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The definition of what constitutes impairment is an evolving process, with the most recent attempt ( AMA Guides to the Evaluation of Permanent Impairment , 6th edition, 2008) representing a paradigm shift compared with prior attempts.
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An impairment evaluation is performed once the patient has reached maximum medical benefit.
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Impairment should not be used synonymously with disability.
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The impairment rating requires a comprehensive medical evaluation, which includes a history and physical examination using objective measures.
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The 6th edition Guides now follow the International Classification of Functioning, Disability and Health (ICF) as developed by the World Health Organization (WHO).
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Diagnoses for the upper extremity are now defined in three major categories: soft tissue, muscle–tendon, and ligament–bone–joint . There are now five defined impairment classes, ranging from class 0 (no objective findings and thus no impairment), to class 4 (“very severe” problem with an upper extremity impairment range from 50%–100%).
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The 6th edition does account for inconsistencies during the physical examination, and using the Diagnosis-Based Impairment rating technique, less weight is given to the physical examination and functional status in the setting of significant inconsistencies.
Extent of the Problem
In the United States, disorders of the upper extremities are widespread and cause associated disability and considerable economic consequences. Injuries and arthritic conditions are the most common disorders of the upper extremity, and musculoskeletal problems involving the upper and lower extremity and the spine are the most common cause of work-related disability. As documented by Kelsey and colleagues, approximately 18 million acute upper extremity injuries occur per year, and at any given time, approximately 31 million people have arthritis, many with upper extremity involvement. Twenty-four million visits are made to physicians’ offices each year for upper extremity problems, at a cost of almost $19 billion in 1995. In 2004 the sum of the direct expenditures in health care costs for bone and joint health and the indirect expenditures in lost wages has been estimated to be $849 billion dollars, or 7.7% of the national gross domestic product. In a survey from the National Center for Health Statistics published in 2005, it was reported that chronic joint pain (defined as joint pain lasting longer than 3 months) was reported by 58.9 million adults aged 18 or older (26.4 of 100). These statistics illustrate the current significance of these problems.
Currently, musculoskeletal disorders and diseases are the leading cause of disability in the United States and result in the greatest number of total lost work days in the United States relative to other major medical conditions. For more information, the reader is directed to Jacobs and coworkers’ informative text, The Burden of Musculoskeletal Diseases in the United States. This text is an update of two prior works entitled Musculoskeletal Conditions in the United States published in 1992 and 1999 by the American Academy of Orthopedic Surgeons and is a joint project of the AAOS, American Academy of Physical Medicine and Rehabilitation, American College of Rheumatology, American Society for Bone and Mineral Research, Arthritis Foundation, National University of Health Sciences, Orthopedic Research Society, Scoliosis Research Society, and the United States Bone and Joint Decade. This text is available free of charge online at < www.boneandjointburden.org/ >.
History of Impairment Evaluation
The need for impairment and disability evaluation became apparent with the development of entitlement programs and workers’ compensation awards (private or public programs for the disabled). Evidence indicates that some of these systems existed in ancient times, and in the Middle Ages, merchant and craft guilds organized to protect their members. ,
Many guidelines developed in Europe in the 19th century showed great variability in assigning value to the same impairment because of a lack of established standards. Rating was a conglomerate of many factors, and the physician was in a weak position to defend his opinion because of a lack of definitive criteria. In 1927, Kessler proposed that medical decisions be based on measurable factors. McBride , then developed a complex system of medical measurements in disability evaluation. The first rating system for the American orthopedic surgeon, authored by McBride, was published in 1936 and focused on workers’ compensation laws. It was an attempt to standardize ratings on a more scientific basis. Unfortunately, problems remained because of the degree of subjectivity involved. Slocum and Pratt offered a schedule based on function, which when reviewed today appears rudimentary. In response to the problem of impairment evaluation, the American Medical Association (AMA) appointed a Committee on Medical Rating of Physical Impairment in September of 1956 that was authorized to establish guidelines for a rating system. Kessler and McBride served as consultants on this committee. The first of these Guides was published as a special edition of the Journal of the American Medical Association on February 15, 1958; its three sections covered the upper and lower extremities and the back. The upper extremity section, “a unit of the whole man” was divided into four categories: hand, wrist, elbow, and shoulder. The hand was further subdivided into the five digits and the digits into their respective joints. Impairments were then rated based on loss of motion or ankylosis at the joints or secondary to amputation of a part as assigned by the committee and given on a provided chart. A functional value was derived for the deficit and then applied from the digit to the hand and the hand to the upper extremity and from there onto the whole person.
