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Guides to the Evaluation of Permanent Impairment, fourth edition 4th Edition, (Ebook PDF)
*Table 1-5 Generic Template for Impairment Classification Grids
Table 1-6 General Principles and Rules for Calculating Impairment
CHAPTER 2
Table 4-3 Energy Expenditure in METs During Bicycle Ergometry . . .
Table 4-4 Methodology for Determining the Grade in an Impairment Class . . .
.7
.8
.11
.11
.14
*Table 4-5 Criteria for Rating Permanent Impairment due to Valvular Heart Disease
*Table 4-6 Criteria for Rating Impairment due to Coronary Artery Disease
*Table 4-7 Criteria for Rating Impairment due to Cardiomyopathies
*Table 4-8 Criteria for Rating Impairment due to Pericardial Heart Disease
.49
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*Table 4-9 Criteria for Rating Permanent Impairment due to Dysrhythmias . . . .64
Table 4-10 Classification of Blood Pressure for Adults
Practical Application of the Guides 19
Table 2-1 Fundamental Principles of the Guides .
CHAPTER 3
.20
Pain-Related Impairment 31
*Table 3-1 Pain-Related Impairment and Whole Person Impairment Based on Pain Disability Questionnaire
CHAPTER 4 The Cardiovascular System
Table 4-1 NYHA Functional Classification of Cardiac Disease.
Table 4-2 Relationship of METs and Functional Class According to 5 Treadmill Protocols .
.66
*Table 4-11 Criteria for Rating Impairment due to Hypertensive Cardiovascular Disease
.67
*Table 4-12 Criteria for Rating Impairment due to Peripheral Vascular Disease – Lower Extremity
.69
*Table 4-13 Criteria for Rating Impairment due to Peripheral Vascular Disease – Upper Extremity
.70
*Table 4-14 Criteria for Rating Impairment due to Diseases of the Pulmonary Artery . . . .72
Table 4-15 Cardiac Impairment Evaluation Summary
CHAPTER 5
.74
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The Pulmonary System 77
Table 5-1 Impairment Classification of Dyspnea (Adapted) .
Table 5-2 Impairment Classification for Prolonged Physical Work Intensity by Oxygen Consumption
.79
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Table 5-3 Methodology for Determining the Grade in an Impairment Class . . . . . . .86
*Table 5-4 Criteria for Rating Permanent Impairment due to Pulmonary Dysfunctiona
*Table 5-5 Criteria for Rating Permanent Impairment due to Asthma
Table 5-6 Scale for Judging Capabilities of Subjects With Cancer
Table 5-7 Pulmonary Impairment Evaluation Summary
CHAPTER 6
Digestive System
Table 6-1 Desirable Weights for Men by Height and Body Build
Table 6-2 Desirable Weights for Women by Height and Body Build
Table 6-3 Methodology for Determining the Grade in an Impairment Class . .
*Table 6-4 Criteria for Rating Permanent Impairment due to Upper Digestive Tract (Esophagus, Stomach and Duodenum, Small Intestine, and Pancreas) Disease
*Table 6-5 Criteria for Rating Permanent Impairment due to Colonic and Rectal Disorders
*Table 6-6 Criteria for Rating Permanent Impairment due to Anal Disease .
Table 6-7 Impairments From Surgically Created Stomas
*Table 6-8 Criteria for Rating Permanent Impairment due to Liver Disease
*Table 6-9 Criteria for Rating Permanent Impairment due to Biliary Tract Disease
*Table 6-10 Criteria for Rating Permanent Impairment due to Herniation .
Table 6-11 Digestive System Impairment Evaluation Summary
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*Table 7-3 Criteria for Rating Permanent Impairment due to Urinary Diversion Disorders .
*Table 7-4 Criteria for Rating Permanent Impairment due to Bladder Disease
*Table 7-5 Criteria for Rating Permanent Impairment due to Urethral Disease .
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.139
.141
*Table 7-6 Criteria for Rating Permanent Impairment due to Penile Disease . . .144
*Table 7-7 Criteria for Rating Permanent Impairment due to Scrotal Disease
*Table 7-8 Criteria for Rating Impairment due to Testicular, Epididymal, and Spermatic Cord Disease
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.147
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CHAPTER 7
The Urinary and Reproductive Systems 129
Table 7-1 Methodology for Determining the Grade in an Impairment Class
*Table 7-2 Criteria for Rating Permanent Impairment due to Upper Urinary Tract Disease.
