Robotic Suturing
Fundamentals of proper surgical suturing require an opposition of tissue planes in a manner that facilitates healing while limiting the inflammatory response and damage to surrounding tissue. Hypothetical benefits of telerobotic surgery over traditional minimally invasive instrumentation are provided through tremor filtration, motion scaling, articulation and improved ergonomics. While surgical suturing seems like a natural application of the increased intracorporeal dexterity afforded by this refined technology, there are a multitude of factors involved which obfuscate such an apparent revelation.
Introduction:
The placement of sutures to oppose tissue planes depends on a number of factors. These factors are dependent not only on a surgeon’s technical abilities but rather a multitude of variables ranging from medical comorbidities to operating room staffing. This chapter will provide a background in basic technique as well as a review of individual studies to suggest a context for the evolution of robotic suturing.Method:
A systems approach and component evaluation of the steps necessary to telerobotically oppose tissue planes is merited. Critical studies of surgical systems such as laparoscopy, robots or virtual reality simulators that inherently evaluate the kinematics and dynamics of the steps of the procedure benefit from a regimented methodology for both analysis of efficacy and objective evaluation.[1] This systems approach is beneficial not just for the individual steps in knot tying or port placement but also the entire design of the operating rooms as well as the rolls of the individuals participating in the operating room suite. In other words the proper design of the entire operating room experience is critical in minimally invasive surgery so that surgeons may dedicate their physical and mental energy toward the technical and anatomic challenges of the operation instead of the mechanics of the instrumentation. [2] Not only can the physical efficiency of the individual actions behind minimally invasive suturing be improved by such an approach, [3] but in a more global context, minimally invasive surgery is performed more efficiently in a dedicated surgical suite versus a traditional operating room. [4]Theory and History
Surgical techniques of suturing share similar goals- the creation of an anastomosis safely, rapidly and efficiently. An ideal technique limits the amount of intramural foreign body and tissue trauma with the expectation of a decreased inflammatory response. Ideal results achieve rapid and substantial healing in a systemic manner that minimizes intersurgeon variability. Paramount to the description of surgical anastomosis was Lembert’s treatise that serosa-to-serosa approximation was necessary to provide early adhesion formation and subsequent permanent anastomotic strength. [5] Shortly thereafter, Halstead demonstrated that it is actually the submucosal layer and not the serosa that is responsible for the strength and integrity of the intestines. [6] Although anatomic layers vary between tissues, coaptation of wound surfaces is necessary to provide conditions for primary wound healing. Sutures however are foreign bodies with potentially negative effects on the healing process. [7, 8] Inflammatory reaction in a wound is caused both by the injury to the tissues as well as foreign material present in the wound area. Increased trauma by the passing of needles and sutures and the presence of excess suture material exaggerates and or prolongs the inflammatory reaction in the wound region. Brunius confirmed these findings and demonstrated a prolongation of the inflammatory reaction when sutures were used. [9] The adage of ‘do no harm’ holds true to surgical suturing. Sutures should be used to approximate tissue planes so that the body’s natural mechanisms for healing are least disrupted. Sutures placed by hand through the wall of the gut produce local inflammation at the anastomosis regardless of the type of suture because it is the penetration of the suture through the bowel layers that initiates this response[10]. There have been many different technologies developed to aid in surgical anastomosis over the last 100 years. Denans’ rings which used two solid rings of identical dimensions, placed inside of each end of transected intestine and joined together by an expanding cylinder coil.[11] This was followed by the Murphy button which consisted of two hemispheric ends placed inside the bowel and screwed together to form the anastomosis.[12] 1972 Clarke described a simple and satisfactory method of suture ligation with a basic technique of extracorporeal knot tying. [13]Ergonomics:
Laparoscopic suturing is limited by the design of the instrumentation compounded by small working spaces and fixed angles at the trocar level to place sutures. A comparison of the physical effort required for laparoscopic and open surgical has been quantitated but deserving special mention is that there is both increased physical and cognitive work that a minimally invasive surgeon must employ to overcome the separation between the surgeon and the operating field. In comparison with open surgery where the surgeon views and manipulates patient’s tissues directly and naturally using simple and efficient instruments, the laparoscopic surgeon must view the operating file indirectly through an optical and video system and simultaneously manipulate tissues using more complex and less efficient instruments. Under these conditions, the laparoscopic surgeon has to work harder from the very beginning to achieve the same technical goals as those of open surgery. [14] A typical disposable laparoscopic grasper transmits the force of the surgeon’s hand from the handle to the tip with a ratio of only 1:3 in contrast to a 3:1 ratio with a hemostat. [15] The surgeon must therefore work about 6 times as hard to accomplish the same grasping task with the laparoscopic instrument. [16] Excessive wrist angulation, whether flexion/extension or radial/ulnar deviation, decreases the efficiency of the forearm muscle actuating the hand and fingers and increases carpal tunnel pressure.