Use of three-dimensional animation for regional anaesthesia teaching: application to interscalene brachial plexus blockade{dagger}

M. W. Lim*, G. Burt and S. V. Rutter

Nuffield Department of Anaesthetics, John Radcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU, UK

* Corresponding author. E-mail: michael.lim{at}ntlworld.com

Accepted for publication October 22, 2004.


    Abstract
 Top
 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background. Using commercial computer graphics software (TrueSpace), we constructed a virtual-reality model for teaching interscalene brachial plexus block. This tool combines the clarity of schematic drawings and the clinical relevance of video clips and live demonstrations. The aim is to accelerate learning and aid retention of relevant information.

Method. We made a series of continuous short virtual-reality animations demonstrating the steps to perform an interscalene block. Superficial structures were made transparent to show the anatomical relevance of landmarking and needle manipulation. The clips were presented to delegates at a training course in Oxford. Delegates were surveyed to ascertain whether or not the presentation enhanced their understanding of anatomy and regional block technique. Before and after the presentation, delegates indicated surface landmarking, needle angulation, and movement on photographs of the lateral and anterolateral neck views of two volunteers. The markings were analysed by two independent assessors and rated as ‘good’, ‘bad’, or ‘ungradeable’. The percentage improvement for each skill group was calculated and McNemar's test applied.

Results. Of 24 respondents, the majority thought that the presentation enhanced their understanding of the anatomical (87.5%) and technical principles (79.2%) of interscalene blocks. Analysis of the marked photographs showed an overall 24.1% improvement in landmarking skills after the teaching presentation (P<0.001). Changes were significant in moderately experienced skill groups (P<0.001) but not for the very experienced (P>0.5) and the inexperienced skill groups (P<0.1). There was 76.3% concordance in scoring between the two assessors.

Conclusion. Three-dimensional animation is a promising new tool to accelerate the learning of regional anaesthetic techniques.

Keywords: anaesthetic techniques, regional ; computers ; teaching


    Introduction
 Top
 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Regional anaesthesia is a major component of modern anaesthetic practice. Regional anaesthesia requires clinical skills of patient positioning, surface marking, and needle manipulation.

However, the acquisition of these skills and background knowledge may be detrimentally affected by decreasing training opportunities (as a result of decreasing clinical time) and unpredictable intervals between suitable patients leading to failure of reinforcement. These problems are especially relevant to interscalene brachial plexus block, as it is indicated only for a limited number of operations (that is, shoulder and upper arm procedures).

Currently, the methods for teaching regional anaesthetic techniques include two-dimensional drawings, cadaveric teaching, videos, and live demonstrations. While no method can fully replace apprenticeship training on real patients, they each have their advantages and disadvantages. Two-dimensional drawings have clarity at the expense of detail; cadaveric models demonstrate anatomical relationships but cadavers are of limited availability, and the dissected tissues are displaced from their normal positions; video demonstrations show the clinical performance of regional anaesthetic techniques but require the audience to imagine underlying structures.

We have developed a three-dimensional (3D) model that combines the strength of each of these methods and tested on a cohort of attendees at a Regional Anaesthesia training course in Oxford.


    Methods
 Top
 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
We used TrueSpace 6, a 3D modelling program, to create a series of animation clips (Fig. 1). Each clip, lasting from 2 to 8 s, shows a discrete stage in the performance of the classical approach to interscalene brachial plexus block (as described by Winnie1). The stages are: adequate exposure and proper positioning of the neck, locating the cricoid cartilage, following the true horizontal plane from the cricoid cartilage posteriorly, locating the interscalene groove, inserting an electrostimulating regional block needle 30° caudally and 30° posteriorly to a depth of 1–2 cm, and observing for motor response below the level of the acromion process.



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Fig 1 Using 3D graphics, we created animation clips, which were able to expose anatomical structures to show the anatomical basis for surface marking. In addition, we could demonstrate the classical approach and common mistakes that deviate from this approach, thus teaching by contrast.

