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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 70  |  Issue : 3  |  Page : 140-145

Wax versus plastinated models in teaching human anatomy to health-care professionals. A randomized crossover trial


Department of Neurosciences, Institute of Human Anatomy, University of Padova, Padova, Italy

Date of Submission31-Jan-2020
Date of Acceptance07-Jul-2021
Date of Web Publication23-Sep-2021

Correspondence Address:
Prof. Veronica Macchi
Department of Neurosciences, Institute of Human Anatomy, University of Padova, Via A. Gabelli 65, Padova 35127
Italy
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JASI.JASI_17_20

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  Abstract 


Introduction: Teaching anatomy moved from teacher-centered to student-centered learning. Three-dimensional models help to improve self-learning of basic concepts other than anatomical spatial relationships. Wax and plastinated models were compared for appropriateness and safety in teaching human anatomy to health-care professionals. Material and Methods: Randomized crossover trial. The CONSORT checklist for randomized crossover trials was followed. Eighteen volunteer physiotherapy students at the University of Padova were randomized into two crossing-over groups applying to wax and plastinated heart models. Final Likert survey scales were administered. Results: They reported that the wax models presented a more pleasant smell, a better chromatic appearance, and superior ease of handling than plastinated models, with a higher degree of perceived biological safety. Wax models were judged less suitable for educational use and for clarifying anatomical doubts, both in assessing external and internal anatomical details. Discussion and Conclusion: Overall, the plastinated models were considered more suitable for educational use in teaching internal and external anatomical details. The wax models showed a better appearance, ease of handling, and a minor perceived biological hazard.

Keywords: Ceroplastic, health-care professionals, plastinated model, randomized crossover trial, wax model


How to cite this article:
Boscolo-Berto R, Tortorella C, Macchi V, Porzionato A, De Caro R. Wax versus plastinated models in teaching human anatomy to health-care professionals. A randomized crossover trial. J Anat Soc India 2021;70:140-5

How to cite this URL:
Boscolo-Berto R, Tortorella C, Macchi V, Porzionato A, De Caro R. Wax versus plastinated models in teaching human anatomy to health-care professionals. A randomized crossover trial. J Anat Soc India [serial online] 2021 [cited 2021 Dec 3];70:140-5. Available from: https://www.jasi.org.in/text.asp?2021/70/3/140/326425




  Introduction Top


Historically, the dissection of human bodies has been the most relevant teaching paradigm for gross anatomy learning since the late 16th century. A body donation program was implemented at the Institute of Human Anatomy of the University of Padova to make health-care professionals specifically, anatomy education and research activities on real human models.[1] However, the exponential growth of interest in anatomical education on cadavers by students and postgraduates, jointly with the increase of class sizes, makes the number of available bodies insufficient to meet current needs fully.

The paradigm shift has moved from passive and teacher-centered learning toward active and student-centered learning by integrating supplementary multimodal teaching resources.[2] Interactive three-dimensional models may improve the long-lasting retaining of anatomical details and understand their spatial arrangement and neighborhood relationships. Indeed, they are increasingly required by health-care students, with a favorable impact on student's perception and learning.[2],[3],[4] Among the tools traditionally used for this purpose, there are both wax and plastinated models.[5],[6],[7],[8] They are widely used for didactical purposes, attempting to reproduce and clarify the human body's three-dimensional organization and complexity. They recall the actions and results of an anatomic dissection as performed by an anatomist, being a potential option to reproduce and manipulate specimens as close as possible to reality.[9]

Mainly, anatomical wax modeling (also named ceroplastics or less frequently moulage) referred to a traditional technique involving wax obtained by bees or other animals/vegetable sources to manufacture high-quality artworks colored so realistic that they resemble almost lifelike.[7],[10] They require unique expertise and are time- and money-consuming.[11]

On the other hand, anatomical plastination was introduced in the late 1970s using silicone rubber, polyester, or epoxy resin to produce treated specimens of high durability that are extensively used in anatomical research and medical teaching.[12],[13] However, one negative point is the complexity of the operations necessary for the production of the models, resulting in an articulate and expensive process with low chromatic credibility.[5]

The present study compared three-dimensional wax versus plastinated models to investigate their impact on practical experience. Mainly, it explores which one is perceived as more useful, safe, and appropriate for the study of basic human anatomy in a university course devoted to health professionals such as physiotherapists.


