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Industrial Causation to Injury, Disability and Evidence-Based Medicine
by Michael McDonald

In this series, Michael G. McDonald, Esq. of the McDonald Law Corporation offers practical advice to WC lawyers and adjustors.

Causation, what is it? It is not a word customarily used in newspapers or on the street. It is a term of art in workers’ compensation determining the liability of an employer for injury under Labor Code §3600(a) and apportionment of permanent disability under Labor Code §§4663 and 4664.

Evidence-based medicine (EBM), how is it used and when should it be used in our California workers’ compensation system?

Causation and Industrial Injury

It has long been held that employment and an industrial injury must be linked in some causal manner. The causal connection between the employment and the alleged injury need not be the sole cause of the injury. However, the connection must be a contributory cause of the injury. Maher v. WCAB (1983) 48 CCC 326.

This theory encompasses situations such as idiopathic seizures and falls. The leading case on point is Employers Mutual Liability Ins. Co. of Wisconsin v. IAC (Gideon) (1953) 18 CCC 286. In that case, the defendant was found liable for injuries sustained from hitting the ground at work, even though the applicant’s seizure was not industrial. The issue was what injuries did the applicant suffer from the fall?

There are many instances where we, defendant and applicant advocates, request a doctor for an expert opinion on whether an incident caused an injury. Recently, I had a well-known AME tell me at deposition that a four year old incident (a fall) which caused no injury or impairment two years after the incident, now resulted in a low level of permanent disability to the hip and the need for a potential hip replacement.

When asked how he arrived at that conclusion in light of the fact that all tests were negative two years prior, the AME advised that it just made sense to him. Were there tests which could be performed to determine whether the present condition was non-industrial? Yes, bone scans and blood tests could be used. This was important information since the applicant had other significant arthritic issues to other body parts which had been diagnosed as hereditary and pre-existing.

As advocates for our clients, we need to challenge the “experts” to support their opinions with the use of evidence-based medicine methods and relevant facts. It has long been held that medical opinions superseded by more reliable medical opinions are insufficient. Jones v. WCAB, (1968) 33 CCC 221. Where a physician fails to examine the worker, but bases an opinion on review of other medical histories, the opinion is not substantial evidence. Sweeney v. WCAB (1968) 33 CCC 404. Contra, Bethlehem Steel Corp. v. WCAB (Compani) (1982) 47 CCC 1283 (writ denied).

If an expert’s opinion is based upon incorrect legal theories or does not rely upon relevant facts, the opinion is not substantial evidence. Bracken v. WCAB (1989) 54 CCC 349.

Evidence-Based Medicine

EBM really came into the limelight in California with the adoption of SB 238 and AB 227 in 2004. Up until that time, the WCAB typically utilized the “years of experience” theory or the “because I said so” theory of the doctor to support a finding. These theories are still expressed by many of our hearty medical examiners to support their opinions. Now, we see the use of EBM through ACOEM, Utilization Review and Official Disability Guidelines (ODG).

Although the above-referenced guidelines are utilized for treatment, EBM can be used to analyze causation of injury, as well as apportionment of permanent disability.

An EBM analysis requires a review of the factual evidence; review of the epidemiologic data to support a relationship with industrial causation; evidence of industrial exposure; and review of other relevant factors.

Is there evidence of disease? Is the diagnosis correct? Does the evidence support the diagnosis? These questions need to be asked of our experts, especially if there is a conflict in the medical record.

What epidemiologic data/evidence exists for the disease or condition? Do the data support a relationship with work? Again, what outside resources has the medical examiner reviewed to support the expert opinion? Is the scientific evidence reliable? Is there empirical testing? Is it peer-reviewed? What is the known or potential error rate in the operation standards? Is there a general acceptance of the data/theory/technique in the scientific community?

What predominantly objective evidence exists to support the level of occupational environmental exposure which could cause the disease? What are the frequency, intensity and duration of the exposure? Where did the expert get the information?

