The accuracy of needle placement in lower-limb muscles: a blinded study.

Objective: To assess the accuracy of common anatomic guides for electromyographic needle placement in muscles.

Design: Blinded study. The dissector identified different needle placements by a random number attached to a wire in the insertion site.

Setting: A university anatomy laboratory.

Cadavers: Ten cadaver lower limbs.

Interventions: By using techniques published in texts by Gieringer and Delagi and Perotto, clinical electromyographers palpated and measured appropriate locations for needle placement. A thin wire was inserted through the needle into 36 different muscles in 10 cadavers, resulting in 263 targeted muscles. An anatomist blinded to intended location dissected and recorded muscles and other tissues that the wire pierced or passed near.

Main Outcome Measures: Targeted muscle penetration, final resting place of the wire tip, and proximity to vital structures.

Results: Fifty-seven percent of insertions penetrated the intended muscle. The wire tip was in the intended muscle 45% of the time. Seventeen percent of insertions penetrated or passed within 5mm of an important structure, including nerve (9.1%), tendon (3.0%), named artery (2.7%), vein (2.7%), or joint (0.8%). Specific muscle accuracy was highly variable, from 0% for 12 tries in various deep hip muscles to 100% of 10 tries in the vastus medialis.

Conclusion: The accuracy of blind needle placement varied according to muscle. With the blind insertion technique, more accurate and safe needle placement strategies can be developed.