[17, 18] Electromyographic (EMG) signals and body part discomfort scores are higher during laparoscopic knot tying versus its open correlate. Complex manipulative tasks using laparoscopic techniques require substantially higher upper-extremity muscle effort compared with open surgical techniques.[19] Three categories of hand and wrist problems are typically described usually occurring after a prolonged high grasping force has been applied to an instrument. These problems include compression neuropathies and pressure injuries to the soft tissues of the hands and fingers, wrist pain and hand fatigue. Typically the surgeon might recollect a vague discomfort during the procedure but later describes numbness and pain in the distribution of the digital nerves. The results of long-term injury on laparoscopic surgeons are largely unknown. A series of studies largely with retrospective questionnaire have evaluated neuromuscular complaints in minimally invasive surgeons. Hand-assisted laparoscopy is associated with more frequent neuromuscular strain to the upper extremity than standard laparoscopy, but standard laparoscopic surgeons experience more neck pain or injury. [20] Case reports of laparoscopic tubal anastomosis repeatedly are associated with surgeon fatigue, neck, shoulder, and back pain. Surgeons in these small case studies who compare the procedures to robotic-assisted operations typically describe the later as more comfortable and with less physical fatigue. [21, 22]. This point has also been made in the description of thoracic robotic procedures. [23]
Cognitive Benefits of Robotic Suturing:
Minimally invasive intracorporeal suturing is a stressful task. Compounding the stress of this technical challenge are the significant cognitive challenges for the laparoscopic surgeon who must overcome the physical separation of the visual and physical aspects of the operation. The surgeons must ‘blend’ or bring together the view on the display and the mechanical feedback from the arms and hands in order to dexterously manipulate the tissues. A definite cognitive expenditure is involved with reconstructing the 3D workspace from the 2D television screen. Although the use of performance efficiency measures (speed, movement economy, errors) and ergonomic assessments are relatively well established, the evaluation of cognitive outcomes is rare. Assessment strategies that include mental workload measures act as a way to improve training scenarios and training/operating environments. These mental workload measures can be crucially important in determining the difference between well-intentioned but subtly distracting technologies and true breakthroughs that will enhance performance and reduce stress.[24] The visual and physical interfaces involved with laparoscopic knot tying have been shown to cause greater stress levels in surgeons as measured by tonic skin conductance level, electrooculogram measuring number of blinks as well as subjective reports of stress.[14] Robotics with its comfortable counsel and intuitive interface would be expected to decrease the stress of complicated procedures. Participants with no experience as primary surgeons in endoscopic surgery performed a set of simulated surgical tasks using robotics and a traditional manual endoscopic surgery system. Given identical tasks, the time to completion was longer using the telerobotic technique than its manual counterpart. Despite the increased operative time, a questionnaire measuring the participants' intuitiveness and mental stress and the upper extremity postural analysis suggested that telerobotic surgery provided a more comfortable environment for the surgeon without any additional mental stress.[25] Exact quantification of decreased stress is difficult to substantiate especially considering the confounding factor of the learning curve involved with the new technology and the systems involved. Berguer however evaluated electromyographic data, skin conductance and perceived difficulty to measure both laparoscopic novices and experts performing bench tasks. Robotic techniques appear slower and less precise than laparoscopic technique for simple tasks, but equally fast and possibly less stressful for complex tasks. His studies also suggested that previous laparoscopic experience has a complex influence on the physical and mental adaptation to robotic surgery.[26] The operating room environment no doubt also compounds the influence of experience. Kolvenbach reports a series of minimally invasive aneurysm repairs using traditional laparoscopic instrumentation as well as robotic-assisted operations. The time to suture the aortic anastomosis was significantly shorter in the robotic-assistance group yet total operating time was longer because of the technical complexity of the robotic device. [27] Although mental stresses of the operating room environment are present for laparoscopic and robotic procedures, an operating room team that is not yet comfortable with robotic procedures may also increase the stress of the robotic operator.
