Ogonna Kenechi Nwawka MD, Presenter: Nothing to Disclose

Theodore T. Miller MD, Abstract Co-Author: Nothing to Disclose

Gregory Roy Saboeiro MD, Abstract Co-Author: Research funded, Terumo Corporation Speakers Bureau, Bioventus LLC

Shari Tamar Jawetz MD, Abstract Co-Author: Nothing to Disclose

Our current clinical technique for ultrasound-guided perineural injection consists of placing the needle along both the superficial and deep surfaces of the nerve to obtain circumferential distribution of the injectate. This study aims to determine if a single needle position will produce circumferential coating of a nerve.

For this IRB approved study, 6 upper extremity and 3 pelvic fresh cadaveric specimens were obtained. For the upper extremity, a 25 gauge hypodermic needle was positioned along the deep surface of the median nerve in the carpal tunnel, the radial nerve in the radial tunnel, and the ulnar nerve in the cubital tunnel, and 2 ml of dilute Omnipaque-300 contrast was injected for each nerve. In the pelvis, a 22 gauge spinal needle was positioned deep to the sciatic nerve, and 5 ml of contrast was injected. Thus, 18 upper extremity nerves (6 median, 6 radial, 6 ulnar) and 6 sciatic nerves were injected. All needle placements and injections were performed under ultrasound guidance by two experienced musculoskeletal radiologists. The specimens then underwent CT scanning, and the distribution of perineural contrast was assessed by a musculoskeletal radiologist not involved in the injections.

6/6 radial and 6/6 ulnar nerves demonstrated circumferential distribution of injectate on CT. Only 3/6 median nerves had circumferential coverage. 6/6 sciatic nerves demonstrated circumferential coverage on CT. The average length of spread for the upper extremity perineural injectate was 12.5 cm, with a range of 5.5 cm to 20 cm. For the sciatic nerves, the average length of spread was 10.3 cm, ranging from 6.4 cm to 15.5 cm.

Using the clinical volumes of injectate that we use for upper extremity nerves and the sciatic nerve, positioning adjacent to the deep surface of each nerve was sufficient to produce circumferential coating of the nerve, except in the tight fibroosseus space of the carpal tunnel.

We no longer try to position the needle adjacent to two opposite sides of a nerve during ultrasound-guided perineural injections, except in the carpal tunnel.

Nwawka, O, Miller, T, Saboeiro, G, Jawetz, S, Ultrasound-guided Perineural Injection of Upper Extremity and Sciatic Nerves: Does Single Needle Position Produce Circumferential Nerve Coverage?.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14008984.html