- Causation (thin skull doctrine)
- Permanent impairment {NEL} (degree of impairment) (back)
- Permanent impairment {NEL} (rating schedule) (AMA Guides)
- Apportionment (non-economic loss) (preexisting conditions)
- Board Directives and Guidelines (apportionment) (pre-existing condition) (measurable impairment)
The worker suffered a low back injury in February 2010, for which the Board granted the worker a 36% NEL award, but reduced by 7% to 29% due to a pre-existing condition. The worker appealed a decision of the Appeals Resolution Officer regarding the quantum of the NEL award for low back impairment, the quantum of a NEL award for psychotraumatic disability and level of LOE benefits after February 2015.
In this decision, the Vice-Chair dealt with the issue of the quantum of the NEL award for low back impairment.The Board found that the worker had a measurable pre-existing impairment with Board Operational Policy Manual, Document No. 18-05-05, and rated that pre-existing impairment at 7% using Table 53IIC of the AMA Guides.Table 53 deals with impairments due to specific disorders of the spine. Section II provides ratings for intervertebral disc or other soft tissue lesions. Seven types of lesions are identified as A through G. Lesion C is described as unoperated with medically documented injury and a minimum of six months of medically documented pain and rigidity.The Vice-Chair noted that the worker had not experienced any back pain prior to the compensable accident. Radiological studies conducted after the accident disclosed degenerative changes in the worker's lumbar spine. It was logical to conclude that these degenerative changes were present prior to the accident. However, those changes were asymptomatic prior to the accident. Table 53IIC refers to a medically documented injury and six months of medically documented pain. The Vice-Chair found that the worker did not have a measurable pre-existing impairment as described in Table 53IIC. Rather, the worker's lesion was best described within Table 53IIA for unoperated lesions with no residual signs or symptoms. The rating under Table 53IIA is zero.The Vice-Chair also considered the definitions of impairment in the WSIA and the AMA Guides.Impairment is defined in the WSIA as a physical or functional abnormality or loss which results from an injury. That definition would not include a pre-existing asymptomatic condition, as it does not result from an injury. Accordingly, the worker's pre-accident condition did not result from an injury and, accordingly, was not an impairment within the definition in the WSIA.In the AMA Guides, impairment means an alteration of an individual's health status that is assessed by medical means. The worker's pre-accident condition was an impairment within that definition. However, since there were no symptoms associated with that pre-accident condition, it would have attracted a zero rating under Table 53IIA.Thus, whether based on the definition in the WSIA or evaluation under the AMA Guides, there should be no reduction of the NEL award due to a pre-existing impairment.The Vice-Chair also considered the thin skull doctrine. Generally, as applied in workers' compensation, entitlement to benefits is not reduced due to a pre-existing condition which made a worker more vulnerable to injury, where the work accident made a significant contribution to the resulting injury. Those are the circumstances in this case.The worker also appealed regarding the calculation of the 36% NEL award. The Board found a 22% impairment for a nerve disorder affecting the left leg, which reduced to 9% on a whole person basis. There was also a 30% rating of the whole person related to the low back. The 30% rating and the 9% rating were combined for the 36% NEL award. The worker objected to the rating for the nerve disorder.Nerve disorders are rated under Table 49 of the AMA Guides. For the L5 nerve root, there are ratings for sensory deficit and loss of strength. Reference is then made to Tables 10 and 11 for grading schemes. Those grading schemes have a percentage range. The Board used the bottom of the range for both the sensory deficit and loss of strength. After review of the medical evidence, the Vice-Chair found that the worker's sensory and motor deficits were severe within the identified category and should have been rated using the top of the percentage range.On that basis, the combined NEL award should be increased from 36% to 39%. The worker was entitled to the 39% award without reduction.