Precision in stitches: Radius Surgical System

Comparison of two cable configurations in 3D printed steerable instruments for minimally invasive surgery

In laparoscopy, a small incision size improves the surgical outcome but increases at the same time the rigidity of the instrument, with consequent impairment of the surgeon’s maneuverability. Such reduction introduces new challenges, such as the loss of wrist articulation or the impossibility of overcoming obstacles. A possible approach is using multi-steerable cable-driven instruments fully mechanical actuated, which allow great maneuverability while keeping the wound small. In this work, we compared the usability of the two most promising cable configurations in 3D printed multi-steerable instruments: a parallel configuration with all cables running straight from the steerable shaft to the handle; and a multi configuration with straight cables in combination with helical cables. Twelve participants were divided into two groups and asked to orient the instrument shaft and randomly hit six targets following the instructions in a laparoscopic simulator. Each participant carried out four trials (two trials for each instrument) with 12 runs per trial. The average task performance time showed a significant decrease over the first trial for both configurations. The decrease was 48% for the parallel and 41% for the multi configuration. Improvement of task performance times reached a plateau in the second trial with both instruments. The participants filled out a TLX questionnaire after each trial. The questionnaire showed a lower burden score for the parallel compared to multi configuration (23% VS 30%). Even though the task performance time for both configurations was comparable, a final questionnaire showed that 10 out of 12 participants preferred the parallel configuration due to a more intuitive hand movement and the possibility of individually orienting the distal end of the steerable shaft.

Endoscopic surgery suturing techniques: a randomized study on learning

BACKGROUND

Surgeons have widely adopted endoscopic suturing techniques using conventional laparoscopic instruments and the more advanced robotic systems. The FlexDex is a novel articulating laparoscopic needle driver providing enhanced dexterity in laparoscopic surgery. This study evaluates and compares the learning curve of endoscopic suturing with conventional laparoscopy, the FlexDex and robotic suturing in novices.

METHODS

Participants performed a minimal invasive suturing task in three different ways in a randomized order: with a conventional laparoscopic needle driver, using the FlexDex needle driver and third, using the Da Vinci Si surgical system. Primary outcome was suturing task time. Secondary outcome parameters were assessment of suturing quality and workload perception.

RESULTS

A total of 10 novice participants were included and completed a total of 300 sessions. Median (IQR) suturing time of the first 5 sessions was 231 s (188-291) in the laparoscopic group versus 378 s (282-471) in the FlexDex group versus 189 s (160-247) in the DaVinci Si group. The last 5 sessions showed significant reduction of median suturing time of 143 s (120-190), 232 s (180-265) and 172 s (134-199) respectively. Analysis identified that the learning curve for the laparoscopic needle driver and Da Vinci Si was reached in 5 sessions, compared to 8 sessions for the Flexdex. The laparoscopic needle driver and Da Vinci Si showed a significant shorter median suturing time compared to the FlexDex (p = 0.00). The FlexDex quality assessment scores were significantly lower compared to the laparoscopic (p = 0.00) and robotic (p = 0.00) scores and perceived workload remains high for the FlexDex users.

CONCLUSIONS

Ex vivo endoscopic suturing with the FlexDex demonstrated a prolonged learning curve compared to laparoscopic and robotic suturing. The learning curve of the FlexDex is fundamentally different from conventional laparoscopic and robotic instruments. This study provides further insights in the implementation and training of endoscopic suturing techniques.

Autonomous robotic laparoscopic surgery for intestinal anastomosis

Autonomous robotic surgery has the potential to provide efficacy, safety, and consistency independent of individual surgeon's skill and experience. Autonomous anastomosis is a challenging soft-tissue surgery task because it requires intricate imaging, tissue tracking, and surgical planning techniques, as well as a precise execution via highly adaptable control strategies often in unstructured and deformable environments. In the laparoscopic setting, such surgeries are even more challenging because of the need for high maneuverability and repeatability under motion and vision constraints. Here we describe an enhanced autonomous strategy for laparoscopic soft tissue surgery and demonstrate robotic laparoscopic small bowel anastomosis in phantom and in vivo intestinal tissues. This enhanced autonomous strategy allows the operator to select among autonomously generated surgical plans and the robot executes a wide range of tasks independently. We then use our enhanced autonomous strategy to perform in vivo autonomous robotic laparoscopic surgery for intestinal anastomosis on porcine models over a 1-week survival period. We compared the anastomosis quality criteria-including needle placement corrections, suture spacing, suture bite size, completion time, lumen patency, and leak pressure-of the developed autonomous system, manual laparoscopic surgery, and robot-assisted surgery (RAS). Data from a phantom model indicate that our system outperforms expert surgeons' manual technique and RAS technique in terms of consistency and accuracy. This was also replicated in the in vivo model. These results demonstrate that surgical robots exhibiting high levels of autonomy have the potential to improve consistency, patient outcomes, and access to a standard surgical technique.

