Abstract
Adolescent idiopathic scoliosis (AIS) is associated with decreased respiratory quality of life and impaired diaphragm function. Recent hyperpolarized helium (HHe) MRI studies show alveolarization continues throughout adolescence, and mechanical forces are known to impact alveolarization. We therefore hypothesized that patients with AIS would have alterations in alveolar size, alveolar number, or alveolar septal dimensions compared to adolescents without AIS, and that posterior spinal fusion (PSF) might reverse these differences. We conducted a prospective observational trial using HHe MRI to test for changes in alveolar microstructure in control and AIS subjects at baseline and one year. After obtaining written informed consent from subjects' legal guardians and assent from the subjects, we performed HHe and proton MRI in 14 AIS and 16 control subjects aged 8-21 years. The mean age of control subjects (12.9 years) was significantly less than AIS (14.9 years, p = 0.003). At baseline, there were no significant differences in alveolar size, number, or alveolar duct morphometry between AIS and control subjects or between the concave (compressed) and convex (expanded) lungs of AIS subjects. At one year after PSF AIS subjects had an increase in alveolar density in the formerly convex lung (p = 0.05), likely reflecting a change in thoracic anatomy, but there were no other significant changes in lung microstructure. Modeling of alveolar size over time demonstrated similar rates of alveolar growth in control and AIS subjects in both right and left lungs pre- and post-PSF. Although this study suffered from poor age-matching, we found no evidence that AIS or PSF impacts lung microstructure. Trial registration: Clinical trial registration number NCT03539770.
Highlights
Adolescent idiopathic scoliosis (AIS) affects 2–3% of American adolescents, and approximately ten percent of these children will require posterior spinal fusion (PSF) [1]
We developed this study to investigate whether altered intrathoracic forces in AIS cause impaired alveolarization as has been noted in earlier-onset scoliosis
Data loss occurred in 1 AIS subject after the first scan and in 3 control subjects after the second scan
Summary
Adolescent idiopathic scoliosis (AIS) affects 2–3% of American adolescents, and approximately ten percent of these children will require posterior spinal fusion (PSF) [1]. We developed this study to investigate whether altered intrathoracic forces in AIS (e.g. impaired diaphragm function, compression of the concave lung, and expansion of the convex lung) cause impaired alveolarization as has been noted in earlier-onset scoliosis. The intrinsic diffusion of the gas within the lung is restricted by the alveolar walls, and diffusion imaging provides maps of apparent diffusion coefficients (ADC), alveolar number density (N), mean linear intercept (Lm), and other morphometric properties of the distal airspaces [18, 19] This technique has been used to assess lung structure in normal children [9], children with bronchopulmonary dysplasia [20, 21], and adults with emphysema [22,23,24]. To determine whether patients with AIS experience alterations in distal lung structure and whether PSF reverses these changes, we performed HHe and proton MRI in control subjects and in AIS subjects recommended for PSF with follow up imaging at 1 year
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