The Quantitative Impact of Using 3D Printed Anatomical Models for Surgical Planning Optimization: Literature Review

Abstract

3D printing has entered the medical field as a visualization tool that allows the manufacture of three-dimensional (3D) models that physically represent the anatomy of a patient in need of analysis to improve surgical results. This article analyzes the literature around reported study cases that make use of anatomical models for their surgical processes' planning, focusing on obtaining the quantitative results of each one of them. A search of case studies was carried out in the main medical databases such as PubMed, ScienceDirect, SpringerLink, among others; to obtain the most relevant results of the 56 selected articles, the information of each study was analyzed and categorized. These articles presented figures and data about the benefits that are considered more representative to measure the positive impact of this technology. These benefits are summarized in variables such as the decrease in surgical time, greater accuracy in the diagnosis of pathology, blood loss reduction, and decreasing operating room costs; owed to an improvement in the surgery planning. It was found that in all the cases analyzed there was an improvement in the surgical results related to these variables, which were summarized in macro figures that combine this improvement quantitatively. In the analyzed studies, it was evident that there is great potential in the use of 3D printing for presurgical planning, being as the results of these analyzed interventions were better when using this technology. In addition, it was found that the results obtained initially, before applying the inclusion and exclusion criteria, were mostly of a qualitative nature; expressing the perception of researchers regarding the positive use of this tool in the field and evidencing an opportunity for this research to focus on concrete and technical information to show in numerical terms the effectiveness of this tool, to demonstrate the cost-benefit that it has for the field.

1. Introduction

Contextualization (background, delimitation, and consequences)

In recent years, diagnostic images obtained from medical examinations, such as computed tomography or magnetic resonance imaging, have been required for the diagnosis, planning, approach, and treatment of surgical procedures. These images provide a two-dimensional (2D) virtual reproduction of a patient's anatomy and pathology for the medical specialist to study; however, these have several limitations. The analysis of these diagnostic images is a highly complex process because the 2D axial data require the radiologist and surgeon to develop a mental image of the pathology.¹

Furthermore, the format in which these images are presented fails to show the specialist missing information about the spatial relationships between the organ structures, and lack the tactile and physical tridimensional qualities necessary to improve the understanding of the anatomy in question.² For this reason, in cases where the visualization and interpretation of a pathology is complicated, it is less likely for the doctors to accurately identify all the information required; thus, unreliable interpretation of diagnostic images leads to numerous risk factors for both patients and health centers. This is the result of unexpected complications during the intervention owing to missing information that was not displayed in the image and then, was not considered in the planning process.³

As a result of this complexity, it has become necessary to implement an alternative tool that would improve the visualization and analysis of high-risk pathologies and their surgical results. This necessity has led to new applications of 3D printing within the medical field by means of the tangible representation of a patient's organs through the construction of a 3D printed anatomical model, which, was itself obtained from the diagnostic images.

These anatomical models provide a full-scale physical representation of the affected organ,⁴ thereby making it possible to study and analyze the pathology and plan the surgery. The appearance of 3D printing as an opportunity to materialize an intangible object has enhanced surgical results by virtue of the improvement in the visualization of pathologies.

1.1 Study focus

The key benefits of this alternative in the medical field serve as metrics or indicators that validate the utility of printing anatomical models. As presented by Xu et al.,⁵ patient-specific 3D printed models can help reduce the incidence of unexpected or adverse events; intraoperative and postoperative complications; time in the operating room; and potentially hospitalization expenses. They can be used to facilitate decision-making as well as promote doctor–patient communication and medical education.

Through an analysis of several clinical studies including the aforementioned, it was discovered that surgical results obtained with the use of 3D printed models are primarily based on the following benefits: (1) the impact on operating room time, specifically the time saved in a surgical intervention; (2) the degree of surgical modification in diagnosis and intervention, alluding to the point in which a specialist changes the diagnosis or surgical plan after analyzing the pathology with a 3D printed anatomical model; (3) the amount of blood loss during surgery; and (4) the impact on operating room costs. The last indicator allows for the development of a cost–benefit analysis of the use of 3D printing for preoperative planning in high-risk surgeries. These benefits will be considered as study variables that constitute the principal focus of this research.

