J Korean Med Sci.  2007 Jun;22(3):459-462. 10.3346/jkms.2007.22.3.459.

Anatomic Motor Point Localization of the Biceps Brachii and Brachialis Muscles

• Park BK
• Shin YB
• Ko HY
• Park JH
• Baek SY

• KMID: 1778354
• DOI: http://doi.org/10.3346/jkms.2007.22.3.459

Abstract

Injection of the neurolytic agents into motor points of the biceps brachii or brachialis muscles is an effective treatment of spasticity of the elbow flexors in many stroke survivors. Accurate localization of the motor points of each muscle is necessary for enhancing the efficacy of motor point blocks. To identify the precise locations of the motor points (terminal nerve endings) of the biceps brachii and brachialis muscles in relation to anatomic surface landmarks for motor point blocks, we dissected 23 limbs from 12 cadavers. A reference line was defined as a line connecting the coracoid process with the lateral epicondyle of the humerus. The location of the motor points of the biceps brachii and brachialis muscles was identified in reference to the reference line. The motor point of the biceps brachii muscle was found to be approximately half of the reference line. In the brachialis muscle, the location of the motor point was 70% of the reference line from the coracoid process and 2 cm medial to the line. The results are expected to facilitate effective localization of the motor point block of these muscles in selective motor nerve block.

Keyword

Elbow; Flexor; Muscle Spasticity; Nerve Endings; Nerve Block

MeSH Terms

Adult
Aged
Aged, 80 and over
Cadaver
Female
Humans
Humerus/anatomy & histology
Male
Middle Aged
Motor Neurons/*drug effects
Muscle, Skeletal/*anatomy & histology
Muscles
Nerve Block
Shoulder
Skin/*drug effects

Figure

• 

  Fig. 1 Diagrammatic drawing of measurement of the location of the motor point of the brachialis muscle. The coracoid process and lateral epicondyle of the humerus were identified as reference points. The shortest distance between the reference points was measured and was defined as a reference line. The distance from the 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 reference line was defined as a y value.

• 

  Fig. 2 A plot of the location of the motor points in the biceps brachii muscles. The normalized ratio indicates the ratio of the distance from the coracoid process to the length of the reference line connecting from the coracoid process to the lateral epicondyle of the humerus. SH, short head; LH, long head.

• 

  Fig. 3 A plot of the location of the motor points in the brachialis muscle; x axis is the distance from the reference line to the motor point and y axis is the distance from the coracoid process to the point where the perpendicular line crosses the reference line. MP1, the first motor point; MP2, the second motor point.

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