The da Vinci ® Surgical System Overcomes Innate Hand Dominance

Introduction

T he da Vinci ^® surgical system (Intuitive Surgical Inc., Sunnyvale, CA) has experienced widespread acceptance and growth since its introduction more than 10 years ago. ^1,2 The popularity and success of robotics as a surgical tool is multifactorial; however, properties inherent to the da Vinci robot, such as seven degrees of freedom, three-dimensional (3-D) vision, tremor filtration, motion scaling, and enhanced instrument precision may have contributed to the speed and widespread adoption of the system. ³ The da Vinci robot is a computer-assisted telemanipulator, which uses a master-slave system. ¹ The surgeon is able to control the movements of the robotic arms from an ergonomic console with 3-D vision, and the slave unit carries out each movement of the surgeon. These movements should, in theory, also reflect the surgeon's innate difference in dexterity between each hand.

The lateralization of chirality, or handedness, is defined as the unequal distribution of fine motor skills between the left and right hand. Handedness is an innate characteristic of a surgeon and, in general, does not limit the overall ability of a surgeon to perform a surgical task. Many surgeons, however, perform complex and critical tasks, such as throwing sutures or fine dissection, with their dominant hand exclusively, either as a preference or out of necessity. While tasks with the dominant hand can be performed in an open fashion by readjusting one's body position, laparoscopic or robot-assisted surgery often necessitates performing tasks such as fine dissection or placement of sutures with the nondominant hand. This is seen with the completion of a vesicourethral anastomosis during robot-assisted radical prostatectomy.

We examine the impact of the da Vinci robot on surgeon handedness during basic manual dexterity skill tasks to determine whether this platform can potentially reduce or eliminate intraoperative handedness, giving a surgeon more freedom to perform delicate tasks.

Methods

After University of California Institutional Review Board approval, volunteers for the study were solicited during a combined urology and anesthesia training program that was designed to introduce residents to the functionality of the da Vinci surgical system. Residents with all levels of training and experience with the robotic system were invited to participate in the study. Each participant, regardless of robotic experience, underwent a short tutorial on the capabilities of the da Vinci robot (standard—first generation) and was given time (approximately 30 minutes) to practice basic exercises (ring transfer, passing needles through targets, and robotic knot tying) using the robot before entry into the study. All subjects were also asked to fill out a short demographics questionnaire.

Manual dexterity was assessed using two different skill tests: The Purdue Pegboard Test and a standard targeting test. The Purdue Pegboard is a validated test of manual dexterity initially used to evaluate the skills and dexterity of factory workers. ⁴ In the “open” testing, subjects were asked to place as many peg assemblies within the board as possible within 30 seconds using their dominant hand. Participants had the opportunity to practice before the testing. After performing the task with the dominant hand, their nondominant hand was then tested. Each hand was tested twice, and the scores were averaged.

During the “robotic” testing phase of manual dexterity, the Purdue Pegboard was again used to test differences in handedness while using the robot. Participants were asked to place as many pegs into the board as possible within a 30-second interval. All tasks were performed with a standard Maryland bipolar grasper commonly used on the da Vinci robot. The robotic patient cart setup was standardized for all subjects. The arms were placed in a previously marked set position with the camera positioned so that only the arm being tested needed to move to grab and place the pegs. This setup was designed to eliminate the need for camera movements or clutching during the testing—factors that could potentially influence performance and handedness comparisons. Each hand was tested twice, and the scores were averaged.

Needle targeting during open testing was performed using a standard Keith needle and a 5½ inch Kelly clamp. The needle was grasped 2 cm above the needle point and at a right angle with the Kelly clamp. Paper targets with a 1-mm diameter bull's-eye were placed on a rubber backer board, and each subject had 10 seconds to hit as many bull's-eyes as possible. Only bull's-eyes (>90% of the hole created was within the marked bull's-eye) were counted as a score. Again, the dominant hand was tested first, followed by the nondominant hand. Each hand was tested twice, and the scores were averaged.

During the robotic testing phase, the Keith needle was grasped 2 cm above the tip with a standard large needle driver. As with the Purdue Pegboard testing, the robotic arms were standardized to a set position that was marked on the robot and did not vary among subjects. The camera was positioned so that only the arm being tested needed to move to hit the targets. Each subject was given 30 seconds to hit as many targets as possible, and again, only bull's-eyes were considered a score. Each hand was tested twice, and the scores were averaged.

For each test described above, open and robotic, subjects performed the task with their dominant hand first, followed by their nondominant hand. All subjects completed the open testing before performing the robotic testing. All data were analyzed using Stata Version 9.0 (Stata Corp, College Station, TX). Averaged scores between the dominant and nondominant hand on the open and robotic tasks were compared using paired Student t test. A P value of < 0.05 was considered significant.

Results

Most of the subjects were anesthesia residents (68%), and the remaining participants were urology residents (32%). All subjects had little or no robotic experience before participating in the study, and only one participant had used the robot during a clinical operative case. Handedness and perceived level of dexterity among subjects is shown in Table 1. Most subjects were right handed (84.2%) and thought that their dominant hand was significantly more dexterous than their nondominant hand (79%). No subjects were ambidextrous or thought their manual dexterity was equal between hands.

