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The use of a biological model for comparing two techniques of fluoroscopy-guided percutaneous puncture: A randomised cross-over study

The use of a biological model for comparing two techniques of fluoroscopy-guided percutaneous... Arab Journal of Urology (2013) 11,79–84 Arab Journal of Urology (Official Journal of the Arab Association of Urology) www.sciencedirect.com STONES/ENDOUROLOGY ORIGINAL ARTICLE The use of a biological model for comparing two techniques of fluoroscopy-guided percutaneous puncture: A randomised cross-over study Mohamed M. Abdallah , Shady M. Salem, Mohamed R. Badreldin, Ahmed A. Gamaleldin Faculty of Medicine, Department of Urology, Shibin Elkom, Menofiya University, Egypt Received 13 October 2012, Received in revised form 9 December 2012, Accepted 9 December 2012 Available online 15 January 2013 KEYWORDS Abstract Objectives: To develop a new and inexpensive model for training in fluo- roscopic puncture into the pelvicalyceal system, and to use this model to compare Percutaneous nephro- the learning curve of two fluoroscopic techniques, the ‘eye of the needle’ (EN) and lithotomy; triangulation techniques. Biological model; Materials and methods: For the trial we used a commercial plastic model (a shop- Triangulation; window mannequin) in which a bovine kidney, embedded in sponge with a spatial Radical; orientation similar to the human, was inserted into the model. The ureter of the ani- Eye of the needle mal kidney was connected to contrast fluid. Ten residents and interns were random- ised into two groups; group A started the puncture using the EN technique, each ABBREVIATIONS member making five attempts, and then five attempts using the triangulation tech- PCNL, percutaneous nique, and group B started with triangulation and then used the EN technique. nephrolithotomy; EM, Results: There was no statistically significant difference between the techniques eye of the needle for the mean (SD) number of trials to make a correct puncture, at 2.68 (1.00) in (technique) the EN technique and 2.86 (1.05) in the triangulation technique, or for the duration of each trial, at 523 (189) s for the EN technique and 578 (175) s for the triangulation technique. The fluoroscopy time was less in the EN technique, at 113.9 (48.9) s than for the triangulation method, at 135.8 (42.4) (P < 0.005). Corresponding author. Tel.: +20 1003413438. E-mail address: mmarzouk@yahoo.com (M.M. Abdallah). Peer review under responsibility of Arab Association of Urology. Production and hosting by Elsevier 2090-598X ª 2012 Arab Association of Urology. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aju.2012.12.001 80 Abdallah et al. Conclusions: The model was easy to construct and feasible for training. Both tech- niques had a similar learning curve, with higher fluoroscopy exposure for the trian- gulation technique. ª 2012 Arab Association of Urology. Production and hosting by Elsevier B.V. All rights reserved. Introduction paucity of training models and simulators [11]. The devised models can be generally categorised into three types: (1) Computer-based virtual environments like The role of percutaneous renal procedures in urology is the inanimate and virtual-reality simulators [12]; (2) expanding to cover several domains. Percutaneous neph- Biologically based models like an infused porcine kidney rolithotomy (PCNL) is the method of choice for stones in a chicken carcass [13]; and (3) using a thin-slice CT of > 2 cm, and percutaneous access is also used for image to create a patient-specific three-dimensional endopyelotomy and the management of renal TCC model of the kidney, and then using a rapid proto- [1,2]. Overall there is increasing use of PCNL, especially typing machine to produce a silicon model for the for complex stones, staghorn and lower-pole stones [3,4]. kidney [14]. Making a puncture is the first step in PCNL and can be McDougall et al. [15] proposed several definitions described as the key step for any percutaneous procedure. (face validity, content validity, construct validity and Complications associated with a faulty puncture include criterion validity) to allow objective judgements of surgi- failure to complete the procedure, obtaining less than cal training models. In brief, ‘face validity’ is a measure optimal access (making the procedure more difficult), of the opinion of non-experts about the simulator, ‘con- bleeding, and injury to the surrounding structures [5]. tent validity’ the opinion of experts about the simulator, The puncture can be done either by a urologist