In an effort to advance biomedical technology, the innovation and incorporation of additive manufacturing (AM) has facilitated the approach of bone defect treatment by enabling the development of patient-specific scaffolds, moving beyond conventional devices. AM enables the fabrication of scaffolds with tailored geometries, mechanical properties, and biological responses, using an extensive range of materials and methods. Such precision in scaffold design is essential for effectively treating bone defects, which can vary greatly in scale and complexity. This chapter offers a comprehensive guideline for scaffold customization, including bone defect imaging, material selection, topography design, and fabrication methodology. It will also highlight innovations such as in situ 3D printing, smart materials for scaffolds, and deep learning in design, pointing to future directions and challenges. Additionally, the chapter introduces a cooperative model involving patients, clinicians, and engineers, emphasizing an interdisciplinary approach for practical clinical application. This collaboration is anticipated to lead to a new era of bioactive medical materials, revolutionizing personalized medicine with innovative, tailored solutions for medical challenges.