The dexterity assessment of all subjects on the Purdue Pegboard Test and needle targeting test in both the open and robotic approaches are shown in Table 2. There was a significant difference in manual dexterity between the dominant and nondominant hands in both open pegboard scores and needle targeting. This difference, however, was not seen when using the robot.

When the subjects were broken down by handedness, right-handed persons had significant differences between the right and left hand in open pegboard scores (15.6+1.1 vs 14.6+1.5, P=0.040) and needle targeting (4.5+1.6 vs 3.6+1.2, P=0.019), while this difference was not observed in the three left-handed subjects (P=0.546 and P=0.089, respectively). There were no differences between the left and right hands while using the robot among right- or left-handed persons (data not shown).

Discussion

The widespread adoption and growth of robotics in the field of surgery over the past decade have been facilitated by features of the da Vinci robot that have allowed novice surgeons to overcome some of the technically challenging aspects of traditional laparoscopy, aspects thathave curtailed similar growth and adoption of pure laparoscopic surgery for complex reconstructive and extirpative procedures. These features are not without trade-off, however, as the surgeon is no longer at the bedside “scrubbed in” with the patient. Also, with current technologies, there is a lack of haptic feedback using the robotic interface. ² Notwithstanding these limitations, surgeons have adapted to this new interface and have consistently shown that robot-assisted prostate and kidney surgery can produce similar outcomes to laparoscopic or open techniques. ^{5 –7}

In this study, we attempted to discern whether the mechanization of tasks using the da Vinci robot could diminish or eliminate the innate lateralization of manual dexterity seen among the majority of surgeons. Laparoscopic and robotic surgeons are often faced with using their nondominant hands to complete critical tasks during an operation, such as the vesicouretheral anastomosis during radical prostatectomy or the placement of sutures during partial nephrectomy. We are the first to show that the da Vinci robot does, in fact, help eliminate handedness in tests of manual dexterity.

A small number of studies have examined dexterity-related capabilities of the da Vinci robot. Moorthy and associates ⁸ demonstrated enhanced manual dexterity in surgically related tasks using the robotic system when compared with laparoscopic surgery in 10 surgeons with various degrees of laparoscopic expertise. They found that the performance of tasks using the robotic interface resulted in decreased hand movements and time to place and tie knots. Their tasks, however, required the use of both hands, and they did not examine the effect of the robot on surgeon handedness. Chandra and colleagues ⁹ also examined the performance of suturing tasks using both the laparoscopic and robotic platforms and found that, regardless of laparoscopic experience, subjects performed better using the robot on the majority of metrics assessed.

This study is the first, to our knowledge, to examine whether the da Vinci robot can help overcome handedness while performing tasks related to manual dexterity. We found that when subjects performed these tasks in an open fashion, there was a significant difference between the dominant and non-dominant hand for both the Purdue Pegboard Test and needle targeting test. These differences were eliminated when using the robotic interface. We also found that right-handed persons appeared to benefit the most from using the robot; however, our small number of left-handed subjects precludes any robust conclusions. Although the study focused solely on performing nonsurgical tasks, a yet unpublished study by our group has found that the time to complete a surgically related task (running a suture on a suture block) was no different using the right or left hand exclusively with the robotic system. This supports the idea that the robot may help to eliminate innate handedness during surgical procedures.

There are some limitations to this study. Only subjects with little or no robotic experience participated in the study, and more than half of the subjects also had limited open surgical experience. Differences between the dominant and nondominant hand may not be as pronounced among more experienced open and robotic surgeons. The study is also limited by the fact that the Purdue Pegboard is not validated for use with the da Vinci robot, although there is currently no validated system to test manual dexterity using the robot. This is reflected in the fact that there were less completed peg assemblies in the robotic testing portion than in the open testing for all subjects. We found that it was much more difficult and time consuming to grasp and orient a peg with a single robotic instrument compared with the open testing. This is also reflected in the fact that we allowed 30 seconds for the needle targeting portion of the testing using the robot and only 10 seconds in the open testing. It took much longer to orient and place the needle with the robot compared with open movements. There was also no standard laparoscopic arm in the testing. Finally, the study did not include surgically related tasks, but as stated, data yet unpublished from this group show that when surgeons were timed using the robot to suture exclusively with the left or right hand, there were no differences in time to completion.

The da Vinci surgical system has a number of characteristics that have facilitated the adoption of minimally invasive surgical techniques and has allowed surgeons to tackle more complex extirpative and reconstructive procedures. Reducing the innate differences in fine motor skills between our hands is another technical aspect of the da Vinci robot that may have contributed.

Conclusion

The da Vinci robot is capable of minimizing innate handedness among novice surgical trainees. This may explain improved comfort with suturing and dissection using the nondominant hand during robot-assisted surgery that has facilitated the adoption of robotics among surgeons even without advanced laparoscopic training.