or by ‘construct validity’ is the ability of the simulator to dis- a radiologist, with similar complications and stone-free tinguish between different levels of experience, measured rates, but when urologists alone make the access they within one trainee over time or between groups of train- tend to manage more complex stones and use several ees. The criterion validity is the predictive validity corre- and supracostal punctures more often than do radiolo- lation of trainees’ performance on the model with gists [6]. operating-room performance. Two techniques are commonly used to insert the In the present study we aimed to develop a new and puncture needle into the collecting system, i.e. the ‘eye inexpensive model for training in fluoroscopic puncture of the needle’ (EN) technique and the triangulation tech- into the pelvicalyceal system, then to use the model to nique. In the latter (Fig. 1A and B), the targeted calyx is compare the learning curve of two fluoroscopic tech- identified, a C-arm is positioned parallel to the line of niques of pelvicalyceal puncture (EN and triangulation). the puncture (position A) then the C-arm is turned ob- liquely (cephalo-caudal) 30 to this line (position B). Materials and methods In position A the needle is adjusted mediolaterally, and in position B adjustments are made up and down, with careful monitoring to ensure the same orientation The study was approved by the ethics committee of our as the mediolateral position of the needle [7]. hospital. We started with a commercial model (a manne- The EN technique (Fig. 2) entails aligning the desired quin) of the kind used in clothing-shop windows. We calyx, the tip of the needle, the hub of the needle and the chose one with dimensions and curves similar to the axis of the X-ray beam. This gives a ‘bull’s eye’ effect. average person, into which was placed a kidney from a The needle is then advanced and the depth is controlled freshly slaughtered cow. The ureter, renal artery and using a lateral C-arm view [7]. vein were identified, and the kidney was flushed with The learning curve for PCNL is not yet clearly de- cold normal saline until the efflux from the renal vein fined; Two reports of a single-surgeon experience sug- was clear (Fig. 3). We then used two sheets of sponge gested that proficiency in PCNL is obtained after 60 to cover the kidney and placed it inside the mannequin, cases [8,9]. A survey from the USA showed that a urol- keeping it as close as possible to the normal kidney ogist trained on PCNL during their residency undertook orientation and position. A window was created in the more PCNLs after that residency and was more com- model where the needle puncture should start and part fortable doing PCNL. The authors suggested that resi- of an aubergine (eggplant, Solanum melongena) was used dents should perform >24 PCNLs during their to mimic the human cuticle. The model was then residency [10]. checked under fluoroscopy for the integrity of the pel- Despite the steep learning curve of PCNL and poten- vicalyceal system, and the correct position of the whole tially grave complications for such a procedure there is a kidney was ascertained (Fig. 4A and B). Comparison of Eye of the Needle Method with the Triangulation Technique 81 A group of five residents and five interns volun- pelvicalyceal system, and then five punctures using the teered to participate in the study. They had no expe- EN technique. Then group B started by making five rience of PCNL (none of them had participated in punctures to the pelvicalyceal system using the EN tech- PCNL or made a fluoroscopy-guided puncture). The nique, followed by five with the triangulation technique. 10 participants were randomised into two groups, A The two groups were not together during the study. We and B, by selecting a folded paper from a container measured the number of trials until there was a correct of 10 folded papers with five marked group A and five puncture, and the total fluoroscopy time and total time group B. for each trial. After a detailed presentation of both techniques by After finishing the two training sessions the partici- two of the authors who had extensive experience of pants answered a simple questionnaire developed by PCNL, one of them using the triangulation technique the authors, the questions being: (1) Do you feel this primarily and the other the EN method primarily. Each training session is useful?; (2) Does it improve your presented his method and stayed as a guide and mentor understanding of fluoroscopically guided puncture?; (3) during the study. Do you think this session will be reflected in your train- Group A started by using the triangulation tech- ing on PCNL? The only answers allowed were ‘yes’ or nique, with each member making five punctures of the ‘no’. Figure 1 (A) An anteroposterior puncture in the triangulation technique, with the C-arm in position B; (B) a fluoroscopic image showing two syringe tips marking the targeted calyx, with the C-arm in position A and B, with the puncture seen in the horizontal plane. 