JOURNAL OF ENDOUROLOGYVolume 20, Number 5, May 2006© Mary Ann Liebert, Inc.

Synthetic Torso for Training in and Evaluation of Urologic Laparoscopic Skills

DUMITRU MAZILU, Ph.D., ALEXANDRU PATRICIU, LUCIAN GRUIONU, MARC MCALLISTER,ALBERT ONG, M.D., LARS ELLISON, M.D., DOMINIC FRIMBERGER, M.D., OSCAR FUGITA, M.D.,

LOUIS KAVOUSSI, M.D., and DAN STOIANOVICI, Ph.D.

ABSTRACT

Background: The expanding use of advanced minimally invasive surgical techniques demands more advancedtraining methods, objective measures of resident performance, and more realistic and anatomically correcttraining models.

Materials and Methods: A new synthetic torso for urologic laparoscopy training was developed and assessed.The trainer, Lapman, was based on the Visible Human Model and has the exact shape of a human torso. Thetorso models the outer shape of the body and the abdominal and pulmonary cavities. Animal or syntheticmodels of the abdominal organs may be placed in the abdominal cavity. An abdominal wall provides accessand seals the cavity and can be replaced after repeated punctures with laparoscopic instruments. The tho-racic cavity connects to a pneumatic pump to simulate breathing. In order to render realistic mechanic prop-erties, the torso is cast of materials with elastic properties similar to those of soft tissue and incorporates asynthetic skeleton. These similar mechanical properties and the thoracic insufflation create realistic ventila-tory motion simulation.

Results: Twenty-five individuals—medical students, residents, and attending urologists—participated in astudy comparing Lapman with a standard training box. Lapman presented several advantages over the tra-ditional training box, specifically with regard to internal and external views and the incorporation of a real-istically shaped abdominal wall. A significant and recurrent theme was the value of the synthetic wall as atool to gain a greater appreciation of the importance of port placement. Study participants at all levels oftraining appreciated that Lapman gives a more realistic approximation of the operative procedure.

Conclusions: The novelty of the trainer consists in its anatomic shape, realistic mechanical properties, andventilatory simulation. This paper reports on its design, construction, and preliminary tests.

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INTRODUCTION

IN CONTRAST TO OPEN SURGICAL TECHNIQUES, lap-aroscopic surgery typically results in shorter hospitalization

and reduced patient morbidity, lower analgesic dosages for paincontrol, and faster recovery.1–5 However, laparoscopic surgeryrequires significant surgeon training. The complexity of urologicapplications and the low relative incidence of appropriate casesmake it essential for the urologist to have access to training mod-els.6–8 In an attempt to provide training, numerous urologic lap-aroscopy programs and short courses have been established.9–11

For most urologists, the short course is the only opportunityto acquire the skills necessary to initiate a laparoscopic prac-

tice. The difficulty for these individuals is translation of skillspracticed in the laboratory to use at the operative table. Tradi-tional laparoscopic trainers have focused on simple discretetasks in an environment devoid of anatomic challenges. Al-though there is a role for such training, the importance of work-ing within the abdominal cavity cannot be understated.

Similarly, residency programs are challenged to guide thedevelopment of these skills among their trainees.12 Accredita-tion boards will soon require objective assessment of surgicalperformance.13 The use of trainers and recording performanceis one possible pathway to achieve this goal.

We developed Lapman to address deficiencies identified instandard laparoscopic trainers. Using the Visible Human Proj-

URobotics Laboratory, Brady Urological Institute, Johns Hopkins Medicine, Baltimore, Maryland.

SYNTHETIC TORSO FOR TRAINING 341

FIG. 1. Development of model. (A) Slice from Visual Human. (B) Three-dimensional reconstruction in ProEngineer.

*For more information on the work of the laboratory, visithttp://urology.jhu.edu/urorobotics

FIG. 2. Development of model (continued). (A) Fabrication of mold by CNC machining. (B) Components for torso and ab-dominal wall.

ect14 of the National Library of Medicine, an exact syntheticreplica of the human torso, including the thorax and abdominalcavity was created. Once it was manufactured, we conducted apreliminary randomized study to assess physician and medicalstudent perceptions of this new device.*

MATERIALS AND METHODS

Trainer design, development, and description

Lapman was developed to mimic the anatomic and mechan-ical properties of the human torso and to provide means of in-corporating synthetic or animal organs in situs for performingrealistic surgical maneuvers.

