AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Background

In the early 20th century, many cosmetic breast prosthetic techniques and materials were used for implants; these included polyvinyl alcohol prostheses, paraffin injections, and injections of free silicone. All of these techniques and materials had notable drawbacks and for the most part were abandoned.

Silicone gel breast implants (SGBIs) have been marketed in the United States since 1962. The US Food and Drug Administration (FDA) began regulating SGBIs in 1976 with the passage of the Medical Device Amendments. In 1992, after months of public and private meetings, the FDA restricted the use of SGBIs to specific instances of medical necessity, such as those involving patients who had undergone mastectomy. Saline breast implants have replaced SGBIs as the common breast prosthesis. Details of the FDA rulings and current status updates are available at the Breast Implants information section of the FDA Web site.^{1, 2, 3, 4}

The ability to reliably evaluate SGBIs with imaging is important because the findings at clinical examination often are nonspecific. The incidence of implant rupture increases with time, and the long-term systemic effects of SGBIs, if any, remain unclear. The diagnosis of SGBI rupture is useful to clinicians and patients; it aids in surgical decision making and helps the patient gain peace of mind.

This article does not address imaging of the rupture of single-lumen saline implants (which usually is clinically obvious because extravasated saline is rapidly absorbed and breast volume quickly decreases at examination).

See also the following related eMedicine topics:
Breast Implants, Silicone: Safety and Efficacy
Breast Reconstruction, Expander-Implant
Uses of the Postoperatively Adjustable Implant in Aesthetic Breast Surgery

Pathophysiology

SGBIs have 2 common designs: single lumen and double lumen. Single-lumen implants contain free silicone gel in a textured or nontextured silicone membrane. Double-lumen implants usually have a saline outer shell that surrounds a silicone inner shell.

Implants may be placed in 2 locations:

• The subglandular location is anterior to the pectoralis muscle, and implantation here is technically easier.
• The subpectoral location is posterior to the pectoralis muscle, and implantation here is technically more difficult.

In essentially all patients, a fibrous capsule forms around the implant (ie, encapsulation). The capsule may be soft and nonpalpable or hard and resistant.

Two types of SGBI rupture can occur:

• Intracapsular rupture occurs when silicone escapes the silastic membrane shell but is contained in the fibrous capsule. This form of SGBI rupture is most common.
• Extracapsular rupture involves the escape of free silicone gel through the fibrous capsule, with extravasation into the breast tissue. Migration of silicone to the axillary lymph nodes also may be present.

Frequency

United States

An estimated 1-2 million patients, or approximately 1% of the adult female population, have breast implants. The incidence of implant rupture increases over time.

• One recent study revealed that the median lifespan of an SGBI is 16.4 years. In that study, 79.1% of implants were intact at 10 years; the percentage decreased to 48.7% at 15 years.⁵

• Another study revealed that of 344 women from Birmingham, Alabama, who were not referred for examination, at least 77% had at least one implant that either was found to have ruptured or that produced an indeterminate finding, when examined via magnetic resonance imaging (MRI). The reported median implant age at rupture was 10.8 years, and submuscular implants were more likely than subglandular ones to rupture.⁶

Mortality/Morbidity

The FDA reviewed 94,120 mandatory reports of SGBI-related adverse events that occurred between 1984 and 1995.⁷ The following terms were used to categorize most adverse events: reaction, failure by rupture, nonspecific adverse reaction, and capsular contracture. Less than 1% of reports involved patient death; of these deaths, none was causally related to an SGBI.

• In 1988, SGBIs accounted for 2.4% of all mandatory device adverse event reports submitted to the FDA. The most common adverse event reported in 1988 was bursting, or rupture. In 1992, when the FDA restricted the use of SGBIs and after public awareness had grown concerning a lack, at that time, of implant-related safety information, SGBI’s accounted for 30.3% of all device reports.³ The most common adverse event reported in 1992 was “reaction.”

Much has been reported on the systemic conditions associated with SGBIs. However, few reports in the peer-reviewed literature support many of the associations. Two well-designed studies were unable to find an association between SGBIs and an increased risk of breast cancer or systemic disease.^{8, 9} (Investigations in animals have revealed that systemic exposure to silicone may be anticarcinogenic.) While no proven association between SGBIs and connective tissue disease exists, the literature is insufficient to entirely rule out an SGBI link to connective tissue disease–like syndromes. 

