision approach versus a conventional approach, a retrospective cohort study

PURPOSE

We have make use of a new method to perform carpal tunnel release (CTR) through a 1.5-2.0 cm long incision The aim of this study is to introduce this method and to compare the effectiveness and safety of this approach to the conventional one.

METHODS

We included consecutive patients diagnosed with primary carpal tunnel syndrome (CTS) who had CTR from January 2015 to September 2016. A total of 85 patients were included in our study. Among them, 42 patients with mini-incision approach were enrolled in group A, and the other 43 patients with conventional approach were enrolled in group B. Objective tests and subjective evaluations were performed to compare the outcomes of mini-incision approach with the conventional approach. Postoperative complications after the two approaches were also compared.

RESULTS

At the 12-months follow-up, all patients in both groups got recovery. We found no significant differences between the two groups in postoperative pinch strength, grip strength, 2-point discrimination (2-PD), visual analogue scale (VAS) score, Levine score and the Disabilities of the Arm, Shoulder and Hand (DASH) score (P > 0.05). However, at the one-month follow-up, the percentage of patients with wound pain in group A was significantly lower than that in group B (0.05% vs. 0.23%, P = 0.03). At the 12 months follow-up, the number of patients with persistent wound pain and pillar pain in group B were 2 (4.7%) and 3 (7.0%) respectively, while no patients showed wound pain and pillar pain in group A.

CONCLUSION

Patients with mini-incision approach have satisfactory surgical outcomes, low postoperative complications, and good appearance.

A cadaveric study of the distribution pattern of the cutaneous sensory fibres of the distal palm of the hand

We investigated the cutaneous innervation of the distal palm, an area frequently dissected by the hand surgeon. Ten (five paired) fresh-frozen cadaveric hands were dissected under 3.0× loupe magnification. Volar branches were found on both sides in the majority of digits. They originated alongside, or at the proximal margin of, the A1 pulley in 84% of digits. The mean distance from the palmar digital crease to the origin of volar branches was 21 mm.

From the brachial plexus to the hand, multiple connections between the median and ulnar nerves may serve as bypass routes for nerve fibres

Axons from the median and ulnar nerves can pass to each other through aberrant connections between them. Multiple interconnections between the nerves may provide a detour route for nerve fibres going to the hand. We investigated the incidence of variations and the associations between them in 90 cadaveric upper limbs. In 91% of upper limbs, one to five variations were found, with several statistically significant associations. The contribution of the C8 nerve to the lateral cord was positively associated with an accessory contribution of the lateral cord to the ulnar nerve. The latter variation showed positive association with the occurrence of any of the variations in the hand itself. Ulnar innervation of the superficial head of the flexor pollicis brevis was positively associated with the Riche-Cannieu communication. The co-existence of the variations and their associations may be the explanation for unusual clinical findings related to median and ulnar conduction, which appear contrary to anatomical knowledge.