14.2.1 Behrooz Akbarnia, MD

The classification of Skaggs grouped growth-friendly procedures into those based on distraction, guided growth, or tension. In principle, the four debaters today are talking about two systems in each of the first two groups. It is worth noting that only the vertical expandable prosthetic titanium rib (VEPTR) is approved in the United States; therefore, the debate can be one of two ways—namely, growth-guided vs. distraction-based or chest vs. spine, the latter being the most challenging if nonoperative treatment fails and if surgery is needed.

As health care professionals, we must do the following:

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  Pay attention to the correction. The correction is not just about the Cobb angle; it is about a three-dimensional correction of the spine and thoracic deformity.

  
  
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  Achieve spinal growth. We must define what is meant by growth and how growth is measured.

  
  
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  Improve pulmonary function. A huge debt of gratitude is owed to Bob Campbell, MD, for his contributions in this area.

  
  
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  Ensure that any intervention is safe and minimizes complications.

  
  
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  Improve the health-related quality of life of the patient.

If we are referring to growing rods, we must define whether they are single or dual rods; the statistics and results are different, so it is important to be specific. For example, the growing rod technique has been established and is based on proximal and distal foundations. There are two rods, which may be magnetic or conventional. The principle is to distract the two parts of the spine. This is specific. Elongation and growth should also be differentiated. When elongation is performed at the beginning of treatment, this is not growth; rather, growth starts from after the course of the initial surgery and goes on until the end of treatment. Curve correction and balance should also be noted. Pulmonary function in terms of actual improvement in function or lung volume is important. Consideration must be given to the impact of the diagnosis on outcomes because etiology does matter. Complications must be compared.

14.2.2 Literature Review

In my view, most of the currently available data are based on opinion, not on evidence. We need to have evidence-based data.

One of the earliest reports on the dual growing rod technique noted that up to 5 cm of elongation and 5 cm of growth could be subsequently achieved. The yearly average growth rate was reported to be 1.2 cm, and on average, more growth was observed per year in patients younger than 5 years of age than in their older counterparts. Thompson et al ¹ looked at 28 patients and found a significant difference in the amounts of curve correction and in growth rates when single rod constructs were compared with dual rods. Another series revealed significantly better correction with dual rod constructs than with single rod constructs. A comparison of studies using the VEPTR technique and the Cobb angle as denominator noted that the maximal curve correction was 34%, which is still less than that shown with the dual rod technique.

There is a case report of a patient with Marfan syndrome who was almost 4 years of age when she started treatment. The patient continued treatment up to about the age of 13 years before definitive fusion took place, meaning that she received about 9 years of growing rod treatment. That is exactly the end point we want to see; the beginning of the correction right at the start was 50%, the curve stayed basically the same throughout the treatment period, and the patient’s growth continues to increase.

Emans et al ^{2 ,​ 3} looked at growth rates and found that average growth was 1.2 cm ± 0.9 each year following the initial VEPTR procedure, indicating a reasonably good growth.

Hasler et al ⁴ reported a 30% Cobb angle correction following the initial surgery and a 25% correction that was maintained at follow-up. A 40% complication rate was also noted, which was in line with the rate in other studies. The Philadelphia series ⁵ showed a mean Cobb angle correction of 34% and a complication rate of 33%. The correction rates when bracing and casting were used were 51% and 59%, respectively. The researchers reported that the casting group had a better correction rate than did the group that underwent VEPTR.

Does etiology matter? We looked at some of the patients in the larger groups (i.e., idiopathic, neuromuscular, congenital, syndromic). The idiopathic and congenital groups had more growth per year compared with the other larger groups, but those belonging to the congenital group had an increased loss of correction. This difference in etiology between the groups should be recognized so that we can begin to understand which group will do what. In an assessment of dual growing rods in 19 patients with congenital scoliosis, a 29% correction rate was seen and growth was almost 11 mm per year, which is relatively in line with the rate in the idiopathic group. Campbell et al ⁶ looked at the differential growth rates on the convex and concave sides of the curve and discovered that the rates were 8.3 mm and 7.9 mm per year, respectively. The growth rate was also found to be higher in children younger than 5 years of age (p < 0.033). ⁷

So, are improvements in the anatomical volume of the lungs and the functional volume and capacity of the lungs important? Bob Campbell has put this topic on the map with his description of the thoracic insufficiency syndrome, which impresses upon us the need to pay attention to the chest and thorax.

