The role of three-dimensional printing models in medical education: a systematic review and meta-analysis of randomized controlled trials | BMC Medical Education

This study provides a systematic review and meta-analysis of the application of 3DPMs in medical student education, with the results showing that 3DPMs may promote the theoretical test performance and lab test performance of medical students with a moderate effect size. The results will provide theoretical basis, new ideas and directions for the application of 3DPMs in medical education, as well as directions for improvement for 3DP technology developers. However, due to the small number of studies included in quantitative analysis, their poor quality, and small sample size, caution should be exercised when interpreting the results.

The results of this study show that for theoretical performance, 3DPMs of the skeletal system can significantly improve learners’ theoretical performance; however, there was considerable variability in the results. The reasons considered are as follows: First, among the included studies, a notable degree of heterogeneity was observed among the subjects. Given that students at different academic levels possess distinct knowledge reserves, this variation inevitably gives rise to heterogeneity in the research outcomes. The differences in prior knowledge can significantly influence how students engage with the study materials and respond to the interventions, thereby affecting the comparability and generalizability of the results. Second, there were disparities in the 3DP materials and printing accuracy leading to variations in the realism and precision of the models. These factors, combined with the differences in the control groups, contribute to the heterogeneity of the statistical results. The lack of standardization in these aspects makes it challenging to draw consistent and reliable conclusions from the collective body of research. Finally, different studies adopted diverse outcome indicators to assess students’ academic performance. Some studies utilized multiple-choice questions, while others relied on single-choice questions or open-ended questions. Each type of assessment tool has its own strengths and limitations, and the choice of outcome indicator can significantly affect the measurement of students’ learning outcomes. This divergence in outcome indicators also results in heterogeneity in the research results, as different assessment methods may capture different aspects of students’ knowledge and skills.

Nevertheless, there is a lack of evidence indicating that cardiovascular, plastic, and dental 3DPMs significantly enhance learners’ academic performance. The reasons considered are as following: First, four studies used bone models with a total sample size of 646, while the above models were only used in one or two studies. Therefore, the small sample size may be the reason for the negative results. Second, structural complexity of different 3DPMs between studies may also lead to different results [60]. Prior research indicates that anatomical complexity can modify the effectiveness of educational tools on learning and performance outcomes [60,61,62]. In this study, the 3DPMs used were diverse and varied in their complexity (bone models, heart models, plastic surgery models and tooth models), which may also have led to inconsistent results. It was reported that 3DPMs of the upper and lower limbs did not significantly improve learners’ performance compared to the control group, while 3DPMs of the pelvis and spine significantly improved learners’ performance on theory tests [58]. Furthermore, Studies have shown that for medical students, the learning difficulty of normal human anatomy is much lower than the pathological state of clinical patients [15, 53, 58]. In the results of this quantitative analysis, only 8 studies used medical cases as the data source for 3DPMs, which may may have results in insufficient power of the results. Finally, the situation of different control groups may also lead to this result. As the previous research results show, there is no difference between 3DPMs and cadaveric skull models, 2D atlases or 2DIs, but there are obvious differences between 3DPMs and lectures. In the results of this quantitative analysis, the control intervention included cadaveric skull, the 2D atlases, CBL, Traditional radiographic image, PPT + 3DIs, plastinated specimens, traditional teaching, and PPT, which led to inconsistent results.

The results of this study show that 3DPMs may improve the lab test of medical undergraduates with moderate effect size, but there is no evidence that 3DPMs can significantly improve the total test. The inconsistency in results, as we considered, is related to the diversity of total scores and lab test assessment methods. In the studies that included quantitative analysis, the assessment methods of lab scores and total scores are diversified. In terms of the assessment of lab scores, they include marking bone marks, inlay preparations, and completing test items. In the evaluation of the total score, some studies add the theoretical scores and practical scores to get the total score, while some studies not only calculate the theoretical scores and practical scores but also include the learner’s satisfaction and the evaluation of the model into the total score. This may lead to the inconsistency of results due to the diversity of forms and contents of score evaluation, and also cause the inconsistency of total results and lab score. Combined with the results of meta-analysis, the P-value and SMD of the 3DPMs group were 0.20 and 0.26 respectively compared with the control group in terms of total scores. There is no evidence that the intervention group is actually better than the control group; therefore, this result needs to be treated with caution, and further research may be needed to confirm the stability and authenticity of this small effect size. For example, increasing the sample size, improving the study design, or conducting subgroup analyses could be done to more accurately assess the effect of the intervention.

