Trip to San Juan, Puerto Rico

 

Recently was in San Juan, Puerto Rico teaching surgeons about early-onset scoliosis and the use of the MAGEC system.  I had the opportunity to meet the attending pediatric orthopaedic surgeons Drs. Humberto Guzman, Pablo Marrero, Gladys Ramos, Onix Reyes, and Lissette Salgueiro.  Also in attendance was the upcoming complex spine deformity fellow at Columbia University (NY) and 6 Orthopaedic Residents from the San Juan residency program.  Extremely engaging meeting with this top-notch group.  Thanks to Benito Padilla for his hospitality.

Vertebral Body Tethering for Scoliosis

Since the first description of spinal fusions for the treatment of scoliosis over 100 years ago, there have been significant advancements in the surgical technique, which have led to improved fusion rates, lower complication frequency, greater three-dimensional correction of the deformity and more rapid postoperative recovery.  However, spine fusions mean fewer motion segments (less spine motion) which may lead to lower function in high-level physical activity (e.g. competitive athletics) and greater chance for spine arthritis. Hence preservation of spinal motion, particularly in the low back, is a highly attractive goal.  The desire to maintain spine motion has fueled the development of various growth modulation procedures, whose goals are correct the spinal deformity and maintain motion (without fusion).  One of these promising techniques which has gained traction in the last 10 years is vertebral body tethering (VBT).

The concept of VBT in scoliosis is to alter the relative vertebral growth (right vs. left) of the front of the spine.  This is accomplished by relative slowing the vertical growth on the convex side (by tensioning of the tether) with unloading of the concave side of the vertebra, to permit greater growth.  In order for growth modulation to occur the spine need to have enough spinal growth remaining.    

 This is a patient 4 days after VBT

At present in 2017 there is no FDA-approved devices for use in the U.S. in a nonfusion, growth-modulation technique in a skeletally immature patients.  This means the use of this tether system to the children and adolescents is in an “off-label” manner. 

Studies on VBT in animal models have demonstrated proof of concept that tethering of the immature spine can alter its growth.  The first description of VBT use in humans was a case report in 2010.  Reports of VBT use in children/adolescents have been encouraging with a low frequency of complications.  At present there is limited data available on the use of VBT in skeletally-immature patients with scoliosis. 

MAGEC (Part 3)

Follow-up on the reported complications of the MAGEC device.

In the last blog post three modes of failure of this device were described: rod breakage, actuator pin breakage (inside the device) and rod breakage.  It should be noted that with traditional growing rods, breakage of the rods is a common occurrence, so this problem is due to rigid rods taking the stress from a flexible child’s spine. Remember, all metals gradually fatigued over time as they are stressed by bending and twisting.  The smaller the diameter the rod the greater the chance of it breaking.

As mentioned in the previous blog the actuator pin, which is inside the device, has been re-engineered to be stronger.  Children who had their MAGEC devices implanted after the FDA clearance of this device have the improved, stronger MAGEC device design.

What are the outcomes of this new device?  Better, worse or the same?

Research in Early-Onset Scoliosis (EOS), like many areas of medicine, is very hard to complete.  For one thing it is a relatively uncommon problem in our population.  EOS also encompasses a wide variety of diagnoses, deformities types and severity.  The combination of being uncommon and highly variable patient to patient makes research challenging.  As such, it can be difficult for one surgeon or even one hospital to have enough patients to study a particular problem or treatment.  This is why many published research studies on EOS are from surgeon study groups, which are research collaborations between institutions around the world.  This permits surgeons to pool their data, unidentified to protect the patient, with other surgeons from around the world in order to get enough patients to study a research hypothesis. 

Since the MAGEC device has only been approved in the U.S. since 2014, the longest study follow-up in the U.S. is only a couple of years, too short to really help us at all.  The longer follow-up studies, which are really only intermediate length, are from Europe and Asia.  There are no comparative, long-term studies (>7 years) on the MAGEC device.  So we have to rely on short-term and intermediate-term studies on this device.

