Epidemiology

Occupational injuries are both common and expensive. For example, occupational low back pain occurs in 2% of workers per year. In those younger than 45 years, low back pain is the most common cause of disability. Direct costs include medical expenses; indirect costs include lost worker productivity. The total annual direct costs are in excess of $65 billion; indirect costs are more than $106 billion. Occupational injuries and illnesses are insufficiently appreciated contributors to the total burden of health care costs.¹⁸

The largest and most expensive source of injuries is work-related musculoskeletal disorders. A National Academy of Sciences study found that musculoskeletal disorders of the back and arm cause more than 1 million workers to miss time from their job each year, at an annual cost of more than $50 billion.²⁵ When one takes into account such indirect costs as reduced productivity, loss of customers as a result of errors made by replacement workers, and regulatory compliance, the total yearly cost of all workplace injuries is estimated to be well over $1 trillion, or 10% of the U.S. gross domestic product.^23,24,26 A small percentage of injured workers account for a large percentage of costs. For example, 7.4% of cases of absence from work for 6 months in a cohort of occupational back pain claimants accounted for about 70% of lost days, medical costs, and wage replacement costs.¹

History

Occupational health and safety is not a new concept. Many of our common treatments—such as splints, surgery, dressings, and ointments—were referred to in the Edwin Smith papyrus, dating to about 3000 BC. The Code of Hammurabi in Babylon, around 2000 BC, contained clauses dealing with proper handling of injuries, physician fees, and monetary damages for those who harm others.

The Egyptians established the first fully staffed “occupational health clinic” under the guidance of Ramses II in about 1500 BC. To maintain a healthy workforce to build temples and canals, the pharaoh had physician civil servants who regularly examined the workers, enforced hygiene, and isolated the sick. Treatments were further advanced by the Greek physicians Hippocrates and Galen, who documented more environmental hazards. The Romans’ concern over work site dangers prompted them to make many improvements in ventilation, waste disposal, and construction methods.

The basic principles of compensation for injury began in the Middle Ages. The code of King Rothari in 643 clarified a sliding scale of payments for various injuries and disabilities, part of which went to the victim. King Canute specified payments for specific injuries that gave rise to our current impairment guides. For example, the compensation for the loss of a thumb was twice that for the loss of the second digit, and 2.5 times that given for the loss of the third digit. The first monograph dealing with the diseases of a specific occupational group, On the Miners’ Sickness and Other Miners’ Diseases by Paracelsus, was published in 1567.

Many observers in the seventeenth century commented on the diseases of certain workers. In the eighteenth century these observations were published in the first comprehensive treatise on the diseases of workers. Bernardino Ramazzini noted in his Discourse on the Diseases of Workers that workers could be harmed by either “the harmful character of the materials that they handle” or “certain violent and irregular motions and unnatural postures of the body, by reason of which the natural structure of the vital machine is so impaired that serious diseases gradually develop therefrom.” Ramazzini consistently emphasized the link between occupation and health, earning him the title “father of occupational medicine.”

Workers’ compensation acts were passed near the end of the nineteenth century in Germany (1884), Austria (1887), Great Britain (1897), and France (1898). In the United States, the Bureau of Labor Statistics was established in 1869 to study industrial accidents. The Employer’s Liability Law (1877) established the potential for employer liability in workplace accidents. After a long study of the German insurance plan, workers’ compensation legislation was finally passed into law in the United States in 1911. Further concerns over workers’ safety led to the formation of the Occupational Safety and Health Act of 1970.^10,12

Before the current workers’ compensation system, an injured worker’s only recourse against an employer was to sue. Eighty percent of these plaintiff lawsuits were unsuccessful. The injured worker often had, for long periods, no income or medical benefits. Unsuccessful lawsuits often resulted in the worker being fired. On the employer’s side, in the event that the injury suit was successful, there was tremendous unlimited liability. The injured worker had to prove that the injury was the fault of the employer.

