  Breast implants are widely used after breast cancer resection and must be
changed regularly to avoid a rupture. To date, there are no quantitative
criteria to help this decision. The mechanical evolution of the gels and
membranes of the implants is still under investigated, although it can lead to
early rupture. In this study, 35 breast explants having been implanted in
patients for up to 17 years were characterized by ex vivo measurements of their
mechanical properties. Using Acoustic Radiation Force Impulse (ARFI) ultrasound
elastography, an imaging method for non-destructive mechanical
characterization, an increase in the stiffness of the explants has been
observed. This increase was correlated with the implantation duration,
primarily after 8 years of implantation. With an increase of the shear modulus
of up to a factor of nearly 3, the loss of flexibility of the implants is
likely to lead to a significant increase of their risk of rupture. A
complementary analysis of the gel from the explants by mass spectrometry
imaging (MSI) and liquid chromatography coupled to high resolution mass
spectrometry (LC-HRMS) confirms the presence of metabolites of cholesterol
originating from the breast tissues, which most likely crossed the membrane of
the implants and most likely degrades the gel. By observing the consequences of
the physical-chemical mechanisms at work within patients, this study shows that
ultrasound elastography could be used in vivo as a quantitative indicator of
the risk of breast implant rupture and help diagnose their replacement.