 
The classical approach was chosen because it is a simple technique and the approach is associated with the fewest complications.2

By moving the virtual camera around a virtual-reality neck model in the C6 transverse plane, we were able to choose optimal views to demonstrate surface landmarking and needle direction and movement. By making the superficial structures transparent or translucent (Fig. 1), we were able to show the underlying structures, demonstrating the anatomical basis behind interscalene block and important complications. We could also show incorrect techniques and their consequences. Our virtual-reality neck model was drawn schematically, showing only relevant vital structures.

Left-clicking on PowerPoint animations paused and restarted the animation, allowing us to focus on the most important aspects.

Each clip was made contiguous with the previous clip, allowing viewers to maintain both continuity of perception as well as the illusion of 3D movement. At various milestones, recapitulation and integration of what had so far been taught aided viewers to assemble the information into a consistent whole.

The clips were organized into a 20-min PowerPoint presentation, which was presented at the inaugural Oxford Upper Limbs Block Training Day. Delegates were surveyed before and after the presentation. The survey consisted of a questionnaire and photosurvey.

In the questionnaire, we asked delegates to self-assess their skill with the question: ‘How would you assess your competence in performing interscalene block?’. The response options were: ‘competent when unsupervised’, ‘performed unsupervised’, ‘performed supervised’, ‘observed but never done myself’ and ‘never seen one’.

After the presentation, delegates were asked: ‘did the presentation help you understand the anatomical principles behind interscalene block?’ and ‘Did the presentation help you understand needle direction and movements while performing interscalene block?’. The response options to each question were: ‘yes’, ‘no’, ‘not sure’.

The photosurvey consisted of two identical photosets, one for ‘before’ and the other for ‘after’ our presentation. Each photoset had four photographs. Two photographs showed the right lateral view of two volunteers with different body habitus and the other two showed the anterolateral view of the same volunteers (Fig. 2).



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Fig 2 This group of four photographs shows the lateral and anterolateral aspects of the necks of two volunteers. Respondents marked with a cross on the lateral photographs to indicate surface marking for interscalene block, giving horizontal and vertical scorings. Respondents marked with an arrow on the anterolateral photographs to indicate needle angulation and indicated on the numerical scale provided for needle depth, giving another two scorings. These four photographs were duplicated so that we could assess markings for changes ‘before’ and ‘after’ presentation.

 
Delegates were asked to mark with a cross on the lateral views where they thought the needle should be inserted for an interscalene block. They were also asked to mark with a circle and arrow on the anterolateral views to indicate needle direction and needle depth. A numerical scale was provided as another method to indicate needle depth. A PowerPoint slide showing the photographs was displayed at the same time for reference.

Two assessors analysed the markings on photographs. These were a consultant anaesthetist and a senior trainee with interscalene block experience. We categorically scored surface landmarkings along two directions (horizontal and vertical): ‘good’, ‘unmarked’, ‘forward’, ‘backward’, ‘high’, or ‘low’. We scored needle angulation as ‘good’, ‘unmarked’, ‘shallow’, or ‘steep’, and needle depth as ‘good’, ‘unmarked’, ‘deep’, or ‘shallow’.

We compared markings for each delegate ‘before’ and ‘after’ the 3D teaching for changes. The changes were then tested for statistical significance using McNemar's test (related nominal samples). As McNemar's test is designed for each participant acting as his/her own control, we discarded paired scores where either the ‘before’ or ‘after’ scores were ungradeable. We adopted the null hypothesis that there was no improvement in markings after our teaching. The alternative hypothesis that there was improvement, was accepted at P<0.01. This P-value was chosen because our study cohort was stratified into five independent skill groups (skill groups A to E).


    Results
 Top
 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Out of 24 respondents, two described themselves as ‘competent when unsupervised’ (skill group A), 11 as ‘performed unsupervised’ (skill group B), five as ‘performed supervised’ (skill group C), three as ‘observed but never done’ (skill group D), and one as ‘never seen one’ (skill group E). Two did not respond (‘did not respond’ group).

