Singapore General Hospital

Dr. Henry Soeharno

3D printing or additive manufacturing is a process involving the creation of three dimensional solid objects from a  digital file. In contrast to conventional subtractive manufacturing, such as milling, where an object is created by  removing excess bulk material, 3D printing creates an object from the bottom up, layer by layer. In the healthcare  setting, this usually involves the use of Computed Tomography (CT scan) DICOM files. The files then need to  undergo a process known as segmentation and eventual conversion into 3D printable files, known as STL files.

3D printing technology was first described as far back as the early 1980s, however it was not until around 2005  that the technology became more accessible and widespread across various industries. This coincided with the  expiration of the original 3D printing patent from the 1980s. Since then, in tandem with advancement in computer  technologies, 3D design software and materials, 3D printing has become more mainstream in many industries  including healthcare and medicine.

In Orthopedic surgery 3D printing is used in pre-operative planning, intra-operative adjuncts (eg: 3D printed jigs  for bone cutting or screw firing), as well as 3D printed prosthesis/ implant manufacturing.

In the past, 3D printed bone models were most commonly used in the planning of complex maxillofacial reconstructive surgery, however in recent decades it has become common practice in the Orthopedic Surgery arena. A widespread of Orthopedic sub-specialties have adopted 3D printing technology, including: trauma surgery, joint arthroplasty, paediatric orthopedic ,foot and ankle surgery, spine surgery, sports surgery, musculoskeletal tumour surgery as well as joint preservation surgery.

The ability to pre-plan surgeries using an anatomically accurate life size 3D bone model has been shown in numerous studies to reduce operative time as well as increase surgical accuracy.

Trauma surgeons are able to better visualise complex bone fractures and pre-bend implants to best-fit prior to surgery. Complex spine deformities are better appreciated on a 3D model and simulation corrective surgeries may be performed in a controlled environment prior to actual surgery. In paediatric orthopedic surgery, 3D models of congenital deformities allow accurate surgical planning, simulated deformity correction and implant pre-contouring.

"The advancement in 3D printing technology as well as biomaterial development has allowed for the printing of custom patient specific bone scaffolds."

The advancement in 3D printing technology as well as biomaterial development has allowed for the printing of custom patient specific bone scaffolds. These synthetic bone scaffolds are used to reconstruct large bone defects, a common technical challenge in bone tumor surgery and complex joint arthroplasty surgery. The implanted bone scaffold will allow the patient’s native bone to regenerate along the scaffold, restoring skeletal integrity. This technique has many advantages when compared to the use of cadaveric bone graft, such as the avoidance of potential risk of disease transmission, graft resorption, just to name a few.

Custom 3D printed metal implants have allowed the restoration of complex bony defects where mass produced off the shelf available implants will not be adequate or suitable otherwise. A good example of such customised metal implants are tumor end oprosthetic implants used for reconstruction following a major bone tumour resection in the pelvis. Patients with abnormal skeletal anatomy poses a significant challenge in joint arthroplasty surgery, where off the shelf conventional implants would not fit the patient’s abnormal anatomy. The ability to custom design and 3D print patient specific implants in such cases have allowed Orthopedic surgeons to address surgical challenges which conventional implants would not have been able to address.

The following is a case example in which 3D printing was utilised in pre-operative planning of a 62 years old female who 3 months following her right total knee replacement, sustained a right tibia peri-prosthetic fracture due to an accidental fall. Pre-op CT scan shows a displaced proximal tibia shaft fracture at the level of the tibial stem with intact implant components (Figure 1). DICOM files from the CT scan was subsequently utilised to 3D print a life size bone model for the use of pre-operative planning (Figure 2) and appropriate fixation plate was selected (Figure 3). The fixation plate was subsequently pre-bend and contoured onto the bone model for best fit before being sent for sterilisation prior to actual surgery (Figure 4).

Aside for its clinical use, 3D printed bone models have been pivotal in the area of education. Medical students, surgical residents as well as specialist have benefited from the use of 3D bone models. These models allow for a better understanding of anatomy and disease processes. It serves as an invaluable communication tool between health professionals and patients. Patients are able to better understand the disease process and make more informed decision regarding surgery.

3D printing in healthcare is developing rapidly in recent decades. What started off as simple printing of 3D bone models for pre-operative planning has evolved into bio printing of biological cells to restore the diseased human body. A lot of research and development is underway and it is an exciting time to witness the ever evolving forefront of medical technology in pursuit of better patient care.