The simulator is based on the three-dimensional (3D) modelof a typical man created from segmented and reconstructed data

available through the Visible Human Project14 of the NationalLibrary of Medicine. Transverse slices (Fig. 1) at an averageof 5-mm intervals (from section no. 4155 at sagittal-coronal co-ordinate z � 463 voxel � 154 mm to section no. 2048 at z �3190 voxel � 1063 mm) were obtained. This set spans the en-tire torso, including the thoracic, abdominal, and pelvic regions.

A manual segmentation method was used to define the outerbody and pulmonary and abdominal cavities in these imageslices (Fig. 1A). The volume created for the abdominal cavityincludes all the peritoneal and retroperitoneal organs. A newaspect in creating the 3D model (Fig. 1B) was its constructionusing engineering design software, Pro/Engineer (PTC, Inc.),which was selected for manufacturing purposes. The model wasused to design and fabricate negative molds for casting thetrainer (Fig. 2). These were digitally manufactured of wood-blocks using computer numerically controlled (CNC) equip-ment (Fig. 2A) in our laboratory.

The torso was cast of Cine Skin Silicone A/B from BurmanIndustries Inc. (Van Nuys, CA). This material was selected bytesting a number of skin-like materials (Moulage and Mold La-

A

A

B

B

tex material from Dick Art Materials Inc. [Galesburg, IL], Du-ralco from Cotronics Corporation [Brooklyn, NY], and Latexmold and mask materials from Douglas & Sturgess [San Fran-cisco, CA]) with respect to the ease of the molding process, re-sulting mechanical properties, ability to vary these propertiesby changing the mixing components ratios, and by color anddye pigments available for proper color settings. The elasticproperties of the selected material also allow for ventilatory-motion simulation. Because kidney position and other abdom-inal organs fluctuate with breathing, this was an important fac-tor in designing and creating the model.

In order to provide realistic support and structure for the bodyand ventilatory motion, a synthetic skeleton was placed insidethe molds prior to casting of the torso (Fig. 3). The lungs wereinitially cast of a low melting-temperature wax in a differentmold. These were incorporated in situs before molding of thetorso. After curing of the rubber compound, the wax was ex-tracted by melting, to leave behind the cavities of the lungs.

The disposable abdominal wall was cast in a separate mold(Fig. 2B). It presents a two-layer structure of rubbers with dif-ferent consistencies. The wall is attached to the body using a

hook and loop fastener on its boundary and is hermeticallysealed over the base with an elastic rim (Fig. 4A). This allowsabdominal insufflation, as can be seen in Figure 4B.

Six connection hoses were included next to the spine fromthe left and right retroperitoneal fossas and out through the neck.These may be used to simulate blood and urine flow to animalorgans placed within the torso.

Evaluation methods

We compared the self-evaluation and trainer scores of agroup of subjects with either a standard box simulator or theanatomically correct simulator, Lapman (Fig. 5). Twenty-fivemedical students, residents, and attending urologists were en-rolled in the study. A 15-minute instructional presentation givenby an endourology fellow provided a basic overview of lapa-roscopic surgery and described and demonstrated the tasks tobe practiced. The participants were then randomized and al-lowed to work for 2 hours, during which the fellow was pres-ent to provide assistance.

In the case of the laparoscopic training box case (Fig. 5A), a10-mm port (U.S. Surgical Corp.) was placed in the middle forcamera access. Ports of 5 mm and 10 mm (USSC) were placedfor instrument access. A large plastic Petri dish was used to sup-port and immobilize a porcine kidney within the box. With theLapman (Fig. 5B), a 10-mm port was placed at the umbilicus forcamera access. A second 10-mm trocar 4 cm lateral to the um-bilicus at the midaxillary line and a 5-mm port 4 cm superior tothe umbilicus were placed for instrument access. A porcine kid-ney was placed in the abdominal cavity in the left retroperitonealfossa. The same type standard video cart was utilized for both sim-ulators, and 10-mm 30° laparoscopes were connected to the cam-era and a light source (Stryker Instruments, Santa Barbara, CA).The laparoscope and camera were held and manipulated in bothcases by another participant. The following tasks were performed:trocar placement, instrument selection and manipulation, needleand suture manipulation, suturing, and intracorporeal knot-tying.

