a. **Femoral triangle block**:

The femoral triangle (FT) is a subfascial space in the upper third of the thigh bounded by the inguinal ligament (base), medial

#### **Figure 9.**

*Sonoanatomy of subsartorial regions.*

*A: Distal femoral triangle, B: Apex of the femoral triangle, C: Proximal adductor canal, D: Mid-adductor canal, E: Distal adductor canal.*

*(STM: Sartorius muscle, ALM: Adductor longus muscle, VMM: Vastus medialis muscle, AMM: Adductor magnus muscle, SN: Saphenous nerve, NVM: Nerve to vastus medialis, FA: Femoral artery, FV: Femoral vein, DGA: Descending genicular artery, Yellow color: Nerves, Red color: Artery, Blue color: Vein, Brown color: Muscles).*

> border of the adductor longus muscle (medial border), and the medial border of the sartorius muscle (lateral border). Femoral triangle block can be given at the distal-most part of FT, just (1–2 cm) proximal to the apex of FT. Sonoanatomy of this location includes posteromedial adductor longus muscle (ALM), anterolateral vastus medialis muscle (VMM), and medial sartorius muscle (STM). The saphenous nerve (SN) and nerve to vastus medialis (NVM) appear as hyperechoic structure lying lateral to the femoral artery (FA) in the fascial plane between STM and VMM. This analgesic block requires diluted (low concentration)

local anesthetic solution with the volume of 10-20 ml. A higher volume (more than 40 ml) or higher concentrated LA may cause proximal spread and include the femoral nerve and its branches, causing unwanted motor weakness. The drug injected into the distal FT spreads distally above and below the vasoadductor membrane (VAM) in the adductor canal region [39, 40]. Due to drug spread between STM and VAM, the subsartorial plexus also gets blocked, providing an additional and required analgesic coverage. The FT block mainly addresses anterior knee pain.
