Elsevier

Journal of Surgical Education

Volume 71, Issue 1, January–February 2014, Pages 133-141
Journal of Surgical Education

Original Reports
Visual Force Feedback Improves Knot-Tying Security

https://doi.org/10.1016/j.jsurg.2013.06.021Get rights and content

Background

Residents in surgical specialties suture multiple wounds in their daily routine and are expected to be able to perform simple sutures without supervision of experienced surgeons. To learn basic suture skills such as needle insertion and knot tying, applying an appropriate magnitude of force in the desired direction is essential. To investigate if training with real-time visual force feedback improves the suture skills of novices, a study was conducted using a training platform that measures all forces exerted on a skin pad, i.e., the ForceTRAP.

Method

Two groups of novices were trained on this training platform during a suture task. One group (nov-c) received no visual force feedback during training, whereas the test group (nov-t) trained with visual feedback. The posttest and follow-up test were performed without visual force feedback.

Results

A significant difference in reaction force, (nov-c: mean 2.47 N standard deviation [SD] ± 0.62, nov-t: mean 1.79 N SD ± 0.37), suture strength (nov-c: median 25 N interquartile range (IQR) 15, nov-t: median 50 N interquartile range 25), and task time (nov-c: mean 109 s SD ± 22, nov-t: mean 134 s SD ± 31) was found between the control and training group of the posttest.

Conclusion

Participants that are trained with visual force feedback produce the most secure knots in the posttest and their suturing results in lower applied forces. Therefore, the results of this study indicate that visual force feedback supports students while learning to insert the needle smoothly, to effectively align the suture threads and to balance the force between instruments during knot tying. However, for long-term learning effects, probably more than 1 training session is required.

Introduction

Suturing is one of the most common methods for wound closure, and surgeons suture multiple wounds in their daily routine. Suturing of superficial and deep skin lacerations is considered as one of the most important procedural skills that all surgical residents ought to possess at the start of their medical career.1 After graduation, doctors are expected to be able to perform simple sutures without supervision of experts.2 However, because of the lack of opportunities to practice while in their medical education program, most residents acquire these basic surgical skills when starting to treat patients in practice.

Courses dedicated to practising surgical skills would help novices to gain surgical experience before their first contact before they treat patients in practice. Such courses will increase confidence, improve performance, and reduce the number of beginner’s errors.3 When a suture fails to perform its function, the consequences may be disastrous.4, 5, 6 A bleeding may occur when the suture loop that surrounds a vessel is disrupted. When a suture in an abdominal wound unties or breaks, wound dehiscence and even evisceration may follow.7 Because of the importance of setting knots of good quality, there is a continuing need to improve techniques to teach basic suture skills.8 The most important criteria for proper wound closure are known: proficiency in speed, precision of hand movements, and the firmness of the body of the suture.9

In a suture, tightness of the loop of the thread determines the pressure on the tissue nearby the wound, and therefore the blood supply and drainage of the wound area. As a result, the healing process of the wound is related to the suture itself.10 A good suture is not too tight to prevent infections and necrosis and not too loose to be unable to press the wound edges together. Furthermore it will not unravel during the recovery of the wound by natural skin movements or accidental manipulation.

During needle insertion it is important that the curvature of the needle is followed. A well-controlled force in line with the tip of the needle should push the needle with minimal damage through the tissue. Inadequate needle insertion can result in excessive reaction forces that damage tissue from the inside. Reaction forces during knot tensioning occur owing to poor alignment of the threads or a force imbalance between instrument tips while tightening. If the force on the threads during knot tying is not in balance, a reaction force (FR) is generated in the tissue that can result in tissue damage (Fig. 1 [left]). A force imbalance between threads in combination with poor thread alignment indicates that a knot is not properly tensioned increasing the risk on dangerous and weak knots (Fig. 1 [right]). For proposed suture errors, a reaction force (FR) is generated in the tissue that can be measured by a force sensor. During needle insertion, a low reaction force is always present. In an ideal knot-tying scenario, the measured reaction force remains zero.

An increasing number of studies suggest that training with real-time visual feedback of instrument motion in virtual-reality and augmented-reality simulators has a positive effect on learning.11, 12 Moreover, a prior study in laparoscopic needle insertion showed that novices that were trained with augmented-reality feedback of the tissue manipulation force applied less force compared with the control group that received no visual feedback.13 As a follow-up to this study, we developed a force sensor, the ForceTRAP, that incorporates colored LEDs to signal any imbalance in the forces exerted during tissue manipulation tasks.

In the current study, the ForceTRAP is used to provide feedback on 3 important suture errors that cause high reaction forces in (artificial) tissue. During needle insertion, the student is warned for high forces due to inefficient needle insertion with orange and red lights. During knot tying, the orange or red light warns for a force imbalance between the 2 tensioned threads or for poor alignment of the 2 tensioned threads.

The current study investigates the added value of real-time visual force feedback on suturing. The main research question is whether training with real-time visual force feedback improves the suture skills of novices.

Section snippets

Hardware

The ForceTRAP is based on a previously developed force platform that was validated in 2 studies on intracorporal suturing in a box trainer.14, 15 In these studies, a force platform was used to validate the suture task with force parameters. The ForceTRAP uses distance sensors and a microcontroller to determine the deformations of 3 orthogonally placed parallelograms. Figure 2 displays such a parallelogram mechanism, which consists of 2 stiff bars and 2 spring blades. To measure deformation of

Results

All participants were able to complete the pretest, training trials, and posttest. Because of illness of 1 participant, the FB group of the follow-up measurement consisted of 12 instead of 13 participants.

Discussion

In the current study, the results show that immediately after training in simple interrupted suturing with visual force feedback, the applied forces are significantly reduced and that the suture strength is increased. However, these performance improvements also result in a longer task completion time. Without additional training, these differences diminish within 4 weeks after training.

Conclusion

By training with visual force feedback, novices can learn how instrument movements during needle insertion and knot tying influence the force exerted on the tissue. Participants that are trained with visual force feedback produce the most secure knots in the posttest and their suturing results in lower applied forces. Therefore, the results of this study indicate that visual force feedback supports students while learning to insert the needle smoothly, to effectively align the suture threads

Acknowledgment

The authors would like to thank all students, personnel and gynecologists from the LUMC for participation in this study. Special thanks to Gert-Jan Hultzer en René Rodenburg of the Skills laboratory for educating 2 of the authors in advanced suturing and for providing us with all the instruments, materials, and facilities necessary.

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