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A Triangulating Operating Platform EnhancesBimanual Performance and Reduces SurgicalWorkload in Single-Incision LaparoscopyErwin Rieder, MD, Danny V Martinec, BS, Maria A Cassera, BS, Trudie A Goers, MD,

hristy M Dunst, MD, FACS, Lee L Swanstrom, MD, FACS

BACKGROUND: Single-site laparoscopy (SSL) attempts to further reduce the surgical impact of minimallyinvasive surgery. However, crossed instruments and the proximity of the endoscope to theoperating instruments placed through one single site leads to inevitable instrument or trocarcollision. We hypothesized that a novel, single-port, triangulating surgical platform (SPSP)might enhance performance by improving bimanual coordination and decreasing the surgeon’smental workload.

STUDY DESIGN: Fourteen participants, proficient in basic laparoscopic skills, were tested on their ability toperform a validated intracorporeal suturing task by either an SSL approach with crossed artic-ulated instruments or a novel SPSP, providing true-right and true-left manipulation. Standardlaparoscopic (SL) access served as control. Sutures were evaluated using validated scoring meth-ods and the National Aeronautics and Space Administration Task Load Index was used to ratemental workload.

RESULTS: All participants proficiently performed intracorporeal knots by SL (mean score 99.0; 95% CI97.0 to 100.9). Performance decreased significantly (more than 50%, p � 0.001) with the SSLapproach using 1 rigid and 1 articulating instrument in a cross-wise manner (mean score 39.2;95% CI 28.3 to 50.1). The use of the SPSP significantly enhanced bimanual coordination(mean score 67.6; 95% CI 61.3 to 73.9; p � 0.001). Participants recorded lower mentalworkload when using true-right and true-left manipulation.

CONCLUSIONS: This study objectively assessed SSL performance and current attempts for instrumentation improve-ment in single-site access. While SSL significantly impairs basic laparoscopic skills, surgical platformsproviding true-left and true-right maneuvering of instruments appear to be more intuitive andaddress some of the current challenges of SSL that may otherwise limit its widespread acceptance.

(J Am Coll Surg 2011;212:378–384. © 2011 by the American College of Surgeons)

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Single-site laparoscopy (SSL) is a recently evolving devel-opment in minimally invasive surgery that proposes to fur-ther reduce the surgical impact of standard laparoscopy(SL) by decreasing the number of trocars and abdominalwall incisions. Most reports of SSL have described the um-bilicus as an ideal location for access into the abdominalcavity. Early results already have demonstrated the success-

Disclosure Information: TransEnterix, provided the SPIDER surgical sys-tem and SPIDER flexible instruments. Stryker Endoscopy, provided the5-mm bariatric endoscope. These companies were not involved in studydesign or data acquisition and interpretation.

Received August 3, 2010; Revised October 6, 2010; Accepted October 12,2010.From the Minimally Invasive Surgery Program, Legacy Health, Portland, OR.Correspondence address: Erwin Rieder, MD, Minimally Invasive Surgery

nd

tProgram, Legacy Health, 1040 NW 22 Ave, Suite 560, Portland, OR97210. email: erwin.rieder@meduniwien.ac.at

378© 2011 by the American College of SurgeonsPublished by Elsevier Inc.

ful use of multiple trocars through 1 umbilical incision orspecific single-port devices for cholecystectomies and evenmore advanced procedures such as colectomies.1-3 Thisoncept, of multiple laparoscopic instruments togetherith the endoscope through 1 access point, has some severehysical and ergonomic constraints that make it more dif-icult to learn and perform than traditional laparoscopicurgery. The proximity and parallel trajectory of the endo-cope and operating instruments placed through a singleite leads to inevitable instrument or trocar collision, whichnterferes with smooth movements in the majority of casesnd makes the procedure more demanding than standardaparoscopy.

