IMPAIRMENT RATING 5 TH EDITION MODULE IV THE LOWER EXTREMITIES. CENTRAL AND PERIPHERAL NERVOUS SYSTEM PRESENTED BY: RONALD J. WELLIKOFF, D.C., FACC, FICC In conjuction with:
According to the Guides, the first step in evaluating the lower extremities is to establish the diagnosis(es) and whether or not the individual has reached MMI. The second step is to identify each part of he lower extremity that might possibly warrant an impairment rating (pelvis, hip, thigh, etc.) The physical examination MUST be accurate, objective, and well DOCUMENTED. Included in an impairment report the following should be considered: 1. Activities of Daily Living 2. Observations of the Examinee 3. Local and General Physical Examination 4. Appropriate Imaging Evaluation 5. Laboratory Tests 6. Photographic Record, if possible. A prior injury may be considered during an assessment of causation and, if included in the report, should be apportioned. IT IS ALSO ESSENTIAL THAT THE RATER INCLUDE, IN THE REPORT, A DESCRIPTION OF HOW THE IMPAIRMENT WAS CALCULATED.
Once again, the physical examination is the determining factor of a permanent impairment. The physical examination MUST be accurate, objective, and well DOCUMENTED. This section provides criteria for evaluating permanent impairment of the lower extremities, including impairment ratings that reflect an individuals activities of daily living. The evaluation of the lower extremities includes: 1. Feet 2. Hindfeet 3. Ankles 4. Legs 5. Knees 6. Hips and Pelvis
In this section, as with the upper extremities, assessment of the joints, associated soft tissues, vascular system, and nervous system are important components, as indicated. FIGURE 2 1 HIERCHY IN WHOLE PERSON CONCEPT FOR LOWER EXTREMITIES: WHOLE PERSON LOWER EXTREMITY 40% 50% 60% 100% 100% Introduction to the AMA s 6th edition of the Guides
METHODS OF ASSESSMENT There are a number of methods in which to evaluate impairments of the lower extremities. Let s take a look at a few of these methods.
Anatomic Assessment: This includes: 1. Range of Motion 2. Limb Length Discrepancy 3. Arthritis (has its own diagnostic category) 4. Skin changes 5. Amputation 6. Muscle Atrophy 7. Nerve Impairment 8. Vascular Derangement Diagnosis Based Assessment: This includes: 1. Specific fractures and deformities 2. Ligamentous Instabilities 3. Bursitis 4. Surgical Procedures (joint replacement, meniscectomies, etc.)
Functional Assessment: This procedure is used for conditions when anatomic changes are difficult to categorize or when functional implications have been documented.
While this form is specific for the lower extremities, each chapter has a chart specific to that body part or organ system. This form lists potential methods for each lower extremity part. The evaluator determines whether ROM impairment or other regional impairments are present for each relevant part and records the impairment values in the appropriate locations on the chart. The selection of the most specific method(s) and the appropriate combination are later considerations.
Since there are various methods to evaluate an individual, the one that is used is the one that provides the higher rating. The ratings in the Lower Extremities chapter are expressed in percentages of lower extremity impairments and then converted to whole person impairments.
NOTE: To avoid confusion, in some of the figures and on their tables, there are two or three impairments noted. When there is a parentheses the number represents a lower limb impairment. When there is a bracket, a particular part impairment is noted. When there is neither a parentheses or bracket then the impairment is for
When there are several impairments involving the same region, combine the regional LE impairments and then convert to whole person Regions of the Lower Extremity 1. Foot and Ankle: Mid shaft of the tibia to tip of the toes. 2. Knee: Mid shaft of the femur to the mid shaft of the tibia. 3. Hip: Articular cartilage of the acetabulum to the mid shaft of the femur. While one individual may have several impairments involving different parts of the same lower extremity another may have several impairments involving the same parts of the same lower extremity. When there are several impairments involving different regions of the LE evaluate each impairment separately, and then convert to whole person and then combine using the Combined Values Chart.
NOTE: There is another method, however, it is not recommended. In certain circumstances, x-ray measurement is recommended. The specific tables for these measurements will provide the impairment rating. ASSESSMENT METHODS Limb Length Discrepancy: The individual should be placed in the supine position with their legs in the same position. Measure the distance between the anterior superior iliac spine and the medical malleolus on the involved side, and compare it with the opposite side. In order to determine where the discrepancy is, flex the knees to 90 degrees with the feet flat on the table. If one knee is higher than the other, the tibia is longer on that leg.
Gait Derangement: Gait derangement is present with many different types of lower extremity impairments and is always secondary to another condition. Gait derangement impairments should be supported by pathologic findings like those found on x-rays. Generally, the gait derangement should be full time and the individual should require an assistive device. In most cases, gait derangement impairments are stand alone and are not combined with other impairment evaluation methods.
Muscle Atrophy (Unilateral): The evaluation of muscle atrophy is determined by circumferential measurement comparing one side of the lower extremity to the other. The general rule of thumb is, the thigh should be measured at 10 cm above the superior surface of patella with the knee fully extended and the muscles relaxed. The general rule of thumb is, the calf should be measured at the maximum circumference level bilaterally. You might want to measure down from the inferior border of the patella. Again, the knee is fully extended and the muscles relaxed. Atrophy at both the thigh and calf is evaluated separately and the whole person impairment combined.
