Blog Topic: Recent Publication on Magnetically-Controlled Growing Rods

12-31-2022

 Blog Topic: Growing Rod Constructs for Patients with Neuromuscular Scoliosis

12-31-2022

This talk was presented at the International Pediatric Orthopaedic Symposium in Orlando, Florida last November 2022.  My topic was to talk on patients with neuromuscular scoliosis (NMS) who were less than 8 years of age, presenting the argument to do Growing Rod (GR) surgeries, instead of performing a Posterior Spinal Fusion (PSF). My opponent was Dr. Nick Fletcher from Children’s Healthcare of Atlanta, who provided a nice counter-argument presentation for PSF in this patient population. 

My side of the debate was an easy one for me to support, specifically to support GR surgeries.  I will present the slides of the talk and give some additional information.

 

 

The diagnosis of NMS lumps together a wide variety of neuromuscular diagnoses, from cerebral palsy to spina bifida to spinal muscle atrophy, just to name just a few.  With these different neuromuscular diseases come a wider variety of medical comorbidities, such as cardiac (heart), pulmonary (lung), and endocrine issues which can impact surgery and the recovery from surgery.  When compared to idiopathic, syndromic, and congenital scoliosis patients, neuromuscular patients are by far the most challenging group of patients. 

In NMS the impact on the child can be broken down into two broad groups, orthopaedic and medical.  One main musculoskeletal problem we see in NMS is difficulty in sitting, which can be called “imbalance”, because the pelvis is tipped.  When the patient tries to get their bottom onto the seat of their wheelchair they lean severely to the left or the right.

The other main problem we see in NMS is back pain when patients are sitting. The bigger the scoliosis, and the more the pelvis is tipped the higher, the chance of having pain when sitting.  This can be a significant problem preventing the children to sit in a car seat, be upright in school and/or be unable to travel any significant distances.

The last bullet point on this slide is about T1-S1 distance, which is a quantitative measurement of the distance from the shoulders to the pelvis.  The longer this distance is, the greater potential lung volume will be.  However, we don’t often know how much distance a single child will need to have no pulmonary problems (pneumonias, shortness of breath, etc…) in adolescence and adulthood.  Also, we don’t know the growth potential for any one child.  What we do know is that, in general, children with neuromuscular disease do not grow as much as the family history (height of parents and siblings) may predict. 

So if a child has NMS, and is less than or under 8 years of age and needs surgery, how do we know if a child should undergo GR or PSF surgery? We know the data to support either surgery, over the other, is poor.  The main reason is we don’t know how much T1-S1 distance a child needs at the end of growth or how much potential T1-S1 growth any child may have….. so we need to have discussions, between the surgeon and family/caregivers about the two options, and their benefits, risks, and potential complications.  As indicated on the slide, we need to discuss:

1.      Number of procedures a family/caregiver is willing to have the child undergo.

2.      The tolerance of complications, such as implant breakage, implant pull-out and infection.

3.      The ability of the family/caregivers to be able to deal with complications and need for hospitalizations and procedures, sometimes with short notice.

4.      The amount of T1-S1 distance a patient may need

5.      The patient’s pulmonary (lung) status, such as need for supplemental oxygen, tracheostomy or use of a ventilator to breath.

For each child/family/caregiver there is a unique situation for each item #1-#5….and varying degrees.  These discussions can take many months or years to come to a decision.  Each child and decision is unique.

This slide presents a published study from the Pediatric Spine Study Group on the use of GR in NMS.  81% of patients achieved a T1-S1 distance of 18 cm, which is the minimum distance currently believed to be sufficient for asymptomatic pulmonary function though there is scant data to support this position. 

Not every scoliosis needs surgery right away. Here is a 9 year old girl with CP.  In the first picture on the left there is severe scoliosis of 81 degrees and pelvic obliquity (tipped pelvis) of 28 degrees (away from being level).  Move to the third picture from the left and you see there is kyphosis of 76 degrees (high end of the normal range is 50 degrees).  So this young lady has a severe kypho-scoliosis, a combination of both deformities.  This magnitude of deformity typically ends up getting surgery, however see the 2^nd from the left and the 4^th from the left pictures and you see how flexible she is!  The scoliosis goes down to 45 degrees and the kyphosis down to 28 degrees!  Based on this information we can treat nonsurgically with bracing and wheelchair modifications.  Eventually she will need PSF surgery but it will be just one surgery….and not several!