Articulating laparoscopic instruments, developed toake SL easier, have been subsequently adopted for SSL in

n effort to correct the difficulties inherent in the loss of

riangulation resulting from a single-site approach. The

ISSN 1072-7515/11/$36.00doi:10.1016/j.jamcollsurg.2010.10.009

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379Vol. 212, No. 3, March 2011 Rieder et al Single-Port Platform Enhances Performance

additional maneuver of using a cross-wise approach of thearticulating instruments such as graspers or scissors makesit possible to overcome, to some degree, the inherent diffi-culties in traction/counter-traction issues. However, work-ing with crossed instruments side-inverts any movementdisplayed on the monitor and makes SSL potentially morementally demanding than standard multiport laparos-copy.4 A potential solution to this problem is the use of ariangulating operating platform with a single shaft (foringle-site access) but multiple triangulating end-effectorso replicate the angles of approach of SL.5 With the help of

flexible arms/channels with adjustable angle, an addi-ional rigid channel for triangulation, and 1 channel for thendoscope, instruments are maneuvered at the surgical siteith true-right and true-left manipulation. SSL is similar

o standard laparoscopy only hampered due to the coaxialccess and consecutive interfering of instrument move-ents, a surgical platform represents a completely dif-

erent and new approach for the minimally invasive sur-eon. It was hypothesized that a novel laparoscopiclatform enabling single-site access has substantial ben-fits compared with standard SSL, in which instrumentsave to be used in a cross-wise manner. A valid educa-ional tool with reliable metrics was chosen as the lapa-oscopic drill.6 Because 7 degrees of freedom provided

by each instrument of the single-port platform might beinitially overwhelming for some, the mental workload ofparticipants after each task was evaluated by a well-established and validated test.

METHODSParticipantsAll tests were conducted at the Division of Minimally In-vasive Surgery, Legacy Health, Portland, OR, and volun-teering participants (pre-med students, surgical residents,fellows, and attending physicians) experienced in conven-tional laparoscopy were tested on an advanced laparoscopicdrill using 3 different approaches. All tasks were conductedin a Fundamentals of Laparoscopic Surgery (FLS) laparo-scopic trainer box with a modified polyvinyl chloridemembrane to replicate a single-site approach. To simulate

Abbreviations and Acronyms

FLS � Fundamentals of Laparoscopic SurgeryNASA-TLX � National Aeronautics and Space

Administration Task Load IndexSL � standard laparoscopySPSP � single-port triangulating surgical platformSSL � single-site laparoscopy

the influence of endoscope maneuvering, especially in SSL,

a rigid endoscope (0 degrees, 5-mm, bariatric length,Stryker Endoscopy) driven by an experienced assistant wasused for visualization instead of a built-in camera used instandard FLS tasks. A pretest questionnaire was given to allparticipants to obtain demographic data and level of train-ing, and laparoscopic or SSL experience.

The endoscope was connected to a processor (888digital camera, Stryker Endoscopy) and illuminated by alight source (X6000, Stryker Endoscopy). The task wasdisplayed on a 19-inch surgical monitor (Sony PVM-1953MD).

Task: intracorporeal suturingAdvanced bimanual coordination was tested by an intra-corporeal suturing task, conducted similar to the FLS cri-teria, which requires participants to place a suture of stan-dardized length (15 cm length, size 0, SH needle, EthibondExcel, Ethicon) precisely through 2 marks on a standard-ized Penrose drain (3.0 cm) with an oval slit along its longaxis (1.0 cm). The Penrose drain was attached onto a stan-dard FLS suture block by Velcro strips and participantswere instructed to tie a knot using an intracorporeal tech-nique.7 Three throws were required including 1 doublehrow and 2 single throws. Timing started when the needlelaced in front of the Penrose drain was grasped and itnded when the sutures were cut with scissors. Knots wereupposed to be square, be accurate through marks, andhould not slip or come apart. Time as well as quality wasvaluated and penalties were given according to FLS crite-ia by an experienced proctor. Performance score was cal-ulated according to FLS criteria and compared withinroups. A previously defined level of proficiency requireserforming accurate intracorporeal sutures within 112 sec-nds, resulting in a score of 93.7.8 After detailed explana-

tion and demonstration of the task, participants had theopportunity to practice and make themselves familiar withthe different approaches for a maximum of 15 minutesbefore each evaluation. The order of the approach was ran-domly allocated to avoid any intergroup learning effectsand 3 attempts in a row were performed with each ap-proach. A maximum time limit of 10 minutes per attemptwas set.