Single incision laparoscopic repair for late-onset congenital diaphragmatic hernia using oval-shaped multichannel port device (E•Z ACCESS oval type)-2 months infantile case of Bochdalek hernia

INTRODUCTION

Late-onset congenital diaphragmatic hernia constitutes 10%-36% of congenital diaphragmatic hernias. They qualify for endoscopic treatment including both thoracoscopic and laparoscopic approaches because this type of patient is in relatively stable condition compared with neonatal cases. However, single incision laparoscopic approach has not been reported. We herein report an infantile case of late-presenting diaphragmatic hernia who underwent single incision laparoscopic repair using an oval-shaped multichannel port device.

MATERIALS AND SURGICAL TECHNIQUE

A 2 month old female infant had sudden onset dyspnea with cyanosis and was diagnosed as having left diaphragmatic hernia (Bochdalek hernia) by chest X-ray. As her respiratory condition became stable under conservative treatment using combination of decompression of the gastrointestinal tract and mild sedation, we electively planned laparoscopic repair. Preoperative enhanced computed tomography imaging found that herniated organs were stomach, spleen, pancreatic tail, small intestine and right colon. The patient also had an umbilical hernia, so we decided to perform single incision repair through this umbilical hernia. Three trocars were introduced using an oval-shaped multichannel port device and herniated organs were reduced by gentle manipulation. The defect of the diaphragm was closed by bi-hand needle driving for upper and lower limb using a stay suture. The umbilical hernia was also repaired. Postoperative course was uneventful and no recurrence was recognized.

DISCUSSION

Wider trocar separation was achieved using the oval-shaped device, making the needle driving easier to perform. By using an oval-shaped multichannel port device and ingenuity of needle driving, single incision repair of infant diaphragmatic hernia was enabled.

Comparison of Laparoscopic Steerable Instruments Performed by Expert Surgeons and Novices

As an alternative to the surgical robot, some medical companies have engineered new steerable devices that mimic the robot’s capacities. This study aimed to assess how steerable instruments ameliorate the efficacy of suturing in comparison with the traditional instrument, and a combination instruments, performed by experienced and novice surgeons. The study was performed by three experienced surgeons and three novice surgeons. The instruments employed were divided into three surgical sets: two steerable dissectors; one steerable dissector and one straight needle; two straight needle holders. The study supervisor recorded the total time for the procedure, the number of bites completed, the time for each bite, and the quality of the procedure. In our study, we found consistent data demonstrating that experienced laparoscopists completed the prescribed suture pattern with more bites in less time than novices. The use of two steerable instruments was more time consuming than standard straight instruments, but a combination of instruments was significantly less time consuming, as was the use of two straight needle holders. This result was even observed in novice surgeons. Combining a steerable instrument with a traditional straight needle holder provided more advantages in this study.

Learning Intracorporeal Suture on Pelvitrainer Using a Robotized Versus Conventional Needle Holder

BACKGROUND

Laparoscopy is the gold standard approach in numerous surgical procedures. A new generation of robotized instruments has been developed to compensate for the ergonomic constraints of conventional instruments. The main objective was to compare the learning curves of novices for intracorporeal suturing on a laparoscopy pelvitrainer, using either a robotized needle holder or conventional needle holders. The post-training performances under ergonomically difficult conditions were also analyzed.

MATERIALS AND METHODS

Fifth-year medical students were randomized in group A using a robotized needle holder (JAIMY; Endocontrol, Grenoble, France) and group B using straight conventional needle holders. They undertook four training sessions (intracorporeal knot-tying task) followed by an evaluation session (intracorporeal knots-tying task, frontal suture, and hexagonal suture).

RESULTS

Twenty participants were included. The performances of the two groups (n = 10) were not significantly different at baseline. During the training sessions, there was a learning curve with a plateau at the third session for both the groups. At the final evaluation session, there was no significant difference between group A and group B for the intracorporeal knot-tying task (median fundamentals of laparoscopic surgery score: 468 versus 474.5 respectively; P = 0.762). There was a significant difference between group A and group B for the frontal suture (median global score: 15.75 versus 3.75 respectively; P = 0.005) but not for the hexagonal suture (median global score: 18 versus 15 respectively; P = 0.284).