Most of the studies published and presented on MAGEC growing rods have reported similar radiographic outcomes when compared to traditional growing rods (TGR).  Correction of the spinal deformity and providing vertical growth of the chest appear to be overall similar.  However, there are many questions about the device longer-term such as:

1.       Will actuator failure frequency increase the longer the device is implanted?

2.       Will the spine become more rigid over time like is seen in traditional growing rods? 

3.       Is the MAGEC device cost-effective in it real world applications?  Each actuator costs as much as a new compact automobile, and typically two of these are implanted in each child.

4.       How much should the MAGEC device be lengthened at each office visit and how often should the device be lengthened? 

5.       Are the indications for the use of MAGEC devices the same as for TGRs?

We have many unanswered questions about the device, however the device appears to have more positive aspects than negative.

 

Is the surgery to place a MAGEC growing rod different than traditional growing rods (TGR)?

The surgical approach is the same for both procedures, but the big difference is the MAGEC rods are one long rod whereas each TGR is actually two short rods connected together.  So the MAGEC rods are much more difficult to place in a child, especially when the child is short, is thin and has a large spinal deformity.  The MAGEC devices need between 9 and 11 centimeters of relatively straight spine to place the MAGEC rod without it being too prominent under the skin.  Optimal placement of this device requires a high level of surgical skill with strong spine (pedicle screws) or pelvic fixation points.

How do I find a surgeon who uses MAGEC devices?

It is important to pick a surgeon who frequently cares for EOS as they can decide, based on their experience with all types of treatment options, if MAGEC or another type of surgery is optimal.

A good way to find one of these surgeons is to go the Growing Spine Foundation Website to find a center near you: https://www.growingspine.org/research/gssg

Our EOS spine centers at St. Louis Children’s Hospital (314-454-2045) and Shriner’s Hospital for Children, St. Louis unit (314-432-3600) are always willing to help.

MAGEC (Part 2)

In the last posting the MAGEC system for Early Onset Scoliosis was introduced.  This system is a significant improvement when compared to Traditional Growing Rods, mainly due to the ability to lengthen the instrumentation without the need for anesthesia or a trip to the operating room.  The benefits of this device are easy to see, but was with any new technology there are some drawbacks or limitations.  The MAGEC device is a cutting-edge, high-tech magnetic lengthener and complicated devices may not function as intended.  The MAGEC device requires a magnetic field from the ERC (shown below) to spin the magnets in the implanted actuator.

It is possible the distance between skin and the actuator is too great, making the magnetic field too weak to lengthen the actuator

 

 This can happen, in children with more subcutaneous fat, an older patient and if the actuator was deeply buried in soft tissues around the spine.  Personally I have had only one patient in whom the MAGEC device was unable to be magnetically lengthened.  The remaining 30+ patients in my practice with this device have been easy to lengthen.

The other problem with the MAGEC device was in breakage of the actuator pin.  If this happens the actuator will not lengthen with the ERC.  Several reports of actuator pin breakage have surfaced, with most of them being from Asia and Europe.  This is because the MAGEC system was first released overseas so there is a slightly longer experience with this device outside of the U.S.  This was also the first-generation of the MAGEC device.  When the MAGEC device was released in the U.S. the actuator pin design had been improved, creating a second-generation.  This is what we currently use in the U.S.  I have not seen any actuator pin breakage yet in my patient population. 

Another mode of failure of the MAGEC device is rod breakage, either above or below the actuator.  This type of failure is the same as what is seen in Traditional Growing Rods.  The metal rods are constantly stressed, or cycled, by the child on a daily basis.  These stresses are cumulative on the rods and will gradually weaken until there is a fracture or breakage of the rod. 

 

This problem can be partially avoided by using the larger sizes of the MAGEC rods, specifically the 5.5 mm rods instead of 4.5 mm rods.  However, due to patient size we cannot use 5.5 mm rods as the patient is just too small to hide the rods in their back without breaking through the skin or being painful.

MAGEC Growing Rods (Part 1)

In the last blog we talked about Growing Rods for the treatment of EOS.  The major downside to this treatment method is the need for repetitive anesthesia and open lengthening of the growing rods in the operating room.  Over the last 5 years there has been a number of studies assessing the impact of repetitive anesthetics in the growing child, specifically on brain development and behavior.  Despite the volume of research in humans and in animal models, there remains confusion as to who is at risk, what is at risk and the magnitude of the risk.  What we do know is that there is a significant amount of psychological stress on children, and the parents.

