Lateral epicondylitis, often called “tennis elbow,” is a musculoskeletal condition characterized by pain around the lateral elbow and adjacent forearm with resisted wrist extension or passive terminal wrist flexion with the elbow in full extension, plus tenderness over and/or just distal to the lateral epicondyle. The name is a misnomer because the pathology is neither inflammatory nor located in the lateral epicondyle but rather represents a chronic tendinosis with disorganized tissue and neovessels of the tendon originating from the extensor carpi radialis brevis muscle and less commonly the extensor digitorum communis muscle, which originate on the lateral epicondyle. Clinical assessment involves understanding the chronology, precipitating activities, current symptoms, and interference with activities of daily living. Physical examination is performed bilaterally and includes palpitation provocative testing, measuring elbow and wrist motions, and neurological evaluation. Many treatments have been proposed, but little quality evidence supports any specific approach; more than 90% of cases are managed nonoperatively. Severe cases that have failed at least months of nonoperative management may warrant surgical assessment, but studies of surgical results for treatment of lateral epicondylitis are limited. Impairment rating may be necessary in a minority of cases and involves using the AMA Guides to the Evaluation of Permanent Impairment ( AMA Guides ), Sixth Edition, based on diagnosis-based impairment and using Table 15-4, Elbow Regional Grid: Upper Extremity Impairments.

Part 1 of this series examined many of the rules in the AMA Guides to the Evaluation of Permanent Impairment ( AMA Guides ), Sixth Edition, regarding rating nerve entrapment or focal neuropathies; the current article, part 2, examines how to read and match the findings in an electrodiagnostic report to the criteria in Appendix 15-B, Electrodiagnostic Evaluation of Entrapment, as explained in Section 15.4f, and determine the severity of the test findings as listed in Table 15-23. Physicians who perform nerve conduction studies often use their own definitions of mild, moderate, and severe ; these definitions are not standardized and frequently differ from the electrophysiologic definitions used in the AMA Guides, Sixth Edition. When examiners rate focal entrapment neuropathy, they must match data from the electrodiagnostic report to the criteria in Appendix 15-B, and a figure shows a hypothetical motor nerve conduction report for a case that shows both mild neuropathy (conduction delay) of the median nerve at the wrist (carpal tunnel syndrome) and severe neuropathy (axon loss) of the ulnar nerve at the elbow (cubital tunnel syndrome). If both fibrillations and positive waves are seen in the same muscle, the reviewer can be more confident that other electromyographic potentials were not misinterpreted as fibrillations. Prepared with the results of electrodiagnostic studies, the evaluator can work through the steps of history, physical findings, and functional scale to determine the final upper limb impairment according to the AMA Guides .

The AMA Guides to the Evaluation of Permanent Impairment ( AMA Guides ), Sixth Edition, introduced the concept of diagnosis-based impairments (DBI), and a modified version of this method can be used in rating peripheral nerve injury in general (Section 5.4) and upper limb entrapment syndromes (Section 15.4f). The first portion of this article reviews the evaluation of upper extremity nerve impairment and summarizes inclusion criteria and causation correlation for carpal tunnel syndrome, Guyon's canal syndrome, cubital tunnel syndrome, anterior interosseous, Wartenberg's syndrome, and radial tunnel syndrome. Very mild nerve entrapments do exist and may fail to meet the AMA Guides criteria for impairment related to a diagnosis of nerve entrapment. Electrodiagnostic examination includes nerve conduction studies that assess the largest, most heavily myelinated axons, and needle electromyelography, which detects muscle membrane instability but not the sensory function of nerves. A case example from the AMA Guides, Sixth Edition, shows the process of permanent impairment rating in a case of carpal tunnel syndrome. Determination of impairment for peripheral nerve entrapments can be easily accomplished once one understands how to determine if the nerve under consideration from the electrodiagnostic evaluation demonstrates a conduction delay, a conduction block, or an axon loss. This establishes the test findings that usually are the only objective findings present.