CONCLUSIONS

Learning curves were equally fast using the robotized needle holder versus conventional instruments and led to equivalent performances. Under ergonomically difficult conditions, the robotized needle holder provided an advantage relative to conventional instruments.

Evaluation and comparison of basic gestures in ex vivo laparoscopic surgery using a robotic instrument and traditional laparoscopic instruments

BACKGROUND

The robotic Dextérité Surgical™ arm (DEX) is an instrument used in laparoscopy that provides 6 degrees of freedom and 360 degrees of rotation with a needle holder and scissors. To evaluate the benefits this instrument offers, we asked novice surgeons to use DEX and a conventional laparoscopic instrument on a pelvitrainer and compared the results.

METHODS

The participants were asked to perform two exercises with DEX and then with a conventional laparoscopic instrument on a pelvitrainer that contained a synthetic reproduction of a male pelvis. For the stitching exercise, the distance from the marked points and any tears caused were analyzed. For the cutting, the participants were judged by how well they respected the marked extremities, the form and the amount of "hacking" observed on a multi-criteria scale. The amount of time required to carry out the exercises was recorded.

RESULTS

All twelve urology interns all succeeded in using DEX. Of the 36 stitches, seven were giving a failing grade (19.4%) when using the conventional laparoscopic needle holder and one (0.3%) was recorded when using DEX. All of the criteria (entry and exit points, tears and duration) for the results obtained were better when using DEX compared to the classic laparoscopic tool. This difference was statistically significant for horizontal stitches and tearing. Concerning the cuts made, the global score obtained, following a multi-criteria scale, favored the use of DEX for 10 out of 12 candidates (83.3%) with an average score of +2.6 (±2.1). No significant difference was recorded for the duration of each exercise.

CONCLUSION

It does not take novice operators long to understand how to use DEX. It enables precise stitching and reduces tearing while improving the quality of cuts compared to conventional laparoscopic instruments, all without slowing the user down.

LEVEL OF EVIDENCE

4.

Performance of Kymerax© precision-drive articulating surgical system compared to conventional laparoscopic instruments in a pelvitrainer model

BACKGROUND

The Kymerax© Precision-Drive Articulating Surgical System by Terumo© is a handheld laparoscopic robot which permits motion in two additional degrees of freedom (deflection and rotation in the instrument tip). In a pelvitrainer model, we compared the performance of participants with different laparoscopic experiences and compared Kymerax© to conventional laparoscopic instruments.

METHODS

20 expert surgeons, performing more than 50 laparoscopic procedures per year, and 25 medical students without any experience in surgery at all were selected. Each participant was randomized into two groups: Group TK performed the tasks using the traditional laparoscopic Instruments (TLI) first and Kymerax© thereafter, group KT vice versa. Six standardized tasks were used: Two instructional exercises and four tasks where time, number of mistakes, and overall precision were measured. Finally, a questionnaire had to be answered.

RESULTS

All four tasks were performed significantly more slowly with the Kymerax© device. Improved needle control in stitches towards the surgeon, significantly less deviation while cutting along different lines as well as a significantly reduced fraying of the cutting edge were found when participants were using Kymerax©. By questionnaire more than 90% of the participants indicated clear advantages using Kymerax©. However, participants needed more training time and had an earlier loss of concentration with Kymerax©. Further complaints about Kymerax© were its limitations in rotation and deflection, the impaired view as well as the non-ergonomic instrument handle. Rotation force, instrument weight, digital instrument-tip control, and needle fixation were rated as accurate.

CONCLUSIONS

This study shows that more time is needed to solve tasks with Kymerax© compared to conventional laparoscopic instruments. Kymerax© is superior to conventional laparoscopy for suturing at difficult angles and cutting along complex structures. Kymerax© can potentially bring benefits for certain laparoscopic tasks, but as seen in this study, further developments are necessary. Terumo© meanwhile closed down its Kymerax

Robot-like dexterity without computers and motors: a review of hand-held laparoscopic instruments with wrist-like tip articulation

INTRODUCTION

Conventional manual laparoscopic instruments for minimally invasive surgery have limited dexterity within the patient, making procedures challenging. Surgical robotic systems offer enhanced articulation, but at substantial financial costs. This has motivated the development of high-dexterity, low-cost laparoscopic instruments.