Instruments for the laparoscopic approachApproach 1 (control group)Two standard needle drivers (Jarit Instruments) inserted viatwo 12-mm trocars inserted at a convenient distance wereused for conventional laparoscopic (SL) intracorporeal su-turing. The laparoscope was placed centered in a typical

triangular fashion (Figs. 1A and B).

380 Rieder et al Single-Port Platform Enhances Performance J Am Coll Surg

Instruments for the single-site approachApproach 2To closely mimic single-incision surgery in an experimentalsetting, three 5-mm low profile trocars were placed in atriangle with a maximum of 5 mm distance in between.One rigid (Jarit Instruments) and 1 articulating/lockableneedle holder (Cambridge Endo) were used in a cross-wisemanner. The laparoscope, driven by an assistant experi-enced with SSL, was inserted in the lower trocar (Figs. 1Cand D).

Approach 3A novel single-port, multichannel surgical platform (SPSP;Spider Surgical Platform, TransEnterix) was table mountedand adjusted for use in the trainer box (Figs. 1E and F).This platform is a single-port access device to facilitatemulti-instrument maneuvering through a single incision.The SPSP has 2 flexible working channels where instru-ments can be delivered to the operative field. These chan-nels are guided by a gimbal system at the proximal end andenable 7 degrees of freedom at the distal tips. Flexible in-struments can be inserted and movements of the operatorare accurately transferred to the tip of the channel and tothe instrument. Thereby, standard laparoscopic maneuver-

Figure 1. A–F. Different approaches for intracorporeal suturing.laparoscopy; E, single-port triangulating surgical platform) and ilaparoscopy; F, single-port triangulating surgical platform).

ing is supposed to be simulated, as the right hand controls

the right instruments and the left hand controls the leftinstrument seen on the monitor. Two additional rigidchannels accommodate the endoscope and a rigid instru-ment for additional traction/countertraction if needed. Be-cause the endoscope is mounted within the rigid channel,tasks were performed without an assistant. For the suturingtask, 2 flexible needle drivers were used (SPIDER needledriver, TransEnterix).

Mental workloadAfter the 3 suture attempts within each approach, partici-pants had to self-evaluate their stress level associated withthe task, unobserved in a separate room, using the comput-erized National Aeronautics and Space AdministrationTask Load Index (NASA-TLX). The NASA-TLX requiresratings regarding mental demand, physical demand, tem-poral demand, effort, performance, and frustration, and itspsychometric properties are well established.9

StatisticsA sample size of 11 participants was calculated to be suffi-cient to detect the observed performance difference be-tween the 2 single-site suturing techniques using a paired

nal view of the surgeon (A, standard laparoscopy; C, single-siteal view of instruments (B, standard laparoscopy; D, single-site

Externtern

t-test analysis with alpha � 0.05 and a power of 0.8. Our

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381Vol. 212, No. 3, March 2011 Rieder et al Single-Port Platform Enhances Performance

study, which used 14 participants, should provide a confi-dent level of power to test the primary hypothesis as well asthe differences in mental workload. To assess the normalityin the distribution of the data, the Kolmogorov–Smirnovtest was used. Statistical analysis was performed usingwithin-subjects ANOVA, paired t-test, Wilcoxon signedrank test or Pearson’s coefficient of correlation, as appro-priate. SPSS 17.0 (SPSS, Inc) statistical software was usedfor analysis. All values are shown as mean and 95% CI. Pvalues less than 0.05 were considered significant.

RESULTSParticipants (4 women, 10 men) had a median age of 40years (range 25 to 55 years) and represented a group ofattending surgeons (n � 7; 50%), fellows (n � 4; 28.6%),1 PGY4 resident (7.1%), and 2 pre-med students (14.3%).Seven participants (50%) had more than 10 years of expe-rience in laparoscopy and an additional 5 had between 2and 6 years of training in minimally invasive surgery. The 2participating students had gained laparoscopic knowledgein animal laboratories or trainer-box settings for more than2 years and both were able to pass the standard FLS curric-ulum. Seven laparoscopists (50 %) did not have previousexperience with performing SSL procedures, in either theclinical or experimental settings. Four surgical attendingshad previous SSL experience of more than 15 cases(28.6%) and 3 surgical fellows (21.4%) had performed lessthan 10 SSL cases.