The goals for surgery mirror the topics which should be part of preoperative discussions:

1.      Improve pelvic obliquity

2.      Improve scoliosis and/or kyphosis

3.      Increase T1-S1 distance

4.      No complications. It is important to point out GR constructs will have more complications than PSF due to the nature of the GR constructs (stiff metal, relatively flexible spine) and the need to convert these patients to a final, definitive at or near the end of skeletal growth.

5.      Durable; minimal reoperations. To this point, traditional growing rods (TGRs) will need more surgeries than magnetically-controlled growing rods (MCGRs).  This is because the MCGRs can be lengthened in the office without sedation, while TGRs need to be lengthened in the OR under general anesthesia (about every 6 months).  Hence we try very hard to place MCGR, but sometimes patients size and deformity prevents us from placing them, and we have to place TGRs.

The correction forces of GRs is demonstrated on this slide. A car jack, which lifts a car off the ground, has two points it is distracting against, the ground and the car.  In GRs we need to establish two point to distract against, and these need to be over the area of the spine deformity in order to correct the deformity.  So there are two foundations which need to be created:

1.      Cranial (Upper)

2.      Caudal (Lower)

Cranial fixation points can be ribs or the spine.

Caudal fixation points can be spine, iliac crest or the sacrum-pelvis

 

Cranial or upper fixation point option are the ribs, and there are many of them on each side of the chest.  After using them for many years, it appears these are likely a better option than the spine in children under 7 years of age. When these are used 3-4 ribs should be used for each rod, to minimize the occurrence of the rib hooks pulling through the ribs.

 

This slide demonstrates two points of interest: the use of spine fixation (pedicle screws) cranially and the use of only one rod.

#1: The use of spine fixation appears more successful in patients over 7-9 years of age, versus patients over 9 years of age. In the older patients, the grip strength of the screws is more reliable, due to the ability to maintain bony fixation.  If the fixation is UNBALANCED (upper vs. lower) then the end with weaker fixation is more likely to fail.  This is important when the caudal (below) fixation is in the iliac crests or sacropelvis, as this is a very strong fixation method. Therefore, in this case the BALANCED fixation is sacropelvic fixation caudally, and 6 pedicle screws used at the cranial side creating BALANCED fixation.

If the lower foundation is to the spine, then the cranial fixation with 4 screws may be sufficient.  By fixating short of the pelvis, a lot of the normal body/trunk motion is dissipated by the lumbar spine below the spine fixation.

#2: The use of two rods is stronger than using one rod.  However, the use of one rod is occasionally necessary because the spinal deformity may prevent safe placement of two rods.  A child with low body mass, and hence low muscle mass may not allow a rod on the convex side.  The other situation is in the spinal deformity with significant kyphosis, called kyphoscoliosis, which can preclude a rod on the convex side, especially a magnetically-controlled growing rod.

The caudal foundation options are presented here.  If the fixation can stop short of the pelvis, onto the spine, this is preferred.  The risk of a surgical site infection is lower if pelvic fixation can be avoided.

If fixation needs to go to the pelvis, such as the pelvis is very tipped at an angle, then all methods of fixation are reasonable to use. 

Here are the three main types of pelvic fixation

The left picture shows the use of a Dunn-McCarthy or “S” hook.  This device rests on the top of the iliac crest and was popularized by Dr. Robert Campbell with the VEPTR device.

The middle picture is another method of iliac crest fixation called pelvic saddles.

The right picture is sacropelvic fixation using pedicle screw at bilateral L5 and bilateral S1 and bilateral iliac screws.  This is a very strong, rigid method of fixation.

The choice of fixation method depends on multiple factors, such as patient age, diagnosis, deformity type, and surgeon training and experience.

As mentioned two rods are stronger than one, so we typically try to put in two rods.

Another obvious statement is to use bigger rods (5.5 mm vs. 4.5 mm) as they have a lower fracture rate.

What type of rods should be used? In general, the use of magnetically-controlled growing rods is preferred as this minimizes the number of surgical procedures.  However, the use of traditional growing rods may be necessary due to the patient size and type of spinal deformity.