3D Visualization as it Applies to Surgical Suturing
:Stereoscopic vision provides a significant advantage during when table drills of increasing complexity are performed with the robotic system in 3D mode compared to 2D mode. [28, 29] Suturing skill sets evaluated with table anastomosis drills also demonstrate this pattern with anastomosis completed 65% faster using 3D with equal, if not greater, accuracy. [30] More complicated evaluations have been performed comparing motion path analysis of robotic surgery compared to laparoscopy. Moorthy et. al and the team at St Mary’s Hospital used the da Vinci API for motion path analysis of positional data to demonstrate enhanced dexterity reduction in path traveled in terms of by nearly 50% as compared to laparoscopic surgery. 3-D vision enhanced measures of dexterity by a further 10-15%. The presence of 3-D vision results in a 93% reduction in skills-based errors and was required for the robotic operators to have a significant reduction in time taken when compared to their laparoscopic cohort. [31]
Narrow Working View and Suture Manipulation:
The greater magnification and improved optics of the da Vinci system also contributes to some problems with suturing for both inexperienced as well as expert users. Although there are few systemic analyses of novice intracorporeal robotic versus laparoscopic anastomoses, the greater magnification sometimes predisposes novel robotic users to place a greater number of sutures per unit area than what is traditionally done with the laparoscopic anastomosis. A problem that is a function of working in a small workspace is the increased manipulation of the length of the suture material. While the manipulation of the needle is made easier, the manipulation of the suture itself is more difficult. When working in a narrow field of view, it is often necessary to zoom out of the visual field of the anastomosis in order to track the motion of the robotic arms as the slack in the suture is tightened. Another difficulty with working with suture material in both laparoscopy and robotics lies within the problems with grasping the suture material. Some materials especially proline, do not have a h3 transverse fracture strength, therefore when the robotic graspers are used to pull up on the suture and draw out the remaining length of the suture, it requires applying force without haptic feedback to grip the suture material. The weakening of the sure can lead to another cause of possible disruption line. After infliction of controlled damage with laparoscopic needle holders, sutures of various materials had significantly reduced tensile strength and impaired extension compared with control sutures.[32] The passage of a suture into the operating field is also more difficult with robotic procedures. The 8mm Intuitive ports do not accommodate most curved needles and an additional working port is needed. Although the robotic exterior arms can be removed out of position this is notably more difficult than laparoscopy where such an action does not necessitate any more of an increase work than a standard instrument change. A novel idea, which has recently been introduced, is the concept of modified suture design specific for intracorporeal minimally invasive suturing and knot tying. A modified suture allowed inexperienced surgical residents to perform intracorporeal laparoscopic knot tying on average faster than the standard suture did. The concept of modifying suture design to facilitate intracorporeal laparoscopic suturing and knot tying will most likely receive further attention. [33]
Haptic Feedback:
The application of robotic end wrist technology aids certain characteristics of surgical suture placement. The increased number of degrees of freedom facilitate complex motion tasks and in the execution of more natural circular wristed movements. Although this technology facilitates the task of following the arc of the needle as it passes through various tissues, the lack of haptic feedback implies a difficulty in judging the consistency of the tissue that has been encompassed by the arc of the needle. Additional difficulties arise as it is difficult to gauge the tension that is placed on each stitch causing both suture line tension and the tissue tension (i.e. the surgical adage of ‘approximation and not strangulation’) to rely on visual cues only. This difficulty is also found in surgical knot tying which is especially problematic, as a perfectly sutured running anastomosis can be rendered incompetent with a loose knot. End-to-end anastomosis on post-mortem porcine small intestine was evaluated in experienced endoscopic surgeons performing standard endoscopic techniques and with robotic assistance. Anastomosis time, number of stitches, and the number of knots did not differ significantly between the two groups. The time needed per stitch was significantly shorter with robot assistance however more suture ruptures occurred in the robot group due to the lack of force feedback. Total anastomosis time was not demonstrated to be shorter but fewer stitch errors were found in the robotic group. [34] Preliminary studies describe evidence that haptic feedback, in the form of sensory substitution permits the surgeon to apply more consistent, precise, and greater tensions to fine suture materials without breakage during robot-assisted knot tying.[34, 35]. This is not to say that haptic feedback is a prerequisite for surgical suturing but rather than certain caveats must be reinforced. Gentleness in handling tissues has been found to be mandatory in closing the contaminated wound. Sutures tied tightly around wound edges markedly increase the incidence of wound infection because of the strangulation of tissue within the suture loop and its associated lowering of the hosts’ defenses.
