Evaluation Of Permanent Impairment Research Articles

Cauda Equina Syndrome

Abstract The cauda equina is a collection of peripheral nerves in the common dural sheath within the lumbar spinal canal. Cauda equina syndrome, also known as bilateral acute radicular syndrome, usually is caused by a large, sequestered acute disc rupture at L3-4, L4-5, or L5-S1 that produces partial or complete lesions of the cauda equina–lower motor neuron lesions associated with flaccid paralysis, atrophy, and other conditions. Patients usually present with a history of back symptoms that have worsened precipitously. The syndrome includes back pain, bilateral leg pain, saddle anesthesia, bilateral lower extremity weakness, urinary bladder retention, and lax rectal tone. Cauda equina syndrome is rated using Diagnosis-related estimates (DRE) lumbosacral categories VI or VII. Category VI, Cauda Equina–like Syndrome Without Bowel or Bladder Signs, is used when there is permanent bilateral partial loss of lower extremity function but no bowel or bladder impairment. Category VII, Cauda Equina Syndrome with Bowel or Bladder Impairment, is similar to Category VI but also includes bowel or bladder impairment. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) uses the term cauda equina syndrome with reference to both the thoracolumbar and cervicothoracic spine regions; this usage is unique to the AMA Guides but maintains the internal consistency of the Injury Model, which is the best approach to date for assessing spine impairment.

Quick Reference: Chapter 4: The Nervous System

Abstract Impairment rating for conditions that affect the spinal cord is discussed in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, Section 4.3. Spinal cord lesions produce varied and characteristic patterns of neurologic loss, depending on the portion of the cord affected, and the AMA Guides divides them into six categories: station and gait, use of upper extremities, respiration, urinary bladder dysfunction, anorectal dysfunction, and sexual functioning. With respect to station and gait, the functional result of the disorder is rated, not the underlying pathology (infarct, contusion, or otherwise), so that different conditions with similar functional outcomes can have similar ratings. Because many activities of daily living depend on dexterous use of the dominant upper limb, loss or loss of use of that extremity usually results in greater impairment than if the contralateral limb were involved. Section 4.3c addresses breathing only in terms of neurologic limitations, and other aspects are covered in chapters that address the respiratory system; criteria for neurologic impairment of the bladder (used to rate bladder dysfunction related to neurologic pathology, based primarily on ability to control bladder emptying); impairment ratings associated with anorectal dysfunction; and rating sexual functioning.

Clinical Update: Spinal Cord Impairments

Abstract Lower urinary tract dysfunction may result from a variety of neurologic disorders, including traumatic spinal cord injury, head injury, a cauda equina syndrome, or trauma to the peripheral lumbosacral nerves. Urinary incontinence can be divided into five categories: stress incontinence, urge incontinence, mixed incontinence, overflow incontinence, and total incontinence. A table lists each type, provides a description, and gives both common and neurological examples. Evaluation of voiding dysfunction should not be based on symptoms alone, and urodynamic evaluation is required also. Indeed, urodynamic evaluation is the only means to establish a functional interrelationship of the components of the lower urinary tract. Most ratings of neurogenic bladder dysfunction are performed using Section 4.3d, Urinary Bladder Dysfunction, and Table 17, Criteria for Neurologic Impairment of the Bladder in the AMA Guides to the Evaluation of Permanent Impairment. Ratings for whole-person permanent impairment depend on symptomatology (ie, urgency, dribbling, or incontinence), voluntary control, and bladder reflex activity. If problems with urinary system dysfunction are related to a combination of neurologic and urologic pathology, including pathology in the upper urinary tract, ratings from both sections can be combined using the Combined Values Chart.

Improving the Validity of the Impairment Evaluation Process: A Proposed Theoretical Framework

The American Medical Association's Guides to the Evaluation of Permanent Impairment is the most widely used set of procedures for rating permanent medical impairment. Although the Guides authors intend that the impairment ratings not be used for disability determination, the ratings are routinely used in benefit entitlement systems for work disability. This has created problems with the validity of the Guides because the validity of a measure is affected by the context within which the measure is used. To maintain wide acceptance of the Guides, its authors need to address this problem. One approach that we recommend is to adopt a model of work disability to specify the context of the Guides so that the level of measurement of each chapter can be explicated. This will retain the validity of inferences from the measures and integrate with developing systems that determine work disability.

