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Things You Should Know But Are Afraid to Ask – Top 3 Open Classroom, 2019
Posted in Lectures on 31 December 2019
Yeray Trujillo Loli
General Surgery
National University of San Marcos (Lima, Perú)


How do you make surgical knots correctly?
Is it OK to make every knot in the same direction?
Is it OK to cross the edges of the suture to make the knot?

To answer these questions you must know about types of basic knots, knot combinations, knot symmetry, blocking sequences.
The half knot is made by crossing the two ends over each other in the horizontal plane and pulling both ends in opposite directions. This is called “H”.
In the half hitch, either thread plays a different role. One remains inactive (blue), and the other one, which is called the active (purple) thread, makes the knot by wrapping itself around the other thread and pulling it in an angle of 90º. This is called “S”.
The horizontal combinations of the half knot are: H1, H2 and H3. They are made when the suture is given one, two or three horizontal twists.

DANGER KNOT: the knot opens at 0 Newton of force.
SAFE KNOT: the knot has a correct blocking sequence.


How do you make a good knot?
By making half knots or half hitches using correct combinations and blocking sequences.

Is it ok to make every knot in the same direction?
Half-hitch sequences can be made in the same direction (with the lap of the needle holder around the suture). However, you should change the direction of the suture threads (90º) to make a correct blocking sequence.
Half knot sequences can be made in the same direction only when you make square knots and suture threads are pulled in opposite direction (180º)
To finish: if you make half-hitches, you should always make a blocking half hitch at the end. If you make half knots, make sure that they are all square knots.

When you pull the suture threads to adjust the knot, do you have to cross them?
If you make half hitches, it is not necessary to cross the threads.
If you make half knots, you MUST cross the suture threads to make a correct square knot. The shorter thread should always be on the same side as the hand that is making the knot.