.130
.134
*Table 7-9 Criteria for Rating Impairment due to Prostate Disease
*Table 7-10 Criteria for Rating Permanent Impairment due to Vulval and Vaginal Disease
*Table 7-11 Criteria for Rating Permanent Impairment due to Cervical and Uterine Disease
*Table 7-12 Criteria for Rating Permanent Impairment due to Fallopian Tube and Ovarian Disease
Table 7-13 Urinary and Reproductive Systems Impairment Evaluation Summary
.149
.152
.154
CHAPTER 8
Table 8-1 Structure, Functions, and Disorders of the Skin
.160
*Table 8-2 Criteria for Rating Permanent Impairment due to Skin Disorders . . .166
Table 8-3 Skin Impairment Evaluation Summary
CHAPTER 9
Table 9-1 Karnofsky Performance Status Scale Definitions Rating (%) Criteria
Table 9-2 Eastern Cooperative Oncology Group Performance Status Scale (ECOG-PSS)
Table 9-3 Burden of Treatment Compliance . . .186
Table 9-4 Methodology for Determining the Grade in an Impairment Class . . . . . .187
*Table 9-5 Criteria for Rating Permanent Impairment due to Anemia .
.189
*Table 9-6 Criteria for Rating Permanent Impairment due to Neutropenia . . . .194
*Table 9-7 Criteria for Rating Permanent Impairment due to the Leukemias . . .196
*Table 9-8 Criteria for Rating Permanent Impairment due to HIV Disease . . . . .199
*Table 9-9 Criteria for Rating Impairment due to Platelet Disorders
*Table 9-10 Criteria for Rating Impairment due to the Hemophilias
*Table 9-11 Criteria for Rating Impairment due to Other Bleeding Disorders
*Table 9-12 Criteria for Rating Impairment due to Thrombotic Disorders
*Table 9-13 Criteria for Rating Impairment due to Lymphoma and Metastatic Disease
Figure 12-6 Effect of Nasal Field Loss on the Binocular Field .
Figure 12-7 Effect of Temporal Field Loss on the Binocular Field
Figure 12-8 Conversion From VSI to WPI .
Figure 12-9 Evaluation of Permanent Visual Impairment
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Figure 12-10 Overlay Grid for Goldmann Fields . . .315
Figure 12-11 Overlay Grids for Humphrey Field Plots
CHAPTER 15
The Upper Extremities
Figure 15-1 Upper Extremity Regions
Figure 15-2 Upper Extremity Impairment Evaluation
Figure 15-3 Techniques for Measuring the Scaphoid, Lunate Axis, and Long Axis of the Radius and Corresponding Angles .
Figure 15-4 Digit Impairment due to Thumb Amputation at Various Lengths or Total Transverse Sensory Loss . .
.409
.426
Figure 15-5 Digit Impairment due to Finger Amputation at Various Lengths or Total Transverse Sensory Loss . . . . . .426
Figure 15-6 Hand Impairment Values for Total Transverse Sensory Loss and Total Longitudinal Sensory Loss on Radial and Ulnar Sides Involving 100 % of the Digit Length.
Figure 15-7 Motor Innervation of the Upper Extremity
Figure 15-8 Cutaneous Innervation of the Upper Extremity and Related Peripheral Nerves and Roots
. .428
.432
.432
Figure 15-9 Impairment Estimates for Upper Extremity Amputation at Various Levels
Figure 15-10 Impairments of the Digits and the Hand for Amputation at Various Levels
Figure 15-11 Digit Impairment Percent for Thumb Amputation at Various Levels
.456
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Figure 15-12 Digit Impairment Percent for Finger Amputation at Various Levels . . . . . .458
Figure 15-13 Upper Extremity Range of Motion Record
Figure 15-14 Measurement of MCP Joint Position in Flexion, Extension Lag, Full Extension, and Hyperextension . .
Figure 15-15 Neutral Position and Flexion of Thumb IP Joint
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. .466
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Figure 15-16 Flexion of Thumb MCP Joint . . . . . . .467
Figure 15-17 Neutral Position of Thumb MCP Joint
.467
Figure 15-18 Thumb Radial Abduction, Measuring the Angle of Separation Formed Between First and Second Metacarpals in Coronal Plane . . . . . .467
Figure 15-19 Adduction of Thumb
Figure 15-20 Linear Measurements of Thumb Opposition (cm) at Various Positions
Figure 15-21 Neutral Position and Flexion of Finger DIP Joint
Figure 15-22 Neutral Position and Flexion of Finger PIP Joint
Figure 15-23 Neutral Position and Flexion of Finger MCP Joint.
Figure 15-24 Wrist Flexion and Extension
Figure 15-25 Radial Deviation and Ulnar Deviation of the Right Wrist
Figure 15-26 Flexion and Extension of Elbow
Figure 15-27 Pronation and Supination of Forearm
Figure 15-28 Shoulder Flexion and Extension.
Figure 15-29 Shoulder Abduction and Adduction
Figure 15-30 Shoulder External Rotation and Internal Rotation
Figure 15-31 Upper Extremity Impairment Evaluation Example .
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CHAPTER 16
The Lower Extremities 493
Figure 16-1 Lower Extremity Regions.
Figure 16-2 Lower Extremity Impairment Evaluation Record .
Figure 16-3 Sensory Nerves of the Lower Extremity . .
