21 Medical Textiles

S. Amsamani

1. INTRODUCTION

Combination of textile technology and medical sciences has resulted into a new field called medical textiles. Medical and related healthcare and hygiene sector is an important and growing part of the textile industry. Textile materials and products that have been engineered to meet particular needs are suitable for any medical and surgical application where a combination of strength, flexibility, and sometimes moisture and air permeability are required. The numbers of applications are huge and diverse, ranging from a single thread suture to the complex composite structures for bone replacement, and from the simple cleaning wipe to advanced barrier fabrics used in operating rooms. The Meditech products are available in woven, knitted and non-woven forms based on the area of application. Development of medical textiles can be considered as one such development, which is really meant for converting the painful days of patients into the comfortable days.

2. OBJECTIVES

At the end of the session the learner will be able to

•  Understand the implication of medical textiles in caring and saving life.
•  To gain knowledge about various medical textile products and uses

3. DEFINITION

   Medical Textiles are fiber, yarn, fabric based products whose structures are designed for used in first-aid, clinical treatment of a wound or medical condition, hygiene care or as a part of the human body. The major characteristics of medical textiles are non toxicity, non allergenic and ability to be sterilized. Medical textiles should also have good strength, elasticity, biocompatibility, durability and flexibility depending upon the product. As biomedical materials may be contaminated with bacteria, sterilization is important for biomedical polymers. The sterilization technique can be physical or chemical.

4. CATEGORIZATION OF MEDICAL TEXTILES

• Non-implantable materials– wound dressings, bandages, plasters.
• Extracorporeal devices– artificial kidney, liver, and lung.
• Implantable materials – sutures, vascular grafts, artificial ligaments, artificial joints.
• Healthcare/hygiene products– bedding, clothing, surgical gowns, cloths, wipes.

5.1 Non-implantable materials

These materials are used for external applications on the body and may or may not make contact with skin. Some of the common non-implantable materials are wound care fabrics and absorbent pads, bandages, plasters, gauzes, lint and wadding.

5.1.1     Wound care

The functions of these materials are to provide protection against infection, absorb blood and exudates, promote healing and, in some instances, apply medication to the wound. Common wound dressings are composite materials consisting of an absorbent layer held between a wound contact layer and a flexible base material. The absorbent pad absorbs blood or liquids and provides a cushioning effect to protect the wound. The wound contact layer prevents adherence of the dressing to the wound and be removed easily without disturbing new tissue growth. The base materials are normally coated with an acrylic adhesive to provide a means by which the dressing is applied to the wound. The use of healing property fibers like collagen, alginate, and chitin has proved success in many medical and surgical applications.

Other textile materials used for wound dressing applications include gauze, lint, and wadding. The type of dressing used varies based on the type of wound and location of the wound. The wound dressing material should be sterile, breathable and should provide

• a moist healing environment.

5.1.2   Bandages

The wound care layer is held in proper position by a bandage holds. It supports the dressing material and function as compression material. They can be woven, knitted, or nonwoven and are either elastic or non-elastic. Compression bandages are used for the treatment and prevention of deep vein thrombosis, leg ulceration, and varicose veins. Orthopedic cushion bandages are used under plaster casts and compression bandages to  provide padding and prevent discomfort. The bandage can also be used on standalone basis in orthopaedic cases (e.g. crepe bandage). The bandage products consist of:-

• Rolled Bandage
• Gauze bandage
• Elastic/Non-elastic bandage
• Light support bandage
• Crepe bandages / compression bandages
• Plaster-of-Paris (POP)

Manufacturers: Johnson and Johnson India, KOB textile – Dressing Material, JajooSurgicals Private Limited

5.2 Extracorporeal Devices

Extracorporeal devices are mechanical organs that are used for blood purification and include artificial kidney (dialyser), artificial liver, and mechanical lung. The function and performance of these devices has found a facelift with use of newer fibers and modern textile technology.

5.2.1  Artificial Kidney / Dialysers

The function of the artificial kidney is achieved by circulating the blood through a membrane, which may be either a flat sheet or a bundle of hollow regenerated cellulose fibres like hollow viscose or hollow polyester fibre in the form of cellophane that retain the unwanted waste materials. The kidney dialysis machine is outside the body and purifies the blood using a filter called the haemodialysor.

