Long-term Follow-up of Remnant Capsules After Implant Removal Without Capsulectomy: An Animal Model Study.

BACKGROUND

Breast implantation induces fibrous capsule formation as a natural foreign body response. Although capsule-related complications often require capsulectomy, the need for capsulectomy during implant removal in patients with asymptomatic capsules remains unclear.

OBJECTIVES

In this study, the authors aim to examine the capsule's degradation process over time and identify key cytokines involved in its remodeling.

METHODS

Nine 7-week-old Sprague-Dawley rats received custom 2.25 cm silicone cohesive gel implants subcutaneously on both dorsal sides. Capsule tissues were collected at implant removal (0M) and 3-month (3M) and 6-month (6M) intervals following implant removal without capsulectomy. Tissues were analyzed histologically utilizing hematoxylin and eosin and Masson's trichrome staining. Immunohistochemical staining for matrix metalloproteinase-9 (MMP9), CD31, α-smooth muscle actin (αSMA), Type I collagen (COL1), and CD68 was quantified for comparative analysis.

RESULTS

The 0M group showed robust capsule formation with dense collagen and myofibroblasts. Over time, the capsules thinned (315 µm at 0M, 194.8 µm at 3M, 136.8 µm at 6M; P < .01), became structurally disrupted, and merged with surrounding adipose tissue. Notably, MMP9 and CD31 levels increased significantly, indicating enhanced matrix turnover and vascularization. αSMA and COL1 declined initially before partially rebounding at 6M, whereas CD68 exhibited trends consistent with ongoing remodeling.

CONCLUSIONS

The findings illustrate the natural degradation and remodeling of implant-induced capsules driven by specific cytokines and matrix markers. These insights may inform future guidelines on the necessity of capsulectomy during implant removal.