Figure 16-4 Motor Nerves of the Lower Extremity
Figure 16-5 Evaluating the Range of Motion of a Toe: The Metatarsophalangeal (MTP) Joint of the Great Toe
.494
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.537
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.545
Figure 16-6 Measuring Inversion and Eversion . . .546
Figure 16-7 Measuring Ankle Dorsiflexion (Extension) and Plantar Flexion
Figure 16-8 Measuring Knee Flexion
Figure 16-9 Using a Goniometer to Measure Flexion of the Right Hip
Figure 16-10 Neutral Position, Abduction, and Adduction of Right Hip
Figure 16-11 Measuring Internal and External Hip Rotation
Figure 16-12 Lower Extremity Range of Motion Record
Figure 16-13 Lower Extremity Impairment Evaluation Record Example .
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CHAPTER 17
The Spine and Pelvis
Figure 17-1 Spine and Pelvis Regions
Figure 17-2 Spine and Pelvis Impairment Evaluation Record
Figure 17-3 Skin Areas Innervated by Cervical and Thoracic Nerve Roots Showing Autonomous Zones
Figure 17-4 Skin Areas Innervated by Thoracic and Lumbosacral Nerve Roots and Showing Autonomous Zones
Figure 17-5 Loss of Motion Segment Integrity, Translation
Figure 17-6 Loss of Motion Segment Integrity, Angular Motion (Sagittal Rotation), Lumbar Spine
Figure 17-7 Spine and Pelvis Evaluation Record Example
Figure 17-A Pain Disability Questionnaire
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Conceptual Foundations and Philosophy
1.1 History of the Guides
1.2 New Directions for the Sixth Edition
1.3 The International Classification of Functioning, Disability, and Health (ICF): A Contemporary Model of Disablement
1.4 Measurement Issues
1.5 Balancing Science and Clinical Judgment
1.6 The Case for Simplification and Ease of Application
1.7 The Application of Functional Assessment
1.8 The Need for Internal Consistency and a Uniform Template
1.9 Summary
1.1 History of the Guides
Tolerance of and care for the sick and the disabled may be elemental components of our social fabric rooted in the very origins of human society. Anthropological evidence supports the notion that our earliest ancestors were afforded communal benefits in terms of improved odds of survival of hereditary and physical impairments that might otherwise prove fatal to the individual.1 The concept of compensation for personal injuries and resulting disabilities is hardly a contemporary one; historical evidence documents that social justice and compensation systems for injured parties have been around since recorded history.1,2
Since antiquity, from ancient Babylonian societies 4000 years ago to the Roman Empire many centuries later, lawgivers attempted to legislate justice in moral, social and economic spheres, which inter alia provided for pecuniary compensation.3 These various attempts to legislate monetary compensation for personal injuries were aimed at ridding the society of the blood feud and replacing it with a more civilized and enlightened system involving the exchange of monetary value for losses resulting from personal injuries. For example, the Lombard laws 2 millennia
ago set forth monetary compensation values for all sorts of injuries, from minor loss such as teeth to the loss of eye and limbs. These systems even accounted for cosmetic loss, doubling the value of a lost tooth if it showed on smile.4 Such monetary compensation schemes, in terms of their whole person values, are strikingly similar to some of our contemporary systems of compensation for disablement.
The Guides reflects experience with impairment ratings over the centuries1,2 and started in 1958 with publication by the American Medical Association (AMA) of the article, A Guide to the Evaluation of Permanent Impairment of the Extremities and Back.5 Over the next 12 years, 12 additional guides appeared in JAMA, and in 1971 a compendium of these 13 guides became the First Edition of the Guides.6
The Guides is revised periodically to incorporate current scientific clinical knowledge and judgment. For example, the Third Edition, published in 1988, introduced pie charts for range of motion (ROM) impairment evaluation of the upper extremities.7 In 1993 the Fourth Edition introduced the DiagnosisRelated Estimates (DRE) or “injury” model to the evaluation of spinal injuries.8 A pain chapter was introduced in the Fourth Edition and refined in the Fifth Edition in 2000.9 The Fifth Edition modified the DRE method and expanded the ROM method for spinal impairment evaluations. The Sixth Edition represents this continued evolution and introduces a “paradigm shift” to the assessment of impairment.
1.2 New Directions for the Sixth Edition
1.2a Previous Criticisms of the Guides
The Guides is revised to reflect the latest scientific research and evolving medical evidence. Earlier versions of the Guides were subject to criticisms,10–17 which included the following:
• There was a failure to provide a comprehensive, valid, reliable, unbiased, and evidence-based rating system.
• Impairment ratings did not adequately or accurately reflect loss of function.
• Numerical ratings were more the representation of “legal fiction than medical reality.”17
Recommended changes included:
• Standardized assessment of Activities of Daily Living (ADL) limitations associated with physical impairments.
• Application of functional assessment tools to validate impairment rating scales.
• Include measures of functional loss in the impairment rating.
