Pilot study on effectiveness and safety of Shape Memory Scoliosis Correction Instrument

1. INTRODUCTION AND RATIONALE

The main reason for patients to undergo surgical intervention for Idiopathic
Scoliosis is to reduce Rib Hump.
The standard procedure for correction of the deformity will reduce the lateral
and kyphotic deformation but does not correct the rotation of the vertebrae
whereas the main influence on hump reduction is the de-rotation of the spine.
This lack of de-rotation is not due to the implant which fixates the vertebrae
but due to the limited possibilities of the current instruments available to
correct the deformity prior to placing the rods.
A recent article by Cheng et al.[1] showed that in the current standard
procedure the forces during de-rotation exerted by the instruments on the
pedicle screws are high and can cause failure of the vertebra.

This pilot study is set up to asses clinically that the Shape Memory Scoliosis
Correction (SMSC) Instrument is capable of simultaneous 3D correction on all
levels prior to placing the implants as used in the standard procedure.

Compared to the standard procedure the only difference is the instrument used
to correct the deformity prior to placement of the rods. All implants (rods and
pedicle screws) are the same as in the standard procedure.

The advantages of the SMSC instrument over the standard instruments:
• Simultaneous 3D correction vs 2D correction
• Simultaneous correction on all levels vs correction per level
• Locking of the desired correction until the rods are placed
These advantages combined should result in correction of the deformation
including de-rotation and thereby result in a decrease of the rib hump

The SMSC instrument has been tested with good results on its safety and
function in mechanical tests and functional tests on sawbone.
There is no literature found on an instrument to correct Scoliotic deformation
simultaneous in 3D on all levels, so there is no prior data on this type of
correction.
Due to the specific behaviour of the human spine it is only possible to show
its effectiveness during a clinical trial.
[1] Cheng I, Hay D, Iezza A, Lindsey D, Lenke LG., Biomechanical analysis of
derotation of the thoracic spine using pedicle screws., Spine, 2010 May
1;35(10):1039-43.

Primary Objectives:
• show effectiveness of the SMSC instrument in 3D correction of the spine prior
to placement of the implants.
The hypothesis is that to achieve de-rotation of the spine without failure of
the pedicle screws, de-rotation has to be done simultaneous over all levels and
in combination with lateral and kyphotic correction to minimize increased
correction forces due to interaction between the separate vertebra.

• Show significant rib hump reduction after the standard procedure with the use
of the SMSC instrument.
The hypothesis is that there is no significant rib hump reduction without
de-rotation of the spine

STUDY DESIGN


The study is set up as an observational study: a case series of 15 subjects.

The duration of the study is 1 year.
The follow-up is conform the standard procedure and is not included in the
trial.
The data to confirm the objectives is collected during and immediately after
the surgery

The study is performed at the UMCG

Burden: Time in surgery increased by approx. 20 minutes.

Risks associated with the investigational product: If the investigational
product does not correct as foreseen or can not be fitted to the patient it
will be removed and the standard instruments will be used. Risk for the patient
is an additional 20 minutes operating time

Benefit: Patient will have a higher rate of reduction of the deformity compared
to the use of the standard instruments.