82 Abdallah et al. Figure 2 A fluoroscopic image of the EN technique. After accumulating data from the two techniques from both groups, the Kruskal–Wallis test and Spear- man’s correlation were used to assess the results, with P < 0.05 taken to indicate significant differences. Results Overall the model was easy to construct, inexpensive and allowed trainees to practice the two methods of PCNL puncture. Each cow’s kidney allowed a mean of 20 punctures in different calyces. All the trainees re- ported satisfaction in the anonymous questionnaire completed after the trial. The performance of the two groups was compared after combining the results of the trials in both tech- niques; there were no statistically significant difference Figure 3 The kidney of a freshly slaughtered cow; the ureter is between the groups for all three measurements (Table 1). cannulated with a Nelaton catheter. To compare the EN and triangulation techniques we combined measurements from the two groups. There was no statistically significant difference between the improvement in the three measurements with repeated techniques for either the number of punctures needed trials in the two techniques. Spearman’s correlation test for correct access to the targeted calyx or the total time for the correlation between the number of trials and the (Table 1). The mean fluoroscopy time was shorter for study measurements is also shown in Table 1. The ques- the EN technique (P = 0.01). tionnaire showed that all participants answered the three To show the effect of gaining experience in one tech- questions with ‘Yes’. nique when using the other we compared the three mea- surements for each of the techniques between the two Discussion groups. There were no statistically significant differences in the three measurements in the triangulation technique (Table 1), but comparing the two groups for the EN The ideal training model should resemble the actual pro- technique, group A (which started with triangulation) cedure in almost every aspect, be able to show the progress had shorter mean total and fluoroscopy times for each of trainees during training, and facilitate translation of puncture than had group B (Table 1). There was an the skills as improved performance in real cases. Comparison of Eye of the Needle Method with the Triangulation Technique 83 Construction of the present model was simple, as the fresh cow kidneys are inexpensive and the pelvicalyceal system is similar to that of the human to a great extent. This model fulfilled face validity, but the content validity, construct validity and criterion validity could not be confirmed for this model [15]. The use of the eggplant cuticle gives the texture of hu- man skin, and the use of shop-window mannequin al- lowed the kidney to be orientated in the space similar to that in the human. The orientation was better than that used by Earp [16], where a sheet of foam was used to resemble the human body. The catheter attached to the ureter allowed the kidneys to be flushed with con- trast material, to facilitate fluoroscopy. The advantage of the fresh cow kidney was that it allowed many punc- tures with no extravasation of the dye. This model is easy to construct and reassemble. It can be used to sim- ulate both supine and prone PCNL. The use of a biological model has advantages over computer-based models in that it provides a feedback sensation of different tissue resistance [12]. Our model was better than that of Hacker et al. [13], who used a porcine kidney in a chicken carcass, as it provided a greater appreciation of the kidney position in relation to the human body. In the present study the mean fluoroscopy time was shorter in the EN technique, but there was no statistically significant difference between the techniques for either the number of punctures or the total time. However, in a clinical setting, Tepeler et al. [17], comparing 40 pa- tients undergoing PCNL for a simple renal stone using Figure 4 (A) The construction of the model; (B) the bovine the EN technique with 40 using triangulation, found kidney under fluoroscopy. Table 1 The comparison between the groups