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 strain-gauge sensor, and an LED-and-buzzer feedback unit wired to a computer, for practising one-handed square knot tying in vessel ligation. 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.[1][2]
| Field | Details |
|---|---|
| Features and Basic Operation | The device has four parts: a hook where the knot is tied (A); a clear plexiglass tube over the hook that recreates the depth of a deep surgical field (B); a strain-gauge sensor that measures the vertical reaction force and logs it to a computer over USB (C); and a feedback unit with red and green LEDs and a beeper (D). As the trainee ties a knot, a green LED and intermittent beep mean the pulling force is below 1.3 N; a red LED and continuous beep warn when it exceeds 1.3 N — the maximum force expert surgeons use, from the developers' 2019 study.[1][2] The software logs total force, peak pulling and pushing force, and completion time for each knot.[1] Buildability note: The parts are inexpensive, but this is not a build-from-local-materials trainer — it needs a strain-gauge load cell, a microcontroller, an LED-and-buzzer circuit, and a computer running the logging software. |
| Current Development Status | Built and validated by its developers — construct validity and a training benefit shown in published studies (Amiel et al. 2019, 2020); operating-room skill transfer not yet demonstrated.[2][1] |
| Estimated Build Time and Cost | Not stated in source |
| Specialized Tools and Equipment | A personal computer running the device's data-logging software, which records the sensor's force readings over USB. The software is part of the original device described in Laufer et al. 2016; its specifications are not re-verified for this page.[3] The 2020 validation study analysed the recorded force data in R (R-Project v3.4.1).[1] Consumables (use-time): 3-0 silk suture — the source used Sofsilk 3-0 (Medtronic) — and surgical gloves.[1] |
| Version | Version 1 — as described in Amiel et al. 2020 (American Journal of Surgery 220(1):100–104). The device was first reported in Laufer et al. 2016 and its validity established in Amiel et al. 2019; no later design iterations are documented.[1][2][3] |
| Development Team Contact Information | Imri Amiel, Roi Anteby, Moti Cordoba, Shlomi Laufer, Chaya Shwaartz, Danny Rosin, Mordechai Gutman, Amitai Ziv and Roy Mashiach — Faculty of Medicine, Tel Aviv University; Sheba Medical Center (Tel-Hashomer, Ramat-Gan); the Israel Center for Medical Simulation (MSR); and the Technion – Israel Institute of Technology (Haifa). Corresponding author: Roi Anteby (roianteby@mail.tau.ac.il); first author Imri Amiel (imri.amiel@sheba.health.gov.il).[1] |
Structural Parts
| Part Name | Qty | Material | Cost | Notes |
|---|---|---|---|---|
| Hook (component A) | 1 | Material not specified in source | Not reported | The point where the knot is tied, representing a vessel-ligation site. Material and dimensions are not specified in Amiel et al. 2020.[1] |
| Plexiglass tube (component B) | 1 | Plexiglass (acrylic) | OD 5.1 cm × ID 4.4 cm × wall 0.35 cm (Laufer et al. 2016, not re-verified); total length not stated | Placed over the hook to recreate the depth of a deep surgical field; removable. Its top sits above the hook (see build steps).[3][1] |
| Data sensor (component C) | 1 | Strain-gauge load cell (per Laufer et al. 2016, not re-verified) | Aluminium sheet 2.54 × 12.7 × 0.16 cm (Laufer et al. 2016, not re-verified) | Measures the vertical reaction force with strain gauges and logs it to a computer over USB. Sensor brand, sampling rate and range are attributed to Laufer et al. 2016 and were not re-verified for this page.[3][1] |
| Feedback unit (component D) | 1 | LED-and-buzzer circuit (specifications not stated) | Not reported | Red LED with a continuous beep above 1.3 N; green LED with an intermittent beep below it. Added after the original device; described in Amiel et al. 2019, whose full schematic was not accessed.[2][1] |
| Base / mounting platform | 1 | Material not specified in source | Not reported | Holds the hook, tube, sensor and feedback unit together. Shown in Fig. 1 of Amiel et al. 2020, but its material and dimensions are not given.[1] |
Build Instructions
Phase 1: Obtain or fabricate the components
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)[3] and Amiel et al. (2019),[2] 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.
- The hook (component A), where the knot is tied. Material and dimensions are not specified.[1]
- The plexiglass tube (component B), placed over the hook so the top of the tube sits 3 cm above the top of the hook.[1]
- The data sensor (component C): a strain-gauge load cell that logs the vertical reaction force to a computer over USB. Its dimensions, brand, sampling rate and range are attributed to Laufer et al. 2016 and not re-verified here.[3]
- The feedback unit (component D): red and green LEDs and a beeper, calibrated to the 1.3 N threshold. The feedback circuit was added after the original device and is described in Amiel et al. 2019; its schematic is not given in the staged sources.[2]
Phase 2: How the components are arranged
The source gives no assembly procedure; the arrangement below is read from Fig. 1.
- The hook (A) is mounted on a base platform (visible in Fig. 1; material and dimensions not specified).[1]
- The plexiglass tube (B) sits over the hook so the top of the tube is 3 cm above the hook.[1]
- The data sensor (C) measures the vertical reaction force at the hook and connects to a computer by USB cable.[1]
- 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.[2][1]
Phase 3: Verify function
- Launch the logging software and confirm the computer is reading the sensor over USB.
- Tie a test knot (3-0 silk, one-handed square-knot technique) on the hook inside the tube.
- Confirm the green LED and intermittent beep when the reaction force is below 1.3 N.
- Confirm the red LED and continuous beep when the reaction force exceeds 1.3 N.
- Confirm the software logs total force, peak pulling force, peak pushing force, and completion time for the knot.[1]
Not Suitable For
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.[1]
- Knot integrity testing under load — knot quality was judged visually by an examiner, not by tensile testing.[1]
- 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.[1]
- Tissue-model fidelity — the 1.3 N target was derived from expert performance, not from tissue models that measure tear forces.[1]
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 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.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 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.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 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. DOI: 10.3233/978-1-61499-625-5-199. PMID: 27046578. Original Knoti device hardware description.
| Alternative names | Knoti (the device name used throughout the source papers; written "KNOTI" in the figures) |
|---|
| Authors | Arturopelayo |
|---|---|
| License | CC-BY-SA-4.0 |
| Cite as | Arturopelayo (2026). "TissueDB/Simulators/Knot Tying Force-Feedback Simulator (Amiel)". Appropedia. Retrieved July 14, 2026. |