A Surface Landmark-Based Scanning Algorithm for Selected Ultrasound-Guided Nerve Blocks of the Upper and Lower Limb in Orthopedic Surgery: A Narrative Review

Performing an ultrasound-guided nerve block requires two cognitively distinct phases: image acquisition, in which the operator positions the transducer and identifies the target anatomy, and image maintenance, in which that image is preserved during needle advancement. Without a pre-formed expectation, scanning can become an open-ended search. This review proposes structuring image acquisition as a confirmatory task by linking a defined surface landmark to an expected sonographic target through a defined scanning path. The present article consolidates the correspondence between surface landmarks and sonographic targets, for a selected set of upper and lower limb nerve blocks used in orthopedic surgery, into a single landmark-based scanning algorithm. Four steps (anchor, place, trace, and confirm) structure each block: a surface anchor defines the starting reference; an initial transducer position is derived from it; a directional search vector defines the trajectory of probe displacement; and a sonographic endpoint confirms correct placement and marks the transition to the needling phase. Anchors are described for the cervical plexus and brachial plexus blocks of the upper limb, and for the femoral nerve, fascia iliaca, lateral femoral cutaneous nerve, iliopsoas plane, pericapsular nerve group, obturator nerve, femoral triangle/adductor canal, popliteal sciatic nerve, and saphenous nerve blocks of the lower limb. A common graphic notation renders every block as a single instance of this sequence, making the set directly comparable. Whether this structure reduces cognitive demand, or renders the spatial reasoning of experienced operators transferable, is a hypothesis that requires prospective validation.