Shilla Growth Guidance Procedure

1.      What is the Shilla procedure? The Shilla technique is one which passively guides spine growth, rather than actively distracting across like a growing rod system.  I refer to it as a "track and trolley" system.

 

2.      Who is a candidate for the Shilla technique?  Many patients who are candidates for traditional growing rods (GR) are also candidates for the Shilla technique.  The decision between GR and Shilla technique will be made between the surgeon and parents/caregivers focusing on what is best for the child. 

3.      How is it different that traditional growing rods or MAGEC?  The Shilla fixes the worst part of the deformity, that part of the spine which is growing more sideways than vertically.  By straightening out the severely curved part and then fusing the apex of the deformity the apex will be permanently improved. A traditional growing rod or MAGEC system fixates above and below the worst part of the spine deformity and creates small fusions in the part of the spine which is growing more normally.  The growing rods are then forcefully distracted to put the spine under tension.  See reference #1 below for more details.

 

4.      Is Shilla better than traditional growing rods or MAGEC?  To this surgeon, if a Shilla can be used over a traditional growing rod or MAGEC then it is my first choice.  The question is why?  The initial surgery is similar between all three surgeries in terms of recovery.  The benefit of the Shilla is there is no need for repetitive surgeries, unlike traditional growing rods, or frequent clinic visits, as is necessary for MAGEC.  Overall, when Shilla is compared to growing rods the overall outcome on x-rays is nearly identical.  Another benefit is Shilla patients undergo 1/3 the number of surgeries/anesthesia when compared to traditional growing rods.  See reference #2 below.

5.      Is the spine fused in a Shilla procedure?  A spine fusion is performed typically over 2-4 vertebra where the scoliosis is at its worst.  These vertebra were not growing normally anyways.  Even if the patient had received a traditional growing rod or MAGEC that very curved part of the spine would not grow normally.

6.      How long will the Shilla procedure last? In the 2^nd paper listed below it was demonstrated that they average patient underwent 3 surgeries: initial, one revision and then one final surgery.  The average patient underwent a revision surgery at 3-3.5 years after the first surgery and then final surgery at 6-7 years after the first surgery.  Every patient is different.

7.      When growth is completed what happens with the Shilla construct?  At or near the end of spine growth a decision is made to either convert the Shilla to a definitive spine fusion or removal all the implants with the idea to restore spine motion and not need a fusion surgery. 

8.      Whose decision is it to remove the implants or convert to a spine fusion?  It is a decision made by the patient, family and surgeon.  Most patients are undergoing definitive fusion surgery thus far because they wanted to improve their body position permanently.

9.      How many patients have had their implants removed? Thus far between our center and Little Rock there are less than 10 patients.

10.   If the implants are removed can a fusion surgery be done in the future?  Yes.

References:

1.            Luhmann SJ, McCarthy RE.  A Comparison of SHILLA™ GROWTH GUIDANCE SYSTEM and Growing Rods in the Treatment of Spinal Deformity in Children Less than 10 Years of Age.  J Pediatr Orthop 37(8):e567-e574, 2017.

2.            Luhmann SJ, Smith JC, McClung A, et al.  Radiographic outcomes of Shilla Growth Guidance System and traditional growing rods through definitive treatment.  Spine Deformity, 5:277-282, 2017.

3.            Luhmann SJ, McAughey EM, Ackerman SJ, Bumpass DB, McCarthy R: Cost analysis of a growth guidance system compared with traditional and magnetically controlled growing rods for early-onset scoliosis: a US-based integrated health care delivery system perspective. ClinicoEconomics & Outcomes Research 1:179-187, 2018.

Vertebral Body Stapling (VBS)      Part 2

1.  What is the success rate for VBS?  Two centers have reported their outcomes of VBS in patients (Washington University in St. Louis, and the Philadelphia Shriner’s).  Overall success rates for lumbar and thoracic curves are around 70%, which means the curve improved, did not change or changed less than 6 degrees.

2.  What is the success rate of bracing?  The highest level of evidence on bracing for idiopathic scoliosis is from the BRIAST study, which was a prospective study of scoliosis patients who wore a scoliosis brace and those who did not.  48% of non-braced patients did not have progression of their scoliosis and 72% of braced patients did not progress.

3.  So to conclude: the success rates for VBS and bracing appear to be equivalent.

4.  Why would a VBS be offered or performed if the results are similar to bracing?  Bracing is not an easy treatment for anyone.  VBS provides an option for those patients who cannot or will not wear a brace to control their scoliosis.  It is important to note VBS is not better than bracing, it is just a different treatment option.

5. Do the staples have to be removed in the future?  The answer is no.  The staples do not have to be removed.  The body will cover over the staple with scar tissue and the staple will gradually loosen in the vertebral body.  Due to the tines of the staple curving in the staples will not back out.

6.  What happens if the VBS does not control the scoliosis and a posterior spinal fusion is needed? Do the staples have to be removed at that time?  Again, no.  Since the staples are placed in the front of the spine they will not interfere with the instrumentation placed in the posterior (back) part of the spine.  Also the staples do not interfere with the ability to correct the scoliosis at the time of fusion.

