Multidetector CT assessment of gluteal fat and muscle thickness: implications for safe dorsogluteal intramuscular injections

The dorsogluteal region is commonly used for intramuscular injections. However, variations in the body mass index (BMI), muscle thickness, and subcutaneous gluteal fat can influence both the efficacy and safety of drug delivery. In this retrospective study, we evaluated the thickness of the gluteal fat and muscle at a typical injection site using CT scans from patients who had previously undergone imaging. This study aimed to assess the correlation between muscle thickness, gluteal fat thickness, and BMI using Multidetector computed tomography (MDCT) to determine the suitability of the dorsogluteal region for IM injections. This retrospective, cross-sectional study was performed on 270 adult participants, including 106 males and 164 females aged 19–88. Gluteal fat and muscle thickness were measured using pelvic MDCT scans. Analysis of variance (ANOVA), independent t-tests, and Pearson correlation analyses were performed to examine the correlations between BMI, tissue thickness, and demographic factors. The results revealed a strong positive correlation between the BMI and gluteal fat thickness (r = 0.78, p < 0.001). No sex-based differences were observed in muscle thickness, whereas females had significantly higher fat thickness than males (p < 0.001). The findings suggest that increased BMI levels increase fat thickness in the dorsogluteal region, influencing the depth of IM injections, indicating the need for personalized injection approaches based on anatomical differences. This study demonstrates that high BMI is strongly associated with increased gluteal fat thickness, which may prevent intramuscular injections in the dorsogluteal region from reaching the muscle layer. When injections are deposited into adipose tissue, drug absorption can be compromised, leading to potential complications such as granuloma formation. To ensure efficacy and safety, clinicians should consider alternative injection sites, longer needles, or different administration routes for patients with high BMI and substantial subcutaneous fat. While MDCT provides precise assessment of tissue thickness, ultrasound offers a practical and radiation-free alternative for measuring gluteal fat depth in clinical practice, enabling personalized injection strategies.