Accuracy of needle placement in cadavers: non-guided versus ultrasound-guided.

Objective: To compare the accuracy rates of non-guided vs. ultrasound-guided needle placement in four lower limb muscles (tibialis posterior, peroneus longus, and short and long heads of the biceps femoris).

Methods: Two electromyographers examined the four muscles in each of eight lower limbs from four fresh frozen cadavers. Each electromyographer injected an assigned dye into each targeted muscle in a lower limb twice (once without guidance, another under ultrasound guidance). Therefore, four injections were done in each muscle of one lower limb. All injections were performed by two electromyographers using 18 gauge 1.5 inch or 24 gauge 2.4 inch needles to place 0.5 mL of colored acryl solution into the target muscles. The third person was blinded to the injection technique and dissected the lower limbs and determined injection accuracy.

Results: A 71.9% accuracy rate was achieved by blind needle placement vs. 96.9% accuracy with ultrasound-guided needle placement (p=0.001). Blind needle placement accuracy ranged from 50% to 93.8%.

Conclusion: Ultrasound guidance produced superior accuracy compared with that of blind needle placement in most muscles. Clinicians should consider ultrasound guidance to optimize needle placement in these muscles, particularly the tibialis posterior.