Microsurgical Anastomoses and Tremor Filtration:
Microsurgery typically employs sutures 7-0 to 10-0 which are too small to be seen by the naked eye. The fragility of these sutures also implies that reliance on haptic feedback even during traditional open procedures is minimized. With increased visualization, scaling of movements and the benefits of tremor filtration microsurgery thus seems like an ideal application for robotic surgery. Studies typically demonstrate that minimally invasive robotic microanastomoses are feasible however of no increased benefit to the open procedure. Studies typically are limited to the endpoint of an intact anastomosis that can withstand a saline infusion test and do not evaluate a more holistic view of minimally invasive versus open surgery. The use of the Zeus robot was used to compare end-to-end microvascular anastomoses in 1-mm rat femoral arteries with interrupted 10-0 suture. The authors describe the robotic tremor filtration as remarkable however note that because all anastomosis were patent, none leaked and because anastomosis done by hand (17.2 minutes were significantly faster than those done with Zeus 27.6 minutes p <.01) there was no measurable benefit from the tremor filtration and motion scaling offered by robot-enhanced surgery. [36] Kuang and colleagues evaluated the technically difficult vasovasotomy performed with 9-0 sutures and the conventional microscope versus the robot. Pre-specified performance measures and adverse haptic events (broken sutures, bent needles or loose stitches) were recorded. Patency was evaluated by instilling saline through the anastomoses. Mean operating time differed significantly (84 vs. 38 minutes p=0.01) and numbers of adverse haptic events were higher for RAVV than for MAVV (84 vs 38 minutes, p = 0.01; 2.4 vs 0.0 events, p = 0.03). The number of needle passes required for the 6 full-thickness stitches was similar in both groups (16.8 vs 15.2 passes, p = 0.55). All anastomosis were evaluated by instilling saline and demonstrated to be patent. These authors also remarked about the noticeable elimination of tremor and commented about the use of the robot as a surgical alternative for microsurgical vasovasostomy.[37] These studies are particularly relevant because they demonstrate that robotics is feasible for the most delicate anastomoses. Of note is that the comparison has changed. As these procedures are impossible with traditional laparoscopic graspers, robotics is no longer compared to laparoscopy but rather to the open operations.
Learning Curves:
Considerable training is necessary to master laparoscopic suturing and knot-tying. These difficult skills contribute to reasons why advanced laparoscopic procedures have been met with certain reluctance. On initial examination, robotic systems are assumed to facilitate these difficult skills with a steeper learning curve that requires less time to master. This assumption is not always supported by laboratory data. Consistent conclusions are difficult to surmise considering the variety of different drill sets that are employed to investigate subtle changes in groups of novices and experts with varying levels of experience. Robotic suturing in an ex-vivo bench test is quickly learned. Hernandez et. al demonstrated a very efficient learning curve for the novices using the da Vinci system for a series of synthetic small bowel anastomosis. Quantitative analysis used API software to retrieve real-time robotic signal data of time, path length, and number of movements. The first compared to the fifth anastomosis took considerably less time (3507 sec vs. 2287 sec (p < 0.01), total number of movements (2411 vs. 1387 (p = 0.01), total path length (21,630 cm vs. 13,941 cm (p =0.01). [38] Anderson-Hynes pyeloroplasty and Fengerplasty performed with the da Vinci robotic system resulted in overall decreased operative time compared to laparoscopic pyeloroplasty however factors responsible for the decreased operative time were not clearly defined.[39] Yohannes et. al evaluated a series of bench trials to evaluate the differences in learning curves between laparoscopy and robotics. Both groups demonstrated a statistically significant improvement between the first and last trial. There were some differences in the laparoscopic learning curves in favor of robotic assistance however not for overall improvement.[40] Conversely, a study evaluating an ex vivo vascular anastomosis using the Zeus-Aesop system demonstrated equivalent results but with significant longer suture and knot tying time and significant more actions were needed compared to the manual laparoscopic procedures. [41] These ex vivo results are both dependent on the task evaluated and operator experience dependent. Nio et. al. evaluated a laparoscopically experienced surgeon and a laparoscopically inexperienced surgeon making alternating laparoscopic vascular anastomoses and robot-assisted laparoscopic vascular anastomoses. The learning curves of both surgeons were not improved by the robotic system. Neither laparoscopic method influenced the quality score or leakage rate, but with laparoscopic experience, significantly fewer failures were made. Suturing and knot-tying were faster with laparoscopic experience both with and without the robotic system, and fewer stitch actions and knot actions were performed.[41, 42]. Bergeurs’ studies also suggested that previous laparoscopic experience has a complex influence on the physical and mental adaptation to robotic surgery. [26] Although studies seem to suggest equivalency between the two techniques, the comparison between learning curves still remains difficult. Laparoscopic suturing is challenging when port placement or visualization is compromised not when the evaluating an ex vivo learning skills task. Early ex vivo studies (i.e. performing peg-board tasks) demonstrated that laparoscopic maneuvering and suturing is faster and just as precise when performed manually as when performed with the prototype robotic system with differences in speed are inversely proportional to the size of the suture.[21] These findings might represent an investigator-derived task that is particularly well suited to laparoscopy harkening the need for a regimented skill set as evaluations of surgical skill become more common both in the evaluation of surgical skill as well as evaluations of new technologies.
