Balloon catheters and angioplasty

17 Expanded stent in artery acting to widen the channel. 

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 Dm). 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 

78 Fractured breast tissue expander in siiicone rubber with crack between catheter and bag. 

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