Investigations of 3D printed orthopaedic cortical bone screws to improve biomechanical pullout strength

Abstract

Bone fractures are a common hazard due to external forces acting on the bone, causing misalignment, or breakage of bones. Bone drilling is imperatively required for fractured bone fixation used during orthopaedics surgeries, joint replacement, plate implantation, and total knee arthroplasty. The fractured bone is repaired with bone screws and implants to secure and retain the accurate position of fracture parts for early mobilization and early union. Bone screws are used in almost every orthopaedic surgery, as they provide inter-fragmentary compression to support the fractured bone. The success of osteosynthesis is affected by bone-screw interface holding power, type of screw used, screw purchase strength, the number of screws used and bone mass available for fixation, the orientation of screws and bone mineral density. The poor pullout strength and holding power at the bone-screw interface may lead to intolerable pain, screw loosening and implant failure at the fracture site can cause reoperation and revision surgery. These orthopaedic bone screws are made up of metallic biomaterials such as titanium, and stainless steel that are strong, ductile, fatigue-resistant, and highly biocompatible. However, due to the high stiffness and high strength of metallic screws, they may cause stress corrosion, the stress-shielding effect, tear and wear in the surrounding tissues. Further, strong integration at the bone-screw interface by sharp threads and soft bony tissues complicates the post-operative revision surgery while removing the metallic screws. This problem can be solved with biodegradable bone screws. Three-dimensional (3D) printing technology provides the ideal tailor-made solution for different orthopaedic applications. Various researchers used this technology for the fabrication of patient-specific prosthetics and customized implants. Limited research is reported for the fabrication of orthopaedic bone screws using 3D printing technology.