Local morbidity does occur and can manifest as pain, paresthesia, capsular contracture, migration, siliconoma, and hardness of or an unnatural feel to the breast. Systemic immunologic reaction to silicone exposure also occurs, but the outcome of this exposure, if any, is unclear.

Clinical Details

The FDA and various groups, such as the American Society of Plastic and Reconstructive Surgeons, have advised removal of ruptured SGBIs. Because the findings at clinical examination for SGBI rupture often are unreliable, imaging examination with a reliable technique is necessary for preoperative diagnosis.

Preferred Examination

The imaging examinations for SGBI rupture are the following:

• MRI^{5, 10}
• Ultrasonography^{5, 10}
• Computed tomography (CT) scanning 
• Mammography^{5, 10}

Patients should undergo mammography per the American Cancer Society recommendations for breast cancer screening. When implant rupture and extravasation is detected at mammography, further imaging studies may not be required. However, screening mammography alone is insensitive and its findings often are nonspecific in the detection of SGBI rupture.

Limitations of Techniques

MRI is the most accurate imaging examination for the evaluation of SGBI rupture.¹¹ MRI's drawbacks include its cost and possible unavailability. Ultrasonography is fairly accurate and more available than MRI but is highly operator dependent and has a steep learning curve. CT scanning can show findings similar to those obtained with MRI, but the modality involves ionizing radiation, and it has not been systematically studied to the extent that MRI has been. Mammography is inexpensive. Its findings can be specific if free silicone is present, but it has very low sensitivity.¹²

DIFFERENTIALS

Section 3 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Other Problems to Be Considered

The differential diagnosis of breast implant rupture includes intracapsular and extracapsular ruptures. Extensive silicone gel bleed may have an identical appearance to early or focal intracapsular rupture at MRI.  Extracapsular rupture involves free silicone in the breast parenchyma; this can simulate other breast masses, including breast cancer, at mammography and ultrasonography. Diligent comparison with prior images and attention to the imaging characteristics should prevent confusion.

RADIOGRAPH

Section 4 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

Findings at mammography include the following:

• Rupture with deflation and silicone extravasation
• Measurable periprosthetic opaque band or rim of tissue
• Periprosthetic calcification
• Asymmetry in the size and/or shape of the implant
• Focal implant herniation

Silicone injections and SGBIs can limit the sensitivity of mammography. Implant-displaced views should be obtained, if possible. Comparison with prior images is strongly advised.

Degree of Confidence

When rupture and extravasation are present, confidence is high. However, these findings are uncommon, and other signs are both insensitive and relatively nonspecific. However, when screening mammography performed for other reasons reveals incidental signs of rupture, the sensitivity is high.

CT SCAN

Section 5 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

With intracapsular ruptures, CT scans show findings analogous to the linguine sign at MRI, and CT can demonstrate the extracapsular spread of silicone. To our knowledge, no findings from large studies examining the effectiveness of CT have been published. Because CT scanning involves ionizing radiation and its multiplanar capabilities are limited, MRI typically is the examination of choice.

MRI

Section 6 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

MRI can be used to exploit differences in silicone, water, and fat resonance frequencies to deliver high-resolution images of SGBIs.^{11, 13, 14} The approximate resonance frequency of silicone is 100 Hz lower than that of fat and 320 Hz lower than that of water. Because the resonance of silicone is similar to that of fat, silicone appears similar to fat on nonselective chemical fat- or water-suppressed images.

On short–inversion time inversion-recovery (STIR) images, the fat signal is suppressed and water and silicone are bright. Water-suppressed STIR sequences produce a silicone-only image. Chemical-shift imaging with the modified 3-point Dixon protocol provides both a silicone-only and a water-and-fat image with a single sequence. The relative appearances of silicone, fat, and water on various types of MRIs are summarized in the following table:

Table. Relative Appearances of Silicone, Fat, and Water
on MRI of SGBI Rupture^*

^*Adapted, with permission, from Bassett and Jackson.¹⁵

^† FSE indicates fast spin echo.

While exact protocols differ among institutions, in general, orthogonal-plane imaging with several pulse sequences is performed. Image quality is maximized with the use of a dedicated phased-array breast coil and a high–field-strength magnet; however, in our experience, an adequate examination can also be performed with a low–field-strength, open-sided magnet.