• Overall improvements in intrarater and interrater reliability and internal consistency.14
Although attempts were made to correct these deficiencies in the Fifth Edition, problems persisted. These were attributable, in part, to adherence to antiquated and confusing terminology, limited validity and reliability of the ratings, lack of meaningful and consistent application of functional assessment tools, and lack of internal consistency.14 A high error rate among all ratings has been reported.18 In this edition there is a paradigm shift, which adopts a contemporary model of disablement; it is simplified, functionally based, and internally consistent to the fullest extent possible.
1.2b Five New Axioms of the Sixth Edition
The vision embodied by this paradigm shift is articulated in terms of 5 specific new axioms. These axioms provide direction and define priorities:
1. The Guides adopts the terminology and conceptual framework of disablement as put forward by the International Classification of Functioning, Disability, and Health (ICF).19
2. The Guides becomes more diagnosis based with these diagnoses being evidence-based when possible.
3. Simplicity, ease-of-application, and following precedent, where applicable, are given high priority, with the goal of optimizing interrater and intrarater reliability.
4. Rating percentages derived according to the Guides are functionally based, to the fullest practical extent possible.
5. The Guides stresses conceptual and methodological congruity within and between organ system ratings.
1.3 The International Classification of Functioning, Disability, and Health (ICF): A Contemporary Model of Disablement
1.3a
ICF Model
The World Health Organization (WHO) developed a comprehensive model of disablement, the International Classification of Functioning, Disability, and Health (ICF)19; this classification is depicted in Figure 1-1. The ICF framework is intended for describing and measuring health and disability at the individual and population levels. It consists of 3 key components:
1. Body functions and body structures: physiological functions and body parts, respectively; these can vary from the normal state, in terms of loss or deviations, which are referred to as impairments.
2. Activity: task execution by the individual and activity limitations are difficulties the individual may experience carrying out such activities.
3. Participation: involvement in life situations and participation restrictions are barriers to experiencing such involvement.
These components comprise functioning and disability in the model. In turn, they are related interactively to an individual with a given health condition, disorder, or disease, and to environmental factors and personal factors of each specific case.19
1.3b Applications of ICF Model to the Guides
Advantages
of ICF Model
The ICF model appears to be the best model for the Guides. It acknowledges the complex and dynamic interactions between an individual with a given health condition, the environment, and personal factors. The relationships between impairment, activity limitations, and participation are not assumed to be linear or unidirectional. An individual may experience measurable impairment without significant activity limitations that do not produce restrictions to major life activities such as work or recreation. On the other hand, one can experience significant activity limitations and/or participation restrictions in the absence of demonstrable impairment.
ICF Model of Disablement
FIGURE 1-1
History of Models of Disablement
The traditional model of disablement was based on the International Classification of Impairments, Disabilities, and Handicaps (ICIDH) that the WHO presented more than a quarter century ago.20 This model, depicted in Figure 1-2, focuses on the individual and extends across 4 levels of disablement in linear fashion. The first level, pathology (a disease or trauma at the tissue level), is viewed as giving rise to impairment (an abnormality in anatomic or physiological structure or function at the organ system level). This, in turn, gives rise to disability (the functional consequences to the individual in terms of abilities lost) within one’s personal sphere (ie, mobility; Activities of Daily Living, or ADLs); and eventually to handicap (a disadvantage to a given individual in terms of role fulfillment) in their societal sphere (may include barriers or impediments to functioning in a major life activity, such as work).14
The ICIDH model is overly simplistic and unidirectional. This unidirectional depiction of the relationships among impairments, disabilities, and handicaps implies causation and irreversibility; disabilities and handicaps can also give rise to impairments. The ICIDH model also lacks sufficient complexity to fully account for important environmental modifiers of a biological, psychological, and social nature.15 For example, the societal consequences of impairment may be substantially mitigated by environmental accommodations such as those mandated by the Americans with Disabilities Act,21 and by greater acceptance and enabling expectations.
Interim Developments of the WHO and Institute of Medicine
Saad Nagi22 developed a conceptual model of disablement in the 1960s that was similar to the WHO model. It recognized that the correlations among impairments, functional limitations, and associated disabilities were poor. He suggested that environmental factors were important modifiers of this relationship, albeit in a unidirectional sense.
In 1991 the Institute of Medicine (IOM) defined disability as “a function of the interaction of the person with the environment” and produced an interactive model of the “enabling-disabling process,” which identified 3 independent modifiers, including biology (ie, heredity), environment (ie, physical, social, psychological), and lifestyle and behavior.23
In 1997, a second International Classification of Impairments, Disabilities, and Handicaps (ICIDH-2) was presented by the WHO. 24 This model changed terminology of disablement (referencing impairments, disability, and handicap) to that of enablement (referencing impairments, activities, and participations). It provided unified and standard language to characterize the functional consequences of a variety of health conditions.24
FIGURE 1-2
World Health Organization’s International Classification of Illness
PathologyImpairment Disability Handicap
The underlying disease or diagnosis
The immediate physiological consequences, symptoms, and signs
The functional consequences, abilities lost
The social and societal consequences, freedoms lost
Rondinelli RD, Duncan PW. The concepts of impairment and disability. In Rondinelli RD, Katz RT, eds. Impairment Rating and Disability Evaluation. Philadelphia, Pa: WB Saunders Co; 2000:19. Used with permission.
