Ultrasonographic study for optimal volar needle approach technique for the pronator quadratus to avoid anterior interosseous nerve injury.

We visualized the entry point (EP) of the anterior interosseous nerve (AIN) into the pronator quadratus (PQ) in the distal forearm with ultrasonography and examined its location to identify the safe zone for approaching the PQ on the volar side. The forearms of healthy volunteers without any musculoskeletal problems of the upper extremities were examined. Using high-resolution ultrasonography, the volar aspects of the forearms were scanned with elbows flexed at 90°. Using the images obtained, several parameters for distance were measured. Overall, 20 forearms were examined. The means ± standard deviations of the forearm length (A) and the distance from the wrist to the EP of the AIN (B), from the lateral margin of the ulna to the medial margin of the radius on the interosseous membrane (IOM) (C), from the lateral margin of the ulna to the AIN on the IOM (D), from the AIN to the skin surface (E) were 25.50 ± 1.56 cm, 4.18 ± 0.61 cm, 12.99 ± 1.99 mm, 6.63 ± 1.46 mm, and 18.85 ± 3.03 mm, respectively. The mean values of B/A and D/C were 0.16 ± 0.02 and 0.51 ± 0.08, respectively. We utilized high-resolution ultrasound to locate the EP of the AIN in the distal forearm in a three-dimensional space. These findings may provide insights into the nerve's course and assist in establishing a safety zone to minimize the chances of accidental nerve injuries when inserting a needle toward the PQ.