(1) The total impairment rating for a body
part cannot be more than 100% of the body part.
(2) When rating disability the movement in a
joint is measured in active degrees of motion. Impairment findings describing
lost ranges of motion are converted to retained ranges of motion by subtracting
the measured loss from the normal of full ranges established in these rules.
(a) Range of motion values for each direction
in a single joint are first added, then combined with other impairment
findings. [Example not included. See ED. NOTE.]
(b) Range of motion values for multiple
joints in a single body part (e.g., of a finger) are determined by finding the
range of motion values for each joint (e.g., MCP, PIP, DIP) and combining those
values for an overall loss of range of motion value for that body part. This
value is then combined with other impairment values.
(3) The range of motion or laxity
(instability) of an injured joint is compared to and valued proportionately to
the contralateral joint except when the contralateral joint has a history of
injury or disease or when either joint's range of motion is zero degrees or is
ankylosed. The strength of an injured extremity, shoulder, or hip may be
compared to and valued proportionately to the contralateral body part except
when the contralateral body part has a history of injury or disease.
Instability example:
The injured knee is reported to have severe instability of the
anterior cruciate ligament. The standards grant an impairment value of 15% for
severe instability of the anterior cruciate ligament.
The contralateral knee is reported to have mild instability of
the anterior cruciate ligament. The standards grant an impairment value of 5%
for mild instability of the anterior cruciate ligament.
A proportion is established by subtracting the contralateral
instability of 5% from the 15% for the injured joint which = 10% impairment for
the instability.
Strength example:
The injured deltoid muscle is reported to have 3/5 strength.
The standards note 3/5 strength = 50%.
The contralateral deltoid muscle is reported to have 4+/5
strength. The standards note 4+/5 strength = 10%.
A proportion is established by subtracting the contralateral
strength of 10% from the 50% for the injured arm which = 40%. This percentage
is then used to determine the loss of strength for the injured deltoid.
Range of motion examples:
Flexion (knee): 80° retained on injured side, the
contralateral joint flexes to 140°.
A proportion is established to determine the expected degrees
of flexion since 140° has been established as normal for this
worker.
One method of determining this proportion is: 80/140 =
X/150.
X = expected retained range of motion compared to the
established norm of 150° upon which flexion is determined under these
rules. X, in this case, equals 86°.
86° of retained flexion of the knee is calculated under
these rules, after rounding, to 23% impairment.
Extension (knee): 35° retained on injured side, the
contralateral joint extends to 15°. First, find the complement, i.e., 150 -
15 =135 (uninjured) and 150 - 35 = 115 (injured). Next, using the same method
as for flexion, 115/135 = X/150, or, X = 127.77. Then, revert back, so, 150 -
127.77 = 22.23 rounded to 22° for an impairment value of 9%.
(a) If the motion of the injured or
contralateral joint exceeds the values for ranges of motion established under
these rules, the values established under these rules are maximums used to
establish impairment.
(b) When the
contralateral joint has a history of injury or disease, the findings of the
injured joint are valued based upon the values established under these
rules.
(4) Specific
impairment findings (e.g., weakness, reduced range of motion, etc.) are awarded
in whole number increments. This may require rounding non-whole number
percentages and contralateral comparison degrees of motion for given impairment
findings before combining with any other applicable impairment value.
(a) Except for subsection (b) of this
section, before combining, the sum of the impairment values is rounded to the
nearest whole number. For the decimal portion of the number, point 5 and above
is rounded up, below point 5 is rounded down. [Example not included. See ED.
NOTE.]
(b) When the sum of
impairment values is greater than zero and less than 0.5, a value of 1% will be
granted. [Example not included. See ED. NOTE.]
(5) If there are impairment findings in two
or more body parts in an extremity, the total impairment findings in the distal
body part are converted to a value in the most proximal body part under the
applicable conversion chart in these rules. This conversion is done prior to
combining impairment values for the most proximal body part. [Example not
included. See ED. NOTE.]
(6) Except
as otherwise noted in these rules, impairment values to a given body part,
area, or system are combined as follows:
(a)
The combined value is obtained by inserting the values for A and B into the
formula A + B(1.0 - A). The larger of the two numbers is A and the smaller is
B. The whole number percentages of impairment are converted to their decimal
equivalents (e.g., 12% converts to .12; 3% converts to .03). The resulting
percentage is rounded to a whole number as determined in section (1) of this
rule. Upon combining the largest two percentages, the resulting percentage is
combined with any lesser percentage(s) in descending order using the same
formula until all percentages have been combined prior to performing further
computations. After the calculations are completed, the decimal result is then
converted back to a percentage equivalent. Example: .12 + .03(1.0 - .12) =.12 +
.03(.88) =.12 + .0264 =.1464 = 14.6 = 15. [Example not included. See ED.
NOTE.]
(b) Impairment values for a
given body part, area, or system must be combined before combining with other
impairment values. If the given body part is an upper or lower extremity,
ear(s), or eye(s) then the impairment value is to be converted to a whole
person value before combining with other impairment values, except when the
date of injury for the claim is prior to Jan. 1, 2005. [Example not included.
See ED. NOTE.]
(7) Loss
of strength is determined using the modified 0 to 5 international grading
system described below. The grade of strength is reported by the physician and
assigned a percentage value from the table in subsection (a) of this section.
The impairment value of the involved nerve, which supplies (innervates) the
weakened muscle, is multiplied by this value. Grades identified as "++" or "--"
are considered either a "+" or "-", respectively.
(a) The grading is valued as follows:
[Example not included. See ED. NOTE.]
(b) When a physician reports a loss of
strength with muscle action (e.g., flexion, extension, etc.) or when only the
affected muscle(s) is identified, anatomy texts or the AMA Guides to the
Evaluation of Permanent Impairment may be referenced to identify the specific
muscle(s), peripheral nerve(s) or spinal nerve root(s) involved. A copy of the
standards referenced in this rule is available for review during regular
business hours at the Workers' Compensation Division, 350 Winter Street NE,
Salem OR 97301, 503-947-7810.
(8) For muscles supplied (innervated) by the
same nerve, the loss of strength is determined by averaging the percentages of
impairment for each involved muscle to arrive at a single percentage of
impairment for the involved nerve. [Example not included. See ED.
NOTE.]
(9) When multiple nerves
have impairment findings found under these rules, these impairment values are
first combined for an overall loss of strength value for the body part before
combining with other impairment values.
(10) When a joint is ankylosed in more than
one direction or plane, the largest ankylosis value is used for rating the loss
or only one of the values is used if they are identical. This value is granted
in lieu of all other range of motion or ankylosis values for that
joint.