and between the techniques. Variable Mean (SD) Number of punctures Total duration (s) Fluoroscopy time (s) Group A 2.9 (0.96) 506 (156) 116.0 (44.3) Group B 2.62 (1.06) 594 (200) 133.7 (48.0) P 0.117 0.031 0.059 Triangulation 2.86 (1.04) 578 (175) 135.78 (42.4) EN 2.68 (0.99) 523 (189) 113.92 (48.8) P 0.32 0.07 0.01 Triangulation Group A 3.2 (1.08) 549 (175) 137.3 (45.8) Group B 2.52 (0.92) 607 (174) 134.2 (39.5) P 1.0 0.29 0.80 EN Group A 2.64 (0.76) 463 (117) 94.7 (31.0) Group B 2.72 (1.21) 538 (227) 133.1 (56.1) P 1.0 0.074 0.005 Spearman’s correlation Triangulation 0.43 0.33 0.35 P <0.01 0.02 0.01 EN 0.41 0.53 0.54 P <0.01 <0.01 <0.01 correlation between the number of trials and the study measurements in the two techniques. 84 Abdallah et al. [3] El-Nahas AR, Eraky I, Shokeir AA, et al. Percutaneous neph- no statistically significant difference in fluoroscopy time rolithotomy for treating staghorn stones: 10 years of experience of and operative duration between the techniques. a tertiary-care centre. Arab J Urol 2012;10:324–9. We acknowledge that this model has several limita- [4] Morris DS, Taub DA, Wei JT, Dunn RL, Wolf Jr JS, Hollenbeck tions. It was not designed to allow a complete PCNL BK. Regionalization of percutaneous nephrolithotomy: evidence procedure, including dilatation and stone extraction. for the increasing burden of care on tertiary centers. J Urol 2006;176:242–6. The complications of PCNL cannot be reproduced, [5] Michel MS, Trojan L, Rassweiler JJ. Complications in percuta- e.g., bleeding, or injury to adjacent organs. Also, this neous nephrolithotomy. Eur Urol 2007;51:899–906. model allowed only fluoroscopically guided but not [6] El-Assmy AM, Shokeir AA, Mohsen T, El-Tabey N, El-Nahas ultrasonically guided puncture. The study had relatively AM, Shoma AM, et al. Renal access by urologist or radiologist few participants which increased the a error. We hope for percutaneous nephrolithotomy–is it still an issue? J Urol 2007;178:916–20. that further studies can have more participants with bet- [7] Miller NL, Matlaga BR, Lingeman JE. Techniques for fluoro- ter designed models. scopic percutaneous renal access. J Urol 2007;178:15–23. In conclusion, the present model was inexpensive, [8] Allen D, O’Brien T, Tiptaft R, Glass J. Defining the learning easy to construct, and had face validity. Both the EN curve for percutaneous nephrolithotomy. J Endourol and triangulation techniques can be done easily in the 2005;19:279–82. [9] Tanriverdi O, Boylu U, Kendirci M, Kadihasanoglu M, Horas- model, with improved performance while training. anli K, Miroglu C. The learning curve in the training of When comparing both methods, there were no differ- percutaneous nephrolithotomy. Eur Urol 2007;52:206–11. ences in total time and the number of punctures, but [10] Lee CL, Anderson JK, Monga M. Residency training in percu- the EN technique was associated with a shorter fluoros- taneous renal access: does it affect urological practice? J Urol copy time. 2004;171:592–5. [11] de la Rosette JJ, Laguna MP, Rassweiler JJ, Conort P. Training in percutaneous nephrolithotomy – a critical review. Eur Urol Conflict of interest 2008;54:994–1001. [12] Laguna MP, Hatzinger M, Rassweiler J. Simulators and endou- None. rological training. Curr Opin Urol 2002;12:209–15. [13] Hacker A, Wendt-Nordahl G, Honeck P, Michel MS, Alken P, Knoll T. A biological model to teach percutaneous nephrolithot- Funding omy technique with ultrasound- and fluoroscopy-guided access. J Endourol 2007;21:545–50. None. [14] Bruyere F, Leroux C, Brunereau L, Lermusiaux P. Rapid prototyping model for percutaneous nephrolithotomy training. J References Endourol 2008;22:91–6. [15] McDougall EM. Validation of surgical simulators. J Endourol 2007;21:244–7. [1] Knudsen BE, Cook AJ, Watterson JD, Beiko DT, Nott L, Razvi [16] Earp PP. Percutaneous renal surgery – new model for learning H, et al. Percutaneous antegrade endopyelotomy: long-term and training. Int Braz J Urol 2003;29:151–4. results from one institution. Urology 2004;63:230–4. [17] Tepeler A, Armagan A, Akman T, Polat EC, Erso¨ z C, Topaktas R, [2] Thompson RH, Krambeck AE, Lohse CM, Elliott DS, Patterson et al. Impact of percutaneous renal access technique on outcomes ML, Blute ML. Endoscopic management of upper tract transi- of percutaneous nephrolithotomy. J Endourol 2004;26:828–33. tional cell carcinoma in patients with normal contralateral kidneys. Urology 2008;71:713–7. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Arab Journal of Urology Taylor & Francis