AREAS COVERED

This article reviews both commercial and academic results on creating fully mechanical (i.e. non-robotic) laparoscopic instruments that provide wrists or wrist-like dexterity within the patient. We review the state of the art in the development of these mechanical instruments, focusing on the surgeon interface, wrist mechanism, and the kinematic mapping between the two. Expert commentary: Current articulated mechanical laparoscopic instruments exhibit a wide range of designs, with no clear consensus on what makes such devices easy to use. As these technologies mature, user studies are needed to determine surgeon preferences. Articulated, low-cost instruments have the potential to impact the minimally invasive surgery market if they provide compelling benefits to surgeons.

Plenoptic Cameras in Surgical Robotics: Calibration, Registration, and Evaluation

Three-dimensional sensing of changing surgical scenes would improve the function of surgical robots. This paper explores the requirements and utility of a new type of depth sensor, the plenoptic camera, for surgical robots. We present a metric calibration procedure for the plenoptic camera and the registration of its coordinate frame to the robot (hand-eye calibration). We also demonstrate the utility in robotic needle insertion and application of sutures in phantoms. The metric calibration accuracy is reported as 1.14 ± 0.80 mm for the plenoptic camera and 1.57 ± 0.90 mm for hand-eye calibration. The accuracy of needle insertion task is 1.79 ± 0.35 mm for the entire robotic system. Additionally, the accuracy of suture placement with the presented system is reported at 1.80 ± 0.43 mm. Finally, we report consistent suture spacing with only 0.11 mm standard deviation between inter-suture distances. The measured accuracy of less than 2 mm with consistent suture spacing is a promising result to provide repeatable leak-free suturing with a robotic tool and a plenoptic depth imager.

Comparing a Mechanical Analogue With the Da Vinci User Interface: Suturing at Challenging Angles

The da Vinci Surgical System offers a natural user interface and wrist articulation, which enable suturing and other complex surgical actions in confined spaces. However, both the one-time cost of the system and the recurring cost of the limited-use instruments remain high. This has motivated the development of several hand-held alternatives-some partially motorized, some fully mechanical-in recent years. While a few of these have been commercialized, none have yet met with broad commercial success comparable to the da Vinci robot. In this letter, we suggest a user interface-based explanation for this, and describe a new mechanical instrument that provides wrist articulation with a novel user interface. We provide results of a single-user pilot study with an experienced laparoscopic surgeon to compare the new device with a traditional wristless laparoscopic tool, a prior commercial wristed mechanical tool (the RealHand), and the da Vinci robot, in the context of suturing at challenging angles. We observe better targeting of desired suture needle entry and exit points with the new device in comparison to prior wristed and wristless mechanical instruments, with the da Vinci only slightly outperforming the new tool.

A multi-degree-of-freedom needle driver with a short tip and small shaft for pediatric laparoscopic surgery: in vivo assessment of multi-directional suturing on the vertical plane of the liver in rabbits

BACKGROUND

Laparoscopic Kasai portoenterostomy has been performed in infants with biliary atresia at several institutions, but laparoscopic anastomosis requiring multi-directional suturing on a vertical plane of the liver remains a challenge. To assist multi-directional suturing, we developed a multi-degree-of-freedom (DOF) needle driver whose tip length was 15 mm and shaft diameter was 3.5 mm. The tip of the multi-DOF needle driver has three DOFs for grasp, flection and rotation. The aim of this study was to evaluate the performance of the multi-DOF needle driver in two kinds of in vivo experiments.

METHODS

Surgeons were asked to perform four-directional laparoscopic suturing on a vertical plane of the liver in six rabbits using the multi-DOF needle driver or a conventional needle driver. The needle grasping time, the needle handling time, the number of needle insertions, the number of liver lacerations, the suturing width and depth, and the area of necrotic tissues were analyzed and compared. Additionally, one surgeon was asked to perform laparoscopic hepato-jejunostomy in four rabbits to assess the feasibility of Kasai portoenterostomy using the multi-DOF needle driver.

RESULTS

The suturing depth using the multi-DOF needle driver was significantly larger than that using the conventional needle driver in both the right and downward suturing directions. No statistically significant differences were found in other metrics. Liver lacerations were observed only when suturing was performed using the conventional needle driver. The experimental laparoscopic hepato-jejunostomy using the multi-DOF needle driver was successful.

