Tim Horeman

Assessment of Laparoscopic Skills Based on Force and Motion Parameters

Box trainers equipped with sensors may help in acquiring objective information about a trainees performance while performing training tasks with real instruments. The main aim of this study is to investigate the added value of force parameters with respect to commonly used motion and time parameters such as path length, motion volume, and task time. Two new dynamic bimanual positioning tasks were developed that not only requiring adequate motion control but also appropriate force control successful completion. Force and motion data for these tasks were studied for three groups of participants with different experience levels in laparoscopy (i.e., 11 novices, 19 intermediates, and 12 experts). In total, 10 of the 13 parameters showed a significant difference between groups. When the data from the significant motion, time, and force parameters are used for classification, it is possible to identify the skills level of the participants with 100% accuracy. Furthermore, the force parameters of many individuals in the intermediate group exceeded the maximum values in the novice and expert group. The relatively high forces used by the intermediates argue for the inclusion of training and assessment of force application during tissue handling in future laparoscopic skills training programs.

Influence of visual force feedback on tissue handling in minimally invasive surgery

Force feedback might improve surgical performance during minimally invasive surgery. This study sought to determine whether training with force feedback shortened the tissue‐handling learning curve, and examined the influence of real‐time visual feedback compared with postprocessing feedback.

The influence of instrument configuration on tissue handling force in laparoscopy.

In single-access surgery, instruments enter the abdominal cavity through only 1 incision, the position of the instruments relative to each other is different compared with that in conventional laparoscopy. Changes in instrument configuration may increase task complexity and therefore affect tissue handling skills. The aim of this study is to determine if a relation exists between instrument configuration and tissue interaction force. A study was performed to investigate the differences in manipulation force between a single-port (SP) and 2-port (TP) instrument configuration in a standard box trainer. A force platform was placed under a tissue manipulation task in a box trainer and used to measure the pulling forces and trial time. A total of 28 medical students with no previous experience in laparoscopic surgery were divided into 2 equal groups. Group 1 trained the task 6 times with the TP configuration and subsequently performed 6 trials with the SP configuration. Group 2 used the configurations in the opposite order. For both groups, the learning curves of the maximum force and task time were compared. Time and maximum pulling forces were significantly different between the 2 instrument configurations. In both groups, the participants used significantly more force in the SP configuration than in the TP configuration. The force data indicate that the increased complexity in instrument handling with straight instruments in a SP configuration increases the tissue manipulation force. Furthermore, the tissue handling skills of novices who mastered the task with the TP configuration decreased after switching to the SP configuration.

Laparoscopic suturing learning curve in an open versus closed box trainer

BackgroundThe aim of this study was to examine the influence of training under direct vision prior to training with indirect vision on the learning curve of the laparoscopic suture task.MethodsNovices were randomized in two groups. Group 1 performed three suturing tasks in a transparent laparoscopic box trainer under direct vision followed by three suturing tasks in a standard non-transparent laparoscopic box trainer equipped with a 0° laparoscope. Group 2 performed six suturing tasks in a standard laparoscopic box trainer. Performance time, motion analysis parameters (economy of movements) and interaction force parameters (tissue handling) were measured. Participants completed a questionnaire assessing: self-perceived dexterity before and after the training, their experienced frustration and the difficulty of the training.ResultsA total of 34 participants were included, one was excluded because of incomplete training. Group 1 used significantly less time to complete the total of six tasks (27 %). At the end of the training, there were no differences in motion or force parameters between the two groups. Group 2 rated their self-perceived dexterity after the training significantly lower than before the training and also reported significantly higher levels of frustration compared to group 1. Both groups rated the difficulty of the training similar.ConclusionNovices benefit from starting their training of difficult basic laparoscopic skills, e.g., suturing, in a transparent box trainer without camera. It takes less time to complete the tasks, and they get less frustrated by the training with the same results on their economy of movements and tissue handling skills.

