重力线原则

Gravity line strategy may reduce risks of intraoperative injury during laparoscopic surgeryAnlong Zhu •Chao Yuan •Daxun Piao •Tao Jiang •Hongchi JiangReceived:2January 2013/Accepted:28June 2013/Published online:27July 2013ÓSpringer Science+Business Media New York 2013AbstractBackground ‘‘Tilt’’of surgical view was commonly shown on the monitor due to unintentional rotation of camera along its long axis by camera driver.Surgeons may be influenced on identification of anatomical structures by the tilt vision.We aimed to analyze the surgical records and videos of laparoscopic surgery,and to reveal the correlation between intraoperative complications and tilt view.Methods A series of 425consecutive patients who received laparoscopic low anterior resection and abdominoperineal resection were studied,and 398surgery videos were reviewed.Still pictures showing intraoperative injury were selected.A method was established to measure tilt angle in the still pictures according to the reference line based on several anatomic landmarks.The patients were grouped with two methods according to different study purposes.Incidence of intraoperative complication and tilt angle were calculated,and statistical analysis was performed.Results The incidence of intraoperative complications was 8.3%.Tilt of the surgical field at different degrees (\15°,15°–30°and [30°)was found in a relatively high rate in these surgery videos (31.4%).Compared with controls,comparatively bigger tilt angles were found in all cases of complication group.It is interesting to note that intraoperative complications happened more often when the tilt angle was in the range of 15°–30°(72.7%)than [30°(18.2%).We also noted a high incidence of complication(72.7%),while tilt angle was over 15°(26%)in the first 100cases;comparatively a steady declining low rate of complication occurrence (5–7%)and also tilt angle over 15°(9–11%)were noted in the later 298cases.Conclusions Rotation of camera is common during lap-aroscopic procedures.The tilt view increased the risk of laparoscopic procedures.Tilt angle at 15–30°is the most dangerous rotation for laparoscopic surgeries.Therefore,we propose the ‘‘Gravity Line Strategy’’principle as one of the basic operating criteria to correct the tilt angle.Keywords Intraoperative complications ÁLaparoscopic surgery ÁOperative techniques ÁPrevention ÁSurgical proceduresAlthough the important progress has been made in the past decade in terms of surgical equipment,techniques,and perioperative management [1,2],patients who receive laparoscopic procedures for abdominal diseases may still experience risks of intraoperative complications [3–5].It is crucial to understand not only the impact of intraoperative complications on patient survival,but also the risk factors associated with complications during laparoscopic proce-dures [6–8].Most of the intraoperative complications,including thermal injury,too-deep dissection,and technical compli-cations,are results of misidentification of anatomic struc-tures [9–11],although other less frequent factors exist [6–8,10,11].The visual perceptual illusion is the main cause accounting for the misidentification of anatomic structures [9–12],which could be led by the rotation of laparoscopic camera [13].One common phenomenon is that ‘‘tilt of laparoscopic view’’may be shown on the monitor while the laparoscopePresented at the SAGES 2013annual meeting,April 17–20,2013,Baltimore,MD.A.Zhu (&)ÁC.Yuan ÁD.Piao ÁT.Jiang ÁH.Jiang Department of General Surgery,First Affiliated Hospitalof Harbin Medical University,Harbin,Hei Long Jiang,China e-mail:zhuanlone@Surg Endosc (2013)27:4478–4484DOI 10.1007/s00464-013-3093-2is unintentionally rotated along its long axis by the camera driver.Relatively moving and tilted vision is a character of the indirect view style of laparoscopic surgery,compared with the direct vision of open surgery[14–16].The tilted view is often ignored by surgeons and may lead to misi-dentification of anatomic structures[17].To date,to our knowledge,no research has addressed the relationship between camera rotation and intraoperative complications. Therefore,we analyzed the surgical records and videos of laparoscopic surgery to study the correlation between intraoperative complications and tilted view.Patients and methodsPatientsA series of consecutive patients from September2006to June2012who received laparoscopic low anterior resec-tion(LAR)and laparoscopic abdominoperineal resection (APR)for sigmoid colon and rectal diseases in the Department of General Surgery at the First Affiliated Hospital of Harbin Medical University were included.This hospital is a teaching hospital that provides training in general surgery and laparoscopic techniques.The