Emans et al ² studied eight patients who underwent preoperative and postoperative spirometry. They reported an increase in the forced vital capacity (FVC) and forced expiratory volume in 1 second, but this result was not statistically significant. The predicted FVC value did not significantly change between baseline and the last test, indicating that the increase was in line with growth of the lung volume rather than the actual effects of surgery.

Studies measuring the lung volume in three-dimensional reconstructions of computed tomographic (CT) scans have shown a 25 to 90% increase in lung volume based on analysis following VEPTR surgery. However, these lung volume measurements were not corrected for somatic growth. In addition, the static measurements of functional residual capacity were performed with patients in the supine position. Reports from Michigan showed that preoperative function in patients with scoliosis improved by 29%, but in data presented to the Scoliosis Research Society (SRS), ⁸ functional outcome in patients remained unchanged and no significant difference was seen between preoperative and postoperative values. In addition, no statistically significant difference was seen in complication rates or in pulmonary values, lung volumes, scoliosis angles, and SRS scores between patients in various sex, age, and disease categories.

Olson et al ⁹ performed experimental work on three different groups of animals (normal, simulated thoracic insufficiency syndrome, and simulated thoracic insufficiency syndrome with expansion thoracoplasty). The authors concluded that there was inconclusive evidence to support the concept that pulmonary hypoplasia is induced by thoracic insufficiency syndrome and controlled by expansion thoracoplasty.

With regard to lung volume and decreasing FVC rate, Redding and Mayer ¹⁰ showed that the benefits of VEPTR are stabilization of the thorax and improvement of respiratory mechanics, but they are measured in other ways.

Karol et al ¹¹ researched early thoracic fusions. They reported that if the thoracic height from T1 to T12 is less than 18 cm, the incidence of severe pulmonary restrictive disease is 63%. As the height increases from 18 to 22 cm, the incidence decreases to 25%. Therefore, there is a correlation between thoracic height and the development of pulmonary problems.

We put this to the test. There were 51 patients involved in the study. Participants were younger than 10 years of age at index surgery, had undergone more than 3 lengthening procedures, and, per the inclusion criteria, had to have complete data sets. In terms of etiology, 20 patients had neuromuscular scoliosis, 10 idiopathic, 10 syndromic, nine congenital, and two thoracogenic scoliosis. The mean preoperative T1-T12 height was 152 mm, which postoperatively increased to 175 mm and was 205 mm at the latest follow-up (p < 0.001). These patients underwent growing rod treatment. After reviewing these results, the researchers concluded that a significant increase in thoracic height could be correlated with patient age at index surgery, number of lengthening procedures, and correction of scoliosis and kyphosis, as well as with correction and maintenance of the major curve.

14.2.3 Complications

Unwanted fusions may occur with growing rods and VEPTR. Problems may also occur at anchor points. Put simply, complications are comparable between the VEPTR and growing rod techniques. In the one study of the quality of life of patients treated with the VEPTR vs. the growing rod technique, physical function, parental burden, and total score results for the two treatment options were very close.

14.2.4 Future Treatment Options

I believe the future of growing rods is headed toward MAGEC (Ellipse Technologies, Irvine, California), which is a magnetically controlled growing rod. When MAGEC is compared with other systems, such as the standard growing rod, the amount of growth seen is very similar. Maintaining distraction means stimulating growth, which cannot be done with growth-guided systems. It is hoped that this technology will have fewer complications than its predecessors.

Many of the recent developments in growing rod technology can be attributed to the dedication and time of Bob Campbell. I acknowledge the tremendous work he has done over the last 30 years to help children around the world.

The treatment of early onset scoliosis involves a careful review of several aspects of the condition. The best outcomes are achieved by addressing the issues of deformity, growth, and pulmonary function and by minimizing complications. Currently practicing spine surgeons have the option of using nonoperative treatment techniques as well as various growth-sparing systems. We must be prepared to use the best possible treatment method for each patient.

Jeremy Fairbank, MA, MD: With regard to long-term follow-up, can you clarify whether the growth potential of these children is normal? In other words, if you look at the growth rate of the limbs, is the rate normal? Sometimes, we assume that people with congenital scoliosis tend to be rather short anyhow.

Behrooz Akbarnia, MD: Yes, we must look at the whole patient. I think we must also look at each diagnosis, not merely look at the spine and the chest for lengthening; rather, we should look at the patient with cerebral palsy or Morquio syndrome and begin thinking about it as a pediatric problem.

