Fascial Ultrasound-Guided Injection: Where Do We Really Inject?

Background: The relationship between human anatomy on ultrasonography (US) and dissection is unclear.Therefore, we investigated the precise location of a solution injected into eight legs from five fresh-frozen specimens between the fascial layers of two aponeurotic fascial (APF) regions using US. Methods: The US-guided injection target points were the fascial lata-distal, crural fascia-proximal, and crural fascia-distal. The operator searched the optimal visualization area of two close fascial layers of the two APF regions; 2.5 mL of 0.9% saline was injected through US guidance. The layers with the solution were categorized as above the APF (between the superficial fascia and APF), intra-APF, between the APF and epimysium (EPI), or intra-muscle (under the EPI). Results: A small amount of solution was identified within the intra-APF region, whereas a substantial amount was observed above the APF, between the APF and EPI, and intramuscularly. Regarding the fascia lata-distal and crural fascia-distal, a substantial volume of solution was observed between the APF and EPI in all cases. For the crural fascia-proximal, the solution was observed above the APF in 25% of cases and intramuscularly in 75% of cases. Conclusions: Solution distribution may be associated with whether the muscle fibers are directly inserted into the APF and the absence of EPI in each area.