robotic applications in abdominal surgery: their limitations and future developments

THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERYInt J Med Robotics Comput Assist Surg 2007; 3: 3–9. REVIEW ARTICLEPublished online 22 December 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/rcs.115

Robotic applications in abdominal surgery: theirlimitations and future developments

G. W. Taylor*D. G. Jayne

Academic Surgical Unit, Level 7,Clinical Sciences Building, St. James’sUniversity Hospital, Leeds LS9 7TF,UK

*Correspondence to: G. W. Taylor,Academic Surgical Unit, Level 7,Clinical Sciences Building, St.James’s University Hospital, LeedsLS9 7TF, UK.E-mail: [email protected]

Accepted: 24 October 2006

Abstract

Background In the past 20 years, the technical aspects of abdominal surgeryhave changed dramatically. Operations are now routinely performed bylaparoscopic techniques utilizing small abdominal incisions, with less patientdiscomfort, earlier recovery, improved cosmesis, and in many cases reducedeconomic burden on the healthcare provider. These benefits have largely beenseen in the application of laparoscopic techniques to relatively straightforwardprocedures. It is not clear whether the same benefits carry through to morecomplex abdominal operations, which are more technically demanding andfor which current laparoscopic instrumentation is less well adapted. The aimof surgical robotics is to address these problems and allow the advantages ofminimal access surgery to be seen in a greater range of operations.

Methods A literature search was performed to ascertain the current state ofthe art in surgical robotics for the abdomen, and the technologies emergingwithin this field. The reference lists of the sourced articles were also searchedfor further relevant papers.

Results Currently available robotic devices for abdominal surgery arelimited to large, costly ‘slave–master’ or telemanipulator systems, such as theda Vinci (Intuitive Surgical, Sunny Vale, CA). In addition to their size andexpense, these systems share the same limitation, by virtue of the fulcrumeffect on instrument manipulation inherent in the use of ports by whichexternal instruments gain access to the abdominal cavity. In order to overcomethese limitations several smaller telemanipulator systems are being developed,and progress towards freely mobile intracorporeal devices is being made.

Conclusions While current robotic systems have considerable advantagesover conventional laparoscopic techniques, they are not without limitations.Miniaturisation of robotic components and systems is feasible and necessaryto allow minimally invasive techniques to reach full potential. The ultimateextrapolation of this progress is the development of intracorporeal robotics,the feasibility of which has been demonstrated. Copyright 2006 John Wiley& Sons, Ltd.

Keywords abdominal surgery; laparoscopy, robotic surgical systems

IntroductionA revolution in abdominal surgery occurred 15–20 years ago with theintroduction of laparoscopic and minimally invasive techniques. Theadvantage of laparoscopic surgery was quickly realized, with smallerabdominal incisions resulting in quicker recovery, improved cosmesis,and shorter stay in a costly hospital bed. The safety, efficacy andcost-effectiveness of laparoscopic surgery has subsequently been demon-strated in clinical trials for many routine abdominal operations (1–4).However, the benefits of minimally invasive techniques have yet to

Copyright 2006 John Wiley & Sons, Ltd.

4 G. W. Taylor and D. G. Jayne

be translated across the whole range of abdominalsurgery. The case for laparoscopic surgery in morecomplex abdominal operations remains to be proved. Thisis largely due to the difficulties in learning and performingsuch procedures with current laparoscopic equipment,which is cumbersome, non-ergonomic, non-intuitive andlacking in adequate visual and tactile feedback.

In an attempt to overcome some of these problems,abdominal surgeons, like many of their counterparts inother surgical specialties, are turning to robotic surgicalsystems. A wide range of diagnostic and therapeuticrobotic devices are being developed (5), but those that arecurrently available for abdominal procedures are limitedto large, costly ‘slave–master’ telemanipultors, such as theda Vinci (Intuitive Surgical, Sunny Vale, CA). Althoughthis system offers several advantages, including three-dimensional (3-D) field of vision, intuitive instrumentmanipulation and enhanced dexterity, it is not without itsdrawbacks (6,7). It is an expensive, heavy and bulkypiece of equipment, which is difficult to manoeuvreand does not lend itself readily to current operatingtheatre design. The space occupied above and aroundthe patient creates issues relating to anaesthetic safety(8), in that rapid access to the patient in the eventof a cardiopulmonary collapse is difficult. In addition,although robotic systems offer excellent vision and precisetissue manipulation within a defined area, they do notreadily lend themselves to operations involving morethan one quadrant of the abdomen. Many gastrointestinaloperations involve operating in at least two abdominalquadrants, with varying states of patient ‘tilt’. This requiresrepeated docking and disengagement of the robot, whichadds significantly to the total operating time.

