Workers' Compensation

California: Keys to Proving Apportionment: The Bullet Proof List

The apportionment statutes were massively revised by the 2004 workers’ compensation reform package. However, apportionment was one of the only areas of the workers’ compensation law that did not get hit by the most recent reform legislation of SB 863. Nevertheless, over the past year, the WCAB has fine tuned some of the defining principles of apportionment per Labor Code section 4663, as illustrated in several of the noteworthy panel decisions discussed below.

Apportionment Must Be Based on Substantial Evidence

In the noteworthy panel decision of Thomas v. Long Beach Unified School, 2012 Cal. Wrk. Comp. P.D. LEXIS 317, the WCAB set forth the basics as to what constitutes substantial evidence on the issue of apportionment.

Labor Code section 4663 provides as follows:

“(a) Apportionment of permanent disability shall be based on causation;

“(b) Any physician who prepares a report addressing the issue of permanent disability due to a claimed industrial injury shall in that report address the issue of causation of the permanent disability;

“(c) In order for a physician’s report to be considered complete on the issue of permanent disability, the report must include an apportionment determination. A physician shall make an apportionment determination by finding what approximate percentage of the permanent disability was caused by the direct result of injury arising out of and occurring in the course of employment and what approximate percentage of the permanent disability was caused by other factors both before and subsequent to the industrial injury, including prior industrial injuries.” (Emphasis added.)

Marva Thomas was working as an office assistant for the Long Beach School District when she suffered several admitted industrial injuries to her upper extremities and spine. She had fallen off a chair twice and had suffered a cumulative trauma to her wrists and spine due to her clerical work activities. The parties agreed to use Dr. Alban, as the orthopedic Agreed Medical Examiner (AME) in the case.

Dr. Alban made a specific determination of 50% apportionment to industrial factors and 50% apportionment to non-industrial factors. The Judge followed his determination and awarded permanent disability be reduced accordingly.

Five Components of Apportionment

In reversing the Judge’s finding on apportionment, the WCAB relied on two preeminent cases dealing with this issue, the en banc decision of Escobedo v. Marshalls (2005) 70 Cal Comp Cases 604 and the case of E.L. Yeager Construction v. WCAB (Gatten) (2006) 145 Cal. App.4th 922 [71 Cal Comp Cases 1687]. In those cases, the courts set forth five components of an apportionment determination that can be used as a checklist to ensure a doctor’s report is bullet proof on the issue.

1. Dr. must make a specific apportionment determination, using percentages, based on the permanent disability that existed at “the time of his (or her) evaluation of applicant.” (It’s fine if one of the percentages is 0% and the other is 100%, but there must be a specific determination.)

2. Dr. must analyze permanent disability based on causation of disability (rather than causation of injury);

3. Dr.’s opinion “must not be speculative, it must be based on pertinent facts and on an adequate examination and history;”

4. Dr.’s opinion must be based on “reasonable medical probability;”

5. Dr. must explain how and why he or she arrived at his conclusion.

The WCAB reviewed Dr. Alban’s discussion on apportionment, starting with his July 30, 2004 report as follows:

“The applicant’s obesity has played a significant role in the development of her extensive degenerative arthritis. 50% of her disability is apportioned to the degenerative joint disease affecting the cervical, thoracic, lumbar spine and bilateral shoulders. This disability would be present absent her industrial exposure with the Long Beach Unified School District. The remaining 50% is apportioned to her work-related injuries.”

In addition, the WCAB noted that Dr. Alban testified in his deposition of August 8, 2006, “that it was his intention when he initially made an apportionment determination apportioning 50% of her disability to degenerative joint disease, to, in essence, lump all of the pre-existing factors together.”

Escobedo & Gatten Require the Doctor to Explain All Conclusions

After comparing Dr. Alban’s analysis with that required in Escobedo and Gatten, the WCAB concluded:

“(T)he AME here has not gone beyond his conclusionary statements to justify his apportionment determination. We do not find his opinion on apportionment to constitute substantial medical evidence, as he has not adequately explained the ‘how and why the injury is responsible for approximately 50% of the disability,’ or state his apportionment opinion in terms of reasonable medical probability.”

The WCAB rescinded the Judge’s decision finding apportionment, and returned the matter to the trial level for further development of the medical record.

The findings in this case may be compared with other recent panel decisions in which the WCAB considered whether the AMEs’ reports contained all of the necessary elements of a proper apportionment determination. There is a particularly excellent discussion of this topic by Judge Ralph Zamudio, whose Report and Recommendation (R&R) was affirmed by the WCAB in Domay v. University of California Los Angeles, 2012 Cal. Wrk. Comp. P.D. LEXIS 122. That case dealt with a plumber, James Domay, who suffered a serious fall off a ladder onto the concrete landing below. In his R&R, Judge Zamudio lists each of the mandatory requirements for an apportionment determination based on substantial evidence, and explains how the AME properly met each of the requirements and apportioned 15% of the permanent disability to Mr. Domay’s prior snowboarding accident.

AME Is Considered Expert for Both Parties

In the panel decision of Briceno v. Los Angeles Unified School District, 2012 Cal. Wrk. Comp. P.D. LEXIS 226, the WCAB affirmed the Judge’s finding of apportionment of 90% of a teacher’s permanent disability to non-industrial factors. It is significant in both this case and the Domay case cited above that the Judge relied on the AME’s opinion regarding apportionment. Normally, the findings of the AME are to be followed, given that the AME is considered the expert for both parties in a case, as long as the AME’s report is considered substantial evidence, as it was in both of these cases. (See Green v. WCAB (2005) 127 Cal.App.4th 1426, 1444 [70 Cal Comp Cases 294].)

Query as to whether the results in these two cases may have been different if the reporting doctors had been a primary treating physician (PTP) and/or a Panel Qualified Medical Examiner (PQME). For instance, what if the PTP had made a permanent disability determination of 90% industrial factors and 10% non-industrial factors? And what if the QME had made a permanent disability determination of 10% industrial factors and 90% non-industrial factors? Would the Judge have found in favor of the doctor who determined that apportionment did exist when the other doctor determined it did not? The issue would turn on whether one or both reports constituted substantial evidence and which met the “bullet proof” checklist listed above. If both reports were considered “equal” in this regard, would the tie go to the injured worker’s favor?


When dealing with an issue of apportionment, prudent practitioners will use the “bullet proof” points discussed above as a checklist to determine if the reporting physician has hit all the marks. Depending on whether the attorney is applicant or defense, a deposition or supplemental report may be warranted to clarify the issues and to ensure the doctor has fully explained his conclusions.

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