MRI findings include the following:

• Intact single-lumen implants
• • Smooth, low–signal-intensity silicone membrane shell
  • Low–signal-intensity radial folds in the shell (These may be complex, and they always abut the implant at its periphery and span the gel substance only at periphery.)
  • A few internal water droplet signals (common; not a reliable indication of rupture)
  • Reactive fluid around textured implants (common; not indicative of rupture)
  • Fibrous capsule (dark, ringlike structure around the implant)
• Double-lumen implants - Gradual deflation of the saline chamber over time, which results in complex fold patterns and occasional, nonspecific findings of fluid around the outer capsule of the implant
• Intracapsular rupture
• • The linguine sign refers to a collapsed and folded elastomer shell that is floating in gel. This is the most reliable sign of intracapsular rupture.
  • The keyhole (ie, teardrop, inverted teardrop, noose) sign refers to the presence of silicone both inside and outside a radial fold.
• Extracapsular rupture¹⁰
• • Macroscopic extrusion of silicone through the fibrous capsule into the surrounding parenchyma, pectoralis muscle, or lymph nodes is present.
  • Findings in intracapsular rupture should be expected.
• Internal rupture of double-lumen implants
• • Failure of the inner shell may be depicted as saline droplets that are floating in the silicone gel; this is considered a form of intracapsular rupture.
  • The presence of some saline droplets is a normal finding in single-lumen implants.
• Capsular contracture
• • Asymmetric, serrated, focal folding of the fibrous capsule that changes the normal ovoid appearance of the implant may be present.
  • A transverse diameter of less than twice the anteroposterior depth corresponds well to clinically evident contracture.

Degree of Confidence

MRI has a reported a sensitivity of 76-95% and a specificity of 93-97% in the detection of rupture.

False Positives/Negatives

Extensive gel bleeding can have the same findings as those of an intracapsular rupture, in which the keyhole sign is present and the linguine sign is absent. Some authors believe that a tiny tear is present and that it can be found with diligent examination at surgery. Other authors maintain that microscopic gel bleeding alone is the cause. Radial folds are normal invaginations of the silastic membrane, and they should not be confused with the keyhole sign. Silicone should not be present both inside and outside a radial fold.

ULTRASOUND

Section 7 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

Typically, a high-frequency (eg, 10-MHz) transducer is used. Findings may include the following:

• Intact implant
• • Smooth, thin, linear membrane
  • Sonolucent anechoic interior (most reliable but insensitive finding)
  • Reverberation artifact from the proximal membrane wall
  • Radial folds possible - Parts of the implant envelope may be connected by scanning adjacent portions of the implant.
  • Linear internal echoes - These do not indicate rupture. The abundance of the linear echoes has been evaluated, and their effect in the prediction of rupture is not statistically significant.¹⁶
• Intracapsular rupture
  
  
  • Stepladder sign - This is identified as multiple, discontinuous, parallel, linear echoes in the lumen. It is the most reliable ultrasonographic finding in intracapsular rupture and is analogous to the linguine sign at MRI.
  • Echogenic implant lumen
  • Focal, prominent, irregular bulge in the implant
  • Ill-defined or poorly visualized implant margin
• Extracapsular rupture¹⁰
• • Snowstorm, or hyperechoic, noise - Intense, homogeneous echogenicity with loss of the posterior detail of free silicone (silicone can replace portions of the implant envelope; be extruded into the breast parenchyma, forming nodules; and migrate to lymph nodes)
  • Silicone masses (granulomas) - The same hyperechoic noise pattern as above; possibly hyperechoic or hypoechoic and similar to other breast lesions (including carcinoma) or nearly sonolucent and similar to breast cysts (hyperechoic noise is often near or around cystic-appearing masses)
  • Snowstorm pattern in involved axillary lymph node 

• Indeterminate
• • Coarse echogenic aggregates - Occurred in 41% of surgically confirmed implant ruptures in one study¹⁷. These have also been found to occur in approximately the same percentage of implants that have been confirmed as intact at surgery.
  • Cobwebs - Delicate, short, linear echoes diffusely scattered throughout the implant (most authors consider this finding a normal variant; they also are called "commas" in some reports)
  • Smooth focal bulge in the implant
  • Peri-implant fluid collections

Degree of Confidence

Sensitivity ranges from 47-74%; specificity, from 55-96%. An anechoic interior, although rare (4 of 64 implants in one series), is a strong indicator of an intact implant.