One solution to these problems is to miniaturize surgicalrobots for use as intra-abdominal devices. Engineers haveincreasing capabilities to create micro- and nanoscalecomponents and machinery, and it is important that thisis embraced within surgical technology.

Miniaturization

The need to make surgical robotic systems smallerhas been recognized by Intuitive Surgical, who have

developed the da Vinci-S (Figure 1A), with the ‘S’ beingfor ‘streamlined’. Other telemanipulator systems havebeen designed that take up less space in the operatingtheatre, including Active Trocar (9) (Figure 1B), fromthe University of Tokyo, and Laprotek (10) (endoVia,Norwood, MA). The group developing Active Trocarhave applied their expertise in simulation of humanmovement to enhance the degrees of freedom availablein a small space in order to make robotic arms smaller.The Laprotek system (Figure 1C) uses robotic arms fixedto the operating table to save operating theatre floorspace. Unfortunately, all these systems remain relativelybulky and still limit access to the patient. The lattertwo systems have been demonstrated in conjunction withsimple two-dimensional (2-D) displays rather than the3-D display integrated into the da Vinci console. Theytherefore save space in the operating theatre, but to datelack the important optical advantages of 3-D vision.

Another limiting factor of current systems is themechanism by which the end effectors are manoeuvredaround the abdomen, which remains external to thepatient. This limits access within the abdomen by virtueof the fact that the instruments are relatively fixed to theabdominal wall at their point of entry. The instrumentsare further restricted by this fulcrum effect, because theirinternal motion is mirrored and magnified outside thebody by the robotic arms, which have limited space tomove, leading to collisions.

A novel solution to this problem has been demonstratedat Nagoya University. The Hyperfinger (11) (Figure 2) hasbeen used to perform surgical tasks in in vivo experiments.This system works on the basis of a ‘slave’ endoscope withfour articulations mirroring the motion of an identicallyjointed ‘master’ control. The third generation of this deviceallows the end effector nine degrees of freedom, therebyimproving the access within the abdomen. Because mostof the moving parts are internalized, the space taken upin the operating theatre is much reduced when comparedto other telemanipulators. The group postulate that withthe insertion of multiple Hyperfinger endoscopes intothe abdomen, complex operations would be possible by ateam of surgeons, reminiscent of traditional open surgery.

However, the viability of such a system remains to beproved. It is likely that as further units are added, along

A B C

Figure 1. (A) da VinciS ( 2005, Intuitive Surgical Inc.: www.intuitivesurgical.com). (B) Active Trocar (University of Tokyo).Reproduced by kind permission of the authors (9) and Springer Science and Business Media. (C) Laprotek (EndoVia:endovia.millersystems.com)

Copyright 2006 John Wiley & Sons, Ltd. Int J Med Robotics Comput Assist Surg 2007; 3: 3–9.DOI: 10.1002/rcs

Robotic Applications in Abdominal Surgery: Limitations and Future 5

Figure 2. Prototype of Hyperfinger (University of Nagoya). Four articulations at the end effectors allow nine degrees of freedom.Reproduced by kind permission of the authors (11)

with the complex control methods to integrate them, therewill be challenges in preventing the equipment becomingexcessively bulky, both in the operating room and insidethe abdomen. The movement available to the device is cur-rently limited to an arc around the first joint of the endo-scope, so for more complex and wider-ranging operations,a device to move it externally (currently manual) will beneeded. Despite these potential problems, the Hyperfin-ger represents a potential improvement on accessibilityand freedom compared to the larger telemanipulators.

Intracorporeal devices

The next evolutionary step in surgical technology will bethe further miniaturization of robotic devices, such thatthey can be completely internalized or ‘intracorporeal’,with limited connections to the outside world. Suchdevices will have the freedom to work at any locationand position within the abdominal cavity. In this respect,developments to date have mainly centred on thedevelopment of intra-abdominal cameras and roboticdevices for imaging of the gastrointestinal tract.

Intra-abdominal cameras

Currently, in both conventional laparoscopic and roboticsystems, the laparoscope is anchored at the abdominalwall and, as such, its movements are limited to anarc around the point where it enters the abdomen. Ithas only four degrees of freedom, which limits whatit can see from each position at which the tip isplaced. Although laparoscopes are available with angledlenses, to change the viewing angle intra-operatively

requires time-consuming camera changes and the needfor multiple scopes at added expense.

