Findings and limitations of cadaveric studies in plan A blocks: a narrative review.

Cadaveric studies provide anatomical information unavailable from clinical investigations and have contributed to the development of regional anesthesia techniques. The Plan A framework comprises seven versatile techniques intended for routine clinical practice. However, related cadaveric evidence remains insufficiently synthesized. This narrative review summarizes and critically appraises cadaveric studies of Plan A blocks. A focused literature search identified 54 studies investigating the interscalene brachial plexus block, axillary brachial plexus block, femoral nerve block, adductor canal block, popliteal sciatic nerve block, erector spinae plane block (ESPB), and rectus sheath block. Studies of the six blocks other than ESPB clarified target anatomy, injectate distribution, and technical or safety considerations, but were generally limited by small numbers of studies and uncertain clinical applicability. The ESPB accounted for half of the included studies. These consistently demonstrated extensive craniocaudal spread within the erector spinae fascial plane, whereas anterior spread to the paravertebral space and ventral rami was inconsistent and was not reliably explained by injectate characteristics or volume. Cadaveric models cannot reproduce physiological conditions or establish clinical efficacy, but remain valuable for visualizing injectate spread and investigating anatomical mechanisms. Integration with imaging and clinical studies is required to translate these findings into clinical recommendations.