7.  Who is a candidate for Vertebral Body Stapling?

     a.  Skeletally immature: since scoliosis mainly progresses due to growth, the use of VBS only is indicated during the growth.  There is no benefit of VBS in skeletally mature individuals

     b.   Scoliosis who Cobb measure is:

                                                    i.     </= 35 degrees in the thoracic spine

                                                   ii.     </= 40 degrees in the lumbar spine

     c.  Patients who cannot or will not wear a brace to halt the progression of scoliosis.

     d.  Diagnosis of idiopathic scoliosis or patients who have idiopathic-like scoliosis    

Who is not a candidate for VBS?

a.      Skeletally mature patients: Risser >/=3

b.      Diagnoses with poor bone quality, increased muscular tone, neurogenic scoliosis (patients with Chiari or syrinx), etc…

c.      Cobb measures >35 in the thoracic spine and >40 in the lumbar spine.

d.      Increased kyphosis of the thoracic spine >40 degrees (since the staples induce kyphosis)

e.      Those patients whose spine is excessively malrotated due to the scoliosis.  VBS will not significantly change this for the better.

Vertebral Body Stapling (VBS)      Part 1

1. What is Vertebral Body Stapling?  How is it different from Vertebral Body Tethers?  In a previous blog the surgical technique of Vertebral Body Tethering was presented.  This technique places a compressive force over the convex side of the spine (slowing down growth), to permit the concave side of the spine to relatively grow more and create a straighter spine.  Prior to the introduction of the Vertebral Body Tether, which uses screws placed into the vertebral body, modulating growth of the concave and convex side of the spine was accomplished with staples.  These staples were also placed anteriorly, but instead of being placed in the middle of the vertebral body they were placed across the disc spaces between each vertebral body. 

   
   

   
   

   
   

1. Is VBS a new procedure? This surgical technique was first reported in the 1950s but, due to the lack of an adequate implant, the technique did not work as designed.  It wasn’t until the 2000s that an appropriate implant was identified, and this technique began to show promise.  The staples used at that time, and currently, are made of Nitinol which is a memory-shape alloy.  When the staples are placed in an ice bath, the tines of the staples can be straightened.  After placement across the disc space the staple warms up to body temperature and the tines curve back inward.
2. What is the purpose of VBS?  To halt or improve scoliosis in the skeletally immature patient.
3. What research has been done on VBS?  There have been animal studies and clinical studies over the last 15 years.
4. Are there any potential complications of VBS? As with any surgical procedure there can be complications related to the surgical procedure or the patient’s underlying medical condition.  The potential complications includes, but is not limited to:
   1. Anesthetic (anaphylaxis, airway, etc…)
   2. Pneumothorax
   3. Excessive bleeding
   4. For thoracic stapling: Injury to the lung, heart, great vessels, thoracic duct, etc…
   5. For lumbar stapling: injury to the great vessels, ureter, psoas dysfunction, etc…
   6. Painful postoperative surgical scar
   7. Staple dislodgement
   8. Staple breakage
   9. Failure to control the scoliosis
   10. Need for definitive spinal fusion

Vertebral Body Tethering (Part 5 and the last one on this topic)

In earlier posts VBT has been extensively detailed.  One question that commonly is asked during discussion of VBT with patients and caregivers is: “What are the long-term issues with VBT?”

The simplistic answer is: “We don’t know”.

One layer to this question is what happens to the actual tether? 

1. If we look at other implant systems used in the spine and other bones of the body over the last 50+ years we can roughly sketch out some possible scenarios for the system currently used for VBT.  The fixation in the vertebra are screws which, as a group, have a long history of safety and efficacy.  However the screw used in VBT are designed for use in the posterior spine, and for VBT they are placed anterior through a minimally-invasive or thoracoscopic approach.  The question is will they function with the same efficacy and safety profile.  Based on the collective experience it appears the screws have good purchase and few issues with prominence, migration or pullout. 
2. The other aspect of VBT is the tether which is made of braided polypropylene.  This is the workhorse of the system, which compresses across the convex discs and growth plates to modulate spine growth.  Since there is no fusion across the vertebral bodies there will be constant motion on the tether.  Like any non-regenerating material which is constantly moving, the tether is subject to fatigue, which can lead to failure or breakage of the tether.  It makes sense that the tether will eventually break, considering it is implanted in adolescents and will be stressed for over 60+ years (or more!).  Over the last year there have been reports of segmental failure of the tether (between two screws), so it is reasonable to assume that in the long-term the tether will likely break in multiple locations.  For the sake of the aim of VBT to modulate growth in the immature spine, we only need it to last until the completion of spinal growth.  What is not desired is for the tether to break prior to this time and permit the spine deformity to get worse.