False Positives/Negatives

Ultrasonography is limited in the evaluation of the posterior implant wall, because of marked beam attenuation caused by silicone. Use of a low-frequency transducer (eg, 5 MHz) can help improve visualization of the posterior wall of the implant and the adjacent soft tissues. Reverberation artifacts from the near-side interface may limit visibility of the superficial implant margins. Prior silicone injections limit visualization of the implant.

INTERVENTION

Section 8 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Medical/Legal Pitfalls

• Failure to accurately diagnose SGBI rupture could lead to increased legal liability should there be perceived physical or psychological injury from the decision—based on findings from relevant imaging examinations—not to explant the prosthesis. Such injuries could legally be found to be partially or wholly attributable to an incomplete imaging examination; potential causes include inappropriate or insufficient MR pulse sequences for diagnosis, incomplete ultrasonographic evaluation of the entire implant, or mistaken evaluation of the opposite-sided implant. 
• Errors of omission involving significant imaging-related findings that could alter proposed therapy, such as the linguine, snowstorm, or echodense noise signs or extracapsular free silicone, would also increase potential legal liability. Therefore, a thorough and appropriate examination should be performed in all cases, and development of modality-specific protocols is encouraged.

Special Concerns

• Management of ruptured SGBIs typically involves explantation of the prosthesis, with or without reconstruction. Reasons for removal include the potential for silicone migration with subsequent inflammatory reaction; the development of adverse local symptoms in the patient, including pain, deformity, and granuloma formation, is also considered a cause for removal. Removal of SGBIs in patients who have symptoms of connective tissue disease, fibromyalgia, or chronic fatigue syndrome is advocated as well.
• Screening for SGBI rupture in asymptomatic women remains controversial. Some authors advocate mass screening with MRI, while others advocate prophylactic removal at or around 8-10 years after implantation. Still others advocate no removal unless the patient is symptomatic and has imaging and clinical evidence of rupture.

MULTIMEDIA

Section 9 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Media file 1:  Inversion recovery magnetic resonance image shows an intact silicone gel breast implant.
	View Full Size Image
Media type:  MRI

Media file 2:  An intact silicone gel breast implant with a valve appears as a low–signal-intensity region in the retroareolar area. Most silicone implants are valveless; this implant includes a port for addition of saline by the implanting surgeon, for custom-fit sizing. No saline was added to this implant.
	View Full Size Image
Media type:  MRI

Media file 3:  Magnetic resonance image shows a normal radial fold, which appears as a low–signal-intensity line through the implant.
	View Full Size Image
Media type:  MRI

Media file 4:  Fast spin-echo T2-weighted magnetic resonance image shows the keyhole sign. Silicone appears on both sides of the radial fold. The differential diagnosis includes intracapsular rupture and extensive gel bleeding. A small water droplet is in the posterior aspect; small water droplets have no prognostic importance in silicone gel breast implant rupture.
	View Full Size Image
Media type:  MRI

Media file 5:  Magnetic resonance image shows the keyhole, or inverted teardrop, sign. The linguine sign is present elsewhere on the image, and a portion of the sign is adjacent to the keyhole sign. These findings are consistent with an intracapsular silicone gel breast implant rupture.
	View Full Size Image
Media type:  MRI

Media file 6:  Craniocaudal mammogram shows free extracapsular silicone around a ruptured silicone gel breast implant.
	View Full Size Image
Media type:  X-RAY

Media file 7:  Mediolateral oblique mammogram shows extracapsular silicone. Note the opaque axillary lymph node, which is consistent with nodal uptake of silicone.
	View Full Size Image
Media type:  X-RAY

Media file 8:  Sagittal magnetic resonance image shows extracapsular silicone, with a high–signal-intensity lesion in axilla (which is compatible with silicone in node, as shown on the mammogram) (see Image 7).
	View Full Size Image
Media type:  MRI