The other negative for traditional growing rods is the need for open lengthenings.  Every time growing rods are openly lengthened creates an opportunity for a deep wound or implant infection.  If infections involve the Growing Rods, they typically must be removed as it is very difficult to eradicate the infection (bacteria).  This means surgeons commonly must remove the Growing Rods, treat with antibiotics and then re-implant the Growing Rods at a later date. 

So it is easy to see that limiting the number of anesthetics the child is exposed to and minimizing the number of surgical procedures is optimal for the patients, and their families.  In the fall of 2014, a new device received FDA clearance for use in the U.S., the MAGEC (MAGnetic Expansion Control) system.  This new device is an actuator that can lengthen or distract when inside the patient, without the need for anesthesia or making an incision on the child.  This system permits lengthening of the growing rods without the need for anesthesia and open lengthening

The lengthening of the MAGEC rod is done by placing the device in a special magnet field.  The MAGEC rods can be lengthened painlessly in the clinic, without sedation or anesthesia.  In fact the lengthening of the MAGEC rods takes less than 1 minute by a device called an ERC or External Remote Controller, which creates the special magnetic field around the MAGEC device.

I have personally implanted 30 early-onset scoliosis patients with the MAGEC system; some patients were converted from a traditional Growing Rod system and others it was their first surgery.  This system has dramatically improved the ability to lengthen the growing rods, since even if the child is not well we can lengthen the MAGEC rods in the clinic.  Previously if the child had traditional growing rods, and was ill, their surgery may be cancelled because of concerns about their airway and breathing.  Also, as mentioned earlier, there is a lot less stress on the patient and family.  There is no need for placement of IVs, an anxiety-provoking and sometimes painful procedure, or general anesthesia so there is no post-anesthesia nausea and vomiting. 

 

However, MAGEC rods are not the answer for all patients with early-onset scoliosis.  The device can be difficult to place as it requires an almost perfectly straight area to be placed into the back, around 12 centimeters.  At first glance this looks like all patients would have a straight area to be able to place a MAGEC device, however it is not always the case in early-onset scoliosis.  Sometimes it is necessary to start with traditional growing rods and then change at a later date to MAGEC, after the child has grown more.

Growing Rods

As mentioned in earlier blogs, nonsurgical management of early-onset scoliosis (EOS), which can consist of bracing, casting, observation, and physical therapy is usually the primary treatment, especially for mild/moderate curve with no or mild progression.  Surgery for EOS is reserved for patients whose deformities are severe and/or progressive, and cannot be or have not been successfully treated with those nonsurgical methods.  The surgeon will evaluate the child’s spinal deformity, age, physical size, medical condition, and other factors when determining the need for surgery. 

One of mainstays in the surgical treatment of infantile/juvenile/early-onset scoliosis (EOS) has been Growing Rods.  These rods do not actually grow, like the child, but can be lengthened or “distracted” in the operating room on a routine interval, to straighten the spine.  This is much like jacking up a car to change a tire, the jack is the Growing Rod.  One difference is the jack/Growing Rod is implanted in the child’s back so it works 24/7 attempting to correct and maintain the child’s scoliosis in a straightened position.

There is a large volume of information published on Growing Rods, with the one of first major publications on their use in children in 20 years ago, by Klemme et al.  Since that time, Growing Rods have become the most common surgical treatment for EOS.  If one searches for “growing rods scoliosis” on PUBMED, the U.S. National Library of Medicine/NIH website for medical journal publication, there will be over 150 articles published in peer-reviewed journals.  There are many reasons for the acceptance of Growing Rods as the “gold standard” for the surgical treatment of EOS: abundant literature supporting their effectiveness, ease of use by surgeons, and the surgeries are well-tolerated by patient in terms of pain, function and outcomes. 

As mentioned above the Growing Rods achieve straightening of the spine by creating lengthening of the rods via a connector between two segments of rods.  So in actuality, as shown in the above radiographs, there are actually 4 segments of rods, two on each side with a connector between them.  The attachment sites of the Growing Rods to create the straightening effect can be on the spine, ribs or the pelvis, which are done with screws or hooks.  The nice thing about Growing Rods is that they are very utilitarian, because they can attach at a variety of places with several different types of bone anchors.  This is very helpful since each child’s spine deformity is unique and each can create challenges to safely treat.