The ICF recognizes that limitations to participation may secondarily produce activity restrictions or impairments. It also recognizes the impact of environmental and personal factors to the consequences of disease. Activity limitations and participation restrictions are not static. They may vary over time and be influenced by numerous physical and psychological factors that may also vary over time.
The ICF model is designed to be enabling in its approach and etiologically neutral in addressing human functioning as well as disability. It is inclusive in dealing with personal and environmental determinants of health and disablement, and is causally interactive as opposed to linearly predictive of its constructs and associations.
International Appeal and Applications
The ICF was developed out of a worldwide consensus process, which embodies broad cultural values and perspectives. The ICF model (unlike its predecessor, the ICIDH) was endorsed by the World Health Assembly in May 200125 and is now a member of the WHO Family of International Classifications. This acceptance reflects the increasing worldwide importance placed on recognition and reduction of burden of care associated with health conditions.
1.3c ICF Terminology and Definitions
According to the ICF, the following terms and definitions apply:
• Body functions: physiological functions of body systems (including psychological functions).
• Body structures: anatomic parts of the body such as organs, limbs, and their components.
• Activity: execution of a task or action by an individual.
• Participation: involvement in a life situation.
• Impairments: problems in body function or structure such as a significant deviation or loss.
• Activity limitations: difficulties an individual may have in executing activities.
• Participation restrictions: problems an individual may experience in involvement in life situations.
For purposes of the Guides, the following operational definitions and disclaimer apply:
Impairment: a significant deviation, loss, or loss of use of any body structure or body function in an individual with a health condition, disorder, or disease.
Disability: activity limitations and/or participation restrictions in an individual with a health condition, disorder, or disease.
Impairment rating enables the physician to render a quantitative estimate of losses to the individual as a result of their health condition, disorder, or disease. Impairment ratings are defined by anatomic, structural, functional, and diagnostic criteria; physicians are generally familiar with these criteria, based on their broader training and clinical experience. These ratings are determined by following accepted diagnostic processes and procedures. Most physicians are not trained in assessing the full array of human functional activities and participations that are required for comprehensive disability determinations. Impairment rating is a physician-driven first approximation of a process that attempts to link impairment with a quantitative estimate of functional losses in one’s personal sphere of activity. As a result, the following operational definition will continue to apply:
Impairment rating: consensus-derived percentage estimate of loss of activity reflecting severity for a given health condition, and the degree of associated limitations in terms of ADLs.
There are important remaining differences between the ICF and Guides terminology. The ICF model depicts only an association between body function/ structure, activity, participation, and a given health condition. Typically, in assessing impairment, the physician must determine if the health condition is causally related to an event or exposure.
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, technology, and
sufficient accommodations are available. Disability may be influenced by physical, psychological, and psychosocial factors that can change over time.
The Guides is not intended to be used for direct estimates of work participation restrictions. Impairment percentages derived according to the Guides’ criteria do not directly measure work participation restrictions. The intent of the Guides is to develop standardized impairment ratings to be used as follows:
1. Fix the diagnosis and associated percentage of physical and functional loss at “Maximum Medical Improvement” (MMI) (see Chapter 2).
2. Enable a patient with an impairment rating to exit from a system of temporary disablement (eg, temporary total or partial disablement under workers’ compensation before MMI).
3. Provide diagnosis and taxonomic classification of impairment as a segue into other systems of longterm disablement.
In disability evaluation, the impairment rating is one of several determinants of disablement. Impairment rating is the determinant most amenable to physician assessment; it must be further integrated with contextual information typically provided by nonphysician sources regarding psychological, social, vocational, and avocational issues.
1.3e Domains of Personal Function
There are 2 domains of human personal function that are most often affected by impairments and for which well-accepted measurement tools exist, and hence they are of particular interest to the impairment rater. These are mobility and “self-care,” which can be further defined and categorized as follows.26
Mobility
Transfer: movement of one’s body position while remaining at the same point in space (eg, supine to side lying, supine to sit, sit to stand).
Ambulation: movement of one’s body from one point in space to another (eg, walking, stair climbing, wheelchair locomotion).
Self-Care
Activities of Daily Living (ADLs): basic self-care activities performed in one’s personal sphere (eg, feeding, bathing, hygiene, dressing; see Table 1-1).
Instrumental Activities of Daily Living (IADLs): complex self-care activities (eg, financial management, medications, meal preparation), which may be delegated to others (see Table 1-1).