The haemodialysor is made primarily made of poly sulphone and polyacetate. Multilayer filters composed of numerous layers of needle punched fabrics with varying densities specifically designed for rapid and effective removal of waste materials. The average price of artificial kidneys is around Rs. 300 per unit. The typical characteristics of these fabrics are low linting, high durability, good capillary rise, good absorbency, biodegradability and inert behavior.

5.2.2    Artificial Heart

The artificial heart is intended for use in patients whose hearts have been irreparably damaged, and for whom, existing methods of surgical intervention and/or drug therapy are inadequate. The device is available at Rs 34 lakh and the overall cost of surgery as Rs 40 lakh. In India, about 20 million patients suffer from heart failure every year; hence this devise would be a live supporter.

5.2.3     Artificial Lung

The microfibers or the membrane oxy-generator are the technical textile component in this device. The microporous membranes of the mechanical lung possess high permeability to gases but low permeability to liquids and functions in the same manner as the natural lung allowing oxygen to come into contact with the patient’s blood. The artificial lung device is connected to the heart’s right ventricle. It relies on the heart to send blood through the lung, where it receives oxygen and offloads carbon dioxide as it flows through the arrays of microfibers or membrane oxygenators. Oxygen rich blood passes from the device into the left atrium and then to the rest of the body. These membranes are made up of knitted high performance fibers with good strength and compatibility.

5.2.4     Artificial Liver

The artificial liver utilizes hollow fibres or membranes similar to those used for the artificial kidney to perform their function. In this system, patient’s blood or plasma is pumped into bioreactors, with are hollow fibre devices which act like the liver to transform human hematoma cell line.

5.3   Implantable materials

These materials are used in effective repair of the body whether, like wound closure (sutures)or replacement surgery (vascular grafts, artificial ligaments,).Biocompatibility is of prime importance. Four key factors determine how the body reacts to the implant.

These are as follows:

The most important factor is porosity, which determines the rate at which human tissue will grow and encapsulate the implant. Small circular fibres are better encapsulated with human tissue than larger fibres with irregular cross-sections. Toxic substances must not be released by the fibre polymer, and the fibres should be free from surface contaminants such as lubricants and sizing agents. The properties of the polymer will influence the success of the implantation in terms of its biodegradability.

5.3.1    Soft-tissue implants

The strength and flexibility characteristics of textile materials make them particularly suitable for soft-tissue implants. A number of surgical applications utilise these characteristics for the replacement of tendons, ligaments, and cartilage in both reconstructive and corrective surgery.

5.3.2    Orthopaedic implants

Orthopaedic implants are those materials that are used for hard tissue applications to replace bones and joints. This category also includes screws and plates that are implanted to stabilise fractured bones. To promote tissue growth around the implant a nonwoven mat made from graphite and PTFE (e.g. Teflon) is used, which acts as an interface between the implant and the adjacent hard and soft tissue. Braided surgical cables composed of steel filaments ranging from 13–130mm are used to stabilise fractured bones or to secure orthopaedic implants to the skeleton. Carbon fibre reinforced composite structures are used to resurface the defective areas of cartilage within joints (knee/elbow).

5.3.3     Artificial Joints

The orthopaedic joints are used for patients suffering from arthritis and accidental damage of joints. The artificial joints are primarily made of Titanium, Stainless Steel and Cobalt, materials which exhibit compatibility with the human body. The technical textile component in joints is Ultra High Molecular Weight High Density Polyethylene (UHMWHDPE).It helps in smoothing movement of the joints. The approximate market for joints in India is around Rs.4.5 crore.

5.3.4    Artificial Ligaments

An artificial ligament is medical device for joining ends of two bones. The artificial ligaments are made from man-made fibres like polyester. Artificial ligament is a multi-layered or tubular woven structure having intra-auricular region, with at least one bend and end regions. Each region is woven so as to possess the required flexibility and strength. PET (Polyethylene Teraphthalate ) is primarily used for manufacturing artificial ligaments. Braided polyester artificial ligaments are strong and exhibit resistance to creep and cyclic loads. Braided composite materials containing carbon and polyester filaments have also been found suitable for knee ligament replacement. The artificial ligaments are generally subject to lot of wear and tear. They also carry a risk of septic arthritis. The artificial ligaments market in India is small and primarily artificial ligaments are imported from Netherlands and USA.