Robert (Bob) M. Campbell, Jr., MD: There is a sequence when the specific treatment for scoliosis is determined. Basically, we start with whatever we are taught in training, and then perhaps we sometimes grope at what is currently accepted in the literature and what is set as the current standard of care. Among those options, we ought to look at the one that best addresses each individual patient’s acute and long-term disease concerns (Fig. 14.5).

Differences are now noted between adult, juvenile, and infantile curves. I was taught during residency training that fusing both was an appropriate treatment option, but this is not true. That is why a great struggle exists with regard to growth-sparing techniques. It is worth noting that all of these techniques are brutal and expensive, and they have high morbidity rates. They are not good options, but they are not quite as horrible as natural history.

With that said, the goals of treatment should be these:

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  Correcting the Cobb angle;

  
  
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  Minimizing complications;

  
  
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  Reducing costs;

  
  
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  Minimizing morbidity rates;

  
  
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  Improving operative long-term health over natural history.

As previously mentioned, spine deformity should be controlled while also allowing for growth. In some cases, this can be done with bracing or casting; however, if these options fail, then we must turn to options similar to what Dr. Akbarnia mentioned earlier. The Harrington rod was the original growing rod, which was then followed by growth guidance instrumentation and with tethering and tension techniques. Per the U.S. Food and Drug Administration (FDA), the VEPTR instrumentation is indicated for the treatment of thoracic insufficiency syndrome.

Dr. Akbarnia explained how well Harrington’s goals have been defined. John Emans has also lectured on this topic and says that for patients with chest involvement, VEPTR is better than spinal growing rods. The concept seems rather simple until you look carefully and ask what this means. For example, should the VEPTR or a growing rod technique be used for a child on oxygen with Larsen syndrome?

Both techniques are appropriate if the anteroposterior (AP) radiograph is the only thing you look at; however, if you look at the CT scan, a problem of volume is present. In this scenario, which technique is more appropriate? Which is going to straighten it out, growing rods or VEPTR? (It is worth noting that the answer is unknown with growing rods because only AP radiographs have been used to analyze the results; CT scans have not.)

Therefore, the choice depends on the goals of the health care professional. Correcting the Cobb angle and minimizing complications are fairly standard options and are supported in the medical literature. But what is the evidence for these options? Although many series have been presented, all of them are small and are made up of heterogeneous populations and different syndromes. We are now discovering that the term idiopathic probably covers many syndromic populations. VEPTR has the same problems—namely, heterogeneous populations and small clinical series. Both appear to function the same for correcting the Cobb angle and minimizing complications. It is not worth quibbling over 39% vs. 43% improvement rates for Cobb angles and then calculating Cobb angles up to three decimal points! Note that the measurement error is never mentioned; it is huge, and many of these children may be in the congenital group. For these, the measuring error is very high; among children in the idiopathic group, the error could be 5 degrees or more. Add in that figure and the statistics may become meaningless.

It is my hope that a large prospective clinical study of a homogeneous population that compares growth rods with VEPTR will be possible. Such a study would take a long time, it would be expensive, and I do not know who would pay for it, but its results might settle some of these issues. Comparing retrospective series is fine for debate, but it is not good science.

There is a lot of talk about morbidity rates between the two techniques, and basically, we have not done much better than Paul Harrington with these approaches. A two-point fixation can be seen, and there are many problems with that. A new approach, the Shilla technique, was taught to us in a way by the Luque trolley. The Shilla technique may be able to minimize costs and morbidity rates. It is only one operation, so patients are not taken back to the operating room. If you count the screws, there is also a three- or even an eight-point fixation; it is somewhat more segmental. However, additional operations may be required for complications, and there may be an unknown loss of thoracic spine growth because of the central fusion / anchor points. What is being traded off for this big central segment of spine fusion? There need to be long-term data to answer this question. The long-term complication rate is yet to be established. Everyone looks good at 5 years, but at 10 years is when we are likely to find out what has been going on.

What about growing rods vs. VEPTR, and what about self-expansion? Dr. Akbarnia mentioned that there might be less cost and lower morbidity rates. So what exactly is the long-term cost? The units will have to be replaced. Ultimately, how much are they going to cost when they come to the market for widespread distribution? There is still only a two-point fixation, and the so-called point of diminishing returns may be valid with the self-expansion as well as the manual extension devices.

Will the treatment work in the long term? In the case of devices extending extremities, many pulled out in the long term. The health care professional is likely to trade known complications for new ones when choosing the path of innovation.