Future Applications:
A glimpse into the future of robotic suturing is perhaps heralded by a short reflection on past developments. The tenants of surgical suturing are based on atraumatic opposition of tissue in a manner that achieves rapid healing, minimizes an inflammatory response as well as intersurgeon variability. An examination of future suturing applications needs to acquiesce that all these criteria are better met with surgical stapling devices that share both an decreased inflammatory response as well as accelerated wound healing.[10] The difficulties of using the robotic device outweigh many of the proposed benefits of tremor filtration and scaling of motions in early attempts at complex microanastomotic procedures. The increases in cardiopulmonary bypass time have limited the acceptance of robotic totally endoscopic coronary artery bypass grafting as well as complex vascular repairs requiring aortic cross-clamp. [27] Although coronary artery and valve suturing initially seemed like ideal applications, time limits are causing surgeons to move away from the suturing abilities of the robot in favor of other facilitating technologies such as the use of nitinol U-clips for mitral valve repairs [43] and the favoring of anastomotic coupling devices to facilitate beating heart totally endoscopic coronary artery bypass grafting. [41] Again, it is important to note that minimally invasive suturing was previously deemed impossible prior to the introduction of robotics. The technical superiority of the robotic device over laparoscopic suturing is evident in complex microanastomses where laparoscopic approaches are not tenable and the robot seems to at least be equivalent to the open microsurgical approaches. In the near future, robotic suturing will play an invaluable role in urologic and gynecologic procedures that need minimally invasive microanastomses in the narrow confines of the bony pelvis and are not limited by the same time constraints as cardiac surgery. Eventually robotics will also be applied to endoscopic suturing which is already being studied with histological evaluation of suture depth placement [44] and automated devices to facilitate suture placement and knot tying. [45] In the distant future, telerobotic master-slave devices will evolve into ‘true’ surgical robots. API data that is currently being gathered from research groups performing methodological component evaluation of surgical suturing will be used to increasingly automate the suturing process and eventually entire surgical procedures. There will be a time when the robot performs the surgery with surgeon playing a supervisory role. [1]
Conclusion:
There is considerable overlap with the number of surgeons who regularly perform complex laparoscopic and robotic procedures that require intracorporeal suturing. Robotics is still in its infancy and although the technology is indeed ‘intuitive’, the machines are currently being used only by centers that can afford them. It is rare that surgeons who do not have advanced laparoscopic training perform robotic operations. Long-term prospective follow-up of procedures performed with or without the da Vinci robotic system for surgeons with limited experience in laparoscopic management will help delineate the true efficacy of the device. Perhaps with concurrent development of medical advances and facilitating technologies such as visual overlays there will be a physiologic reason to demand increased minimally invasive precision. Tasks that are easy to perform with traditional laparoscopic instrumentation are not improved with robotic instrumentation. Learning curves for simple ex vivo tasks are not improved for novices and a machine that promises increased precision does not necessarily correlate with improved clinical outcomes. Robotic suturing is superior to traditional laparoscopic approaches only by experienced operators in the correct context. Minimally invasive robotic approaches are however possible and comparable to open microsurgical anastomoses that traditionally had to be performed with a microscope. Prior to the adaptation of the device for urologic and gynecologic procedures, the perils of increased cross-clamping times in cardiovascular surgery limited its clinical practicality. The increased use as well as the exponential growth of urologic robotic procedures is perhaps more indicative of the future of the technology rather than studies which are brief glimpses of the technology in an artificial environment.
