Friday, 20 September 2013

Why does spine surgery increase impairment?

In the world of compensation and impairment ratings there is a bible known as the AMA Guides to the Evaluation of Permanent Impairment. The “Guides” aren’t perfect, but I have one major criticism: that the impairment rating for spinal conditions is linked to having surgery, such that surgery (that is undertaken in order to reduce impairment) increases the impairment rating. I will take you through the twisted logic, but it makes as much sense as awarding no impairment for someone crippled with knee arthritis, and then awarding a high impairment rating after they have had their knee replaced and their function restored. This paradox is helping surgeons and lawyers, but does little for the patients except to increase their payout.

The “Guides” (as they are referred to) are used to calculate impairment ratings. These ratings, expressed as a percentage of the whole person (“WPI”: Whole Person Impairment), are used to calculate compensation payments.

A simple example of how they work: if an employee loses his left arm between the shoulder and elbow, the Guides tell us that this equates to a 60% WPI, whereas a below-knee amputation rates 28% WPI. Under specific compensation systems, this is converted to a dollar equivalent that represents the compensation payment to the worker. It is better than the old system where doctors just estimated a number for WPI, because different doctors would estimate wildly different numbers that often depended on who was paying them for the assessment. Using the Guides is more objective. There are still arguments over the ratings, but usually in more complicated cases and usually the arguments are over smaller differences in assessment than were previously seen.

Now to the problem at hand. Two cases are described below based on what actually happens using the Guides.

Case 1: A bad knee.
If you have severe arthritis in your knee, perhaps secondary to a previous fracture at work that didn’t heal too good, you would get a WPI rating based on the assessment of your knee function. If it is severe, that rating may be up to 20% WPI. If you have that knee treated with surgery such that you are now able to walk long distances unaided, comfortably and with no instability or deformity in the knee, your impairment rating would (understandably) go down, perhaps to about 5%.

Case 2: A bad back.
First, put aside reservations about chronic back pain and its causes, and play along with the widely held view that work somehow causes degenerative changes and that back pain is somehow related to degenerative changes. If someone has degenerative changes in their back (as most of us do) and complains of back pain and loss of function, then without any obvious traumatic injury to the spine (like a fracture or dislocation) or any nerve involvement, they will be rated a 0% WPI according to the Guides. This is because there is no identifiable pathology to explain their pain, and pain alone is not an impairment (impairment is a loss of function). If that person undergoes a spine fusion for their back pain (again, set aside the fact that they are very unlikely to get better with such treatment under a workers compensation system) their WPI rating will increase to at least 20%. That’s right, surgery that is ostensibly performed to improve the patient’s condition automatically results in a large increase in WPI and, therefore, monetary payment to the worker. This increase in payment corresponds to a proportional increase in payment to the lawyer representing the worker, and to a massive increase in payment to the surgeon (compared to non-operative management).

What’s wrong
The fact that an operation designed to improve a patient’s lot automatically results in an increase in their impairment rating doesn’t make sense. The logic behind it is that if they had the operation, they must have lost “motion in a motion segment”. However, a spine fusion (of one segment) does not result in a clinical loss of motion or any measurable impairment in movement, so this should not be used to justify an increase in the impairment rating.

The bottom line
The impairment rating for spine fusion surgery is not just illogical, it is backwards. It provides a perverse incentive to have surgery due to financial interests for multiple parties. I always thought that medicine could make you worse, now I guess it is official.                                                                                                                     


  1. Hi Doc S.
    I suspect in your haste to find fault with spinal surgery (again) you may have misinterpreted the definition of "loss of motion segment integrity" from the AMA guides.
    I refer here to the 4th edition as used in my home state of Victoria, and most other states of Australia, utilising the Diagnosis Related Estimates (DRE) model of assessment, again, as used throughout Australia. Page 98, under the heading "Loss of Motion Segment Integrity", defines the term using several paragraphs that describe not a spinal fusion, but instability - that is, increased motion at a spinal level, as may happen following a traumatic spinal injury.
    Table 72 on page 110, "Lumbosacral Spine Impairment Categories", where you probably obtained the 20% WPI, also quite clearly refers the reader to the same section of the book I have just described. It's a shame you didn't check your definitions.
    The only table that refers to postoperative status is Table 75, which is part of the Range of Motion Model (not used in Australia), where a single level fusion, even with residual signs, is given 12% WPI. Again, that system isn't used in Australia.
    As an AMA certified impairment assessor, I had to complete a course on how to use the AMA guides in order to understand them and be familiar with them. It's a shame you've written this blog post clearly without having completed the same course, or even checking your definitions.