This article focuses on obtaining quantitative data that measures the effectiveness of 3D printing in the medical field in relation to the previously mentioned study variables. This approach emerged after noting that much of the current literature and data supporting the use of anatomical models for the visualization of a patients' anatomy in high-risk surgeries planning are promising yet mainly qualitative owing to the lack of studies that objectively demonstrate improvements in the performance of interventions.⁶ In addition, further research is required to determine whether intervention costs, including the use of printed anatomical models, can be balanced with the observable advantages of this technology. By means of this, it can be concluded that there is a need of a formal cost-effectiveness analysis.²

This research project is based on a literature review within the principal medical databases. It aims to demonstrate the positive impact that the use of 3D printing technologies has had in high-risk surgeries in case studies reported between 2012 and 2020. The previous is intended to quantitatively demonstrate the effectiveness of 3D printing in the medical field and therefore, its utility, causing appeal from hospitals, clinics, and health centers for its generalized use.

2. Materials and Methods

A literature search was carried out in main databases such as PubMed, ScienceDirect, SpringerLink, among others. For the search and selection of the articles, a study protocol was established and divided into four stages. In addition, Microsoft Excel tables were used to organize and categorize the information:

Stage 1, search parameters

A literature searching strategy was carried out based on parameters and pre-established guidelines to delimit and obtain the expected results for the databases. First, to narrow down the search and obtain texts aligned to the project's interests and analysis variables established, a combination of the following keywords was used: 3D printing, surgical time, cost-benefit, surgical decision modification, high-risk surgery, and anatomical models. Next, the search was limited to articles published from 2012 onward to ensure that the information is related to current medical practice.

Stage 2, filter 1

Subsequently, a first filter was settled in pre-established eligibility standards, which were divided into inclusion and exclusion criteria. In this filter, the title and abstract of the articles found were examined to determine if they were eligible for the following analysis. Articles that met at least one of the inclusion criteria were selected, these inclusion criteria were as follows: high-risk surgical cases, the use of anatomical models for the representation of vital and bone organs, the use of 3D printing for human medical applications, reported case studies with the use of anatomical printed models, the use of anatomical printed models for surgical guides, planning, and simulation.

In addition, if any of the articles contained one of the exclusion criteria, it was not included for analysis. The exclusion criteria were defined as the following: nonsurgical cases, dental surgery, plastic surgery, 3D printing for prostheses or medical implants, anatomical models made with living cells (biomodels), case studies aimed at education for doctors and patients. Table 1 provides a pre-established configuration of the criteria to decide on the inclusion or exclusion of an article.

Table 1.

Presetting of Criteria for Exclusion or Inclusion of an Article and Exceptions

In criteria	Ex criteria	Outcome	Exceptions
X	X	EX	If IN is equal to or greater than 5 and EX is equal to or less than 2, the results is IN
x		IN
	x	EX	If IN is less than 5 and there is an EX, the result is EX
		EX

Source: Self made.

EX, exclusion; IN, inclusion.

Stage 3, filter 2

Through the first filter, the articles eligible for analysis were obtained. Then, a second filter was then established. For this stage, the chosen articles were downloaded to obtain the full texts. Moreover, four new exclusion criteria were assigned: database access, case studies with at least one patient, inclusion of at least one of the study variables (impact on operating room time, level of modification of surgical plan, amount of blood loss, impact on operating room costs), and if the article was a duplicate among the others.

The main intention of this third stage was to analyze and extract basic information from each article to acknowledge in depth the medical specialty of the cases, the source country of the text, the study variables included in the article, the number of cases attended, and the type of study carried out, whether it was qualitative or quantitative. After analyzing each article, it was determined if they should continue to be considered for the study (included) or not (excluded).