The sensitivity analysis showed that after each study was sequentially deleted, there was no impact on the final results. Therefore, the heterogeneity between studies mainly arises from the subjects, intervention methods, controls, outcome indicators and other aspects. First of all, in the studies included in quantitative analysis, although all included medical students, there was obvious heterogeneity among the studies due to the differences in the knowledge reserve of included learners and the educational level in different regions. Secondly, the use of different 3DPMs in the intervention group, different 3D printing techniques and different resolutions also contributed to heterogeneity between studies. Moreover, the intervention methods of the control group were also diverse, such as 3DIs, 2DIs, and cadaver specimens, which also resulted in the existence of heterogeneity. Finally, the studies included in quantitative analysis also have different testing methods for outcomes. From the form of test questions, some only have single choice, while others include single choice, multiple choice, short answer and medical record analysis questions, which were also an important source of heterogeneity.

When using 3DPMs, the accuracy of data sources (such as resolution, layer thickness of CT or MRI images), printing materials, and whether there are clear marks will all affect the effect of 3DPMs on academic performance. In this study, the resolution and layer thickness of pictures are quite different, and the printing materials are also different. This results in less consistency between studies, which may affect the strength of the data results. Learners’ basic knowledge and early knowledge reserve will affect the teaching effect. In this study, only 5 studies took some measures to ensure a similar baseline level of knowledge on the subject [25, 31, 39, 42, 52], such as excluding subjects with scores greater than 50% through pre-test [52], only students with no prior knee-related anatomical knowledge at the time of recruitment were selected for the study [39].

Among the included studies, only seven studies had follow-up ranging from 5 days to three months [32, 34, 43, 45, 46, 50, 51]. The findings from these studies are inconsistent. Some studies suggest that 3DPMs enhances short-term learning outcomes compared to traditional teaching methods, although its long-term effects have yet to be confirmed [32, 43]. Conversely, other studies indicate that 3DPMs can improve both short- and long-term learning outcomes [46, 50]. Nonetheless, a consistent finding across these studies is that 3DPMs positively impacts learners’ cognitive anxiety and confidence in learning.

There are many confounding factors in the learning process, such as learning motivation, previous learning experience, curiosity about new things, etc. In one study, baseline data were collected on students’ previous exposure to 3DPMs and through the assessment of students’ spatial representation skills through a mental rotation test [50]. The influence of learners’ motivation on learning results should not be ignored. It is believed that students who can actively participate in this kind of research project have a relatively positive learning attitude, and when they are included in the research, they will cherish the learning opportunity [25, 48], which also affects the validity of the results. Besides, anatomical complexity may be a key confounder of learning and performance outcomes, as Wu’s research shows that no significant differences were found in the upper limb or lower limb test scores between the 3DPMs group and the traditional radiographic image group; however, the scores on the pelvis and spine test for the traditional radiographic image group were significantly lower than the those for the 3DPMs group [63].

In addition to improving the quality of teaching, we are also concerned about the cost of equipment, materials and time. In this study, only five studies reported the cost of materials and time, and no study reported the cost of equipment. In the studies included in this project, the processing time of 3DPMs was reported to be the as short as 4–5 h and as long as 3–7 days, while the material cost was the as lower as $14 and as high as $281.61. It was previously reported that the 3DPMs was not time-effective and the costs of specialized printing machine and the bioinks were still too high to be affordable, especially for the underdeveloped areas [64, 65]. This also limits the application of 3DPMs in medical education to a certain extent.

It should be emphasized that successful 3DPMs require careful design and conception, especially models that can be assembled or models that add biomechanical elements. Successful design comes from years of clinical work, the accumulation of teaching experience, as well as repeated speculation and reflection. At the same time, the successful production of the model also needs the assistance and guidance of professional and technical personnel. Therefore, we should make it clear that 3DPMs are only an auxiliary teaching means; Its successful application can significantly improve the teaching effect, but we cannot ignore the advantages of traditional teaching.