NOTE: Diminished muscle function can be estimated using four different methods ONLY use one method. Atrophy ratings should not be combined with any of the other three possible ratings: 1. Gait Derangement 2. Muscle Weakness 3. Peripheral Nerve Injury.
Manual Muscle Testing: Manual muscle testing usually involves groups of nerves. The cooperation, or lack of cooperation, is dependent on the examinee. Even in a cooperative individual, strength may vary from one examination to another, or between two examiners. If the variance is more than one grade, then the measurement should be considered invalid.
In order for this assessment to be valid, the results should be in line with the type of injury sustained. Generally, this method of assessment is best used for pathology that does not have a primary neurologic basis eg, a compartment syndrome or direct muscle trauma.
Range of Motion: If the evaluator believes that restricted range of motion has an organic basis, three measurements should be obtained and the greatest range measurement should be used. If there is inconsistency of a rating class between the findings, on separate occasions, the results are considered invalid.
Range of motion restrictions in multiple directions do increase the impairments. ADD range of motion impairments for a single joint Hip motion is evaluated and any impairment added in each of the six directions of motion. Flexion + Extension + Internal Rotation + External Rotation + Abduction + Adduction
Joint Ankylosis: When a joint becomes immobile, no matter what the position, an impairment is present. The more the fixed position is left in a position of dysfunction, the higher the impairment. Multiple malpositions of the same joint ie. angulation and malrotation, are added whereas deformities of different joint are combined REMEMBER, added or combined impairment ratings can never exceed 100% of the lower extremity.
Arthritis: In order to realistically evaluate the impact of a traumatically induced arthritic impairment, x-rays are necessary. The presence of osteophytes and reactive sclerosis have no direct bearing on an impairment. The best roentgenographic indicator of disease stage and impairment for a person with arthritis is the cartilage interval or joint space. Amputations: With this type of residual problem, the location of the amputation is the primary indicator of impairment.
Diagnosis-Based Estimates: According to the Guides, some impairment estimates are assigned more appropriately on the basis of a diagnosis than on the basis of findings on physical examination. An example of this is someone who had a hip replacement and can function well but has some restrictions of ADL s to prevent deterioration or prosthesis failure. Remember: All impairments are based on the inability or curtailed ability to perform at least one Activity of Daily Living.
To rate a hip replacement, you must first address the information contained in the following table: PROCEDURE: Identify those categories that apply to the individual. Add the number of points from each category. Take that number and apply it to Table 17.33 to determine the impairment.
TABLE 17.33 POINTS Good Results Fair Results Poor Results
To rate a knee replacement, you must first address the information contained in the following table: PROCEURE: Identify those categories that apply to the individual. Add the number of points from each category (A, B, C) THEN Deduct the number of points form each category (D, E, F) Take that number and apply it to Table 17.33 to determine the impairment.
POINTS Good Results Fair Results Poor Results
Since we have talked about the Combined Values Chart let s take another look at it.
Peripheral Nerve Injuries: As seen in the upper extremities, peripheral nerve deficits are divided into two parts: 1. Sensory Deficit 2. Motor Deficit Full (complete) sensory or motor deficits have their own tables. Partial sensory or motor deficits are rated exactly the same as with the upper extremities. Sensory Impairment Rating: 1. Identify the area of involvement 2. Identify the nerve(s) that innervate the area(s). 3. Determine the value of the nerve(s) that innervates the area of involvement (Spinal nerves, Plexus, and major peripheral nerves. 4. Grade the severity of the sensory deficit or pain according to the grading classification. Use clinical judgment to select the appropriate percentage from the range of each grade. 5. Multiply the full value of the nerve by the degree of sensory deficit or pain.
CASE HISTORY (Taken from the Guides ) Current Symptoms: Individual walks with an abnormal gait, hyperextending his knee by using his hip extensors, just prior to weight bearing. Physical Exam: Decreased light touch perception in the leg in the distribution of the saphenous nerve (distal sensory branch of he femoral nerve(s). This area of skin on the medial leg has retained sharp dull perception. Blisters on the medial malleolus from his shoe rubbing on an area where the skin has decreased sensation. Quadriceps strength is judged as grade 4: moderate resistance by the examiner prevents full knee extension. Diagnosis: Partial femoral nerve palsy Impairment Rating: 4% WP
How did we get from the exam to the final impairment rating? The exam indicated decreased light touch perception in the leg (femoral nerve) and decreased skin sensation. Dysesthesia is defined, in Dorland s a distortion of any sense, especially that of touch. In this case we take 2% LE and combine it with 7% LE. = 9% LE
The sensory deficit and pain are forgotten during activity, so the severity grade multiplier is 4 The range of multipliers is 1%-25% In this case, based on clinical judgment, the multiplier used is 20%. 20% x 9% = 2% LE
Again, as discussed with the upper extremities, the AMA Guides addresses the loss of strength as a neurological deficit. Rules and precautions must be taken in order to rate the motor aspects appropriately. Muscle testing, including tests for strength, duration, repetition of contraction, and function helps evaluate the motor function of specific nerves. Testing should be performed both ACTIVELY and PASSIVELY, but, only the ACTIVE movement should be considered in the impairment. The rating of loss of function due to loss of strength is dependent on two major factors: 1. Muscle Grade 2. Inervation of the nerve that goes to the muscle Muscle Grading is based on two principles: 1. Gravity (the ability to raise a segment of the body through its ROM against gravity). 2. Resistance (to hold its segment at the end of its ROM against resistance).
