I.
Injections through intramuscular routes are given in areas where muscles are thick and with extensive blood supply. Injections may target the gluteus medius muscle of the buttock, lateral side of the thigh in the midportion of the vastus lateralis muscle, and the deltoid muscle of the shoulder. For neonates, the recommended site for intramuscular injections is in the anterolateral area of the thigh, targeting the vastus lateralis muscle. In order to locate this muscle, the area below the greater trochanter and above the lateral femoral condyle or knee joint must be palpated. As you palpate, divide the muscle into thirds and locate the middle third of the muscle, lateral to the thigh’s midpoint. This muscle’s origin, insertion, and action is as follows;
Origin: Greater trochanter and linea aspera of femur.
Insertion: Patella via quadriceps tendon and then tibial tuberosity via patellar ligament.
Action: All four heads extend leg at knee joint; rectus femoris muscle acting alone also flexes thigh at hip joint.
II.
In the case of the baby’s 65-year-old grandfather, the client may receive the vaccine through the deltoid muscle. To locate this muscle, the acromion should be palpated. An inverted triangle may be visualized and its center will be identified as the injection site, 3-5cms below the acromion. This muscle’s origin, insertion, and action is as follows;
Origin: Acromial extremity of clavicle (anterior fibers), acromion of scapula (lateral fibers), and spine of scapula (posterior fibers).
Insertion: Deltoid tuberosity of humerus.
Action: Lateral fibers abduct arm at shoulder joint; anterior fibers flex and medially rotate arm at shoulder joint; posterior fibers extend and laterally rotate arm at shoulder joint.
SOURCES:
Clinical Guides (Nursing) - Intramuscular Injections. (n.d.). The Royal Children's Hospital Melbourne. https://www.rch.org.au/rchcpg/hospital_clinical_guideline_index/Intramuscular_Injections/
Tortora, G. J., & Derrickson, B. (2017). Principles of Anatomy & Physiology. http://ndl.ethernet.edu.et/bitstream/123456789/1717/1/36%2c2012.pdf.pdf