Ultrasound Investigation of the Radial Nerve's Superficial Branch: Reducing the Risk of K-Wire Insertion Damage in Distal Radius Fractures.

Background: Kirschner wire (K-wire) insertion during surgery for distal radius fractures carries a risk of damaging the radial nerve's superficial branch. In this prospective study, we investigated the relationship between the radial nerve's superficial branch and the radius using ultrasound to minimize risk.

Methods: We collected data from 101 healthy volunteers (202 limbs; 51 men; mean age: 40.6 years). We ultrasonographically assessed the courses of the radial nerve's dorsal and superficial palmar branches at 0, 1, 2, and 3 cm proximal to the radial styloid process tip. The positional relationship between the radial nerve's superficial branch and the radius was determined by splitting the radius's ultrasound map into 4 sections (R1-R4) from the palmar side. The section containing the dorsal and palmar branch midpoints was determined for each height.

Results: In many limbs, the dorsal branch tended to wrap from the proximal palmar to the distal dorsal side at 1 to 2 cm proximal to the radial styloid process tip. In approximately 90% of limbs, the palmar branch ran along the radius's palmar side rather than the radial surface.

Conclusions: A small incision enabling direct view may be the best approach for avoiding nerve damage when the superficial branch is less than or equal to 2 cm proximal to the tip of the radial styloid process. Inserting the K-wire from the dorsal side of the radius may be safer for more proximal locations. We recommend a preoperative ultrasound examination to determine the course of the superficial branches of the radial nerve in each patient.