The wrist is the articulation between the distal forearm bones (radius and ulna) and eight carpal bones. The most common carpal instability is between the scaphoid and lunate, termed scapholunate instability. Complete scapholunate dissociation results in a gap between the scaphoid and lunate on posterior–anterior (PA) radiographic projections (scapholunate gap). On lateral radiographs, the scaphoid assumes a flexed posture and the lunate extends, resulting in increased scapholunate and radiolunate angles. The second most common carpal instability patters is between the triquetrum and lunate, termed lunotriquetral instability. Ulnar translocation of the carpus, also known as carpal translation, refers to medial displacement of the entire carpus on the forearm (radius and ulna) and is the most common radiocarpal instability. In the AMA Guides to the Evaluation of Permanent Impairment ( AMA Guides ), Sixth Edition, carpal instabilities are rated using Table 15-3, Wrist Regional Grid; the impairment class is determined using Table 15-9, Clinical Studies Adjustment: Upper Extremities. Measurements from plain radiographs are used in Table 15-9 to characterize the instability as mild, moderate, or severe; these characterizations, in turn, determine the class. The assessment of carpal instability using radiographic measurements has limitations, particularly that the radiographic parameters used to grade impairment are imprecise; angular measurements between individual bones are particularly variable, and carpal bone axes can be difficult to determine due to bony overlap on plain radiographs.

Workers’ compensation and personal injury claims often become embroiled in debates about the cause of the clinical presentation. When the primary claim involves an extremity, affected individuals sometimes report subsequent symptoms in the contralateral, previously “normal” limb and often attribute its onset to overuse while favoring the initially involved extremity; such an overuse hypothesis seems plausible, and perhaps intuitively obvious, to some. The concept that favoring one upper limb can result in injury to or illness in the other is not based on scientific evidence and instead is an unsupportable myth. Determining relationships between risk factors or exposures and medical conditions is a complex process that is outlined in the Guides to the Evaluation of Disease and Injury Causation ( Causation ). A search on PubMed and MEDLARS using the key phrases “opposite uninjured arm” and “uninjured arm” returned only six relevant articles, and the authors report that claims of serious or persisting painful syndromes in the arm or hand opposite the injured one are seldom adequately supported by clinical evidence. Similarly, the literature does not support “favoring” as a reasonable cause for development of symptoms in the contralateral shoulder or elbow. Epidemiological studies can provide general information regarding risk; this information must be filtered by specific steps to assess causal association for a disorder and determine if the injury is work related. Findings then can be applied to the specific individual.

Some injuries to the extremities can be associated with multiple injuries or diagnoses, and, in such cases, evaluators should recall that the functional history adjustment can be considered only for the single highest rated condition. This Case Example illustrates the proper rating methodology using the AMA Guides to the Evaluation of Permanent Impairment ( AMA Guides ), Sixth Edition section on The Upper Extremities. A 58-year-old male automotive mechanic fell at work on an oil-slickened floor and landed directly on his left outstretched hand and wrist, as well as the lateral part of his left elbow. At maximum medical improvement (MMI), the individual complained of moderate pain at rest and severe pain with repetitive forceful gripping and grasping. Radiographs taken at MMI showed a healed distal radius fracture in anatomic position with no posttraumatic arthritis and no carpal instability. The AMA Guides, Sixth Edition, allows use of only one of two methodologies: the Diagnosis-based impairment (DBI) methodology or the range-of-motion (ROM) method. Because ROM findings at the left elbow and wrist were recorded as normal and because the greater impairment that is causally related to the injury is used to rate the impairment, the DBI methodology is appropriate here. Only a single diagnosis is rated per region, and a case that involves more than a single region in the same extremity can be rated for separate impairments based on the separate regional conditions or diagnoses.