The use of a biological model for comparing two techniques of fluoroscopy-guided percutaneous puncture: A randomised cross-over study

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Arab Journal of Urology (2013) 11,79–84 Arab Journal of Urology (Official Journal of the Arab Association of Urology) www.sciencedirect.com STONES/ENDOUROLOGY ORIGINAL ARTICLE The use of a biological model for comparing two techniques of fluoroscopy-guided percutaneous puncture: A randomised cross-over study Mohamed M. Abdallah , Shady M. Salem, Mohamed R. Badreldin, Ahmed A. Gamaleldin Faculty of Medicine, Department of Urology, Shibin Elkom, Menofiya University, Egypt Received 13 October 2012, Received in revised form 9 December 2012, Accepted 9 December 2012 Available online 15 January 2013 KEYWORDS Abstract Objectives: To develop a new and inexpensive model for training in fluo- roscopic puncture into the pelvicalyceal system, and to use this model to compare Percutaneous nephro- the learning curve of two fluoroscopic techniques, the ‘eye of the needle’ (EN) and lithotomy; triangulation techniques. Biological model; Materials and methods: For the trial we used a commercial plastic model (a shop- Triangulation; window mannequin) in which a bovine kidney, embedded in sponge with a spatial Radical; orientation similar to the human, was inserted into the model. The ureter of the ani- Eye of the needle mal kidney was connected to contrast fluid. Ten residents and interns were random- ised into two groups; group A started the puncture using the EN technique, each ABBREVIATIONS member making five attempts, and then five attempts using the triangulation tech- PCNL, percutaneous nique, and group B started with triangulation and then used the EN technique. nephrolithotomy; EM, Results: There was no statistically significant difference between the techniques eye of the needle for the mean (SD) number of trials to make a correct puncture, at 2.68 (1.00) in (technique) the EN technique and 2.86 (1.05) in the triangulation technique, or for the duration of each trial, at 523 (189) s for the EN technique and 578 (175) s for the triangulation technique. The fluoroscopy time was less in the EN technique, at 113.9 (48.9) s than for the triangulation method, at 135.8 (42.4) (P < 0.005). Corresponding author. Tel.: +20 1003413438. E-mail address: mmarzouk@yahoo.com (M.M. Abdallah). Peer review under responsibility of Arab Association of Urology. Production and hosting by Elsevier 2090-598X ª 2012 Arab Association of Urology. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aju.2012.12.001 80 Abdallah et al. Conclusions: The model was easy to construct and feasible for training. Both tech- niques had a similar learning curve, with higher fluoroscopy exposure for the trian- gulation technique. ª 2012 Arab Association of Urology. Production and hosting by Elsevier B.V. All rights reserved. Introduction paucity of training models and simulators [11]. The devised models can be generally categorised into three types: (1) Computer-based virtual environments like The role of percutaneous renal procedures in urology is the inanimate and virtual-reality simulators [12]; (2) expanding to cover several domains. Percutaneous neph- Biologically based models like an infused porcine kidney rolithotomy (PCNL) is the method of choice for stones in a chicken carcass [13]; and (3) using a thin-slice CT of > 2 cm, and percutaneous access is also used for image to create a patient-specific three-dimensional endopyelotomy and the management of renal TCC model of the kidney, and then using a rapid proto- [1,2]. Overall there is increasing use of PCNL, especially typing machine to produce a silicon model for the for complex stones, staghorn and lower-pole stones [3,4]. kidney [14]. Making a puncture is the first step in PCNL and can be McDougall et al. [15] proposed several definitions described as the key step for any percutaneous procedure. (face validity, content validity, construct validity and Complications associated with a faulty puncture include criterion validity) to allow objective judgements of surgi- failure to complete the procedure, obtaining less than cal training models. In brief, ‘face validity’ is a measure optimal access (making the procedure more difficult), of the opinion of non-experts about the simulator, ‘con- bleeding, and injury to the surrounding structures [5]. tent validity’ the opinion of experts about the simulator, The puncture can be done either by a urologist or by ‘construct validity’ is the ability of the simulator to dis- a radiologist, with similar complications and stone-free tinguish between different