In conclusion, it is important to have shared decision-making.  Ideally, the decision of growing rods vs. posterior spinal fusion is one, which usually occurs over multiple office visits.  Both approaches are reasonable and the complications, potential outcomes and need for future surgical procedures are the main drivers of the decision.

 Blog Topic: Talking Points about Thoracic Vertebral Body Tethering vs. ApiFix

Vertebral Body Tethering (VBT) and the ApiFix device are procedures which have garnered a lot of attention from surgeons, patients and families.  Below is a list of talking points which should be known about VBT and ApiFix so there can be informative, educated, transparent discussions about VBT and ApiFix, when compared to the other commonly-performed procedure Posterior Spinal Fusions.  Discussions on these points is necessary before VBT or ApiFix surgery between the surgeon and patients/families to be fully-informed.

Talking Points to discuss with your surgeon:

 

Blog Topic: Use of Magnetically-Controlled (MAGEC) Growing Rods in Neuromuscular Scoliosis

11-6-2022

 

In past blog posts we have presented Magnetically-Controlled (MAGEC) Growing Rods.

1)     There was the three-part series on the following dates:

3-9-2017          MAGEC: Part 1

5-3-2017          MAGEC: Part 2

5-18-2017        MAGEC: Part 3

 

2)     On 11-28-2021 a study on the use of MAGEC vs. Posterior Spinal Fusion vs. Vertebral Body Tethering in 8-11 year old patients was presented

 

3)     On 8-23-2022 we presented a comparison of the Shilla Growth Guidance system vs. the MAGEC Growing Rods.  This blog post was a compilation of talking points for discussions with surgeons when these constructs are options for treatment.

 

In this blog post we will demonstrate the use of MAGEC Growing Rods in a patient with neuromuscular scoliosis due to spastic quadriplegic cerebral palsy

 

This first figure shows an 8 year old boy with spastic quadriplegic cerebral palsy (CP).  He uses a stander and gait trainer, and has pain in his back when sitting. There is a 92 degree scoliosis (left picture) and 94 degree kyphosis (right picture).  It is common at this magnitude of deformity that back pain occurs when sitting, which is very problematic if they cannot stand and must use a wheelchair for all activities.  These children may not be able to attend school or take car ride due to back pain.

 

 

When the patient lays down the scoliosis improves from 92 to 65 degrees and the kyphosis from 94 to 29 degrees, which is VERY flexible for a patient with CP.

 

 

 

 

As you see below the 92 degree scoliosis and 94 degree kyphosis both improve to 44 degrees by placement of magnetically-controlled growing rods (MCGRs) from T2 down to L5.  Stopping the growing rod short of the pelvis is possible since the hips are level, which decreases the infection risk and preserves some motion of the low back.

 

 

 

The below slide is 4 years and 3 months after surgery. The MCGRs have been lengthened 8 times in the office over that time period. No surgeries have been done over those 4 years, 3 months.  The two yellow arrows point to the area on each growing rod that has been lengthened.

 

 

 

The last slide shows how the spine deformity has improved…..with the MCGRs.  Treatment is ongoing…..

 

 

Blog Topic: Posterior Spinal Fusion for Thoracic Scheuermann’s Kyphosis

10-28-2022

 

Two blog posts ago the topic of thoracic Scheuermann’s Kyphosis (SK) was presented, stopping short of discussing the surgical treatment.  In this post we will show a patient who underwent correction of his SK using posterior column osteotomies (see blog post from 9-6-2020) and posterior spinal fusion (see blog post from 1-16-2022).

 

The two main reasons patients choose to undergo surgical correction are:

 - Back pain. Surgery can be an option when the back pain has not responded to nonsurgical treatments and is severe enough that the patient is unsatisfied with their quality of life.

- Aesthetics/Appearance of the body. SK causes changes in the body, which are viewed as unappealing, such as slouching, having a “poochy” belly and small chest/breasts, and tendency to look down at the ground with difficulty in looking straight ahead.  Patients can have a very negative opinion of their body, and this can negatively impact their self-image and social interactions. We cannot underestimate, or minimize, the impact of SK on the patients, specifically on their mental health.  Body dysmorphia is real issue in SK.

 

What is our goal of surgery (posterior spinal fusion)?

