Evaluation of inguinal sonoanatomy regarding pericapsular nerve group (PENG) block in children: the relation of femoral artery, femoral nerve, lateral femoral cutaneous nerve and iliopsoas notch

BackgroundPericapsular nerve group (PENG) block is a novel technique that provides analgesia in hip surgeries while preserving motor function. This study aimed to identify developmental differences and variations regarding PENG block sonoanatomy in the inguinal region in children.MethodsA total of 150 children between 28 days and 18 years were included in this prospective, observational, descriptive study. The participants were divided into six groups according to growth and development periods. Ultrasonographic measurements representing block depth, needle length, and the vicinity of femoral nerve (FN) and femoral artery (FA) to the block area were collected.ResultsBlock depth: 16.2 +/- 4.0 mm in infants (28 days-12 months); 33.5 +/- 6.1 mm in adolescents (145-215 months). Needle length: 24.2 +/- 5.9 mm in infants; 39.3 +/- 6.6 mm in adolescents. The distance of FA to the block area: 4.4 +/- 2.0 mm in infants; 11.6 +/- 5.7 mm in adolescents. The distance of FN to the block area: 0.7 +/- 0.8 mm in infants; 2.9 +/- 4.0 mm in adolescents. FN-FA distance: 2.2 +/- 1.4 mm in infants; 3.8 +/- 1.8 mm in adolescents. In 49/150 (32.7%) cases the FN overlapped the perpendicular line between iliopsoas notch and skin. The lateral femoral cutaneous nerve (LFCN) was involved in the ultrasound frame in 11/50 (22%) children under the age of three.ConclusionsEspecially in children under three years of age, LFCN should be visualized during the pre-block preparation phase. The out-of-plane approach is not recommended in the PENG block due to the FN's alignment on the path of a vertical needle trace.Trial registrationNCT04860479.