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.