Breast implant ruptures are a recognized complication of a breast implant. It can be intracapsular, when confined by the surrounding fibrous capsule, or extracapsular, when silicone freely extravasates.
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Pathology
After implantation of a silicone or saline breast implant, a fibrous capsule (scar) forms around the implant shell. Implant ruptures may be intracapsular (~85%) or extracapsular (~15%) 4.
Intracapsular rupture
An intracapsular rupture occurs when the shell of the implant ruptures but the fibrous capsule formed by the breast remains intact. Silicone does not freely extravasate. This makes it difficult to detect on clinical exam or mammography. Intracapsular rupture is best seen on MRI.
Extracapsular rupture
An extracapsular rupture can lead to a change in the implant contour and may be detected on clinical examination or mammography. An extracapsular rupture implies intracapsular rupture as well 3.
Radiographic features
Mammography
Detection of implant ruptures (particularly silicone implant ruptures) are difficult on mammography and detection of intra-capsular silicone ruptures are almost impossible on mammography.
Ultrasound
Ultrasound may demonstrate a "snowstorm appearance" of an extracapsular rupture or the "stepladder sign" of an intracapsular rupture (a normal implant should usually be anechoic). Ultrasound overall performs poorly, with sensitivity and specificity rates ranging between ~59-85% and ~55-79% respectively 7.
Breast MRI
MRI is considered the most sensitive for the detection of implant rupture. Contrast is often not required if the indication is solely for this purpose.
In an intracapsular rupture, the contents of the implant are contained by the fibrous scar, while the shell appears collapsed. When minimally collapsed, it appears as a parallel line to the capsule, termed the "subcapsular line sign". When significantly collapsed, it appears as a group of wavy lines, termed the "linguine sign" 1. The "keyhole sign", "noose sign" or "teardrop sign" is the appearance of silicone on both sides of a radial fold and also suggests an implant rupture 2.
With the use of multi-planar imaging, MRI may also be able to make a distinction between radial folds or actual ruptures.
A gross extracapsular rupture is evident as free silicone, separate from the implant, which has extended beyond the implant capsule into the breast or axilla. Free silicone has an increased signal in STIR sequence without any enhancement in T1 weighted fat-suppressed sequence.
Non-contrast MRI may also be able to distinguish between silicone and saline implants by using silicone or water-only sequences. The "salad oil sign" has also been described in a double lumen implant rupture, where there is mixing of the saline and silicone, although this on its own is non-specific.
Management
Confirmed intra/extracapsular rupture is an indication for surgical removal, to minimize interaction with surrounding tissue and nodal/distal migration of its contents. Newer silicone implants contain cohesive silicone which do not migrate, however, older implants may disseminate widely. Reports of silicone migration as far as the inguinal region exist 11.
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