Stage 4, final chosen articles

Finally, having the final articles selected for the study, the most relevant information and data were extracted from each of them. The research group analyzed the articles and captured the most relevant information in an Excel table, giving greater importance to the study variables that lead the research. This information was useful for subsequent analysis obtaining results, findings, and conclusions; whereupon the data are diagramed, and the information tabulated.

Figure 1 provides a flow chart of the study protocol, which presents by steps the methodology that was carried out and the number of articles that were obtained in each stage.

FIG. 1.

Flow chart of the search strategy and exclusion criteria. Source: Self made.

3. Results

In the literature review, 500 articles were initially found to meet the pre-established search parameters. Later, these articles were reviewed and submitted into filters leading to a total of 56 selected articles for the study research and an additional 10 for references. Additional file 1 provides a general description of the chosen articles and the analysis carried out for each study.

To begin with, the overall research results will be presented globally. Figure 2 provides the years of publication of the articles considered in the study. It can be observed that between 2017 and 2018, there was a significant increase in the number of studies published on the topic in question.

FIG. 2.

Evidence of selected studies according to the year of publication. Source: Self made.

Figure 3 provides the countries in which the selected articles were published. There is a predominance of studies carried out in China, the United States, and Spain.

FIG. 3.

Evidence of selected studies according to the country of publication. Source: Self made.

Figure 4 provides the specialties represented in each of the selected articles. Thus, the demand for 3D printing in different fields of medicine is evident. Orthopedics has the highest participation with 48.2% (n = 27), cardiology follows with 23.2% (n = 13), and neurology continues with 10.7% (n = 6).

FIG. 4.

Evidence from selected studies according to medical specialty. Source: Self made.

Next, results of the research regarding each of the study variables will be presented. This is a compilation of quantitative data from each of the selected and analyzed studies. The results of each variable were classified according to the different specialties considered because it was found that the surgical procedures and their results vary according to the specialty to which they belong; for this reason they should not be evaluated under the same conditions.

3.1 Impact on operating room time

Of the 56 final articles chosen for analysis, 34 studies were found to mention the impact of 3D printing on reducing time in the operating room (Table 2). From these, 64.7% (n = 22) were of the orthopedic specialty, 14.7% (n = 5) of cardiology, 11.8% (n = 4) of neurology, and 8.8% (n = 3) of oncology. This shows the predominance in orthopedic studies that evaluate the reduction in operating room time with the use of 3D printed anatomical out in the studies to measure and determine the time savings in each of them. In most cases, specifically in 70.6% (n = 24) of the studies, the procedure to determine the savings was making a comparison between a surgical intervention carried out in a conventional way and a surgical intervention carried out with the use of 3D printed anatomical models for preoperative planning.

Table 2.

Specialty-Classified Total of Articles Involved in the Study

Specialty	No. of articles	%
Orthopedics	27	48.2
Cardiology	13	23.2
Neurology	6	10.7
Oncology	5	9
Hepatology	2	3.5
General medicine	2	3.5
Urology	1	1.9
Total of articles	56	100

Source: Self made.

For both interventions, the duration of the intervention was measured, and the savings calculated. It was also important to consider that two patients or pathologies are never the same, but similar features were always considered to achieve data with greater accuracy. Furthermore, the utility that was given to the printed models within the surgical procedure was also considered, and it was found that in all cases these were used for the preoperative planning of the intervention, allowing the doctor to analyze the physical reconstruction of the anatomy of each patient and obtain feedback about their pathology to achieve a more successful intervention. In some of the cases these models had other utilities that will be explained hereunder with the results found in the different studies for each specialty.

Orthopedics

Among the studies related to orthopedics, the type of surgery performed as well as the amount of time reduced both in percentage and minutes per procedure were analyzed. Seven of 22 studies referred to mandibular reconstruction surgeries.