exclusion criteria were as follows:(1)integral operation video unavailable,(2)integral case record unavailable,and(3) conversion to open surgery not due to intraoperative inju-ries,such as adhesion,intra-abdominal phlegmon,abscess, enteric-relatedfistulae,or tumor size.These operations were performed by three different surgeons.In addition to the listed procedures,performed surgeries also included adnexectomies and appendectomies when indicated intraoperatively.Data recorded for each patient included age,sex,body mass index(BMI),indi-cation for surgery,performed surgical procedure,conver-sion to laparotomy,operating time,length of stay,and intraoperative complications.Complications and surgical proceduresIntraoperative complications such as bowel injury,ureter injury,intraoperative hemorrhages,and organ injury were recorded.Medical records,videos of the operations,and their associated complications were studied.In particular, the tilt angles of the laparoscopic view shown on the monitor were measured using the method described below.In our study,organ injuries were defined as problems in which further surgical procedures were needed.Intraoper-ative hemorrhage as a complication was recorded when specific additional treatments were applied,including active bleeding rather than oozing,hemostating procedure (controlled bleeding by compression,clamps and ligatures)over5min,blood loss of[10ml,blood transfusion,vas-cular surgery,or conversion to open surgery.Postoperative complications were excluded because of this study’s aim.The incidence of complication for each surgical procedure was calculated.In patients who underwent attempted laparoscopic resections,the peritoneal cavity was accessed by puncture or open method,and carbon dioxide was insufflated to maintain an intraperitoneal pressure of12–14mm Hg. Dissection was performed in the majority of patients by ultrasonic dissectors or with electric hook.Vessels were controlled with endoscopic staplers or absorbable clips intracorporeally in most circumstances.After bowel mobilization and vessel division,tumor-bearing segments were retrieved through an incision at a convenient site with adequate wound protection.A left-sided or rectal anasto-mosis was performed with a circular stapler that was inserted transanally.Here,rectal mobilization and tran-section followed the same principle as in open surgery.Conversion was defined as the need for a premature abdominal incision for bowel mobilization and/or vascular control.The necessity for an abdominal incision to deal with any intraoperative complication was also considered to be conversion.Measurement of tilt of laparoscopic viewDuring laparoscopic surgery,the views of the surgicalfield shown on the monitor are captured by the laparoscope;they will be tilted in accordance with the axial rotation of the camera.Therefore,the rotational angle of the camera can be calculated by measuring the tilt of the view on the screen.The procedures are as follows.First,draw a base-line(0°)parallel to the top edge of the screen on the screen as a reference orientation;second,draw another line,which represents the actual orientation of operating site(usually based on the vertical direction of gravity);and third, measure the angle between the two lines by a protractor or the MB-Ruller software program(Markus Bader,MB Software Solutions),which will be the tilt angle of camera. The tilt angle must be between0°(no camera rotation)and 180°(camera turned upside down).The actual orientation of the operating site was determined by the transversal axis of several anatomic landmarks,including bladder,uterus, and ridge of sacral bone.Figure1shows a pelvic cavity without rotation.The method to determine the angle is illustrated in Fig.2.Time point to calculate tilt angleVideos of each case were reviewed in their entirety.Video footage was suspended to calculate the tilt angle at the following time points:(1)occurrence of intraoperativecomplication (e.g.,bowel lesions,bladder injury,vaginal injury,urethral injury,bleeding);(2)bowel mobilization and vessel division (e.g.,inferior mesenteric artery,inferior mesenteric vein,ureter);and (3)ligation of vessels (e.g.,inferior mesenteric artery,inferior mesenteric vein).Grouping informationPatients with intraoperative complications were classified as the complication group,and those who received suc-cessful laparoscopic procedures comprised the control group.Patients were also categorized into four groups in chronological order (groups 1–3,100cases each group;and group 4,98cases).A consultation was held on the incidence of intraoper-ative injury after the first 100cases,and then the gravityline strategy was calculated and applied to the last 298patients.Keeping the