Examples of Impairment and Disability
Christopher Reeve was a well known celebrity who suffered a traumatic spinal cord injury resulting in a high-level cervical tetraplegia, a condition that would have an unusually high expected impairment rating due to the nearcomplete activity limitations that typically accompany it. In his particular case, he required elaborate mobility and ventilatory assistive equipment and the 24-hour availability of a personal care attendant to assist with virtually all selfcare activities. However, Mr. Reeve was highly exceptional in terms of his public persona and renown, and his access to significant personal financial assets and other resources. He was able to martial these constructively to create an education and research foundation for which he was the principal spokesperson, and to become globally recognized as a prime advocate for the spinal cord injured and disabled. His vocational success would be judged exceptional even for any ablebodied individual, and underscores the fact that participation restrictions do not correlate with activity limitations in many instances.
Similarly, a given physical impairment can be highly disabling in one vocational context and virtually non-disabling in another. For example, amputation of one’s great toe might preclude the vocation of a ballerina who must dance “on point,” whereas the same amputation might be of no functional consequence to a construction worker equipped with an appropriately fitted work boot.
These mobility and self-care activities may be performed independently (without the use of a helper or adaptive aids) or modified independently (require the use of adaptive aids but no helper), or they may require helper assistance with or without adaptive aids. The highest level of independence with which the given activity is consistently and safely carried out at the individual’s baseline is considered the functional level for that individual.27
1.4 Measurement Issues
Measurement issues are important determinants in defining impairment. The process of impairment rating relies on criteria that may be discrete (ie, amputation of a limb) or continuous (ie, loss of range
TABLE 1-1
Self-Care
Activities of Daily Living (ADLs)
Bathing, showering
Bowel and bladder management
Dressing
Eating
Feeding
Functional mobility
Personal device care
Personal hygiene and grooming
Sexual activity
Sleep/rest
Toilet hygiene
Instrumental Activities of Daily Living (IADLs)
Care of others (including selecting and supervising
caregivers)
Care of pets
Child rearing
Communication device use
Community mobility
Financial management
Health management and maintenance
Home establishment and maintenance
Meal preparation and cleanup
Safety procedures and emergency responses
Shopping
Source: Youngstrom. 26
of motion). Severity of an impairment also can vary according to discrete (ie, level of amputation) or continuous (ie, degrees of motion lost) criteria. There are 4 levels of measurement whereby test results can be analyzed and interpreted, including nominal, ordinal, interval, and ratio.28 Nominal and ordinal scales are used to classify discrete measures because the scores they produce occupy mutually exclusive categories. Interval and ratio scales apply to continuous measures because the scores produced occupy points on a continuum within an available range of scores.12
Precision, accuracy, reliability, and validity are critical issues in defining impairment. Precision refers to the smallest unit of change that a measurement instrument can distinguish. Sensitivity to change is critical to the measurement of the clinical effects of treatment, and the sensitivity of a measurement scale should be appropriate to the level of precision required in a given case. Reliability is the extent to which a measurement provides consistent information.
Measurement Scales
Nominal scales categorize items into different, internally equivalent groups based on a single criterion. They may be dichotomous (ie, 1 of 2 possible groups such as male vs female) or nondichotomous (ie, the colors of the spectrum). Ordinal scales categorize items hierarchically, based on order of magnitude, where intervals between groups are not assumed to be equal and the order of magnitude may differ for each group. Ordinal scales are most commonly used in clinical practice and are typical of the self-report functional outcome scales being adopted here. Interval scales, by contrast, are continuous scales, which are rank ordered according to uniform and sequential units of increment (ie, temperature scale). Ratio scales are interval scales whose zero point reflects absence of the quantity being measured.12
Analysis of nominal and ordinal data requires special considerations to avoid mistaken inference of the results.29,30 Controversy surrounds summation and averaging of subtest scores to produce an overall result for comparative purposes. As such, continuous-scale measures lend themselves more readily to rigorous statistical analysis than is possible for discrete counterparts.12 Since the comparative data being drawn upon for some organ systems of the Guides remain largely discrete, by nature, and have not been subjected to appropriate Rasch analysis or other manipulations, the use of normative statistics (eg, means, standard deviations) for comparative purposes in such cases remains problematic and will be avoided.
Validity is the extent to which an instrument measures that which it is intended to measure.
Previous work examining the validity of musculoskeletal impairments derived according to the Guides has yielded equivocal results.15,32,33 One study33 examined the validity of hand impairments due to loss of ROM or to amputation, and in terms of correlations of impairment ratings and objective measures of hand function. Approximately two thirds of the correlations were significant; hence, these results were touted as a validation of impairment ratings. However, the R2 coefficients derived from these correlations (amount of variance actually “explained” in terms of these correlations and regressions) were quite low (exceeded .5 in only 8% of correlations.) Another similar
Precision and Accuracy
Consideration must be given to feasibility and practicality of achieving a given level of precision, including cost and availability of equipment, and time required and ease of application in the field. For example, a Thomas test can rapidly reveal presence of a hip flexion contracture to an examiner but is less precise than standard goniometric assessment of ROM for impairment rating purposes. The term accuracy defines the ability of a measurement to correctly (and precisely) assess the condition or process being measured. The ability to do so depends on minimizing sources of error, which in human performance measurement include examiner training and skills required to use, the interface between subject and measurement device, and the instrument itself. Generally speaking, examiner training is usually the most variable.31
study32 showed significant correlations between lower extremity impairments associated with fractures and measures of functional performance as well as limitations measured on the Sickness Impact Profile (SIP). Again, these results were used to tout validity. However, the associated R2 coefficients were again quite small (R2 .32 and .30, respectively).