Vergez et al.⁷ mentioned a reduction of 120 min, and whereas these authors do not specify the total duration of the surgery without the use of 3D printed models by analyzing the conventional duration in other interventions of the same type of surgery, it was found that these can last a total of 4–6 h.⁸ Ren et al.⁹ mentioned a 145-min reduction on a 299-min surgery. Gil et al.¹⁰ found a reduction of 42 min over a total of 176.58 min; the utility they gave to the printed model was to obtain a precontoured titanium plate to use during the intervention and, thus, decrease the time in the operating room. Lethaus et al.¹¹ suggested a reduction of 25.2 min without mentioning the total duration of surgery. Olszewski¹² mentioned a reduction of 17.6% in operating room time, which is equivalent to 42.24 min saved. Hanasono and Skoracki¹³ mentioned a reduction of 102 min on a surgery with a total duration of 630 min, and finally, Ballard et al.¹⁴ mentioned a 66-min reduction on surgery without exposing its total duration.

In addition, five articles that referred to spinal and lumbar surgeries were analyzed. Parr et al.¹⁵ mentioned a reduction of 37.5 min in surgery; although the study does not mention the total duration of the intervention, it was found that such procedure can last a total of 3–6 h.¹⁶

The anatomical printed models in this study were used to provide visual, tactile enhancement, and appreciation of bone anatomy. On the contrary, Yang et al.¹⁷ exposed in their study a reduction of 14.8 min over a surgery with total duration of 175.5 min; the utility of the printed models was for an intraoperative reference. After a sterilization process with epoxyethane, they were able to enter the model into the surgery room during the operation. Yang et al.¹⁸ exposed a reduction of 28 min over a surgery of 212.32 min. Gálvez et al.¹⁹ mentioned a reduction of 94.3 min in the surgery time of two spine cases over a total time of ∼210 min; the 3D printed models helped the surgeon evaluate different alternatives and establish the best strategy. Finally, Li et al.²⁰ mentioned a reduction of 27 min over a total of 133 min in a surgical procedure.

Six of the 22 articles discussed limb surgeries for fractures or other complications. Sanz-ruiz²¹ in his study presented a reduction of 27 min in the surgery time of a periarticular knee osteotomy, over an average total duration of 1–2 h without the use of anatomical printed models.²² In their study, the models were sterilized in the hospital itself to be used in the operating room setting.

Corona et al.²³ showed a reduction of 156.6 min over a total value of 329 min; in their study the printed models were used to obtain prebuilt plates before surgery to avoid the task of making them during the intervention. Chen et al.²⁴ mentioned a reduction of 8.9 min over a total time of 75.4 min. Shuang et al.²⁵ exposed a reduction of 22.7 min over a total time of 92.3 min. Yang et al.²⁶ showed a reduction of 27 min in a case of trimaleolar fracture over a total time of 98 min. Finally, Lou et al.²⁷ exposed a reduction of 14 min over a total of 99 min in a surgical procedure.

Likewise, three articles referred to surgeries performed in the mid-body area (ribs, hips, and pelvis), where a reduction of 60 min was found in the study by Garcia et al.²⁸. Although the total time of a surgery of this type is not mentioned, it was found that a similar surgery to the one studied can have a total duration of 122 min without the use of 3D models.²⁹ The usefulness given to the printed models was to locate the pathology and position the incision to reduce time in the operating room. On the contrary, Liu et al.³⁰ mentioned a saving of 84 min over a total time of 372 min, and Maini et al.³¹ mentioned a saving of 8 min over a total duration of 119 min. Finally, one of the articles referred to bone tumor surgery where Punyaratabandhu et al.³² presented a reduction of 213 min in their study over a total value of 421 min.