When they assess impairment, examiners must determine what “loss, loss of use, or derangement of any body part, organ system, or organ function,” occurred, according to the AMA Guides to the Evaluation of Permanent Impairment, ( AMA Guides ), Fifth Edition. At the same time, the AMA Guides cautions examiners to avoid “double dipping,” or rating the same impairment twice: “Related but separate conditions are rated separately[,] and impairment ratings are combined unless criteria for the second impairment are included in the primary impairment.” For example, it is not appropriate for an examiner who is rating spinal impairment using a Diagnosis-related estimate (DRE) category to award an additional 3% whole person impairment (WPI) beyond the baseline rating for the category because of limitation in activities of daily living (ADLs), presumably at least in part because of residual pain, and then to award a further impairment rating for pain based on Chapter 18. Rather, the AMA Guides notes that “the impairment ratings in the body organ system chapters make allowance for any accompanying pain.” Duplicative and, therefore, erroneously inflated ratings sometimes are performed by physicians who are less experienced in using the AMA Guides or those who, due to patient advocacy or other reason, want to maximize ratings.

Permanent impairment cannot be assessed until the patient is at maximum medical improvement (MMI), but the proper time to test following carpal tunnel release often is not clear. The AMA Guides to the Evaluation of Permanent Impairment ( AMA Guides ) states: “Factors affecting nerve recovery in compression lesions include nerve fiber pathology, level of injury, duration of injury, and status of end organs,” but age is not prognostic. The AMA Guides clarifies: “High axonotmesis lesions may take 1 to 2 years for maximum recovery, whereas even lesions at the wrist may take 6 to 9 months for maximal recovery of nerve function.” The authors review 3 studies that followed patients’ long-term recovery of hand function after open carpal tunnel release surgery and found that estimates of MMI ranged from 25 weeks to 24 months (for “significant improvement”) to 18 to 24 months. The authors suggest that if the early results of surgery suggest a patient's improvement in the activities of daily living (ADL) and an examination shows few or no symptoms, the result can be assessed early. If major symptoms and ADL problems persist, the examiner should wait at least 6 to 12 months, until symptoms appear to stop improving. A patient with carpal tunnel syndrome who declines a release can be rated for impairment, and, as appropriate, the physician may wish to make a written note of this in the medical evaluation report.

The author responds to The Continuing Challenge of Evaluating Carpal Tunnel Syndrome Impairment in the March/April 2000 issue of The Guides Newsletter . Carpal Tunnel Syndrome (CTS) is a clinical diagnosis based on the patient's history and objective findings on examination. Patients present with dull, aching discomfort of the hand, forearm, or upper arm; paresthesias and tingling of the hand; subjective weakness or numbness; and, occasionally, autonomic changes. Nerve conduction velocity studies are highly accurate in documenting median nerve entrapment at the level of the wrists, but this is an anatomic finding and does not mean that the entrapment produces any symptoms. An electrophysiologic study does not predict if or when the median nerve entrapment will become symptomatic, which is based on the patient's history. Electromyography (EMG) and nerve conduction velocity (NCV) studies do not help distinguish among the many etiologies of CTS. EMG/NCV testing can provide significant, highly accurate information regarding the physiologic function of the median nerve at the level of the wrist, but physicians must know how to interpret this information in the clinical setting. [The Editor responds: Several traditional findings of CTS have little or no diagnostic value, and electrodiagnosis is the diagnostic test of choice, although reported sensitivities range from 49% to 84% with specificities of 95% to 97%.]

The three components of electrodiagnosis useful in evaluation of the peripheral nervous system and spinal cord include electromyography (EMG), electroneurography (nerve conduction studies), and somatosensory evoked potentials. EMG examination involves introduction of a special recording needle into a muscle belly. Electrical potentials located within a few millimeters of the needle are picked up by an electrode and are transmitted from the muscle to amplifiers that filter and display results visually for the electromyographer. Three types of spontaneous activity in electrical potentials are of the greatest relevance: positive sharp waves, fibrillation potentials, and fasciculations (fasciculation potentials on the EMG result from irregular firing of motor units). Electromyography can help assess the status of nerve fibers indirectly, but the integrity of large myelinated sensory and motor neurons can be evaluated directly by nerve conduction studies (NCS), also known as electroneurography. NCS can assess motor neurons, sensory neurons, or mixed nerve trunks. Sensory nerve conduction velocity can be studied in a manner analogous to motor conduction velocity: sensory fibers can be directly stimulated, and the evoked response can be measured at the wrist and elbow. Somatosensory evoked potentials occasionally are useful as an adjunct to EMG and NCS in the diagnosis of peripheral nervous system pathology. These tests also are useful when it is unclear whether an individual has a true radiculopathy.

