12Designing Custom Knee Joints for Japanese PatientsResearch1. Hisamori’s students explore new ideas for spinal fixation parts 2. Titanium alloy artificial knee and hip joint parts 18SOPHIA MAGAZINE Vol. 19Advancing Titanium Alloys for Greater Safety and LongevityAn artificial knee joint is a medical device designed to replace de-formed knee joints. It consists of three parts made from different materials, with the tibial (shin) component typically crafted from a durable titanium alloy capable of bearing substantial weight. Professor Hisamori focuses his research on developing these ad-vanced materials.The materials used for artificial joints must meet rigorous stan-dards for durability and safety, as maintenance and repair are not easily performed once the joints are implanted in the human body. Hisamori has been collaborating with the Orthopedic Surgery Department at Keio University Hospital for over 30 years. Together, they study the optimal combinations of different ma-terials, including plastics. Their research also focuses on strength testing and processing methods to ensure long-term safety and reliability.“Over the years, the quality of materials has improved, and sur-gical techniques have advanced as well. When I was a student, an artificial knee joint would last about ten years, but today it’s around twenty. But that’s still not enough. Artificial joints expe-rience wear and tear with every movement, eventually leading to defects. As a result, replacement surgery is generally postponed until patients are over sixty years old,” Hisamori explained.Despite extending material lifespans, the recommended age for surgery remains at sixty because people are living longer. Hisamori believes that increased longevity of artificial joints would allow patients to undergo surgery earlier, and reduce the period of en-during pain in the meantime.“To achieve this, we need both improved materials and custom-ized designs tailored to each patient. This is why I am currently working on research on custom-made artificial knee joints.” Most artificial knee joints in use today are manufactured in North America and Europe and designed to suit to body types, bone structures, and lifestyles in those countries. While a range of sizes is available, they do not always provide an ideal fit for Japanese patients. Moreover, the size and shape of joints vary from person to person. Even slight deviations can cause signifi-cant discomfort for patients and have an adverse impact on the knee joint’s longevity. “The advent of 3D printing has made customized designs a real-ity. The 3D printing process, however, fundamentally differs from traditional manufacturing methods. Instead of pouring molten metal into molds, 3D printing involves layering titanium powder melted by lasers or electron beams. As a result, the properties, du-rability, and characteristics of the materials produced differ from those made using conventional methods. We are collecting and analyzing data on the strength, wear, fatigue, and safety of these materials. Our goal is to commercialize this technology within ten years of starting our research. As an engineer, I am deeply com-mitted to practical applications of research. I want to ensure that the outcome of our work contributes meaningfully to society.”Creating Possibilities for Multidisciplinary Collaboration in MedicineResearch in the medical field—including the development of artificial knee joints—is both essential and in high demand. Hisamori, however, points out that one of the key challenges in R&D is finding supportive of manufacturers and medical profes-sionals to collaborate with.“Many people recognize the importance of collaboration between medicine and engineering, but there are very few active, on-site research projects of this kind in Japan. Doctors are extremely busy with their clinical duties. While they are constantly exploring problems and potential solutions, they often lack the time or op-portunity to connect with engineering researchers like us,” he said.During his graduate studies, Hisamori had the good fortune of
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