  Material and Methods Top


A single-day crossing-over trial was implemented to test the hypothesis and compare the usefulness/appropriateness of wax and plastinated anatomical models in teaching anatomy [Figure 1]. The CONSORT checklist for randomized crossover trials was followed [Supplementary File 1].
Figure 1: Experimental design

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Outcomes

The following outcomes were investigated: perceived biological hazard, perception of internal and external anatomical configuration, color and smell, usefulness in clarifying anatomical doubts they had, and overall appropriateness in teaching anatomy.

Selection and description of participants, randomization to groups and variables.

One author (BBR) enrolled participants, managed the allocation, and assigned participants to the interventions sequence.

All the first-year students attending the mandatory course in general macroscopic anatomy in the first semester of the 3-year cycle degree course of physiotherapy at the University of Padova were considered eligible. As the number of potential applications was less than the number of available positions, a selection test was not carried out. Moreover, as the trial had a limited number of students available, the preliminary calculation of the sample size was not carried out. All physiotherapy students were unpaid volunteers.

Student's data, i.e. “gender,” “age,” and “scoring arithmetic mean for passed examinations,” were collected.

They were subsequently randomized by simple allocation to a first group, which applied for up to 10 min to a wax anatomical model, and a second one applied for up to 10 minutes to a plastinated anatomical model (first step). Randomization was performed on the random-order-of-service basis, and the allocation ratio was 1:1. This way, whenever the two anatomical models became free, the next student was chosen randomly from the queue, each participant being equally likely to be selected. After the first step, the groups reversed without any washout period, applying to the type of anatomical model they had not yet used, according to a crossing-over experimental design [Figure 1]. As no information was required to be retained between steps, we excluded a carryover effect. Moreover, blinding was prevented by the type of experiment.

Wax and plastinated models

We chose to focalize the experiment on human hearts due to practical and logistic convenience. Physiotherapy students were given a whole and dissected human hearts both as wax (n = 2) and plastinated (n = 2) models [Figure 2]. The two models were considered substantially suitable in size, integrity, correspondence to anatomical reality, and potential teaching usefulness. As the models were human hearts, treated or reproduced, a certain similarity of the experimental interventions was implicit.
Figure 2: Wax and plastinated models. (a) Plastinated model (heart whole). (b) Plastinated model (heart opened). (c) Wax model (heart whole). (d) Wax model (heart opened)

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The plastinated models were taken from two adult males included in the Body Donation Program of the University of Padova.[14] The Regional Bioethics Committee approved the study for exemption from the formal review as part of the Body Donation Program of the University of Padova. The scientific coordinator of the donation program supervised the study.

The wax models were taken from the historical collection of the Institute of Human Anatomy - University of Padova, dating back to the early 20th century.

Test

After the manual examination of the wax and plastinated models, participants were asked to fill an anonymized questionnaire. It consisted of ten questions focused on the following: adequacy of the time given to complete the task, evaluation of the models on perceived biological hazard, internal and external anatomical configuration, color and smell, usefulness in clarifying anatomical doubts they had, and their appropriateness in teaching anatomy.

The available answers were arranged according to the five levels of a standard Likert survey scale (strongly disagree [1 point], disagree [2 points], undecided [3 points], Agree [4 points], and strongly agree [5 points]).

The questions were reduced to prevent the tendency to respond in a specific direction to a series of items, regardless of the differences in item content (“response set bias”). It could be partially due to the high number of questions administered, hence reducing the questionnaire length provide some protection. A particular type of response set bias is called “acquiescence response set, “ which is the tendency of participants to agree rather than disagree on a whole series of items. Half of the questions were reported using the reverse wording (and scoring) of the issues and encouraging participants to carefully read each question. Consequently, the results were reported in the adjusted form in light of the reversal wording introduced.

Statistical analysis

The parametric nature of studied variables was assessed using central tendency measures, measures of variability, and measures of shape, and confirmed by performing of Shapiro–Wilk test. Consequently, parametric variables were described as mean ± standard deviation, with an additional overall range of values provided as necessary. Accordingly, the comparisons were performed by using the Student's t-test. A two-sided p < 0.05 was chosen to indicate statistical significance in all the analyses.


  Results Top


A total of 18 out of 25 first-year physiotherapy students were recruited. Seven refused due to overwhelming personal commitments. Enrolled participants were 13 males and five females. The mean age of participants was 20.8 ± 0.4 years, ranging from 20.1 to 21.2 years [Table 1]. The rate of completed tests was 100% (18/18).
Table 1: Descriptive statistics

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Students preliminarily confirmed that the time slot assigned for the evaluation of the models (10 minutes) was sufficient, both for wax models (Likert scale (LS): 4.0 ± 0.9 points; 5.7 ± 1.7 min) and for plastinated models (LS: 3.9 ± 1.0 points; 7.4 ± 2.1 minutes), with a significant statistical difference (p = 0.043).