Questions and Answers

Abstract Workers’ compensation in Canada is a legislated system of social insurance that is funded by assessments levied on employers. Thirteen established Workers’ Compensation Board (WCB) systems have regional jurisdiction and responsibility for administering and adjudicating compensation for the injured worker. Disability awards for certain injuries are determined by statute; others are determined using an acceptable reference or impairment schedule such as the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides). On August 22, 1960, Dr D. E. Bell presented to the Association of Workers’ Compensation Boards of Canada an impairment rating schedule to represent the loss of earning capacity and fulfill the spirit of workers’ compensation. Dr Bell's schedule has served as the basis for many Canadian WCB Primary Rating Schedules. Most jurisdictions refer to the AMA Guides in instances when the primary schedule is inadequate. A table in this article lists the current primary and secondary schedules for assessment of impairment in Canada; another table shows the differences in the ratings between Dr Bell's schedule and the AMA Guides. The AMA Guides is used principally only in Yukon and Prince Edward Island and is used for impairment estimations of more complicated injuries in all regions but Quebec.

Tools & Resources: Impairment and Disability Web Sites

Abstract Personality disorders are enduring patterns of inner experience and behavior that deviate markedly from those expected by the individual's culture; these inflexible and pervasive patterns reflect issues with cognition, affectivity, interpersonal functioning and impulse control, and lead to clinically significant distress or impairment in social, occupational, or other important areas of functioning. The AMA Guides to the Evaluation of Permanent Impairment, Fourth Edition, defines two specific personality disorders, in addition to an eleventh condition, Personality Disorder Not Otherwise Specified. Cluster A personality disorders include paranoid, schizoid, and schizotypal personalities; of these, Paranoid Personality Disorder probably is most common in the legal arena. Cluster B personality disorders include antisocial, borderline, histrionic, and narcissistic personality. Such people may suffer from frantic efforts to avoid perceived abandonment, patterns of unstable and intense interpersonal relationships, an identity disturbance, and impulsivity. Legal issues that involve individuals with cluster B personality disorders often involve determination of causation of the person's problems, assessment of claims of harassment, and assessment of the person's fitness for employment. Cluster C personality disorders include avoidant, dependent, and obsessive-compulsive personality. Two case histories illustrate some of the complexities of assessing impairment in workers with personality disorders, including drug abuse, hospitalizations, and inpatient and outpatient psychotherapy.

Clinical Update: Overview of Work-Capacity Restrictions

Abstract Early return to work is fundamental in the treatment of occupational injuries, but the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) may require temporary or permanent work restrictions. The US Department of Labor Physical Demand Characteristics of work classifies jobs by exertional level (sedentary, light, medium, heavy, and very heavy). The Workplace Functional Ability Guidelines (WFAGs) consist of 21 categories of health impairment and emphasize what the worker can do, ie, the “functional ability.” Musculoskeletal symptoms and signs such as strength, range of motion, or radiographic findings are not good predictors of functional abilities, nor does standardizing the method for work-capacity determination. Measures of physical work performance, even when conducted by highly trained individuals, have low interrater reliability when used for complex tasks. Any discrepancy in expectations between the physician and worker about capabilities and anticipated progress should be resolved. This may be best done if the physician is familiar with the requirements of the job and can offer suggestions about, for example, reducing the stress on an injured body part by using a different model of a tool. Individual differences in motivation, pain tolerance, conditioning, and so on make it difficult to determine work restrictions, but physicians should attempt to return the worker to gainful employment as early as possible.

Impairment and Disability Compensation Systems in the United States

Abstract Although several states use the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) when they evaluate individuals with impairments and disabilities, various disability systems exist in the United States. Disability and compensation systems have arisen to ensure that disadvantaged members of society with a medically determinable impairment, which may lead to a disability, have recourse to compensation from various sources, including state and federal workers’ compensation laws, veterans’ benefits, social welfare programs, and legal avenues. Each of these has differing definitions of disability, entitlement, benefits, procedures of claims application, adjudication, and the roles and relative weights assigned to medical vs administrative deliberations. Workers’ compensation statutes were enacted because of inadequacies of recovery from claims for injured workers under common law. Workers’ compensation is a no-fault system adopted to resolve the dilemmas of tort claims by providing automatic coverage to employees injured during the course of employment; in exchange for coverage, employees forego the right to sue the employer except for wanton neglect. Other workers’ compensation programs in the United States include the Federal Employees Compensation Act; the Federal Employers Liability Act (railroads); the Jones Act (Merchant Marine Act); the Longshore and Harbor Workers’ Compensation Act; the Department of Veterans Affairs; Social Security; and private, long-term disability insurance.

