Musculoskeletal Disorders: The Fatigue Failure Mechanism

This book presents a new mechanism as to how musculoskeletal disorders (MSDs) develop, not considered in previous books, but supported by several lines of evidence. broad implications for prevention and control of these costly and disabling disorders. Specifically, the book proposes that MSDs are the result of a material fatigue failure process in musculoskeletal tissues. It explains how fatigue failure theory provides a unifying framework for understanding why the physical risk factors of force, repetition, posture, and vibration exposures (encountered in many jobs) are associated with the development of MSDs.

The realization that MSDs result from a fatigue failure process has many important ramifications. For example, there are many validated methods of assessing the development of damage in materials resulting from fatigue failure. These methods allow for the development of easy-to-use risk assessment tools that can assess the cumulative effects of exposure to highly variable loading conditions and can identify the proportion of the overall risk associated with specific tasks (helpful in prioritizing tasks requiring intervention). This is something prior risk assessment approaches have not provided. The fatigue failure risk assessment approach has been shown to be helpful in assessing other issues, such as the effectiveness (or lack thereof) of job rotation scenarios, as well as helping to quantify the effectiveness of exoskeletons. The book also discusses how fatigue failure techniques are well-positioned to address future advances in MSD risk assessment technology, for example, techniques are available to deconstruct complex continuous loading curves into cycles easily analyzed using fatigue failure techniques.

However, it must be recognized that in the biological setting the fatigue failure mechanism is "modified" by the presence of remodeling and healing processes in musculoskeletal tissues. This book discusses the complexities associated with fatigue in a biological environment and presents models for understanding how the body strives to maintain musculoskeletal homeostasis through these unique processes. We discuss the potential impact of factors that might impair the healing mechanism (such as psychological stress, obesity and aging) and discuss in detail the dynamic processes of the biological system related to maintaining musculoskeletal health. Recent findings on musculoskeletal epidemiology are provided as well as a detailed overview of the musculoskeletal system.