Original reportOperating Room Fatigue: Is Your Twentieth Surgical Knot as Strong as Your First?
Introduction
Indisputably, knot integrity is an essential part of any surgical procedure. We completed a search of the literature (MEDLINE; January 1966—April 2011; English language; search terms; “suture,” “knot security,” “knot integrity”) and noted several gaps in the literature. Previous studies have examined variables affecting knot strength, such as suture type, suture end length, number of throws, and tying modality.1, 2, 3 Interestingly, intraoperator variability has not been examined critically as a variable in knot tying. It is not currently established whether knot strength is affected by the order in which a knot is tied, over a short period, similar to a hysterectomy.
This project was undertaken in an attempt to determine whether muscle fatigue would affect the operator and how this would be reflected in the tensile strength of the suture/knot. Muscle memory could also play a role if knot strength progressively increases with the number of knots tied. Our objective is to determine the intraoperator variability of tensile strength in a series of 20 consecutively tied knots.
Section snippets
Materials and Methods
Polyglactin 910 (Ethicon, Inc, Somerville, New Jersey) is a common suture material used for vaginal hysterectomy.4 Nonexpired 0-gauge United States Pharmacopeia suture was used. A metal hex head screw model with the screws 50 mm on center was used to tie the suture.5
The knots were tied without a surgeon's knot and 4 additional square knots (1 = 1 = 1 = 1 = 1).6 A knot was tied then the surgeon started tying the first throw of the next knot less than 20 seconds later to simulate the time needed
Results
A total of 400 knots was tied in 20 sets of 20 knots each by each surgeon. All the sutures broke at the knot and 36% were untied. For each knot, the Newtons at failure were measured, and the failure type (untied in contrast to broke) was recorded. For analyses, the data for each series of knots were collapsed into quartiles (ie, knots 1-5, 6-10, 11-15, and 16-20). Table 1 displays the descriptive statistics for each series of knots.
Discussion
This laboratory experiment showed that the surgeon's first knot has a similar tensile strength as the 20th when tied with polyglactin 910 sutures. This would infer that fatigue does not influence the tensile strength for a series of 20 knots; however, additional study with more knots series and a wider variety of surgeon experience may be warranted.
Surgery is a physically demanding task. Tachycardia may be considered as an appropriate response induced by the physical or psychological stress of
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