What other relevant factors are present in the case? What individual risk factors other than occupational exposure exist? Could those risk factors contribute to the development of the disease or condition?

Finally, the practitioner needs to question the expert on what conflicting evidence, if any, exists which suggests the assessment is inaccurate? The practitioner needs to have specific facts available to question the expert at deposition. Further, many of our experts typically set aside up to two hours for deposition. The questions relating to EBM may require much more additional time, especially if the goal of the deposition it is to discredit the expert’s opinion.

Keep in mind that the manner in which the expert provides an opinion not only determines whether the opinions are adequate, but whether the opinions are persuasive. People v. Bassett (1968) 69 C2d 122.

Causation of Permanent Disability/Apportionment

Apportionment limits the liability of the employer for an injured worker’s permanent disability. Employers must compensate injured workers only for that portion of permanent disability attributable to a current industrial injury, not prior injuries or non-industrial factors. Brodie v. WCAB (2007) 72 CCC 565; LC 4663, LC 4664.

Escobedo v. Marshalls (2005) 70 CCC 604 (en banc) requires consideration of the cause of permanent disability. Examiners are required to make an apportionment determination by finding the approximate percentage of the permanent disability caused by the direct result of the industrial injury, as well as other causative factors before and after the industrial injury. The opinion must be framed in terms of reasonable medical probability, must not be speculative, and must be based upon pertinent facts, adequate examination and history. The examiner must explain the how and why of the apportionment opinion.

The courts have validated the Escobedo analysis. See Andersen v. WCAB (2007) 72 CCC 389; SCIF v. WCAB (Echeverria) (2007) 72 CCC 33; E.L. Yeager Construction v. WCAB (Gatten) (2006) 71 CCC 1687.

The practitioner needs to review the causative source of an injured worker’s disability and determine whether the medical expert’s opinion does not merely pay lip service to Escobedo, but actually follows the analysis. The physician must analyze the reason for the disability.

For instance, in osteonecrosis cases, the medical expert must determine whether the condition was pre-existing and a causative source of the current disability. In other words, the reason for the disability, including pain and limitations resulting from hip replacement, is a factor to be considered in the apportionment determination. See Malcolm v. CNA Ins. Group (2008) 36 CWCR 176.

This approach may be used in any number of cases. In all cases, EBM should serve as the basis for analysis. In cases of degenerative disc disease for instance, what x-ray evidence indicates the existence of the disease process? What individual risk factors exist which contributed to the disease process? How long has the disease process existed? Were there any post-injury factors which could have been a contributor? If so, what factors exist?


Our disability system for injured workers has changed. We need to change with it. Whether one represents the injured worker or the employer, we need to focus our efforts for clear, persuasive and substantial reports by utilizing EBM tools, such as ACOEM, ODG and UR opinions. Whether to use an Agreed Medical Evaluator (assuming the AME will split the baby on causation of injury and apportionment) is a topic for another day.

Today, however, we deal with Labor Code §4663(a): Apportionment of permanent disability shall be based on causation. This requires an analysis of the causal factors of that disability.

> How to Get the PTP Paid
> Defense Perspective on Causation
> Medicare Set Aside Myths
> Ogilvie Tips
> Ogilvie and the Vocational Expert
> Ogilvie Trial Brief
> Editor's Rant: Limping into 2010

About the Author:

Michael G. McDonald is the founder of McDonald Law Corporation in Concord, California and a Certified Specialist in Workers' Compensation Law, State Bar of California. He is a Director for the California Workers’ Compensation Defense Attorneys Association.

Michael G. McDonald, Esq.
McDonald Law Corporation
1800 Sutter Street, Suite 430
Concord, CA 94520-2563
Voice: (925) 363-4380
Fax: (925) 363-4352
Other locations: Sacramento, San Jose and Fresno www.mcdonaldlawcorp.com

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