From a merely didactical point of view, wax models were overall judged less suitable for educational use (LS: 2.9 ± 1.0 points), with a worse performance in assessing both external (LS: 2.6 ± 1.3 points) and internal (LS: 2.6 ± 1.3 points) anatomical configuration compared to plastinated models. Moreover, wax models were judged less suitable to clarifying anatomical doubts (LS: 2.2 ± 1.1 points).

Moreover, wax models showed superior ease of handling than plastinated models (LS: 3.4 ± 1.5 points) with a higher degree of perceived biological safety (LS: 3.4 ± 1.0 points). The wax models presented a more pleasant smell than plastinated models (LS: 3.8 ± 1.1 points), with a better chromatic appearance (LS: 3.1 ± 1.4 points) [Figure 3].
Figure 3: Likert survey scale. Numbers on the X-axis are referred to as percentages of provided answers

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  Discussion Top


A solid understanding of gross human anatomy is recognized as a fundamental premise of any academic curriculum involving health-care professionals.[1],[15]

The School of Medicine at the University of Padova provides with the 3-year cycle degree course of physiotherapy the teaching of human anatomy. The lessons are scheduled in the first-semester/first-year course, including frontal lectures and exercises of direct dissection in small groups on fresh frozen bodies, as available. Wax and plastinated models are also used. However, increasing student enrolments jointly to simultaneous inadequacy of the numbers of cadavers has made it more difficult for health-care students to access and dissect cadavers.[2],[4]

On the other hand, physical anatomical models offer a useful tool for teaching gross anatomy in three-dimensional representation due to their easy accessibility, low cost, and educational effectiveness.[16]

In this scenario, wax and plastinated models are considered superior to synthetic models, as they may reflect anatomical variations.[13],[17]

However, while the plastinated models are still widely used, the wax models are not, even if their reintroduction is supported by some authors.[8],[18] In the past, three-dimensional wax tools adhered to the ideals of immediacy and practicality of medical knowledge, which became central during the 18th and 19th centuries, with medical disciplines based on the morphological substrate of diseases.[10],[19] Thanks to the three dimensionality and chromaticism of the waxworks, physicians and medical students could appreciate vivid and realistic representations of many organic diseases typical of that time, mediating sophisticated medical knowledge with immediacy.[10],[19] On this point, physiotherapy students confirmed in the final test the better chromatic appearance of wax models compared to plastinated models, conferring an artistic experience to the manipulation of the analyzed samples. Indeed, in the past, a large number of collections have arisen in several countries, some with an exquisitely anatomical vocation such as Padua, Bologna, Florence, Paris, Athens, and Zurich, and others with a shared interest in forensic medicine such as Parma, Halle, Berlin, and Wien.[11]

On the other hand, anatomical plastination was introduced in the second half of the 20th century to produce treated specimens of high durability in anatomical research and medical teaching.[12],[13]

Wax was highly appreciated for its pliability, elasticity, and workability, allowing the creation of various delicate models not obtainable with clay, which must be worked while wet and present weak tensile strength.[9] On the other hand, plastination can provide for whole organ preservation and body slices without artifacts, with several techniques including the most recent evolutions, such as the light plastination.[20] It can be carried out using low-cost equipment readily available in most anatomy departments,[21],[22] allowing for prosections lasting for a long time after their production, performed once every many years.[22],[23]

In the present article, the final test revealed that wax models showed superior ease of handling than plastinated models, probably due to their nondeformability to manual exploration and their constitution in a single piece of wax. It is coherent with the literature, which reported that wax models are more rigid than plastinated and do not allow the mechanical features of joints or the full demonstration of hidden structures.[17]

Overall, plastinated models were deemed useful by students and accommodated needs at various levels,[22],[23],[24] including residents and surgeons,[17] other than anatomists.[13],[25] Moreover, plastination can preserve delicate structures and their interconnections, enabling them to be traced microscopically.[25] Regarding safety, both wax and plastinated models do not present an actual biological risk for which specific protections must be adopted.[17],[22],[23] However, physiotherapy students perceived a higher degree of biological safety in handling wax models, perhaps because plastinated models, although treated, derive from human bodies. Overall, plastination can provide a supplementary method to show odorless anatomical structures and variants, allowing easy storage and handling.[23],[24],[25] The test participants reported that wax models presented a more pleasant smell than plastinated models, although they did not give off particularly unpleasant odors.

