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Abstract from the SRS 2002 Annual Meeting
Background: Thoracic Insufficiency Syndrome (TIS) can develop in children
with congenital scoliosis associated with fused ribs and other skeletal deformities
that result in thoracic hypoplasia. TIS limits the growth of the thorax to the
point that the chest is too small to permit the development of normal lung volumes
and pulmonary function as the child matures. Campbell has introduced a technique
for expansion thoracoplasty consisting of an opening wedge thoracostomy followed
by lengthening of the chest wall with an implantable distracter known as the
vertical expandable prosthetic titanium rib (VEPTR). This technique allows for
the surgical expansion of the chest wall in order to facilitate an increase
in lung volume and respiratory function.
TIS is a three-dimensional deformity, and it is difficult to quantify both
the amount of pulmonary compromise and degree of surgical correction with two-dimensional
plain radiography. Accepted techniques for measuring the amount of spinal deformity,
such as the Cobb method, are insufficient to evaluate the results of the treatment
of TIS. However, Computed Tomography (CT) scans can be used to accurately measure
the three-dimensional volume of the thorax and the effect of expansion thoracoplasty
on the size of the lung parenchyma. In addition, this data can be used to generate
holographic images of the thoracic cavity that allow surgeons to visualize the
three dimensional nature of the deformity and the results of surgical correction.
Methods: We reviewed the pre and post-operative radiographs and thoracic
CT scans on 5 patients who underwent expansion thoracoplasty for thoracic hypoplasia.
Pre and post-operative lung volumes were determined for 4 patients by measuring
the area of the lung parenchyma (in mm2) on each 5mm thick CT scan slice through
the thorax. The sequential measurements of lung area were then added together
and multiplied by the slice thickness in order to derive a measurement (in cm3)
of the three-dimensional volume of lung tissue in the thorax. The same CT scan
data was used to generate Voxel holographic images of the thorax before and
after surgical correction of the skeletal deformity.
Results: The volume of lung parenchyma before and after expansion thoracoplasty,
the change in volume, and the percent increase in lung volume for four patients
is presented in the following table:
| Patient |
Pre-op Lung Volume (cm3) |
Post-op Lung Volume (cm3) |
Increase in Volume (cm3) |
% Increase in Volume |
| 1 (P.S.) |
3797.45 |
6352.2 |
2554.7 |
67.3% |
| 2 (N.S.) |
5727.9 |
7015.8 |
1287.9 |
22.5% |
| 3 (W.D.) |
2161.2 |
4084.6 |
1923.4 |
88.9% |
| 4 (D.S.) |
5526.5 |
9028.7 |
3502.2 |
63.4% |
Conclusions: CT scan data is an excellent tool for measuring the three-dimensional
volume of the thorax in TIS. This permits a quantitative analysis of the volume
of lung parenchyma before and after the surgical treatment of the chest wall
and spinal deformities. The same data can be used to generate holographic images
of the thoracic cavity in order to visualize the deformity in three-dimensions
prior to surgical correction and the results of treatment. Further work is needed
to develop protocols for obtaining and measuring CT scan data while minimizing
the effects of respiratory and cardiac motion, and normal parameters for the
age dependent volume of lung parenchyma need to be established.
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