A more recent study15 estimated upper extremity impairments due to a simulated “fusion” at the metacarpophalangeal joint of the dominant extremity in otherwise healthy adult subjects, using individually fabricated hand splints. They examined randomized, real-time performance on standardized measures of hand function with and without the splints, to obtain correlations and regressions of impairment ratings and functional performance. Although simulated impairments in that study led to slowing of performance on all functional measures, the correlations of degree of slowing and magnitude of impairment were not significant. The methodological limitations and small number of these studies preclude definitive conclusions concerning validity of impairment ratings at this time.
Collectively, these studies do suggest that the criterion validity of musculoskeletal impairment ratings, as traditionally determined, remains limited. What this means is that functional losses (in terms of ADLs) associated with impairment are not being captured by (and reflected in) the impairment ratings themselves. Likewise, such validity as is possible to achieve in impairment ratings can be expected to improve if greater attention is paid to direct
measurement of functional losses in terms of ADLs, in the derivation of these ratings.
1.5 Balancing Science and Clinical Judgment
1.5a The Relative Merits of Study Designs
The relative merits of research study designs have been examined, and hierarchies of evidence have been proposed.34–36 The Agency for Health Care Policy and Research has adopted a hierarchy of study types,37 based on ability of study design to minimize the possibility of bias and confounding influence, as listed in Table 1-2.35 Strength of evidence is based largely on reliability estimates of study design.35 Steps for determining levels of evidence and grades of recommendations for evidence-based clinical guidelines are as follows:
• Levels of evidence are defined and ranked hierarchically based on study design (see Table 1-2) and methodological quality of individual studies.
• Questions to be addressed are carefully defined.
• Eligible evidence is defined, as are inclusion and exclusion criteria.
• All studies meeting the aforementioned criteria relating to a specific question are obtained using clearly defined search strategies.
• Eligible studies are summarized in an evidence table.
• The strength of evidence to support a given intervention or hypothesis is stated.
• Judgments regarding the consistency, generalizability, applicability, and overall clinical impact are considered in linking evidence to clinical recommendations.
TABLE 1-2
Hierarchy
of Study Types
Systematic reviews and meta-analyses of randomized controlled trials
Randomized controlled trials
Nonrandomized intervention studies
Observational studies
Nonexperimental studies
Expert opinion
• Grades of recommendations are based on strength of supporting evidence as modulated by the judgment of guideline developers, especially in the absence of evidence.
Historically, the numerical ratings applied for organ system impairment and whole person impairment throughout the Guides are based largely on consensus and expert opinion. Research has focused on reliability and reproducibility of ratings17 and functional validity of ratings.15,32,33 The evidence basis for impairment percentages assignable to ICF functional levels must await further empirical testing;19 infrastructure exists to develop such studies based on the ICF model, core sets, and ADL assessments.38,39
Impairment and disability are complex concepts that are not yet amenable to evidence-based definition. Diagnoses should be evidence-based, however, the impact of injury or illness is dependent on factors beyond physical and psychological aspects, including psychosocial, behavioral and contextual issues. Therefore, it is more challenging to obtain data needed to define an evidence-based approach to impairment assessment.
Given the dearth of higher-level, evidence-based criteria on which to base impairment ratings, the following approach was followed for this edition of the Guides:
1. Current literature was consulted to ensure evidence-based approach for diagnoses used to determine consensus based impairment ratings.
2. Where ratings must be consensus based, due to absence or lack of valid objective data, explanation of the specific basis on which the ratings are derived is provided. Normative judgments that are not data driven will follow precedent in many cases and must await future validation studies before significant change is adopted.
3. Attempts have been made to normalize impairment ratings across organ systems to improve internal consistency. Decisions, in such cases, are
Reliability
A simple conceptualization of reliability is to consider a gun as a measurement instrument, and the shots fired at a target as the measurements themselves. If the shots cluster tightly, the gun is shooting with high reliability, regardless of where the cluster appears on the target. If the shots fail to cluster, the reliability is low.12 Reliability can vary significantly between instruments for a given rater, and between raters for a given instrument.40
Validity
Using the target analogy, if a gun (instrument) is aimed at the target, validity is the ability to hit the target at the point being aimed at. For purposes of discussion here, impairment ratings can be considered in terms of their content validity, construct validity, and criterion validity. Content validity of a particular test refers to its ability to cover a representative sample of a particular domain being measured. For example, “hand impairment” is determined by examining digital amputation level, joint ROM, sensory loss, and/or other anatomic and functional aspects of the hand. Such validity is generally asserted by expert opinion (Delphi panel). Construct validity refers to the extent to which the test measures some theoretical construct such as functioning (eg, ADLs), pain, or suffering. Criterion validity refers to whether or not the test measure in question correlates well (is predictive) with some independent criterion or “gold standard.” For example, a contrast venogram is a highly accurate test for detecting deep venous thrombosis (DVT). A venous Doppler is a less invasive and less costly alternative, which has shown high criterion validity to a venogram and, hence, is typically used instead to make the diagnosis of DVT in the clinical setting.12
consensus based and will remain so until future validation studies can be carried out.
