An increasing number of patients have breast implants for cosmetic augmentation of the breast, reconstruction after mastectomy or correction of congenital malformations [1]. Implant rupture is the main cause of implant removal. Implant rupture can have various causes, but most ruptures have no obvious traumatic origin and sometimes occur in asymptomatic patients. Most implant ruptures occur 10 to 15 years after implantation [2]. The incidence of rupture increases with implant age; the average incidence is approximately 2 implant ruptures per 100 implant-years, with an estimated probability of being intact after 5 and 10 years of implantation of 98% and 83–85%, respectively [3–6].
Clinical diagnosis is difficult, being based solely on nonspecific findings such as palpable nodules, asymmetry or tenderness [7]. Free silicone from ruptured implants has in rare cases spread to distant body regions, giving rise to symptoms. If implant rupture is accompanied by loss of the shape of the breast, the diagnosis of breast implant rupture at physical examination is feasible. However, clinical evaluation may fail to detect breast implant rupture that occurs over time without loss of breast volume and misshapenness. Breast pain on the clinical examination of implants is a strong predictor of rupture, but the absence of pain does not exclude rupture [3]. According to Tark et al. [8], the most common symptom in breast implant rupture is contour deformity (44%), followed by displacements (20%), mass formations (17%), pain (13%) and inflammation (3%). However, physical examination fails to diagnose implant rupture in more than 50% of cases.
Magnetic resonance imaging (MRI), mammography, ultrasonography (US) and exceptionally computed tomography (CT) have all been used to diagnose silicone breast implant rupture. Each technique has specific strengths and weaknesses that may make a particular technique the study of choice for an individual patient [9]. Familiarity with both the typical and atypical findings for implants is essential to enable abnormalities to be detected. Many factors can influence which imaging technique should be used to evaluate the integrity of silicone breast implants in a particular patient. These factors include the cost of the examination, the availability of an imaging technique, the expertise of the radiologist performing and interpreting the study, and potential contraindications or limitations of a patient that would prevent the use of a specific imaging technique [9].
Furthermore, knowing which implant the patient has can help determine the type of imaging findings to expect in case of rupture. Each type of silicone gel-filled implant has slightly different imaging findings for implant failure related to the manufacturing process and viscosity of the silicone gel.
Breast reconstruction may involve the insertion of various types of implant or the modelling of autologous myocutaneous flaps. According to the literature, breast implants can be categorised into five implant generations reflecting product development over time. The recent generations of silicone gel implants have a cohesive viscous silicone gel. As a result of this feature, these implants will rarely have a totally collapsed implant shell, differing from the older generations. Moreover, most of them have gel leakage and silicone migration. The third and fourth implant generations offered models of breast implants with textured or uniformly smooth surfaces (Fig. 1), and it seems that capsular contracture rarely occurs in women with recent generations of breast implants. All implants in this article are silicone breast implants including single-lumen implants (the majority) and less commonly double-lumen implants (Fig. 5). Single-lumen implants have a single lumen of silicone gel delimited by a multilayer shell, while double-lumen implants have a fixed amount of saline and silicone within them, or a fixed outer lumen usually filled with silicone and an inner lumen that can be expanded, as necessary, with saline (inverse double-lumen) [10].
Finally, another surgical breast reconstruction technique uses autologous myocutaneous flaps. Flaps are most commonly either transverse rectus abdominis musculocutaneous (TRAM) flaps or latissimus dorsi flaps, and are used to reform the breast either alone or in conjunction with an implant. Another alternative more rarely encountered in clinical practice is direct silicone gel injection in the breast.
Breast implants may be placed in a subglandular (anterior to the pectoralis major muscle) or subpectoral (posterior to the pectoralis major muscle) location (Fig. 2).
Before implant insertion, especially in oncoplastic breast reconstruction, a tissue expander (Fig. 1) is usually placed in the mastectomy site to stretch the remaining skin in preparation for the placement of a permanent implant later. The expander is like an inflatable breast implant that is inserted into a pocket under the skin and muscle of the chest. The expander is usually placed in its collapsed form at the time of mastectomy and then, after surgery, fluid is introduced into the tissue expander to slowly inflate it. It is important to realise that, as their function is to expand, they might not be fully inflated and thus may appear to have multiple folds or wrinkles on the surface. This should not be interpreted as rupture [10]. Depending on the type of expander, the fluid is either introduced directly into the expander (magnetic marker) or is injected into a distant port. This process continues for several weeks until the tissue expander is filled to an optimal volume, when a permanent breast implant can be inserted.
Notably, some kind of breast tissue expanders should be considered a contraindication to MRI because of the magnetic marker of the filling valve: expander manufacturers list possible consequences such as overheating, possible expander displacement, and possible reduction of magnetisation of the marker [11].
Early postoperative complications of breast augmentation include hematoma and infection [12]. After placement, a thin fibrous capsule (scar tissue) normally forms around the prosthesis. This occurs around all silicone implants to some degree; however, pronounced fibrous capsule formation causes discomfort and alters the shape of the breast. This capsular contracture is one of the most common complications of implant insertion. Changes owing to marked fibrous capsule contraction often cannot be appreciated on imaging, and clinical examination is the best way to diagnose this condition [10].
Magnetic resonance imaging (MRI) is the most accurate technique in the evaluation of implant integrity. Its sensitivity for rupture is between 80% and 90%, and its specificity is between 90% and 97% [3, 5–16] (Fig. 3).
MRI may be used to exclude a ruptured prosthesis, and it may aid explantation surgery as it documents the presence and extent of silicone leakage better than other imaging techniques. Despite this, conventional breast imaging techniques are the methods of choice when breast implant failure is suspected because well-defined and discernible sonographic features have been established for ruptured implants [1], as we shall show throughout this article. Moreover, MRI is more expensive, and many women have contraindications (cardiac pacemakers, aneurysm clips, metallic foreign bodies and claustrophobia) to MRI.
In this article, we describe the preeminent role of MRI in detecting implant failures, illustrating the spectrum of appearances of normal silicone gel implants and of implant ruptures. Furthermore, we summarise the advantages and limitations of other imaging techniques and describe the key findings in detection of silicone implant failure.