is highly unlikely that any textile fibres that exist today, have not, at
sometime or the other, been considered for use in the present-day advanced
medical field. Hospital rooms are upholstered with similar materials to
those in our homes. The staff needs uniform and patient needs clothing.
Thus, the largest use of textile fibres in the medical history is for items,
which do not differ significantly in physical specifications or chemical
type from those of our domestic surroundings, except for those for
The general uses are, however, not
commonly thought of as medical textiles - medical textiles are those, which
are associated with speciality areas where the use of textile materials is
of direct assistance in the medical and surgical treatment of the patient.
While the major volume of these special medical textiles are for non-implantables,
the most interesting uses of textiles for medical application are in the
areas of extra corporeal and implantables. This has been shown in Table 1.
The fibres for medical applications may be produced from common polyester or
propylene or from some more exotic polymers such as polyglycolic acid esters
|Table 1: Medical textiles
||Hellow fibers for dialysers and oxygeneratiors
||Fabrics for heart values and percutaneous leads
||Patches for heart repair
||Surgical reinforcement meshes
||Reinforced tubular meshes for veins and grafts
||Fibre reinforcement - bone plates and ligaments
||Restraining loops for intraocular lences
To a large extent, these fibres are
manufactured in the same way as the textile fibres are. However, commercial
polymers contain additives and contaminants like plasticisers, stabilisers,
residual monomers and catalysts and, sometimes, finishing agents. These are
not only undesirable but may also be harmful in medical applications. Any
material implanted within the body has to be inert as well as compatible
with blood and other body fluids. In addition, it must cause no tissue
irritation, be non-toxic, release no foreign material and cause no tumors
with long-term use. In essense, such materials have to be treated as drugs.
Today, more and more people are aware
that an operating room could not solely operate without the necessary
materials. Consequently, one of the most important materials needed in the
operating room are the sutures. Generally, sutures are surgical guts, or
silk, cotton or metal thread, 18 or more inches long, threaded on a needle.
It is used mainly for sewing or suturing together the edges and the surfaces
of tissue, for checking the flow of blood, fastening drainage tubes in
position, etc. Sutures are either interrupted, each stitch tied separately;
Or continuous, the thread running in a series of stitches, only the first
and last of which are tied. In the following paragraphs, one of the most
important applications of textiles in medical field, sutures, along with its
production techniques, is reviewed.
Types of Sutures
Sutures are small lengths of yarn with
needle attached to one end and are generally used to close lacerations, cuts
and deliberate incision which have been made on an item or living being. The
practice of suturing started at an early age in civilisation with the sewing
of protective garments and, certainly by the time of the early Chinese
culture, for closing wounds in humans. In fact, the Chinese started by using
silk as their source for suturing filaments. Even today, silk remains as one
of the most prominent material, used for this purpose by the physician.
Another age old suture still produced
and used today is the gut suture, which is made from bovine stomachs and is
basically a collagen monofilament. This protein derivative suture is derived
from the sub-mucosa of sheep intestines or scrosa of bovine intestine by
cutting the intestines in narrow ribbons after chemically and mechanically
cleaning them. Several ribbons are then twisted together, dried, ground and
first new filament to come in this field is cellulose fibres followed by
nylon and a number of other polymeric filaments, which included the olefins
and polyester. All have been produced in numerous forms such as
monofilaments and multifilaments, having different diameters and tensile
strength. In the last 30 years, a more exotic entry into the suture field
has been the addition of resolvable sutures made from synthetic polymeric
materials. The typical example of this category include: Homopolymers and
copolymers of glycolide, D L lactide and E-caprolactone. The resolvable
sutures are bio-compatible and bio-degradable, as are silk and gut sutures,
but can also be ejected from the interior of the body through natural body
function. Table 2 shows the list of sutures most commonly used today, along
with their general strength characteristics.
Among the natural polymers, silk is
presently the most common material used. Polyglycolic acid (PGA), polylactic
acid (PLA) and polyester are the other major synthetic polymers used to
manufacture sutures. Polyester sutures fall into the category of
non-absorbable and, as such, are used mostly for closing cutaneous or oral
incisions where the suture can be easily removed when required. PGA and PLA
sutures are bio-degradable and, as such, can be used internally for heart
repair and for similar operations. By proper design of the polymer, the rate
of absorption can be varied to match one's need.