Force sensing in surgical sutures

The tension in a suture is an important factor in the process of wound healing. If there is too much tension in the suture, the blood flow is restricted and necrosis can occur. If the tension is too low, the incision opens up and cannot heal properly. The purpose of this paper is to describe the design and evaluation of the Stitch Force (SF) sensor and the Hook-In Force (HIF) sensor. These sensors were developed to measure the force on a tensioned suture inside a closed incision and to measure the pulling force used to close the incision. The accuracy of both sensors is high enough to determine the relation between the force in the thread of a stitch and the pulling force applied on the suture by the physician. In a pilot study, a continuous suture of 7 stitches was applied on the fascia of the abdominal wall of multiple pigs to study this relationship. The results show that the max force in the thread of the second stitch drops from 3 (SD 1.2) to 1 (SD 0.3) newton after the 4th stitch was placed. During placement of the 5th, 6th and 7th stitch, the force in the 2nd stitch was not influenced anymore. This study indicates that in a continuous suture the force in the thread remains constant up to more than 3 stiches away from the pulled loose end of the suture. When a force feedback tool is developed specially for suturing in surgery on patients, the proposed sensors can be used to determine safety threshold for different types of tissue and sutures.

The use of navigation forces for assessment of wrist arthroscopy skills level.

Purpose To provide an efficient learning process, feedback on performance is crucial. In skills laboratories, it is possible to measure the skills and progression of skills of the trainees objectively. This requires metrics that represent the learning curve of the trainee, which were investigated for wrist arthroscopy. The research questions were: What are the forces used by novices during wrist arthroscopy?What aspects of these navigation forces are discriminative for the wrist arthroscopy skills level?Methods A cadaver wrist was mounted in a custom-made distraction device mounted in front of a force platform (ForceTrap). Eleven novices were invited to perform two tasks on the wrist: Insertion of the scope through the 3-4 portal and the hook through the 6R portal, and visualization of the hook in the center of the imageNavigation through the wrist from radial to ulnar with probing and visualization of five predefined landmarksThe second task was repeated 10 times. The absolute force (F abs) and the direction of force were measured. The angle α is defined in the vertical plane, and the angle β in the horizontal plane. Results The median F abs used by novices remained below the force threshold as defined from the expert data (7.3 N). However, the direction of the applied forces by novices in both planes was not consistent with expert data and showed a wider range. Also, there was no improvement after more trials. Conclusion Our study suggests by the absence of a learning curve for the novices and a significant difference between novices and experts that novices can benefit from feedback on the magnitude and direction of forces to improve their performance.

Design of a box trainer for objective assessment of technical skills in single-port surgery.

OBJECTIVE Laparoscopic single-port (SP) surgery uses only a single entry point for all instruments. The approach of SP has been applied in multiple laparoscopic disciplines owing to its improved cosmetic result. However, in SP surgery, instrument movements are further restricted, resulting in increased instrument collisions compared with standard multiport (MP) laparoscopy. METHODS Our goal was to develop a trainer that can quantitatively measure task time, force and motion data during both MP and SP training to investigate the influence of instrument configuration on performance. Custom-made abdominal force sensors and accelerometers were integrated into a new training box that can be used in an SP and an MP configuration. This new box trainer measures forces, acceleration, and tilt angles during training of SP and MP laparoscopy. With the new trainer, 13 novices performed a tissue manipulation task to test whether significant differences exist between MP and SP in maximum abdominal force, maximum tissue manipulation force, maximum acceleration, and tilt angles of the handles. RESULTS The results show that the task time (SP-145s, standard deviation (SD) = 103 vs MP-61s SD = 16), maximum abdominal force (SP-8.4N, SD = 2.0 vs MP-left (L)-3.3N, SD = 0.8 and MP-right (R)-5.8N, SD = 2.1), tissue manipulation force (SP-10.4N, SD = 3.6 and MP-5.6N, SD = 1.3), maximum acceleration (MP-L-9m/s(2), SD = 5 vs SP-L-14m/s(2), SD = 7), and tilt angles of the left handle are significantly higher in SP. CONCLUSIONS AND DISCUSSION This study shows that the new trainer can be used to find the most important differences in instrument and tissue handling, which is an important step toward the assessment of surgical skills needed for safe SP surgery depending on force and motion-based parameters.

