Normative Data of Pulmonary Function Tests and Radiographic Measures of Chest Development in Children Without Spinal Deformity: Is a T1-T12 Height of 22 cm Adequate?

ABSTRACT

STUDY DESIGN: Retrospective case series. OBJECTIVES: To develop normative data of pulmonary function tests (PFTs) and radiographic measures of chest development in normal children and to determine if the prior proposed T1-T12 height of 22 cm for spinal fusion in a growing child is adequate for pulmonary function based on normative PFT values at skeletal maturity. SUMMARY OF BACKGROUND DATA Shortening of the spine from T1-T12 is a concern with early thoracic fusion for spinal deformity, as it has a deleterious effect on the development of the pulmonary system. METHODS: Children with mild asthma who had pulmonary function tests (PFTs) >90% and without chest or spinal deformity were identified. PFT data included absolute forced vital capacity (FVC), %-predicted FVC, absolute forced expiratory volume in one second (FEV1), %-predicted FEV1, and FEV1/FVC. Radiographic measurements performed on chest radiographs included T1-T12 height, coronal chest width (CCW), and space available for the lung (SAL) bilaterally. These data were analyzed for all patients and for patients with T1-T12 heights 22-24 cm. To assess the impact of T1-T12 shortening on PFTs at skeletal maturity, spirometric standards for healthy adult lifetime nonsmokers were used. RESULTS: Of 1,797 PFT studies, 149 children (average age 12.4 ± 3.0 years; girls, 97) were analyzed. For the entire cohort, PFT values were as follows FVC 3.0 ± 0.9 L, %-predicted FVC 103.9% ± 10.6%, absolute FEV1 2.7 ± 0.9 L, %-predicted FEV1 106.9% ± 11.1%, and FEV1/FVC 90.7% ± 2.6%. The averages for T1-T12 height was 25.6 ± 3.8 cm, CCW 25.5 ± 3.4 cm, and SAL bilaterally 19.0 ± 3.5 cm. For the 21 patients (girls 11; average age 9.7 ± 1.4 years) with T1-T12 heights 22-24 cm, absolute FVC was 2.2 ± 0.3 L, %-predicted FVC was 104.0% ± 13.0%, absolute FEV1 was 2.0 ± 0.3 L, %-predicted FEV1 was 108.2% ± 15.0%, and FEV1/FVC was 91.0% ± 2.7%. If these kids with 22-24 cm T1-T12 heights maintained the same thoracic height, they were calculated to have %-predicted FVC of 44% (girl) and 42% (boy) and %-predicted FEV1 of 42% (girl) and 43% (boy) at skeletal maturity (15 years old). CONCLUSIONS: Percent-predicted FEV1 and FVC values for normal children with a T1-T12 height of 22 cm at skeletal maturity were <50%. Though this analysis does not take into consideration radial expansion of the chest or children with scoliosis (idiopathic, congenital, neuromuscular), these values are concerning and may not be adequate to guarantee that children with early-onset scoliosis who are fused with T1-T12 heights of 22 cm will have an asymptomatic pulmonary status in adulthood. LEVEL OF EVIDENCE Level IV.