Resumen

Objectives: To determine the optimal injection volume in autologous breast fat grafting by analyzing the relationship between injected volume and 3-month volume gain, and to identify efficient injection-to-capacity ratios for maximizing outcomes while minimizing fat waste. Introduction: In lean Asian women, limited donor fat and small breast capacity complicate volume planning in fat grafting. Overharvesting leads to unnecessary fat waste, while overinjection may cause fat necrosis, nodules, or distortion due to tissue pressure overload. Despite its clinical importance, objective guidelines for optimal injection volume remain lacking, particularly in low-BMI patients. We aimed to model efficiency and safety using 3D volumetry. Materials / method: Twelve female patients undergoing fat grafting (mostly with the Condense method) were analyzed using 3D volumetric imaging pre-op and at 3 months post-op. Volume efficiency was defined as: (3M volume − pre-op volume) ÷ injected volume. Injection ratio was defined as: injected volume ÷ pre-op breast volume. Quadratic regression and stratified analysis were used to identify optimal injection ranges. Results: Efficiency peaked at an injection ratio of ~1.3. Ratios beyond 1.5 achieved greater volume gain but at diminishing efficiency. No benefit was observed above 1.8. In patients with BMI 18.5–21 and pre-op volume <150 ml, injecting 240–280 ml per side balanced high efficiency and significant volume gain without waste. Conclusion: Modeling the injection-to-capacity ratio enables a balanced approach to maximize volume gain while minimizing risks associated with overinjection, such as fat necrosis or nodularity. In lean Asian patients, a ratio around 1.3 offers high efficiency, while 1.5 serves as a safe upper threshold. While the sample size was limited, these findings offer a foundation for future studies to refine personalized grafting strategies.