Elsevier

Spine Deformity

Volume 7, Issue 6, November 2019, Pages 857-864
Spine Deformity

Case Series
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?

https://doi.org/10.1016/j.jspd.2019.01.010Get rights and content

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.

Introduction

Management of early-onset scoliosis aims to improve and prevent deformity progression while accommodating and promoting growth of the spine and thoracic cavity. As early thoracic fusions in young patients whose lungs are immature and developing is associated with unacceptably poor functional results [1], [2], [3], [4], the old saying of a short, straight spine is better than a long, curved spine has been debunked. However, when to proceed with definitive fusion in patients with early-onset scoliosis continues to be an area of interesting debate and one without ultimate consensus.

Thoracic height measured between T1 and T12 is one radiographic marker used to guide timing of definitive fusion in this patient population, as it has been associated with pulmonary function tests (PFTs) [1], [5], [6]. In a landmark article by Karol et al., children who underwent early spinal fusions demonstrated compromised PFTs when thoracic height was <22 cm [1]. Although this threshold has been a benchmark, its association with appropriate long-term pulmonary function has recently been questioned [6]. As such, the goals of this study are twofold: (1) to develop normative data of PFTs and radiographic measures of chest development in normal children, and (2) 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.

Section snippets

Cohort

After approval from the Institutional Review Board, a tertiary-care children hospital's pulmonology database was queried to identify all children who underwent PFT evaluation. After including only children with PFT values >90% and without chest or spinal deformity, a radiology database was cross-referenced to identify all children who had a chest radiograph within two months of PFT studies. For each child, the following PFT and radiographic data were collected.

Pulmonary function data

  • 1.

    Absolute forced vital capacity

Cohorts

A total of 1,797 children were identified who underwent PFTs. Of this group, 149 children (average age 12.4 ± 3.0 years, range 7.1–18.4 years) met inclusion criteria. Demographic data are presented in Table 1. There were nearly twice as many girls (n = 97) as boys (n = 52). Number of girls by age group were as follows: <10 years (n = 25; average age 8.6 ± 0.8), 10–12 years (n = 16; average age 10.9 ± 0.5), 12–14 years (n = 17; average age 12.7 ± 0.5 years), and >14 years (n = 39; average age

Discussion

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 [1], [2], [3], [4]. In this study, we present two major findings: 1) normative data of pulmonary function tests (PFTs) and radiographic measures of chest development in normal children and 2) a child whose T1–T12 height is halted and maintained at 22 cm to skeletal maturity is predicted to have FEV1 and FVC values <50% of

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.

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    Author disclosures: AAT (none), JS (none), MK (none), JRG (none), SJL (none).

    IRB approval: This study was approved by the Washington University School of Medicine Institutional Review Board (#201706176).

    Funding Source: No funding.

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