Blog Topic: Development of a Treatment Matrix for Adolescent Idiopathic
Scoliosis (IS)
4-19-2023
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.