CONCLUSIONS

Using the multi-DOF needle driver, uniform multi-directional suturing on a vertical plane of the liver could be performed. The short distal tip of the multi-DOF needle driver demonstrated its advantages in multi-directional suturing in a small body cavity. The multi-DOF needle driver may be able to be used to perform complex tasks in laparoscopic Kasai portoenterostomy.

Single-port live donor nephrectomy using a novel Curved Radius r2 Surgical System in an in vivo model

OBJECTIVE

Single-port laparoscopic donor nephrectomy provides low morbidity and satisfactory cosmetic results for patients. The aim of this animal study was to establish a surgical technique of single-site (LESS) living donor nephrectomy using novel curved r2 CURVE manipulators specially designed for single-port access.

MATERIAL AND METHODS

A total of six LESS nephrectomies were performed in three female pigs. r2 CURVE-instruments (Tuebingen Scientific Medical GmbH) were used providing a curved rotatable shaft, endless tip rotation, as well as 90° tip deflection. A 10 mm 30° extra long laparoscope, r2-curved Grasper, Maryland dissector and bipolar scissors were used for mobilization and dissection.

RESULTS

All LESS nephrectomies were performed successfully. Average operative time was 80 min (range, 42-149 min). No technical problems were observed. Insertion and extraction of the instruments through the single-port were easy to conduct. The diameter of the used single-port was sufficient for safe manual organ harvesting. Potential conflict between the laparoscope and the instrument handles was avoided by using an extra long laparoscope.

CONCLUSIONS

The new curved and deflectable instruments showed that single-port nephrectomy using the R2 manipulators is feasible. Single-port laparoscopic nephrectomy might be more patient-friendly and improve the willingness of potential donors to donate live organs.

Smart tissue anastomosis robot (STAR): a vision-guided robotics system for laparoscopic suturing

This paper introduces the smart tissue anastomosis robot (STAR). Currently, the STAR is a proof-of-concept for a vision-guided robotic system featuring an actuated laparoscopic suturing tool capable of executing running sutures from image-based commands. The STAR tool is designed around a commercially available laparoscopic suturing tool that is attached to a custom-made motor stage and the STAR supervisory control architecture that enables a surgeon to select and track incisions and the placement of stitches. The STAR supervisory-control interface provides two modes: A manual mode that enables a surgeon to specify the placement of each stitch and an automatic mode that automatically computes equally-spaced stitches based on an incision contour. Our experiments on planar phantoms demonstrate that the STAR in either mode is more accurate, up to four times more consistent and five times faster than surgeons using state-of-the-art robotic surgical system, four times faster than surgeons using manual Endo360(°)®, and nine times faster than surgeons using manual laparoscopic tools.

Laparoendoscopic single-site common bile duct exploration using the manual manipulator

BACKGROUND

Laparoendoscopic single-site (LESS) surgery has developed as a new surgical modality that has increased cosmetic benefits over conventional endoscopic surgery. However, there are no reports about LESS surgery in common bile duct exploration. This report presents a LESS surgery to manage CBD stones by laparoscopic choledochotomy and C-tube placement with favorable outcomes.

METHODS

This retrospective review analyzes 13 patients who underwent LESS CBD exploration with C-tube drainage for choledocholithiasis. The technique is herein described and the outcomes measured. The Radius Surgical System (Tübingen Scientific Medical, Tübingen, Germany) is a flexible manual manipulator that was applied for suturing and ligation to overcome the difficulties associated with LESS surgery.

RESULTS

The diameters of the CBDs ranged from 12 to 20 mm, the median number of stones was 5.8, and the median diameter of stones was 9 mm. All of the routine procedures including choledochotomy, intraoperative ultrasound, choledochoscopy, and intraoperative cholangiography guidance were performed. Stone clearance from the CBD was achieved for all but one of the patients. It was possible to close the common bile duct opening with regular forceps, but this required extra effort compared to conventional laparoscopic surgery. On the other hand, the manual manipulator enabled the optimal penetration angle and was useful for both intracorporeal suturing and ligation for the closure of the common bile duct opening. The manual manipulator also helped to overcome in-line viewing and hand/instruments collisions, which are common problems in LESS surgery. No mortality was associated with this procedure, and two wound infections were drained without anesthesia. No recurrent stones were observed during the follow-up period.

CONCLUSIONS

LESS surgery was successfully applied to CBD exploration as an available alternative to conventional laparoscopic surgery. This method is technically feasible and produces superior cosmetic results. The manual manipulator may therefore have several advantages for performing LESS surgery.

