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

Enhancing Botulinum Toxin Injection Precision: The Efficacy of a Single Cadaveric Ultrasound Training Intervention for Improved Anatomical Localization

Ultrasound guidance can enhance existing landmark-based injection methods, even through a brief and single exposure during a cadaveric training course. A total of twelve participants were enrolled in this training program, comprising nine physical medicine and rehabilitation specialists, one pediatrician, and two physician assistants. For each participant, one upper-limb muscle and one lower-limb muscle were randomly chosen from the preselected muscle group. Subsequently, participants were tasked with injecting both of their chosen cadaveric muscles with 1 mL of acrylic paint using a manual needle palpation technique, relying solely on their knowledge of anatomic landmarks. Participants then underwent a personalized, one-to-one ultrasound teaching session, lasting approximately five minutes, conducted by two highly experienced instructors. Following this instructive phase, participants were tasked with a second round of injections, targeting the same two muscles in the lower and upper limbs. However, this time, the injections were performed using anatomical landmarks and ultrasound guidance. To facilitate differentiation from the initial injections, a distinct color of acrylic paint was employed. When employing the anatomical landmark-based approach, the overall success rate for injections was 67%, with 16 out of 24 targeted muscles accurately injected. With the incorporation of ultrasound guidance, the success rate was 92%, precisely targeting 22 out of the 24 muscles under examination. There was an improvement in injection accuracy achievable through the integration of ultrasound guidance, even with minimal training exposure. Our single cadaveric ultra-sound training program contributes valuable insights to the utilization of ultrasound for anatomy training to help optimize the targeting of BoNT-A.

Distribution of the intramuscular innervation of the triceps brachii: Clinical importance in the treatment of spasticity with botulinum neurotoxin

This study aimed to identify ideal sites for botulinum toxin injection by analyzing the intramuscular nerve patterns of the triceps brachii muscles. A modified Sihler's method was applied to the triceps brachii muscle (15 specimens), with long, medial, and lateral heads. The intramuscular arborization areas of the long, medial, and lateral heads of the triceps brachii muscle were measured as a percentage of the total distance from the midpoint of the olecranon (0%) to the anteroinferior point of the acromion (100%), by dividing the medial and lateral parts based on the line connecting the midpoint of the olecranon and the anteroinferior point of the acromion. Intramuscular arborization patterns were observed at the long head at two medial regions, proximally 30%-50% and distally 60%-70%; medial head of 30%-40%; and lateral head of 30%-60%. These results suggest that the treatment of spasticity of the triceps brachii muscles involves botulinum toxin injections in specific areas. The areas corresponding to the areas of maximum arborization are recommended as the most effective and safe points for botulinum toxin injection.