Revolutionising orthopaedic implants: a comprehensive review on metal 3D printing with materials, design strategies, manufacturing technologies, and post-process machining advancements

This paper conceptualises an understanding of advanced manufacturing methods to develop 3D-printed metallic orthopaedic implants, including a brief discussion on post-process machining. The significance of Metallic Additive Manufacturing (MAM) and its practicality for industrial applications is discussed through a juxtaposition with conventional casting and machining approach. Different alloys and suitable MAM techniques are thoroughly reviewed to determine optimum operating conditions. Although MAM can produce near-net shape parts, post-processing is an unavoidable requirement to improve surface quality and dimensional accuracy. A comparative study is presented, highlighting the importance of machining for post-processing in terms of cost savings and performance. Different materials are evaluated aiming to overcome problems associated with existing orthopaedic implants. The consequence of bone-implant mechanical mismatch leading to stress shielding and inadequate corrosion properties obstructing biodegradability are explored in detail. The effect of additive manufacturing parameters on mechanical, corrosion, and surface properties including biocompatibility is analysed. Evidence of MAM’s advantages over conventional manufacturing approaches, such as the use of functionally graded lattices and patient-specific customised designs, is also presented. Finally, for future studies, a two-way approach is conceptualised with material selection and manufacturing process control in progressions of implant development using MAM.