Theoretically, a camera mounted on a mobile intra-abdominal device would allow images to be relayed fromany position in the abdomen, and at a large range of view-ing angles. This would give the surgeon unlimited framesof reference. The position and angle of the view could bechanged under the surgeon’s control, and by using currentoffset lens technology a 3-D image would be feasible. Twoor more such devices could be employed simultaneously,which would allow the surgeon to move instantaneouslybetween various fields of view. These capabilities wouldcontribute to the intuitivism of the surgical procedure,making it easier to learn and perform, reducing operativetimes, and minimizing intra-operative complications.

Ideally, the device (or devices) would not need acontinuous port site, so the patient would require oneless working port. Also, a small intra-abdominal devicewould not get in the way of the operating instruments, asis the case with the rigid laparoscope used in laparoscopicand current robotic surgery.

A group at the University of Nebraska have developedtwo prototype intra-abdominal devices. The first is acylindrical camera system mounted on a three-leggedbase, which can rotate 360◦ and change the angle ofthe camera in the vertical plane through 45◦ to providea range of views of the entire abdomen (12). Duringa laparoscopic cholecystectomy on an anaesthetized pig,the device proved useful in providing images of trocarsbeing inserted through the skin and instruments enteringthe abdomen via the ports. These parts of laparoscopicprocedures are often done ‘blind’ with standard equipmentand are a source of potential iatrogenic injury.

The obvious disadvantage of this device is that it is notmobile and its views are thus limited by its position. It willnot be able to get to unique positions within the abdomen,



Figure 3. Mobile in vivo camera (University of Nebraska). Reproduced by kind permission of the authors (13) and Springer Scienceand Business Media

and will be time-consuming and distracting to reposition.The practicality of the device in human laparoscopicsurgery has yet to be demonstrated. Nevertheless, thework showed the potential for intra-abdominal roboticsystems to enhance the safety of minimal access surgery,and the group have gone on to produced a prototypeintra-abdominal robot with mobility (Figure 3) (13).

This device comprises two cylindrical wheels with aspiral tread, and a miniature camera mounted in the axlebetween the wheels. The wheels are specifically designedto move across deformable tissue without damaging it.The device is 20 mm in diameter, 100 mm in length andweighs 50 g. It has a tail to stop the body rotating whenthe wheels move, but can be flipped over when the deviceneeds to reverse its direction. The wheels are poweredby two DC motors, which allows them to be controlledindependently, thus providing a mechanism for turning.The device has been used to assist in a laparoscopiccholecystectomy in a pig, and was indeed the sole sourceof visual feedback during this experimental operation.The surgeon was able to move the device around theabdomen and achieve a range of views and frames ofreference which have previously been unavailable withcurrent standard and robotic laparoscopes. Moreover, itwas shown that the operation could be done via twolaparoscopic ports, rather than the usual four, becauseno extra port was needed for the camera and thedevice could be moved so that the surgeon could seethe relevant structures without the need for an extraretracting instrument.

Although this device was shown to have mobility withinthe abdomen, there are no data regarding its performance.Its speed and agility are unknown, and whether it neededto be moved by the other laparoscopic instruments duringthe procedure is also unknown.

The design of the wheels was based on experimentaldata from two ‘organ models’ (14); flat synthetic foam,and bovine liver tissue. The mechanical properties ofthese models differ greatly from other organs within theabdomen, in particular the small bowel. The surface thatthe small bowel presents is highly deformable, with mobileloops of tissue, very different from the relatively solid andfixed surface of the liver. With no mechanism of adhesionto the tissues, it seems likely that the device would be

liable to fall into the recesses within the abdomen, orbetween bowel loops. Given its size, it is unlikely thatit will be manoeuvrable into small spaces, such as thepelvis, splenic flexure or lesser sac. However, the Nebraskagroup have again made a huge step in the developmentof intracorporeal robotics, and have established the proofof concept for a mobile intra-abdominal device.

The potential applications of anintracorporeal mobile device

The delivery of mobile internal cameras into the abdomenis the simplest of a list of potential applicationsof an intracorporeal device. Many other applicationsthroughout the body are feasible, bringing the potentialfor huge improvements in minimally invasive diagnosticand therapeutic techniques. Several further applications,with specific emphasis on use within the abdomen,are considered below. These applications are dependenton the ability of the device to travel to the targettissue and the capability of the payload the devicecarries. Some of the science and technology behind thesecapabilities is still developing, but it is important thatthese future applications are recognized now, as theyrequire intelligent delivery mechanisms which should bedeveloped in parallel.

Imaging of the gastrointestinal tract

This has long been a difficult and technically demandingarea for clinicians, and has attracted the attention ofengineers and roboticists who have recognized the needfor better equipment to visualize the various parts of thegastrointestinal tract. In so doing, they have added tothe development of intracorporeal robotics and begun thediscovery of adhesive and locomotive mechanisms mostapplicable to the internal body environment.