Strengths and limitations

This study was conducted in strict accordance with the guidelines to ensure the reliability of the results. Firstly, the retrieval strategy was adjusted several times by pre-inspection to ensure the comprehensiveness and accuracy of literature retrieval. Secondly, in the process of literature screening, quality assessment and data extraction, two researchers independently completed the process and consulted with the third experienced researcher to obtain a consensus result. Thirdly, in the process of data analysis, subgroup analysis, sensitivity analysis and other methods were used to explore the factors affecting the results and the sources of heterogeneity, so as to ensure the reliability and validity of the results.

In addition to the above advantages, there are still some problems that need our consideration in this study. First of all, although the subjects included in this study are all medical students, the differences in medical education mode, medical education level and curriculum in each country and region could have affected the stability, validation, and generalization of the final results. Secondly, the different 3DP equipment used in the study, the different materials, the different printing parts, and the different precision of the data images led to the great heterogeneity among the 3DPMs. Also, the printing model and image data did not include analysis of muscles and neurovascular tissue surrounding the model, without which the model cannot completely represent a pathological condition. The precision of 3DPMs will affect the learning effect of learners. In this study, only 2 studies evaluated 3DPMs, which might lead to the existence of heterogeneity. Thirdly, different control teaching methods, including 2DIs, 3DIs, 3D visualization, cadaver specimens, lectures, etc., also led to the existence of outcome heterogeneity. Moreover, although all the studies included in this study were randomized controlled studies, only two studies reported blind methods, and only 2 studies were multi-center studies, resulting in the included studies being mostly identified as high risk in the assessment of risk bias, which affected the reliability of the results. In addition, it should be noted that among the included literatures, only a small number of articles reported the data we desired for quantitative research. By contacting the original authors, we did not obtain all the data required for the quantitative analysis of this study. Therefore, the power of the results of this study needs to be further verified. Finally, it is imperative to emphasize that in the original studies included in this research, most of the outcome evaluation indicators are either self-reported or subjectively judged by the evaluators. The inconsistent cognitive differences and evaluation criteria among different individuals may also lead to some deviations in the results, thereby affecting the accurate assessment of the effects of 3DPMs.

Future research direction

In future research, when using the 3DPMs for medical education, we may pay attention to the following aspects. Firstly, in the practical application context, the time and material costs are the top concerns for medical educators. Nevertheless, only five out of the incorporated studies have addressed the time cost. Precisely, the time span required varies remarkably, stretching from a minimum of 4–6 h to a maximum of 30 h. According to one of the studies, commencing from the acquisition of CT or MRI scan data and concluding with the finalization of the 3DPM suitable for medical instruction, the entire processing pipeline generally demands 3 to 7 days. Regarding the material cost, four studies likewise furnished pertinent information. The expenditure on materials for 3DPMs lies within the interval of 10 to 20 euros or 14 to 281.61 US dollars. Notably, one study accentuated that while the direct material cost for model printing is relatively moderate, the financial outlay for procuring 3DP machines is considerably high, imposing an undeniable economic strain on medical education institutions intending to adopt this technology. Consequently, due to the cost of time and materials, future research can be optimized from the following aspects. On the one hand, the production process of 3DPMs dedicated to medical education can be deeply optimized to minimize the time spent in the process from medical image data extraction to model production, thereby effectively improving the efficiency of teaching preparation and ensuring that 3DPMs can serve medical teaching practice in a more time saving manner. Secondly, make every effort to explore the material replacement strategy that meets the needs of medical education and is more cost-effective. On the basis of fully guaranteeing the quality requirements such as the accuracy and fidelity of 3DPMs, effectively reduce the material procurement cost and the comprehensive cost of equipment acquisition and maintenance, and open up an economic and feasible way for the popularization of 3DP technology in medical education; Thirdly, systematically and deeply explore the impact of different time input and material cost input modes on the final teaching performance of 3DPMs in medical education scenarios, such as the effect of the model on assisting students to understand complex anatomical structures, improving practical operation skills, and actual teaching application effectiveness. Thus, it can provide an accurate and scientific cost–benefit reference basis for medical educators to make optimal decisions when using 3DPMs.

