Biomedical Engineering Reference
In-Depth Information
The thermal properties of the polymer showed a main melting point of
about 200 °C, with subsidiary peaks at 180, 126 and 73 °C. it is known that
the suture was coated with another polyglactide of different composition,
probably exhibited by a large peak at 180 °C while the smaller peaks
represented lubricants such as calcium stearate. Finally, the fibre proved
soluble (several hours immersion) in strong caustic soda of pH 14, showing
that alkaline conditions were needed for hydrolysis. Some body fluids are
slightly alkaline, so enhancing degradation.
9.8.3 Possible causes of failure
it was therefore necessary to examine how the suture failed at such a critical
moment. The company ethicon publishes guidelines on their Vicryl suture
on their website, www.ethicon360.com, stating that the sutures retain 75%
of their original tensile strength after 2 weeks implantation in rats, and 50%
at three weeks. Because the sutures failed the day after they were emplaced,
it was thus unlikely that they failed by dissolution in her body. However, the
doctor who restitched the wound said that the Vicryl suture had fractured in
the middle. Unfortunately the suture was discarded, so no forensic examination
could be made of the remains, and his assertion could not be tested.
it is unusual for cords to break centrally, fractures tending to occur at
knots or other attachment points, as experiment had shown. Alternatively,
the stitch could simply have not been tied correctly in the first place using
approved knots and placements in the soft tissues to be joined together.
evidence from the staff involved in the original stitching was contradictory,
but it was known that very junior staff had been involved when the patient
was stitched.
9.8.4 Outcome
The legal action did not proceed in the absence of clear evidence of either
medical negligence or a defective suture, and the patient could not be
compensated for her distress. it is unfortunate that the physical evidence
of failure in many medical cases is frequently lost or discarded, perhaps
because the items are disposable anyway. However, it may leave patients
uncompensated, and product manufacturers uncertain of the state of their
product. if the design and manufacture of products is to be improved, then
analysis of failures is vital to determining the cause or causes of the specific
problem in question. That task is impossible if the failed products are no
longer available for examination. even a photograph of a failed product is
better than no product at all, for much can be learnt from good photographs
of failures, especially now when even a mobile phone can be used to record
evidence.
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