The Guides lists six muscle grades and assigns each a value. NOTE: In the 5 th edition, the rating scales now read 5 through 0 with 5 being considered normal and 0 indicating no contractibility. GRADE % MOTOR DEFICIT 5 Complete active ROM against gravity with full resistance 4 Complete active ROM against gravity with some resistance 3 Complete active ROM against gravity only, without resistance 2 Complete active ROM, with gravity eliminated 1 Evidence of slight contractability, no joint movement 0 1-25 26-50 51-75 76-99 0 No evidence of contractabilty 100 To be accurate, compare the affected and non-affected sides.
Let s look at the same case resulting in a motor deficit. The maximal impairment for total loss of femoral nerve motor function is 37%. The individual can move the leg through a full range of motion against gravity, but with only minimal resistance added. Once again, this is grade 4 with a grade range of 1%-25%. This time, based on clinical judgment, a 25% multiplier is chosen. 25% x 37% = 9% LE With both the sensory and motor deficits considered, the final rating would be: 9% LE c 2% LE = 11% LE This converts to a final impairment rating of 4% WP
REMEMBER, give the patient what is due. HOWEVER, when rating an extremity the final impairment should not exceed the amputation rating. It would be very difficult to explain that to a judge or jury.
This section of the Guides addresses the following: 1. The Brain 2. Cranial Nerves 3. Spinal Cord 4. Nerve Roots 5. Peripheral Nerves and Muscles As previously mentioned, be sure, if you use this section that you have objective, evidence-based rationale for your decisions and opinions. I suggest that you don t go where you have limited experience. REFER WHEN NECESSARY In this section, deficits or impairments are based on the neurologic evaluation.
It is important to note that for some nervous system impairments listed, hand dominance is critical to determine the degree of impairment. It is also important to note that pain has been accounted for neurologic based impairment ratings. Once again, all impairments MUST be related to a negative impact on the Activities of Daily Living. When an impairment involves more than one nervous system area, determine the whole person rating for each area and then combine them. NOTE: Because brain dysfunction will likely affect many overlapping functions, identify the most severe cerebral impairment. The impairment rating is based on the neurologic condition that causes the most severe impairment.
There are 5 steps in evaluations: 1. Assess the cerebral function to determine level of consciousness or awareness. 2. Evaluate mental status 3. Identify difficulties with language 4. Evaluate any emotional or behavioral disturbances 5. Identify the most severe cerebral problem and combine with other neurologic disturbances Criteria for Rating Impairment Due to Central Nervous System Disorders: The most severe category of impairment is based on the neurologic evaluation and relevant clinical investigations in four categories: 1. State of consciousness and level of awareness, whether permanent or episodic. 2. Mental status evaluation and integrative functioning. 3. Use and understanding of language. 4. Influence of behavior and mood. NOTE: Decide if you have the expertise, training, or experience to give an opinion on these areas of neurology.
The following are a list of impairments that may be combined with severe cerebral impairments:
The cranial nerves are evaluated individually based on specific tables and various chapters in the Guides. Problems maintaining balance and stable gait can develop from a CNS or peripheral neurologic impairment. Impairment ratings for station and gait disorders are determined according to the effect on ambulation. Other anatomic The basic tasks of everyday living depend on dexterous use of the dominant upper extremity. In most cases, loss of the dominant extremity is higher than the nondominant extremity.
The basic tasks of everyday living depend on dexterous use of the dominant upper extremity. In most cases, loss of the dominant extremity is higher than the nondominant extremity.
The spinal cord relays impulses for motor, sensory, and visceral functions. Impairments resulting from spinal cord injuries and other adverse conditions include those relating to: 1. Station and Gait 2. Use of the Upper Extremities 3. Respiration 4. Urinary Bladder function 5. Anorectal function 6. Sexual function 7. Pain When a spinal cord injury impairs several functions or systems, the impairments are combined
Intractible chronic pain certainly may impact on ADL s. Chronic pain includes: 1. Causalgia 2. Posttraumatic Neuralgia 3. Reflex Sympathetic Dystrophy Upper Extremity Lower Extremity
There are other CNS and PNS disorders that are ratable for impairment, however, they are limited as to specific causes. For that reason, and the fact that most of them do not relate to a traumatic etiology, they will not be discussed in this presentation. Again, before rating an individual based on CNS and/or PNS disorders, be sure that you are on firm ground and that you can defend your opinion.