07.04-07 Knot Tying
Any description makes knot tying sound more difficult than it actually is. Do not be discouraged if you find it difficult at first - almost everybody does. The best way to develop a dependable technique for tying safe, reliable knots is repeated practice of the processes covered in this module.
You will learn how to tie a reef knot, surgeon's knot and Aberdeen knot, as well as how to tie at depth and in a confined space.
In this module
07.04 The Surgeon's Knot
The surgeon's knot is a simple modification to the reef knot and is used to achieve extra security. It can be tied with an instrument, or by hand. Many surgeons use this knot routinely when tying with an instrument, rather than a standard reef knot.
It is particularly useful when using synthetic monofilament sutures such as Prolene, which can be very springy due to their inherent memory. It is also useful where slippage could be a major issue, for example when tying a vessel at depth.
The knot may look cumbersome, but it is very secure.
07.04.01 Principles Video 1
With an instrument tie, the thread is looped twice around the needle holder for the first throw only. This adds friction which will give extra grip and prevent the knot from coming undone.
With a hand tied knot, the extra friction is achieved by making an additional twist in the first throw only.
07.04.02 Principles Video 2
When using monofilament sutures such as Prolene which are difficult to tie, many surgeons use more than two throws to avoid slippage. In this example, the surgeon uses three throws. Some surgeons even use a surgeon's knot for their final throw, rather than the first, to achieve the friction that they need.
07.04.03 Practise Instrument Tie
To practise an instrument tied Surgeon’s knot, you won’t need to use the whole length of your practice thread. Start by placing the white end of your practice thread under the knot trainer strings, with the free end furthest away from you. Hold the long end of the thread between your left thumb and index finger, approximately 6 cm into the red section.
With your needle holder in your right hand, twist the thread in a forward direction twice around it so that a loop is formed. Pick up the free end of the suture with the needle holder and bring it back through the loop towards you, simultaneously pushing the long end in your left hand away from you. Pull until the knot lies flat on the trainer. Release the free end of the suture.
For the second throw, loop the thread round the needle holder once in a backward direction, i.e. towards you. Tighten by pushing the free end with the needle holder away from you and pulling the long end in your left hand towards you. Release the free end of the suture.
For the third throw, loop the thread once forward around the needle holder. Tighten by pulling the free end in the needle holder towards you and pushing the long end in your left hand away.
07.04.04 Practise Hand Tie Video 1
Place the practise thread under the knot trainer strings with the white end to the left, then cross the two ends over the top of the trainer strings so that the red end is on the left and the white on the right. This will avoid you having to cross your hands over when tightening the first throw.
Hold the white end between your right thumb and middle finger and the red end between your left thumb and index finger. Using your extended right index finger push the white thread over and across the red thread. Take your right index finger down through the loop that has now formed and grasp the red thread. Rotate your index finger to loop the white thread round the red. Hold the loop open with your left thumb and index finger and take the white thread round the red a second time with your right index finger. Now pull the thread through and pull your hands apart to apply horizontal tension and tighten. This completes the first throw.
07.04.05 Practise Hand Tie Video 2
The second throw is made with your middle finger in exactly the same way as for a standard hand tied reef knot. There is no additional twist. To tighten, rotate your hands by 90 degrees so that you are pulling the left (red) thread towards you and the right (white) away from you.
The third throw is made with your index finger and tightened in the opposite direction to the second, by pulling the left (red thread) away from you and the right (white) thread towards you.
07.05 Aberdeen Knot
The Aberdeen knot is useful when, having finished a continuous suture, you are left with a loop and a free end. It is usually tied by hand. It has been found to be stronger and more secure than a surgeon’s knot.
Although it is not feasible to practise this type of knot using your knot tying kit, you will have the opportunity to practise it on your skin pad when you reach the chapter on Continuous Sutures in the Suturing Techniques module.
07.05.01 Principles
When completing your last continuous suture, rather than pulling it all the way through a loop of suture should be left. The loop is then displayed between the index finger and thumb of one hand and the free end is held between the index finger and thumb of the other.