Bibliography:
1. Rosen, J., et al., Minimally invasive surgery task decomposition--etymology of endoscopic suturing. Stud Health Technol Inform, 2003. 94: p. 295-301.
2. Lai, F. and E. Entin, Integrating surgical robots into the next medical toolkit. Stud Health Technol Inform, 2005. 119: p. 285-7. 3. Neo, E.L., M. Patkin, and D.I. Watson, Suturing efficiency during hiatal repair for laparoscopic fundoplication. ANZ J Surg, 2004. 74(1-2): p. 13-7. 4. Hsiao, K.C., Z. Machaidze, and J.G. Pattaras, Time management in the operating room: an analysis of the dedicated minimally invasive surgery suite. Jsls, 2004. 8(4): p. 300-3.
5. Lembert, A., Nouveau procede d'enterorraphie. Repertoire. General d'anatome et de Physiologic Pathologique, 1826(2:3).
6. Halsted, W., Circular suture of the intestine- An experimental study. Am J Med Sci, 1887. 94: p. 436-461.
7. Postlethwait, R.W., D.A. Willigan, and A.W. Ulin, Human tissue reaction to sutures. Ann Surg, 1975. 181(2): p. 144-50.
8. Van Winkle, W., Jr. and J.C. Hastings, Considerations in the choice of suture material for various tissues. Surg Gynecol Obstet, 1972. 135(1): p. 113-26.
9. Brunius, U., B. Zederfeldt, and C. Ahren, Healing of skin incisions closed by non-suture technique. A tensiometric and histologic study in the rat. Acta Chir Scand, 1967. 133(7): p. 509-16.
10. Ballantyne, G.H., The experimental basis of intestinal suturing. Effect of surgical technique, inflammation, and infection on enteric wound healing. Dis Colon Rectum, 1984. 27(1): p. 61-71.
11. Denans, F.N., Nouveau procede pour la guerision des plaies des intestins. Recueil de la Societe Royal de Medicine de Marseille, 1827: p. 127-131.
12. Murphy, J., Cholecysto-intestinal, gastro-intestinal anastomosis and approximation without sutures. Med Rec, 1892. 42: p. 335-337.
13. Clarke, H.C., Laparoscopy--new instruments for suturing and ligation. Fertil Steril, 1972. 23(4): p. 274-7.
14. Berguer, R., W.D. Smith, and Y.H. Chung, Performing laparoscopic surgery is significantly more stressful for the surgeon than open surgery. Surg Endosc, 2001. 15(10): p. 1204-7.
15. Berguer, R., Surgical technology and the ergonomics of laparoscopic instruments. Surg Endosc, 1998. 12(5): p. 458-62.
16. Berguer, R., D.L. Forkey, and W.D. Smith, The effect of laparoscopic instrument working angle on surgeons' upper extremity workload. Surg Endosc, 2001. 15(9): p. 1027-9.
17. Johnson, S.L., Ergonomic hand tool design. Hand Clin, 1993. 9(2): p. 299-311.
18. Winzeler, S. and B.D. Rosenstein, Occupational injury and illness of the thumb. Causes and solutions. Aaohn J, 1996. 44(10): p. 487-92.
19. Berguer, R., J. Chen, and W.D. Smith, A comparison of the physical effort required for laparoscopic and open surgical techniques. Arch Surg, 2003. 138(9): p. 967-70.
20. Johnston, W.K., 3rd, B.K. Hollenbeck, and J.S. Wolf, Jr., Comparison of neuromuscular injuries to the surgeon during hand-assisted and standard laparoscopic urologic surgery. J Endourol, 2005. 19(3): p. 377-81.
21. Margossian, H., et al., Robotically assisted laparoscopic tubal anastomosis in a porcine model: a pilot study. J Laparoendosc Adv Surg Tech A, 1998. 8(2): p. 69-73.
22. Falcone, T., et al., Full robotic assistance for laparoscopic tubal anastomosis: a case report. J Laparoendosc Adv Surg Tech A, 1999. 9(1): p. 107-13.
