The importance of rotation to teach secure half-hitch sequences in surgery.

Background: Knot security of half-knot (H) sequences varies with rotation, but half-knots risk destabilisation. Objectives: To investigate the rotation of half-hitch (S) sequences on knot security. Materials and Methods: The loop and knot security of symmetrical and asymmetrical sliding and blocking half-hitch sequences was measured using a tensiometer. Results: Loop security of symmetrical sliding half-hitch sequences is much higher than asymmetrical sequences, increasing from 6+2 to 21+2 and from 27+6 to 48+5 Newton (N) for 2 and 4 half-hitches respectively (both P<0.0001). Symmetrical sliding sequences are more compact and remain in the same plane, squeezing the passive thread, while asymmetrical sequences rotate loosely around the passive end. Blocking sequences are superior when asymmetrical since changing the passive end acts like changing rotation, transforming the asymmetrical sliding into a symmetrical blocking half-hitch on the new passive thread. The knot security of 2 sliding and 1 blocking half-hitch doubles from 52+3 to 98+2 N for the worst (asymmetric sliding and symmetric blocking, SSaSsb) or best rotation sequences (SSsSab). Adding a second asymmetric blocking half-hitch (Sab) increases security further to 105+3 N. The overall knot security of four-throw, correctly rotated, half-hitch (SSsSabSab) or half-knot (H2H1sH1s, H2H2a and H2H2s) sequences is similar for four suture diameters. Conclusion: Rotation affects the security of half-hitch sequences, which should be symmetrical when sliding, and asymmetrical when blocking. What is new?: Half-hitch sequences are clinically superior to half-knot sequences. They do not risk destabilisation, and loop security improves approximation of tissues under traction, permitting tight knots.