‘Inverse Double Bubble’ sign for an effective adductor canal block: a novel approach for the ultrasound confirmation of being on the right site

In recent years, the ultrasound-guided adductor canal block (US-ACB) has increasingly become a point of reference for postoperative knee analgesia, especially after total knee arthroplasty (TKA).[1][1] Pain following TKA is often severe and may compromise patients’ rehabilitation and functional