Study design: The medical records of 138 subjects with Early Onset Scoliosis (EOS) from 5 US institutions were reviewed to analyze their hemoglobin levels before and after surgery. Eighty-five subjects were operated with the Vertical Expandable Prosthetic Titanium Rib (VEPTR) and 53 with growing rods.
Objective: To estimate the prevalence of hypoxia and thoracic insufficiency using hemoglobin as a surrogate marker for pulmonary function, and to measure the effect of spine surgery with expandable devices.
Summary of background data: An early intervention with expandable devices might improve pulmonary function. This hypothesis is difficult to test in young subjects because the standard pulmonary function tests require that the patient be at least 7-year old. Previous studies demonstrated that hemoglobin levels are correlated with chronic hypoxemia.
Methods: Blood data were collected before and 6 to 24 months after surgery. The hemoglobin and hematocrit levels were converted into Z-scores, using age-adjusted references to perform t test paired comparisons.
Results: The prevalence of elevated hemoglobin and hematocrit levels in EOS was 23.2% and 22.5%, respectively. The mean hemoglobin Z-score decreased from 1.26 to 0.92 (P = 0.03) after surgery and the hematocrit Z-score changed from 0.90 to 0.88 (P = 0.90). In the VEPTR group, the mean hemoglobin Z-score decreased from 0.98 to 0.69 (P = 0.20) and in the subgroup of subjects who had an expansion thoracostomy, it decreased from 0.82 to 0.24 (P = 0.04). In the subjects operated with growing rods, the hemoglobin Z-score decreased from 1.75 to 1.32 (P = 0.83).
Conclusion: Twenty-three percent of the patients with EOS showed signs of chronic hypoxia. The hemoglobin levels decreased significantly 6 to 24 months after surgery. The greatest effect was observed in subjects with congenital scoliosis and rib fusion and who had an expansion thoracostomy with implantation of VEPTR.