5.3.5     Artificial Tendon (Mesh)

Artificial tendons are woven or braided porous meshes or tapes surrounded by a silicone casing. During implantation the natural tendon can be looped through the artificial tendon and then sutured to itself in order to connect the muscle to the bone. Artificial Tendons or meshes are used in hernia repair and abdominal wall replacement. The mesh could either be woven or knitted. Polypropylene, Polyester mesh is primarily used in hernia repair as it is resistant to infections. PET (polyethylene terephthalate, commercial name Dacron) is also used. Meshes for hernia and other medical requirements are manufactured using warp-knitting process on Double Raschel Warp knitting machines.

The major domestic producer is TTK Healthcare. The artificial tendons are primarily imported and over 50% of the imports are from USA followed by UK, Germany, France, Singapore, Denmark and Hong Kong.

5.3.6    Cardiovascular Implants

Vascular grafts are used in surgery to replace damaged thick arteries or veins 6 mm,8 mm, or 1 cm in diameter. Commercially available vascular grafts are produced from polyester, PET or PTFE with either woven or knitted structures. Straight or branched grafts are possible by using either weft or warp knitting technology. The graft is impregnated with either collagen or gelatin which after a period of 14 days, degrades to allow tissue  encapsulation. Artificial blood vessels with an inner diameter of 1.5 mm have been developed using porous PTFE tubes. The tube consists of an inner layer of collagen and heparin to prevent blood clot formation and an outer biocompatible layer of collagen with the tube itself providing strength.

5.3.7        Artificial Vascular Grafts

In order to function effectively, the grafts need to have special characteristics like – non-thrombogenic surface, elasticity, long-term tensile strength, bio-comparability, durability and bacteria resistance. The type of fabric used is woven or knitted based on the area of application. Most textile grafts for large and medium artery replacement are made of either PET or PTFE. Vascular grafts are manufactured using warp-knitting process on Double Raschel Warp knitting machines. Artificial heart valves, which are caged ball valves with metal struts, are covered with polyester (e.g. Dacron) fabrics in order to provide a means of suturing the valve to the surrounding tissue. The price range varies from as low as Rs. 2000 to Rs. 20,000.

TTK Healthcare in collaboration with Sri Chitra Tirunal is the pioneer of vascular grafts in India.TTK Healthcare is testing indigenously developed grafts with South Indian Textile Research Association (SITRA).

5.3.8        Artificial Heart Valves

Artificial heart valves are implanted in the heart of the patients who need treatment for valve related diseases. The heart valve is made up of three parts, a metallic housing, a disc or ball (Ultra high molecular weight-polyethylene (UHMW-PE)) which functions as occlude and a sewing ring made of warp knitted 100% polyester. Heart valves are manufactured using warp-knitting process on Double Raschel Warp knitting machines. The functional requirement of heart valves are minimum trans-vascular pressure, gradient non-thrombogenic, low wear/tear, minimal leakage, appropriate valve ratio. The heart valve market in India is approximately Rs. 74 crore.

The only producer in India is TTK Healthcare. The imports of heart valves arrive primarily from USA, Brazil, Italy and Netherlands.

5.3.9     Surgical Sutures

The surgical suture is used for stitching together skin deformations, open wounds, organs and blood vessels. The surgical sutures are classified into two categories –

• Absorbable suture – These get dissolved in the body and do not require removal
• Non-absorbable suture – These are sterilised sutures which need to be removed after a specified time

   The raw material for sutures ranges from bovine intestine tissues to Poly glycolic acid (PGA), collagen, mono-filament polyester/polypropylene and multifilament nylon/polypropylene/polyamide and silk. The type of suture used varies based on the area of application and type of medical intervention. They could be either monofilament, multifilament braided fabrics. The general characteristics of sutures are sterilised (non-toxic), hypoallergenic, high tensile strength, and high knot security, flexible and smooth passage through tissues, good pliability, and minimum tissue reaction. The surgical sutures market in India is dominated by Johnson and Johnson.

