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Why do we suture wounds?
Why do we suture wounds?
The main aims of closing a wound with sutures are to:
The main aims of closing a wound with sutures are to:
Eliminate any dead space - a space for potential infection or bleeding leading to a haematoma.
Support the wound until tensile strength is recovered. This helps prevent wound dehiscence.
Allow skin edges to be accurately approximated to produce a wound that is both cosmetically and functionally acceptable. This is known as primary intention.
Prevent healing by secondary intention which may result in an unacceptable scar, both cosmetically and functionally.
Reduce bleeding and infection.
NB this is more specific for skin closure, however, closing deeper layers and their respective suture uses are also discussed below.
Sutures can be categorised by whether they are absorbable or non-absorbable, synthetic or natural or if they are monofilament or multifilament (braided). In surgery today, the majority of sutures are synthetic.
Absorbable vs Non-absorbable
Absorbable vs Non-absorbable
Absorbable
Absorbable
Absorbable sutures such as Vicryl, Polydiaxonone (PDS), and Monocryl are gradually broken down by the body via enzymatic reactions (proteolytic enzymatic degradation) or hydrolysis, which is then absorbed by the body. As a result, absorbable sutures lose a significant amount of their tensile strength within 60 days of tissue insertion.These sutures are suitable for tissues that heal rapidly such as the stomach, bowel, bladder and subcutaneous tissues. They retain their tensile strength during the initial tissue mending process, and as tissues heal, the suture strength declines at a known rate for each specific material type. Absorbable sutures are also commonly used for subcuticular wound closure which can produce superior cosmetic results.
The complete absorption times for the more commonly used absorbable sutures are summarised below, although these times may vary due to factors such as ongoing infection, fever, or even protein deficiency.
Vicryl rapide - 7-10 days
Vicryl - 60 days
Monocryl - 100 days
PDS - 200 days
Non-absorbable
Non-absorbable
Non-absorbable sutures are synthesised from a variety of non-biodegradable materials such as nylon (Ethilon), prolene and silk. Contrastingly, they maintain their tensile strength within tissue for at least 60 days. These sutures are suitable for repair of tissues with slow healing times such as ligaments and tendons as they offer longer term tissue approximation. They are also used in blood vessel repair and vascular anastamoses with grafts, as well as fixation of hernia meshes.
Non-absorbable sutures can be utilised for skin closure, particularly where skin opposition is placed under tension or there is a risk of infection. For this, interrupted suturing technique is the technique of choice as removal of one or two stitches would not affect the wound healing process down or upstream. However, non-absorbable sutures for skin closure will require removal post-operatively, usually between three to fourteen days depending on the healing potential of the patient and the location of the wound (which is discussed below).
Synthetic vs Natural
Synthetic vs Natural
Synthetic
Synthetic
These sutures consist of materials which are man made. As a result, their properties such as tensile strength and absorption can be calculated and predicted more accurately. This allows for wounds to be better managed, giving surgeons reassurance of the behaviour of the suture chosen in situ. These can be absorbable (Vicryl, Monocryl & PDS) and non-absorbable (nylon(Ethilon) & prolene).
Natural
Natural
Natural sutures are made of natural fibres derived from biological sources such as catgut or silk. Despite this, they are becoming less favoured as they can produce unwanted inflammatory reactions, comprimising wound healing. However, silk is still largely used for securing surgical drains. Natural sutures can be absorbable (catgut & collagen) or non-absorbable (silk, steel & cotton).
Monofilament vs Multifilament (Braided)
Monofilament vs Multifilament (Braided)
Monofilament
Monofilament
Monofilament sutures consist of a single strand. They manoeuvere smoothly through tissue with minimal tissue drag (friction) and harbour lower rates of infection due to the absence of pockets of spaces which bacteria favour. Some examples include: nylon (Ethilon), PDS and prolene.
However, monofilament sutures pose decreased knot security due to some of them having a tendency to maintain its original form, therefore, additional knots are required to reduce the propensity for the knot to unravel. Also, these suture types can be significantly weakened by any form of damage, either by kinks or by the surgical instruments. Monofilament sutures are largely preferred in vascular, tendon and nerve repairs
Multifilament (Braided)
Multifilament (Braided)
These types of sutures are composed of several fibres twisted together into a single strand. Braided sutures are generally stronger and allow for better knot security, but tend to produce more tissue drag. This can be overcome with many manufacturers applying coatings to reduce tissue drag, however also comprimising knot security. Some examples include braided silk and Vicryl.
The intervening spaces that come as a result of these braids can be ideal for bacterial gowth, and can lead to bacteria tracking into the wound, known as suture track sepsis. infection can persist due to these bacteria being isolated from the immune system. Therefore, is is vital that multifilament sutures are not placed in contaminated areas. Multifilament sutures are particularly preferred in bowel surgery.
Suture Size
Suture Size
The size of a suture represents its diameter, which has a very close relationship with its tensile strength and handling properties. Historically, when sutures were thicker, size 1 was ascribed to the finest suture. As technology proggressed sutures became thinner, therefore this scale needed adjusting and was taken backwards.
Essentially the sizing follows a scale similar to negative and positive numbers. A number to the right of 0 (or not preceded by a 0) means the suture size gets progressviely larger. For example, a size 3 suture is larger than a size 2 suture, which is larger than a size 1. Conversely, a number to the left of 0 means the suture size gets progressively smaller. For example, a 4-0 suture is smaller than a 3-0 suture, which is smaller than a 2-0. This is known as the United States/British Pharmacopeia Classification (USPC/BPC). This is further highlighted below with their respective uses within different tissue.
11-0 to 10-0 - Used mainly for microvascular surgery
10-0 to 8-0 - Used for delicate procedures such as ophthalmic surgery or nerve repairs
7-0 to 6-0 - Used for facial plastics or small vascular repairs
5-0 to 4-0 - Used for larger vascular repairs or skin closures
3-0 to 2-0 - Used for muscle layers or wounds especially when there is high tissue tension
0 to 1 - Used for deep layers in the back, fascia layers in the abdomen (laparotomy closures) or joint capsules
2 to 5 - Used for tendon repairs
When choosing the size of your suture, the surgeon will choose the smallest size required to adequately keep the wound closed in order to minimise trauma to the tissue. Bearing in mind that as sutures get smaller, tensile strength decreases too.
Removal Times for Non-absorbable Sutures
Removal Times for Non-absorbable Sutures
The length of time that stures are left in-situ is largely dependant on the site of the body where the wound is located. Areas such as the face contain a superior blood supply, allowing for faster wound healing. Therfore, sutures placed here can be removed earlier. Alternatively, other anatomical sites such as the back have a poorer blood supply with tougher skin, slowing down wound healing. Hence sutures here will be required for longer before removal. The table below demosntrates the removal times based on different anatomical sites.
It is important to take into other factors that can significantly impact on wound healing. Patient factors include age, nutritional status and immunocomprimisation. Surgical factors include the gross surgical technique, choice of suture material and technique.
This table from Geeky Medics summarises the recommended suture size, material type, and removal time based on specific anatomical sites.
Anatomy of a suture packet
Anatomy of a suture packet
Self-directed Learning
Self-directed Learning
In addition to the topics covered, it is important to review the following topics to fully complement your suture theory.
Anatomy of the skin
Stages of wound healing
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