Blog Topic: Development of a Treatment Matrix for Adolescent Idiopathic Scoliosis (IS)
The following post is an abridged version of a PowerPoint talk I recently presented to the Washington University School of Medicine Orthopaedics Residents on 3-21-2023.
It is important to understand the purpose of this talk is to present these big treatment topics in a high-level manner, a 30,000 foot view, to provide a framework to think about how to treat idiopathic scoliosis patient, in general. The treatment matrix demonstrated is not intended for treatment of an individual patient, and consultation with a pediatric orthopaedic spine deformity surgeon is required.
In idiopathic scoliosis, the main two factors which guide how we should treat are:
#1: The amount of growth remaining
#2: Magnitude of the deformity
The amount of growth remaining is nicely demonstrated in the below diagram, whose data comes from Dimeglio. This post is on the ADOLESCENT with idiopathic scoliosis, so we are focusing on the area the right side, in the yellow box, starting at 10 years of age. When we talk about the amount of growth, it is the area under the curve which describes the amount of spine growth.
So how do we determine where each patient sits on the previous diagram? The easiest way would be to use the patient’s chronologic age, unfortunately, use of the patient’s chronologic age has been shown to be inaccurate. The most accurate method is to use bone age, which is assessment of the growth plates in the body. For scoliosis, this has classically been determined by the Risser sign, which evaluates the iliac crest growth plate and is graded 0 to 5 (0 = very young; 5 = growth completed). Several years ago an improvement in this assessment was developed by Dr. Jim Sanders, using radiographs of the hand. The Sanders method is graded from 0 to 8, which more accurately determines the amount of growth remaining (especially in the younger children). The reason the amount of growth is important is that this is directly correlated with the risk of scoliosis worsening or progressing. More spine growth spine remaining = higher risk of scoliosis worsening
The second factor, magnitude of the deformity, is equally important as the first factor. The two patients above, have very different deformity magnitudes and thereby may have different potential treatments.
The first study which evaluated the importance of the magnitude of the deformity was published by Lonstein and Carlson in 1984. This study not only reported the importance of the curve magnitude, but also used growth remaining as a critical factor in curve progression risk. This study established the concept that a curve which is > 25 degrees is a curve which is at risk to get worse and is then classified as “progressive”, and active treatment (as opposed to observation) should be initiated.
Building upon the Sanders classification, and incorporating the magnitude of the deformity the study by Sanders et al improves the accuracy of curve risk prediction. Examine the large diagram above, the boxes in light grey are those patient groups which had a low frequency of deformity progression, while those in white had a high frequency of deformity progression. If we distill this down the information (upper right corner) in this diagram we can create an easy to remember concept (using the standard surgical indications for a posterior spinal fusion of 50 degrees):
If curve is > 20 degrees and Sanders 2
If curve is > 30 degrees and Sanders 3
If curve is > 40 degrees and Sanders 4
So, if a patient meets one of these 3 criteria, then the likelihood of progressing to greater than 50 degrees, and needing a posterior spinal fusion is HIGH.
The next step is to create a Treatment Matrix, using the concept of Growth Remaining (using Sanders grade) and Curve Magnitude. This Treatment Matrix is a synthesis of the published research literature, so there will be a little +/- to the curve magnitudes (+/-5 degrees) and Sanders Grades (+/- 1 grade).
So, in the first group to discuss, specifically curves < 25 degrees, based on the study of Lonstein and Carlson, are not considered “progressive”. These curves are not generally actively treated, and will be closely followed every 4-6 months.
The next group is the curves with magnitude level, 25 to 45-50 degrees.
The two subgroups here are Sanders 0 to 6+ and Sanders 7-8
In the Sanders 0 to 6+ group there is significant variation in progression risk. Why? Because there is a wide spread in the amount of growth remaining. Regardless of this however, in general, most of treatment for this group will be NONSURGICAL.
The nonsurgical care for the Sanders 0 to 6+ (25 to 45-50 degree curves) is bracing. For bracing to be effective a rigid thoracolumbosacral orthosis (TLSO) which is custom-designed to apply corrective forces to the spine is recommended, and to be worn for 18+ hours/day.
In the Sanders 7-8 group (25 to 45-50 degree curves), since there is little to no growth left in the spine, there is little progression risk, and observation is the most common treatment.
For curves 25 to 45-50 degrees and Sanders 0 to 6+ (green box), as demonstrated on the Treatment Matrix, newer treatment options have been developed over the last 5-10 years. These new technologies are called growth modulation surgeries, and currently techniques available are ApiFix and VBT (Vertebral Body Tethering). These technologies have significant potential to create a permanent paradigm shift in treatments for adolescent IS, but much more research is needed to fully understand the indications and complications of these technologies.
When the curves get to be </= 45-50 degrees bracing is no longer effective and now meets generally-accepted surgical indications. We just mentioned the growth modulation surgeries (ApiFix and VBT) previously, which can be options in moderate curves. However, as the magnitude increases the curves get stiffer and these new technologies do not work well. It in these larger curves and the moderate curves with little growth remaining that the preferred surgical treatment is a posterior spinal fusion (PSF).
As mentioned the growth modulation technologies, ApiFix and VBT, are under continuous evaluation and scrutiny to determine when they offer distinctly better outcomes with a low revision surgery and complication rates. It is likely that as time moves forward these growth modulation technologies will have expanded indications, so this red box in the matrix will likely increase in its size.
An additional point to make is the area on the matrix for curves from 40 to 50 degrees. This is the “fuzziest” area on the matrix, meaning there can be significant variability in the options for treatment, based on surgeon skill/experience, patient characteristics, tolerance of complications, etc…..
To conclude, this Treatment Matrix is a compilation of many scientific publications and clinical experience. It can be used as a “rough” guide to treatment options and is not intended to be substitute for a consultation with a pediatric orthopaedic spine deformity surgeon.
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