Develop and utilize materials that more closely mimic the mechanical properties of human tissues, such as elasticity, flexibility, and haptic feedback. These materials will make the models more realistic and enhance the learning experience. Explore the use of multi-material 3DP techniques to create models with varying properties, allowing for the representation of different tissues within a single model. The tactile and visual advantages provided by these models allow students to have physical access to anatomical structures, greatly improving their understanding of complex theoretical knowledge [19]. Future advances in implementing 3DP in medical education could include the development of printing devices that allow rapid onsite printing in the teaching hospital and the development of 3DPMs that mimic the haptic characteristics of specific tissue (i.e., nerves, arteries, muscles) [53] It was reported that sight and touch are linked in a cross-modal arrangement in the somatosensory cortices, suggesting that they are mutually enhancing [66],which can improve the learner’ performance scores. Furthermore, the integration of these haptic models into a progressive clinical curriculum is likely to enhance comprehension by contextualizing haptic-visual data and facilitating the precise exploration of specific competencies that students are expected to acquire, such as biomechanical concepts [54]. Designing models with interactive elements, such as removable parts or adjustable components, enables exploration and manipulation, thereby potentially increasing engagement and understanding of complex anatomical relationships. It is very important that when applying 3DPMs, their precision should be evaluated so as not to affect the learning performance of learners.

Case-based models such as fracture model, congenital malformation model, vascular disease model, especially for rarer and more complex situations, use cases as a basis and put empty theories into the context of specific cases for exposition. It has been reported that most cadaver specimens and plasticized models have normal anatomy and cannot be used for the study of pathological conditions; however, the use of 3DPMs offers the possibility of contextualizing the course by selecting the desired pathological structure [41]. 3DPMs can be obtained from interesting cases encountered in clinical practice, which can provide diverse pathological changes and strengthen the connection between learners’ basic knowledge and clinical practice [67].

This ensures that the models are tailored to the needs of the students and the curriculum. Students’ engagement and interest can be increased through the combination of visual and tactile use of 3DPMs and dynamic learning experience in the CBL teaching method. At the same time, instructors can introduce active learning and critical thinking into the traditional classroom, guiding students to analyse problems and explore solutions in a more holistic manner and improving overall teaching and learning outcomes [19, 31].

The confounding factors of learning effect cannot be ignored. In previous studies, students applied and were randomly selected for inclusion in the study. The selected students may cherish this opportunity very much and study hard. When students in the control group realized that they weren’t selected to use the 3DPMs, they were likely to work harder to get better scores [25, 48], which leads to a significant reduction in the difference between the two groups. Therefore, when evaluating the role and effect of 3DP in medical education, the influence of learning motivation on the outcome should be considered. Novel interventions usually arouse participants’ curiosity and lead to better results [68]. In addition, prior exposure to 3DP printing should be considered in the evaluation of medical education outcomes. In view of the impact of different cognitive loads and anatomical complexity on the teaching effect of 3D printing [61,62,63]. Future studies will work to identify the impact of 3DP on anatomy learning of a variety of anatomical regions in an effort to identify the ideal niche to maximize learning with 3D print exposure. Additionally, it was also important to note that 3DP involved complex processes and some structures may be lost during printing or post-printing procedures such as removing and cleaning the support materials. Hence, the structural variations and extent of damaged structures in the cadaveric and 3DP materials were noteworthy to consider while planning the trials [48].

Evaluating the effectiveness of 3DPMs in medical education requires a comprehensive approach that considers various aspects of learning and engagement. The Pre- and Post-Testing of the 3DPMs to measure changes in knowledge acquisition and retention. This can be done using written exams, multiple-choice questions, or practical assessments. Evaluate students’ practical skills, such as surgical techniques or diagnostic procedures, using 3DPMs. This can be done through simulations, observations, or assessments of model modifications. Case Studies and Problem-Solving Exercises: Assign case studies or problem-solving exercises that require the application of knowledge gained from using 3DPMs. This can assess the ability to transfer knowledge to real-world scenarios. Collect feedback from students through surveys or interviews to assess their engagement, motivation, and satisfaction with the use of 3DPMs. This can provide valuable insights into the impact of the models on the learning experience. Compare the effectiveness of 3DPMs with other teaching methods, such as lectures, textbooks, or computer simulations. This can help determine the unique advantages and limitations of 3DPMs. Conduct follow-up surveys with students after they have completed the course to assess the long-term impact of 3DPMs on their learning and retention of knowledge. Assessment of the potential learning curve of 3D model-based learning would require a longitudinal study of 3D use over time compared to 2D traditional learning [51]. When outcome evaluations are conducted, objective outcome indicators should be strived to be used. Alternatively, when subjective outcome indicators are employed, strict and unified evaluation criteria should be established so that the influence of subjective factors can be minimized and the reliability of the research findings can be enhanced.