Surgical Anatomy of the Radial Nerve at the Dorsal Region of the Humerus

Abstract

Background: Surgery for humeral shaft fractures is associated with a high risk of iatrogenic radial nerve palsy (RNP).Plausible causes are difficult anatomical conditions and variants. Methods:We performed a cadaveric study with 23 specimens (13 female and 10 male Caucasian donors) to assess the course and anatomy of the radial nerve (RN) with its branches alongside the humeral shaft. The accuracy of identification of the RN in the surgical field was analyzed by measuring the location, course, diameter, and form of each nerve and vessel of interest.Results: The RN is not a single structure running alongside the humeral shaft; at least 4 parallel structures crossed the dorsal humerus in all subjects. The RN was accompanied by 2 vessels and at least 1 other nerve, which we named the musculocutaneous branch (MCB). With an oval profile and an average diameter of 3.1 mm (range, 2.6 to 3.8 mm), the MCB was thinner but, in some cases, close to the average diameter of 4.7 mm (range, 4.0 to 5.2 mm) of the RN, which had a round profile. Both accompanying vessels had similar diameters: 3.5 mm (range, 2.6 to 4.2 mm) for the radial collateral artery and 4.0 mm (range, 2.9 to 4.4 mm) for the medial collateral artery. In 20 (87%) of the cases, the RN ran proximal to and in 3 (13%) of the cases, distal to the MCB. Furthermore, a distal safe zone of at least 110 mm (range, 110 to 160 mm) was found, measured from the radial (lateral) epicondyle proximally. Conclusions:The RN does not cross the dorsal humerus alone, as often stated in anatomical textbooks, but runs parallel to vessels and at least 1 nerve branch with a similar appearance. Thus, for reliable preservation of the RN, we recommend identification and protection of all crossing structures in posterior humeral surgeries 110 mm proximal to the radial epicondyle.T his study was approved by the institutional review board (406/17).

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

“…52 Depending on the location of the RN on the humerus or the spot where it pierces the intermuscular septum, it may be at risk during operative procedures of the humerus (e.g., in fixation of a humerus fracture). 53 At the level of the elbow, the RN usually divides into a superficial branch (SB) and a deep branch. An accessory brachioradialis muscle can cause entrapment in that region.…”

“… 52 Depending on the location of the RN on the humerus or the spot where it pierces the intermuscular septum, it may be at risk during operative procedures of the humerus (e.g., in fixation of a humerus fracture). 53 …”