Optimal Needle Placement for Extensor Hallucis Longus Muscle: A Cadaveric Study

Optimal needle placement for extensor hallucis longus muscle using ultrasound verification

INTRODUCTION

The extensor hallucis longus (EHL) muscle is important for diagnosis of neurologic lesions. It is also a target muscle for treatment. We investigated EHL with ultrasonography to determine optimal needle placement for safety and accuracy.

METHODS

A total of 96 legs of 48 healthy volunteers were examined through ultrasonography. Four published electromyographic methods for finding the EHL were assessed. We identified the midpoint of EHL (MD) using landmarks to determine optimal needle placement.

RESULTS

Mean values of bimalleolar line-MD on skin (MD-S) and tibial crest-MD-S were 10.5 ± 1.2 cm and 3.6 ± 0.4 cm, respectively. The depth of MD was 1.6 ± 0.2 cm. According to 4 EMG methods, the probability of needle penetrating EHL was 13% to 79% and that of needle penetrating the neurovascular bundle was 50% to 89%.

CONCLUSIONS

Using ultrasonography, we could determine optimal needle placement in the EHL. Muscle Nerve 59:331-336, 2019.

Optimal Placement of Needle Electromyography in Extensor Indicis: A Cadaveric Study

Objective

To identify the center of extensor indicis (EI) muscle through cadaver dissection and compare the accuracy of different techniques for needle electromyography (EMG) electrode insertion.

Methods

Eighteen upper limbs of 10 adult cadavers were dissected. The center of trigonal EI muscle was defined as the point where the three medians of the triangle intersect. Three different needle electrode insertion techniques were introduced: M1, 2.5 cm above the lower border of ulnar styloid process (USP), lateral aspect of the ulna; M2, 2 finger breadths (FB) proximal to USP, lateral aspect of the ulna; and M3, distal fourth of the forearm, lateral aspect of the ulna. The distance from USP to the center (X) parallel to the line between radial head to USP, and from medial border of ulna to the center (Y) were measured. The distances between 3 different points (M1– M3) and the center were measured (marked as D1, D2, and D3, respectively).

Results

The median value of X was 48.3 mm and that of Y was 7.2 mm. The median values of D1, D2 and D3 were 23.3 mm, 13.3 mm and 9.0 mm, respectively.

Conclusion

The center of EI muscle is located approximately 4.8 cm proximal to USP level and 7.2 mm lateral to the medial border of the ulna. Among the three methods, the technique placing the needle electrode at distal fourth of the forearm and lateral to the radial side of the ulna bone (M3) is the most accurate and closest to the center of the EI muscle.