California: Define Causation of Disability % and Nail Apportionment

By Hon. Colleen Casey, Former Commissioner, California Workers’ Compensation Appeals Board

One of the most common reasons evaluating physicians flunk the apportionment validity test is due to their tendency to conflate causation of injury with causation of disability. An easy way to avoid this problem is to adhere to a normal four-step progression of case development from AOE/COE (arising out of employment and occurring in the course of employment) to a final determination of permanent disability.

For the sake of brevity, I’ll be selectively pull-quoting facts and law from three recent WCAB Noteworthy Panel Decisions (NPDs) to illustrate how this process work.

CASE #1 - Cervantes v. Milgard Mfg., 2024 Cal. Wrk. Comp. P.D. LEXIS 234

STEP #1 – AOE/COE?

There is an industrial injury in this case. The parties admitted that on 2/11/2016, Ruben Cervantes, working as a window installer, sustained an industrial injury to his lumbar spine, as well as to other body parts.

STEP #2 – What Was the Mechanism of the Injury?

“Mr. Cervantes sustained an injury when he was lifting a heavy window that weighed approximately 300 pounds. He was being assisted by a co-worker; however, as they lifted the window his co-worker lost his grip and he was left holding most of the weight.” (Report of AME Steven B. Silbart, M.D.,11/3/2020)

STEP #3 – Determination of WPI to Be Converted to Permanent Disability?

In order to calculate applicant’s lumbar permanent disability (PD) rating, Dr. Silbart refers to the Range of Motion (ROM) metrics found in Table 15-7 at page 404 of the AMA Guides. The description of applicant’s lumbar disability is “surgical treated disc lesion with residual, medically documented pain and rigidity,” which can be found in Table 15-7, Disorder Category II, subsection “E.” The assigned WPI (whole person impairment) value for this disability is 10%, with an additional 2% WPI for additional lesions.

STEP #4 – Assign a % of Industrial Causative Factors and a % of Non-Industrial Causative Factors of Disability

The task for the AME at this point was to determine what % of the permanent disability in the form of “surgical lesions” was directly caused by the industrial source and what % of the permanent disability in the form of “surgical lesions” was directly caused by non-industrial source(s).

The AME’s apportionment determination was:

• 90% of the disability to the industrial causes and
• 10% to non-industrial pre-existent degenerative disc changes.

This was determined to be invalid apportionment of disability. Why? Because, the AME attributed non-industrial factors, i.e., pre-existent degenerative disc changes as a partial cause of the injury of 2/11/2016. Nowhere in his report does the AME explain how the pre-existent degenerative disc changes were in any way a partial cause of applicant’s disability which were the “surgical lesions.” Since the AME apportioned non-industrial factors to the cause of the industrial injury of 2/11/2016 and NOT the industrial disability, the apportionment was invalid.

“Causation of injury” is an AOE/COE issue and does not usually contain the same factors of analysis as “causation of disability” which relates to apportionment.

As the WCJ explained in part, “These surgical lesions account for 100% of the Applicant’s lumbar disability. His symptoms and loss of ROM were the result of industrial factors. While certain unexplained and asymptomatic degenerative conditions could have existed, there is simply no explanation as to how they contribute to the present disability. The disability is caused by loss of ROM and surgical lesions described in Table 15-7. Dr. Silbart may have felt that degenerative conditions may increase vulnerability to injury, but he does not explain how they presently cause any of the present disability.”

The latter analysis was critical for a viable apportionment to disability.

CASE #2 - Arias v. Williams Roofing Co., 2024 Cal. Wrk. Comp. P.D. LEXIS 29

STEP #1 – AOE/COE?

The parties admitted that on 6/19/2006 Roberto Arias, working as a roofer, sustained an industrial injury to his lumbar spine, as well as other body parts.

STEP #2 – What Was the Mechanism of the Injury?

On 6/19/2006, Mr. Arias fell 9 feet from a roof and onto his buttocks. (See Report of AME Dr. Miner “diagnosis section.”)

STEP #3 – Determination of Permanent Disability?

In her 2/8/2020 report, AME Dr. Miner identified applicant’s orthopedic disabilities as follows:

Traumatic spondylosis, particularly at L4-5 with 4-5 cm disc herniation, left paracentric with bilateral foraminal stenosis (left neuroforaminal. obliteration). Left L4-5 hemilaminotomy, medial facetectomy, and discectomy.

STEP #4 – Assign % of Industrial Causative Factors and % of Non-Industrial Causative Factors of Disability (NOT INJURY)

At this point, AME Dr. Miner should have assessed the % of disability directly caused by the industrial fall and the % of PD directly caused by non-industrial source(s).