The great majority of respondents to the multiple-choice questions thought that the presentation enhanced their understanding of the anatomical (87.5%) and technical principles (79.2%) of interscalene block (Table 1).


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Table 1 Multiple-choice responses to our two header questions. Question 1 was: ‘did the presentation help you understand the anatomical principles behind interscalene block?’ Question 2 was: ‘did the presentation help you understand needle direction and movements while performing interscalene block?’ The options were: ‘yes’, ‘no’, or ‘not sure’. Invalid replies include no response or multiple responses. Skill group A described themselves as ‘competent when unsupervised’, B as ‘performed (interscalene block) unsupervised’, C as ‘performed (interscalene block) supervised’, D as ‘seen but never done one before’, and E as ‘never seen one before’

 
There was one ‘not sure’ response to question 1 and two ‘not sure’ responses to question 2. The delegate who had never seen or done an interscalene block before (skill group E) answered ‘not sure’ to question 2. The remaining ‘not sure’ responses came from a delegate who had ‘performed (interscalene blocks) unsupervised’ (skill group B).

Each respondent had eight (four ‘before’ and four ‘after’) photographs to mark, with each photograph giving two items of information. For 24 respondents, this gave a total of 384 possible markings. Two assessors could therefore make a maximum of 768 scorings.

Of these, 159 (20.7%) were ungradeable, either because respondents did not mark on the photographs or the assessors deemed the markings undecipherable. The proportion of ungradeable markings was largest in those for needle depth and needle angulation. The proportion also increased in the ‘after teaching’ group, mainly because of an increase in delegates failing to mark on these photographs.

Visual analysis of respondents' decipherable markings on the photographs (Table 2) showed a 24.1% improvement in markings after teaching, with between 18 and 38% improvement in the various marking categories. Breakdown of results by self-described competency showed that most skill groups improved on their markings after teaching. However, the most experienced skill group ‘competent when unsupervised’, did worse.


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Table 2 Visual analysis: assessments of photograph markings by both assessors with the ungradeable scores disregarded. The invalid results for group E were a result of the absence of markings. Skill group A described themselves as ‘competent when unsupervised’, B as ‘performed (interscalene block) unsupervised’, C as ‘performed (interscalene block) supervised’, D as ‘seen but never done one before’ and E as ‘never seen one before’

 
There was statistical significance in the improvement of landmarkings in skill groups B, C, and D, as well as on overall scores (Table 3). There was no statistical significance in the deterioration and improvement of landmarkings of skill groups A and E, respectively.


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Table 3 Visual analysis: McNemar's test applied to data and results categorized according to self-described proficiency.

 
Table 4 shows assessor differences in scoring respondents' drawings. Out of 384 paired scorings, there is concordance on 293 (76.3%), with divergence on 91 (23.7%).


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Table 4 Assessor differences: concordance in scoring is shown by the diagonal line of greyed cells. Out of 384 possible scores per assessor, 293 or 76.3% scores accorded with the other assessor's.

 

    Discussion
 Top
 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Three-dimensional graphics
The rapid advance in 3D computer graphics technology, and their accessibility in the form of recent affordable software, gives opportunity to use virtual-reality animations as a teaching tool. Virtual-reality is able to convey information not normally conveyed by other teaching methods3 4 and is becoming an important part of medical education.5 Although most studies on the effectiveness of virtual-reality were favourable,5 it might not be suitable for all types of training.6 7 In this study, we investigated the effectiveness of virtual-reality in regional anaesthetic teaching.

Many virtual-reality teaching methods are interactive. This may be more appropriate to advanced trainees, allowing them to make and learn from their mistakes on the screen instead of on the patient. However, less advanced trainees would probably benefit more from didactic teaching. Therefore, we chose a less interactive approach involving virtual-reality animations.