We aim to correct the kyphosis to be in, or very close, to the normal range of thoracic kyphosis.  Not all kyphosis deformities should be corrected into the normal range (<50 degrees) since this can increase the risk of having a complication during or after surgery. 

 

What are the overall risks of surgery? In spine deformity surgery, there are two layers of risk:

- Risks possible with any surgery on the human body

- Risks unique to spine deformity surgery

 

What are the “risks possible with any surgery on the human body”?

- General anesthesia.  This means patients are completely asleep under anesthesia and are intubated having a ventilator breathe for them.

- Surgical Site Infections (SSIs). Surgery is done through incisions on the skin. Even in minimally-invasive surgery, skin incisions have to be made to access areas of the body.  This introduces the risk of SSIs, most commonly a bacterial infection, such as Staphylococcus aureus. This risk is minimized by the surgical team and O.R. in many ways, such as using intraoperative antibiotics and diligent sterile technique. 

- Worsening of pre-existing medical conditions. Heart disease, lung disease, neurologic diseases can all increase the risk of a complication related to surgery.

 

What are the “risks unique to spine deformity surgery”?

- Spinal Cord Function. In spine deformity, surgery the focus of attention is mainly on the spinal column, or the bone of the spine.  Inside the spinal column are the spinal cord and nerve roots, and around the spinal column are blood vessels and other organ systems.  Most spinal deformity surgeries never encounter the major blood vessels or other organ systems, so we are more concerned with the spinal cord and nerve roots.  For surgery of the thoracic and lumbar spine, the spinal cord and nerve give muscle function and sensation in the legs and control the bowel and bladder.  It is desirable the spinal cord and nerve roots work the same after surgery as they do before surgery. However, during surgery the patients are under general anesthesia so they cannot tell us if there is a problem with spinal cord function, and cannot actively move the legs.  During surgery, the spinal cord function is assessed by an intraoperative neuromonitoring specialist, which evaluate the electrical signals of the spinal cord.  This method of spinal cord testing is 99.8% accurate in determining final neurologic outcome from surgery. 

- Early Movement/Migration/Pull-out of Spinal Fixation.

- Failure of Spinal (Bone) Fusion.

- Need for Reoperation.

- Adjacent Segment Angulation/Breakdown.

- Back and Leg Pain.

*** Please note the risks of surgery just listed are some of the most common, which may occur.  This list is not exhaustive nor inclusive of all potential complications.  A discussion about complications is important to have before surgery.

 

So let us go to the surgical case…….

 

The case is an 18-year-old male with SK. His pain is mainly over the area of his back where the red arrow is pointing.

 

The left side radiograph is the patient standing upright. On the right is him lying on his back with a bump under the area of kyphosis, which makes him extend his back.  This gives us information about his spinal flexibility and how difficult it will be to correct his deformity. In general, a more flexible spine makes the surgery easier, faster and safer.

 

Here is the patient now 1 year after surgery.  His thoracic kyphosis is 56 degrees, which is just above the normal range.  However, his overall appearance and spinal balance is excellent and he has no back pain.

 

Here he is now 2 years after surgery

 

In 2022 the three most common metals used for spinal rods in spine deformity surgery are cobalt chrome, titanium (pure and alloy) and stainless steel. For SK surgeries, we need to use very stiff spinal rods, such as a 6.0 mm Cobalt Chrome or 6.35 mm Stainless Steel.  Smaller, more flexible rods will not allow us to achieve a new spine position and will not maintain the new spine position as the spine fusion develops.

 

 

 

 

 

 

 

 

Blog Topic: Published study in Journal of Bone and Joint Surgery: Trunk Motion of Vertebral Body Tethering vs. Posterior Spinal Fusion

10-17-2022

 

 

This was a study of trunk (back) motion from the Philadelphia Shriners hospital by a previous spine fellow from Washington University, Dr. Joshua Pahys.  This elegant study used a motion analysis lab to quantify back motion between two groups of patients: 1) 65 patients having undergone Vertebral Body Tethering (VBT), and 2) 47 patients who had a Posterior Spinal Fusion for idiopathic scoliosis.

They evaluated thoracic and lumbar flexion, extension, sidebending and rotation.

 

 

PSF had significant loss of motion in all 4 directions at 2 years postoperative. 