Cardiology

About the five articles referred to the specialty of cardiology: regarding congenital heart disease surgeries, Hussein et al.⁶ mentioned a reduction of 22 min over a total duration of 88 min, whereas Ryan et al.³³ mentioned a reduction of 128.4 min over a total value of 230 min and Zhao et al.³⁴ showed a reduction of 34 min over a total of 285 min in a double outlet repair of the right ventricle. On the contrary, Giannopoulo et al.³⁵ presented a reduction of 28 min over a total of 212 min in a case of cardiothoracic application and finally, Barón and Guevara³⁶ in their study showed a reduction of 20 min over a total duration of 160 min in aortic aneurysm repair surgery.

Neurology

Regarding the four articles referring to the specialty of neurology: Vijayavenkataraman et al.³⁷ presented a reduction of 30 min in a cerebral arteriovenous malformation surgery, which can generally last 2 h, that is 120 min, in a conventional way.³⁸ Moreover, Lin et al.³⁹ mentioned a reduction of 17.5 min of a total of 225.8 min in a surgery for secular tubercle meningioma, Weinstock et al.⁴⁰ mentioned a reduction of 31 min over a total of 286.5 min in complex cerebrovascular injury surgeries; finally, Huang et al.⁴¹ showed a reduction of 16.4 min over a total of 143.4 min in endonasal endoscopic surgery. In Image 1 a brain tumor case can be seen. Here, a full-scale printed anatomical model was implemented to allow the specialist to plan the surgical intervention.

Oncology

Finally, the three studies regarding the specialty of oncology showed the following results: Leoncini et al.⁴² presented a reduction of 84 min over a total duration of 127.77 min in a segmental mandibulectomy surgery and microsurgical reconstruction for tumor extraction. In their study, it is mentioned that the use of prototypes tended to reduce surgical time, thanks to the plates precast and the previous selection of screws that were obtained with these models. Parras-Burgos et al.⁴³ showed a reduction of 52.5 min in malignant tumor reconstruction surgery over a total value of 337.5 min. Coelho et al.⁴⁴ showed a reduction of 180 min over a total time of 420 min in a frontoethmoidal meningoencephalocele surgery.

3.2 Degree of surgical modification in diagnosis and intervention

There were 8 of the 56 selected articles to mention this variable. This refers to cases in which doctors changed their mind or decision to cover surgery after analyzing the 3D printed anatomical model (Figure 5). It was found that 37.5% (n = 3) of the articles were from cardiology, 37.5% (n = 3) from orthopedics, 12.5% (n = 1) from hepatology, and 12.5% (n = 1) from oncology.

FIG. 5.

Medical specialist and resident of the cardiology specialty analyzing 3D printed models of congenital heart disease. Source: Self made.

To measure this variable, the procedure was carried out through, first, the analysis of a case study in a conventional way by a specialist. Only with the use of diagnostic images and virtual reconstructions of the case, the doctor had to perform a first diagnosis and surgical plan with this information. Later, the doctor was given the same case but accompanied by a 3D printed anatomical model. After analyzing it, it was decided whether to maintain the first decision on diagnosis and intervention. This strategy was implemented in 75% (n = 6) of the studies. Next, the results found in the different studies regarding each specialty is given.

Cardiology

Three articles referred to the cardiology specialty. Tam et al.⁴⁵ in their study mentioned a 20% decision modification, where 29 of 144 surgical plans changed after the analysis of a 3D printed anatomical model. Cantinotti et al.⁴⁶ mentioned a 47.5% change of decision, where in 19 of 40 cases the surgical plan was changed. Finally, Valverde et al.⁴⁷ mentioned a 53.6% decision change, where 15 of 28 surgical plans changed after analyzing the 3D printed anatomical model. As can be seen in Images 2 and 3, the analysis of anatomical printed models with their tactile and spatial qualities allows specialists to make more precise intervention decisions according to the needs of the patient and their pathology, helping to carry out a more successful surgery.

Orthopedics

There were three articles referring to the specialty of orthopedics. Corona et al.²³ presented an 80% change of decision, where 8 of 10 cases changed their surgical plan. Galvez et al.¹⁹ presented 28.6%, where two of seven cases changed their surgical plan. Finally, Mishra et al.⁴⁸ mentioned a 25% change in decision, where 3 of 12 cases changed the surgical plan.

