Injection-plane allocation and volumetric outcome after autologous breast fat grafting

Objectives: 1.To evaluate the association between injection-plane allocation and postoperative volumetric gain after autologous breast fat grafting. 2.To determine whether superficial allocation is associated with lower retention after adjustment for baseline clinical factors including preoperative breast volume, total injected volume, and BMI. 3.To provide a practical framework for considering plane distribution in surgical planning to optimize volumetric outcome. Introduction: Autologous breast fat grafting is widely performed, yet volumetric retention remains variable and incompletely predictable. Injection-plane allocation—how the graft is distributed across superficial, deep, and intramuscular planes—may influence postoperative outcome, but the relationship between layer distribution and postoperative breast volume has not been adequately characterized. We investigated whether the proportion of graft placed in superficial versus deeper planes was associated with postoperative volumetric gain and retention. Materials / method: We retrospectively analyzed bilateral autologous breast fat grafting cases with postoperative volumetric follow-up at 3 and 6 months. Allocation ratios were calculated for superficial and deeper planes, including intramuscular distribution. Associations between allocation pattern and volumetric outcomes were assessed using correlation analyses. Multivariable models were constructed to evaluate whether superficial allocation remained associated with retention after adjustment for preoperative bilateral breast volume, total injected volume, and body mass index. Results: At 3 months, higher superficial allocation was associated with lower volumetric gain (rho=-0.517, p<0.001), whereas deeper allocation showed positive associations (deep-plane rho=0.418, p=0.001; intramuscular rho=0.455, p<0.001). Similar patterns were observed at 6 months (superficial rho=-0.508, p<0.001; deep-plane rho=0.498, p<0.001; intramuscular rho=0.520, p<0.001). In multivariable analyses, higher superficial allocation remained independently associated with lower retention at 3 months (p=0.008) and 6 months (p=0.006). Conclusion: Injection-plane allocation was associated with postoperative volumetric outcome after autologous breast fat grafting. Greater superficial allocation was associated with lower gain and lower retention, whereas deeper allocation, including intramuscular distribution, showed more favorable volumetric associations across both early and intermediate follow-up. Plane distribution may therefore represent a clinically relevant planning factor when optimizing volumetric outcome and should be considered during preoperative surgical planning.