After each session, the participants were asked to completea questionnaire identifying the training model, the exercises per-formed, and the instructor. It also queried the level of educa-tion and surgical experience of the subject. The subjects ranked

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FIG. 3. Synthetic skeleton placed within molds.

FIG. 4. Completed torso open (A) and with insufflated abdominal cavity (B).

A B

their responses on a Likert 5 point scale, from “poor” to “ex-cellent” and from “strongly disagree” to “strongly agree.” Par-ticipants also had the opportunity to provide written comments,suggestions, and critiques.

The questionnaires were then converted to an analog scaleby assigning “strongly disagree” and “poor” a value of 1 and“strongly agree” and “excellent” a value of 5. The results werestratified by the simulator used. A mean and standard deviationwere then calculated for each question. The means were com-pared and p values calculated using Student’s standard t-test.All statistical computations were performed using STATA. Thelevel for statistical significance was 0.05.

RESULTS

Table 1 summarizes the statistical results for the questionsasked in the survey. Users found Lapman significantly easier

to use and a better approximation of real anatomy with a bet-ter internal view (p � 0.008, �0.001, and �0.001, respec-tively). The respondents felt that it was a better design (p �0.002). Moreover, students in both groups agreed or stronglyagreed that approximating real anatomy was important and thatport placement was important for training (p � 0.064 and 0.500,respectively).

DISCUSSION

Training programs use a sequence of theoretical, simulator,and animal training followed by mentored surgery, whereasshort courses address only the first three of these steps. Lapa-roscopy simulators can be classified as either physical devicesor virtual reality (VR) simulators.

Traditional training devices present box architecture withflexible trocar entry ports.15 These trainers are designed for gen-

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TABLE 1. SUMMARY STATISTICS OF SURVEY RESULTS (MEAN [SD])

Box simulator Lapman simulatorMean (SD) Mean (SD) P value

Trainer evaluationEase of use 2.9 (0.73) 4.0 (0.95) 0.008Approximation of 1.8 (1.1) 4.1 (0.57) �0.001

anatomyInternal view 2.7 (1.3 4.3 (0.65) �0.001Overall 2.9 (1.3) 4.3 (0.49) 0.002

Trainer designImportance of anatomy 4.0 (1.1) 4.7 (0.49) 0.064External appearance 3.1 (1.3) 3.8 (1.0) 0.150Trainer port placement 2.9 (1.1) 4.2 (0.72) 0.500

Skills labInstrument training 3.6 (0.97) 4.1 (0.90) 0.239Port placement training 3.1 (1.3) 4.0 (0.77) 0.069Suturing 3.7 (1.1) 4.1 (0.66) 0.314Knot tying 3.5 (1.3) 4.1 (0.79) 0.203

Instructor evaluationIntroduction 4.5 (0.70) 4.3 (0.77) 0.608Definition of goals 4.1 (1.1) 4.3 (0.86) 0.724Technique description 3.8 (1.4) 4.2 (0.83) 0.455Assistance 3.8 (1.3) 4.6 (0.67) 0.198

FIG. 5. Testing set-up on box (A) and Lapman simulators (B).

BA

eral laparoscopy training in the initial phases for acquiringthrough-the-hole, inverted manipulation skills, depth perceptionunder monitor vision, and hand–eye coordination but fail to givea realistic anatomic perspective. For example, Mughal16 devel-oped a box trainer designed for basic inverted-motion laparos-copy training. Munro and associates17 and Kopchok et al18 re-ported more realistic box trainers that allow trocar placementand abdominal insufflation. Seattle’s Simulab Corporation,19

along with the University of Washington Center for Videoen-doscopic Surgery, devised a simulator with the purpose of re-placing live-animal training. This simulator consists of a syn-thetic body model and procedure-specific packs and allowstrainees to introduce surgical instruments and practice laparos-copy skills on simulated latex organs with standard instrumentsand laparoscopes.