Hepatology

There was one article that referred to the specialty of hepatology. Witowski et al.⁴⁹ mentioned a 26.3% change in decision, where 5 of 19 cases changed surgical plans.

Oncology

Finally, one article regarding oncology was found. Coelho et al.⁴⁴ presented 100%, because in the only case that was being treated, the decision was changed after analyzing the 3D printed anatomical model.

In conclusion, the importance of 3D printing technology in the field to obtain better results and make better decisions is evident owing to the amount of modified surgical plans with the use of 3D printed models. As mentioned by Witowski et al.,⁴⁹ the 3D models used preoperatively can change the surgical plan, in some cases significantly altering the extent of the surgery.

3.3 Amount of blood loss

There were 10 articles of 56 that mentioned about the amount of blood loss both in percentage and in milliliters. The specialties considered were 90% orthopedics (n = 9) and 10% neurology (n = 1). For this variable, the measurement method was very similar to that of the time impact variable.

The procedure carried out to measure the decrease in blood loss during surgery went about comparing two groups. In the first group, a surgery was carried out with the use of printed models; and in the second, in a conventional way. This procedure was performed in 90% (n = 9) of the studies, and in the remaining 10% (n = 1) the procedure was based on a comparison of surgeries performed with the use of printed models against surgeries previously performed or in other studies with traditional methods. Next, the results found in the different studies regarding each specialty is mentioned.

Orthopedics

Nine of 10 articles mentioned about the amount of blood loss from the specialty of orthopedics. Of these nine articles, three referred to spinal surgeries, where Yang et al.¹⁷ mentioned a decrease of 48.9 mL of blood loss over a total of 134.6 mL; in their study the anatomical printed model was sterilized and used within the operating room for intraoperative references. On the contrary, Yang et al.¹⁸ mentioned a decrease of 182.97 mL of blood loss over a total value of 1,029.65 mL; finally, Li et al.²⁰ exposed a decrease of 125 mL of blood loss over a total of 467 mL.

Separately, four of the nine articles spoke about fractures where Chenet al.²⁴ mentioned a decrease of 13.1 mL of blood loss over a total value of 54.2 mL. Yang et al.²⁶ mentioned a decrease of 25 mL of blood loss over a total value of 90 mL; in their study it is stated that the 3D printed prototype was able to accurately reflect the anatomy of the fracture site effectively, helping doctors plan the operation. On the contrary, Maini et al.³¹ exposed a decrease of 58 mL of blood over a total loss of 525 mL and Lou et al.²⁷ mentioned a decrease of 29.9 mL of blood loss over a total value of 216.2 mL. Galvez et al.¹⁹ mentioned a decrease of 235.7 mL of blood loss over a total value of 500 mL. Finally, Punyaratabandhu et al.³² exposed a decrease of 1550 mL of blood loss over a total value of 1800 mL in bone tumor surgery.

Neurology

Finally, a single article was found about the reduction blood loss regarding the specialty of neurology. Huang et al.⁴¹ in their study mentioned a decrease of 10.1 mL of blood loss over a total value of 170 mL.

Consequently, printed models were found to have a great impact on the variable in question (Figure 6). This can lead to great benefits for the well-being of both patient and clinical entity, because suffering the substantial loss of blood increases the risks for patients in surgical interventions and may require blood transfusions, which are associated with a high number of risks⁵⁰ and can affect the final costs of intervention and recovery time for the patient. It was also important to keep in mind that the amount of blood loss during a surgery may depend on other external factors as well, such as the type of surgery, its duration, and the use or not of tourniquet and the type of anesthesia applied.⁵¹

FIG. 6.

Neurology specialist doctor working on 3D printed model. Source: Self made.

