This is an embroidered stent, as used for the repair of abdominal aortic aneurysms.
The picture shows how much it can be twisted, without the lumen becoming closed.
Embroidery Technology is not exactly new. Hand embroidery has been used for decorating
textiles for thousands of years; even automatic embroidery machinery has been in
use for over a 150 years. The only thing that is really new is its application to
surgical implants, which has been developed within the last few years.
Textile surgical implants have, until now, been constrained by the use of the traditional
methods of knitting, weaving or braiding to make fibre assemblies. However, weaving
usually limits the designer to placing fibres interlaced at right angles to one another,
knitting forms the fabrics in loops which are generally dimensionally unstable, and
braiding confines the designer to usually narrow structures made in a process similar
to plaiting hair.
Embroidery is the formation of stitches on a base cloth, it being possible to place
the stitches in any position. The base cloth can be dissolved away after the stitching
process has been carried out, and, assuming appropriate design features have been
incorporated, the structure holds securely together as a stable entity. When making
technical textiles, one is usually interested in structure rather than appearance
and since fibres can be placed in any orientation in the plane of the base cloth,
endless possibilities arise, especially mimicking natural fibrous arrays such as
natural ligaments. For example, the fibres in a particular ligament may fan out from
a bundle 3 mm wide to an array 20 mm across, a design feature which is easy to reproduce
with textile fibres using embroidery technology. Another example could be a fracture
fixation device which has load bearing threads arranged optimally to fit the part
of the body where it is to be used and with open mesh parts which allows tissue ingrowth
and consequent incorporation into the body.
The colour change facility of the machine can be used to alter the components in
various parts of the implant as it is being manufactured – and allows the automated
incorporation of attachment parts and other features very easily.
Modern embroidery uses sophisticated (and expensive) software dedicated to the quick
and easy production of designs for the decoration of garments. Modifications to the
use of this software allow fibre arrays to be designed for use as surgical implants
with similar facility. This leads to the possibility of customised implants for individual
patients. By way of example, we have taken a rough sketch of a component from a surgeon
and converted it into an embroidery design, e-mailed it to Pearsalls Limited in Taunton,
Somerset, and moved from concept to manufactured product in less than three hours
. The potential, even for specialist trauma surgery, is very exciting.
We have proved the general concept of using embroidery for surgical implants in a
MedLINK project, which developed a device for the endovascular repair of abdominal
aortic aneurysms. Although up to 1900 different size combinations are required to
treat all the patients likely to be seen by a surgeon, special software now allows
us to take the dimensions of an aneurysm provided by the surgeon from CT Scans and
produce a customised embroidery design within seconds, and commence manufacturing
within minutes. The device has significantly improved characteristics when compared
with most other available devices. It is marketed by Lombard Medical Ltd.
Other work has being carried out to develop a range of orthopaedic implants for a
diverse range of end users. Most of our devices are constructed of polyester suture(surgical
stitching) thread. One of the reasons for this is that the use of threads produced
specifically for surgical applications raises no questions for surgeons about suitability
for well designed implants: their behaviour and properties in the body are well documented.
We are now developing advanced materials and bioabsorbable structures and also active
implants. The future is very encouraging and it is hoped that the technology will
help in producing the framework for organs using the patients own cultured tissue
which will replace diseased and damaged parts without the problems currently associated
with transplant surgery.
