Suturing and knot-tying techniques in microsurgery: anastomosis time, learning curve and scanning electron microscopic assessment

BACKGROUND: Various suturing and knotting techniques exist to enhance microsurgical efficiency, yet a comprehensive comparison is lacking. This study evaluates two suturing (interrupted vs. open-loop) and two knot-tying (conventional vs. airborne) techniques to determine how anastomosis time is apportioned between them. METHODS: Seventy-two femoral artery anastomoses were performed on 36 female Wistar-albino rats by nine microsurgeons, stratified into three groups (<1, 1-4, >4 years experience). The four combinations were interrupted or open-loop suture with conventional or airborne knot (IS-CK, IS-AK, OLS-CK, OLS-AK). Each surgeon performed all four before and after a standardised practice session, making technique and practice within-subject factors and experience a between-subject factor, analysed by split-plot repeated-measures ANOVA. Twelve anastomoses from the most experienced group were examined by scanning electron microscopy (SEM), blind to technique and operator. RESULTS: The knot-tying method, rather than the suturing technique, was the principal factor associated with anastomosis time. Conventional knotting was approximately 11 min faster than airborne knotting (666 s; p < 0.001), whereas the two suturing techniques differed by 18.6 s within conventional knotting (p = 0.46) and 82.3 s within airborne knotting (p = 0.005) - approximately 1% and 4% of total time. Experience dominated (51.2 vs. 13.3 min; 3.85-fold; p < 0.001). All techniques improved after practice, and the improvement depended on the technique (F(3,18) = 8.30, p = 0.001): approximately 15% for the airborne-knot techniques vs. 5-10% for the conventional-knot techniques. SEM showed a dissociation: suture spacing was determined by the suturing technique (open-loop superior, p = 0.001) and knot quality by the knot-tying technique (airborne superior, p < 0.001); neither affected suture-tissue interaction (p = 0.77). CONCLUSION: In elective, uncomplicated anastomoses the knot-tying technique, rather than the suturing technique, was most strongly associated with anastomosis time, while surgical experience outweighed both. The airborne knot costs approximately 11 min but yields better knot quality and improves most with practice; the open-loop suture gives more regular suture spacing at negligible time cost. Technique selection is therefore a trade-off between ischaemia time and technical refinement, informed primarily by the operator's experience. Grant sponsor: Çanakkale Onsekiz Mart University Scientific Research Projects Coordination Unit. Grant number: TTU-2024-4668.