Thoracic Morphology and Bronchial Narrowing Are Related To Pulmonary Function in Adolescent Idiopathic Scoliosis

James Farrell*, Enrique Garrido, Ludvig Vavruch, Tom Schlösser

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background
In adolescent idiopathic scoliosis (AIS) lung function impairment is not necessarily related to the coronal spinal deformity. Recently, right-sided bronchial narrowing has been reported in thoracic AIS. The aim of this study is to describe the relation of chest and spinal deformity parameters, bronchial narrowing and lung volumes with pulmonary function in preoperative AIS.

Methods
Spinal radiographs, low-dose CT scans of the spine including the chest and pulmonary function tests were retrospectively collected for 85 preoperative thoracic AIS patients in two centers and compared to 14 matched controls. Three-dimensional lung and airway reconstructions were acquired. Correlation analysis was performed between radiographic spinal parameters, CT-based chest deformity parameters (rib-hump index (RHi), spinal penetration index, endothoracic hump ratio, hemithoracic-width ratio), lung volume asymmetry and bronchial diameters versus percent-predicted spirometry results.

Results
41 (48%) patients had a FEV1% or FVC% below 65% and 17 (20%) had obstructive lung disease. All chest deformity parameters correlated significantly with FEV1% and FVC%; RHi was found to be the best correlate (rs = -0.52 and -0.54 respectively). AIS patients with impaired pulmonary function had hypokyphosis, larger rib hump, increased spinal and thoracic rotation, narrower right hemithorax and increased intrusion of the spine into the chest. Spinal intrusion correlated with right-sided bronchial narrowing, relative right lung volume loss and decreased FEV1% and FVC%. Multivariate regression including spinal and thoracic deformity parameters, lung volume asymmetry and airway parameters could explain 57% of the variance in FEV1% and 54% of FVC%.

Conclusions
Chest intrusion by the endothoracic hump is related to right-sided bronchial narrowing and lung function loss in preoperative AIS. The findings support that ventilatory dysfunction in thoracic AIS is not only restrictive but frequently has an obstructive component, especially in patients with hypokyphosis. RHi is the most predictive chest parameter for lung function loss.

Level of Evidence
Level III (Retrospective cross-sectional study) 
Original languageEnglish
JournalJournal of Bone and Joint Surgery
Early online date23 Aug 2021
DOIs
Publication statusE-pub ahead of print - 23 Aug 2021

Keywords

  • Scoliosis
  • Thoracic deformity
  • Lung function
  • Rib hump
  • Spinal intrusion
  • Airway obstruction
  • Spinal deformity

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