Have you ever wondered how or why it was decided that Cobb angle had to measure greater than 10 degrees in order for a spinal curvature to be formally diagnosed as a scoliosis? Or why bracing is recommended at 20 degrees, and surgery at 40?
To answer this question, we look to an article published back in 1977 in the Clinical Journal of Orthopedics by Dr. William Kane, titled “Scoliosis prevalence: a call for a statement of terms.”
First, Dr. William Kane MD explained the problem that led to his publication of the article:
“Recently published prevalence studies of scoliosis reveal a disconcerting variability, largely due to the use of different diagnostic "cutting points,” which are frequently unstated.”
Stating the problem in other words, scientists and doctors were using different cut-off points for what they considered to be a “real” scoliosis. This led to different points of view, where some individuals were claiming that, out of every 100 people, 16 had scoliosis, and others insisting that only 3 people out of a 1,000 had scoliosis. Furthermore, scoliosis screenings were detecting either very few cases of scoliosis, or quite a few, depending upon who was performing the screening and what their standards were. Dr. Kane was attempting to standardize the management of scoliosis by introducing specific points at which observation, bracing, and surgery would be recommended.
To solve this problem, he used a form of statistical analysis called a “log normal distribution,” which was a graph intended to predict what the prevalence of scoliosis of a specific degree would be in any given population. He accepted as fact that 5 people out of 1,000 would have a 20 degree Cobb angle, 2 would have a 30 degree Cobb angle, and 1 would have a 40 degree Cobb angle. He was then able to extrapolate to conclude that 23 out of 1,000 would have a curvature of 10 degrees or more, and 77 would have a curve of 5 degrees or more.
Dr. Kane recognized the arbitrary nature of the cut-off points he selected, when he stated:
“To further define the adolescent scoliosis population, I would like to present certain statements which are admittedly arbitrary and may be contested; at the least, they offer a clear-cut basis for further discussion:
Dr. Kane’s quest to standardize the definition of scoliosis was a noble one, and certainly necessary. However, his first point (“scoliosis of 20 degrees in an immature individual is deserving of treatment”) is worth a closer look.
We can see today how the consequences of this policy have carried through the years; to this day, traditional orthopedic management of scoliosis involves waiting to brace until 20 degrees. If asked, many doctors might tell you they refrain from prescribing bracing until the scoliosis has progressed to this point to spare a teenager the social and emotional distress that can accompany wearing a brace; others, perhaps out of the belief that a mild scoliosis has little effect upon a person’s health.
But the bottom line is that the reason why an 11 degree curvature is called a scoliosis, but a 9 degree curve is not – or why treatment might be recommended at 20 degrees, but not yet at 12 – is not based around scientific evidence showing that a person’s health is harmed by a 15 degree Cobb angle but a 5 degree Cobb angle is harmless. It’s not based around data showing that 10 degree curves will not respond to treatment, but a 20 degree curve will. It began with one scientist’s “admittedly arbitrary” opinion, and the tradition of treating scoliosis in this manner continues to this day.
It is interesting to consider what the consequences of adopting a Cobb angle of 5 degrees might have been; indeed, Dr. Kane considers this in his paper:
“The consequences of a public pronouncement that the scoliosis rate is 160 per 1000 are considerable. With a total population of 211 million, it would mean that 33 million people in the United States have scoliosis and that it is as prevalent as hypertension or diabetes mellitus.”
Perhaps more interestingly, even back in 1977, Dr. Kane was concerned how the media presented scoliosis in articles such as “A Dangerous Curve,” published in TIME magazine in 1975. The media often focuses upon those individual cases which it considers “news-worthy,” which are often outliers or extreme examples of the condition, and not necessarily representative of the common experience with scoliosis. It’s quite obvious that not every case of scoliosis progresses to the point where it becomes “life-threatening,” as stated in this TIME article, and he was concerned that diagnosing too many individuals with scoliosis could be seen as misinformation, leading people to, “reject all information regarding the problem of scoliosis, rationalizing its rejection by deciding that the information provided by the experts in scoliosis is incorrect and contrary to easily observable facts.”
But now, almost 40 years later, is there reason to re-visit Dr. Kane’s conclusions? Do we have new information to suggest that revising traditional practice might be appropriate? Here we have a quote from a study that was published in November of 2015 in Spine, one of the world’s most prestigious scientific journals:
“Adolescent idiopathic scoliosis is present in 3-5% of the general population. Large curves are associated with increased pain and reduced quality of life. However, no information is available on the impact of smaller curves.”
Looking at 3,184 fifteen year-olds, they found small curves in just over 10 percent. They found that, “those with spinal curves were 42% more likely to report back pain… had more days off school, and were more likely to avoid activities that caused their pain.”
“[S]mall scoliotic curves may be less benign than previously thought. Teenagers with small curves may not present to care, but are nonetheless reporting increased pain, more days off school, and avoidance of activities. These data suggest we should reconsider current scoliosis screening and treatment practices.” [emphasis added]
This is a very significant finding. It suggests that we should re-consider whether or not small, mild cases of scoliosis should truly continue to be ignored and dismissed as nothing more than a minor cosmetic issue with no effects upon health. While bracing may not be appropriate for these smaller curves, perhaps efforts could be devoted to developing a treatment method that can reduce back pain and improve the quality of life for people suffering from scoliosis…
(*cough cough* CLEAR chiropractic! *cough cough*)
Although 10 degrees is the cut-off point for scoliosis and 20 degrees is when bracing is recommended, it is important to emphasize that these are arbitrary numbers. An individual with a very small curve CAN have pain that is directly attributable to scoliosis. Kurt Cobain of the band Nirvana suffered from a mild scoliosis which caused him a great deal of pain, perhaps leading him to self-medicate and eventually to his early death by drug overdose.
Don’t let scoliosis slow you down – even mild curves can have an impact upon your life. Contact your local CLEAR doctor today!
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