The failure of synthetic polymeric medical devices - Durability and Reliability of Medical Polymers - page 200

9.5.1 Failure of tissue expander
The consequences of failure of implants are always serious for patients,
involving trauma and loss of saline into their bodies. Just this happened to
one woman one night several weeks after fitment of the device following
mastectomy. The device had been filled at regular intervals and was apparently
at or near capacity. The patient had already experienced the psychological
shock of discovery of cancer, and loss of her breast, so the sudden loss of her
shape was severe. On visiting her consultant, the device was extracted under
anaesthetic and found to have fractured where the catheter joined the bag (Fig.
9.18). The bag was then made available for independent examination.
A check made using FTiR showed there to be no problem apparent with
the polymer, all absorption peaks observed corresponding with the known
spectrum for polysiloxane. However, the bag was supplied in a contaminated
state with sodium chloride crystals visible on the inner surface in addition
to congealed blood. There were relatively few absorption peaks owing to
the thickness of the sample (c. 100 mm). However, in order to preserve the
device intact, it was necessary to fold the membrane for insertion into the
sample chamber of the spectrometer. The bending stress at the fold created
a tear, showing the poor strength of the material when subjected to relatively
low loads.
Optical microscopy showed that the original fracture extended across
the catheter where it joined the bag, and showed how the fracture extended
between two shoulders from the bag extension, one above and the other
below the crack surface (Fig. 9.19). The survey confirmed the lack of clear
features on the fracture surface itself although a cusp was found at one edge

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9.18 Fractured breast tissue expander in silicone rubber with crack
between catheter and bag.