The current system in the United States is a no fault system. This means that the injured worker does not need to prove that the employer is at fault, and vice versa. Under the current system, if the injury occurred at work, covered costs include medical expenses and partial payment of lost income. The amount of income covered varies with each state but generally does not replace 100% of the workers’ entire salary or wage. Workers who are required to be off work receive medical treatment for the injury and a portion of their normal wage.

Because workers’ compensation is state run, the rules of coverage vary. Each state can decide for itself how to define a work injury, how cases will be managed, and what benefits are provided. The federal government oversees workers’ compensation only for small specific groups such as railroad workers. This varied approach to injured workers is even more marked in other countries. In economies with a strong social benefit system, such as France, the injured workers do not return to work so quickly. Throughout much of the world, low back pain is considered a normal part of life rather than a severely disabling injury. This approach to low back pain is probably healthier and more cost-effective. Given the same level of back injury, compared with those in other countries, individuals in the United States are more disabled.³⁰

Workers who receive workers’ compensation benefits must forgo their right to sue their employer. The employee still has the right to sue third parties. For example, a truck driver injured in a motor vehicle accident because of a faulty tire can accept workers’ compensation benefits for lost earnings and medical expenses. The worker would not be able to sue the employer (the trucking company) but might still have a product liability case against the tire manufacturer.

Principles

An injury occurs after a specific event can be pinpointed at a particular place and time. This generally refers to minor trauma or a specific lifting injury. An example of an occupational injury would be a nurse’s aide hurting her back while lifting a patient. An occupational illness, on the other hand, comes on gradually. This can occur after repetitive microtrauma and can result in a cumulative trauma disorder such as carpal tunnel syndrome. Cumulative trauma disorder, repetitive motion disorder, and repetitive strain injury are among the terms used to refer to the work-related musculoskeletal disorders associated with occupational illness. Cumulative trauma disorder causation is multifactorial and generally is thought to include diagnoses such as carpal tunnel syndrome and lateral epicondylitis. A cumulative trauma disorder is not a specific medical diagnosis but is a general description. A pathoanatomic diagnosis is often not possible. Compared with other workers’ compensation cases, the mean cost per case of upper limb cumulative trauma disorders is nearly 10 times higher. Sixty percent of new occupational illnesses are associated with repetitive motion.²¹

Although occupational risk factors have been identified, recent literature shows less of a direct causation of overuse syndromes than was previously thought. For example, studies have shown that computer use does not pose a severe occupational hazard for developing symptoms of carpal tunnel syndrome.² Although there are psychologic risk factors for developing symptoms, there appears to be little scientific evidence for the effectiveness of biopsychosocial rehabilitation on repetitive strain injuries.¹⁶

Few high-quality studies of effective injury prevention have been published. One such large-scale, randomized, controlled trial of an educational program to prevent work-associated low back injury found no long-term benefits associated with training.³ Many employers include education regarding lifting techniques in new employee orientation. Nurses with mechanical lifting devices and lifting teams in their workplace are significantly less likely to have a musculoskeletal injury or disorder.^8,13,14,32

Multiple risk factors are known for occupational injury claims. These include smoking, low educational status, job dissatisfaction, lower socioeconomic status, deconditioning, and previous history of injuries or disabilities. Other physical risk factors include repetitive motion, improper positioning, forceful movement, contact stresses, whole body vibration, cold temperatures, and unaccustomed work. It is less well known how altering these risk factors will affect injury rates.²⁵ Workers with the greatest physical work requirements and those with the shortest duration of employment are at the highest risk of back injuries.¹¹

Improving one’s flexibility, strength, and aerobic fitness reduces pain, improves sleep, and improves workplace functioning. A review of controlled trials looking at education, lumbar supports, exercises, ergonomics, and risk factor modification found that only exercise demonstrated sufficient evidence of back or neck pain prevention.^19,33 A cohort study suggested that correct dynamic trunk extension performance can protect against back-related permanent work disability.²⁹

Musculoskeletal fitness is a vital component of the overall health-related fitness equation that has not been fully appreciated. Achieving an adequate level of muscle strength and flexibility enhances dynamic joint stabilization. Joint stabilization helps prevent excessive load transmission across joints and reduces the abnormal movement patterns that can predispose one to injury.¹⁵

