Although the physical safety of intramuscular injections at the deltoid and ventrogluteal sites has been studied, the anatomical connection between intramuscular injection sites in the thigh and major blood arteries and nerves is unknown. The goal of this study was to compare intramuscular injection sites in the rectus femoris and vastus lateralis to those in the deltoid and ventrogluteal muscles, and to find safe intramuscular injection sites in the thigh. Twenty-seven young adult participants were recruited, and the thicknesses of subcutaneous tissue and muscle, as well as the number of blood vessels present, were measured by ultrasonic technology at two places on the deltoid, ventrogluteal, and thigh. The right thighs of 24 cadavers were utilized, and the muscle thickness, number of blood vessels or nerves present, and distance between each investigated location and major blood vessels or nerves in the rectus femoris and vastus lateralis were all measured. In young adults, a large blood artery was discovered in the center of the rectus femoris. The descending branch of the lateral circumflex femoral artery and the muscle branch of the femoral nerves to the vastus lateralis were observed in cadavers at the middle point, distal two-thirds point, and middle point between the middle and distal two-thirds points of the rectus femoris, but not at the vastus lateralis’s middle point.

Due to the minimal danger of vascular or nerve injury, the center of the vastus lateralis is a suitable location for intramuscular injections. The current findings support excellent practices for intramuscular injection site selection.