**5. Conclusion**

By taking advantage of the retrospective RP model created, one important challenge was improving the amount of healthy bone preserved compared to that of conventionally performed resections. This means reducing the healthy bone in the resected specimen and leaving a greater volume of healthy bone in the patient, while always maintaining a safe oncological margin. This objective was fulfilled thanks to the 3D control in 3D planning and the 3D control provided by the navigator during the execution of the cut, as it can be observed

Surgical precision, understood as the correspondence between a target osteotomy and an executed osteotomy, is not the only factor to consider when evaluating navigation-assisted surgery. Some complications associated with intraoperative navigation, such as increased procedure time or uncompleted navigation due to technical problems, have shown to decrease as the surgeon team familiarizes with the technology (increasing their total amount of surgeries performed under navigation) [19]. On the contrary, the accuracy level in the registration process appears to be independent of the learning curve and not decreasing with user experience. Local tumor recurrence and non-oncological complications have also been used as

The experiment designed for this chapter shows how 3D printing can be applied to build experimental models, specifically for orthopedical oncology, that can be used for multiple applications. In the first place, these models are useful to test and characterize new surgical technologies such as image-based navigation. In the second place, these models can be used

The potential of 3D printed models as surgical training tools for patient-specific procedures has been evidenced for ENT surgery. In a case report where transtemporal tumor drainage assisted with intraoperative navigation was determined as treatment, the preoperatively planned trajectory to access the tumor was executed under navigation first on a 3D model of the patient's skull and then on the real patient. The mean distance between target trajectory and executed trajectory measured in the 3D model was reduced by 73.66% when measured in the real patient. This probes how 3D printed models are a promising method to increase

3D-printed prototypes are currently gaining accessibility, as 3D printers become more massive and more economical. This manufacturing method is improving both its technical characteristics (such as the speed of printing, resolution and the variety of materials available) and its cost. Therefore, it is reasonable to believe this method can be easily available in clinical practice, turning it into a promising option for the testing of new surgical technologies and procedures.

This work was the first validation experiment of the workflow proposed, which consists of preoperative planning and image-based navigation for orthopedic precision surgery. Subsequent validation and protocolization works have followed this experiment, finally building a routine that is implemented on a weekly basis at the department of computer-assisted surgery at our hospital (Unidad de Cirugía Asistida por Computadora, Hospital Italiano de Buenos

parameters to evaluate the benefits of navigation-assisted surgery [20].

by the surgeons for training on particular procedures.

accuracy in surgeries assisted with navigation [21].

Aires) [22].

in the RP model with colors.

182 3D Printing

The ability to combine different emerging technologies gives important solutions in the field of surgery planning and preoperative surgical design. The 3D prototype as a way of reproducing a surgery is a training model for surgeons interested in knowing the behavior of 3D planning and its reproduction through the navigation of osteotomies in orthopedic oncology. It is possible, in this way, to test surgeries from RP models manufactured from real cases. This method stands out as it is easy to implement and to understand, as well as technically simple and economical.

Likewise, other benefits of this conglomerate of technologies include multiplanar or difficult osteotomies in limb deformities, pre-cast in osteosynthesis plates using the RP models as a guide mold, controlling oncological margins to avoid errors of cut in real surgery and, above all, save surgical time with its cascade of beneficial effects for the surgeon and the patient.

In our hospital department, we were able to adopt computer-assisted surgery for oncologic orthopedics as a standard routine. This includes weekly meetings of specialized medical professionals who perform the preoperative planning for challenging surgical cases, which are then executed intraoperatively under navigation guidance. More than 250 patients have been treated to date following this working protocol, since its introduction 8 years ago. This is an example of how new technologies developed in silico can rapidly reach health care activities.
