Postoperative Complications Following Prepectoral Versus Subpectoral Tissue Expander Placement in Immediate Breast Reconstruction: A Retrospective Study from Japan

Background: Prepectoral implant placement has become a widely adopted alternative to subpectoral reconstruction in implant-based breast surgery, offering reduced postoperative pain and improved aesthetic outcomes. However, in Japan, prepectoral placement of silicone breast implants (SBIs) remains unapproved, and its clinical safety has not been well established. Methods: We conducted a retrospective review of 176 patients (187 breasts) who underwent immediate two-stage breast reconstruction with tissue expander (TE) placement between January 2023 and December 2024. Patients were categorized into prepectoral (128 patients, 135 breasts) and subpectoral (48 patients, 52 breasts) groups. Postoperative complications including infection, seroma, and TE exposure were compared. Univariate and multivariate logistic regression analyses were performed to identify risk factors. Results: Infection unrelated to necrosis was more frequent in the prepectoral group (13.3% vs. 2.2%, p = 0.03), with 14 of 17 cases requiring invasive treatment and 10 leading to TE removal or unplanned autologous reconstruction. Seroma occurred in 15.6% of prepectoral cases versus 1.9% of subpectoral (p = 0.01), and TE exposure occurred only in the prepectoral group (4.6%). Multivariate analysis identified prepectoral placement and a final fill ratio <0.6 as independent predictors of infection. Prepectoral placement was also the sole predictor for seroma. Conclusions: Prepectoral TE placement in Japanese patients was associated with increased risks of infection, seroma, and TE exposure compared to subpectoral placement. These findings suggest the need for careful patient selection and surgical planning in the context of Japanese clinical practice, where prepectoral SBI use is not yet established.