Objectives: Ultrasound-guided puncture is indispensable for the injection of local anesthetic in the interfascial space, the space between 2 muscle fasciae. Interfascial infiltration or block may be useful in treating myofascial pain in the trapezius muscle.
Methods: (1) In 5 cadavers, we studied the diffusion of a physiological saline and latex solution in the interfascial space of the upper muscles of the back, and performed a histological study of the fasciae. (2) We performed an interfascial block in 25 patients with myofascial pain in the trapezius muscle. Depending on the trigger point location, the block was performed between the trapezius and the levator scapulae or between the trapezius and the rhomboideus major.
Results: In all cadavers, anatomical dissection showed the latex in the interfascial space. The histological study confirmed the presence of nerve structures in the fasciae and in the interfascial space itself. Pain was assessed in all patients on a visual analog scale (VAS) before and after the injection (at rest and in motion). Preinjection: mean VAS 6.4 (at rest) and 7.6 (in motion). Postinjection: mean VAS 1 (at rest) and 1.6 (in motion).
Discussion: The anatomical, histological, and ultrasound findings in the cadaver study confirmed the diffusion of the solution in the interfascial space. Study in patients confirms that the interfascial block in the back musculature can be as effective as in the abdominal musculature. The presence of nerve structures in this space, confirmed by the histological study, seems to explain the pain relief reported by the patients with this interfascial technique.