TIS is the inability of the thorax (chest) to support normal breathing and lung growth. Causes of TIS include:
Normal development of the chest includes:
TIS affects the chest's function of moving air in and out of the lungs. Patients with this condition can't maintain normal respiration or lung growth. The thorax (spine, rib cage, and sternum) is the engine of respiration. It must have adequate space for the lungs to grow and it must be able to change that volume for breathing (respiration) to occur. In TIS, the 3-dimensional deformity of the thorax—volume, symmetry and function—can limit its important role as a respiratory engine.
For the thorax to have optimal efficiency as a respiratory pump, it must have ideal volume for age, the ribs need to have a symmetrical shape in order for them to move properly, and the diaphragm muscle must be properly anchored at the base of the chest. With fused or missing ribs associated with some forms of scoliosis, the concave side of the curve can contain a lung constricted by the fused ribs.
Additional loss of thoracic volume may be seen in scoliosis when the curve rotates the spine into the chest on the convexity of the curve, often protruding deeper into the chest in a deformity called lordosis (sway back), flattening the chest with loss of thoracic volume. In this instance, the ribs cannot move well enough to help with respiration, and breathing becomes totally dependent on the diaphragm muscle.
Increasing deformity of the thorax results in greater volume loss and may lead to breathing problems to a point that a child may require oxygen or even ventilator support.
A new surgical technique—VEPTR (vertical expandable prosthetic titanium rib) thoracoplasty—treats the combined thoracic deformity (spine/rib cage) in skeletally immature patients by enlarging the constricted chest and straightening the spine indirectly without a spine fusion. VEPTR surgery is extensive. Devices are placed under the scapula (shoulder blade) and are attached to the ribs near the neck and continue down to either the spine, or the ribs near the waist to help stabilize the surgically expanded chest wall constriction (expansion thoracoplasty).
To accommodate later growth, the devices are expanded twice a year in outpatient surgery through small incisions. Some centers are using the VEPTR device as a means to straighten the spine indirectly via the ribs and chest wall. Long-term follow-up studies of this technique are underway. Currently, there are a limited number of institutions offering VEPTR surgery. Your child's spine surgeon can advise whether your child's condition is appropriate for VEPTR treatment and provide referral information, if needed.