IMPAIRMENT RATING

5TH 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

Introduction to the AMA’s 6th edition of the Guides

FIGURE 2 – 1 HIERCHY IN WHOLE PERSON CONCEPT FOR LOWER EXTREMITIES: WHOLE PERSON 40% 50% 60% 100% LOWER EXTREMITY 100%

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.

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

a 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.

When there are several impairments involving

the same region, combine the regional LE

impairments and then convert to whole person

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.

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.

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).

GRADE % MOTOR DEFICIT

5 Complete active ROM against

gravity with full resistance

0

4 Complete active ROM against

gravity with some resistance

1-25

3 Complete active ROM against

gravity only, without resistance

26-50

2 Complete active ROM, with

gravity eliminated

51-75

1 Evidence of slight contractability,

no joint movement

76-99

0 No evidence of contractabilty 100

The “Guides” lists six muscle grades and assigns each a value.

NOTE: In the 5th edition, the rating scales now read 5 through 0 with 5 being

considered normal and 0 indicating no contractibility.

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.

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.

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

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.