A major part of orthopedics is the treatment of musculoskeletal diseases caused by structural disorders and mechanical breakdown of living tissue. Therefore, biomechanical consideration of static structures and dynamic mechanisms is compulsory for both diagnosis and treatment of orthopedic diseases. Previous biomechanical studies have enabled great advances in orthopedic implant technology, such as artificial joint replacement and instrumentation for spinal fusion. Consequently the importance of biomechanics is increasing more and more in daily clinical practice and development. In addition, biomaterial research into mechanical properties and tissue reactions of implant materials is certainly an important area of related study. This book is comprised of 22 papers presented at the International Seminar on Biomechanics in Orthopedics and the 17th Annual Meeting of the Japanese Society for Orthopedic Biomechanics, held in Nagoya in 1990. The volume contains full descriptions of both conventional and updated knowledge of the spine, ligaments, artificial joint replacement in the hip and knee, fracture treatment, and gait analysis, as well as biomaterials. I earnestly hope that this book will be of benefit to readers in daily clinical work and research. To close, I would like to thank profoundly the two coeditors, Prof. S.M. Perren and Mr. T. Hattori, and also a quiet supporter Mrs. J. Buchanan in Davos, for their cooperation in producing this book.