Influence of gender, BMI and body shape on theoretical injection outcome at the ventrogluteal and dorsogluteal sites

Aims and objectives This study aimed to determine the influences of gender, BMI and observed body shape on subcutaneous fat and muscle thicknesses, and theoretical injection outcome, at the ventrogluteal and dorsogluteal intramuscular injection sites. Background Debate continues as to whether the dorsogluteal or ventrogluteal injection site is more reliable for a successful intramuscular injection outcome. Subcutaneous fat and muscle thicknesses at the injection site are direct determinants of intramuscular injection outcome. BMI and observed body shape influence gluteal subcutaneous fat and muscle thicknesses, and therefore injection outcome, with potentially distinct effects at the ventrogluteal and dorsogluteal sites. Design This was a cross‐sectional study. Methods Demographic data were collected, and subcutaneous fat and muscle thicknesses were quantified bilaterally at the dorsogluteal and ventrogluteal injection sites using ultrasound, for 145 participants (57% female). Results Subcutaneous fat and muscle were significantly thicker at the dorsogluteal than the ventrogluteal site, and 75% and 86% of participants would receive a successful intramuscular injection at these sites, respectively. There were significant effects of gender, BMI and observed body shape on subcutaneous fat thickness and theoretical injection outcome at both sites. Females, obese individuals and endomorph individuals had thicker subcutaneous fat and were more likely to have a subcutaneous injection outcome. Conclusions Gender, BMI and observed body shape could be used to guide site and needle length selection when administering gluteal intramuscular injections to increase the likelihood of a successful intramuscular injection outcome. Relevance to clinical practice Both gluteal injection sites should be avoided in obese individuals and endomorph individuals. An intramuscular injection will be successful: using a 32‐mm needle at the ventrogluteal site for all males and normal‐weight females and using a 38‐mm needle for all females at the ventrogluteal site, and for all males and at least 98% of females at the dorsogluteal site.