levels of experience, measured rates, but when urologists alone make the access they within one trainee over time or between groups of train- tend to manage more complex stones and use several ees. The criterion validity is the predictive validity corre- and supracostal punctures more often than do radiolo- lation of trainees’ performance on the model with gists [6]. operating-room performance. Two techniques are commonly used to insert the In the present study we aimed to develop a new and puncture needle into the collecting system, i.e. the ‘eye inexpensive model for training in fluoroscopic puncture of the needle’ (EN) technique and the triangulation tech- into the pelvicalyceal system, then to use the model to nique. In the latter (Fig. 1A and B), the targeted calyx is compare the learning curve of two fluoroscopic tech- identified, a C-arm is positioned parallel to the line of niques of pelvicalyceal puncture (EN and triangulation). the puncture (position A) then the C-arm is turned ob- liquely (cephalo-caudal) 30 to this line (position B). Materials and methods In position A the needle is adjusted mediolaterally, and in position B adjustments are made up and down, with careful monitoring to ensure the same orientation The study was approved by the ethics committee of our as the mediolateral position of the needle [7]. hospital. We started with a commercial model (a manne- The EN technique (Fig. 2) entails aligning the desired quin) of the kind used in clothing-shop windows. We calyx, the tip of the needle, the hub of the needle and the chose one with dimensions and curves similar to the axis of the X-ray beam. This gives a ‘bull’s eye’ effect. average person, into which was placed a kidney from a The needle is then advanced and the depth is controlled freshly slaughtered cow. The ureter, renal artery and using a lateral C-arm view [7]. vein were identified, and the kidney was flushed with The learning curve for PCNL is not yet clearly de- cold normal saline until the efflux from the renal vein fined; Two reports of a single-surgeon experience sug- was clear (Fig. 3). We then used two sheets of sponge gested that proficiency in PCNL is obtained after 60 to cover the kidney and placed it inside the mannequin, cases [8,9]. A survey from the USA showed that a urol- keeping it as close as possible to the normal kidney ogist trained on PCNL during their residency undertook orientation and position. A window was created in the more PCNLs after that residency and was more com- model where the needle puncture should start and part fortable doing PCNL. The authors suggested that resi- of an aubergine (eggplant, Solanum melongena) was used dents should perform >24 PCNLs during their to mimic the human cuticle. The model was then residency [10]. checked under fluoroscopy for the integrity of the pel- Despite the steep learning curve of PCNL and poten- vicalyceal system, and the correct position of the whole tially grave complications for such a procedure there is a kidney was ascertained (Fig. 4A and B). Comparison of Eye of the Needle Method with the Triangulation Technique 81 A group of five residents and five interns volun- pelvicalyceal system, and then five punctures using the teered to participate in the study. They had no expe- EN technique. Then group B started by making five rience of PCNL (none of them had participated in punctures to the pelvicalyceal system using the EN tech- PCNL or made a fluoroscopy-guided puncture). The nique, followed by five with the triangulation technique. 10 participants were randomised into two groups, A The two groups were not together during the study. We and B, by selecting a folded paper from a container measured the number of trials until there was a correct of 10 folded papers with five marked group A and five puncture, and the total fluoroscopy time and total time group B. for each trial. After a detailed presentation of both techniques by After finishing the two training sessions the partici- two of the authors who had extensive experience of pants answered a simple questionnaire developed by PCNL, one of them using the triangulation technique the authors, the questions being: (1) Do you feel this primarily and the other the EN method primarily. Each training session is useful?; (2) Does it improve your presented his method and stayed as a guide and mentor understanding of fluoroscopically guided puncture?; (3) during the study. Do you think this session will be reflected in your train- Group A started by using the triangulation tech- ing on PCNL? The only answers allowed were ‘yes’ or nique, with each member making five punctures of the ‘no’. Figure 1 (A) An anteroposterior puncture in the triangulation technique, with the C-arm in position B; (B) a fluoroscopic image showing two syringe tips marking the targeted calyx, with the C-arm in position A and B, with the puncture seen in the horizontal plane. 