Intracorporeal suture performanceAll participants were able to sufficiently perform an intra-corporeal knot in the FLS box using 2 rigid needle driversby a conventional laparoscopic approach (mean score 99.0;95% CI 97.0 to 100.9). Performance decreased more than50% (p � 0.001) on the attempt to suture via the SSLpproach using 1 rigid and 1 articulating instrument in aross-wise manner (mean score 39.2; 95% CI 28.3 to0.1). Three participants (21%) were not able to performn intracorporeal suture within the 3 attempts and theaximum time limit. The use of the SPSP significantly

nhanced bimanual coordination (mean score 67.6; 95%I 61.3 to 73.9; p � 0.001). All participants (100%)

scored better with the surgical platform compared withcrossed instruments via the SSL approach.

It was observed that years of experience in minimallyinvasive surgery were significantly correlated to standardlaparoscopic suture performance (r � 0.404; p � 0.008),ut were negatively correlated to the score achieved withhe SSL (r � �0.388; p � 0.011). Surgical attendingscored significantly worse in the SSL approach (mean score

5.0; 95% CI 10.0 to 40.0) than the group of surgical fellows,

esidents, or students (mean score 50.4; 95% CI 38.6 to 62.2;� 0.008). Previous experience in single-incision surgery wasot related to SSL scores. Performance with the surgical plat-orm was also not correlated to previous laparoscopic experi-nce. Results are displayed in Figure 2.

Mental workloadCompared with conventional laparoscopy (mean 25.7;95% CI 20.5 to 30.8) all participants (14 of 14) indicateda significantly higher mental workload, observed byNASA-TLX score after the attempt to perform intracorpo-real sutures by SSL with crossed instruments (mean 74.9;95% CI 65.8 to 84.1). The intraindividual difference be-tween SL and SSL ranged from �16.0 to �78.0 in theNASA-TLX score. After using the SPSP approach (mean62.4; 95% CI 54.1 to 70.7), all participants (14 of 14) alsoscored higher in their subjective workload compared withSL (range: �9.0 to �53.7), but significantly lower com-pared with their subjective score after SSL (p � 0.003).

Figure 2. Diagram displays the mean performance score and 95%CI of 14 participants for the intracorporeal suturing task. Dotted lineindicates the proficiency level (93.7) according to Fundamentals ofLaparoscopic Surgery criteria. LAP, laparoscopy; SSL, single-sitelaparoscopy; SPSP, single-port triangulating surgical platform.

Eighty-six percent (12 of 14) indicated lower demands af-

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382 Rieder et al Single-Port Platform Enhances Performance J Am Coll Surg

ter the SPSP approach (range �2.7 to �31.7). The 2 othersurgeons found the surgical platform similar or slightlymore demanding than SSL (�0.7 and �5.0). Taking thesubjective NASA-TLX score after SL as an individual base-score, participants indicated a significantly higher net in-crease in workload after SSL compared with the increase inworkload after using the SPSP (p � 0.004). Figure 3 dem-onstrates the NASA-TLX scores of all participants andapproaches.

DISCUSSIONNot long after the introduction of laparoscopic surgery,several reports demonstrated an interest in performing evenless invasive surgery by reducing the number of trocarsused.10,11 Perhaps as a logical consequence, Navarra and col-eagues12 reported on a series of 1-wound laparoscopic chole-cystecomies in 1995.12 The authors described placement of 2rocars through 1 skin incision at the umbilicus. Dissection ofhalot=s triangle was enabled with 3 additional transabdom-

nal sutures used for traction and countertraction. Similarechniques have recently gained popularity among mini-ally invasive surgeons and are known by multiple acro-

yms such as: single-incision-laparoscopic-surgery (SILS),aparoendoscopic single site (LESS), or single-port surgery.