ColonoscopyImaging of the colon is currently carried out bymanual manipulation of fibre-optic endoscopes, which



is technically demanding and often uncomfortable forpatients. In the UK, approximately 25% of colonoscopiesare reported as incomplete (15) (failure to reach thecaecum) but it is estimated that this figure couldbe up to 40% (15), depending on the definitionused. The consequences for the patient of failing tocomplete the examination include missed diagnoses,further attendances for repeated colonoscopy, and theneed to undergo additional investigation by an alternativemodality.

Colonoscopy is a common investigation, and is likelyto become more so with the imminent introductionof colorectal cancer screening programmes. Therefore,any technical advance which reduces the numberof incomplete tests or improves the diagnostic andtherapeutic capabilities will be of enormous benefit.

Several mechanisms for locomotion of a robotic devicealong the length of the colon have been described,and some prototypes have been demonstrated in animalmodels (16). However, these devices all use adhesionmechanisms which are potentially hazardous to the bowelwall (stretching the diameter of the bowel, physicalclamping to the bowel wall, or using sharp attachment tocling to the mucosa) or rely on using the full circumferenceof the bowel wall to gain purchase for locomotion. Thesemay work relatively safely in normal bowel, but are likelyto be flawed, or carry an unacceptable risk of perforation,in certain disease states where the bowel has becomedilated or thin-walled or the internal surface is veryfriable. Therefore, smaller devices with safer methodsof adhering to the small bowel are required.

Small bowelDirect visualization of the small bowel is made difficultby virtue of its length and tortuousity, and as aconsequence it is not readily amenable to flexibleendoscopy. Conventional imaging of the small bowelhas employed radiological contrast studies, such as smallbowel enemas and computed tomography (CT) scanning.Although these modalities are good at detecting grossintestinal pathology, they lack sensitivity in diagnosingsubtle mucosal abnormalities. In addition, both contraststudies and CT scanning involve exposure of the patientto ionizing radiation.

These problems have been addressed by the introduc-tion to clinical practice of the PillCam (Given ImagingLtd, Israel) (17) (Figure 4). This is a capsule which can beswallowed and will relay images of the entire alimentarycanal as it passes through. Its current limitation is that hasno method for directing or stopping itself, and so lesionsmay be entirely missed or, if seen, cannot be examinedclosely or biopsied.

Current developments are under way at ScuolaSuperiore Sant’Anna in Pisa to modify the device toinclude graspers, which can hold onto the walls of theintestine (18), and future work will be towards addinglegs, so that the device may be manoeuvred within thebowel (19). Virtual and in vitro demonstrations of thislegged device show that it relies on the tension acrossthe diameter of the small bowel lumen in order to gainpurchase. It would therefore be specifically for use inthe small bowel and would not be applicable for use ineither the colon or stomach. The device may also haveproblems in certain disease states, particularly when thebowel is dilated or when the wall is very thin and proneto perforation.

A stopping and locomotion system for the capsuleis also being developed at Carnegie Mellon University,using microfibrillar adhesive pads which mimic the modeof adhesion of beetles (20). Again, this mechanism isreliant on pushing out against the walls of the intestine,and may not be feasible in varying diameters of bowel(the largest diameter in which the prototype was testedwas 1.25 inches, or 3.2 cm) or in situations where thebowel wall is very thin (the mechanism was tested againstrigid walls). However, the group have demonstrated thefeasibility of microfibrillar adhesion to biological tissue,which is a promising development in the evolution ofinternal robotic devices.

Characterization of deep abdominaltissues

Surgeons frequently rely on imaging techniques to makediagnoses and monitor the progress of disease. Thecommon radiological modalities work well in the majorityof cases, but where changes are subtle there can often be

Figure 4. PillCam ( 2001–2006, Given Imaging Ltd, Israel: www.givenimaging.com)



difficulties in interpretation, and closer inspection vialaparoscopy or tissue biopsy may be required.

A good example is imaging of the pancreas. Thisorgan is situated in a retroperitoneal position on theposterior abdominal wall, and therefore is not readilyaccessible. CT and magnetic resonance (MR) imaging ofthe region will identify gross abnormalities in normalpancreatic anatomy, but can be difficult to interpret.There are many conditions which can mimic the CT andMR appearances of pancreatic cancer (21). A biopsy ofthe diseased tissue is required if there is doubt concerningthe radiological diagnosis, as this will frequently guidesubsequent treatment (e.g. chemotherapy).

