Original ReportsVisual Force Feedback Improves Knot-Tying Security
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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