TissueDB/Simulators/Knot Tying Force-Feedback Simulator (Amiel)

The Knot Tying Force-Feedback Simulator (Amiel) ("Knoti") is a low-cost, bench-top force-measurement device built from a hook, a data sensor and a feedback unit wired to a computer, for practising one-handed square knot tying in vessel ligation.^[1] As the trainee ties a knot, it signals in real time when the pulling force rises above 1.3 N, the maximum force expert surgeons use, so novices learn to tie a secure knot without tearing the thread or avulsing the vessel.

Sources: Amiel et al. 2020 (Am J Surg), Amiel et al. 2019 (Surgery) and Laufer et al. 2016 (Stud Health Technol Inform).

Amiel et al. (2020) is a validation study and does not give a construction procedure; the device's hardware is documented in Laufer et al. (2016) and Amiel et al. (2019), which were not staged for this page. The steps below describe the four components and how they relate (from Fig. 1 and the text) — they are not a verified build sequence from the source.

1. The hook (component A), where the knot is tied. Material and dimensions are not specified.
2. The plexiglass tube (component B), placed over the hook so the top of the tube sits 3 cm above the top of the hook.
3. The data sensor (component C) connects to a personal computer with a USB cable. Amiel et al. 2020 does not give its type, dimensions, force range or sample rate.
4. The feedback unit (component D) carries red and green lights and an alarm circuit set to the 1.3 N threshold. Amiel et al. 2020 does not give the circuit schematic.

The source gives no assembly procedure; the arrangement below is read from Fig. 1.

1. The hook (A) is mounted on a base platform (visible in Fig. 1; material and dimensions not specified).
2. The plexiglass tube (B) sits over the hook so the top of the tube is 3 cm above the hook.
3. The data sensor (C) measures the vertical reaction force at the hook and connects to a computer by USB cable.
4. The feedback unit (D) sits beside the hook-and-tube assembly and is driven by the sensor's reading against the 1.3 N threshold.

1. Launch the logging software and confirm the computer is reading the sensor over USB.
2. Tie a test knot (3-0 silk, one-handed square-knot technique) on the hook inside the tube.
3. Confirm the green light and intermittent beep when the reaction force is below 1.3 N.
4. Confirm the red light and persistent beep when the reaction force is above 1.3 N.
5. Confirm the software logs total force, peak pulling force, peak pushing force, and completion time for the knot.

The simulator trains one-handed square knot tying for vessel ligation with vertical-axis force feedback. Beyond that scope:

• Lateral or multi-axis force measurement — the sensor measures the vertical axis only, a limitation the authors note.
• Knot integrity testing under load — knot quality was judged visually by an examiner, not by tensile testing.
• Trainees outside the tested group — the 2020 training-efficacy study enrolled only 14 PGY 1-2 surgical residents; it was not run with medical students or attending surgeons.
• Tissue-model fidelity — the 1.3 N target was derived from expert performance, not from tissue models that measure tear forces.

Sources consulted for this page but not cited at a specific claim:

• Amiel I, Anteby R, Cordoba M, Laufer S, Shwaartz C, Rosin D, Gutman M, Ziv A, Mashiach R (2020). "Feedback based simulator training reduces superfluous forces exerted by novice residents practicing knot tying for vessel ligation." American Journal of Surgery 220(1):100–104. DOI: 10.1016/j.amjsurg.2019.11.027. PMID: 31806168.
• Amiel I, Anteby R, Cordoba M, Laufer S, Shwaartz C, Rosin D, Gutman M, Ziv A, Mashiach R. "Experienced surgeons versus novice surgery residents: validating a novel knot tying simulator for vessel ligation." Surgery 2020;167(4):699–703 (first published online 2 November 2019). DOI: 10.1016/j.surg.2019.09.017. PMID: 31685234. Construct-validity study (15 experts vs 30 residents) establishing the ~1.3 N expert force threshold.
• Laufer S, Amiel I, Nathwani JN, Mashiach R, Margalit RS, Ray RD, Ziv A, Pugh CM (2016). "A Simulator for Measuring Forces During Surgical Knots." Studies in Health Technology and Informatics 220:199–204. PMID: 27046578. Original Knoti device hardware description.