Flexion loss at L1 11 degrees

Flexion loss at L4 30 degrees

For each level of the fusion down from L1 there was a 7 degree decrease in flexion motion

 

VBT had significant loss of flexion and sidebending at 2 years postoperative.

               Flexion loss at L1 11 degrees

               Flexion loss at L4 17 degrees

 

Take away message from this study about trunk motion after PSF and VBT:

1.      No clinical difference in trunk motion when PSF vs. VBT are instrumented to </= L1.  This means there is not a compelling argument about using VBT to preserve back motion if the surgeries end at T11, T12 or L1.  In fact, a PSF is probably a better choice since the spine can be actively derotated to decrease the rib prominence, much better than a VBT procedure. When surgery goes down to L2, L3 or L4 VBT does preserve more motion

2.      VBT did decrease in flexion and sidebending vs. preop.  This means only back extension and rotation were preserved and there was no significant impact by performing VBT surgery

3.      SRS scores are similar at 2 years postop.  Patients did well in both groups and there was no perceptible difference in pain, appearance, or function.

 

Blog Topic: Thoracic Scheuermann’s Kyphosis

10-16-2022

 

What is thoracic kyphosis? From the side the human spine is wavy, unlike the view from the front in which it should be straight. The only part of the spine with kyphosis is the thoracic spine, the cervical and lumbar spine are in lordosis.

 

 

How much thoracic kyphosis is normal? In general normal kyphosis is in the 20-50 degree range. A higher degree of kyphosis is called hyper-kyphosis

 

 

What are the different types of hyper-kyphosis? There are broad, and sometimes overlapping, sub-groups in hyper-kyphosis:

1.      1. Congenital: parts of the spine never developed or separated or both

2.     2.  Postural: this type of increased kyphosis is flexible, some is of thought of “slouching”.  When they lay down the kyphosis improves

3.     3. Syndromic/Neuromuscular

4.     4.   Post-traumatic: after a spine fracture

5    5. Scheuermann’s

 

What is Thoracic Scheuermann’s Kyphosis?

Angular wedging >5 degrees per level over 3 consecutive levels, called Sorensen’s criteria.  Instead of the vertebra being the normal rectangular shape, they become trapezoidal, shorter in the front than in the back. 

 

 

Over the area of Scheuermann’s it looks like the St. Louis Arch on its side.

 

 

How does is develop? No one is exactly certain, but we do know it is due to asymmetric growth of the vertebra which occurs during the pubertal growth spurt, the second fastest time of spine growth.  So the individuals are normal alignment when they are 9-10 years of age and then develop more and more kyphosis as they go through puberty.

 

Is it due to sports or wearing a heavy backpack? No

 

Can it be prevented? If it is identified very early bracing may be an option to prevent worsening.

 

What are the main symptoms of Scheuermann’s?

1.      The obvious physical changes of the body, the pronounced angular deformity of the back.

2.      Back pain.  Pain develops over the angular area of the back and also the low back, which needs to hyperextend to compensate for the increased thoracic kyphosis.

 

Can physical therapy help? Physical therapy can help the back pain related to Scheuermann’s.  Working on aerobic conditioning and strengthening the back and core musculature can decrease pain.  However, it will not change the Scheuermann’s deformity.

 

When is surgery an option? In general surgery is an options for deformities greater than 75 degrees and the patient is having significant back pain which is not responsive to nonsurgical management (physical therapy, over-the-counter medications, weight loss, aerobic conditioning).

Does surgery have to be done for deformities >75 degrees? No.  If the person doesn’t have significant pain then surgery is not needed.

 

What is the long-term implications of Thoracic Scheuermann’s Kyphosis? Mainly pain.  All the other quality of life measures, such as function, job, etc… is the same with and without Scheuermann’s kyphosis.

 

The next blog post will be on the surgery for Thoracic Scheuermann’s Kyphosis……

 

Blog Topic: Talking Points for Early-Onset Scoliosis Patients: Magnetically-Controlled Growing Rods vs. Shilla Growth-Guidance

8-23-2022

 

In the surgical treatment of Early-Onset Scoliosis (EOS) the options boil down to two main constructs:

 

Distraction-Based: this encompasses both Traditional Growing Rods (TGR) and Magnetically-Controlled Growing Rods (MCGR)

            Growth-Guidance: this is also called the “Shilla Procedure”

 

We will not go into detail about these two spine constructs, but ask you go back in this blog to older posts to get the information you are interested in obtaining for you or your child.