The free end is grasped through the loop and pulled so that a new loop forms. The new loop and the free end are pulled in opposite directions so that the old loop is flattened and eliminated.
This process is repeated up to a maximum of seven throws. Finally the free end is passed through the loop, tightened down and cut to complete your Aberdeen knot.
07.06 Tying At Depth
There will be occasions when you will need to tie at knot at depth and in a confined space, for example when tying off a blood vessel deep in the pelvis. This is best achieved using a hand-tied knot. To practise this technique you will need to assemble the cylinder and hook that are part of the knot tying kit in your Hands-on Kit using the skin pad jig as your base.
- Moisten both sucker feet with a little water. Place the jig on the work surface and push down along the centre of it. Make sure the feet have stuck securely by trying to move the jig
- Slide the base plate (with the magnet facing upwards) under the long sides of the skin pad jig
- Insert the long edge of the top plate (with the hole) under one edge of the skin pad jig
- Gently push the other edge of the top plate into the skin pad jig so that it 'pops' under it and forms a convex shape with the hole at the apex
- Curve round the long flat sheet and insert the tab through the double slits to start forming the depth tying cylinder. Hold this tab in place
- Insert the other tab into the remaining slit
- Push the cylinder into the hole in the top plate
- Attach the magnetic hook to the base plate. The hook represents an object to be ligated
There are 2 strength levels for the magnetic hook:
- for maximum strength, the hook attaches directly to the base plate. This represents tough tissue and is good for your first attempts at tying within a confined space: it takes quite a lot of force to separate the hook from the base
- for less strength, place the spacer (the circular plastic disc) over the magnet on the base plate and then attach the magnetic hook. This represents more delicate tissue and the hook will come away from the base plate with little force
- Now take the two coloured knot tying cord from the basic knot tying kit to represent your suture material. You are ready to start practising!
07.06.01 Tying At Depth Practise
Pass the suture material around the hook, either using artery forceps or your right index finger. Be careful not to exert any tension on the hook.
Bring the suture material out of the cavity, and make a standard reef knot throw on the surface. Again, try to avoid exerting any tension on the hook, as this will cause it to lift up from the base.
Snug the knot down into the cavity using your right index or middle finger, keeping tension on the strand in your left hand. Make sure there is no traction or pull on the structure being ligated.
Tie a further throw outside the cavity. Push it into the cavity and snug it down, again using your right index or middle finger. Tighten it by counter traction against the finger.
Tie a third throw for security and snug it down into the cavity.
07.07 Things to Avoid
The next five videos cover the most common problems encountered when learning to tie knots.
07.07.01 Granny Knot
As well as knowing how to tie a reliable knot, it is equally important to be able to recognize and avoid unreliable knots. A granny knot is asymmetrical and insecure. It becomes twisted as it is tightened. This increases the risk of the suture material breaking when tying the knot, particularly when using monofilament sutures.
A granny knot is caused by failing to change the direction of throw in the second stage. In this example, the thread is looped forward around the needle holder for both the first and second throw.
07.07.02 Slip Knot
Never use a slip knot for suturing. It is dangerously insecure and will tend to come undone on its own.
A slip knot is caused by failing to change the direction of pull in the second stage in spite of correctly changing the direction of throw.
07.07.03 Insufficient Throws
A single reef knot is never sufficient when you are suturing. Build up several throws, each forming a reef knot with the one before. The minimum is three throws, and more are required for springy sutures like monofilament. Five throws are usually enough.
07.07.04 First Throw Coming Undone
Monofilament synthetic sutures are springy and can be difficult to tie. The first throw tends to come undone. To avoid this problem, use a surgeon's knot, with an extra twist in the first throw, rather than a standard reef knot.
An alternative is to try 'tweaking' the throw. Pull firmly on the suture end in your non-dominant hand while giving a sharp tug towards it with your dominant hand. This secures the knot temporarily while you make the second throw.
07.07.05 Damaging the Suture
The simple structure of monofilament sutures means they must be handled very carefully to avoid damage and weakening of the strand. When tying with an instrument, only the ends of the sutures should be handled with your instrument.