The effect of opening wedge thoracostomy on thoracic insufficiency syndrome associated with fused ribs and congenital scoliosis.

BACKGROUND: Thoracic insufficiency syndrome is the inability of the thorax to support normal respiration or lung growth and is seen in patients who have severe congenital scoliosis with fused ribs. Traditional spinal surgery does not directly address this syndrome. METHODS: Twenty-seven patients with congenital scoliosis associated with fused ribs of the concave hemithorax had an opening wedge thoracostomy with primary longitudinal lengthening with use of a chest-wall distractor known as a vertical, expandable prosthetic titanium rib. Repeat lengthenings of the prosthesis were performed at intervals of four to six months. Radiographs were analyzed with respect to correction of the spinal deformity, as indicated by a change in the Cobb angle, and lateral deviation of the spine, as indicated by the interpedicular line ratio. Spinal growth was assessed by measuring the change in the length of the spine. Correction of the thoracic deformity and thoracic growth were assessed on the basis of the increase in the height of the concave hemithorax compared with the height of the convex hemithorax (the space available for the lung), the increase in the thoracic spinal height, and the increase in the thoracic depth and width. The thoracic deformity in the transverse plane was measured with computed tomography, and the scans were analyzed for spinal rotation, thoracic rotation, and the posterior hemithoracic symmetry ratio. Clinically, the patients were assessed on the basis of the relative heights of the shoulders and of head and thorax compensation. Pulmonary status was evaluated on the basis of the respiratory rate, capillary blood gas levels, and pulmonary function studies. RESULTS: The mean age at the time of the surgery was 3.2 years (range, 0.6 to 12.5 years), and the mean duration of follow-up was 5.7 years. All patients had progressive congenital scoliosis, with a mean increase of 15 degrees /yr before the operation. The scoliosis decreased from a mean of 74 degrees preoperatively to a mean of 49 degrees at the time of the last follow-up. Both the mean interpedicular line ratio and the space available for the lung ratio improved significantly. The height of the thoracic spine increased by a mean of 0.71 cm/yr. At the time of the last follow-up, the mean percentage of the predicted normal vital capacity was 58% for patients younger than two years of age at the time of the surgery, 44% for those older than two years of age (p < 0.001), and 36% for those older than two years of age who had had prior spine surgery. In a group of patients who had sequential testing, all increases in the volume of vital capacity were significant (p < 0.0001), but the changes in the percentages of the predicted normal vital capacity were not. There was a total of fifty-two complications in twenty-two patients, with the most common being asymptomatic proximal migration of the device through the ribs in seven patients. CONCLUSIONS: Opening wedge thoracostomy with use of a chest-wall distractor directly treats segmental hypoplasia of the hemithorax resulting from fused ribs associated with congenital scoliosis. The operation addresses thoracic insufficiency syndrome by lengthening and expanding the constricted hemithorax and allowing growth of the thoracic spine and the rib cage. The procedure corrects most components of chest-wall deformity and indirectly corrects congenital scoliosis, without the need for spine fusion. The technique requires special training and should be performed by a multispecialty team.

The characteristics of thoracic insufficiency syndrome associated with fused ribs and congenital scoliosis.

1. Thoracic insufficiency syndrome is the inability of the thorax to support normal respiration or lung growth. 2. The rare condition of fused ribs and congenital scoliosis may result in a three-dimensional thoracic deformity with adverse effects on thoracic growth and function with development of thoracic insufficiency syndrome. 3. The normal thorax is defined by two characteristics: normal, stable volume and the ability to change that volume. Volume depends on the width and depth of the rib cage, and the thoracic spine provides height. The ability to change volume, termed thoracic function, is provided by the diaphragm and the secondary muscles of respiration. 4. On radiographs, the loss of the vertical height of the lung of the concave, restricted hemithorax is defined by the percentage of space available for the lung. 5. Spine rotation causes a windswept thorax, with both restriction of the volume of the convex hemithorax and restriction of the motion of the involved ribs. 6. Constrictive three-dimensional deformity of the thorax may cause extrinsic, restrictive lung disease. 7. Progressive thoracic insufficiency syndrome is diagnosed on the basis of clinical signs of respiratory insufficiency, loss of chest wall mobility as demonstrated by the thumb excursion test, worsening indices of three-dimensional thoracic deformity on radiographs and computed tomography scans, or a relative decline in percent predicted vital capacity due to thoracic "failure to thrive," as demonstrated by pulmonary function tests. 8. Treatment of progressive thoracic insufficiency syndrome should provide an acute increase in the thoracic volume with stabilization of any flail chest-wall defects and maintain these improvements as the patient grows, without the need for spine fusion.