camera in the gravity direction was emphasized in the gravity line strategy.It included three key points.First,the laparoscopic view shown on the screen should always be kept in accordance with the actual gravity direction.Second,the camera orientation must be in gravity direction.Third,the tilt angle should be con-trolled within 15°at least if the gravity direction was not able to be performed.Statistical analysisNonparametric statistical analysis was performed by the Chi square test,Fisher’s exact test,and the Mann–Whitney test,where appropriate,by SPSS 11.0software (IBM,Ar-monk,NY).ResultsIn the 6-year period between September 2006and June 2012,a total of 425laparoscopic procedures were per-formed;398cases were included in the study because operation videos of 27cases were not available.The dif-ferent diagnoses and surgical procedures performed are listed in Table 1.The population of this study consisted of patients ranging in age from 22to 82years (mean,49.8years).There were 191women (62%)and 207men (38%).The average BMI was 25.12±2.35kg/m 2(range,18.1–32.2kg/m 2).The mean duration of hospitalization was 8.5±9.7days (range,7–27days).Demographic and clinical data are listed in Table 2.Patient-,procedure-,and surgeon-specific factors were considered,including age,gender,BMI,diagnosis,Amer-ican Society of Anesthesiology classification score,oper-ative procedure,operative time,cancer staging according to the preoperative and perioperative clinical findings,and histologic tumor,node,metastasis classification for colo-rectal cancer.Intraoperative factors included thepresenceFig.1View of pelvic cavity (resection of rectum),baseline (0°)Fig.2Determination of tilt angle in the view (pelvic cavity,resection of rectum)Table 1Indications for laparoscopic procedures Indicationn (%)Sigmoid colon carcinoma 88(22.1)Sigmoid colon benign disease 4(1)Rectal carcinoma 299(75.1)Rectal benign disease 7(1.8)LAR 308(77.4)APR90(22.6)Conversion to laparotomy (among LAR and APR)11(2.7)LAR low anterior resection,APR abdominal pelvic resectionof intra-abdominal phlegmon,abscess,enteric-relatedfis-tulae,and adhesive tenacity.There was no significant dif-ference between the complication and control groups.Data for complications and the tilt angle of the laparo-scopic view are provided in Table3.Control groupIn total,365videos of successful laparoscopic procedures were reviewed.The patients were evaluated in terms of different tilt angles of the laparoscopic view.Among these, 341cases(93.4%)showed a tilt angle of less than15°and 24cases(6.5%)between15°and30°;no case had a tilt angle of more than30°(Table3).Complication groupIntraoperative complications were observed in33patients (8.29%),including ureter injuries(n=8),bladder injuries (n=3),vaginal injuries(n=3),and bleeding episodes (n=26).Multiple intraoperative complications were documented in4cases.Thirty-three videos with intraoperative complications were reviewed.In3cases(9.1%)the tilt angles of the laparoscopic view were\15°,for24cases(72.7%)between 15°and30°,and[30°in6cases(18.2%)(Table3).Results of statistical analysisThe Fisher’s exact test revealed that the percentage associ-ated with the rotational angle of the control group significantly differed from that of complication group (p\0.001).Patients without complications(n=365)had an increased rate when the rotational angle was\15°(93.4%)compared with patients in the complication group (9.1%)(p\0.001).Rates of the tilt angle between15°and 30°in the control group were significantly decreased in comparison to the complication group(6.5vs.72.7%) (p\0.001).There was also a statistically significant dif-ference between the two groups when the tilt angle was[30°(control0%plication18.2%;p\0.001)(Table3).When we analyzed the number of operations,there was a high incidence of intraoperative injury in thefirst group (p\0.05);the rate of tilt angle[15°(26%)was signifi-cantly increased compared with the other three groups (9–11%)(p\0.05).There was no case with a rotational angle of[30°in groups2–4,and the incidence of intra-operative injury decreased to a steadily low percentage (6.1–15.2%)(p\0.05)(Table4).DiscussionInexperienced camera drivers may lose a critical view during parts of an operation[6,7,18]because of their ignorance.Sometimes it is a result of not showing the surgeon the anatomic area that needs to be visualized.Also, tilt vision is shown on the viewing screen by the rotation ofTable2Demographic and clinical characteristics of patientst test,proportion test and Mann–Whitney test were performed to generate p valuesp values less than0.05are statistically significantBMI body mass index Characteristic Complication(n=33)Control(n=365)p valueAge(y),mean±SD(range)53.12±8.17(26–72)49.7±16.65(22–82)[0.05 