Ultrasound guidance may be augmented with passive muscle movement and or electrical stimulation to identify the target muscle. The practitioner is performing passive flexion of the lateral four toes. On ultrasound, you can see the movement of the flexor digitorum longus muscle in the lower right quadrant of the screen. With electrical stimulation, you will see similar rhythmic movements of the target muscle on ultrasound. In addition to the contraction seen on ultrasound, you may see gross movement of the affected joint. For example, in this case you can visualize flexion of the lateral four toes of the flexor digitorum longus muscle as it is stimulated. Although not demonstrated in the model used for this video, electromyography, or EMG, may also be used to augment ultrasound guidance. EMG guidance can be added once the needle tip is thought to be in the target muscle. At that time, gentle passive stretch of the spastic target muscle should produce a confirmatory increase in motor unit action potentials. This can be especially useful if the patient has a contraindication to electrical stimulation or if there is a concern that electrical stimulation will cause high amplitude muscle spasms.

ultrasound guidance

muscle movement

electrical stimulation

flexor digitorum longus muscle

electromyography (EMG)