Ann Rehabil Med.  2012 Apr;36(2):187-196. 10.5535/arm.2012.36.2.187.

Surface Mapping of Motor Points in Biceps Brachii Muscle

• Moon JY
• Hwang TS
• Sim SJ
• Chun SI
• Kim M

• KMID: 2266756
• DOI: http://doi.org/10.5535/arm.2012.36.2.187

Abstract

OBJECTIVE
To localize the site of motor points within human biceps brachii muscles through surface mapping using electrophysiological method. METHOD: We recorded the compound muscle action potentials of each lattice of the biceps brachii in 40 healthy subjects. Standardized reference lines were made as the following: 1) a horizontal reference line (elbow crease) and 2) a vertical reference line connecting coracoid process and mid-point of the horizontal reference line. The Compound muscle action potentials were mapped in reference to the standardized reference lines. The locations of motor points were mapped to the skin surface, in the ratio to the length of the vertical and the half of the horizontal reference lines.
RESULTS
The motor point of the short head of biceps was located at 69.0+/-4.9% distal and 19.1+/-9.5% medial to the mid-point of horizontal reference line. The location of the motor point of the long head of the biceps was 67.3+/-4.3% distal and 21.4+/-8.7% lateral. The motor point of the short head of the biceps was located more medially and distally in the male subjects compared to that in the female (p<0.05).
CONCLUSION
This study showed electrophysiological motor points of the biceps brachii muscles through surface mapping. This data might improve the clinical efficacy and the feasibility of motor point targeting, when injecting botulinum neurotoxin in biceps brachii.

Keyword

Motor point; Surface mapping; Biceps brachii; Botulinum toxin; Motor point block

MeSH Terms

Action Potentials
Botulinum Toxins
Female
Head
Humans
Male
Muscles
Skin
Botulinum Toxins

Figure

• 

  Fig. 1 Motor point mapping method. The coracoid process and end points of the elbow crease in 90° flexion of the elbow were identified as reference points. Standardized reference lines were made as a horizontal reference line drawn between both end points of the elbow and a vertical reference line drawn between mid-point of the horizontal reference line and coracoid process. Stimulating electrode was located on musculocutaneous nerve at the proximal 1/3 area on anteromedial surface of the arm. Recording surface electrode was located on the long head of biceps brachii muscle area.

• 

  Fig. 2 Diagrammatic drawing of measurement of the location of the motor point of the biceps brachii muscle. The distance from the vertical reference line to the motor point was recorded as an x value and the distance from the coracoid process to the point where the perpendicular line crossed the vertical reference line was defined as a y value.

• 

  Fig. 3 A plot of the location of the motor points in the biceps brachii muscles. x value is the distance from the vertical reference line to the motor point, y value is the distance from the coracoid process to the point where the perpendicular line crossed the vertical reference line. SH: Short head, LH: Long head.

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