Personal modifiable factors are major influences in the recovery from work-related disorders. A relationship exists between subjective well-being and work ability in the general population. Life dissatisfaction predicts subsequent work disability, especially among the physically healthy.¹⁷ Factors associated with better recovery include exercise or physical activity outside work and lower stress levels. Factors associated with higher disability levels over time are cigarette smoking and bed rest.²⁸ Although risk factors for developing occupational disability have been identified, overall there has been low predictive power of such regression models.²⁷

Risk factors for delayed recovery have been identified and have been called yellow flags. Identifying yellow flags in individuals and using aggressive case management with them can be helpful in reducing workers’ compensation costs. Focusing on reducing the perception of disability at the time of injury is critical to preventing time loss.³¹ Non–return to work is associated with higher psychosocial morbidity.²⁰ The doctor’s proactive communication regarding return to work can improve outcomes. According to a prospective study on doctor–patient communication, during the subacute or chronic phase (>30 days of disability), a 60% higher return to work rate was achieved from a positive return to work recommendation.⁴

One conceptual model to improve functional outcomes in occupational injuries (and reduce costs) is called BICEPS. This acronym stands for brevity, immediacy, centrality, expectancy, proximity, and simplicity.

Evaluations

Job descriptions are generally available for each injured worker and should be reviewed to help identify whether that person can return to his or her regular job. Job site analyses done by ergonomists and occupational therapists can help to evaluate whether a worker can perform the particular job safely. These analyses can also help determine whether job modifications are needed to permit the worker to perform the job safely. Ergonomics refers to the study of how the human body interacts with the environment. Certain physical arrangements increase work-related musculoskeletal disorders. Ergonomists are experts in making modifications and suggestions to reduce the risks of injury (Figures 45-1 and 45-2).

FIGURE 45-1 Demonstration of improper lifting technique. Note her straight knees and flexed spine.

FIGURE 45-2 Demonstration of proper lifting technique. Note that she flexed her knees, not her spine.

Preplacement evaluations can be helpful in finding work for an individual who has a higher than average risk for injury. Such persons should not be placed in a job that is known to have a high injury rate. Many employers, such as automotive manufacturers, perform median nerve conduction studies on new hires. These tests are considered a baseline and can be used for comparison purposes later if the employees develop carpal tunnel symptoms.

Functional baseline testing (human performance evaluations) can be done to clarify the individual’s physical ability and to help guide safe job placement. The testing is less extensive than a functional capacity evaluation (FCE; see later explanation) and does not include consistency and validity testing.

Restricted duty allows the injured worker to maintain current function and employment without risking further injury. This is often a better option than being off work. The Department of Labor has published a book called the Dictionary of Occupational Titles³⁴ that clarifies categories of work. They are as follow: sedentary, light, medium, heavy, and very heavy. The occasional maximal lifting that corresponds to each of these is 10 lb, 20 lb, 50 lb, 100 lb, and more than 100 lb, respectively (Tables 45-1 and 45-2).

Table 45-1 Material Handling Limits

Modified from U.S. Department of Labor: Dictionary of occupational titles, Washington, DC, 1986, U.S. Government Printing Office, with permission of the U.S. Government Printing Office.

Independent Medical Examinations

Independent medical examinations (IMEs) are sometimes required in workers’ compensation cases. An IME involves an independent review of a complex medical case. An IME can clarify controversies regarding causation, maximal medical improvement (MMI), work restrictions, impairments, and disability. An IME combines a thorough review of all available medical records and tests with an extensive history and physical examination. An IME does not establish a doctor–patient relationship. IMEs should not be done by any physician with a treatment role with the patient. Although the diagnosis and recommendations sections of the IME report are often detailed, no treatment is ordered by the examining physician. The IME report’s concluding remarks should be stated in layman’s language with as little medical jargon as possible because the reader of these reports is typically an insurance adjuster or an attorney. The most useful IMEs are thorough, unbiased, clear, and legally defensible.

