Background and objectives There is still no consensus on the analgesic range and mechanisms of action of modified thoracoabdominal nerve block through perichondrial approach (M-TAPA). This cadaveric study aimed to determine the spread of an injectate following simulated M-TAPA.

Methods Simulated M-TAPA injections (n=8) were administered on both sides of soft embalmed Thiel cadavers with 25 mL of a saline-soluble dye. Anatomic dissection was performed to document staining (deeply, faintly, or not stained) of the anterior cutaneous branches of the thoracoabdominal nerves and determine the extent of the injectate spread of the dye to the intercostal space in the thoracic cage following a simulated M-TAPA.

Results The median (IQR) dermatome of the stained segmental nerve was T10 (T8–T11) and the median (IQR) number of stained segmental nerves was 3 (4–2). The T9, T10 and T11 segmental nerves were stained in 75%, 100% and 62.5% of simulated M-TAPA, respectively. Conversely, the T8 segmental nerve was stained in only 25% of simulated M-TAPA. No injectate spread of dye to the intercostal space in the thoracic cage was observed in eight simulated injections of M-TAPA.

Conclusion Our findings suggest that M-TAPA most likely involves the T9, T10 and T11 segmental nerves and that the local anesthetic may not spread to the intercostal space in the thoracic cage in M-TAPA. Further studies are required to confirm the precise mechanism of action and efficacy of M-TAPA in a large sample of human participants.