82 Abdallah et al. Figure 2 A fluoroscopic image of the EN technique. After accumulating data from the two techniques from both groups, the Kruskal–Wallis test and Spear- man’s correlation were used to assess the results, with P < 0.05 taken to indicate significant differences. Results Overall the model was easy to construct, inexpensive and allowed trainees to practice the two methods of PCNL puncture. Each cow’s kidney allowed a mean of 20 punctures in different calyces. All the trainees re- ported satisfaction in the anonymous questionnaire completed after the trial. The performance of the two groups was compared after combining the results of the trials in both tech- niques; there were no statistically significant difference Figure 3 The kidney of a freshly slaughtered cow; the ureter is between the groups for all three measurements (Table 1). cannulated with a Nelaton catheter. To compare the EN and triangulation techniques we combined measurements from the two groups. There was no statistically significant difference between the improvement in the three measurements with repeated techniques for either the number of punctures needed trials in the two techniques. Spearman’s correlation test for correct access to the targeted calyx or the total time for the correlation between the number of trials and the (Table 1). The mean fluoroscopy time was shorter for study measurements is also shown in Table 1. The ques- the EN technique (P = 0.01). tionnaire showed that all participants answered the three To show the effect of gaining experience in one tech- questions with ‘Yes’. nique when using the other we compared the three mea- surements for each of the techniques between the two Discussion groups. There were no statistically significant differences in the three measurements in the triangulation technique (Table 1), but comparing the two groups for the EN The ideal training model should resemble the actual pro- technique, group A (which started with triangulation) cedure in almost every aspect, be able to show the progress had shorter mean total and fluoroscopy times for each of trainees during training, and facilitate translation of puncture than had group B (Table 1). There was an the skills as improved performance in real cases. Comparison of Eye of the Needle Method with the Triangulation Technique 83 Construction of the present model was simple, as the fresh cow kidneys are inexpensive and the pelvicalyceal system is similar to that of the human to a great extent. This model fulfilled face validity, but the content validity, construct validity and criterion validity could not be confirmed for this model [15]. The use of the eggplant cuticle gives the texture of hu- man skin, and the use of shop-window mannequin al- lowed the kidney to be orientated in the space similar to that in the human. The orientation was better than that used by Earp [16], where a sheet of foam was used to resemble the human body. The catheter attached to the ureter allowed the kidneys to be flushed with con- trast material, to facilitate fluoroscopy. The advantage of the fresh cow kidney was that it allowed many punc- tures with no extravasation of the dye. This model is easy to construct and reassemble. It can be used to sim- ulate both supine and prone PCNL. The use of a biological model has advantages over computer-based models in that it provides a feedback sensation of different tissue resistance [12]. Our model was better than that of Hacker et al. [13], who used a porcine kidney in a chicken carcass, as it provided a greater appreciation of the kidney position in relation to the human body. In the present study the mean fluoroscopy time was shorter in the EN technique, but there was no statistically significant difference between the techniques for either the number of punctures or the total time. However, in a clinical setting, Tepeler et al. [17], comparing 40 pa- tients undergoing PCNL for a simple renal stone using Figure 4 (A) The construction of the model; (B) the bovine the EN technique with 40 using triangulation, found kidney under fluoroscopy. Table 1 The comparison between the groups and between the techniques. Variable Mean (SD) Number of punctures Total duration (s) Fluoroscopy time (s) Group A 2.9 (0.96) 506 (156) 116.0 (44.3) Group B 2.62 (1.06) 594 (200) 133.7 (48.0) P 0.117 0.031 0.059 Triangulation 2.86 (1.04) 578 (175) 135.78 (42.4) EN 2.68 (0.99) 523 (189) 113.92 (48.8) P 0.32 0.07 0.01 Triangulation Group A 3.2 (1.08) 549 (175) 137.3 (45.8) Group B 2.52 (0.92) 607 (174) 134.2 (39.5) P 1.0 0.29 0.80 EN Group A 2.64 (0.76) 463 (117) 94.7 (31.0) Group B 2.72 (1.21) 538 (227) 133.1 (56.1) P 1.0 0.074 0.005 Spearman’s correlation Triangulation 0.43 0.33 0.35 P <0.01 0.02 0.01 EN 0.41 0.53 0.54 P <0.01 <0.01 <0.01 correlation between the number of trials and the study measurements in the two techniques. 