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.

Top Eleven Podium Presentations at the 2017 ICEOS Meeting Which Will Impact the Care of EOS Patients in My Practice

1.       Paper #1

a.       Bouton D, Karol L, Poppino K, Johnson C.  Continued deterioration in pulmonary function at a minimum 18-year follow-up from early thoracic fusion in non-neuromuscular patients.

b.      Conclusion: Patients with thoracic spinal fusion at a very young age (mean 2.7 years) have a continued decline in pulmonary function (38% of normal) as they enter adulthood, which can be life-threatening.  Additionally, their functional capacity (6-minute walk test) is severely limited to 62% vs. age-matched controls.

c.       Take-away message: Avoid thoracic spine fusions in children less than 5 years of age.

2.       Paper #3

a.       Celebiolglu E, Yataganbaba A, Asli O, Degirmenci C, Kocyigit IA, Tekin R, Demirkiran HG, Yalcin EE, Demir AU, Yazici M.  Can TGR change the natural history of pulmonary function in EOS?  Is radiological straightness correlated with normal lung development?

b.      Conclusion: Traditional Growing Rods can help Early Onset Scoliosis patients who would otherwise have serious pulmonary insufficiency and help achieve pulmonary capacities compatible with a healthy life.  Despite significant decreases in Traditional Growing Rod graduates in oxygen consumption capacity and pulmonary test compared to healthy controls, results were not statistically different than Adolescent Idiopathic Scoliosis.

c.       Take-away message: Traditional Growing Rods are effective and successful in achieving good results in pulmonary functions as well as radiological parameters.

3.       Paper #5

a.       Kawakami N, Matsumoto H, Saito T, Tauchi R, Ohara T, Redding G.  Pre-operative Six Minute Walk Performance in Children with Congenital Scoliosis.

b.      Conclusion: The 6 minute walk test is a feasible measure of function and is substantially reduced prior to surgery in most children with congenital scoliosis.  The 6 minute walk  test correlates with age and inversely with Cobb angle, but not FVC%. 

c.       Take-away message: The 6 minute walk test measured serially in meters and not as a % of normal is a useful measure of functional status in children with congenital scoliosis.

4.       Paper #25

a.       Ahmad A, Subramanian T, Panteliadis P, Wilson-Macdonald J, Rothenfluh D, Nnadi C.  Quantifying the “Law of Diminishing Returns” in Magnetically Controlled Growing Rods.

b.      Conclusion: The “Law of Diminishing Returns” can also be observed following serial distraction in Magnetically Controlled Growing Rods.  In comparison to previously published data for Traditional Growing Rods, there is a gradual linear decline as opposed to a rapid initial decline in lengthening.

c.       Take-away message: Magnetically Controlled Growing Rods gradually appear to stiffen the spine in a similar way as Traditional Growing Rods.

5.       Paper #26

a.       Poon S, Spencer HT, Sever R, Cho R.  Maximal Force Generated by Magnetically Controlled Growing Rods Decreases with Rod Lengthening.

b.      Conclusion:  There is a small (3.6 lb.) statistically significant decrease in the maximal force generated by MCGR as the rods are lengthened.  This decrease may contribute to diminished spine length gained with each subsequent MCGR lengthening.

c.       Take-away message: Magnetically Controlled Growing Rods are able to maintain >92% of distraction force near the end (83%) of the actuator length.

6.       Paper #29

a.       ElBromboly Y, Johnston C, McClung A, Samdani A, Glotzbecker M, St. Hilaire T, Hurry J, Kedar P, Flynn T, El-Hawary R.  Does the Type of Proximal Anchor Used During Distraction-Based Surgeries for Patients with Non-Idiopathic EOS Affect Spine Length?

b.      Conclusion:  At a minimum 5 year follow-up, distraction-based surgeries increased spine length for patients for non-idiopathic EOS; regardless of proximal anchor choice.  Rib-based anchors may protect against potential law of diminishing returns.

c.       Take-away message: Rib-based proximal anchors in growing rods appear to achieve equivalent correction as spine-based anchors in non-idiopathic patients.

7.       Paper #38

a.       Luhmann SJ, McAughey E, Ackerman S, Bumpass D, McCarthy R.  Cost analysis of growth guidance system compared with magnetically controlled and traditional growing rods for early-onset scoliosis in the US: an integrated health care delivery system perspective.

b.      Conclusion: Growth Guidance Systems resulted in fewer invasive surgeries (3.4 vs. 14.4) and deep Surgical Site Infections than Traditional Growing Rods with lower cumulative costs per patient than both Magnetically Controlled Growing Rods ($29,916 less) and Traditional Growing Rods ($25,226 less) over a 6-year episode of care. 

c.       Take-away message: Growth Guidance Systems result in fewer infections, less surgery and are 16-18% cheaper than Magnetically Controlled Growing Rods or Traditional Growing Rods of the entire episode of care.