An attempt to give guidelines for standardization of evaluations done by the orthopedic surgeons also was developed and published in 1962 by the AAOS Committee on Disability Evaluation chaired by McBride. This 30-page pamphlet was intended to standardize orthopedic evaluations. Despite the use of the term disability in the committee’s name, this paper makes it clear that a disability rating is an administrative and not a medical responsibility. This effort was soon superseded by the AMA Guides .
In 1970, Kessler pushed for more objectively obtained measurements. In his volume, published in 1970, he also stressed loss of function over anatomic loss. He refers to the fact that there were varying opinions on the AMA Committee to which he and Dr. McBride consulted.
Subsequent to the first attempt in 1958, the AMA Committee’s scope was broadened, and from 1958 to 1970 it published 13 separate “Guides to the Evaluation of Permanent Impairment” in the Journal of the American Medical Association. A second edition of these guides was published as separate chapters in a single volume in 1971 entitled “Guides to the Evaluation of Permanent Impairment.” These AMA Guides , now in a 6th edition (2008, with updates), are an “attempt to estimate the severity of human impairments based on accepted medical standards.” The concept here is that a loss of function could be translated to a percentage loss of the whole person. Although the Guides are needed, the complexity of issues in impairment evaluation makes them imperfect. This is recognized by most experts, including the framers, who are cautious in their choice of language, stating, “this is an attempt to standardize these evaluation proceedings.” Frequent updates in response to inconsistencies will gradually further improve their utility. The section of the Guides devoted to the upper extremity was updated and developed by Alfred Swanson and coworkers, , and we are indebted for their work in this difficult area. They also have provided the section on impairment evaluation in prior editions of this text. This chapter does not attempt to serve as a substitute for the AMA Guides , but rather as a help to the reader in the application of the Guides , pointing out the pitfalls and adding some opinions on their use.
The Impairment Evaluation
When is an impairment evaluation indicated? Impairment evaluation is not undertaken early, but rather is done after the patient’s condition has stabilized for some time and thus has reached what is known as maximum medical improvement. Impairment, to be evaluated, must be permanent; that is, the patient’s condition should be stabilized and unlikely to change either with time or further treatment. , When performing a rating examination, the rating physician should understand the use of the terms impairment and disability.
Impairment Versus Disability
Impairment is a deviation from normal in a body part and its functioning. It marks the degree to which an individual’s capacity to carry out daily activities has been diminished. Impairment can be determined and thus is a medical decision made with the use of the Guides after a thorough review of the medical history and a medical examination conducted in combination with appropriate laboratory tests and diagnostic procedures. Physical impairment involves an anatomic or physiologic loss that interferes with the subject’s ability to perform a certain function. After evaluation an impairment rating can be assigned. This impairment rating can then be used to determine disability, which is a decrease in, or the loss of, an individual’s capacity to meet personal, social, or occupational demands, or activities that the individual cannot accomplish because of the impairment. Many people exhibit an impairment but with adaptation do not have a disability. An example would be an elevator operator or a surgeon who loses an index finger; although each has a 20% impairment of the hand, he or she has no disability.
It was originally intended that the medically determined impairment rating would be taken to a legal entity, such as a workers’ compensation board or some other administrative body, that would then award the disability rating, but today it appears that these organizations more frequently rely on examining physicians to make the disability determination. This is in spite of the Guides telling us that impairment percentages derived according to Guides criteria should not be used to make direct estimates of disabilities. These impairment examinations are most often performed by physicians who specialize in occupational medicine or disability rating and specialists who, in some states, take a course and are then certified to perform such evaluations. Again, an impaired person is not necessarily disabled, and all impairments do not result in the same degree of disability in all cases. The impairment rating is a medical determination and directly related to the medical status of the individual, whereas disability can be determined only within the context of the personal, social, or occupational demands that the individual is unable to meet as a result of the impairment. Ideally, impairment evaluation should provide only one element of the disability rating.