Treatment

Case Closure

Case closure is considered by employers, insurers, and case managers to be the ultimate goal for any workers’ compensation case. Although case closure is important, there should be other goals as well. The goals and incentives are somewhat different for each stakeholder. The physician would like injured workers to be either fully recovered or independent in their functioning. The employer would like workers to return to their job or to another job within the company. The case manager and insurer have an incentive to return injured workers as soon as is safely possible to their maximal level of functioning. Injured workers need to put the injury behind them as quickly as possible and move on.

Workers’ compensation cases ultimately end at the point after which minimal change over the course of the following year is expected. Maximal medical improvement is attained once the medical condition has resolved or has become fixed and stable (also known as permanent and stationary). At this point, further diagnostic testing and intervention are not recommended. At MMI, the injured worker is not expected to significantly change in pain level or functional ability in the near future.

A permanent partial impairment (PPI) rating might be appropriate once the point of MMI has been attained. The PPI rating is designed to compensate the individual for any future lost earnings as a result of their residual dysfunction after the work-related injury. If there was a preexisting condition, an adjustment or apportionment might be needed (Table 45-3). The most widely accepted methodology for evaluating impairment is the AMA Guides to the Evaluation of Permanent Impairment, published by the American Medical Association. It is updated periodically and is currently in its sixth edition. Several states require its use in PPI determinations, whereas other states allow or require the use of other editions or their own state guide.

Table 45-3 Terminology of Apportionment

Modified from Demeter SL, Andersson GBJ, editors: Disability evaluation, ed 2, St Louis, 2003, Mosby, with permission.

A number of tools can be used for measuring impairments. Goniometry measures joint angle and documents restricted range of motion. Dynamometry measures such voluntary forces as grip strength. Validity tests can be used to measure the consistency of grip strength testing with a dynamometer (most commonly the Jamar dynamometer). Inclinometry can be used to measure the range of motion in the cervical, thoracic, and lumbar spine. Specific techniques and normal values are illustrated in the AMA Guides.

Work conditioning might be needed after a prolonged period of decreased activity to increase the injured worker’s strength and cardiovascular fitness. Work conditioning prepares the worker for return to full employment but is not tailored toward a particular job. Work hardening also improves strength, conditioning, flexibility, and overall functional ability by preparing a particular worker for a specific job. Job matching is used to select specific jobs for particular workers with unique abilities.

Functional Capacity Evaluations

Functional capacity evaluations are extensive and formalized physical and occupational testing. FCEs are done by specially trained physical and occupational therapists. These evaluations last anywhere from 4 hours to 2 days. They assess many aspects of the person’s functioning. FCEs emphasize validity and consistency, overall functional ability, and the ability to perform a particular type of employment. The FCE often can guide or clarify what Dictionary of Occupational Titles category job the injured worker can perform. FCE testing is helpful in documenting inconsistencies, decreased effort, and lack of validity on repeat testing (Figures 45-3 to 45-10).

FIGURE 45-3 Operating a dolly up a ramp.

FIGURE 45-4 Sustained overhead work activities.

FIGURE 45-5 Testing fine motor skills.

FIGURE 45-6 Measuring tolerance to weighted pushing activity.

FIGURE 45-7 Testing weighted low carry ability.

FIGURE 45-8 Testing weighted high carry ability.

FIGURE 45-9 Testing weighted stair climb carry.

FIGURE 45-10 Testing functional work activities.

Medicolegal Aspects of Occupational Rehabilitation

Workers’ compensation involves an interaction between the medical and legal systems. Physiatrists are often thrown into this environment; it is helpful to learn some basics of the legal system to practice more effectively. A few of these critical legal concepts are detailed in the next sections.

Future Role of the Physical Medicine and Rehabilitation Physician

The future of physiatrists in occupational rehabilitation is bright. The quality, availability, and variety of educational and training programs in occupational rehabilitation are expanding. A high level of interest in occupational rehabilitation exists among a growing number of “outpatient” physiatrists. Because of their extensive training in teamwork and musculoskeletal evaluations, physiatrists are well positioned to be future leaders of occupational rehabilitation. The growing emphasis on evidence-based medicine provides opportunities for basic and clinical research in improving rehabilitation of the injured worker.