Properties of Suture Material
Suture materials have been evolved since millennia and being researched to achieve a perfect suture material. Wide variety of sutures and manufacturers or brands is available. Surgeon’s choice and economics both are important and familiarization with suture material’s properties is also important.
General considerations:
An ideal suture material should have following characteristics/ properties
- Sterile and easy to sterilize (without alterations in its tensile strength and other physical and chemical characteristics)
- Remain intact until union occurs
- Causes minimum tissue reaction (non-electrolytic, non-allergic, non-carcinogenic, non-toxic) or bioinert in nature
- Be non-capillary in action / lacking the wick effect
- Easy to handle
- Uniform in thickness (along complete length) or fine
- Sufficient tensile and functional strength (along all of its length)
- Easy knot tying and knot security (no tendency to slip, loosen or swell due to wetting)
- Resistant to infection
- Cheap / economical / inexpensive and readily available
- High tensile strength
- Predictable / favorable absorption profile
- Visibility – should be easily visible in surgical field
- Support the incision while it heals
- Should have smooth surface – The material should pass through the tissues to be apposed without friction or cutting.
- Conforms to the tissue (not conform the tissue to it) – The material should pass through the tissues to be opposed without friction or cutting.
- An ideal suture material should not predispose the animal to oedematous or inflammatory swelling, pain, febrile reaction, loss of function, infection and delayed wound healing.
The ideal suture is the smallest possible to produce uniform tensile strength, securely hold the wound for the required time for healing, then be absorbed. It should have predictable absorption profile, easy to handle, produce minimal reaction, and knot securely.
After going through the points mentioned above it is well understood that it is extremely difficult to manufacture a perfect suture material which can meet all ideal qualities and criteria in all situations. However, polydioxanone, a monofilament synthetic absorbable material, fulfils many of these characteristics to make it almost ideal.
A wide variety of suture materials is available which offers unique characteristics. Different types of sutures are available for specific types of the surgical procedures. An understanding of properties of suture materials help guide rational selection for a particular surgery / tissue/ organ or application. Most of the suture materials available in the market are synthetic fibers and have disadvantages and advantages. Visibility of suture material is important in selection of the thread. Color of the suture varies from clear, white, light tan, blue, purple, green or black. Light coloured sutures are easy to differentiate during removal in dark coloured patients and vice versa. It is important because animals and human patients both sometimes have dense hair coat and studies shows that shaving hair actually increases the risk of wound infection.
“The best suture for a given laceration is the smallest diameter suture, which will adequately counteract static and dynamic tension forces on the skin.” – Brian Lin
An ideal suture material should not predispose the individual to oedematous or inflammatory swelling, pain, febrile reaction, loss of function, infection and delayed wound healing. An ideal suture is the smallest possible to produce uniform tensile strength and securely hold the wound for the desired time until healing occurs and then absorbed or removed without harmful effects or tissue reaction. One have to choose most appropriate suture material from the large variety of available based on the –
- Tissue being sutured and healing duration
- Disease and the patient factors
- Procedure
- Personal choice
- Availability
Use of the wrong suture material / pattern or wrong choice of suture material may lead to dehiscence of the wound/ surgical incision or dehiscence of sutures before the healing takes place, infection at the site, failure of surgical implants, haemorrhage or other complications and sometimes may need a corrective surgery which may increase the cost of the procedure and risk both.
Terms Related to Suture Properties:
Breaking strength – it is the limit of tensile strength or force at which suture breaks or wound edges separate.
Capillarity – action due to capillaries between threads of a multifilament suture which allows body fluid to be absorbed and may lead to infection
Elasticity – Measure of the ability or degree of the material to gain its original form or length after deformation or stretching (Silk). High elasticity sutures should be used in the oedematous tissues or areas.
Knot strength / Knot pull strength – it is important to secure a suture in place and defined by the amount of force necessary to cause a knot to slip. More important to consider when ligating the arteries.
Straight pull strength – It is considered for barbed suture materials. They don’t need to be knotted at the end of finishing of suture pattern or closing of wounds.
Memory or suture stiffness– Inherent capability of suture to return to or to maintain its original gross shape. High memory sutures are stiff, difficult to handle, and unties easily. e.g. – Polypropylene
Ease of handling, memory, and knot strength/knot holding ability are determined by whether it is monofilament or multifilament suture. It is common with monofilament sutures to be smooth, stiff, and have high memory. This sometimes leads to dreaded knots accidentally while performing a running or continuous suture pattern. And slickness of the suture needs extra square knots while securing a surgical knot.
Plasticity – it is a measure of the ability to deform without breaking and to maintain a new form after relief of the deforming force – e.g. polypropylene has good plasticity.
Pliability – Ease of Handling
Tensile strength – related to suture size, Amount of tension/weight, or pull the suture can withstand before it breaks. Important to consider in areas of tension like linea alba. An ideal suture material should possess and maintain adequate tensile strength till healing is achieved: be non-capillary, non-carcinogenic, non-allergic and non-electrolytic.
Configuration – monofilament has less risk of infection due to lack of capillary action. Braided multifilament sutures are easier to handle and tie.
Tissue reactivity – inflammatory response to the suture. Undesirable since inflammation worsens the scar. The reaction is at peak in first 2 to 7 days. Sutures of animal origin like catgut and silk are more tend to elicit intense inflammatory reactions in comparison to synthetic suture material.
Visibility – it is important in a surgical field in order to distinguish and see the suture material. Sutures come in clear form or in colours like white, or light tan. Blue, purple, green, or black coloured suture materials are highly visible.
Fluorescent suture material is also available. Non-absorbable monofilament propylene sutures are coated with fluorescent material (e.g. Fluorofil and Glostitch)