The ability of an intra-abdominal device to gain accessto restricted intra-abdominal areas, such as the pancreas,would be an enormous advantage in this difficult region.If equipped with an ultrasound probe, it could provide anaccurate target for biopsy, improving diagnostic sensitivityand staging accuracy. If used in the place of a laparoscopeprior to surgical resection, a mobile intra-abdominaldevice armed with an ultrasound probe might providethe surgeon with accurate staging of the disease and, ifrequired, take a biopsy to confirm the diagnosis.

Real-time intra-operative anatomy andhistology

Terahertz pulsed imaging and Fourier transform infraredspectroscopy are emerging technologies in medicalimaging. Their mode of action is similar to that of X-rayand CT, in that they work by passing electromagneticradiation through a specimen and identifying differencesin density of the various tissues by the amount ofradiation emerging at the other side. However, unlikeX-rays, the electromagnetic waves are in or near tothe infrared region (the terahertz region) and thereforeare non-ionizing, and have small wavelengths, allowingfor a hitherto unachievable level of spatial resolution.These techniques have shown tremendous experimentalpotential in delineating different types of tissue (22),and also in distinguishing benign from malignant tissue(23). Furthermore, terahertz probes have already beendeveloped for clinical use in characterizing skin cancers(24). The feasibility of similar benefits within theabdomen has already been demonstrated with in vivotests during open surgery (23).

The impact on minimally invasive surgery is potentiallytremendous. The ability to perform real-time histologicalanalysis of the tissues within the operating field willgo some way to making up for the lack of tactilefeedback consequent of minimal access techniques. Withthe development of an appropriate mechanism to deliverthis technology to operative sites, it can be integrated intorobotic surgical systems to further enhance their accuracyand safety and, as a result, also extend their usability toincreasingly challenging types of procedure.

One useful way in which terahertz technology may beintegrated is as part of an augmented reality (AR) systemfor abdominal surgery. AR techniques have previouslybeen described in laparoscopic surgery (25) (Figure 5) buthave encountered a number of problems. In particular,the structures within the abdomen are soft, mobile anddeformable, and so very often do not comply in positionand shape to the preoperative imaging on which thesuperimposed information is based.

The new imaging techniques based on spectroscopyhave the ability to give real-time feedback and maythus provide a real-time AR display, which remainsaccurate despite the movement and deformation of thetissues during surgery. For this to be realized within theclosed abdomen during a minimally invasive procedure,a reliable, highly manoeuvrable delivery mechanism forthe spectroscopy equipment will be required. A mobileintra-abdominal device may provide such a mechanism.

Delivery of new therapeutic techniques

Photodynamic therapyPhotodynamic therapy (PDT) involves the administrationto the patient of a photosensitizing agent which willspecifically destroy tumour cells when they are exposedto light. This technique has so far been developed forcancers of the skin, head and neck and oral cavity (26),and also those of the oesophagus, bladder, cervix andbronchi (27).

A more difficult challenge is the use of PDT on internalsurfaces. There is early evidence that photosensitizingagents are taken up by peritoneal metastatic nodules,implying that PDT here is feasible, although a clinicalbenefit has not yet been shown (28). It is suggestedthat a more selective photosensitizing agent is required

Figure 5. Augmented reality surgery – superimposition of 3-D reconstructed pre-operative images onto the intra-operative visualdisplay (Institut de Recherche contre les Cancers de l’Appareil Digestif, Strasbourg). Reproduced by kind permission of the authors(24), 2004, IEEE



to improve the results, but also a better light deliverymechanism. A possible solution to the latter may bean internalized robotic mechanism with the ability tomanoeuvre around the abdomen and emit the correctwavelengths from optimal positions in relation to thediseased tissue.

MicrosurgeryWith the rapid progression of nanotechnology anddevelopments in micro-electrical machinery (MEMs),there is a new ability to make nano- and microscalecomponents. This capability has opened up a rangeof possibilities for application in medicine and surgery(29) including surgical procedures in very small spacesand even single-cell surgery. There are a huge numberof possible applications for such technology. Thedevelopment of a mobile intracorporeal device to deliverthe equipment to the relevant site will be essential.

Summary

There have been great advances in technology forabdominal surgery over the last decade, not leastwith the introduction of the da Vinci robotic surgicalsystem. However, limitations have been recognized,and miniaturization of components and systems willbe required if surgical robots are to reach their fullpotential. Work in this direction is progressing and thefeasibility of an intracorporeal robotic device has beendemonstrated. Much further work is required to refinecurrent design concepts for clinical application. Oncethese hurdles have been overcome, it is anticipated thatintracorporeal robotics will herald the next revolution inabdominal surgery.

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