Tuesday, January 10, 2023

 Blog Topic: Neuromuscular Scoliosis: Use of Magnetically-Controlled Growing Rods

1-10-2023

 

In the second-to-last blog post the concept of using Magnetically-Controlled Growing Rods (MCGR) was presented for treatment of NeuroMuscular Scoliosis (NMS). In that post the different cranial/upper and the caudal/lower foundations were discussed briefly, and the reasons for why we choose one type over another.  In this post the use of proximal screws and distal pelvic fixation will be presented.

 

Below is a 7 year old female with cerebral palsy and NMS.  Her parents have noticed she is curving her body more, is having more difficulty with sitting, and is not tolerating sitting for very long periods of time which makes travel and school participation very difficult.

 

Because this 7 year old girl had a progressive, severe spinal deformity which is impacting her quality of life, we entered into shared-decision making with parents around surgical options.  So, what are our goals of surgery?

#1: Correct spinal deformity

#2: Improve sitting

#3: Improve sitting intolerance/pain

#4: Permit vertical growth of the spine

The only way to address all 4 of these goals is to use a “growth-friendly” instrumentation, which is to use either a distraction-based construct or Shilla Growth Guidance Construct.  My present preference is to use a distraction-based construct in neuromuscular patients, though I am using Shilla Growth Guidance Constructs more and more.

 

The below radiographs demonstrate the flexibility of the spine deformity.  The Supine image is done with the patient lying on their back, simply taking gravity off the spine.  The Push Supine is also done laying down, but then there are two individuals using lead gloves to create three-point push on the body/spine to further improve the spine deformity. This Push Supine significantly corrects the deformity, and gives us a good idea of what type of correction will be obtained in surgery.  Hence, for this patient a distraction construct will provide good correction.

 

After the decision was made to use a distraction-based construct, the next step is to decide what type of actuator or lengthening mechanism can be used.  If the kyphosis is rigid on the lateral radiograph (far right radiograph, above) then we may not be able to use a magnetically-controlled growing rod, and use a traditional growing rod (TGR).  The downside to TGRs is the need for surgically lengthening in the operating room every 6 months.  However, if the kyphosis is flexible, then we can be fairly reassured that we can place a magnetically-controlled growing rod.  The below radiograph is a lateral radiograph, with the patient lying on a bolster, which causes the spine to hyperextend and if the spine if flexible the kyphosis will significantly improve.  As you see in the below radiograph, this spine has a very flexible kyphosis.

 

A magnetically-controlled growing rod construct, 2 rods, were placed from the cranial foundation of pedicle screws T2-T3-T4 down to two S-hooks on top of the iliac wings. As mentioned 2 blog posts ago, the cranial (top) foundation can be hooks on ribs or screws on the spine.  The placement of T2-T3-T4 pedicle screws, in this case, nice balances the very strong pelvic fixation of two iliac S-hooks.  The decision to use these S-hooks, rather than L5-S1-Iliac screws, was made to preserve the fixation points for the definitive fusion at, or near, the end of skeletal growth.

 

 

As you see above the growing rods nicely improves the oblique pelvis (left radiograph to the 2nd from left radiograph) and scoliosis.  The 2nd two radiographs on the right demonstrates the improvement of the kyphosis.

 

Three years after surgery (below) the spine deformity remains nicely corrected.

 

So how much did we lengthen the magnetically-controlled growing rods? The below pictures show the rods immediately after surgery and then at the 3 years after surgery time point.  The area identified in red is a distraction of 48 mm!

 

More to come on growing rods….

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