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Established in 1985, the Workplace Safety and Insurance Appeals Tribunal (WSIAT) is the final level of appeal to which workers and employers may bring disputes concerning workplace safety and insurance matters in Ontario. WSIAT has always been separate from and independent of the Workplace Safety and Insurance Board.



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  Decision 2701 16
D. McBey

  • Permanent impairment {NEL} (rating schedule) (AMA Guides)
  • Apportionment (non-economic loss) (preexisting conditions)
  • Preexisting condition (rateable condition)

The worker suffered a low back injury in April 2009. The Board granted an 11% NEL award but reduced the award to 4% due to a pre-existing condition. The worker appealed.
Board Operational Policy Manual, Document No. 18-05-03, on determining the degree of permanent impairment, which is applicable to decisions made on or after November 1, 2014, provides that pre-existing conditions affecting the same area of the body are factored out. The policy refers to Document No. 15-02-03 for the definition of pre-existing condition. That results in an extremely broad formulation. However, Document No. 18-05-03 contains a delimiting condition, with the requirement that the evidence must show that the pre-existing condition, on its own, would result in an impairment rating. This is a mandatory stipulation.
To determine whether the pre-existing condition would result in an impairment rating, it is necessary to consider the AMA Guides. According to the AMA Guides, an impairment is an alteration of an individual's health status that is assessed by medical means. It is what is wrong with a body part or organ system and its functioning. The Vice-Chair noted that several specific rating provisions of the AMA Guides identify abnormal conditions for which the rating is 0%. This indicates that ratings are closely correlated to whether a medical condition or anomaly has a functional impact.
Document No. 18-05-03 also states that a pre-existing condition does not need to have produced periods of impairment or have caused a disruption in employment in order to factor out its rating. The Vice-Chair found that provision to be permissive rather than mandatory. As such, it broadens the scope of conditions that a decision-maker may take into consideration but the application of this discretion must be exercised consistently with the legislatively-incorporated provisions of the AMA Guides.
On the evidence in this case, the Vice-Chair found that the worker had no symptoms or functional anomalies attributable solely to degenerative changes prior to the compensable accident. The Board found that the worker had a rateable pre-existing condition within Table 53II of the AMA Guides. However, the Vice-Chair noted that the title of Table 53 refers to impairment. Thus, the specific rating provisions in that Table are to be interpreted as describing alterations to health status that manifest in functional abnormality. In this case, there was no medically documented prior injury and no prior manifest functional abnormality.
The Vice-Chair concluded that the worker's pre-existing degenerative changes would not, on their own, have resulted in an impairment rating under the AMA Guides. Therefore, the worker did not have a pre-existing condition within the meaning of the Board policy. The worker was entitled to the 11% NEL award without reduction. The appeal was allowed.