A new technique for subscapularis muscle needle insertion

To investigate a new technique for needle insertion into the subscapularis muscle for botulinum toxin injection, nerve block with phenol, and electromyography.

A new technique, which we have termed the inferior approach, was delineated by cadaver study. In the first step of the study, the thickest part of the subscapularis muscle and the route for the accurate course of the needle were determined by an anatomist on eight cadavers (16 sides). In the second step, using this technique, a physician attempted to inject India ink into the thickest part of the muscle on a separate 12 cadavers (24 sides). The anatomist then examined the accumulated ink by careful dissection of the involved muscle.

The thickest part was determined to be at the lateral half of the muscle. With the exception of two muscles, all the cadavers were successfully injected using the defined route. If the route and injection sites are correct, there is no risk of injecting any muscle in that anatomic region other than the subscapularis. Furthermore, there were no neurovascular structures identified at risk in the area using the inferior approach.

This new technique, termed the inferior approach, is both easy and anatomically safe: it did not involve any risk of damage to any major artery, vein, or nerve.