Comparison of Gluteal Muscle Intramuscular Injection Sites of Japanese Healthy Subjects: Considerations for Optimal Insertion of Injection Needle Length

Long Acting Injectable (LAI) medications for patients with schizophrenia is commonly administered to relieve their symptoms. Through shared decision-making and clinical evidence-based, psychiatrists should systematically offer LAIs to all patients requiring long-term antipsychotic treatment as a first-line treatment. Gluteal intramuscular (IM) injection requires accurate insertion of needles into the specific muscle area, often the outer upper quadrant of the buttocks, in order to achieve the required blood concentration. The purposes of this study were to compare the “Distance from the Epidermis to the Under-Fascia (DEUF)” and “Distance from the Epidermis to the Iliac Bone (DEB)” of the buttocks IM injection sites at the dorsogluteal and ventrogluteal sites among healthy Japanese volunteer subjects, and to identify the optimal insertion injection needle length. The DEUF and DEB at the gluteal regions were measured by ultrasonography. Welch’s one-way analysis of variance was used to compare the DEUF and the DEB at the gluteal IM injection regions. There was no statistically significant difference observed between the right and left mean values of DEUF for Hochstetter and Clark’s point at the ventrogluteal sites, and the Four and Three-way split or Double Cross point at the dorsogluteal sites. However in the DEB, the Hochstetter’s point (P < 0.01) at ventrogluteal site on the right side, and Clark’s point (P < 0.05) were significantly shorter than the Double Cross point at dorsogluteal sites (F = 4.38). The left buttocks Hochstetter’s point was significantly shorter than the Double Cross point (F = 4.38, P < 0.01). These results, however, did not establish a statistically significant difference in the DEUF among injection sites. It was considered that the difference in the DEB depended on muscle volume and thickness in the gluteal injection sites.

Appropriate Needle Lengths Determined Using Ultrasonic Echograms for Intramuscular Injections in Japanese Infants

Adjuvanted vaccines are recommended for administration through an intramuscular route. The Centers for Disease Control and Prevention (CDC) has recommended the anterolateral thigh using a 22 - 25-G 25-mm (1 inch) needle for infants, injected at a 90° into the skin surface, and using a 16 mm (5/8 inch) for newborns. Appropriate needle lengths may differ depending on racial backgrounds. In the present study, the thickness of the epidermis and lengths from the skin surface to the muscle fascia and bone were measured using ultrasonic echograms in order to determine suitable needle lengths for Japanese infants aged 2, 3, 4, 5, 6, and 12 - 15 months old. The thickness of the epidermis was 1.44 - 1.54 mm (95% CI), and the lengths from the skin surface to the muscle fascia and bone were 11.52 - 12.28 mm (95% CI), and 25.66 - 26.93 mm (95% CI), respectively, at the anterolateral thigh. At the center of the deltoid muscle, skin thickness was similar to that at the thigh, furthermore the lengths from the skin surface to the muscle fascia and bone were 8.49 - 9.10 mm (95% CI), and 17.38 - 18.31 mm (95% CI), respectively. The lengths from the skin surface to the muscle fascia and bone were 1 - 2 mm shorter in 2-month-old infants than those in older generations. Therefore, the appropriate needle length for intramuscular injections in Japanese infants was 16 mm (5/8 inch) at any age and sites, and with 25 mm (1 inch) needles at a 90° angle being associated with the risk of over-penetration.