Three-dimensional printing in colorectal surgery

Introduction

Three-dimensional (3D) printing is an engineering process during which a 3D object is created by applying various materials using a computer-generated model. Materials are usually applied layer by layer. ^, The process can be broken down into the following components:

• Image acquisition/creation

• Modeling: In which computer-aided design (CAD) software, a scanner, or a digital camera creates a digital 3D rendering of an object

• Printing: Several modalities are currently available for 3D printing. Stereolithography uses a liquid photoactive resin that is solidified by ultraviolet light. Fuel deposition modeling uses heat to create object from molten plastics. Multijet modeling uses multiple materials to create color-coded objects at high resolution. These modalities vary in their resolution quality, time to print, and cost.

3D printing has application in a multitude of industries. Product design and engineering as well as the automotive industry were initial adopters of the discipline. In medicine, 3D printing has the potential to be useful in several aspects. Anatomic models, especially those based on individual patient anatomy, can be used for educational purposes, preoperative planning, and training. Surgical instruments and implants and prostheses can be manufactured using 3D printing. In many instances, these “prints” can be customized to a patient's anatomic characteristics.

This segment will focus on the current application of 3D printing in the specialty of colorectal surgery.

Colorectal surgery

The specialty of colorectal surgery is unique in several aspects. It covers a large part of the visceral anatomy. Many disorders in colorectal surgery are associated with or located in the pelvis, a part of the human body with intricate anatomical detail, involving the digestive tract, complex vascular anatomy, and the nervous system. The anorectal region is also intricate in its anatomy. Surgery on any part of the anatomical structures associated with colorectal surgery may affect the anatomical integrity, as well as function of one or more structures aforementioned. In theory, this specialty may lend itself to several applications of 3D printing. Several reports have been published demonstrating the feasibility of 3D printing in colorectal surgery.

Preoperative planning in rectal cancer

Hanabe and Ito used a 3D printed model of the pelvis to facilitate the understanding of anatomy in rectal cancer. The end goal was to aid the surgeon in laparoscopic rectal cancer resection. A multidetector CT scan was used to acquire arterial and venous images with axial thin-slice reconstruction. With the aid of CAD software and a 3D printer, pelvic models with all vital structures (bones, muscles, iliac vessels and branches, nerves, and urogenital organs) were created. Even though the model was of high quality, the long printing time of 40 h and the inelastic nature of the printing material were limiting factors. The model demonstrated the complex special relationships between the pelvic structures but could not replicate the texture of live tissue, as well as the mechanics of an actual surgical procedure realistically.