Recently, several VR surgical simulators have become avail-able.20,21 These trainers use a computer-modeled human bodyand laparoscopic-like input devices (haptic interface) throughwhich the trainee interacts with the model to perform specificsurgical procedures. For example, MIST-VR,20,22 a laparo-scopic trainer developed by Virtual Presence, allows the simu-lation of several laparoscopic procedures. Even though VR sim-ulators are potentially the ideal training solution, providing acost-effective and convenient setting, their application and util-ity are at present limited by the high complexity of realisticallymodeling human organs.21,23

The next training step, using live animals, is realistic withrespect to tissue properties, but the use of animals is limited bycost. In addition, animals present different anatomy for portplacement and dissection.

We report the development of a new laparoscopic trainer,Lapman, designed for laparoscopy on the upper urinary tractpresenting exact human anatomy and mechanical propertiessimilar to those of the human body. The simulator is intendedto provide an additional training step, together with box simu-lators, live animal training, and mentored surgery, with the goalof improving the learning curve. In addition, Lapman could re-duce or even eliminate the need for animal training. Lapmanincorporates several characteristics of previous designs andadds other innovative features in a urologic laparoscopy trainer.Even though the development cost of the initial prototype wasmuch higher, we believe that a commercial version of the Lap-man simulator would not be significantly more expensive thanclassic box-type simulators.

The trainee participates in numerous steps, beginning withinserting the Veress needle, insufflating with CO2, determiningthe port sites, and placing the trocars. The trainee can then per-form a variety of laparoscopic procedures in an anatomicallyconsistent setting. The simulator allows the student to dissectand develop tissue planes, excise and reconstruct tissue, andlearn suturing and electrocautery techniques. Moreover, thesimulator is designed for the placement of an animal kidney inthe retroperitoneum so that the trainee operates on realistic tis-sues, thus simulating various procedures such as renal biopsy,pyeloplasty, nephrectomy, and even partial nephrectomy.

The majority of participants in this study were medical stu-dents. It is not surprising that they would not identify port place-ment as a significant value of this model, as this is a relativelysubtle skills that is developed as an individual’s laparoscopicexperience expands. The experienced laparoscopists in this pi-

lot study uniformly described this as a clear attribute of the syn-thetic torso. In order to measure the value of this particular aspect of the model adequately, one would need to evaluate lon-gitudinal performance among a groups of individuals early intheir training who were randomized to black box versus syn-thetic torso for laboratory training.

There were many limitations to the study performed. Therewas no objective evaluation of the participants, nor do we knowif self-reported evaluations will translate to better surgical per-formance. The goal of the study was to collect the subjectiveimpressions of how simulator design impacts training and toassess our Lapman design. A prospective study will be neededin order to assess objectively how the schedule impacts train-ing: specifically, what is the most effective length of a trainingsession and how many sessions are most effective. Future stud-ies could also evaluate the ability of these training programs todecrease errors in the operating room, as well as what addi-tional skills can be taught effectively through standardized lec-tures or video presentations.

CONCLUSION

The current paper presents a new laparoscopic simulator de-signed for urologic interventions. The natural human body con-figuration allowed the trainee to experience the correct spatialrepresentation and distribution of trocars that are normallyfound in the human abdomen during laparoscopic surgery. Themixed synthetic/animal model with induced ventilatory motionof the organs rendered a most realistic model compared withexisting box simulators. Lapman was tested in a limited com-parative study and showed subjective superiority over the tra-ditional box trainer.

ACKNOWLEDGMENT

The research presented in this paper was supported in partby grant No. PHD0103 from the American Foundation of Uro-logic Disease (AFUD). The contents of this paper are solely theresponsibility of the authors and do not necessarily representthe official views of the AFUD.

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Address reprint requests to:Dan Stoianovici, Ph.D.

URobotics DO115Brady Urological Institute

5200 Eastern Ave.Baltimore, MD 21224

E-mail: dss@jhu.edu

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