Comparison of knot-tying proficiency and knot characteristics for square and reversing half hitch alternating-post surgical knots in a simulated deep body cavity among novice medical students

Abstract

Background: Proficiency-based knot-tying curricula have been developed for square knots for medical students, but, to our knowledge, no such curriculum exists for the reverse half hitch alternating-post (RHAP) knot. We aimed to compare medical students' knot-tying proficiency, knot-tying self-confidence and final knot characteristics for RHAP and square knots in a simulated deep body cavity. Methods: We performed a within-subject prospective crossover study of novice medical students who received 30 minutes of training in tying both RHAP and square knots. Participant performance was assessed via a knot-tying checklist, and knot configuration, tensile strength, tightness (loop circumference) and mechanism of failure were also assessed. Participants' self-reported confidence in knot tying was captured. Results: Twenty-one students participated in the study. Mean scores on the knottying checklist were significantly higher for RHAP knots than for square knots (6.9 [standard deviation (SD) 2.1] v. 5.2 [SD 2.3], p < 0.01), and RHAP knots were significantly tighter than square knots (46.8 mm [SD 0.4 mm] v. 49.3 mm [SD 0.7 mm], p < 0.05). There were no differences between RHAP and square knots in correct knot configuration, breaking strength or mechanism of failure. Reverse half hitch alternating-post knots were easier to tie within a deep-body cavity, whereas square knots were easier to learn. Conclusion: Novice medical students were more proficient in tying RHAP knots than square knots in a simulated deep body cavity. Students were able to construct RHAP knots more securely and reported increased confidence in tying RHAP knots at depth compared to square knots.

Evaluating bowel enterotomy closures in simulated deep body cavities using the reversing half-hitch alternating post and square knots: a randomized controlled trial

“…Third, we did not perform microscopic examination of square knots and RHAP knots to identify loose or slipped knots on the enterotomy repair specimens because we wanted to mimic the setting of the operating room, where it may be difficult to assess the presence of loose or slipped knots. Our previous work 7 showed no difference in the frequency of slipped RHAP versus square knots when constructed at depth. Fourth, we used braided nonabsorbable 2–0 silk sutures for enterotomy repairs.…”

“…Our results demonstrate that enterotomy repairs in simulated deep body cavities are faster to perform and more secure with the RHAP knot than with the square knot. We have previously shown that the RHAP knot is easier for novices to learn to tie at depth, 7 and we now hypothesize that the reduced complexity of the RHAP knot allows the learner to focus their attention on repairing the enterotomy rather than on tying the knots. Our hypothesis is supported by the observed deterioration in performance (burst pressure) seen in the square knot group when participants transitioned from a flat surface to a simulated deep body cavity.…”

“… 3 , 4 , 6 Step-by-step details on how to construct this knot can be found in our previous publications. 6 , 7 We have previously shown that the RHAP knot exhibits equivalent tensile strength to square knots. 3 , 6 We have also shown that RHAP knots are easier for medical students to learn and to tie at depth than square knots in a simulated setting.…”

“… 3 , 6 We have also shown that RHAP knots are easier for medical students to learn and to tie at depth than square knots in a simulated setting. 7 These capabilities suggest that this knot-tying technique may be useful for learners in surgery to perform while perfecting new surgical techniques. The next step toward generalizability of the RHAP knot in medical education is to assess the quality of this knot in more clinically relevant scenarios.…”

Does quality of novice hand-tied square knots improve with repetition during a single training session?

“…The amount of extension under preload provides a measure of loop security ( Luenam, Koonalinthip & Kosiyatrakul, 2019 ). Surgeon and trainee loops extended by a maximum of 0.79 mm and 1.30 mm with preloading, respectively, indicating an initial tightening of throws within an acceptable margin of slippage (<3 mm elongation) for both groups of participants and a greater degree of loop security for surgeons ( Wasik, Cross & Voss, 2013 ; Luenam, Koonalinthip & Kosiyatrakul, 2019 ; Wu et al, 2018 ). Some extension of the loop circumference is expected with tightening when a surgeon’s throw is used ( Zimmer et al, 1991 ).…”