The Medical Evaluation
The medical evaluation is based on the clinical findings from a physical examination after a detailed history has been obtained. The examiner must recognize that the patient is heavily invested in the result of the examination, which consequently is often adversarial in nature. Despite this, the examiner should always present a neutral demeanor. The complaints and findings should be reasonably relatable to the nature of the injury or condition. The examiner should be cognizant of the difficulties inherent in this evaluation and search for objective findings that will correlate with the subjective symptoms. Psychological overlay, symptom magnification, and possible malingering should be noted and attention called to them in the final report with terms that point out such inconsistencies. These issues should not be confronted at the time of the examination, with the examiner maintaining an impartial attitude. On subjective testing, the experienced and sophisticated patient can present findings that may invalidate the meaning of a particular test.
Medical History
The examination should be preceded by a review of the available records, which the examiner should insist be made available. A detailed history of the present illness is then taken along with the current complaints and the examinee’s reported functional difficulties. In trauma, it is useful to understand the details of the initial injury. This information may help the examiner judge whether the incident is likely to have led to the current complaints. The history of treatment is developed along with the patient’s perceived response to that treatment.
The patient’s health history may be significant because certain medical conditions predispose to or explain certain conditions or symptoms. Prior trauma should be elucidated along with its possible relation to present symptoms. Knowledge of current medications and treatment bring out any concurrent problems. The use of inappropriate medications should be known. For example, the use of narcotics to treat a less than major problem greatly influences that patient’s response and reporting of pain symptoms. In our experience, many of these patients who are on inappropriate narcotics for long periods would ideally benefit from withdrawal of their medication as part of their treatment and before their evaluation. A patient’s social history may indicate a healthy or unhealthy lifestyle and reveal issues that may be adding undue stress to his or her life. A work history often reveals much about the patient. A job that requires heavy manual effort may explain symptoms. Other jobs, in which the worker perceives mental stress, can explain symptoms, the origin of which is otherwise obscure. Diffuse, poorly localized symptoms, vague chronic pain, intolerance of treatment, worsening with every treatment modality, excessive drug use, and poor compliance in treatment should all be noted.
Physical Examination
The physical examination should include the usual elements of a complete physical. Required instruments include a goniometer, a tape measure, and devices that allow measurement of sensation, including Semmes–Weinstein monofilaments and two-point discrimination. It is also helpful to have on hand a Jamar dynamometer and a pinch gauge. A current copy of the Guides is necessary to complete the report generated by the evaluation procedures, and software, in the form of a Guides impairment calculator, is available for purchase from the AMA. We have found this software useful; it can definitely aid in the calculation process.
The appearance of the upper extremity is noted, including obvious deformities, amputations, scars, masses, atrophy of muscles or finger pulps, trophic changes, skin discoloration, or sweat pattern abnormalities. The extremity, especially the hand, is palpated to determine temperature and sweat pattern. Range of motion (ROM) is measured at all joints in the involved area. Limb circumference is measured at specified locations above and below the elbow and compared with measurements of the contralateral limb. A sensory evaluation is carried out using monofilaments and a device that measures static two-point discrimination. All data are recorded on the multitude of forms and outlines available for this purpose. Appropriate imaging studies and neurodiagnostic testing should be reviewed. All of this is collated in a comprehensive report.
It is good discipline to conclude the physical examination with a usable diagnosis that is consistent with the current ICD-9 code. This diagnosis should be responsive to the findings and considered very carefully because it can, to a great degree, become a label that, if inaccurate, is difficult to eradicate. At times a clear-cut diagnosis cannot be made. The use of the nonjudgmental diagnostic code 729.5 for “pain—upper extremity” is an excellent tool when the diagnosis is not confirmable. It is useful for a patient without recognizable objective justification for his or her pain and is superior to assigning arbitrary terms such as “fibromyalgia syndrome, cumulative trauma disorder, or chronic pain syndrome.” , Much confusion is created when patients, reporting wrist pain, are labeled as having “tendonitis” or “tenosynovitis” when, in fact, these easily confirmable inflammatory conditions are not truly present. The use of the 729.5 code then serves to point out the lack of an objective or rational explanation for the symptoms and avoids a confirmatory label that confuses the issues. In such cases, the examiner should give the reasons for the offered opinion in the discussion section of the report. After the examination, the history and measurements and the subsequent diagnosis are then used with the Guides to estimate the impairment, which should be backed by the rationale that went into the rating assignment.