    1. Thanks for commenting John,
      I did the course. I am an AMA certified assessor. I checked the definitions. DRE IV (20-23% WPI) includes "may have complete or near complete loss of motion of a motion segment due to developmental fusion, or successful or unsuccessful attempt at surgical arthrodesis [fusion]".
      I am not sure of the objection. It is very well known that a spinal fusion puts you into DRE group IV (20-23% WPI), but back pain without signs or instability puts you into DRE group I (0%WPI). It is often raised as an issue from insurers that spine fusion surgery increases their costs because of this very classification system.
      I will grant you that I should have said "loss of motion of a motion segment" rather than "loss of motion segment integrity". I have now changed it but wording aside, this does not change the primary problem that spine fusion for back pain puts you into an increased impairment category.

    2. Hi Dr Skeptic,

      I am currently writing a research paper on the ethics behind placebo surgeries and have found much valuable insight from your website however I do not know your actual credentials. I was wondering if you could respond so I can find them out and possibly use your insight in my paper!

      Thank you,

      Pharmacy Student

    3. Please see my response to you or someone similar on "Is back surgery just a placebo?" (

      If you are writing about the ethics behind placebo surgery, you need to look at the literature, much of which is referred to in this blog, but all of which is easy to find. My qualifications are not relevant to the ethics, nor are they relevant to the validity of anything I say.

    4. Argument from authority is a common argument form which CAN be fallacious, such as when an authority is cited on a topic outside their area of expertise, or when the authority cited is not a true expert. Wiki

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  3. Thank you for your interesting blog. The rationalization of medicine seems to have diminished serious skepticism of medicine. As your blog highlights, that's rationally rather strange. The effect seems to me to be mainly institutional and discursive. Rational scepticism of medicine lacks institutionalized financial interests. It has also been discursively marginalized. Historically, anti-medical satire had a relatively high discursive profile. Some analysis:

    1. Thanks for the comment and link to your blog. Nice to know that skepticism of doctors is not new. Good comment about the lack of financial interests in rational skepticism. I need a generous philanthropist to fund some of my research - one that can see beyond donating to the nearest research laboratory.

  4. I am a patient that recently had a two level fusion. You may be expert examiners but I think that you both need to walk a mile in a patient's shoes before writing your blogs. I know that although my surgery has greatly reduced my pain thatI have lost some mobility in my neck. I also know that my doctor informed me before surgery that I could end up having more surgeries in the near future.I have no received an inpairment rating yet. But is coming very soon. My point is I don't care about ratings. I care about this. Will I be able to return to my job as a CNA and safely do my job. That is my major concern. Too bad doctors and people like you only focus on money. No amount of money in this world is worth any disability that affects your life period. I was an extremely active person before my surgery. Now not as much. But I have not and will never as long as I breath give up trying to improve my quality of life.

    1. Your point about me only focusing on money is wrong. I rarely mention it in any posts. This one relates to impairment (which relates to compensation) but the outcomes I refer to are usually quality of life, pain, function and complications. These are the outcomes important to patients.

      My recurrent point is that people often get better (feel better, return to work, whatever) after ma y treatments for many conditions. We are not being scientific if we attribute every improvement to every treatment. So often, as highlighted in this blog, the APPARENT cause and effect association between treatment and outcome disappears on proper testing (e.g. comparison with placebo).

      My point in this post is different: according to the AMA5 impairment guidelines, your level of impairment (now that you have been treated and improved) is now much higher than when you had pain (pre-surgery), and that makes no sense at all.

  5. With all due respect, your assessment of an actual whole person impairment post cervicle spine surgery is simply ludicrous. Your assertion is that a person with a diagnosis in which fusion surgery is recommended is somehow "better" after having the invasive procedure. The procedure may or may not improve pain and or quality of life, but what it undoubtedly does is forever alter the persons cervicle spine in such a way that segments above and or below the segment fused cannot function within its normal range of motion without over pressure assuring the person of future fusion procedures. The cycle then repeats.

    Where I think your logic is mostly twisted is that you seem to be aligning your position with the fusion procedure's ability to somewhat alleviate pain symptoms to also improving the biomechanical aspects of the person's cervical spine. Neither are true. The spine is FOREVER altered and will, as a result, degenerate at an accelerated rate. So, to my point, the WPI is smartly increased with invasive surgery and that increase Is not directly related to any subsequent relief form said surgery, but takes into account the damaged person's future outcomes of which they cannot be and will not be compensated for.

    1. Thanks, Interesting points. But I am not clear. Does the spine surgery make the person's life better or worse? If it improves their life, why should their compensation / disabiltiy / impairment increase? If the surgery is ultimately detrimental to their health, why is being done? And remember, this is a very 'discretionary' area where surgeons vary greatly in their opinions on who should and should not get a fusion and on the effectiveness in this environment (compensation).

  6. i have had c6and7 fusion 4 yrs ago seems ok with pain now i need an s1andl5 fusion and was told i will be on 40 pound restrickion for rest of my life im 51 years old havent worked for 12 months what my prognosis