Basic research on osteoarthritis has been carried out mainly from the his tological and biochemical aspects of the degenerating chondrocytes, collagen fibers, and matrix proteoglycans. Undue mechanical stress has been shown to be the principal factor in the initiation of osteoarthritis. Although the exact process by which mechanical stress leads to the total destruction of cartilage tissue remains unclear, several new research methods have enabled us to gain a deeper understanding of the process of degeneration. In October 1997, we organized an international symposium titled "Ad vances in Osteoarthritis" in Kobe, with the main topics being updated re search, diagnosis, and treatment of osteoarthritis. The proceedings of the symposium are presented here in five sections: (1) Mechanical stress and reactions of chondrocytes, such as intracellular ion changes, changes in the cytoskeleton, intracellular messenger systems, release of gas mediators, and changes in electromechanical properties of cartilage; (2) Functional diagnosis of osteoarthritis by MR imaging, and using calpain and collagenase III as new cartilage markers; (3) Treatment with a promising simple washout technique and IL-1RA and MMP antagonists; (4) Cartilage repair by new grafting tech niques; and (5) Problems following total joint replacement. We sincerely hope that the advanced knowledge provided in this volume of proceedings will be valuable to our readers.

It was a great honor for us to preside over the Hip Biomechanics Symposium, held on November 19, 1992, in Fukui City, Japan. We believe it was the first interdisciplinary conference on biomechanical approaches to hip disorders; this volume contains the presentations made at the conference. The information found here will be of value not only for orthopedic surgeons but also for researchers. The advent of biomechanical approaches to hip dis ease has made possible the understanding of fundamental hip pathologies, an understanding which enables us to institute the appropriate non-surgical or surgical treatment. Indeed, efficient surgical planning is not possible without taking these approaches. This comprehensive volume consists of six major sections: loading, gait analyses, THA, osteotomies, motion analyses, and stem designs for stability. Each of these sections brings together many of the leading researchers in this field. We hope this volume will be a spur to future understanding of and on fruitful research on hip disorders. The Editorial Committee wish to express their deep gratitude to the contri butors and the publisher. Shinichi Imura Noriya Akamatsu Hirohiko Azuma Kazuhiko Sawai Seisuke Tanaka v Table of Contents Preface......................................................... V I Hip Joint and Loading 1 Two-Dimensional Finite Element Analysis for Stress Distribution in Normal and Dysplastic Hips Nobuo Konishi.. . .. . . . . . .. . . . . . .. . . . . . . . . . .. . . . . . .. . . . . . . . . . 3 2 Stress Distribution at Hip Joint During Level Walking Kazuhiko Sakamoto, Yoshinobu Hara, Akira Shimazu, and Kenji Hirohashi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 . . . . . . . . . . . . . . 3 Biomechanical Studies of the Hip Utilizing Computer Simulation Takatoshi Ide, Yasuhiro Yamamoto, and Shigeru Tatsugi . . . . . . . . . 21 ."

Basic research on osteoarthritis has been carried out mainly from the his tological and biochemical aspects of the degenerating chondrocytes, collagen fibers, and matrix proteoglycans. Undue mechanical stress has been shown to be the principal factor in the initiation of osteoarthritis. Although the exact process by which mechanical stress leads to the total destruction of cartilage tissue remains unclear, several new research methods have enabled us to gain a deeper understanding of the process of degeneration. In October 1997, we organized an international symposium titled "Ad vances in Osteoarthritis" in Kobe, with the main topics being updated re search, diagnosis, and treatment of osteoarthritis. The proceedings of the symposium are presented here in five sections: (1) Mechanical stress and reactions of chondrocytes, such as intracellular ion changes, changes in the cytoskeleton, intracellular messenger systems, release of gas mediators, and changes in electromechanical properties of cartilage; (2) Functional diagnosis of osteoarthritis by MR imaging, and using calpain and collagenase III as new cartilage markers; (3) Treatment with a promising simple washout technique and IL-1RA and MMP antagonists; (4) Cartilage repair by new grafting tech niques; and (5) Problems following total joint replacement. We sincerely hope that the advanced knowledge provided in this volume of proceedings will be valuable to our readers."