Localization of the nerves innervating the pelvic floor muscles: an application to pelvic pain treatment

Localisation of the centre of the highest region of muscle spindle abundance of anterior forearm muscles

The centre of the highest region of muscle spindle abundance (CHRMSA) in the intramuscular nerve-dense region has been suggested as the optimal target location for injecting botulinum toxin A to block muscle spasms. The anterior forearm muscles have a high incidence of spasticity. However, the CHRMSA in the intramuscular nerve-dense region of the forearm anterior muscle group has not been defined. This study aimed to accurately define the body surface position and the depth of CHRMSA in an intramuscular nerve-dense region of the anterior forearm muscles. Twenty-four adult cadavers (57.7 ± 11.5 years) were included in this study. The curved line close to the skin connecting the medial and lateral epicondyles of the humerus was designated as the horizontal reference line (H line), and the line connecting the medial epicondyle of the humerus and the ulnar styloid was defined as the longitudinal reference line (L line). Modified Sihler's staining, haematoxylin-eosin staining and computed tomography scanning were employed to determine the projection points (P and P') of the CHRMSAs on the anterior and posterior surfaces of the forearm. The positions (PH and PL) of point P projected onto the H and L lines, and the depth of each CHRMSA, were determined using the Syngo system. The PH of the CHRMSA of the ulnar head of pronator teres, humeral head of pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, ulnar part of flexor digitorum superficialis, radial part of flexor digitorum superficialis, flexor pollicis longus, ulnar part of flexor digitorum profundus, radial portion of flexor digitorum profundus and pronator quadratus muscles were located at 42.48%, 45.52%, 41.20%, 19.70%, 7.77%, 25.65%, 47.42%, 53.47%, 12.28%, 38.41% and 51.68% of the H line, respectively; the PL were located at 18.38%, 12.54%, 28.83%, 13.43%, 17.65%, 32.76%, 57.32%, 64.12%, 20.05%, 45.94% and 88.71% of the L line, respectively; the puncture depths were located at 21.92%, 27.25%, 23.76%, 18.04%, 15.49%, 31.36%, 26.59%, 41.28%, 38.72%, 45.14% and 53.58% of the PP' line, respectively. The percentage values are the means of individual values. We recommend that the body surface puncture position and depth of the CHRMSA are the preferred locations for the intramuscular injection of botulinum toxin A to block anterior forearm muscle spasms.

The highest region of muscle spindle abundance should be the optimal target of botulinum toxin A injection to block muscle spasms in rats

Purpose

The effective relief of muscle spasticity requires prompt solutions in rehabilitation medicine. This study aimed to reveal that the highest region of muscle spindle abundance is the optimal target of botulinum toxin A (BTX-A) injections for relieve muscle spasm.

Methods

Sixty adult, male Sprague-Dawley rats with lower limbs spasm caused by stroke after modeling, weighing (200 ± 20) g, were included in this study. The modelrats were divided into four groups: muscle spasm model group (group A), model rats treated with BTX-A injections into the middle of the muscle belly (group B), model rats treated with BTX-A injections into the center of the intramuscular nerve-dense region (INDR) (group C), and model rats treated with BTX-A injection into the center of the highest region of muscle spindle abundance (HRMSA) (group D). Groups B, C, and D were further divided into two subgroups: the 3rd and 6th days after BTX-A injection. The rats in each group were assigned modified Ashworth scale scores (MAS), and the changes in gastrocnemius muscle tone, wet muscle weight, and cross-sectional area of muscle fiber were detected.

Results

Muscle spindle abundance was the highest in the upper part of the INDR. Group B experienced no significant changes in MAS, muscle tone, wet muscle weight, or cross-sectional area of the muscle fiber. Conversely, groups C and D experienced a decrease in these indicators. Group C experienced the most significant decrease in wet muscle weight and cross-sectional area of muscle fibers. Group D experienced the most notable decrease in MAS and muscle tone. There were no significant differences in the indicators between the 3rd and 6th days after BTX-A injections in group B and there were significant differences in the improvement in the indicators between the two subgroups in groups C and D, with group D experiencing more notable intersubgroup differences.

Conclusion

The efficacy of BTX-A injections into the HRMSA is significantly superior to that of conventional BTX-A injections into the middle of the belly muscle or the INDR in the treatment of muscle spasms. Hence, HRMSA should be the optimal target of BTX-A to relieve muscle spasms.