3.4 Impact on operating room costs

Regarding the impact on operating room costs, it was found that 4 of 56 articles mentioned relevant data about this variable. Of these articles, 100% (n = 4) were from the orthopedic specialty. For this variable, the impact of the use of anatomical printed models to reduce the final costs of the operating room was evaluated. On the contrary, it is important to mention that on some occasions an increase in the final costs of surgery is possible owing to the manufacture of the anatomical printed models; however, with the reduction of other factors such as time, blood loss, and other benefits related to the patient's life quality, these costs can be justified and mitigated.¹⁰

Orthopedics

Among the orthopedic studies that mention savings with the use of 3D printing technologies, Parr et al.¹⁵ stated that a total of $100,000.00 USD can be saved in 250 cases if 7 min were reduced per procedure, this is equivalent to $400.00 USD in savings per case. This figure is obtained considering that a single minute of operating room plus 1 min in anesthetist fees is $80.06 USD. Lethaus et al.¹¹ mentioned in their study that a total of $439.74 USD can be saved in a case where ∼25.2 min in surgery time are reduced; this figure is obtained considering that the cost of a single minute in the operating room is calculated at ∼$17.45 USD.

Likewise, Garcia et al.²⁸ stated that in their study there were 40% savings in operating room costs after the implementation of 3D printed anatomical models, this equates to savings of $6,000.00 USD because it was possible to reduce the number of titanium plates required for operation (from five to three plates). Finally, Ballard et al.¹⁴ mentioned in their study that there was a minimum saving of $19,000.00 USD and a maximum of $518,000.00 USD in 1,316 surgeries studied between maxillofacial and orthopedic interventions, equating to savings that range between $14.44 USD and $393.62 USD per surgery, which equals to savings of $204.31 USD per surgery.

4. Discussion

Throughout the investigation, it was observed that, during the last decade, several studies have been carried out regarding the use of 3D printing in the field. An important finding from this review is that there is a lack of studies that integrate the variables that are impacted in preoperative planning in a quantitative and objective way. However, in this research it was possible to gather different data from multiple studies to quantitatively expose the impact of this technology in the field regarding the most influential variables, and the way this can positively affect the results of surgical procedures and its costs. Furthermore, thanks to this positive impact, a cost-effectiveness ratio can be held into account to justify the implementation of anatomical models for high-risk surgeries.

As it has been mentioned, the variables analyzed in the study quantitatively denoted the benefits that the use of 3D printing causes over surgical procedures, within which the impact on operating room time was highlighted. Because of this, the 3D printing of anatomical models can be understood as a tool to reduce surgical time in all cases analyzed. This benefit is of great importance for a procedure because it can directly affect other factors involved in this process, which improve the experience of doctors and patients as well as impacting the operating room costs. As mentioned by Parr et al.,¹⁵ the reductions reported in the operative time potentially reduce the risk of infection and radiation exposure while also providing cost compensation through better performance in the operating room and a reduction of postsurgical interventions.

Continuing with the variable in question, it is worth discussing the figures found in terms of savings in surgical time. Macro figures that weigh all the information found were obtained to finally demonstrate the impact achieved with this technology. The different specialties treated in the studies were continued to be considered, and it is worth mentioning that the orthopedic specialty has granted most of the studies valuable information. Table 3 provides the time saved in each specialty and the percentage of those savings.

Table 3.

Specialty Weighted or Time Impact

Specialty	Time saved (min)	Without 3D (min)	% saved
Orthopedics	84.8	257.1	33
Cardiology	36.5	191	19.1
Neurology	23.7	194	12.2
Oncology	105.5	295.1	35.8

Source: Self made.

Proceeding with the specific analysis of each study variable, the degree of surgical modification in diagnosis and intervention is next. In this variable it was observed that, in a very significant number of cases, the anatomical model allowed the doctors to have a better visualization of the pathology, which led them to change the decision or plan for surgical intervention. This largely demonstrates the relevance of printed models as it allows the medical team to make the best intervention decision and the most successful one for the patient.