1.6 The Case for Simplification and Ease of Application
The consensus of the Guides’ editors is that simplification and brevity, in conjunction with greater clarity, are needed. When evidence-based criteria are lacking, priorities for simplification apply.
1.7 The Application of Functional Assessment
1.7a Earlier Approaches That Have Worked Well
Criticism of previous editions of the Guides includes lack of validity due, in part, to inadequate attention to functional assessment.13,15,17 Historically, attention
to functional (as opposed to anatomic) loss in impairment rating determinations has varied by organ system and the availability of functional data. In the cardiovascular system, for example, anatomic loss refers to damage to an organ or body system (eg, left ventricular hypertrophy), whereas functional loss includes loss such as decreased ejection fraction of the heart. The New York Heart Association41 also provides a well-accepted 4-class, functionally based scheme (NYHA classes I-IV) according to symptoms with activity and overall functional ability in terms of ADLs. There is good evidencebased research linking the NYHA functional class to clinical status (activity tolerance) and metabolic equivalents (METs) achievable on treadmill testing.42 Similarly, in the respiratory system, a functionally based classification of dyspnea in relation to ADLs43 has been applied, and impairment ratings have been developed based on results of pulmonary function testing as well as exercise test results. The ADL-based functional assessment needs to be incorporated into the neurologic, musculoskeletal, and other organ systems of the Guides.
1.7b Self-Report Assessment Tools and the Need for Empirical Validation Through In-Office Applications
Functional assessment should be one aspect of impairment rating, but not the only aspect. Diagnosis, history, and physical examination; appropriate confirmatory tests; and functional outcome scores must all be incorporated.
The rating physician using the Guides should weigh all available information, emphasizing the importance of some and deemphasizing other information, so long as it is consistent and concordant with the pathology at issue. Patients may underreport or overreport their symptom complex, and any resulting clinical outcome tool based on self-report may be scored inappropriately low or high. Examiners must exercise their ability to observe the patient perform certain functional tasks to help determine if selfreport is accurate.
1.7c Choice of Functional Assessment Tools
This edition differentiates between the relative contributions of history of clinical presentation, physical findings, objective test results, and associated functional losses to the impairment rating. Functional assessment is discussed more explicitly in most chapters of this edition and is integrated with clinical presentation, physical findings, and objective testing.
Functional assessment can be approached from a global and/or organ-specific level. Several global functional assessment scales have been developed with multiple applications (eg, Short-Form 36).44 No brief and simple-to-use scale appears available that can serve for multiorgan system functional assessment purposes. In several specific organ systems, general functional outcome scales that are well accepted exist to determine functional loss in relation to symptom severity. For example, the NYHA’s Classification of Cardiac Disease41 and the American Thoracic Society’s Impairment Classification of Dyspnea 45 have well-documented grading schemes for symptom severity which have been validated against objective measures of metabolic energy expenditure and pulmonary function testing, respectively.
For the musculoskeletal organ system, no such well-accepted, cross-validated outcome scales exist. However, there are a number of organ-specific, self-reporting functional assessment tools. These tools were typically developed to assess postsurgical outcomes. Application of such normalized data to a skewed population of patients undergoing impairment ratings is potentially misleading. These tools can generate consistent and standardized self-report data for this subgroup, which can have descriptive and analytical applications toward impairment rating. The resulting scores can be rank ordered into “no deficit; mild; moderate; severe; and extreme” deficit categories to help quantify an individual’s perceived pain, suffering, and functional result. Such self-report tests can be easily and consistently administered in the physician’s office and quickly scored by the examiner. As results are wholly based on self-report, intentional manipulation of impairment rating is possible. Therefore, when these test results tend to place an individual in an impairment grade that is higher or lower than that suggested by other parameters, the evaluator must assess the validity and consistency of conventional information before assigning a rating.
With appropriate scaling, functional scores may also be helpful in developing an impairment percentage adjustment that is organ-specific and functionally based. What this means is that the tool was originally designed to give the examiner the ability to assess a postsurgical patient’s individual test score (standardized) in relation to the normative data of the population for which it was derived (ie, “Mrs. Smith scored at the 55th percentile; based on the population mean of 50% she is slightly better than average in functional outcome.”) The results of such tools,
