# Additive Manufacturing for Surgical Planning and Education: A Review
## 4 Applications of 3D Printing in the Medical Field
### Surgical Planning  
Surgical procedures necessitate a deep understanding of human anatomy and the intricate relationships between various anatomical structures. Traditionally, this knowledge is imparted through the study of human cadavers in medical school's preclinical studies and is further honed through practical experience during real surgeries [87]. Visualizations presented on 2D or 3D computer screens may not provide an intuitive grasp of complex anatomical intricacies [88; 89] (see Figure 11). Moreover, the ability to practice both general  
Figure 10: Skull with 3D-printed embedded implants [86]. surgical procedures and patient-specific techniques, especially in highly complex cases, enhances surgeons' skills and outcomes [90]. Utilizing patient-specific scans to generate 3D models holds significant utility in various surgical and training contexts. Presently, PBF technologies for polymer and metal are considered the gold standard for surgical applications [91]. A study involving 158 students explored the pros and cons of 3D printing in surgery. Benefits highlighted encompass improved preoperative planning, model accuracy compared to the patient, and reduced surgery time [92]. Drawbacks include disparities between the 3D model and the patient's physical condition, extended preoperative planning duration, and expenses related to printing machines and CAD software. Across surgical specialties, 3D printing is revolutionizing the surgical process [93]. Surgeons employ 3D models to familiarize themselves with intricate structural abnormalities, enabling optimal surgical planning through rehearsal of complex procedures. This meticulous planning allows surgeons to anticipate and address potential issues in advance, potentially reducing surgery duration and errors. Despite the increased time invested in preoperative planning, it enhances surgeons' skills and confidence before the actual procedure. In some instances, sterilized 3D models are brought into operating rooms to provide surgeons with enhanced visibility in challenging areas [92]. In interdisciplinary approaches, 3D-printed models facilitate shared understanding among medical teams, enabling patient absence during collaborative planning sessions. While the adoption of 3D printing in surgery is growing, the systematic review indicates limited efforts in in-house fabrication of customized implants or prostheses using 3D printing. This approach necessitates proficiency in CAD software, demanding additional  
Figure 11: Pre-surgical planning for neurosurgeons using a 3D-printed model [94]. skills, expertise, and time from the surgical team. Currently, radiological scans remain the most commonly used data for 3D-model printing. Having a physical representation of a patient's anatomy allows physicians to study and simulate surgeries more effectively compared to relying solely on 2D MRI or CT scans displayed on flat screens [95]. These models provide a tangible advantage over cadavers, which are often limited in availability and pose challenges in terms of cost [96]. Cadavers lack specific pathologies, offering more of an anatomy lesson than a realistic representation of a surgical case. Additionally, 3D models prove invaluable in studying complex spinal deformities. For training doctors in colonoscopies, high-quality 3D anatomical models, accurately representing specific pathologies, are essential, given the significance of colorectal cancer as the second leading cause of cancer-related deaths [73; 96]. Neurosurgeons find 3D-printed neuroanatomical models particularly beneficial (Figure 12) [87; 97; 98], as they illuminate the complicated relationships among cranial nerves, vessels, cerebral structures, and skull architecture. These complexities are challenging to interpret using only 2D radiographic images, and even a small error in understanding this intricate anatomy could have severe consequences.