Review of manual control methods for handheld maneuverable instruments

By the introduction of new technologies, surgical procedures have been varying from free access in open surgery towards limited access in minimal access surgery. Improving access to difficult-to-reach anatomic sites, e.g. in neurosurgery or percutaneous interventions, needs advanced maneuverable instrumentation. Advances in maneuverable technology require the development of dedicated methods enabling surgeons to stay in direct, manual control of these complex instruments. This article gives an overview of the state-of-the-art in the development of manual control methods for handheld maneuverable instruments. It categorizes the manual control methods in three levels: a) number of steerable segments, b) number of Degrees Of Freedom (DOF), and c) coupling between control motion of the handle and steering motion of the tip. The literature research was completed by using Web of Science, Scopus and PubMed. The study shows that in controlling single steerable segments, direct as well as indirect control methods have been developed, whereas in controlling multiple steerable segments, a gradual shift can be noticed from parallel and serial control to integrated control. The development of multi-segmented maneuverable instruments is still at an early stage, and an intuitive and effective method to control them has to become a primary focus in the domain of minimal access surgery.

Laparoscopic Treatment for Esophageal Achalasia and Gastro-Esophago-reflex Disease Using Radius Surgical System

Radius surgical system (RSS) is a manual manipulator to enhance the surgeon's dexterity and ergonomy achieving more degrees of freedom, and it enables us easy to perform intracorporeal suturing in laparoscopic surgery. We successfully performed laparoscopic treatment including intracorporeal suturing in cases of esophageal achalasia and gastroesophageal reflux disease using RSS. RSS may facilitate of intracorporeal suturing and knotting in complex laparoscopic procedures.

Comparison of Two Control Methods for Minimally Invasive Surgical Instruments

Laparoscopic surgery is performed with long and slender instruments through one or several incisions in the abdominal wall. Steerable instruments with flexible distal tips have been developed for improving the ease of access to anatomic structures. However, the development of an intuitive and efficient control method for such steerable instruments remains a challenge. To determine which interface are most intuitive and effective to control steerable instruments, the current study evaluates the performance of novices in orienting the tip of a steerable laparoscopic forceps using thumb control or wrist control. Using two steerable instruments, one controlled by the thumb and the other by the wrist, 24 novices were divided into two groups that had to carry out an experimental task in an EndoTrainer with one of the two instruments. The participants had to orient the tip of the instrument relative to five targets that were presented in a random order. After a break, the participants switched to a second measurement session with the other instrument, followed by a third measurement session with the first instrument. Each participant performed the task 240 times over the three measurement sessions. The performance was assessed by measuring the performance time, using a questionnaire and grading the work load. The performance time showed a significant learning curve for each control method. The shortest performance time was recorded during the third session with both control methods (42.7 s for thumb control and 44.6 s for wrist control). A significant difference in the performance time was observed in the second session (p <0.02) but not in the first and third session. The questionnaire showed that most participants had a preference for thumb control. After a brief training period, thumb control and wrist control did not reveal significant differences in task performance. However, thumb control was strongly preferred by the participants due to the perceptive feeling in performance.

Assessment of joystick and wrist control in hand-held articulated laparoscopic prototypes

BACKGROUND

Various steerable instruments with flexible distal tip have been developed for laparoscopic surgery. The problem of steering such instruments, however, remains a challenge, because no study investigated which control method is the most suitable. This study was designed to examine whether thumb (joystick) or wrist control method is designated for prototypes of steerable instruments by means of motion analysis.

METHODS

Five experts and 12 novices participated. Each participant performed a needle-driving task in three directions (right → left, up → down, and down → up) with two prototypes (wrist and thumb) and a conventional instrument. Novices performed the tasks in three sessions, whereas experts performed one session only. The order of performing the tasks was determined by Latin squares design. Assessment of performance was done by means of five motion analysis parameters, a newly developed matrix for assigning penalty points, and a questionnaire.

RESULTS

The thumb-controlled prototype outperformed the wrist-controlled prototype. Comparison of the results obtained in each task showed that regarding penalty points, the up → down task was the most difficult to perform.

CONCLUSIONS

The thumb control is more suitable for steerable instruments than the wrist control. To avoid uncontrolled movements and difficulties with applying forces to the tissue while keeping the tip of the instrument at the constant angle, adding a "locking" feature is necessary. It is advisable not to perform the needle driving task in the up → down direction.