Literature Review

Abstract Before the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, spine impairment was based on range of motion (ROM) testing combined with ratings for specific spine disorders and neurologic impairment. The AMA Guides, Fourth Edition, uses the Injury or Diagnosis-related Estimates (DRE) Model to rate spinal impairment. This model is based on history, physical examination (but not ROM unless ROM is used as a differentiator), and other test data. Table 71, DRE Impairment Category Differentiators, lists DRE impairment category differentiators and discusses the differences between ratings, choosing between differentiators, and their reliability and validity. Guarding is “a spasm of muscles to minimize motion or agitation of sites affected by injury or disease,” and spasm often is overreported by physicians who are unaware of its definition. Loss of reflexes, presenting as diminished or absent deep tendon reflexes, remains the hallmark of objective physical evidence. Decreased circumference is associated with atrophy. Loss of motion segment integrity is measured on lateral flexion and extension x-rays. Loss of bowel or bladder control suggests significant spinal cord injury. The final differentiator is bladder studies, measured using a cystometrogram and showing unequivocal neurologic compromise of the bladder with resulting incontinence.

Minimizing Impairment Evaluation Difficulties and Risks

Abstract Significant professional and legal difficulties and risks may be associated with the performance of impairment evaluations, particularly in the context of an independent medical evaluation (IME). Many IMEs occur in legal arenas and may involve individuals with challenging personalities, and the circumstances of performing an IME are unique because there exists no physician-patient relationship. The best defense against professional or legal difficulties is prevention, including establishing a well-thought-out process for performing these evaluations, being consistent with directives provided in the AMA Guides to the Evaluation of Permanent Impairment, and, if a problem arises, dealing with it directly and documenting the circumstances. If an examinee is uncooperative, the examining physician may need to explain his or her role, and, if the examinee remains uncooperative or is disruptive, the examiner may stop the examination, notify the client, contact the police as appropriate, and document what occurred. Injury claims against an examiner may be forestalled by preventive strategies such as obtaining written informed consent from the patient to perform the evaluation, having a member of the examiner's staff present during the evaluation, and, after the examination, using a patient satisfaction survey to document “no difficulties with the evaluation.” IMEs require examiners to be familiar with legal aspects of confidentiality, libel and slander, negligence, and other issues. Examiners should ensure their medical malpractice insurance is suitable for this work.

Quick Reference: Chapter 3: The Peripheral Nervous System

Abstract Most impairment ratings for conditions affecting the cervical spine are relatively straightforward and can be addressed using the first three categories of the Injury Model in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides). This real-life case study illustrates how higher impairment categories are applied, including combining categories; the importance of rating the patient's condition based on the injury (as opposed to treatment outcome); and how apportionment is handled in different jurisdictions. Mr Smith, a 64-year-old high school principal, presented with numbness and burning pain from the chest to the feet, unsteadiness of gait, and difficulty maintaining an erection. Symptoms reportedly began two years earlier when he tripped and fell down a flight of stairs at work, striking his face. An MRI scan revealed marked spinal stenosis and cervical cord compression at C3 due to a combination of posterior C3-4 disc protrusion and osteophyte formation. Via an anterior approach, the orthopedic surgeon performed a C4 corpectomy, C3-4 and C4-5 discectomies, and then inserted a tricortical iliac bone graft between C3 and C5. Mr Smith improved postoperatively but still complained of numbness from upper chest to feet, mild unsteadiness of gait, and difficulty maintaining an erection. Evaluators can use the Injury Model, recalling that surgery to treat an impairment does not modify the original impairment, and in the jurisdiction in which Mr Smith was rated, if a claimant was asymptomatic before a work injury, the entire impairment is attributed thereto.

Literature Review

Abstract Pain is the most common presenting complaint at an impairment evaluation. In the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), the term chronic pain is synonymous with chronic pain syndrome. The AMA Guides differentiates between pain of longstanding duration, termed persistent pain, and chronic pain syndrome, which is characterized as “the devastating and recalcitrant type [of pain] with major psychosocial consequences.” Persistent pain may exist in the absence of chronic pain syndrome, but chronic pain syndrome always presumes the presence of persistent pain, according to the AMA Guides. The assessment of chronic pain syndrome involves a multidimensional approach, and a physical examination alone may be misleading. Chronic pain syndrome is a biopsychosocial phenomenon of maladaptive behavior, and the AMA Guides describes diagnostic criteria for chronic pain syndrome. In addition, this article includes a checklist of characteristics shared by chronic pain patients, along with a list of essential questions that evaluators can ask in assessing pain and a list of pain, behavioral, and psychological inventories commonly used in independent medical evaluations. Physicians should choose a battery that is consistent with the needs of the assessment, and the final report should explain the findings and significance of the inventories used.