23. Garcia-Ruiz, A., et al., Robotic surgical instruments for dexterity enhancement in thoracoscopic coronary artery bypass graft. J Laparoendosc Adv Surg Tech A, 1997. 7(5): p. 277-83.
24. Carswell, C.M., D. Clarke, and W.B. Seales, Assessing mental workload during laparoscopic surgery. Surg Innov, 2005. 12(1): p. 80-90.
25. Lee, E.C., et al., Ergonomics and human factors in endoscopic surgery: a comparison of manual vs telerobotic simulation systems. Surg Endosc, 2005. 19(8): p. 1064-70.
26. Berguer, R. and W. Smith, An Ergonomic Comparison of Robotic and Laparoscopic Technique: The Influence of Surgeon Experience and Task Complexity. J Surg Res, 2005.
27. Kolvenbach, R., et al., Total laparoscopically and robotically assisted aortic aneurysm surgery: a critical evaluation. J Vasc Surg, 2004. 39(4): p. 771-6.
28. Munz, Y., et al., The benefits of stereoscopic vision in robotic-assisted performance on bench models. Surg Endosc, 2004. 18(4): p. 611-6.
29. Jourdan, I.C., et al., Stereoscopic vision provides a significant advantage for precision robotic laparoscopy. Br J Surg, 2004. 91(7): p. 879-85.
30. Badani, K.K., et al., Comparison of two-dimensional and three-dimensional suturing: is there a difference in a robotic surgery setting? J Endourol, 2005. 19(10): p. 1212-5.
31. Moorthy, K., et al., Bimodal assessment of laparoscopic suturing skills: construct and concurrent validity. Surg Endosc, 2004. 18(11): p. 1608-12.
32. Bariol, S.V., G.D. Stewart, and D.A. Tolley, Laparoscopic suturing: effect of instrument handling on suture strength. J Endourol, 2005. 19(9): p. 1127-33.
33. Tan, A. and H. Razvi, Evaluation of a novel modified suture material designed to facilitate intracorporeal knot tying during laparoscopic surgery. J Endourol, 2005. 19(9): p. 1104-8.
34. Bethea, B.T., et al., Application of haptic feedback to robotic surgery. J Laparoendosc Adv Surg Tech A, 2004. 14(3): p. 191-5.
35. Kitagawa, M., et al., Effect of sensory substitution on suture manipulation forces for surgical teleoperation. Stud Health Technol Inform, 2004. 98: p. 157-63.
36. Knight, C.G., et al., Computer-assisted, robot-enhanced open microsurgery in an animal model. J Laparoendosc Adv Surg Tech A, 2005. 15(2): p. 182-5.
37. Kuang, W., et al., Initial evaluation of robotic technology for microsurgical vasovasostomy. J Urol, 2004. 171(1): p. 300-3.
38. Hernandez, J.D., et al., Qualitative and quantitative analysis of the learning curve of a simulated surgical task on the da Vinci system. Surg Endosc, 2004. 18(3): p. 372-8.
39. Gettman, M.T., et al., A comparison of laparoscopic pyeloplasty performed with the daVinci robotic system versus standard laparoscopic techniques: initial clinical results. Eur Urol, 2002. 42(5): p. 453-7; discussion 457-8.
40. Yohannes, P., et al., Comparison of robotic versus laparoscopic skills: is there a difference in the learning curve? Urology, 2002. 60(1): p. 39-45; discussion 45.
41. Nio, D., et al., The efficacy of robot-assisted versus conventional laparoscopic vascular anastomoses in an experimental model. Eur J Vasc Endovasc Surg, 2004. 27(3): p. 283-6.
42. Nio, D., et al., Laparoscopic vascular anastomoses: does robotic (Zeus-Aesop) assistance help to overcome the learning curve? Surg Endosc, 2005. 19(8): p. 1071-6.
43. Felger, J.E., et al., Robot-assisted sutureless minimally invasive mitral valve repair. Surg Technol Int, 2004. 12: p. 185-7.
44. Kleemann, M., et al., Depth of endoscopically placed sutures: an experimental study in a human cadaver model. Surg Endosc, 2005. 19(12): p. 1602-5.
45. Swain, P. and P.O. Park, Endoscopic suturing. Best Pract Res Clin Gastroenterol, 2004. 18(1): p. 37-47.