The 15 studies included in this analysis were published between 2015 and 2019 (Table 1). 3D printing has become more and more popular in medical education in recent years. Out of the 15 included studies, 8 were from China. Due to the uneven sources of literature, there might be regional bias.
In the past, for the medical student, the primary learning object was often a real human body. Some of the surgical teaching and research departments in hospitals have anatomical maps hanging to help students learn. Today, some departments teach students how to learn human anatomy through 3D computer graphics. 3D printing has the advantages of high accuracy, good integration, fast reconstruction, and low cost. The technology has gradually entered the medical classroom.
After 1–2 class training, our research showed that there was no significant difference in test scores between the 3D printed heart group and the traditional group in the random-effects model (p > 0.05). Sensitivity analysis indicated that the result was reliable. However, in the nervous system model, motor system and abdominal anatomical model, the performance of the 3D group was better than the traditional group. In the nervous system model, sensitivity analysis suggested that the result was reliable and stable as well. The reasons for the above differences might be as follows: (1). The number of literature included in the study was relatively small; (2). The content of the test was different, the degree of difficulty was different, and the crowd was different. In our study, students in the 3D printing groups took less time to answer questions (P < 0.05), compared to the conventional groups. Wu reported that compared with a conventional group, students in a 3D printing group spent less time answering questions on the pelvis and spine, although there was no significant difference in the time spent on the questions related to the upper and lower limbs between the two groups. Li reported that both male and female students spent less time answering spine models in a 3D group compared with a conventional group. The different results of the above research may be due to variations in the students and organs. In general, 3D printing groups took less time to answer questions compared with conventional groups. This result may be because 3D printed models are easy for students to learn from and easily arouse students' interests. As can be seen from the above, for most anatomical sites, the 3D group has certain advantages in terms of test scores and time consumption.
The visual funnel diagram was tested for symmetry and was found to be symmetrical (Fig. 6). By loading the “meta” package (https://cran.r-project.org/web/packages/meta/), both Egger’s and Begg’s tests showed a P-value > 0.05, indicating the absence of publication bias.
3D printing is widely used not only in medical education but also in the field of surgery . 3D printing models are also used in surgical oncology, plastic surgery, and dental surgery and are included in guides. In addition to educating students and surgeons, studies have highlighted the important role of 3D printing in patient education to improve patient consent [32, 33]. Diment  used a descriptive-analytical method to analyze the application of 3D printing models in the clinical fields and proposed that 3D models have effective applications. Bai et al.  reported, in their meta-analysis, that 3D print-assisted surgery was better than conventional surgery in terms of the operation time, blood loss, and good outcome. Compared with a conventional group, a 3D printing group showed shorter operation time, less intraoperative blood loss, and faster healing time in patients with tibial plateau fractures, suggesting that 3D printing technology-based treatment was appropriate for tibial plateau fractures . Benjamin  used descriptive statistical methods to report the role of 3D printed models in surgical education. The author concluded that 3D printing technology has a wide range of potential applications in surgical education and training. Although the field is still relatively new, some studies have shown that education that employs 3D printing can replace or supplement conventional education .
3D printed models also have some shortcomings. If students only have access to “scaled” models, it could lead to a lack of understanding of real size and relation to other anatomical components . The accuracy of 3D printed models remains a challenge and they have yet to completely replace human structures . The costs associated with various materials and equipment are also a problem. Moreover, the ethical issues regarding 3D printed models should not be ignored. However, despite potential cost constraints, the prices of 3D printing equipment, materials, and software have been declining, [34, 36] and more and more educational models of 3D printing are becoming learning tools for students . Therefore, we hope that 3D printing models will play a role not only in surgery and communication but also in the anatomy classroom.
Because most of the 15 papers included in this study were from China, there were potential sources of bias. Most of the papers did not specifically describe the procedures of randomization, such as the method of generating random numbers. It was not suggested whether to adopt blind research. Furthermore, most of the studies were heterogeneous. The possible reasons for this heterogeneity are as follows: the overall quality of the students in different countries was different, the quality of teachers was different, the contents and objectives of teaching were different, the contents of questionnaires were different, etc. The sample sizes in most of the studies were small.