Sex,M/F18/15189/176[0.05 BMI(kg/m2),mean±SD24.34±1.4725.17±2.67[0.05 Obese(BMI C30kg/m2),n(%)2(6.0%)21(5.8%)[0.05 Malnutrition(BMI B17kg/m2),n(%)1(3.0%)5(1.4%)[0.05 Hemoglobin(g/L),mean±SD(range)128.3±13.8125.4±17.3[0.05 Cancer/benign disease32/1355/10[0.05 Operating time(min),mean±SD(range)165±45.3(133–256)138±23.7(92–243)\0.01 Length of stay(d),mean±SD14.6±9.98.3±9.8\0.01Table3Cases with or without complication at different tilt angles Tilt angle Control,n(%)Complication,n(%)p value\15°341(93.4)3(9.1)\0.001 15°–30°24(6.5)24(72.7)\0.001 [30°0(0)6(18.2)\0.001 Total365(100)33(100)Table4Intraoperative complications and tilt angle of groups in chronological orderGroup Complication,n(%)Tilt angle,n(%)\15°15°–30°[30°1(cases1–100)24(72.7)*74(74)*20(20)*6(6)* 2(cases101–200)5(15.2)91(91)9(9)0(0) 3(cases201–300)2(6.1)89(89)11(11)0(0) 4(cases301–398)2(6.1)89(90.8)9(9.2)0(0) Fisher’s exact test was performed*Statistically significant(p\0.05)compared with other groupsthe camera.Camera rotation may have a detrimental effect on performance and may affect the surgeon’s judgment [19–21]because laparoscopic surgery is totally dependent on a visual view[9,10].In our study,398videos of APR and LAR procedures were reviewed.Tilt views were frequently observed on the screen in the operation videos.In addition,tilt views caused by unintentional camera rotation have also been shown in surgical videos presented at academic confer-ences and in teaching videos;only some of them were properly adjusted.All these examples suggest that surgeons do not pay enough attention to the axial camera rotation. Complication and control groupsGenerally,laparoscopic cameras can be rotated axially at any degree(range,0°to180°,usually0°to30°)and the intraoperative view changed accordingly[16,17,21].In our study,tilt views existed in all of the operation videos both groups.There were more cases of bigger rotational angles in the complication group than in the control group. In the complication group,tilt angles of[15°were observed in most cases(90.9%),and\15°existed in a decided minority(9.1%).In the control group,the per-centage of tilt angle of[15°was much lower(6.5%),and tilt angle of\15°was much higher(93.4%).There was no case of a tilt angle exceeding30°in the control group.The results indicate that tilt view increased the risk of intra-operative complications.It is interesting to note that intraoperative complications happened more often when the tilt of the laparoscopic view was15°–30°(72.7%)than tilt angles exceeding30°(18.2%).This could be attributed to the obvious difficulty of performing operations at tilt angles exceeding30°.In addition,such rotational views are much more easily rec-ognized by surgeons.Therefore,tilt angles of15°–30°comprise the most dangerous rotations for laparoscopic surgeries.The tilt views were mainly the result of inexperienced camera operators,who ignored the importance of proper camera direction.In addition,neither the camera operators nor the surgeons were good at controlling the cameras in the proper direction.Groups in chronological orderPatients were also categorized into four groups(100cases in each group)in chronological order.We held a consul-tation after thefirst100cases and analyzed the relationship between the incidence of intraoperative injury and the tilt of laparoscopic view.We were aware of the negative effects of tilt on the complication rate;we then constructed the gravity line strategy and applied it to the later cases. Keeping the laparoscopic camera in proper direction was emphasized in the last three groups.In thefirst100cases,apparently tilted views exceeding 15°were observed in each case several times during the whole operation;most were ignored and were not corrected to a suitable direction.On the contrary,there was a low incidence of obvious camera rotation in groups2–4,and tilted views were rectified in time in most cases.The incidence of intraoperative injury in group1(cases1–100) was higher(n=24,72.7%),along with a significantly increased rate of tilt angle of[15°(26%)than the other three groups(cases101–398,[15°,9%–11%)(p\0.05). There was no case of a tilt angle of[30°in groups2–4,and the incidence of intraoperative injury decreased to a stea-dily low percentage(5–7%)(p\0.05).Surgeons and camera operators who did not pay enough attention to camera rotation were related to a bigger tilt angle and a higher incidence of intraoperative injuries.The learning curve is considered to be a factor in the incidence of intraoperative complications.Three surgeons andfive camera operators were involved in our study.Two doctors had already completedfive procedures and one doctor had completed10procedures before the study.After thefirst100cases,two