LAUSR

the field of anesthesia. While several novel plane blocks have been described, cadaveric studies on the spread of novel blocks are important for determining appropriate applications [1]. Recently, Tulgar et al. [2] defined the thoracoabdominal nerve block using a perichondral approach (TAPA). They reported that local anesthetic (LA) administered on the upper and lower aspect of the 9th through the 10th costal cartilages would block both the anterior and lateral cutaneous branches, thus providing abdominal analgesia. After describing the TAPA, the authors also redefined the approach, naming it the modified TAPA (M-TAPA). They reported that administering LA only to the lower surface of the costal cartilage would provide successful analgesia similar to that provided by the TAPA [3]. In the literature, there are some case reports and observational studies on the TAPA and M-TAPA [2,3]; however, to the best of our knowledge, no reliable cadaveric investigation has demonstrated the spread of these blocks. Therefore, in this cadaveric investigation, we aimed to evaluate the areas of spread associated with the TAPA and M-TAPA. This study was approved by the Istanbul Medipol University Ethics and Research Committee (Decision No. 36, 06.01.2022). One fresh human male cadaver was obtained from Istanbul Medipol University. Injections were performed by two investigators with 10 and 20 years of experienced in administering regional anesthesia. With the cadaver in the supine position, the M-TAPA was performed on the right side, and the TAPA was performed on the left side. The blocks were performed under ultrasound guidance using a linear transducer. The transducer was placed at the costochondral angle in the sagittal view and then advanced to view the lower side of the chondrium. For the TAPA, 20 ml of 0.25% methylene blue dye was injected into both the upper and lower sides of the chondrium (40 ml total). For the M-TAPA, 40 ml of 0.25% methylene blue dye was injected into the lower side of the chondrium. An anatomical dissection was performed 30 min after the procedure. For both the TAPA and M-TAPA, the dye had spread over the lower surface of the upper part of the rectus abdominis and over the thoracoabdominal nerve on both sides. The lower surface of the external abdominal oblique muscle (EAOM) was completely stained with the dye (over the 8th, 9th, and 10th ribs), and so were the upper and lower surfaces of the internal abdominal oblique muscle (IAOM). Additionally, the dye had spread over the upper surface of the costal margin and from T4 to T11–T12 on both sides. However, the dye spread over the transverse abdominis muscle (TAM) to a greater degree with the M-TAPA compared with the TAPA (limited to the upper part of the muscle) (Figs. 1A and 1B). Received: March 1, 2022 Revised: March 28, 2022 (1st); April 13, 2022 (2nd); April 20, 2022 (3rd) Accepted: April 22, 2022