The below table is a breakdown of the similarities and differences between Shilla Growth Guidance and Magnetically-Controlled Growing Rods.  This table can be used to stimulate and augment discussions with pediatric spine surgeons about the two constructs, and which is more appropriate for their child.

 

Blog Topic: Blood Management During Spine Deformity Surgery

8-22-2022

 

In 2022, spine deformity surgery usually requires a long incision and temporary retraction of muscles from the spine.  This extensive exposure of the spine helps to loosen up the spine (to get better correction), insert pedicle screws to grip the spine and place the long rods, which moves the spine in space and maintains the correction in its new position (while the spine fusion develops).

 

 

This type of exposure, and the amount of time required for these surgeries (4-6 hours), creates the opportunity to have significant blood loss. Does the amount of blood loss in surgery matter? The answer is “yes”. There is a convincing amount of published research which documents lower complications and better patient outcomes when the blood loss from surgery is low.

 

 

 

During surgical procedures in the operating rooms there are various methods to minimize or stop bleeding, from intravenous medications to topical materials to surgical technique.  In spine deformity surgery, some of these are effective and easy to do, while others are not as effective or require changes in the execution of surgery.   

So how do we minimize blood loss during pediatric spinal deformity surgery? Here are a few of methods we utilize on a daily basis:

Meticulous surgical technique: During surgery it is important to identify any and all bleeding.  Electrocautery is used to stop the bleeding.

Use of tranexamic acid: This medication is given by vein, through an IV, during surgery and has been demonstrated to decrease bleeding.

Topical hemostatic agents: These materials are applied on the surfaces of muscle and bone which coagulates bleeding.

Use of red blood cell scavenging: During surgery we suction blood out of the wound and this type machine collects, filters and spins down to concentrate the blood.  We can then give this concentrated back to the patient.

 

Blog Topic: The Use of Internal Distraction in Severe Scoliosis

8-7-2022

In severe scoliosis, the use of traction has demonstrated an ability to improve the spinal deformity before surgery was actually performed.  There are three main methods:

1.    1. Preoperative halo-gravity traction

2.    2.   Intraoperative halo-femoral traction

3.    3. Intraoperative Internal Dis-Traction

This post will focus on #3: Intraoperative Internal Dis-Traction

To demonstrate this treatment we will use the case of a 13 year old female who has severe scoliosis measuring 105 degrees.  Treatment thus far has been observation.  She had been having daily back pain which prevented her from playing athletics. 

Due to the severe scoliosis a total spine MRI was ordered and a thoracic syrinx was diagnosed (treated nonoperatively).

I call her type of scoliosis: neurogenic.  Many surgeons will call this neuromuscular but I don’t think it is correct to included this type of patient into the same group as cerebral palsy, spina bifida, spinal muscle atrophy, etc….diagnoses.

The image, below far right, is a push prone.  This image demonstrates that when a force is exerted on the spine the scoliosis improves from 105 degrees to 77 degrees.

On the below right sidebender (right side radiograph) the deformity decreases to 82 degrees.

Next are a picture and radiograph taken in surgery, which both demonstrate Intraoperative Internal Dis-Traction.  After exposure of the spine multiple osteotomies (posterior column osteotomies or PCOs) are done to make the spine more flexible, and allow more correction of the scoliosis.

Then a few screws are placed in the lower part of the spine (red circle), then hooks are placed on 4 ribs on the concave side of the scoliosis (yellow circle).  These two foundations are then connected by a rod and then distraction can be done to improve the scoliosis, which you can see it is much better than it was before surgery.

After this rod is placed the remainder of all the pedicle screws are inserted.  Distraction is done multiple times to gradually improve the scoliosis.  It is important to have spinal cord monitoring as the Dis-Traction can make the spinal cord not work normally.

In surgery the right rod is placed, then the Dis-Traction rod is removed, and a new left rod is placed.  During the rod placements more and more and more correction is safely obtained.

The below radiographs demonstrated the postoperative correction, improved from 105 degrees to 38 degrees.

Overall a nice correction in both the front and side views of the spine.