The length of sutures varies
considerably. Each suture depends on the character of the work and the
nature of the operation. For instance, deep work in the pelvis requires a
much longer suture than would be necessary in suturing an area closer to the
surface of a wound. Experience and judgement, along with the desire of the
surgeon, must be the determining factors in details and selection of
|Table 2: Satures examples
Surgical guts are also known as catgut
and is made from the sub-mucous layer of a sheep's intestine. Once cleaned,
dried and twisted into threads of various sizes, they are prepared for use
by special processes that include innumerable inspections of gauze and
tensile strength and scrupulous sterilisation. The length of time for
complete absorption of surgical gut in a wound varies according to the
action of certain hardening agents.
This muscle connective tissue of beef
has been used in reconstructive orthopedic surgery and for the repair of
hernias. It is not a true absorbable suture, but becomes a part of the
tissue after the wound has healed.
This is prepared from the thread spun by
the silkworm larva in making its cocoon. It may be twisted or braided, and
it comes in sizes comparable with surgical gut. Its characteristics are:
High tensile strength.
Less tissue reaction.
This is made from cotton fibres. The
strands are twisted and used for both internal and external suture. It
should always be used wet for maximal strength.
This is a synthetic polyamide material,
which can be used in the form of:
This material has maximal flexibility
and tensile strength, yet causes little or no local reaction in the tissue
in which it is placed.
This is a synthetic polyester fibre that
has greater tensile strength, minimal tissue reaction, maximal visibility,
non-absorbent and non-fraying qualities.
This is made of twisted linen thread; It
has sufficient tensile strength, but is rarely used as suture material.
Silver Wire Clips
Many styles of clips are available for
the purpose of holding the edges of the tissue in approximation. They tend
to produce some scarring when used in the skin, but may be used when the
wound is infected.
This is made from the fluid secreted by
the silkworm when they are ready to form their cocoons. The disadvantage is
that they must be soaked in normal saline for about 10 minutes before use to
make them pliable.
This type of suture is made of stainless
steel, usually used for hernia repairs and large defects. It is rarely used.
This is a bluish bray metal that is
non-irritating to the body tissues. It is used because of its high tensile
strength and its inert reaction to tissues.
Some of the characteristic properties
considered in selecting a suture material are: Absorption, pliability, knot
tying, holding strength and tissue reaction.
A suture must hold its strength for a
period of 10 to 12 days to allow healing to complete. If bio-absorbability
is required, then, the rate of absorption becomes a criterion. Furthermore,
the suture must be pliable for the surgeon to handle and tie it properly,
and at the same time, must hold a knot without slipping. Lastly, the suture
must not cause a tissue or skin reaction or irritation.
Absorbable sutures were originally made
of the intestines of sheep, the so-called catgut. The manufacturing process
was similar to that of natural musical strings for violins and guitars, and
also of natural strings for tennis racquets. The inventor, a 10th century
surgeon named al-Zahrawi reportedly discovered the dissolving nature of
catgut when his lute's strings were eaten by a monkey. Today, gut sutures
are made of specially prepared beef and sheep intestine, and may be
untreated (plain gut), tanned with chromium salts to increase their
persistence in the body (chromic gut), or heat-treated to give more rapid
absorption (fast gut).
However, the major part of the
absorbable sutures used are now made of synthetic polymer, ie, fibres, which
may be braided or monofilament; These offer numerous advantages over gut
sutures, notably ease of handling, low cost, low tissue reaction, consistent
performance and guaranteed non-toxicity. In Europe and Japan, gut sutures
have been banned due to concerns over bovine spongiform encephalopathy (mad
cow disease), although the herds from which gut is harvested are certified
BSE-free. Each major suture manufacturer has its own preparatory
formulations for its brands of synthetic absorbable sutures; Various blends
of polyglycolic acid (Vicryl for example), lactic acid or caprolactone are
Non-absorbable sutures are made of
materials which are not metabolised by the body, and are used therefore
either on skin wound closure, where the sutures can be removed after a few
weeks, or in some inner tissues in which absorbable sutures are not
adequate. This is the case, for example, in the heart and in blood vessels,
whose rhythmic movement requires a suture, which stays longer than three
weeks, to give the wound enough time to close. Other organs, like the
bladder, contain fluids, which make absorbable sutures disappear in only a
few days, too early for the wound to heal. Inflammation caused by the
foreign protein in some absorbable sutures can amplify scarring, so if other
types of suture were less antigenic (ie, do not provide as much of an immune
response), it would represent a way to reduce scarring.