Dr. Miner identified “Pre-existing congenital lumbar spinal stenosis” as a non-industrial factor of causation and concluded her apportionment analysis as follows:

In my opinion, when considering all medical issues of the current physical and orthopedic disability, it is with reasonable medical probability that apportionment is indicated. The approximate percentage caused by the industrial injury is 75% and the remaining 25% is secondary to the preexisting congenital lumbar spinal stenosis. From the anatomical standpoint, the patient has a narrowed lumbar spinal canal that places him at increased risk for disability due to trauma. Because the fall itself was significant, from a reported 9 feet, there is a greater contribution to causation resulting in the single level traumatic disc herniation of 4-5 mm than that of the spinal stenosis alone.

Unfortunately, as in the NPD described above, the doctor determined potential non-industrial causes of injury but did not determine potential non-industrial causes of disability, as the WCJ explained as follows:

In concluding that 25% of applicant's lumbar spine disability is secondary to preexisting congenital lumbar spinal stenosis, i.e., a narrowed lumbar spinal canal that placed applicant at increased risk for disability due to trauma, Dr. Miner actually apportioned to the cause of applicant's industrial injury — he was at increased risk of injury due to his narrowed spinal canal - rather than to the cause of applicant's disability at the time of Dr. Miner's evaluation. In doing so, Dr. Miner mistakenly equated a contributing factor in applicant's industrial injury to a contributing factor in his post-injury permanent disability. This is not substantial evidence of apportionment, because the analysis of the issues of causation of injury and causation of disability is different in this case. The fact that applicant had a narrow spinal canal that may have made him more susceptible to injury in the first place does not mean that his narrow spinal canal is causing permanent disability now.

CASE #3 - State of CA v. WCAB (Ham) (2019) 84 Cal. Comp. Cases 1006 (writ den.) (5th DCA)

STEP #1 – AOE/COE?

There is an industrial injury in this case. The parties admitted that on 6/4/2009 Dores Ham, working as a janitor, sustained an industrial injury which resulted in a partial amputation of his left foot.

STEP #2 – What Was the Mechanism of the Injury?

A blister on applicant’s left foot due to applicant’s work boots, became infected after subsequently contracting Methicillin-resistant Staphylococcus aureus (MRSA), which then required a partial left foot amputation.

STEP #3 – Determination of Permanent Disability?

Partial amputation of left foot which equates to 28% level of PD.

STEP #4 – Assign % of Industrial Causative Factors and % of Non-Industrial Causative Factors of Disability (NOT INJURY)

In this case, internist Dr. Allems and orthopedist Dr. Devor served as AMEs in this case. Both AMEs agreed that applicant’s preexisting diabetes was at least a contributing factor to applicant’s industrial injury. But for the preexisting diabetes, applicant would not have needed surgical treatment for his blister which resulted in the MRSA infection and the ultimate need for a partial foot amputation.

The case went to trial with the following result:

Here, the WCAB panel majority noted, it was undisputed that Applicant had diabetes prior to starting his employment with Defendant and that the diabetes was a contributing factor regarding the MRSA and ultimately the left foot partial amputation. However, Dr. Devor and Dr. Allems agreed that the diabetes was not a contributing factor to Applicant’s orthopedic impairment. Both doctors found that Applicant’s diabetes was a contributing cause of the need for the amputation and the amputation caused the orthopedic impairment. On this basis, the doctors concluded that Applicant’s orthopedic disability should be apportioned between the work injury and the diabetes. However, the WCAB noted, medical treatment is not apportionable.* Moreover, neither doctor explained how and why Applicant’s diabetes was causing PD, or how and why it was responsible for the percentage of disability they assigned. The WCAB panel majority concluded that the doctors’ apportionment opinions were based on incorrect legal theories and did not constitute substantial evidence.

* (See Granado v. WCAB (1968) 33 Cal. Comp. Cases 647 “medical treatment is not apportionable.” See also Hikida v. WCAB (2017) 12 Cal. App. 5th 1249 [82 Cal. Comp. Cases 679]

Conclusion

The common denominator among all of these cases appears to be that the doctors did not adequately explain how non-industrial factors were a contributing cause of applicant’s disability. Instead, they conflated “cause of injury” with “cause of disability,” which resulted in invalid apportionment.

Query as to whether the outcomes in each of these cases above might have been different if the deposition of the evaluating physician had been taken?

Before a deposition on this topic is taken, I’d recommend re-reading both the California Supreme Court case of Brodie v. WCAB (2007) 40 Cal. 4th 1313 and the WCAB en banc decision of Escobedo v. Marshalls (2007) 72 Cal. Comp. Cases 336, which include everything you need to know about apportionment but were afraid to ask. Perhaps bring a copy of each case along for the physicians to read as well. At the deposition, the attorneys could take a “deep dive” into exploring the true identity of applicant’s disability. Next, the physician should explain whether there were any non-industrial factors that might be responsible for causing that disability. And, if so, “how and why” the non-industrial factors are linked in that way. It might not bullet proof your apportionment analysis, but you’ll certainly increase the odds substantially.

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