In vitro comparison of secure Aberdeen and square knots with plasma- and fat-coated polydioxanone

Objective: To determine (1) the minimum number of throws to form secure Aberdeen (AB) and square knots to start (SS) and end (SE) continuous patterns, in fat- and plasma-coated polydioxanone; and (2) compare relative knot security (RKS) and knot volumes of these secure SS, SE, and AB knots. Study Design: In vitro experimental materials testing. Sample Population: Polydioxanone suture material (3 metric). Methods: Each knot was tested 20 times, and throws incrementally added until secure SS, SE, and AB knots were found. RKS and knot volumes were calculated for SS, SE, and AB knots. Results: Secure SE knots needed 5 throws in plasma or fat. Secure SS knots needed 4 throws in plasma, but 5 in fat. The minimum AB configuration that was secure in plasma or fat was 3+1, however, the 4+1 AB knot was also secure in fat. Mean (SD) RKS of secure knots were: SE 59.69% (5.91), SS 67.92% (12.50), AB 81.08% (8.99). AB knots had significantly higher mean RKS than any SS or SE knot in plasma or fat (P<.001). Mean knot volume of 3+1 AB knot was significantly smaller than any secure SS or SE knots by 22.6–69.4% (P<.0001). Mean knot volume of 4+1 AB knots was significantly smaller than all fat secure SS and SE knots by 19.9–57.5% (P=.0001). Conclusion: The knot security of the SS knot was decreased by fat coating polydioxanone suture, requiring an additional throw to keep it secure. Secure AB knots had a higher breaking strength and smaller knot volume than secure SS and SE knots. Clinical Relevance: The AB may be preferable to square knots in continuous closures. As many body fluids contain lipid, surgeons should tie knot configurations considered secure in fat. We advise tying a 4+1 AB and placing a minimum of 5 throws to tie SS and SE knots using 3 metric polydioxanone.

Olaf Schaaf, Mark Glyde and Robert E. Day