Superficial radial nerve-lateral antebrachial cutaneous nerve anatomic variation

Anatomical variations in the sensory innervation of the dorsal surface of the first digit space, a cadaveric study with clinical consequences

INTRODUCTION

Radial nerve palsy is a classical complication of a humeral shaft fracture. In clinical practice, motor palsy of the radial nerve is sometimes observed without an abnormality felt in the sensory territory.

HYPOTHESIS

We hypothesised that this dissociation between sensory and motor involvement is related to anatomical variations of the sensory innervation of the dorsal surface of the first digit space, thus, we decided to study the nature and frequency of these variations.

MATERIAL AND METHOD

A cadaveric study was conducted on 24 upper limbs to analyse the truncal origin of the sensory branches innervating the dorsal surface of the first digit space.

RESULTS

The sensory branch of the radial nerve (SBRN) participated in the innervation of the dorsal surface of the first digit space in 22 limbs, an anatomical variation was present in 2 cases with a mixed innervation by the SBRN and the lateral cutaneous nerve of forearm (LCNF) in 1 case and singular innervation by LCNF, with no SBRN involvement, in 1 case. Communications between SBRN and LCNF were found in 7 cases.

DISCUSSION

Pure motor radial damage, without a sensory deficit of the dorsal surface of the first digit space, does not preclude a complete traumatic injury of the radial nerve. The sensory innervation of this region can be relayed by a branch of the LCNF.

LEVEL OF EVIDENCE

IV; cadaveric study.

The communication patterns between the lateral antebrachial cutaneous nerve and the superficial branch of the radial nerve

INTRODUCTION

The superficial branch of the radial nerve (SBRN) and the lateral antebrachial cutaneous nerve (LACN) are sensory nerves coursing within the forearm in a close relationship. This high degree of overlap and eventual communication between the nerves is of great surgical importance. The aim of our study is to identify the communication pattern and overlap of the nerves, to localize the position of this communication in relation to a bony landmark, and to specify the most common communication patterns.

MATERIALS

and methods: One hundred and two adult formalin-fixed cadaveric forearms from 51 cadavers of Central European origin were meticulously dissected. The SBRN, as well as the LACN, were identified. The morphometric parameters concerning these nerves, as well as their branches and connections, were measured with a digital caliper.

RESULTS

We have described the primary (PCB) and secondary communications (SCB) between the SBRN and the LACN and their overlap patterns. One hundred and nine PCBs were found in 75 (73.53%) forearms of 44 (86.27%) cadavers and fourteen SCBs in eleven hands (10.78%) of eight cadavers (15.69%). Anatomical and surgical classifications were created. Anatomically, the PCBs were classified in three different ways concerning: (1) the role of the branch of the SBRN within the connection; (2) the position of the communicating branch to the SBRN; and (3) the position of the LACN branch involved in the communication to the cephalic vein (CV). The mean length and width of the PCBs were 17.12mm (ranged from 2.33-82.96mm) and 0.73mm (ranged from 0.14-2.01mm), respectively. The PCB was located proximally to the styloid process of the radius at an average distance of 29.91mm (ranged from 4.15-97.61mm). Surgical classification is based on the localization of the PCBs to a triangular zone of the SBRN branching. The most frequent branch of the SBRN involved in the communication was the third (66.97%). Due to the frequency and position of the PCB with the third branch of the SBRN, the danger zone was predicted. According to the overlap between the SBRN and the LACN, we have divided 102 forearms into four types: (1) no overlap; (2) present overlap; (3) pseudo-overlap; and (4) both present and pseudo-overlap. Type 4 was the most common.

CONCLUSION

The patterns of communicating branch arrangements appeared to be not just a rare phenomenon or variation, but rather a common situation highlighting clinical importance. Due to the close relationship and connection of these nerves, there is a high probability of simultaneous lesion.

Anatomical characterization of acupoint large intestine 4

Large intestine 4 (LI4) is a major acupoint used in various treatments in acupuncture and Traditional Chinese Medicine. There are structures associated within the region of LI4 that have three-dimensional anatomical relationship that needs further characterization. The aims of this study were: (a) to observe the anatomical variation of structures around LI4; (b) to observe specific overlap of structures around LI4. A 1256 mm² area was dissected in 25 cadaveric hands around LI4. Nondissected areas were marked with pins as reference points. Dissections were photographed with a fixed camera. Subsequently, images were imported to Adobe Photoshop 2020 and analyzed. Descriptive statistics and graphs were compiled using Graphpad Prism 2020. The tributaries of the dorsal venous plexus (22.3%), branches of superficial radial nerve (18.9%), first dorsal interosseous muscle (52.4%), arterial branches in the first interosseous space (10.2%), and deep ulnar nerve (4.0%) were observed in the area of LI4. One branch of the superficial radial nerve passed through LI4. The deep ulnar nerve was found in the bulk of the first dorsal interosseous muscle. Several structures observed intersected at LI4. The superficial radial nerve interweaved with the dorsal venous plexus superficially. The deep ulnar nerve passed anterior to the second palmar metacarpal artery before entering into the first dorsal interosseous muscle. These results provide anatomical evidence and variation into the vascular contributions at LI4.

Ultrasonographic Study of the Anatomical Relationship Between the Lateral Antebrachial Cutaneous Nerve and the Cephalic Vein

OBJECTIVE

To define the anatomy of the lateral antebrachial cutaneous nerve (LABCN) and the cephalic vein (CV) in the anterior forearm region of living humans using ultrasonography for preventing LABCN injury during cephalic venipuncture.

METHODS

Thirty forearms of 15 healthy volunteers were evaluated using ultrasonography to identify the point where the LABCN begins to contact with the CV, and the point where the LABCN separates from the CV. The LABCN pathway in the forearm in relation to a nerve conduction study was also evaluated.

RESULTS

The LABCNs came in contact with the CV at a mean of 0.6±1.6 cm distal to the elbow crease, and separated from the CV at a mean of 7.0±3.4 cm distal to the elbow crease. The mean distance between the conventionally used recording points (point R) for the LABCN conduction study and the actual sonographic measured LABCN was 2.4±2.4 mm. LABCN usually presented laterally at the point R (83.3%).

CONCLUSION

The LABCN had close proximity to the CV in the proximal first quarter of the forearm. Cephalic venipuncture in this area should be avoided, and performed with caution if needed.