On this occasion, the total cases of the studies that analyzed the decision change variable were added including different specialties treated. In addition, the cases that changed the surgical plan with the use of 3D printed anatomical models were also added. With these two figures it was possible to obtain a total percentage of the level of decision modification. Overall, there was a 31.42% decision change, this means that 82 of 261 surgical plans changed after analysis of the printed models.

In the third instance, the variable of amount of blood loss was analyzed, where the milliliters of blood lost per operation were counted. It was found that factors such as time and incisive precision can affect this variable the most. The incisive or cutting precision can be improved by decreasing its size given the better visualization and spatial relation that physical models provide. In the literature review, a figure was found that referred to this second factor. Punyaratabandhu et al.³² mentioned in their study that with the use of a printed anatomical model for planning surgery, there was a decrease in the length of the surgical incision of at least 17 cm. Bearing this in mind, the variable in question was analyzed gathering all the information according to the specialties included in the studies as given in Table 4.

Table 4.

Impact in Amount of Blood Loss Weighted by Specialty

Specialty	Saved blood (mL)	Without 3D (mL)	% saved
Orthopedics	484	766.3	63.2
Neurology	10.1	170	5.9

Source: Self made.

Finally, in monetary terms, an analysis was made of the information collected regarding the variable of impact on operating room costs. For this variable, the figures found in the articles referring to saving money for surgery with the use of 3D printed models were weighted. It should be noted that only four of the articles chosen for review showed conclusive and specific figures regarding the amount of money saved. This allows to deduce that there is a lack of studies that show in numerical terms the monetary impact of this technology for surgical procedures and therefore the cost-benefit of its use. Overall, it was found that there was an average savings of $348.01 USD in total in three of the four studies analyzed.

The remaining study, which is the one of Garcia et al.,²⁸ was not included within this average since it was considered as a special case because in its analysis there was a saving of $6,000.00 USD, which is above the general average, given that this value was compromised with the use of titanium plates for the intervention.

Other relevant information that influences the variable of operating room costs is the total cost of the printed models according to some of the articles analyzed in the review. With this information, it is possible to analyze the cost-effectiveness of this technology for the field. On numerous occasions, medical personnel tend to reject this alternative because of the cost required to manufacture the printed models, without previously making a relation with the money that this can help save for the clinical entity. The price of the anatomical models exposed in 19.6% (n = 11) of the articles analyzed^{11,14,17,21,23,52–57} found that a 3D printed model can cost an average of $228.52 USD including its manufacture.

It is important to mention that this cost may be subject to other external factors such as the printing material, the size and complexity of the piece, the use of complementary pieces in other materials, and so on, which can increase or decrease the average cost mentioned. Although this cost may seem a significant amount, the use of these models saves a considerable amount of time in surgery, more than enough to justify the costs associated with this production.²³

5. Conclusions

In conclusion, 3D printing technology has brought great benefits to the medical field, specifically for high-risk surgical procedures, where it has contributed as a tool that enhances pathology visualization to obtain better surgical results. It can also be concluded that among the literature referring to these practices, large and numerous contributions from authors were found that took place in case study investigations with the use of printed anatomical models; however, the results found in the review were mostly of a qualitative nature, expressing the perception of researchers regarding the use of this tool for such applications.

Still, because 3D printing is an emerging technology that is constantly evolving within the medical field, it requires new validations to justify its regular use. Therefore, there is a lack of concrete and technical information to show the effectiveness of the tool in numerical terms to demonstrate the cost–benefit ratio it has for the field. In addition, as it could be observed throughout the present investigation, the quantitative benefits of the use of this technology specifically demonstrate there is a positive impact for the field, and a better dissemination of these can contribute to the potentializing of this tool and a better quality of life for patients.

Authors' Contributions

All listed co-authors have taken part in writing the article, reviewing it, and approving its content.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This research project was funded by the Colombian government entity, Minciencias, in its call #781 of 2017 called “Young Talent in Health”. It was also supported by the Universidad Icesi's Innovation and Design Department.