 

This patient had fixation with screws at the bottom and the use of hooks onto 4 ribs on each side.

Prior to recent advances in EOS treatment with the MAGEC device, one of the less attractive aspects of Growing Rods is the need for operative lengthening.  These small surgeries are typically every 6 months, but like any other surgery on children requires the use of general anesthesia.  In addition in order to lengthen Growing Rods the surgeons needs to incise the skin, expose part of the spine construct and then lengthen or distract the construct.  The major concern with the creation of incisions is the risk for infections, both of the skin and also of the metal.  If a deep infection of the implants occurs, the metal typically needs to be removed and the infection treated with intravenous antibiotics. 

Once the Growing Rods have been implanted they are lengthened in the operating room about every 6 months.  This is usually continued until the child is at or near the end of their growth.  At that time the Growing Rods can be removed and converted to a definitive posterior spinal fusion, which would be the last planned surgery for the spine deformity.

What organ systems are affected by Early-Onset Scoliosis (EOS)?

Scoliosis, at any age, causes distortion of the body from the neck to the waistline.  Though on the x-rays (or radiographs) that are obtained to evaluate for scoliosis the spine only appears to curve in a lateral direction, however it actually has become deformed in three dimensions (front, side and axial).  The front view is shown below in the first x-ray or radiograph.  It is easy to see the severe curve, causing the right shoulder to be higher than the left, but also it is easy to appreciate the shift of the body to the right relative to the pelvis and hips.

As the spine starts to curve to the side it also twists on itself, and it is this twisting which causes the ribs to be differently oriented between the left and right sides of the body.  In the x-ray below one can also appreciate the difference in the ribs, both in their position, shape and spacing.  The ribs on the left side are more horizontal, while those on the right are more vertical, especially at the middle of this severe curve.  Also the ribs on the left are very close together, and those on the right more spaced apart.  This is because the spine on the concave side of the deformity is relatively shorter than the convex side, so the ribs are more close together.  Also as the spine curves to the side the distance of the spine, from the neck to the hips, shortens which can cause the body to look uneven, with the leg looking longer than they should be.

In Early-onset scoliosis (<10 years of age at detection) the main organ system of concern in the lungs.  The two main issues impacting the child’s lungs are the shortening of the spine (neck to pelvis) and the twisting of the spine.  In general as the spine shortens the abdominal contents (liver, spleen, stomach, intestines, etc…) relatively move upward into the chest.  Since the lungs are very compliant or soft, compared to the abdominal contents, this effectively creates less room for the lungs.  In other words the lungs become squished. 

 

3-d Computed Tomography (CT) scan of the lungs in a patient with EOS

 

 

The graph above is from a study by Emery and Mithal in 1960 which is looking at the alveoli in the young child’s lung.  The alveoli are the air sacs which permit us to get oxygen into our blood stream and get rid of carbon dioxide.  It is important that the development of the lungs is optimized early in life as the alveoli multiply in number up to approximately 8-10 years of age.  Thereafter it is mainly the alveoli mainly increase in size, not in numbers.  So it is important to maximize the growth, or length of the spine, during the first 10 years of life as this impacts how well the lungs develop.

The other organ systems (heart, gastrointestinal) are impacted to a lesser degree.  These two systems are impacted only in severe (>100 degrees) of scoliosis.  However, unlike the lungs, the impact of scoliosis on theses two systems is much more reversible.  When the scoliosis is treated these systems will return close to normal status. 

Pediatric spine deformity surgeons focus much of their attention on maximizing the development of the lungs in children unde 10 years of age.  This is why performing definitive, long spine fusions in this age group is rarely performed.  A long, multi-level spine fuison will permanently shorten the spine, and secondarily decrease the volume of the lungs.  To treat spine deformity in children <10 year pediatric spine deformity surgeons use “growth-friendly” techniques, which corrects/manages the scoliosis but permits growth of the spine.  Bracing and casting are nonsurgical techniques which are “growth-friendly” have already been posted on this blog earlier.  In subsequent blogs surgical techniques which are “growth-friendly” will be explained.