Public Service Company of Colorado v. ICAO, 00CA1991 (June 21, 2001): Claimant sustained a compensable low back injury in 1991 for which he underwent surgery and received a permanent impairment rating of 16% of the whole person. Claimant reinjured his back in 1995, but recovered from that with no additional impairment.  Claimant sustained a third low back injury in 1998, which again necessitated surgery. His treating physician and the division-sponsored independent medical examiner (IME) both rated his permanent medical impairment at 23% of the whole person, which they reduced to 8% after apportioning the previous impairment rating.
The administrative law judge (ALJ) held that apportionment was inappropriate because claimant was not suffering any disability from the 1991 injury at the time of the 1998 injury. The ALJ found that the issue of preexisting disability pertained to apportionment rather than causation, and applied the preponderance of the evidence standard, rather than the clear and convincing evidence standard, in determining that claimant overcame the IME's opinion. The ALJ awarded claimant permanent partial disability benefits based upon the 23% rating. The court of appeals affirmed, and upheld the ALJ's determination that the apportionment applied by the IME was not entitled to presumptive effect because the IME's opinion was not based on a finding of causation. The court held that if a claimant's condition has improved to the extent that a previous disability is no longer present (i.e., asymptomatic) when the later injury occurs, the prior disability rating cannot be considered a contributing factor and apportionment is improper.