5.3.10 Contact Lenses

The contact lenses are typically used to correct vision, although some people wear colored contact lens to enhance or change their eye color. Contact Lenses are made from a water absorbing material called HEMA (Hydroxy Ethyl Metha Acrylate) and are very soft to handle and comfortable on the eyes. Hard contact lenses are made of PMMA (polymethyl methacrylate) and are obsolete.RGP lenses are semi-rigid lenses made from silicones which allow oxygen through to the eye. Contact lens market in India is dominated by soft contact lenses. USA, Canada & UK are the largest export destinations of contact lenses from India accounting for 70-80% exports.

5.3.11   Artificial Cornea

The cornea is the transparent front portion of the eye that permits light to enter the eye. Normally crystal clear, it can become cloudy or misshapen, causing reduction

in vision or blindness. The polymers used in artificial cornea need to be biocompatible, flexible, sufficient mechanical strength. The artificial cornea is made using following materials:

• PMMA (Poly methyl methacrylate)
• PHEMA (Poly 2-hydroxythyl methacrylate hydrogels)
• PVA (Poly vinyl alcohol)

   The characteristics required for textiles, used in the making of artificial cornea are to withstand pressure, be transparent, have appropriate curvature, and have suitable refractive index, sufficient tensile strength to allow surgical manipulation and fixation, scratch resistance. In India, approximately 30,000 cornea transplants are carried out every year.

5.3.12    Artificial Skin

Skin grafting is the procedure of replacing dead skin with live skin. After removing burnt / damaged skin, surgeons blanket the wound with a covering (artificial skin) before applying a skin graft on top of this biomaterial to encourage the growth of new skin to close the wound. Artificial skin consists of two layers. The bottom layer, which is designed to regenerate the lower layer of real skin, which is a composed of a matrix of interwoven bovine collagen (a fibrous cow protein) and a sticky carbohydrate (sugar) molecule called glycosaminoglycan, which mimics the fibrous pattern of the bottom layer of skin. This matrix then sticks to a temporary upper layer: a medical-grade, flexible silicon sheet that mimics the top, epidermal layer of skin.

Skin grafts look somewhat like translucent plastic wrap. The artificial skin market in India is negligible due to very high costs involved. For example, a four by four inch skin patch costs Rs 40 lakh.

5.4   Healthcare/hygiene products

Healthcare and hygiene products are an important sector in the field of medicine and surgery. They are used either in the operating theatre or on the hospital ward for the hygiene, care, and safety of staff and patients.

   5.4.1     Diapers

Baby diapers are used to absorb and retain body fluids of infants in period between birth and 24 months. The technical textile component of the diaper is the non-woven fabric which prevents fluid leakage and gives diaper the desired shape. The typical product characteristics are

• Super absorbent polymer to ensure complete dryness and prevent growth of bacteria
• The non-woven inner layer should be hydrophilic and absorb fluids fast
•  The cover should be breathable
•  Optional, leg guards to prevent leakage

The baby diapers marketed in India are primarily imported and repackaged for sale. The major brands like Huggies (Kimberley Clark Lever), Pampers (Procter and Gamble), Snuggy (Godrej-SCA) and Wipro Baby Soft cover more than 95% of the domestic market.

5.4.2     Incontinence Diapers

Incontinence diaper also known as adult diapers. It is for people with loss of bladder control which typically applies to people in the age group of 70 years and more. These diapers are disposable single use products specifically designed to absorb and retain fluids. The diapers are typically made of the absorbent material of cellulose with poly-beads to convert fluid into gel. The non-woven material is placed on top for dry feeling. The adult diapers are primarily imported by almost all companies and marketed with different packaging in the domestic market (similar to the baby diapers). The diaper market in India is growing at the rate of 25% year on year. Kimberley-Clark Lever with Depend and Godrej-SGA with Tena are the major branded players in the market.