84 Abdallah et al. [3] El-Nahas AR, Eraky I, Shokeir AA, et al. Percutaneous neph- no statistically significant difference in fluoroscopy time rolithotomy for treating staghorn stones: 10 years of experience of and operative duration between the techniques. a tertiary-care centre. Arab J Urol 2012;10:324–9. We acknowledge that this model has several limita- [4] Morris DS, Taub DA, Wei JT, Dunn RL, Wolf Jr JS, Hollenbeck tions. It was not designed to allow a complete PCNL BK. Regionalization of percutaneous nephrolithotomy: evidence procedure, including dilatation and stone extraction. for the increasing burden of care on tertiary centers. J Urol 2006;176:242–6. The complications of PCNL cannot be reproduced, [5] Michel MS, Trojan L, Rassweiler JJ. Complications in percuta- e.g., bleeding, or injury to adjacent organs. Also, this neous nephrolithotomy. Eur Urol 2007;51:899–906. model allowed only fluoroscopically guided but not [6] El-Assmy AM, Shokeir AA, Mohsen T, El-Tabey N, El-Nahas ultrasonically guided puncture. The study had relatively AM, Shoma AM, et al. Renal access by urologist or radiologist few participants which increased the a error. We hope for percutaneous nephrolithotomy–is it still an issue? J Urol 2007;178:916–20. that further studies can have more participants with bet- [7] Miller NL, Matlaga BR, Lingeman JE. Techniques for fluoro- ter designed models. scopic percutaneous renal access. J Urol 2007;178:15–23. In conclusion, the present model was inexpensive, [8] Allen D, O’Brien T, Tiptaft R, Glass J. Defining the learning easy to construct, and had face validity. Both the EN curve for percutaneous nephrolithotomy. J Endourol and triangulation techniques can be done easily in the 2005;19:279–82. [9] Tanriverdi O, Boylu U, Kendirci M, Kadihasanoglu M, Horas- model, with improved performance while training. anli K, Miroglu C. The learning curve in the training of When comparing both methods, there were no differ- percutaneous nephrolithotomy. Eur Urol 2007;52:206–11. ences in total time and the number of punctures, but [10] Lee CL, Anderson JK, Monga M. Residency training in percu- the EN technique was associated with a shorter fluoros- taneous renal access: does it affect urological practice? J Urol copy time. 2004;171:592–5. [11] de la Rosette JJ, Laguna MP, Rassweiler JJ, Conort P. Training in percutaneous nephrolithotomy – a critical review. Eur Urol Conflict of interest 2008;54:994–1001. [12] Laguna MP, Hatzinger M, Rassweiler J. Simulators and endou- None. rological training. Curr Opin Urol 2002;12:209–15. [13] Hacker A, Wendt-Nordahl G, Honeck P, Michel MS, Alken P, Knoll T. A biological model to teach percutaneous nephrolithot- Funding omy technique with ultrasound- and fluoroscopy-guided access. J Endourol 2007;21:545–50. None. [14] Bruyere F, Leroux C, Brunereau L, Lermusiaux P. Rapid prototyping model for percutaneous nephrolithotomy training. J References Endourol 2008;22:91–6. [15] McDougall EM. Validation of surgical simulators. J Endourol 2007;21:244–7. [1] Knudsen BE, Cook AJ, Watterson JD, Beiko DT, Nott L, Razvi [16] Earp PP. Percutaneous renal surgery – new model for learning H, et al. Percutaneous antegrade endopyelotomy: long-term and training. Int Braz J Urol 2003;29:151–4. results from one institution. Urology 2004;63:230–4. [17] Tepeler A, Armagan A, Akman T, Polat EC, Erso¨ z C, Topaktas R, [2] Thompson RH, Krambeck AE, Lohse CM, Elliott DS, Patterson et al. Impact of percutaneous renal access technique on outcomes ML, Blute ML. Endoscopic management of upper tract transi- of percutaneous nephrolithotomy. J Endourol 2004;26:828–33. tional cell carcinoma in patients with normal contralateral kidneys. Urology 2008;71:713–7.

Journal

Arab Journal of UrologyTaylor & Francis

Published: Mar 1, 2013

Keywords: Percutaneous nephrolithotomy; Biological model; Triangulation; Radical; Eye of the needle; PCNL, percutaneous nephrolithotomy; EM, eye of the needle (technique)

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