インプラントからモデルへ：整形外科における3Dプリンティングの役割拡大

For decades, orthopedic implants have been essential for improving mobility, functionality, soothing pain, and rebuilding complex skeletal structures. Old manufacturing methods, such as casting, forging, and machining, have resulted in long-lasting implants but could not adapt to the complex anatomical variability in patients' anatomy. Additive manufacturing (3D printing) overcomes this limitation by allowing for complex, patient-specific computer-aided design (CAD) models to be created and implants to be manufactured containing precise porous architectures that encourage osseointegration and vascularization. This narrative review compiles evidence from systematic reviews, clinical studies, and experimental trials that were published between January 2020 and October 2025 to describe the historical development, clinical applications, outcomes, challenges, and future aspects of 3D-printed orthopedic implants. 3D printing is changing from an experimental modeling method to standard clinical practice with application in arthroplasty, spine surgery, trauma fixation, and oncology. The most common fabrication techniques for metallic implants can be divided into two components: selective laser melting and electron beam melting, while stereolithography and fused deposition modeling serve as significant aspects for the preparation of anatomical models, surgical guides, and biodegradable implants. Titanium alloys continue to be recognized as the gold standard for load-bearing devices, while biodegradable polymers and composites are being used in more recent pediatric and temporary implant surgeries. All data reports reduced operative time, better alignment precision, quicker osseointegration, and stable fixation with satisfactory short- to mid-term follow-up outcomes. Evidence from case series and systematic reviews supports the application of 3D printing in revision hip arthroplasty, cervical cages, patient-specific plates, and tumor reconstruction. However, cost, manufacturing standardization, reproducibility, infection control, and lack of substantial randomized clinical trials to prove the long-term safety and reliability of this new field still remain an issue that needs to be resolved to allow centers around the globe to adapt these kinds of techniques. Finally, these 3D-printed orthopedic implants present advanced anatomical integrity with greater mechanical stability than traditional types of implants. Moreover, innovative advances in technology include AI-assisted design, shape-morphing devices, and bioprinting of vascularized bone structures. Broader clinical adoption will depend on larger trials demonstrating safety, reproducibility, and cost-effectiveness.