A Feasibility Study on the use of Percutaneous Instrumentation for less invasive surgery of Scoliosis Deformity in Children with Neuromuscular Disease.

Children with a neuromuscular disease (e.g. muscular dystrophy or cerebral
palsy) or spina bifida will almost always develop a scoliosis deformity. Many
times this deformity does not necessitate operative treatment. Sometimes there
is a problem for the child to fit into his/her wheelchair due to the deformity
of the spinal column (severity of the scoliosis). In these cases one could
decide to perform an operative treatment.

Currently these children are treated by a posterior instrumentation with
pedicle screws and rods on the backside of the spinal column for correction of
the deformity. Sometimes, when the child is quite young and growth of the
spinal column needs to be preserved as much as possible, metal lamina wires
instead of pedicle screws are used over 2 metal rods allowing the child to grow
and shift the wires over the rods for longitudinal growth. In both situations,
the paraspinal muscles need to be stripped from the lamina on the back side of
the vertebral column from neck to pelvis in order to reach a good exposure.
This takes time and usually causes a blood loss of between 500 and 1000 cc of
blood (which can partially be returned to the patient using cell saving
devices). Additionally, postoperative pain can be quite significant. All of
these children will be admitted to the ICU for pain control and respiratory
support. Usually they can be transferred to the clinical wards after 24 hours.

In the past years, new developments using less invasive surgery techniques have
taken place in the treatment of adult spinal trauma patients. This percutaneous
pedicle screw instrumentation system is currently applied on a regular basis in
the UMCU for the treatment of spine fractures due to trauma or pathological
causes such as primary tumors/metastases (the latter usually in addition to
postoperative irradiation). Also the use of this thechnique in combination with
less invasive anterieur spinal column surgery for deformities such as
sponylolisthesis or degenerative scoliosis has been reported in the literature,
making it a logical next step to apply this less invasive technique in children
and adolescents with a scoliosis deformity. Recently, 12 adults with a
degenerative scoliosis were treated with the less invasive percutaneous screw
placement in combination with an anteriorly placed cage using a less invasive
new approach (Anand et al., J Spin Disord Techn, 21(7), 459-467, okt 2008). The
authors found a significant reduction in bloodloss. The follow-up time in this
group is unfortunately quite short at this time making long term prognosis of
this technique impossible to judge (also since the technique was combined with
an anterior cage).

One obstacle could be the achievement of a true bony fusion (spondylodesis).
Traditionally, in the open technique, bone graft is added to the posterior
elements or to the anterior intervertebral space in order to achieve this
fusion. Without this fusion, failure of the instrumentation could be the
result. With the current experience in the UMCU on trauma patients, failure of
the instrumentation was not observed until now. Perhaps a spontaneous fusion in
these traumatically fractured vertebrae is the reason why this has not occured.
Children, in scoliosis surgery, usually have no problem developing a bony
fusion in comparison to adults. It is speculated that children will already
develop a fusion due to surgery itself (the exposure procedure of the spine)
because of their high numbers of stem cells that are triggered to make bone
tissue due to the surgical procedure (stripping of the periosteum from the
vertebral bone). Theoretically it is possible that children will also make this
bone due to the percutaneous (less invasive) surgical procedure. In a
feasibility study we would like to explore the possibility to correct scoliosis
with the less invasive technique in a group of children with a disease state
that causes a scoliosis deformity of the spine that can be easily corrected
peroperatively and who have an activity level that puts less challenges on the
new instrumentation system. Children with muscle dystrofy and/or cerebral
paresis or a high spina bifida have a weak muscle tonus in their legs and
paraspinal muscles making them easy to correct once they are under general
anaesthesia. They usually do not need additional procedures such as the removal
of the facet joints or flavum ligaments to mobilise the spine. These patient
could potentially benefit the most from the new technique, especially since the
trauma of surgery is reduced that may reduce the high rate of especially
pulmonary complications but also infections due to their lower level of
resistance.

To test the surgical feasibility of the less invasive percutaneous pedicle
screw instrumentation system for the treatment of children with a so called
"hypotonic" scoliosis. Additionally, postoperative pain reduction and a reduced
hospital (ICU) stay is examined and considered part of the study objectives.
The latter is however a secondary aim, which may be studied in a second more
extensive study, since the feasibility of this new surgical technique first
needs to be established.

The study is a therapeutic observational study.

All children and adolescents will be treated with the percutaneous less
invasive scoliosis correction. A group of 5 children will be studied first to
observe any surgical adverse events or postoperative complications. When safety
can be warranted, the second half of the study group will be treated.

The burden of the new surgical technique will not be bigger than with the
current technique, potentially even less.

Potential risk factors:

Current risk factors:
- neurological deficit
- wound infections
- postoperative bleedings
- complaints caused by the profile of the fixation device used (screws, rods)

Potential new risk factors:
- loss of correction due to instrumentation failure (because no spondylodesis
procedure is performed, just fixation of the spine)
- (more?) complaints caused by the profile of the fixation device used (screws,
rods)

In case of loss of fixation due to instrumentation failure a secondary
procedure may be needed using the standard open technique.