The flexibility of virtual-reality technology is a critical advantage over other teaching methods. In the animations, we can dynamically change views, choose an appropriate level of detail, transform structures to better demonstrate spatial relationships, and demonstrate both correct and incorrect techniques. No other teaching method can combine these advantages.4

The disadvantage of 3D teaching is in their preparation. Software programs need to be purchased and techniques learnt. It takes time to build the models and even more time to render the clips (our model required an average of 2 h computer time on an Athlon 1800+ MHz machine to render 2 s of video). Often, minor errors are not evident until the clips are rendered, requiring additional cycles of preparation, rendering, and viewing.

Part-whole training
We designed the clips as an accelerated form of combined part-whole task training.8 9 This approach states that complex skills are easier to learn when broken down into a series of simpler skills. The trainee then concentrates on learning the simpler skills, one at a time, using reinforcement through repetition. Integral to learning, is learning around each simpler skill, for example, relative anatomy. At appropriate intervals, the trainee assembles what he/she has learnt so far, into a more complex procedure until, finally, the complex skill is learnt in its entirety.

In keeping with this concept, our teaching was broken down into stages, each showing a discrete step. At each stage, the approved technique and common errors that deviate from it were demonstrated, teaching by contrast. This was reinforced using translucency and camera movement to demonstrate anatomy and consequences.

Reinforcement by repetition was not applicable in our setting. These need other media. We therefore distributed handouts summarizing the salient points of our teaching. We also created animation clips with suitable resolutions for Internet learning and handheld computers. These clips are available on the Regional Anaesthetic web page of our departmental website (www.nda.ox.ac.uk) and are meant for unsupervised reinforcement.

Errors
Assessment using multiple-choice questions provides unambiguous raw data. However, this was based on respondents' self-perceptions and therefore might not be objective.

Visual analysis of respondents' markings on photographs provides a mechanism for external assessment. By allowing free markings on reproduced photographs, it was also potentially richer in information obtained.

However, the accuracy of visual analysis was confounded by methodological, respondent and assessor errors. Methodological errors included difficulty conveying 3D information, such as needle angulation, using two-dimensional markings on reproduced photographs. Respondent errors included the non-uniform interpretation of instructions by respondents and the number of undecipherable or non-responses. Assessor errors resulted in differences in assessor scorings. Some of these errors are unavoidable but others are avoidable.

Methodological errors were largely unavoidable. However, we could have used better quality photographic reproductions.

Respondent errors were reduced by using similar photosets for ‘before’ and ‘after’. Thus, we could assess, not only the absolute positions of the markings, but also the relative change. This allows use of respondent markings as their own control.

Respondent errors might be further reduced by, first, showing delegates visual examples of how we wanted them to mark the photographs and, secondly, checking the survey forms before accepting them. These measures needed to be balanced against the possibility of confounding the study with prior information, the need for increased manpower and organization, and interrupting the flow of scheduled courses. We decided in favour of simplicity.

Assessor errors might be reduced by first, ‘training’ or ‘coaching’ assessors and secondly, by using multiple assessors. We had two assessors who practise the same classical approach. Despite having no previous coaching or training, there was concordance on 76.3% of scores, which we deemed satisfactory.

Finally, both questionnaire and photosurvey results corroborate each other, down to the benefit on individual skill groups (see next section), validating our decision choices in this study.

Effectiveness of virtual-reality teaching
We did not set out to compare the effectiveness of virtual-reality animation clips against other more traditional modes of education. However, a video clip of a clinical interscalene block was shown before our virtual-reality presentation. Moreover, in a hand poll, most of our survey population indicated knowledge of interscalene block from traditional teaching methods. The scores before our teaching could therefore be considered the result of traditional teaching modes.

The multiple-choice responses strongly suggested that 3D animations were effective to teach regional anaesthetic blocks for the majority of delegates. Visual analysis indicates that there was improvement in all skill groups except the most experienced group A. Changes were significant for skill groups B through to D, which were trainees with little to moderate experience.

The level of improvement did not reach statistical significance for trainees who had never even seen an interscalene block before (skill group E). This was a reflection of the small numbers (n=1). However, this delegate's response to question 2 indicated that this could also reflect the trainee's lack of practical experience preventing him/her from benefiting fully from our 3D teaching.