Now that some of the basics of suture
requirements and material properties have been identified, the following is
a presentation of steps taken to manufacture a typical multi-filament
Multi filaments are purchased or
manufactured by the suture manufacturer. However, these products are
produced from specially approved raw materials and manufactured through
specially approved procedure. The multi filament yarn is then twisted on a
common ring twister. The number of twist per inch or cm is determined by the
producer and can be very high. This twist is a factor in the final
properties of the suture and affects the 'Feel' and knot tying faciliities.
The next operation is to braid a number
of twisted yarn ends into a single strand. First, the yarn is wound onto
braider bobbin and placed on a braiding machine. The number of carriers used
in braiding vary with the suture specifications. Normally, a suture plant is
equipped with braiders having 6 to 24 carriers. The braided suture material
can be described as looking like a miniature 'Sash' or sash cord or ski
After the braiding operation, stretching
operation follows. The stretching unit is equipped with two sets of dual
rollers, and like any other stretching system, the delivery set moves faster
than the feed set. Normally, a coat of finish is applied to the braided yarn
as it is stretched. After testing of quality parameters, the spools are
stored for next operation.
Next operation is the needle attaching
operation. The braided yarn is cut to desired lengths, generally from 150 mm
to 900 mm. One end of the suture - about 25 mm - is t dipped in a polymer
solution and placed in an oven for curing. This operation makes the end
stiff and easier to handle while attaching the needles. There are,
generally, two ways for attaching the needles. In the first method, the
needles have holes drilled in the end opposite to the sharp pointed end, the
yarn is pushed into the hole and then held in place by crimping the needle
barrel into the yarn. The other method utilises a needle that has two lobes,
flat configuration on the end, instead of a hole. The yarn is placed on top
of this configuration and then a special clamping device folds the two lobes
on top of the yarn, thus holding the two firmly together. Whatever may be
the method that is used, testing of security of attachment is very
Sterilisation and packaging are the two
final operations performed during suture manufacture. Generally, the
completed suture is rolled into a circle of 25 mm in diameter and then
placed in a small package. Sterilisation is done by two methods. One is a
toxic gas sterilisation in which ethylene oxide is used and the other is by
radiation. In gas sterilisation, several thousand packages of sutures are
placed in trays, which are then placed in a steriliser. The steriliser is
located in an air-tight room wherein the air pressure is higher than that
used in the steriliser while the gas is present. Radiation sterilisation is
carried out in a similar manner except that the radiation box and personal
safeguards are different. The needle attachment and sterilisation steps are
the classic operations related to suture manufacturing technique.
After sterilisation, the packages are
sealed and are ready for marketing.
Application of textiles in the medical
field has come a long way since its first recorded use in the Edwin Smith
Surgical Papyrus nearly 4,000 years ago; The description is of the use of
stitches to repair wounds. It is, of course, quite likely to assume that
hand woven cloth or spider webs were used, even earlier, to stop bleeding.
In the Susanta Sambita of Indian
literature, written approximately 2,500 years ago, a variety of suture
materials are mentioned, namely, horse hair, leather strips, cotton, animal
sinews and fibrous tree bark.
The manufacture of modern day sutures
made from polymers is not difficult. Standard or slightly modified fibre
spinning units are usually adequate. However, the most important factor in
suture spinning is the outstanding characteristics of the particular polymer
being processed, and the biological characteristics of the tissue in which
it is to be placed.
Further, the anticipated time of
healing, the potential contamination and infection, the patient's physical
condition and the past post-operative course of the patient are other
considerations, which generally, govern the choice of a particular type of
1. James O Threlkeld: IFJ, October 1994,
2. Raul De Persia, Alberto Guzman,
Lisandra Rivera & Jessica Vazgwz: Mechanics of Biomaterials: Sutures
After the Surgery, Applications of Engineering Machines in Medicine, May
3. Jim Fowler and John Hagewood: IFJ,
October 1994, Page 28.
4. John Hagewood: IFJ, October 1994,
5. Rakesh Gupta: Fibre World,
January 1989, FW 2.
6. Rakesh Gupta: Fibre World, March
1989, FW 4.
The author acknowledges with thanks the
management of MANTRA for giving permission to publish this paper.
Note: For detailed version of this
article please refer the print version of The Indian Textile Journal
December 2008 issue.
Dr S K Basu
Director, Man Made Textiles Research