Tuesday, January 10, 2023

 Blog Topic: Neuromuscular Scoliosis: Use of Magnetically-Controlled Growing Rods

1-10-2023

 

In the second-to-last blog post the concept of using Magnetically-Controlled Growing Rods (MCGR) was presented for treatment of NeuroMuscular Scoliosis (NMS). In that post the different cranial/upper and the caudal/lower foundations were discussed briefly, and the reasons for why we choose one type over another.  In this post the use of proximal screws and distal pelvic fixation will be presented.

 

Below is a 7 year old female with cerebral palsy and NMS.  Her parents have noticed she is curving her body more, is having more difficulty with sitting, and is not tolerating sitting for very long periods of time which makes travel and school participation very difficult.

 

Because this 7 year old girl had a progressive, severe spinal deformity which is impacting her quality of life, we entered into shared-decision making with parents around surgical options.  So, what are our goals of surgery?

#1: Correct spinal deformity

#2: Improve sitting

#3: Improve sitting intolerance/pain

#4: Permit vertical growth of the spine

The only way to address all 4 of these goals is to use a “growth-friendly” instrumentation, which is to use either a distraction-based construct or Shilla Growth Guidance Construct.  My present preference is to use a distraction-based construct in neuromuscular patients, though I am using Shilla Growth Guidance Constructs more and more.

 

The below radiographs demonstrate the flexibility of the spine deformity.  The Supine image is done with the patient lying on their back, simply taking gravity off the spine.  The Push Supine is also done laying down, but then there are two individuals using lead gloves to create three-point push on the body/spine to further improve the spine deformity. This Push Supine significantly corrects the deformity, and gives us a good idea of what type of correction will be obtained in surgery.  Hence, for this patient a distraction construct will provide good correction.

 

After the decision was made to use a distraction-based construct, the next step is to decide what type of actuator or lengthening mechanism can be used.  If the kyphosis is rigid on the lateral radiograph (far right radiograph, above) then we may not be able to use a magnetically-controlled growing rod, and use a traditional growing rod (TGR).  The downside to TGRs is the need for surgically lengthening in the operating room every 6 months.  However, if the kyphosis is flexible, then we can be fairly reassured that we can place a magnetically-controlled growing rod.  The below radiograph is a lateral radiograph, with the patient lying on a bolster, which causes the spine to hyperextend and if the spine if flexible the kyphosis will significantly improve.  As you see in the below radiograph, this spine has a very flexible kyphosis.

 

A magnetically-controlled growing rod construct, 2 rods, were placed from the cranial foundation of pedicle screws T2-T3-T4 down to two S-hooks on top of the iliac wings. As mentioned 2 blog posts ago, the cranial (top) foundation can be hooks on ribs or screws on the spine.  The placement of T2-T3-T4 pedicle screws, in this case, nice balances the very strong pelvic fixation of two iliac S-hooks.  The decision to use these S-hooks, rather than L5-S1-Iliac screws, was made to preserve the fixation points for the definitive fusion at, or near, the end of skeletal growth.

 

 

As you see above the growing rods nicely improves the oblique pelvis (left radiograph to the 2nd from left radiograph) and scoliosis.  The 2nd two radiographs on the right demonstrates the improvement of the kyphosis.

 

Three years after surgery (below) the spine deformity remains nicely corrected.

 

So how much did we lengthen the magnetically-controlled growing rods? The below pictures show the rods immediately after surgery and then at the 3 years after surgery time point.  The area identified in red is a distraction of 48 mm!

 

More to come on growing rods….

Tuesday, January 3, 2023

 

Blog Topic: Recent Publication on Anterior Vertebral Body Tethering (AVBT) Compared with Posterior Spinal Fusion for Major Thoracic Curves: A Retrospective Comparison by the Harms Study Group

1-3-2023

 

 

Study Cohort: Thoracic Idiopathic Scoliosis patients who underwent Anterior Vertebral Body Tethering (AVBT) with minimum 2-year follow-up after surgery and propensity matched to Posterior Spinal Fusion (PSF) patients from Harms Study Group multicenter database.

237 AVBT patients (thoracic curve tethered only) vs. 237 PSF patients

Propensity matched using: age, preoperative thoracic curve magnitude, sex, and grouped Risser sign

All but one AVBT were Lenke 1 or 2

 

Measures: Compared preoperatively and at >/= 2-year follow-up.

               Radiographic data

               Clinical data

               Scoliosis Research Society 22-Item Questionnaire (SRS-22)

 

Results:

              

Preoperatively AVBT patients:

1.3 years younger (p<0.001) than PSF group

Triradiate cartilage were open in 59% (vs. 19% in PSF)

Smaller preoperative curves (5 degrees; p<0.001) than PSF group

               More Lenke 1 curves (81%) vs. PSF (64%)

 

Postoperatively AVBT patients:

               21 degrees correction from preop (44% correction) vs. PSF 33 degrees (62% correction)

               1 degree improvement from initial postop to final vs. 4 degrees worsening for PSF.

Residual thoracic curve


<35 degrees in 76% (vs. 97% for PSF)

Improvement of Angle of Trunk Rotation: 6 degrees (preop to postop) vs. 9 degrees (PSF)

 

LIV: T10-L3 vs. PSF T10-L4; on average PSF was 1 level longer than AVBT

 

 

Complications:

AVBT broken tethers documented in 20%

Secondary surgeries:

               AVBT: 46 procedures in 38 patients (16%)

               PSF: 4 procedures in 3 patients (1.3%)

 

SRS-22: AVBT group with less improvement in pain and self-image

 

Secondary, more stringent propensity matching:

               AVBT improved 22 degrees (preop to postop) and PSF 33 degrees

               Revision rate: AVBT 10% vs. PSF 2%

 

 

Study Problems and Issues:

No reporting of Lumbar Modifiers. This can impact the outcomes of AVBT and PSF.

No power analysis was reported.

Despite primary propensity matching, the two groups were statistically different for age and curve magnitude.

There were separate cohorts analyzed in the study which is confusing. It can be assumed by the reader the more stringent propensity-matching was done primarily, and was likely underpowered, so there were few significant findings. Hence a less stringent propensity-matching analysis was performed and is the bulk of the statistical findings.

“Angle of trunk rotation” was not defined but could be assumed to be from a scoliometer measurement.

No report on how missing data was handled statistically

No Sanders grading (only Risser grades)

Minimum follow-up 2 years and mean follow-up 2.2 years +/-0.5 (which means some patients did not reach two-year follow-up).  This is a very short follow-up for AVBT and longer follow-up will likely demonstrate high tether breakage, loss of correction and higher reoperation rate.

 

Take-away message:

               In this short follow-up study, Posterior Spinal Fusions (PSFs) when compared to Anterior Vertebral Body Tethering (AVBT) of the thoracic spine:

Better corrected the deformity (+11 degrees coronal, +3 degrees rotational)

Were instrumented with 1 more vertebral level distally

5-12 times lower reoperation rate

               Had 21% more patients with a thoracic curve less than 35 degrees

               Reported better improvement in pain and self-image

 

This information needs to be discussed before surgery to achieve shared decision-making.  Both procedures correct the deformity but due to the short length of follow-up the use of AVBT in this patient population should be approached with caution.

Saturday, December 31, 2022

 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 2nd from the left and the 4th 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.


Saturday, November 26, 2022

 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:






Saturday, November 5, 2022

 


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…..

 

Friday, October 28, 2022

 

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.