The ultimate Aberdeen knot

Abstract

Introduction: The Aberdeen knot has been shown to be stronger and more secure than a surgeon's knot for ending a suture line. No data exist as to the ideal configuration of the Aberdeen knot. The Royal College of Surgeons of England in their Basic Surgical Skills Course, 2002 recommended six throws. The aim of this experiment is to find the ideal combination of throws and turns.

Materials and methods: Aberdeen knots of various configurations were tied in 0-PDS suture (Ethicon, Johnson and Johnson). Each configuration was tied 10 times. A materials testing machine was used to test the knots to destruction in a standardised manner.

Results: The knots were seen to behave in two ways. They either slipped and unravelled, or broke. Knots tied with fewer than three throws were unreliable. Knots tied with three throws and two turns appear to be the strongest configuration. Adding further throws and turns does not increase the strength of an Aberdeen knot.

Conclusions: An Aberdeen knot tied with three throws and two turns is the ultimate Aberdeen knot.

Figure 1

A loop or bight is formed in the suture (A), and passed under the bar. In surgery, the loop is taken as the last bight of the suture line.

Figure 2

An image of a continuous suture line showing the formation of a loop as the last bight of the suture line.

Figure 3

A further loop or bight (B), is formed in the working end and passed through the loop A.

Figure 4

The second bight being passed through the first, as described in Figure 3.

Figure 5

The bight B has been passed through A. This is called a throw. This step can be repeated any number of times to give varying numbers of throws.

Figure 6

Another bight being passed under the newly formed loop to form 2 throws.

Figure 7

To finish the knot, the end of the suture, C, is then passed through the new loop formed by the previous bight, B. This is called ‘one turn’.

Figure 8

(A,B) Images of finishing the knot with either 1 or 2 turns. Up to 3 turns were tested in this experiment.

Figure 9

This final step can be repeated by passing the working end, C, under the bight B twice to give a knot configuration of one throw and two turns.

Figure 10

Bar chart of average breaking force for Aberdeen knots with number of throws specified.

Figure 11

Mean and standard deviation for each configuration of Aberdeen knot.

Figure 12

Mean breaking force for each group. Note, there is no error bar for Group 1, as it only contains a single data point.

Figure 13

Average breaking force for Aberdeen knots with number of turns specified.