A second layer is what the tether does to the vertebral bodies, and more importantly, to the disc between the vertebral bodies.  The implications of long-term compression of the instrumented disc and the presence of anterior instrumentation in a non-fusion technique is unknown.  Changes to the intervertebral discs may occur and, if this happens, may cause axial thoracic back pain or possible disc herniations in the future.  Also, it is unknown if increased motion, such as after the tether breaks, through a previously VBT-compressed motion segment is significant.  Will this cause back pain? At the present time we just don’t know.

More research is necessary on VBT safety, timing of VBT placement, VBT tensioning, intervertebral disc health, and long-term patient reported and radiographic outcomes of VBT.

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References:

Website: www.zimmer.com/medical-professionals/products/spine/dynesys-dynamic-stabilization-system.html

Newton PO, Fricka KB, Lee SS, et al.  Asymmetrical flexible tethering of spine growth in an immature bovine model.  Spine 2002;27(7):689-93.

Braun JT, Ogilvie JW, Akyuz E, et al.  Fusionless scoliosis correction using a shape memory alloy staple in the anterior thoracic spine of the immature goat.  Spine 2004;29(18):1980-9.

Newton PO, Farnsworth CL, Faro FD, et al.  Spinal growth modulation with an anterolateral flexible tether in an immature bovine model: disc health and motion preservation.  Spine 2008;33(7):724-33.

Chay E, Patel A, Ungar B, et al.  Impact of unilateral corrective tethering on the histology of the growth plate in an established porcine model for thoracic scoliosis.  Spine 2012;37(15):E883-9.

Crawford CH 3^rd, Lenke LG.  Growth modulation by means of anterior tethering resulting in progressive correction of juvenile idiopathic scoliosis: a case report.  J Bone Joint Surg [Am] 2010;92(1):202-9.

Samdani AF, Ames RJ, Kimball JS, et al.  Anterior vertebral body tethering for immature adolescent idiopathic scoliosis: one-year results on the first 32 patients.  Eur Spin J 2015;24:1533-9.

The World Pediatric Projects winter fundraiser called "Treasures in Paradise" happened last week, Friday January 26th,

The keynote speaker was Erickson Hernandez, a wonderful young man who Drs. Manke and Goldfarb, and myself treated at our Shriner's Hospital.

Check out the web address (copy and paste in your browser) below for a video of Erickson's speech.


https://vimeo.com/lpcreativestudio/review/252613501/753298fe30

Vertebral Body Tethering (Part 4)

Primum non nocere or “do no harm” is a basic tenet of medicine.  This is why for surgical procedures, such as Vertebral Body Tethering or VBT, safety is the pre-eminent concern, even more so than its efficacy or how well it works.  If a surgical procedure is safe (infrequent, minor complications, with no significant long-term problems) but only demonstrates mild to moderate efficacy then it may be viewed as a reasonable treatment.  However if the procedure cannot be demonstrated to have reasonable safety it is unlikely any level of efficacy will be able to make this a reasonable treatment.  This is especially the case for diseases which are not life-threatening, such as scoliosis. 

As patients and caregiver potentially contemplate if VBT as a possible treatment (as detailed in an earlier post) it is important that the potential complications or adverse outcomes are detailed and well-understood as to their likelihood, severity and long-term implications.  The list of complications which may occur with VBT are:

Anesthetic problem (such as allergic reaction or airway problem)

Injury to the great vessels, heart, lungs

Uncontrolled bleeding

Neurologic deficit

Postoperative pneumothorax

Surgical site infection

Screw pullout or symptomatic migration

Tether breakage

Failure of VBT modulate growth

Over-correction of spinal deformity

Pleural scarring secondary to surgical approach and presence of screw heads/tether in chest

Irritation of the diaphragm or psoas due to screws

Back or chest pain

In the next blog post the long-term issues of VBT will be presented.

Vertebral Body Tethering for Scoliosis (Part 3)

In Medicine, and in particular the area of spine deformity, the development of new treatments and technologies which can demonstrate improved outcomes, lower frequencies of complications, and/or faster recovery can create a “buzz” and enthusiasm depending on its potential of improvement.  Physicians typically see these innovations earlier than the general public at medical meetings and read about them in peer-reviewed medical journals.  Slightly later the medical media, followed by mainstream media, begin to report on the new medical technologies, especially if these treatments have developed some traction amongst physicians.  One such technology is Vertebral Body Tethering (VBT) for scoliosis in the growing spine. 

As detailed in previous postings on this blog there is significant potential for this technology, but little scientific evidence of its efficacy in humans.  At present there are no approved implant systems in the U.S. which are FDA-approved for scoliosis. Spine implants used for VBT are being used in an off-label or unlabeled manner in the U.S.  It is important to understand that innovations, especially in area of surgical spine deformity treatment, advances typically occur faster than does FDA approval.  So innovations without FDA approval does not categorically mean they are unsafe or do not work, rather there is an absence of sufficient high-level of medical evidence to prove these devices are safe and efficacious to the FDA, who demands very high level of scientific proof.  Prior to FDA approval implant systems, such as VBT, exist in a “grey” area.  This can be frustrating to patients and caregivers who are anxious for advances in medicine, yet there is scant medical literature to help them navigate treatment options. 

In the next blog post the complications of VBT will be presented.