July 1995 Bulletin

New look at repetitive motion disorders

Book reviews underlying causes and other issues

Repetitive motion disorders, also commonly known as cumulative trauma disorders or repetitive strain injuries, are among the fastest growing occupational injuries in the United States, accounting for 60 percent (302,000) of the 1993 workplace illnesses reported by the Bureau of Labor. Carpal tunnel syndrome is said to be one of the most common diagnoses for workers' compensation claims in the United States.

The disorders are the subject of a growing body of scientific literature as basic and clinical scientists attempt to understand the causes and effective treatments. A new Academy book, Repetitive Motion Disorders of the Upper Extremity, covers the epidemiologic and psychologic laboratory studies as well as clinical issues of the subject.

Importantly, the publication also reviews the pathophysiology of the tissues, muscle, nerve and biomechanical loads underlying the disorders, said co-editor Stephen L. Gordon, PhD, chief, musculoskeletal branch, National Institute of Arthritis and Musculoskeletal Diseases (NIAMS). Other editors of the book are Sidney J. Blair, MD, FACS, professor emeritus, department of orthopaedic surgery, Loyola University Medical Center, Maywood, Ill.; and Lawrence J. Fine, MD, DrPH, director, division of surveillance, hazard evaluations and field studies, National Institute for Occupational Safety and Health (NIOSH). The book is based on manuscripts and discussions associated with a workshop organized by NIAMSand held June 20-22, 1994.

"It is the first time that the underlying causes, the pathophysiology, are reviewed in the same context as the overall subject of repetitive motion, per se," Dr. Gordon said.

The book also discusses areas for future research and has a "Dear Doctor" section offering answers to six clinical questions that a physician might be asked by a lay person.

Underlying cause

"Although some individuals believe that the underlying issue may be improper reporting or false claims of a medical problem, the organizers and most of the participants believe that for the vast majority of cases, there is an underlying physiologic insult to one or more of the various tissues involved," said Dr. Gordon.

The book opens with a look at the epidemiological studies and psychosocial factors, followed by discussions of subjects such as the dynamic effects of work on musculoskeletal loading; the biomechanics of soft tissue: normal, injured, and healed states; effects of loading on metabolism and repair of tendons and ligaments and pathophysiology of nerve compression.

The section on clinical issues was written more from the perspective of what to do, not how to do it, Dr. Gordon said.

Studies nonconclusive

Although the media and general public associate carpal tunnel syndrome with the workplace, Robert M. Szabo, MD, professor of orthopaedic surgery, chief, hand and upper extremity service, and Michael Madison, MD, department of orthopaedic surgery, both of the University of California, Davis, say the evidence is inconclusive. They point out that various studies have produced conflicting findings supporting the concept that carpal tunnel syndrome is a work-related disorder.

They examined intrinsic and extrinsic risk factors contributing to a clinical case of carpal tunnel syndrome, pointing out that qualitative understanding of intrinsic factors and their relationship to exposure to extrinsic factors at work is very imperfect. "There is a fundamental incompatibility between the epidemiologic perspective and the clinician's perspective, with the result that even very compelling epidemiologic data is of only limited use to the clinician," they said.

"It is unfortunate that workers' compensation determinations must be made in individual clinical cases, where it is impossible to quantify the contribution of the job to the clinical problem. The proper arena for workers' compensation issues with regard to carpal tunnel syndrome and similar contributions is at the statistical level, where surveillance, intervention, and regulation can be carried out in a meaningful way."

They conclude that "workers with physically demanding jobs should undergo careful screening to disqualify those with unacceptable intrinsic risk factors, and a program of continuing physical conditioning should be required. In addition, it should be recognized that after 10 to 20 years, a worker should be transferred to a less demanding task. The belief that any worker can do any job until age 65, which is a premise of much workers' compensation policy and labor union rhetoric, is not realistic."

The book is priced at $85 for members and $105 for nonmembers. To order, call the Academy's customer service department, (800) 626-6726.

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