Examination of skin and subcutaneous fat tissue thickness in the gluteal region: Adequacy of needle length in intragluteal injection

The effectiveness of intramuscular (IM) injection depends on the direct administration of the medication into the muscle tissue. However, increased subcutaneous fat thickness may result in failure of IM injections performed with standard needle lengths. In such cases, treatment efficacy decreases, and the risk of complications increases. The aim of this study was to determine, using lower abdominal and pelvic computed tomography (CT) images, the thickness of the skin and subcutaneous fat tissue that the needle must traverse to reach the muscle in the gluteal region where IM injections are administered. This retrospective study included 200 individuals (98 females and 102 males). In both dorsogluteal and ventrogluteal regions, the thicknesses of the skin, subcutaneous fat tissue, and total tissue (skin + subcutaneous fat) were measured bilaterally. Body mass index (BMI) was categorized into three groups: individuals with a BMI of 18.5–24.9 were classified as normal weight (Group 1), those with a BMI of 25–29.9 as overweight (Group 2), and those with a BMI of ≥30 as obese (Group 3). The distribution according to BMI was analyzed. In females and individuals with higher BMI, subcutaneous fat thickness in the dorsogluteal region was found to be greater than in the ventrogluteal region. For ventrogluteal IM injections, the needle reached the target muscle in 30.6% of females and 81.4% of males; whereas in the dorsogluteal region, this rate was 5.1% in females and 47.1% in males. The study demonstrated that there was a statistically significant difference between the dorsogluteal and ventrogluteal regions in terms of subcutaneous fat thickness and the rate of reaching the muscle during IM injection. The results are expected to contribute to determining the appropriate needle length for IM injections administered to adult individuals.