Tying different knots: what forces do we use?

AbstractBackgroundA study was performed to determine differences in applied interaction force between conventional open surgery and laparoscopic surgery during suturing in a non-clinical setting.MethodsIn a laparoscopic box trainer set-up, experts performed two intracorporeal and two extracorporeal sutures on an artificial skin model. They also performed two instrument-tie knots and two one-hand square knots in a similar conventional training set-up. The force exerted on the artificial tissue (mean force, mean non-zero, maximum, and volume) and the time to complete a task were measured. For analysis purposes, sutures are divided in a needle driving phase (Phase 1) and knot-tying phase (Phase 2). ResultsPhase 1: Force values in laparoscopic suturing are significantly higher than in conventional suturing, except for the force volume during extracorporeal suturing versus the one-hand square knot. Phase 2: The mean force non-zero and maximum force during the intracorporeal knot are significantly higher than during the instrument-tie knot. The mean and maximum force during the extracorporeal knot are significantly higher than during the one-hand square knot. Furthermore, laparoscopic suturing takes longer time than conventional suturing.ConclusionExpert surgeons apply significantly higher force during laparoscopic surgery compared to conventional surgery even though the same strategy is used. Aspects such as the limited visual and haptic feedback, and movement possibilities hamper surgeons’ ability to assess the applied interaction force. Therefore it can be useful to provide additional force feedback about the applied interaction force during training in non-clinical settings.

A Force Measurement System for Training of Arthroscopic Tissue Manipulation Skills on Cadaveric Specimen

To improve arthroscopic skills, the preferred means of training is cadaveric tissue, because this gives the most realistic scenario. A drawback of cadaveric training is that objective performance tracking and accompanied feedback cannot be provided due to the absence of a suitable system. The main criteria were that the system should be compatible with any cadaveric joint, be used with any type of instrument, easy to set up, and measure two critical parameters that reflect the task efficiency (task time) and safety (forces due to instrument-tissue interaction). This resulted in the development of a force measurement system which consists of a custom-made universal vice, a custom-designed six degree-of-freedom (DOF) force measurement table (FMT) coupled to a computer equipped with customized software to record the time and forces in all directions. The FMT was calibrated and able to measure forces in the range of 0-750 N, with an accuracy of 0.1 N. During two cadaveric training courses, measurements were performed with the FMT. It was observed that the acquired force data could discriminate between novices and experts or reflect a certain phase of a navigation task performed in a cadaveric cow and human knee. A distinct phase highlighted from the force measurements is the insufficient joint stressing of novices during navigation. This results in too small a joint space for inspection and forces the novices to readjust the stressing. As forces cannot be seen, the FMT can contribute to more efficient training by providing explicit cues on the exerted loads during training. This enables a more precise supervision of the trainees

Design and Preliminary Evaluation of a Stiff Steerable Cutter for Arthroscopic Procedures

This article describes a novel and simple shaft actuated tip articulation (SATA) mechanism that allows arthroscopic instruments to articulate while remaining stiff. Since the SATA mechanism requires only independent rotation of two tubes for hinge articulation, cables, gears, or other internal components that are normally found in steerable endoscopic instruments become obsolete. The SATA mechanism was integrated in a new steerable cutter prototype and tested. Early user, mechanical strength and cadaver experiments were performed that indicate that this first prototype withstands an axial and sideways force of 100 N and 20 N, that trained users can (dis) assemble the instrument in less than 1.5 min and that a surgeon is able to reach all important locations on the menisci