Figure 3. Diagram displays the National Aeronscores (y-axis) of 14 participants after the attestandard laparoscopy (●), the single-site laparoplatform ( ) approach, arranged in order of exfellows; 4 to 7; attendings: 8 to 14).

rticulating instruments, with different degrees of free- b

om, as well as several additional tools and techniques haveeen adopted or developed to facilitate triangulation, oth-rwise strongly hindered in SSL. Inspite of articulating in-truments, several tricks of instrument maneuvering haveo be learned to enable laparoscopy via 1 small skin incisionr a single port, and adequate tissue exposure is achievednly when laparoscopic tools are arranged in a cross-wiseanner with a resulting limited range of motion. It is cer-

ain that bimanual coordination, defined as the synergisticovement of 2 different instruments, as well as smooth-

ess of movements are strongly hampered in SSL. Typi-ally, in clinical application, using 1 articulating and 1 rigidnstrument is adequate to give enough working space to

anipulate and dissect tissue bimanually and make therocedure less mentally demanding. However, the lack ofrgonomics is still a significant drawback of SSL, whichesults in higher mental workload, surgeon fatigue, andotentially higher operative errors.Several tasks based on the McGill Inanimate System for

raining and Evaluation of Laparoscopic Skills programMISTELS) were developed and introduced by the Societyf American Gastrointestinal Endoscopic SurgeonsSAGES) to teach and measure basic skills. These werencorporated into the FLS program curriculum and have

s and Space Administration Task Load Indexto perform an intracorporeal suture using the

y (�), and the single-port triangulating surgicalnce (pre-med students: 1 and 2; resident: 3;

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een extensively validated.13 This program is generally ac-

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383Vol. 212, No. 3, March 2011 Rieder et al Single-Port Platform Enhances Performance

cepted to document basic competence in minimally inva-sive surgery, and simulator scores are strongly predictive ofintraoperative laparoscopic performance.14 Intracorporealsuturing is probably the most advanced (difficult) taskwithin this training curriculum. Several skills includingeye-hand and bimanual coordination are represented bythe suturing task, but limited degrees of motion make itdifficult to perform in SSL. However, the ability to performan intracorporeal knot belongs to the basic competency foradvanced minimally invasive surgery and was thereforeused as the primary performance metric for this study. Itwas hypothesized that performance is initially hampered byan SSL approach, even with an articulating instrument, butmight be improved by using a novel surgical platform thatoffers true-right and true-left manipulation and triangula-tion via a single port. For this experimental setting it wasimportant to use a laparoscope, driven by an assistant, in-stead of a mounted camera used for visualization in thestandard FLS trainer box. In single-port surgery it is wellknown that the rigid endoscope strongly interferes withinstrument movements and any data acquired without anactive camera-person might highly underestimate the dif-ference between SSL and SL. No assistant was used for theSPSP because the visualization system is mounted in one ofthe rigid channels.

Although all participants were sufficiently experiencedin basic laparoscopic techniques and had reached a previ-ously defined level of competence as defined by passing theFLS examination,8 average performance was significantlydecreased with crossed instruments and the SSL approach.The mean score reached only 40% of that achieved withconventional laparoscopy. Despite using a sophisticated ar-ticulating needle driver, enabling even small adjustments ofthe tip by 2 additional degrees of freedom, several partici-pants were initially not or only barely able to perform in-tracorporeal knots with SSL instruments in the maximumgiven time of 10 minutes. The subjective mental workload ofparticipants as measured with a validated measurement tool,was observed to be an average of 3 times higher when com-pared with the standard approach. Clinically, this might resultin a higher number of errors when performing SSL, at least inthe learning phase, similar to what was observed in the earlyphase of laparoscopic cholecystectomy.15 Interestingly, it wasbserved that surgical attendings scored significantly worseith the SSL approach than the group of surgical fellows,

esidents, or students. It can be hypothesized that years ofaparoscopic experience might lead to certain automatismsnd muscle memories in bimanual coordination, whichannot be easily transferred to the SSL approach. Suchutomatism might initially interfere with the required “in-