The November/December 1996 issue of The Guides Newsletter included an article regarding the challenges faced by those who evaluate carpal tunnel syndrome (CTS) impairment. A recent case highlights some of these challenges: Ms Kirby presented for an independent medical evaluation to address two issues, the work-relatedness of her left CTS and the percentage of anatomic impairment due to her surgically treated left CTS. Relevant clinical records noted nonspecific complaints of left-hand pain and paresthesia but no abnormalities of the peripheral neuromusculoskeletal system. Motor nerve conduction velocities were normal and showed relative prolonged latencies in the left vs right median nerve at the wrist. Left carpal tunnel release surgery was recommended and performed, but Ms Kirby reported no improvement in her symptoms and had a self-perception of substantial occupational incapacity. The evaluating physician determined that Ms Kirby had neither the specific hand/wrist symptoms nor the median nerve slowing necessary to establish a diagnosis of CTS and, therefore, could not have work-related CTS according to the criteria in the AMA Guides to the Evaluation of Permanent Impairment, Fourth Edition. The parties involved could not reach a settlement, and the case went to trial; the trial court relied on the testimony of the treating surgeon in finding that Ms Kirby's CTS was caused by her work and awarded her a substantial percentage of occupational disability.

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.

Apportionment estimates the degree to which each of various occupational or nonoccupational factors may have caused or contributed to a particular impairment. Apportioning spinal impairment among different injuries often is challenging. The AMA Guides to the Evaluation of Permanent Impairment ( AMA Guides ), Third Edition, relied on the Range of Motion (ROM) Model, which is included in the Fourth Edition for use only in 2 circumstances: first, if the spine has a disease and no injury has occurred (eg, ankylosing spondylitis) and, second, as a tie breaker. The AMA Guides, Fourth Edition, introduced a new approach, the Injury Model or Diagnosis-related estimates (DRE) Model. The Injury Model is different from other approaches in the AMA Guides because when the individual reaches Maximal Medical Improvement (MMI), the degree of persisting anatomic or physiologic loss is rated. In contrast, the Injury Model rates the severity of the original injury, not the degree of recovery. Recurrence is common after significant back injury, so even if the individual seems to be doing well when rated, years later the functional result may be different; these concerns explain the instructions to rate soft-tissue back injury using objective findings and true radiculopathy using the Injury Model.

Wrist trauma can disrupt the ligamentous support between the carpal bones, leading to instability of the carpus and pain, loss of motion, and loss of function. The most common patter of wrist instability is scapholunate instability that results from a fall on the outstretched hand, possibly with twisting motion. The second most common carpal instability pattern is that between the triquetrum and the lunate, termed lunotriquetral instability. The AMA Guides to the Evaluation of Permanent Impairment directs physicians to use frontal and lateral roentgenographic projections of the wrist to evaluate carpal instabilities and to rate impairment as mild, moderate, or severe. Carpal height can be used to assess impairment. Carpal translation is a medial or lateral translation of the entire carpus on the forearm (radius and ulna). Arthritic changes also can impair wrist stability and are seen roentgenographically as loss of joint space in the wrist. The degree of carpal instability lies on a continuum of loss of carpal bone support and amount of collapse, and, although little absolute difference exists between a 28-degree radiolunate angle and a 31-degree measurement, these two measurements yield different impairment ratings. Also, some forms of instability (eg, dynamic carpal instability) appear roentgenographically if the wrist is stressed, and examiners have freedom to assign impairment without reproducible, objective measures.