Quick Reference: Rating Spine Impairment

Abstract Spinal impairment evaluation includes determining the presence or absence of loss of motion segment (structural) integrity (LOMSI). The AMA Guides to the Evaluation of Permanent Impairment, Fourth Edition, defines two ways of detecting LOMSI: anterior-posterior translation of one vertebra on another (more than 3.5 millimeters in the cervical spine or 5 millimeters in the thoracic or lumbar spine); or angular motion of one vertebra on another greater than 11 millimeters (15 millimeters at L5-S1). A finding of LOMSI results in at least a diagnosis-related estimate Category IV impairment rating in any of the three spinal regions. Measurements of vertebral translation and angular motion are made using standing lateral x-rays in maximal flexion and extension. The second method of detecting LOMSI is measurement of the angular motion between three adjacent vertebrae. Flexion and extension x-rays may not be necessary in every patient undergoing spinal impairment evaluation, particularly because patients rarely have LOMSI with normal supine spinal x-rays in the absence of translational or angular abnormality on routine films. Loss of structural integrity is rare in the workers’ compensation area and is seen most commonly in middle-aged women at L4-5 or following aggressive laminectomy. Attempted but unsuccessful fusion of a motion segment does not qualify as LOMSI.

Impairment Tutorial: Evaluating Impairment Due to Other Disorders of the Upper Extremity

Abstract Because grip and pinch strength are highly correlated and most literature deals with the former, this article focuses on grip strength, which is controversial because, as a functional test, it can be influenced by subjective factors that are difficult to control and include effort, pain, time of day, and fatigue. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) identifies additional factors that influence grip and include sex, age, sensation, comorbidities, age, nutritional status, and, perhaps, handedness. Although grip strength is considered a measure of hand function, its correlation with activities of daily living is poor. Grip strength measurements must be performed in a standard manner because altering wrist, forearm, or elbow position can change the results. Impaired hand strength is compared to that of the opposite extremity, which usually is normal; if both extremities are involved, the strength measurements are compared to the average normal strengths. The AMA Guides specifies that grip measurements are regarded as reliable if there is less than 20% variation in the readings, but subjective factors may result in higher-than-normal variance between measurements of grip. Because pain interferes with maximal effort and, if present, may invalidate grip strength measurement, the latter generally is inappropriate to rate tendonitis or other painful conditions. Generally, grip strength is not used to rate neurological deficits.

Tools and Resources: Instrumentation for Upper Extremity Impairment Assessment

Abstract The primary methods of evaluating impairment in the upper extremity are range of motion testing and neurological examination. For certain conditions that do not cause motion or neurological deficits yet leave the extremity significantly impaired, the editors of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, provided Section 3.1m, Impairment Due to Other Disorders of the Upper Extremity. The AMA Guides emphasizes that the criteria described in these “other disorders” should be applied only when the other criteria have not adequately encompassed the extent of the impairments. The evaluator must carefully read the criteria for rating each derangement to ensure the rating is correct and not duplicative. Table 26, Upper Extremity Impairment Due to Carpal Instability Patterns, includes values based on radiographic findings, and Table 27, Impairment of the Upper Extremity after Arthroplasty of Specific Bones or Joints, features ratings for resection arthroplasty and implant arthroplasty. Tables 28, 29, and 30 for musculotendinous impairments require that the percent of digit impairment be multiplied by the relative value of the digit according to Table 18. The AMA Guides does not assign a large role to functional measurements such as pinch and grip strength tests because they are influenced by subjective factors that are difficult to control.

Letter to the Editor

Abstract This letter responds to “Evaluating impairment from allergic disorders” in the March/April 1999 issue of The Guides Newsletter. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) does not provide clear direction about whether allergies themselves constitute impairment. Consider a worker whose symptoms of asthma subsequent to workplace exposure to toluene diioscyanate resolve when he or she is removed from the job and is no longer exposed to the chemical. Because everyday exposure to diisocyanates is not common and the patient no longer requires medication, one could conclude the patient has no impairment. In contrast, consider a patient who has developed latex allergies as a result of being a health care worker and has experienced two anaphylactic reactions at work after entering rooms where powdered latex gloves had been used and must travel with an epinephrine pen. This person would have a minimum of a Class I impairment because of the few limitations of this person's activities of daily living (ADLs) and the condition requires no or intermittent treatment. Both patients might feel they had permanent changes in their body functions that required permanent changes in their ADLs. Clinicians who make evaluations should be aware of patients’ need for medications or monitoring, the severity of the patient's reactions, and limitations on social activities (eg, need for medications and need to avoid seasonal pollens).