3D animations were not shown to help very experienced trainees (skill group A). This could reflect difficulty in changing from a familiar technique. However, the number within this group (n=2) was too small for accurate interpretations (P>0.5).

Therefore, both questionnaire and photosurvey results corroborated each other in most skill groups (B, C, D, and E) in that trainees need at least some practical experience to benefit from 3D animation learning. We could not however, draw any inferences about the most experienced skill group (A), although informal feedback from experienced consultants was favourable.

Restructuring training
We believe that 3D animation clips are effective for interscalene block teaching because the methods fit the subject. Thus, 3D visualization and part-task sequencing suits the anatomical nature and the related sequential sub-task procedure of interscalene blocks respectively.

We suggest that interscalene block training should be restructured. There should be an initial observation phase, followed by 3D animation tutorials. During the tutorials, trainees would also be taught how to assess intranet resources for unsupervised reminder/reinforcement training. Trainees would then be supervised for interscalene blocks until such time as they and their supervisors are confident they are ready to progress to unsupervised blocks.

We anticipate that with this approach, the time to unsupervised interscalene blocks would decrease, and it would be easier to maintain skills and confidence. This is the next step to be demonstrated, using traditional teaching methods as study controls.

Because of the similar anatomical and sequential nature of most, if not all, regional anaesthetic block techniques, we are confident that the principles we have developed are also applicable to other regional anaesthetic techniques.

Conclusion
3D animation is a promising teaching tool for regional anaesthetic techniques and is well-received by both trainees and trainers. However, in our study, it was only shown to be effective for trainees with some (little to moderate) practical experience. More research is needed to further elaborate this method's strengths and how best to use it.


    Acknowledgments
 
We would like to thank Professor John Sear, Professor of Anaesthetics, Nuffield Department of Anaesthetics, Oxford and Dr Alan Loach, Consultant Anaesthetist, Nuffield Department of Anaesthetics, Oxford, for their help in reviewing our paper and presentation respectively. We would also like to thank ODP Celia Day for her assistance with the photography. Dr Lim is supported by a research fellowship funded by the British Journal of Anaesthesia and the Royal College of Anaesthetists.


    Footnotes
 Top
 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
{dagger} This paper has been presented at the 13th World Congress of Anaesthesiologists, Paris, April 2004. The abstract is published in the accompanying CD-ROM under reference S028. This paper has also been presented at the Society of Computing and Technology in Anaesthesia Winter Meeting, Manchester, November 2003 and at the National Anaesthetic Research Meeting, Penrith, June 2004. Back


    References
 Top
 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Winnie AP. Interscalene brachial plexus block. Anesth Analg 1970; 49: 455–66[Medline]

2 Evolution of the interscalene brachial plexus block. www.anesth.uiowa.edu/boezaart/evolutionisb.pdf.

3 Dolata DP, Wathen SP. The use of VRML in chemical education. J Mol Graph Model 1998; 16: 37–46[ISI][Medline]

4 Friedl R, Preisack MB, Klas W, et al. Virtual reality and 3D visualizations in heart surgery education. Heart Surg Forum 2002; 5: E17–21[Medline]

5 Letterie GS. Medical education as a science: the quality of evidence for computer-assisted instruction. Am J Obstet Gynecol 2003; 188: 849–53[CrossRef][ISI][Medline]

6 Engum SA, Jeffries P, Fisher L. Intravenous catheter training system: computer-based education versus traditional learning methods. Am J Surg 2003; 186: 67–74[CrossRef][ISI][Medline]

7 Gerson LB, Van Dam J. A prospective randomized trial comparing a virtual reality simulator to bedside teaching for training in sigmoidoscopy. Endoscopy 2003; 35: 569–75[CrossRef][ISI][Medline]

8 Stammers RB. Part and whole practice in training for procedural tasks. Hum Learn 1982; 1: 185–207[ISI]

9 Park JH, Wilde H, Shea CH. Part-whole practice of movement sequences. J Mot Behav 2004; 36: 51–61[ISI][Medline]





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