surgeons and three camera opera-torsfinished their learning curve with50cases.We think that the accumulation of experience in laparoscopic surgery helps decrease the incidence of intraoperative injury.The decline in the complication rate for the last three groups indicates that the gravity line strategy is a useful principle in laparoscopic colorectal surgery.Inexperienced camera drivers may lose critical vision or get a tilted view[16,21].The tilted view may make more it more difficult for the surgeon to identify anatomic structures[13,21].A higher risk of injury may be the result if the surgeon is not aware of the rotation of the surgical view[13].The rotation of the laparoscope is not only critical to experienced surgeons but also plays an important role in the procedures performed by less expe-rienced surgeons[14,15].We propose that the tilt of the laparoscopic view may mislead the surgeon and may be an important factor associated with accidental injury.We also noted that a rotation of\15°may be sufficient to prevent intraoperative injuries.Thus,keeping the laparoscopic view from rotating[15°may be a crucial criterion for a safe laparoscopic procedure.How,then,can novice surgeons keep the laparoscopic view in the appropriate direction?They require some practical criteria to follow.On the basis of the analysis of videos of thefirst100surgeries,we suggest that surgeons ought to abide by the gravity line.Tilt angle and gravity line strategyCommonly,laparoscopic surgical experience is derived from the performance of open surgeries.While performing surgeries,surgeons have the established perception of the relative localization of the operating site [22].Following the habit of the positional perception,the direction of gravity should be taken as the vertical coordinate of the basic reference for the operating procedure in the surgeon’s unconscious mind.This means that an object (e.g.,blood)should be always falling downward as a result of pared to open surgeries,laparoscopic surgeons viewthe operating site only from the visualization provided by the monitor [23,24].It is easy to understand that the sur-gical field shown on the monitor may be tilted when the camera is rotated.For example,a drop of blood may be seen falling from the left upper part of the screen to the right lower part instead of actually falling downward.This experience in perception of anatomic localization may mislead a surgeon,who may dissect tissue along the wrong direction if he or she has no awareness of this false front [25,26].For example,the pelvic ureter may be injured from a wrong incision direction as a result of the mis-leading tilted view when the overlying peritoneum is dis-sected in the mobilization of the rectum.Figures 3and 4show a wrong incision because of a rotational view,which may mislead surgeons to make a risky decision on the ureter.Consequently,it is crucial to keep the camera orienta-tion in the direction of gravity,in accordance with open surgeries.This should be a basic principle abided by camera operators and surgeons during laparoscopic pro-cedures.Therefore,we propose the gravity line strategy as a solution to looking at the tilt view according to the visual habit of open surgery.The gravity line strategy includes three points.First,the laparoscopic view shown on the monitor should always be kept in accordance with the direction of gravity.Second,the camera orientation must be in the direction of gravity.Finally,the tilt angle should be controlled within 15°at least if gravity direction cannot be obtained.Otherwise,an increased risk of wrong judg-ments regarding anatomical planes—and consequently an incidence of intraoperative complications—may be con-fronted.We recommend two strategies to surgeons and camera holders in following the principle of gravity line.First,camera holders must keep the ‘‘zero point’’displayed on the laparoscopic camera up or at a rotation of \15°;and second,surgeons and camera holders may adjust laparo-scope orientation by consulting anatomical landmarks,including bladder,uterus,and ridge of sacral bone.We thus recommend the gravity line strategy as a basic criterion for laparoscopic surgery;this creates an effective reference,permitting the surgeon to gain a proper percep-tion of the anatomical structure.Intraoperative complica-tions might then be decreased by the timely adjustment of the camera’s orientation.The gravity line strategy is criti-cal for surgeons and residents to understand as they develop their laparoscopic skills.Acknowledgments Supported in part by Natural Science Founda-tion of Hei Long Jiang Province (2007–64),Hei Long Jiang Post-doctoral Financial Assistance (LBH-Z05184),and the Wujieping Academician Foundation (320.6750.12188).Disclosures A.Zhu,C.Yuan,D.Piao,T.Jiang,and H.Jiang have no conflicts of interest or financial ties todisclose.Fig.3View without rotation (pelvic cavity,resection of rectum).Black line trace of ureter,blue line correct incision line on the overlying peritoneum.There is a distance between the 2lines,so it is safe to incise the overlying peritoneum along the bluelineFig.4Tilt view after camera rotation (pelvic cavity,resection of rectum).black line new trace of ureter,blue line same incision line as in Fig.3.We get a crossover of the 2line,dissecting along the blue line may lead to ureter injuryReferences1.Berguer R(1999)Surgery and ergonomics.Arch Surg134:1011–10162.Luglio G,Nelson H(2010)Laparoscopy for colon cancer:state ofthe art.Surg Oncol Clin N Am19:777–7913.Inoue T,Kinoshita H,Satou M,Oguchi N,Kawa G,MugurumaK,Murota T,Matsuda T(2010)Complications of urologic lap-aroscopic surgery:a single institute experience of1017proce-dures.J Endourol24:253–2604.Lebeau T,Roupreˆt M,Ferhi K,Chartier-Kastler E,Richard F,Bitker MO,Vaessen C(2010)Assessing the complications of laparoscopic robot-assisted surgery:the case of radical prosta-tectomy.Surg Endosc25:536–5425.Strasberg SM,Hertl M,Soper NJ(1995)An analysis of theproblem of biliary injury during laparoscopic cholecystectomy.J Am Coll Surg180:101–1256.Schlachta CM,Mamazza J,Seshadri PA,Cadeddu M,Poulin EC(2000)Determinants of outcomes in laparoscopic colorectal surgery:a multiple regression analysis of416resections.Surg Endosc14:258–2637.Khoury W,Kiran RP,Jessie T,Geisler D,Remzi FH(2009)Is thelaparoscopic approach to colectomy safe for the morbidly obese?Surg Endosc24:1336–13408.Shin EJ,Kalloo AN(2009)Transcolonic NOTES:currentexperience and potential implications for urologic applications.J Endourol23:743–7469.Duff WM(2006)Avoiding misidentification injuries in laparo-scopic cholecystectomy:use of cystic duct marking technique in intraoperative cholangiography.J Am Coll Surg203:257–261 10.Jones DB,Brewer JD,Soper NJ(1996)The influence of three-dimensional video systems on laparoscopic task performance.Surg Laparosc Endosc6:191–19711.Strasberg SM(2005)Biliary injury in laparoscopic surgery:part1.Processes used in determination of standard of care in misi-dentification injuries.J Am Coll Surg201:598–60312.Hanna G,Shimi S,Cuschieri A(1998)Randomized study ofinfluence of two-dimensional versus three-dimensional imaging on performance of laparoscopic ncet351:249–251 13.Conrad J,Shah AH,Divino CM,Schluender S,Gurland B,Shlasko E,Szold A(2006)The role of mental rotation and memory scanning on the performance of laparoscopic skills:a study on the effect of camera rotational angle.Surg Endosc20:504–51014.Sarker SJ,Telfah MM,Onuba L,Patel BP(in press)Objectiveassessment of skills acquisition during laparoscopic surgery courses.Surg Innov15.Honeck P,Wendt-Nordahl G,Rassweiler J,Knoll T(2012)Three-dimensional laparoscopic imaging improves surgical per-formance on standardized ex vivo laparoscopic tasks.J Endourol 26:1085–108816.Nakamoto M,Ukimura O,Faber K,Gill IS(2012)Current pro-gress on augmented reality visualization in endoscopic surgery.Curr Opin Urol22:121–12617.Gallagher AG,Al-Akash M,Seymour NE,Satava RM(2009)Anergonomic analysis of the effects of camera rotation on laparo-scopic performance.Surg Endosc23:2684–269118.Autorino R,Haber GP,Stein RJ,Rane A,De Sio M,White MA,Yang B,de la Rosette JJ,Kaouk JH,Laguna M(2010)Laparo-scopic training in urology critical analysis of current evidence.J Endourol24:1377–139019.Vettoretto N,Saronni C,Harbi A,Balestra L,Taglietti L,Gi-ovanetti M(2010)Critical view of safety during laparoscopic cholecystectomy.JSLS15:322–32520.Machado NO(2011)Biliary complications postlaparoscopiccholecystectomy:mechanism,preventive measures,and approach to management:a review.Diagn Ther Endosc2011:967017 21.Breedveld P,Wentink M(2001)Eye–hand coordination in lap-aroscopy—an overview of experiments and supporting aids.Minim Invasive Ther Allied Technol10:155–16222.Risucci DA(2002)Visual spatial perception and surgical com-petence.Am J Surg184:291–29523.Bittner JG,Hathaway CA,Brown JA(2008)Three-dimensionalvisualisation and articulating instrumentation:impact on simu-lated laparoscopic tasks.J Minim Access Surg4:31–3824.Bhayani SB,Andriole GL(2005)Three-dimensional(3D)vision:does it improve laparoscopic skills?an assessment of a3D head-mounted visualization system.Rev Urol7:211–21425.Cheah WK,Lenzi JE,So J,Dong F,Kum CK,Goh P(2001)Evaluation of a head-mounted display(HMD)in the performance of a simulated laparoscopic task.Surg Endosc15:990–991 26.Bishop PO,Kozak W,Vakkur GJ(1962)Some quantitativeaspects of the cat’s eye:axis and plane of reference,visualfield co-ordinates and optics.J Physiol163:466–502。