Improving the patient’s operative long-term health over his or her natural history is important because this goal is what treatment should really be all about. Very few data exist about the natural history of untreated scoliosis. Data from Scandinavia reveal that mortality rates are extremely high for untreated infantile scoliosis and very high for juvenile scoliosis, but not necessarily adolescent scoliosis. With regard to the morbidity rates of natural history, there is a higher risk for respiratory failure in patients with curves greater than 110 degrees. There is also a higher risk for cor pulmonale and cardiac issues in patients with severe curves. As Dr. Akbarnia mentioned, children with scoliosis and thoracic insufficiency syndrome have a worse quality of life than those who have scoliosis without thoracic insufficiency syndrome.

The mortality rates of the operative history are unknown for growing rods and the Shilla / Luque trolley technique. For VEPTR, a higher mortality rate was seen among patients in the hypoplastic cohort.

Very little pulmonary data exist on growing rods. VEPTR has been studied, but most of its pulmonary data are based on older children because we do not yet have the ability to measure these data in younger children. However, a decreased normal but stable vital capacity has been seen among patients with scoliosis and fused ribs operated on after the age of 2 years. It has been implied that because the vital capacity gets better and improves, then that result was negative. However, the rate has just been maintained and stabilized, which is a good thing. What is lethal is when vital capacity normal percentage decreases. So, how can the “best” option simply be to stabilize it? That option may change in the future, but it currently holds true now. Pulmonary data for Shilla are currently unknown. This large hole in the data needs attention.

Cardiac morbidity rates are also unknown for all four techniques. These must be looked at systematically in the future.

Data on quality of life for the VEPTR have been submitted to the FDA; these data are what Dr. Mike Vitale has been looking at all these years. I believe that issues of quality of life tend to be dubious, subjective, and complicated, and I am unsure whether they have a real bearing on the world.

My philosophy on growth-sparing techniques is just as valid today, but it may change tomorrow. As Dr. Akbarnia previously mentioned, no data exist on them because the literature is composed mostly of opinion-based medicine. In my opinion, the safest and most logical position is to do whatever it takes to get the largest, most symmetric, most functional thorax by skeletal maturity, not to look at Cobb angles and available space for the lung.

For patients with congenital scoliosis, the VEPTR has a strong place. Dr. Emans has reviewed CT lung volumes as children grow up. Experiments on rabbits by Dr. Schneider revealed that lungs expanded with the VEPTR approach seemed to have better viscology, but these results are very complex; more issues are being uncovered than are being solved. This new model is much more lethal, and it really does make the case for extrinsic lung disease.

In terms of early scoliosis, if a patient presents with a flexible curve and correction of the concave intercostal space is achieved with bending films and at either end there is a normal growing spine, I would consider growing rods. However, if hemithoracic insufficiency syndrome is present, then I would consider VEPTR but would continue to use growing rods on occasion because the issue is still open; the technique has not been proven by any prosthetic trial. I might also choose VEPTR with the possibility of growing rods when there has been limited correction of the concave intercostal space with bending films. For example, in a neuromuscular case, the intercostal space does not open up that much with bending films, suggesting that there is an intrinsic contraction of the entire thorax that I suspect needs to be addressed; I can push on the spine, but doing so is very difficult. I would treat this patient with an Eiffel Tower construct with VEPTRs. However, it is worth noting that improvements have been made on the dynamic MR images of the lungs by doing this, and in the future, perhaps these improvements will be seen with the growing rod.

If kyphosis is present that has not been emphasized yet, either growing rods or VEPTR I or II could be considered; however, neither instrumentation has been proven to address these issues. In a patient with severe scoliosis, many of us are likely to consider a halo and then try instrumentation. Kyphosis is an unsolved issue at this time.

In the case of an 8-month-old child with a VEPTR II, I have been pushing the limits with him. Periodically, I bend up the flexible rods at the top of the VEPTR II to perform an extension moment. Will this technique work in the long term? I hope so, but I do not know yet. In 10 years I may have some decent results.

I think myelomeningocele is good for the VEPTR. The trouble with this technique is that the gibbous angle must be managed, but the chest must also be taken out of the pelvis to avoid secondary thoracic insufficiency syndrome. In my opinion, VEPTR is probably the best option because the health care professional stays out on each side and is not as centrally located as would be the case with spinal instrumentation. This is how to help these children—nurture them along until after they reach 10 years of age and then try something definitive.

In one patient with pelvic obliquity, I used growing rods. I could have just gone down with iliac bolts and attempted to treat the pelvic obliquity that started 2 years after the growing rod was put in, but instead I put in a VEPTR and straightened it out that way. We can cheat and use hybrids, so to speak.