Nowadays, the production of wax anatomical models is minimal, and most of the circulating was produced decades ago. The reasons for this decline are to be found in the evolution that has affected the biological investigations. At the beginning of the 19th century, the physiological and histological sciences were born, indicating that medicine was already directed toward the anatomo-clinical approach, further developed in the following decades with the introduction of histopathology, cell pathology, and radiology.[9],[19]

In this scenario, the gross anatomic institutions have taken a back seat in scientific research for many decades, although they continued to be active and still considered the mainstay of medical education. Moreover, the prohibitive costs related to the type of processing and the time required have made the wax models the almost exclusive prerogative of the institutions with the most significant funds available. Furthermore, historically, the major boost to wax models was the lack of valid methods for preserving bodies, so the dissections were concentrated in the winter season and over a few days.[11] With the development of more modern fixation techniques in the second half of the 19th century (i.e., formalin instead of alcoholic solutions), demonstrative dissections became more feasible. The treated samples could last for weeks, by the use of much cheaper and faster processes than the productions of wax models, which lost much of their teaching appeal.[9] The wax models kept a role in the reproduction of rare diseases for a longer time so that students had an always-available reference to recognize unfrequent diseases. Dedicated series of wax models were produced for several medical disciplines, aimed to show mainly the pathological modifications of the organs induced by the diseases studied and treated by the specialists.[10],[19] Overall, wax models in modern medical education seemed to be still of interest for learning on diseases, being integrated with other teaching tools to improve diagnostic skills.[7],[11] At the same time, this is valid for studying normal surface anatomy, enabling learners to improve visualization of structures, especially those of the musculoskeletal system, hence contributing to a better anatomical learning experience by familiarising with surface landmarks.[15],[26]

Physiotherapy students here reported that, from a merely didactical point of view, wax models were overall less suitable for educational use compared to plastinated models, with a worse performance in assessing both external and internal anatomical details. In this view, wax models were judged less suitable to clarify anatomical doubts than plastinated ones.

Indeed, for health-care students who are not provided with the opportunity to dissect human bodies, plastinated specimens might represent a valid alternative.[27] Although three-dimensional models cannot replace traditional anatomic dissection in every circumstance, the anatomical section of fresh frozen bodies probably is beyond the scope for physiotherapy students.[17],[18],[22]

Wax models are artistic works of great value that should still find a prominent place in the diagnostic teaching of even unusual pathological cases, while plastinated models can be more useful in daily teaching of anatomy to students needing basic notions.

The present study is affected by the following limitations.

First, the study population was restricted to first-year physiotherapy students. Whether these findings could be generalized to more senior ones needs to be determined. In the same way, external validity should be tested.

Second, students were not tested for their spatial ability, i.e. the aptitude for understanding three-dimensional structure, which could interfere with the spatial evaluation apart from the type of educational materials involved.[28]

Third, participation in the trial was voluntary, potentially leading to biases in various directions concerning which students chose to attend the present experiment.

Fourth, just heart models were used in this trial. The inference of these results to other anatomical regions is to be verified.

Finally, the current results arise from a single-center study. The sample size is limited because the degree course of physiotherapy includes few students. Moreover, their attendance in the classrooms or handling of anatomical material was restricted due to the COVID pandemic.


  Conclusion Top


Wax and plastinated models are significant educational, research, and cultural tools in the medical world to integrate teaching and learning anatomy in conjunction with traditional gross dissection, which remains the milestone reference. They could help maximize the impact of practical experience and overcome the contraction of economic resources and the shortage of available bodies.

Despite wax models showing a better chromatic appearance, superior ease of handling, and a minor perceived biological hazard against the plastinated models, the latter were judged more suitable for educational use in teaching internal and external anatomical details.

Nevertheless, further studies are needed to validate these findings, to expand the trials to models of other anatomical districts, other than examining the long-term impacts on the learning process also for other health-care professionals.

Key findings:

  • Wax and plastinated models are still useful educational, research, and cultural tools.
  • They could be of help in maximizing the impact of practical experience.
  • Plastinated models were judged more suitable for educational use in teaching anatomy.


Acknowledgments

The authors wish to thank Gloria Sarasin for her administrative and technical support in scheduling the experimental activities and administering questionnaires to the students, and Aron Emmi for retrieving museum materials.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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