Anatomic Localization of Motor Points for the Neuromuscular Blockade of Hand Intrinsic Muscles Involved in Thumb-in-Palm

Nerve entry points - The anatomy beneath trigger points

INTRODUCTION

Myofascial trigger points (MTrPs) have been the subject of considerable scientific research for almost forty years. In their seminal paper, Travell and Simons described a model based on the presence of highly irritable, palpable nodules within taut bands of muscle. Since then, a significant number of studies have increased our understanding of the phenomenon, which has, in turn, resulted in refutation of the original model. Alternative models have explained certain properties of MTrP but fail to provide an explanation of their spatial distribution. The aim of this paper was to propose a hypothesis connecting MTrPs and distinct points along the course of the nerve called nerve entry points (NEPs). A literature review was performed in order to identify studies to support hypothesis development.

METHODS

Literature search of digital databases.

RESULTS

A total of 4631 abstracts were screened; 72 were selected for further review. Four articles made a direct connection between MTrPs and NEPs. Another fifteen articles provided high-quality data regarding the distribution of NEPs, thus strengthening the hypothesis.

CONCLUSIONS

There is sufficient evidence to hypothesise that NEPs are the anatomical basis for MTrPs. This presented hypothesis addresses one of the crucial issues in diagnosing trigger points, which is the lack of repeatable and reliable diagnostic criteria. By connecting subjective phenomenon of trigger points with objective anatomy, this paper provides a novel and practical foundation for identifying and treating pain conditions associated with MTrPs.

Safe Needle Insertion Locations for Motor Point Injection of the Triceps Brachii Muscle: A Pilot Cadaveric and Ultrasonography Study

Objective

To determine the location of the motor endplate zones (MoEPs) for the three heads of the triceps brachii muscles during cadaveric dissection and estimate the safe injection zone using ultrasonography.

Methods

We studied 12 upper limbs of 6 fresh cadavers obtained from body donations to the medical school anatomy institution in Seoul, Korea. The locations of MoEPs were expressed as the percentage ratio of the vertical distance from the posterior acromion angle to the midpoint of the olecranon process. By using the same reference line as that used for cadaveric dissection, the safe injection zone away from the neurovascular bundle was identified in 6 healthy volunteers via ultrasonography. We identified the neurovascular bundle and its location with respect to the distal end of the humerus and measured its depth from the skin surface.

Results

The MoEPs for the long, lateral, and medial heads were located at a median of 43.8%, 54.8%, and 60.4% of the length of the reference line in cadaver dissection. The safe injection zone of the medial head MoEPs corresponded to a depth of approximately 3.5 cm from the skin surface and 1.4 cm away from the humerus, as determined by sonography.

Conclusion

Correct identification of the motor points for each head of the triceps brachii would increase the precision and efficacy of motor point injections to manage elbow extensor spasticity.

Determination of injection site in flexor digitorum longus for effective and safe botulinum toxin injection

OBJECTIVE

To determine the optimal injection site in the flexor digitorum longus (FDL) muscle for effective botulinum toxin injection.

METHODS

Fourteen specimens from eight adult Korean cadavers were used in this study. The most proximal medial point of the tibia plateau was defined as the proximal reference point; the most distal tip of the medial malleolus was defined as the distal reference point. The distance of a line connecting the proximal and distal reference points was defined as the reference length. The X-coordinate was the distance from the proximal reference point to the intramuscular motor endpoint (IME), or motor entry point (MEP) on the reference line, and the Y-coordinate was the distance from the nearest point from MEP on the medial border of the tibia to the MEP. IME and MEP distances from the proximal reference point were evaluated using the raw value and the X-coordinate to reference length ratio was determined as a percentage.

RESULTS

The majority of IMEs were located within 30%-60% of the reference length from the proximal reference point. The majority of the MEPs were located within 40%-60% of the reference length from the proximal reference point.

CONCLUSION

We recommend the anatomical site for a botulinum toxin injection in the FDL to be within a region 30%-60% of the reference length from the proximal reference point.

Does botulinum toxin injection site determine outcome in post-stroke plantarflexion spasticity? Comparison study of two injection sites in the gastrocnemius muscle: a randomized double-blind controlled trial

OBJECTIVE

To determine if botulinum toxin type A injection at the proximal 2/10 and 3/10 of calf length, where the intramuscular nerve endings of the gastrocnemius muscle are densely distributed, is more efficacious in controlling plantarflexion spasticity than injection at distant sites within the same muscle.

DESIGN

A double-blind randomized controlled trial.

SETTTING

Two rehabilitation centres.

SUBJECTS

Forty stroke patients were randomly allocated to two groups. Group A received injection at the proximal 2/10 and 3/10 of calf length, group B at and below the midbelly of the muscle. Both groups received 200 IU of botulinum toxin A and were followed up to eight weeks.

MAIN MEASURES

Primary variables were the surface electromyography values recorded during plantarflexion; secondary variables were the Modified Ashworth Scale, Modified Tardieu Scale, clonus scale, 10-metre walking test, ABILOCO and Functional Ambulation Categories.

RESULTS

At baseline, the median Modified Ashworth Scale was 2.0 (range,1+ -3.0), and there were no significant differences between the two groups in all the parameters, including spasticity. Compared to baseline, no significant differences between the two groups were detected in all the surface electromyography and clinical parameters at week 8 (P > 0.05). Both groups showed significant improvement of spasticity with a median Modified Ashworth Scale of 1+ (range, 0.0-2.0) at eight weeks.