5.4.3     Sanitary Napkin

A sandwich of an absorbent pad between fabric sheets essentially makes sanitary napkins. The technical textile component of these napkins is the non-woven fabric which prevents fluid leakage. The non-woven fabric is made up with 18-20 GSM and accounts

for around 11-12% by weight of the sanitary napkin i.e. around 0.95 to 1 grams per napkin. The major characteristics of these napkins are

•  The Super absorbent polymer which ensures complete dryness
•  Hydrophilic non-woven to absorb fluids fast
•  Snug fit
•  Breathable cover

  The sanitary napkins market in India is dominated by Procter and Gamble, Johnson and Johnson and Kimberley Clark Lever. Johnson & Johnson brand Stayfree and Procter & Gamble brand Whisper cover close to 85-90% of sanitary napkins market. Thailand accounts for around 45-50% of direct imports of sanitary napkins in India followed by Slovakia (around 30% share), China (around 15% share).

5.4.4     Surgical Disposables

The surgical disposables primarily consist of masks, caps, drapes, gowns, covers and shoe covers made of polypropylene spun bond fabric (non-woven) with or without polyethylene film. Surgical disposables are used in hospitals and pharmaceutical companies to maintain hygienic and sterile operations. These are called as surgical disposables as these are for one time use and later disposed off. In India, the majority of hospitals use cotton reusable surgical wear which needs to be sterilised after every use.

The major properties of surgical disposables are:

•  High barrier to blood or body fluids
•  Lower lint (lint is a source of infection)
•  Proven sterilisation performance
•  Comfort and breathability
•  Good bacteria filtration efficiency
•  Breathing resistance
•  Splash resistance

The surgical disposable masks and caps are made from polypropylene (PP) spun bond, spun lace and spun bond melt blown spun lace fabrics. The weight of the fabric for caps  ranges from 12 to 25 GSM and for masks ranges from 25 to 40 GSM. The disposable drapes, gowns and covers are also made of polypropylene (PP) spun bond, spun bond melt blown fabric and spun lace fabric. The weight of the fabric is typically 25-40 GSM for spun bond fabric for gowns and around 35-50 GSM for spun bond melt blown fabric for drapes and covers.

There are very few manufacturers of surgical disposable items in India. Thea-Tex Healthcare Pvt. Ltd., Mediklin Healthcare Ltd., Magnum Medicare Pvt. Ltd., Sivshree Medittex India Pvt Ltd.

6. FUTUREOF MEDICAL TEXTILES

    Technical textiles consumption under Meditech is estimated at around Rs 1,500 crore. The key Meditech product is surgical dressings which accounts for over 50% of the total technical textile consumption across Meditech segment. Surgical sutures account for around 21% of the total consumption followed by contact lenses and artificial implants with shares of around 12% and 8% respectively. The non-woven fabric in disposables accounts for 2% of the technical textile usage in Meditech segment and sanitary napkins account for 1.65%. In the medium term (next 5 years), the Meditech industry is expected to achieve growth at the rate of 8-9% year on year.

5. CONCLUUSION

   Textile materials are very important in all aspects of medicine and surgery with a wide range of applications. In reality, however, in-depth research is required to engineer a textile for even the simplest cleaning wipe in order to meet the stringent performance specifications. New developments continue to exploit the range of fibres and fabric-forming techniques which are available. It is predicted that composite materials will continue to have a greater impact in this sector owing to the large number of characteristics and performance criteria required from these materials. Nonwovens are utilised in every area of medical and surgical textiles.

Medical Textile Centers are being established to make the most of knowledge, expertise and existing collaboration with medical researchers, microbiologists, physiologists and textile scientists. Each country has its own regulations and standards for medical textiles. As  medical procedures continue to develop, the demand for textile materials is bound to grow. Growth rates are above average in developing countries as a result increases consumption in Asian and African countries than and Western market.

Web links

• www.atextechnologies.com/MedicalTextile
• www.technicaltextile.net › Articles › Medical Textiles
• www.technicaltextile.net/medical-textiles/
• textilelearner.blogspot.com/2012/02/introduction-of-medical-textiles.html
• www.techtex.ibena.d