erted” ambidexterity in SSL and thereby further decrease

erformance when using crossed instruments. These mus-le memories may not have been locked into participantsith less experience, such as surgical residents or fellows.dditionally, motivation to dedicate oneself to a novel,ore tedious surgical technique might decrease with years

f practicing.The lower scores with SSL noted in this study are also

onsistent with intraoperative data reported in initial SSLrials, in which operative times have been observed to beonger than with the SL approach.16,17 A recent studysing a similar setting already could demonstrate thatven among experienced surgeons, the SSL approach ledo inferior performance.18 The authors have also statedhe need for appropriate training and further instrumentevelopment.An important step further appears to be a single-port

latform, such as was used within this study; the meanuture performance score was observed to be significantlyetter compared with SSL. On average, nearly 70% of aonventional suture performance score was reached evenithin the first 3 attempts. Furthermore, mental workloadeasured by the standardized NASA-TLX score was found

o be lower in 86% of participants compared with SSL. Itas been previously stated that mental workload measureshould be incorporated in the evaluation of new laparo-copic devices or procedures,9 because cognitive overloadas been recognized as a significant cause of surgical error.e used a metric developed for NASA pilots and astro-

auts to measure this; this had been previously validated inurgical applications.19

The NASA-TLX is a multidimensional rating procedurethat provides an overall workload score based on a weightedaverage of ratings on 6 subscales: mental demands, physicaldemands, temporal demands, own performance, effort,and frustration. Using the computerized version the lowestpossible score is 5; the highest ranking leads to an overallscore of 100. Due to the subjective manner of the test, adistinct threshold between a low and a high score cannot beeasily drawn. However, the use of a reference or basic score,such as the workload indicated for a standard procedure(eg, SL), allows efficient identification of an increase ordecrease in required mental workload. Although a novelsurgical platform, which displays a completely new surgicalapproach and 7 degrees of freedom, might be initially over-whelming, it appears that crossed instruments and manda-tory ambidexterity seem to be even more challenging. Thetrue right and true left manipulation provided by the SPSPseems to be more intuitive. Although it might be supposedthat addition of a second articulating instrument to SSLwould increase the surgeon’s dexterity and reduce the op-

erative time, we observed in preliminary experiments that

384 Rieder et al Single-Port Platform Enhances Performance J Am Coll Surg

it, in fact, decreases performance due to increased complex-ity. So far most available data on single-port surgery havebeen case reports or case-matched studies. A weakness ofour study includes the fact that no information on trans-ferability to the clinical outcome can be provided and ad-ditional challenges, not observed in this experimentalstudy, might occur.

Further studies also need to address the specific learningcurves required for both single-site approaches. In addi-tion, it should be evaluated whether the same level of pro-ficiency can be achieved with either standard SSL or a SPSPafter a certain period of practice.

This study objectively assesses SSL from an ergonomicstandpoint and compares it with both the “gold standard”(SL) and to a deliberate attempt to engineer a solution tothese ergonomic issues. Using this validated methodologyit was observed that the SSL approach, where crossed in-struments are basically mandatory, strongly impaired basiclaparoscopic skills compared with multiport laparoscopy.An SPSP, on the other hand, could significantly enhanceefficiency of the single-site approach and facilitated or evenenabled performance of a reliable and validated laparo-scopic drill. Surgical platforms providing a true-left and atrue-right maneuvering of instruments appear to be moreintuitive and address current challenges of SSL that mayotherwise limit its widespread acceptance or lead to patientinjury.

Author ContributionsStudy conception and design: Rieder, Martinec, Cassera,

Goers, Dunst, SwanstromAcquisition of data: Rieder, Martinec, Cassera, Goers,

Dunst, SwanstromAnalysis and interpretation of data: Rieder, Martinec,

Cassera, Goers, Dunst, SwanstromDrafting of manuscript: Rieder, Martinec, Cassera,

SwanstromCritical revision: Rieder, Martinec, Cassera, Goers, Dunst,

Swanstrom

Acknowledgment: We would like to thank TransEnterix,Durham, NC for kindly providing the SPIDER surgical sys-tem, as well as SPIDER flexible instruments; and Stryker En-doscopy, San Jose, CA, for kindly providing the 5-mm bariat-

ric endoscope.

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