CONCLUSIONS

Botulinum toxin A injection was associated with a significant improvement from baseline to week 8 in both treatment groups, however, no significant difference between the 2 groups was observed, based on the electrophysiological and clinical parameters employed in this study.

Anatomic localization of motor points of wrist flexors

OBJECTIVE

The aim of this study was to determine the location of the motor points and the intramuscular branches of the wrist flexors in relation to bony landmarks.

DESIGN

Sixteen limbs from eight adult cadavers were anatomically dissected. The motor branch points of the flexor carpi radialis and flexor carpi ulnaris muscles and the proximal limit points and the distal limit points in relation to a reference line connecting the medial epicondyle and the pisiform bone or one connecting the medial epicondyle and the base of the second metarcarpal bone were identified.

RESULTS

For the flexor carpi radialis muscles, the motor branch points were located at a distance of 27% ± 6% of the reference line, whereas the proximal limit points and the distal limit points were located at a distance of 21% ± 5% and 37% ± 8% of the reference line. For the flexor carpi ulnaris muscles, the corresponding data were 32% ± 8%, 23% ± 6%, and 43% ± 9%.

CONCLUSIONS

The results may assist in enhancing accuracy when localizing points for neuromuscular blockade of the wrist flexors. The optimal area for flexor carpi radialis muscle injection is at a quarter point and that for flexor carpi ulnaris muscle injection is at one-third point along each reference line from the medial epicondyle.

The study of intramuscular nerve distribution patterns and relative spindle abundance of the thenar and hypothenar muscles in human hand

Background

The intramuscular nerve distribution and relative spindle abundance of the human hand have not been well defined, although this is important in guiding hand surgery.

Methods

Forty human hands were dissected and subjected to modified Sihler’s stain and haematoxylin and eosin stain to investigate intramuscular nerve distribution and relative spindle abundance, respectively.

Results

The flexor pollicis brevis (FPB), adductor pollicis (AP), and abductor digiti minimi (ADM) contain separate nerve compartments. Neural anastomoses were observed in the thenar and hypothenar muscles, including the Y-like, O-like, H-like, and U-like appearance. We found that U-like neural anastomoses may be the characteristic of the opponens muscles. The relative spindle abundance was the greatest in the opponens muscles which may coordinate fine movements.

Conclusion

Except for the two opponens muscles, the rest of the thenar and hypothenar muscles could be used as whole muscle or half-muscle donors for muscle transplant. Our nerve map of the hand offers valuable guidance for hand reconstruction.

Effective zone of botulinum toxin a injections in hallux claw toe syndrome: an anatomical study

INTRODUCTION

The aim of this study was to determine the anatomical location of the motor points of the flexor hallucis longus (FHL) and brevis (FHB) muscles for an effective motor point block.

METHODS

Twenty cadavers were used for this study. For the FHL, we identified the line between the medial and lateral epicondyle of the femur and the line joining the prominent point on the surface of the medial malleolus of the tibia and the lateral malleolus of the fibula. For the FHB, we identified the line between the middle-lowest point of the great toe and the middle-lowest point of the sole of the foot.

RESULTS

The dense area of the motor points was located at 40-70% for the FHL and 50-70% for the FHB.

CONCLUSION

An injection area of 50-60% on the reference line for the FHL and FHB is suggested.

Location of the motor entry point and intramuscular motor point of the tibialis posterior muscle: for effective motor point block

The aim of this study was to elucidate the anatomical location of the motor entry point (MEP) and intramuscular motor point (IMP) of the tibialis posterior muscle for effective motor point block. Thirty-six fresh specimens from 20 adult Korean cadavers (11 males and 9 females) were investigated. The reference line between the most proximal-medial articular margin of the tibia (MPM) at the level of the knee joint and the most distal point of the malleolus of the tibia (MDM) on the surface were identified. The mean length of the reference line was 326.5 ± 27.1 mm. There were 82.5% of the total number of MEPs located at 10-30% and 67.9% of the total IMPs were 10-40% from the MPM. The safety zone for botulinum toxin (BTX) injections on the medial approach was 10-40% from the MPM. In addition, insertion of the needle to a depth of 3.5 cm from the surface of the skin was effective. These results may assist in determining more accurate localization of injection sites.

The effective zone of botulinum toxin A injections in the sternocleidomastoid muscle

PURPOSE

The aim of this study was to document the anatomical landmarks of the motor entry point (MEP) and the intramuscular motor point (IMP) of the sternocleidomastoid (SCM) muscle for effective botulinum toxin injections.

MATERIALS AND METHODS

Thirty-five specimens from 20 adults bodies donated to science were investigated. The reference points were the mastoid process and the most medial point of the clavicle.

RESULTS

The mean length of the reference line was 165.2 ± 12.8 mm. 97.0% of the total number of MEP in this study were located at 20-40 and 85.0% of the total number of the IMP was located at 20-70% from the mastoid process. The intersection with the great auricular nerve was located at 22%, it was 45% for the transverse cervical nerve and 28% for the external jugular vein.

CONCLUSIONS

In clinical practice, the mass in patients with torticollis or cervical dystonia might be formed at the lower part or upper part of the SCM muscle. For a mass in the upper portion of the SCM muscle, the injection area using alcohol, phenol or botulinum toxin was determined to be 20-40%. However, to inject the area at 20-40%, ultrasound guidance is recommended because of the cervical cutaneous nerves and veins. For a mass in the lower portion of the SCM muscle, the injection area of botulinum toxin was 50-70%. These areas can be used with botulinum toxin injections or other agents for motor point blocking in patients with torticollis or cervical dystonia.