The American Medical Association Guides to the Evaluation of Permanent Impairment (6th edition) defines "impairment as a significant deviation, loss, or loss of use of any body structure or bodily function in an individual with a health condition, disorder, or disease."
An impairment affects an individual's health status, and is therefore a medical issue to be assessed by a qualified medical professional. Impairments resulting from a given health condition reflect an individual's limitation in performing Activities of Daily Living (ADLs).
Specifically, ADLs are a series of basic activities performed daily by individuals that are necessary for independent living. They include:
Self-care, such as bathing, grooming, and oral care
Communication, such as speaking, reading, and writing
Physical activity, such as standing, sitting, walking, carrying, and climbing
Sensory function, such as hearing, seeing, smelling
Hand functions, such as grasping, holding, and pinching
Travel, such as driving and traveling by car or train
Sexual function: participating in desired sexual activity
Sleep: having a restful sleep pattern
Social and recreational activities: participating in individual or group activities, sports, or hobbies
In contrast, according to the Guides, disability is defined "as activity limitations and/or participation restrictions in an individual with a health condition, disorder, or disease."
In other words, because of impairment, a disabled individual has decreased capacity to meet social or occupational demands and/or is not capable of participation in all the activities they want to or were previously capable of participating in.
A disability arises from the interaction between impairment and external requirements, especially those of a person's occupation. In workers' compensation cases, the level of disability and amount of work time loss is based on the severity and nature of functional impairment caused by the injury. Disability cases cause workers' frustration and loss of wages and a substantial financial burden for employers and workers' compensation organizations.
There are various degrees of disabilities:
● Temporary total disability indicates that the injured employee is incapable of returning to any work or earning wages during a specified period after injury. Most workers' compensation claims involve a temporary total disability.
● Temporary partial disability indicates that the injured cannot do the same job he/she was doing at the time of the injury but can return to work in a modified capacity. As a result, the employee may be incapable of earning his/her pre-injury wages.
● Permanent total disability means that the employee is medically determined to be permanently incapable of returning to work. It may result from a spinal cord injury with paralysis, severe brain injury, or limb amputations.
● Permanent partial disability means that an injured worker, when reached MMI, is assessed to have permanently lost one or several functions. The employee can no longer perform work at his/her pre-injury level but is capable of modified duty or alternative work. Permanent partial disability is the most common category of disability benefit payment. Compensation is based on determining the percentage of impairment of the whole person at the time of MMI using AMA Guides.
Interrelation between impairment and disability and return to work
The Guides emphasize that there is not necessarily a direct correlation between impairment and disability. It states that "The relationship between impairment and disability remains both complex and difficult, if not impossible to predict. In some conditions there is a strong association between level of injury and the degree of functional loss expected in one's personal sphere of activity (mobility and ADLs). The same level of injury is in no way predictive of an affected individual's ability to participate in major life functions (including work) when appropriate motivation, technologies, and sufficient accommodations are available."
A given physical impairment can be highly disabling in one vocational context and virtually non-disabling in another. For example, cervical radiculopathy resulting in the weakness of the right upper extremity might preclude the vocation of a surgeon. In contrast, the same situation might be of no functional consequence for a teacher with some necessary job accommodations.
The limited degree of correlation between impairment and disability has a strong implication for the return to work of the injured worker. To make an effective return-to-work decision, a healthcare provider first needs to understand the specific work-related physical demands of the injured worker. These demands are physical abilities required to perform work tasks successfully. These include work postures, body movements, the level of force or strength the worker applies to job tasks, repetition of the work tasks, and other work factors.
By matching the worker's residual functional capacity from the identified impairments with their job's physical demands, a healthcare provider then determines if they can safely perform their specific job functions. This process indeed becomes much easier when the worker is motivated to resume their work and the employer is willing to provide the job accommodations if necessary.
The critical point is recognizing that an individual with impairment may not necessarily have a disability. Therefore, a successful return to work in these cases can help prevent unwarranted time loss, prolonged absence from work, and propagation of a disability mindset in the long run.
The table below summarizes the important characteristics of disability and impairment:
Disability Impairment
Economic issue Medical issue
Focus on financial loss Focus on functional loss
Loss of capacity for personal/social demands Loss capacity to perform ADLs
Temporary or permanent, total or partial Temporary or permanent
Disability associated with impairment Impairment may not be with disability
American Medical Association. (2008). Guides to the evaluation of permanent impairment (6th ed.). Chicago: AMA Press.
Novick AK, Rondinelli RD: Impairment and Disability under Workers’ Compensation: Robert Rondinelli and Richard Katz (eds): In: Impairment Rating and Disability Evaluation. Philadelphia, W.B. Saunders Company, 2000; 141-156.
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