Using the Guides for Evaluation of Upper Extremity Impairment
Chapters 1 and 2 of the Guides deal with general information, definitions, and how to apply the information derived through the Guides . The upper extremity is covered in the section on the musculoskeletal system, Chapter 15 . Substantial changes have been made between the 5th and 6th editions, and it is highly recommended that the reader review all three chapters prior to performing an impairment rating evaluation that will be based on this newest edition to the Guides . The Guides now follow the ICF as developed by the World Health Organization (WHO). The ICF framework is intended for describing as well as measuring health and disability both at the level of the individual and for population levels. Its three components include alteration in body function and body structure, activity limitation, and participation restrictions. The changes made in the 6th edition represent an ongoing evolution and introduces a paradigm shift to the assessment of impairment. Essentially, the Guides have become more diagnosis and functionally based and stress conceptual and methodologic congruity within and between organ system ratings. The reader is strongly encouraged to study the 6th edition, including the introductory chapters as well as the chapter on the upper extremities. A brief overview of the changes follows, but these changes are difficult to fully grasp without a careful study of the new Guides , including the provided examples found in Chapter 15 .
Diagnoses for the upper extremity are now defined in three major categories; soft tissue, muscle–tendon, and ligament–bone–joint , and there are now five defined impairment classes, ranging from class 0 (no objective findings and thus no impairment), to class 4 (very severe problem with an upper extremity impairment range from 50%–100%) ( Table 17-1 ). Most impairment values for the upper limb are now calculated using the diagnosis-based impairment (DBI) method. The impairment class is determined by the diagnosis once maximum medical improvement has been reached. The class can be modified based on non-key factors, such as functional history, physical findings, and clinical studies. Regional grids are now utilized once the diagnosis has been established, which allow the appropriate impairment rating to be determined for any allowable diagnosis, impairment class, and grade. To evaluate functional history, the 6th edition specifies that physicians should include a self-reported orthopedic functional assessment tool as part of the impairment rating examination and recommends the use of the shorter version of the Disabilities of the Arm, Shoulder, and Hand (DASH) Questionnaire, the QuickDASH, for upper limb impairment. The DASH Questionnaire was developed through a cooperative effort of the AAOS, ASSH, AAHS, and the Canadian province of Ontario Institute for Work and Health.
| Impairment Range | |||
|---|---|---|---|
| Class | Problem | Upper Extremity (UEI) (%) | Whole Person (WPI) (%) |
| 0 | No objective findings | 0 | 0 |
| 1 | Mild | 1–13 | 1–8 |
| 2 | Moderate | 14–25 | 8–15 |
| 3 | Severe | 26–49 | 16–29 |
| 4 | Very severe | 50–100 | 30–60 |
Both the DASH and the QuickDASH, which is a subset of DASH questions and which has similar validity, are available at < http://www.dash.iwh.on.ca/outcome_quick.htm >. There is no charge for their use. The result of the QuickDASH should be compared with an activities of daily living questionnaire to evaluate for consistency. Depending on the result, it may or may not be used to modify the default impairment rating. Though it initially seems that the changes are cumbersome, after one reviews the introductory chapters along with the upper extremity chapter, the logic of the changes becomes apparent.