8.       Paper #40

a.       Bauer J, Yogova P, Neiss G, Rogers KJ, Sturm PF, Sponseller P, Luhmann SJ, Pawelek J, Shah SA.  Is There an Improvement in Quality of Life with Early Onset Scoliosis Managed with Traditional Growing Rods Converted to Magnetically Controlled Growing Rods.

b.      Conclusion: Although patient families and their surgeons may subjectively report improved Quality of Life after conversion from frequent surgical Traditional Growing Rods lengthenings to in-office Magnetically Controlled Growing Rod lengthenings, these improvement were not evident in Quality of Life surveys.

c.       Take-away message: In patients converted to Magnetically Controlled Growing Rods the benefits are obvious to caregivers and surgeons, but the outcome measures are not sensitive enough to pick up a difference.

9.       Paper #41

a.       Skaggs D, Akbarnia B, Pawelek J, Matsumoto H, St. Hilaire T, Sturm PF, Perez-Grueso FJS, Luhmann SJ, Sponseller P, Smith J, White K, Vitale M.  Two Year HRQOL Measures are Similar Between Magnetically-Controlled Growing Rod (MCGR) Patients and Traditional Growing Rod Patients.

b.      Conclusion: Prior to surgery MCGR patients has lower HRQOL in 3 out of 10 domains (Daily Living, Physical Function, Transfers), however at 24 months both groups were similar across all domains.  Subgrouping of neuromuscular patients revealed differences in financial and parental impact domains which suggest etiology plays a role in the Health-Related Quality of Life in these patients.

c.       Take-away message: There may be a benefit to Magnetically Controlled Growing Rods in Daily Living and Physical Function when compared to Traditional Growing Rods.  More study is needed.

10.   Paper #42

a.       Gomez JA, Kubat O, Hurry J, Soroceanu A, Flynn T, Tovar M, Hanstein R, Lafage V, Schwab F, Smith J, Skaggs, El-Hawary R.  Spinopelvic alignment affect Health-related Quality of Life (HRQoL) for Patients with Early Onset Scoliosis.

b.      Conclusion: For children with early onset scoliosis, preop Pelvic Incidence >60 degrees (poor Pain outcomes), pre and post-op Lumbar Lordosis>60 degrees (poor Satisfaction outcomes), postop Pelvic Incidence-Lumbar Lordosis mismatch >20 degrees (poor Fatigue outcomes) and post-op Proximal Junctional Kyphosis (poor Fatigue outcomes) all decrease Health-Related Quality of Life.

c.       Take-away message: Achieving good spinopelvic alignment is important in Early-Onset Scoliosis treated surgically.

11.   Paper #45

a.       Matsumoto H, Campbell M, Minkara A, Roye DP, Garg S, Johnston C, Samdani A, Smith J, Sponseller P, Sturm PF, Vitale M.  Development of a Risk Severity Score (RSS) Predicting Surgica Site Infection in Early Onset Scoliosis: Identifying High-Risk Patients.

b.      Conclusion: The Risk Severity Score (neuromuscular diagnosis and endocrine, gastrointestinal, pulmonary comorbidities, etc…) provides empirically-derived patient-specific Surgical Site Infection risks.  It can be used to prepare for high-risk patients for surgery, as a factor in clinical decision-making, and to facilitate comparison between hospital outcomes. 

c.       Take-away message: The risk of a postoperative surgical wound infection can be tabulated for preoperative optimization and in discussions with caregivers preoperatively.

The Growing Spine Study Group 

Vertebral Body Tethering Part 2

Vertebral Body Tethering for Scoliosis

As mentioned in the last blog there is a paucity of information/evidence on the use of VBT in skeletally-immature patients with scoliosis.  Animal studies have demonstrated VBTs can modulate spinal growth with few changes to the intervertebral disc or growth plates.  Early, short-term, single institution series have been encouraging with few reported serious complications.  More research is necessary on VBT safety, timing of VBT placement, VBT tensioning, intervertebral disc health, long-term patient reported and radiographic outcomes of VBT.

Current indications for VBT

1     1. Skeletally immature patient (Risser 0-3, Sander digital hand score <5).  Optimal timing of VBT surgery is necessary to produce a satisfactory spinal alignment at the completion of spinal growth.  At present there is insufficient information available to accurately predict when to place a VBT.

2     2.  Deformity location: main thoracic

3     3. Idiopathic diagnosis

4     4. Coronal deformity: main thoracic (30-70 degrees), thoracolumbar/lumbar (30-60 degrees)

5     5. Flexibility on side-bending radiographs to less than 30 degrees.

6     6. Less than 20 degrees of axial rotation. 

7     7. Less than 40 degrees of kyphosis

Surgical Technique: VBT for Scoliosis

VBT is a thoracoscopic, minimally-invasive technique in which screws are placed into the vertebral bodies on the convex side of the coronal deformity.  The screws are placed into the middle of the vertebral body with bicortical purchase under fluoroscopic guidance.  A high-strength, braided polypropylene tether is then placed into the screw heads and then sequentially secured to each screw after segmental compression.  The technique achieves modest correction of the spinal deformity immediately postoperative.