Quick Reference: Measuring Impairment Due to Other Disorders of the Upper Extremity

Abstract When performed according to criteria in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, upper extremity impairment assessment requires a thorough physical examination of the involved (and contralateral) upper limb. Observation and palpitation require no instrumentation, and much of the equipment necessary for the remainder of the examination may be present in the physician's office. According to the AMA Guides, sensory testing, particularly in the hand and digits, requires equipment and considers all sensory modalities, including perception of pain, heat, cold, and touch. For example, the two-point discrimination test of sensory quality can be performed using a paper clip or commercially available test disks. Traditionally, light touch is assessed using a cotton tipped swab, and sharp-dull discrimination can be assessed using a safety pin or needle (discard after use). Pressure and vibration sensibility can be assessed using the end of an initially still, then vibrating 128-Hz tuning fork. Deep tendon reflexes are tested with a reflex hammer; goniometers of various sizes are used for range-of-motion tests; and grip strength is assessed using a hand dynamometer. Other instruments are available to assess hand and upper extremity sensibility, coordination, strength, and motion but are not used by the AMA Guides for estimating impairment.

Upper Extremity Impairment Scenarios–Challenges in Rating

Abstract This article discusses situations in which an evaluating physician may find rating according the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) cumbersome, including fingertip injuries, transection of flexor digitorum sublimis tendon, medial and lateral epicondylitis, upper extremity amputations, and recurrent shoulder dislocation. On finding decreased motion at a finger distal interphalangeal joint (DIP) or thumb interphalangeal (IP) joint, the examiner should carefully assess the functional consequences and ensure the rating adequately addresses the impairment but does not rate the same problem twice. Laceration of the distal palm or proximal phalanx of a finger resulting in isolated transection of the flexor digitorum sublimis tendon (flexor digitorum profundus tendon remains intact) is a challenging scenario. Medial and lateral epicondylitis are not mentioned in the AMA Guides because usually they resolve with time. Grip strength loss usually is not an appropriate way to rate epicondylitis because pain limits grasp in this condition. Impairment ratings for upper extremity amputations may not be consistent in terms of the location where the procedure is used. Recurrent shoulder dislocation may complicate an initial traumatic dislocation, particularly in younger patients and must be medically documented rather than anecdotally reported. When faced with a situation that is not covered in the AMA Guides, the rating physician should consider analogous situations, consult other manuals or guidelines, or discuss the case with other experienced evaluators.

Clinical Update: Evaluating the Allergic Patient: Practical Techniques

Abstract Despite rapid advances in understanding of the biology of allergic disorders, practical techniques for evaluating the allergic patient remain fairly constant. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) requires appropriate assessment before an examiner diagnoses the disorder, determines causation, evaluates whether the patient has reached maximal medical improvement, and rates permanent impairment, if any. A careful history includes both occupational and environmental assessment. Patients with allergic occupational asthma typically must be removed from exposure to the allergen. The environmental assessment should determine the nature of the patient's dwelling, its construction material, heating and ventilation, and the presence or absence of a damp basement, pets, rodents or cockroaches, or hobbies performed in the home. A physical examination should focus on the eyes, nose, lungs, and skin and should exclude obstructive sleep apnea. A thorough medical evaluation always is required, and assessment of immunologic sensitization involves diagnostic allergy skin testing or laboratory assessment. Although the allergens used in such tests are purified and the tests themselves increasingly are standardized, concerns remain regarding nonstandardized laboratories and remote testing. Spirometry is an essential element in objectively defining the nature and severity of respiratory complaints; rhinolaryngoscopy helps differentiate asthma from laryngeal dysfunction and can evaluate sinus disease; and limited cut CT of the sinuses is more cost effective than plain sinus films.

Quick Reference: Measuring Impairments of the Hand and Digits

Abstract Many states require the use of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) in their workers’ compensation systems. In 20 states (see Table), this requirement is specified by statute (a law that is enacted and passed by a state's legislature). The state statutes that deal with the AMA Guides may or may not specify which edition to use and how to use it. In any case, ultimately it is the responsibility of the courts to interpret these statutes, which may be ague, to determine which edition of the AMA Guides should be used and to establish how that edition should be used. Evaluators should use the edition of the AMA Guides that is required by the local regulatory authority because of an incorrect version of the AMA Guides could result in judicial invalidation of an impairment rating (see, eg, McCabe v North Dakota Workers’ Compensation Bureau). A table that identifies the edition used and authorizing statute number for the 20 states is included.