Peripheral nerve impairment is now similarly rated by class based on the nerve involved, along with the level of involvement. Variability within a class depends on the severity of the deficit. Entrapment–compression neuropathy is also rated differently and includes modifiers based on nerve conduction study data, history, physical findings, and functional scale ( Table 17-2 ). Impairment due to amputation has also been modified in the 6th edition, and though largely based on the level of the amputation, the grade can be modified up or down from the default “C” based on other “adjustment factors” ( Table 17-3 ).
| Clinical | Grade Modifier 0 | Grade Modifier 1 | Grade Modifier 2 | Grade Modifier 3 | Grade Modifier 4 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Test findings | Normal | Conduction delay (sensory and/or motor) | Motor conduction block | Axon loss | Almost dead nerve | ||||||
| History | Mild intermittent symptoms | Mild intermittent symptoms | Significant intermittent symptoms | Constant symptoms | NA | ||||||
| Physical findings | Normal | Normal | Decreased sensation | Atrophy or weakness | NA | ||||||
| Functional scale | Normal (0–20) 0 | Normal (0–20) 0 | Mild (21–40) 1 | Mild (21–40) 1 | NA | ||||||
| Mild (21–40) 1 | Mild (21–40) 1 | Moderate (41–60) 2 | Moderate (41–60) 2 | ||||||||
| Moderate (41–60) 2 | Moderate (41–60) 2 | Severe (61–80) 3 | Severe (61–80) 3 | ||||||||
| UE impairment | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | NA |
| Diagnostic Criteria (key factor) | Class 0 | Class 1 | Class 2 | Class 3 | Class 4 | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Impairment Ranges (UE %) | % UE | 1%–13% UE | 14%–25% UE | 26%–49% UE | 50%–100% UE | ||||||||||||||||
| Grade | A | B | C | D | E | A | B | C | D | E | A | B | C | D | E | A | B | C | D | E | |
| Thumb, at: | 18 | 18 | 18 | 20 | 22 | 36 | 36 | 36 | 38 | 40 | |||||||||||
| IP joint | MCP joint | ||||||||||||||||||||
| 37 | 37 | 37 | 39 | 41 | |||||||||||||||||
| Half metacarpal | |||||||||||||||||||||
| 38 | 38 | 38 | 40 | 42 | |||||||||||||||||
| Metacarpal at CMC | |||||||||||||||||||||
| Index or middle finger, at: | 8 | 8 | 8 | 9 | 10 | 14 | 14 | 14 | 16 | 18 | |||||||||||
| DIP joint | PIP joint | ||||||||||||||||||||
| 18 | 18 | 18 | 20 | 22 | |||||||||||||||||
| MCP joint | |||||||||||||||||||||
| 19 | 19 | 19 | 21 | 23 | |||||||||||||||||
| Half metacarpal | |||||||||||||||||||||
| 20 | 20 | 20 | 22 | 24 | |||||||||||||||||
| Metacarpal at CMC | |||||||||||||||||||||
| Ring or little finger, at: | 5 | 5 | 5 | 6 | 7 | ||||||||||||||||
| DIP joint | |||||||||||||||||||||
| 7 | 7 | 7 | 8 | 9 | |||||||||||||||||
| PIP joint | |||||||||||||||||||||
| 9 | 9 | 9 | 10 | 11 | |||||||||||||||||
| MCP joint | |||||||||||||||||||||
| 11 | 11 | 11 | 12 | 13 | |||||||||||||||||
| Half metacarpal | |||||||||||||||||||||
| 12 | 12 | 12 | 13 | 13 | |||||||||||||||||
| Metacarpal at CMC | |||||||||||||||||||||
| Hand, at: | 54 | 54 | 54 | 58 | 58 | ||||||||||||||||
| All fingers at MP joints except thumb | |||||||||||||||||||||
| 90 | 90 | 90 | 92 | 94 | |||||||||||||||||
| All digits at MP joints | |||||||||||||||||||||
| 92 | 92 | 92 | 94 | 96 | |||||||||||||||||
| Distal to biceps insertion to transmetacarpophalangeal loss of all digits | |||||||||||||||||||||
| Arm, at: | 92 | 92 | 92 | 94 | 96 | ||||||||||||||||
| Distal to deltoid insertion to bicipital insertion | |||||||||||||||||||||
| 100 | 100 | 100 | 100 | 100 | |||||||||||||||||
| Deltoid insertion and proximally | |||||||||||||||||||||
| Shoulder, at: | 100 | 100 | 100 | 100 | 100 | ||||||||||||||||
| Shoulder disarticulation | |||||||||||||||||||||
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