Media file 9:  Longitudinal ultrasonogram shows the snowstorm, or hyperechoic, noise associated with the capsule in proven extracapsular silicone gel breast implant rupture. Usually, the interior of an intact implant is sonolucent.
	View Full Size Image
Media type:  Ultrasound

Media file 10:  Longitudinal ultrasonogram shows the snowstorm appearance of the soft tissues of the breast, which is consistent with extracapsular silicone gel breast implant rupture and free parenchymal silicone.
	View Full Size Image
Media type:  Ultrasound

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

1. Cunningham B. The Mentor study on Contour Profile Gel Silicone MemoryGel breast implants. Plast Reconstr Surg. Dec 2007;120(7 Suppl 1):33S-39S. [Medline].
2. Spear SL, Murphy DK, Slicton A, et al. Inamed silicone breast implant core study results at 6 years. Plast Reconstr Surg. Dec 2007;120(7 Suppl 1):8S-16S; discussion 17S-18S. [Medline].
3. McLaughlin JK, Lipworth L, Murphy DK, et al. The safety of silicone gel-filled breast implants: a review of the epidemiologic evidence. Ann Plast Surg. Nov 2007;59(5):569-80. [Medline].
4. Hölmich LR, Lipworth L, McLaughlin JK, Friis S. Breast implant rupture and connective tissue disease: a review of the literature. Plast Reconstr Surg. Dec 2007;120(7 Suppl 1):62S-69S. Review. [Medline].
5. Goodman CM, Cohen V, Thornby J, et al. The life span of silicone gel breast implants and a comparison of mammography, ultrasonography, and magnetic resonance imaging in detecting implant rupture: a meta-analysis. Ann Plast Surg. Dec 1998;41(6):577-85; discussion 585-6. [Medline].
6. Brown SL, Middleton MS, Berg WA, et al. Prevalence of rupture of silicone gel breast implants revealed on MR imaging in a population of women in Birmingham, Alabama. AJR Am J Roentgenol. Oct 2000;175(4):1057-64. [Medline]. [Full Text].
7. Brown SL, Parmentier CM, Woo EK, et al. Silicone gel breast implant adverse event reports to the Food and Drug Administration, 1984-1995. Public Health Rep. Nov-Dec 1998;113(6):535-43. [Medline]. [Full Text].
8. Noone RB. A review of the possible health implications of silicone breast implants. Cancer. May 1 1997;79(9):1747-56. [Medline].
9. Silverman BG, Brown SL, Bright RA, et al. Reported complications of silicone gel breast implants: an epidemiologic review. Ann Intern Med. Apr 15 1996;124(8):744-56. [Medline]. [Full Text].
10. Caskey CI, Berg WA, Hamper UM, et al. Imaging spectrum of extracapsular silicone: correlation of US, MR imaging, mammographic, and histopathologic findings. Radiographics. Oct 1999;19 Spec No:S39-51; quiz S261-2. [Medline].
11. Middleton MS, McNamara MP Jr. Breast implant classification with MR imaging correlation: (CME available on RSNA link). Radiographics. May 2000;20(3):E1. [Medline]. [Full Text].
12. Gorczyca DP, Gorczyca SM, Gorczyca KL. The diagnosis of silicone breast implant rupture. Plast Reconstr Surg. Dec 2007;120(7 Suppl 1):49S-61S. Review. [Medline].
13. Morgan DE, Kenney PJ, Meeks MC, et al. MR imaging of breast implants and their complications. AJR Am J Roentgenol. Nov 1996;167(5):1271-5. [Medline].
14. Orel SG. MR imaging of the breast. Radiol Clin North Am. Jul 2000;38(4):899-913. [Medline].
15. DeBruhl ND, Gorcyzca DP, Bassett LW. The Augmented Breast. In: Bassett LW, Jackson VP, Eds. Diagnosis of Diseases of the Breast. Philadelphia, Pa: WB Saunders; 1997:563-79.
16. Palmon LU, Foshager MC, Parantainen H, et al. Ruptured or intact: what can linear echoes within silicone breast implants tell us?. AJR Am J Roentgenol. Jun 1997;168(6):1595-8. [Medline].
17. Venta LA, Salomon CG, Flisak ME, et al. Sonographic signs of breast implant rupture. AJR Am J Roentgenol. Jun 1996;166(6):1413-9. [Medline].

Article Last Updated: Mar 20, 2008