Surgical anatomy of the radial nerve in the arm: a cadaver study

Anatomical Variants of the Upper Limb Nerves: Clinical and Preoperative Relevance

Profound knowledge of nerve variations is essential for clinical practice. It is crucial for interpreting the large variability of a patient's clinical presentation and the different mechanisms of nerve injury. Awareness of nerve variations facilitates surgical safety and efficacy. Clinically significant anatomical variations can be classified into two main groups: variability in the course of the nerve and variability of structures surrounding the nerve. In this review article we focus on the most common nerve variants of the upper extremity and their clinical relevance.

Two fingerbreadths, one finger's width: on the proximity of the radial nerve to the deltoid tuberosity

INTRODUCTION

The aim of this study was to find a convenient technique to evaluate the location of the radial nerve (RN) with reference to the deltoid tuberosity (DT).

MATERIALS AND METHODS

Sixty-eight upper extremities, embalmed using a modified version of Thiel's method, were included in the study. The interval between the tip of the greater tubercle of the humerus and the distal tip of the lateral humeral epicondyle (LE) was defined as humeral length (HL). The most prominent point of the DT was used as the point of reference. Through this point, a horizontal reference line which met the humeral axis at the dorsal side of the humeral shaft was simulated. The longitudinal distance between the crossing point of the horizontal line and the humeral axis and the RN was measured (distance 1). The interval between the intersection point and the reference point at the DT was measured (distance 2). Data were evaluated in centimeters.

RESULTS

For the whole sample, the HL averaged 31.0 cm (SD: 2.3; range 26.2-36.9). Distance 1 averaged 2.2 cm (SD: 0.3; range 1.6-3.1), and distance 2 averaged 1.2 cm (SD: 1.0; range 0-2.8). The HL was larger in the male group when compared to females (p < 0.001; males mean: 32.2 cm; females mean 29.5 cm). There was no difference regarding distance 2 (p = 0.59; males mean: 1.2 cm; females mean: 1.3 cm) between the sexes. Distance 1 was significantly (p = 0.02) larger in the male group (mean: 2.3 cm) when compared to females (mean: 2.1 cm). Concerning sides, there were no differences regarding all evaluated parameters (HL: p = 0.6; Distance 1: p = 0.6; distance 2: p = 0.8).

CONCLUSIONS

This study provides an easily applicable technique to localize the RN with reference to the DT.

The risk of iatrogenic radial nerve and/or profunda brachii artery injury in anterolateral humeral plating using a 4.5 mm narrow DCP: A cadaveric study

INTRODUCTION

Fixation of humeral shaft fractures with a plate and screws can endanger the neurovascular structure if proper care is not taken. No studies to our knowledge have studied the risk of iatrogenic radial nerve and/or profunda brachii artery (RNPBA) injury from each screw hole of a 4.5 mm narrow dynamic compression plate (narrow DCP). The purpose of this study is to evaluate the risk of RNPBA injury in anterolateral humeral plating with a 4.5 mm narrow DCP.

MATERIAL AND METHODS

18 humeri of 9 fresh-frozen cadavers in the supine position were exposed via the anterolateral approach with 45 degrees of arm abduction. A hypothetical fracture line was marked at the midpoint of each humerus. A precontoured ten-hole 4.5mm narrow DCP was applied to the anterolateral surface of the humerus using the fracture line to position the center of the plate. All screw holes were drilled and screws inserted. The cadaver was then turned over to the prone position with 45 degrees of arm abduction, and the RNPBA exposed. The holes through in which 100% of the screw had contact with or penetrated the RNPBA were identified as dangerous screw holes, while lesser percentages of contact were defined as risky.

RESULTS

The relative distance ratios of the entire humeral length from the lateral epicondyle of the humerus to the 4th, 3rd, 2nd and 1st proximal holes were 0.64, 0.60, 0.56 and 0.52, respectively. The most dangerous screw hole was the 2nd proximal, in which all 18 screws had contacted or penetrated the nerve, followed by the risky 1st (12/18), 3rd (8/18) and 4th (2/18) holes.

CONCLUSION

In humeral shaft plating with the 4.5mm narrow DCP using the anterolateral approach, the 2nd proximal screw hole carries the highest risk of iatrogenic radial nerve and/or profunda brachii artery injury.