Are lung functions related to spinal deformities in patients with adolescent idiopathic scoliosis? A systematic review and meta-analysis

Abstract

Introduction: Some studies have shown that teens with adolescent idiopathic scoliosis (AIS) display pulmonary impairments although conflicting findings have been reported. To better identify and manage AIS patients with pulmonary impairments, a meta-analysis is warranted to summarize the correlations between various lung function parameters and structural features of AIS patients. Objective: To summarize the associations between various lung function parameters and radiographic phenotypes of AIS patients. Methods: Candidate publications were identified from 8 electronic databases, from inception to November 2016. Two independent reviewers screened the titles, abstracts, and full-text of potential articles based on the selection criteria. Another 2 independent reviewers extracted relevant data and appraised the methodological quality of the included studies using established assessment tools. The relations between various pulmonary parameters and spinal parameters were summarized qualitatively. Meta-analyses were conducted using random-effects models, if possible. Results and Discussion: Of 1,045 identified citations, 18 studies (3,075 participants) met the inclusion criteria. Fourteen included studies (2,766 patients) reported significant low-to-moderate associations between diverse spinal parameters (e.g., axial vertebral rotation) and lung functions (e.g., percent predicted functional vital apacity (%FVC), percent predicted forced expiratory volume in one second (%FEV1), and percent predicted total lung capacity (%TLC)) in AIS patients. Three included studies found that patients with impaired lung functions (<65 %FEV1 or %FVC) had significantly larger thoracic Cobb angles and less thoracic kyphosis than healthy controls. Homogenous data from 10 studies were pooled for meta-analyses. The results showed that larger thoracic Cobb angles were related to lower %FVC (r= -0.34; 95%CI: -0.39 to -0.29), lower %FEV1(r = - 0.33; 95%CI: -0.39 to -0.27), smaller %TLC (r = -0.19; 95%CI: -0.25 to -0.13), and smaller percent predicted vital capacity (r = -0.28; 95%CI: -0.34 to -0.22). Conversely, thoracic kyphosis angles were positively associated with %FVC (r= 0.11; 95%CI: 0.07 to 0.15), %FEV1 (r = 0.23; 95%CI: 0.18 to 0.27), and %TLC (r = 0.19; 95%CI: 0.15 to 0.24) (Figure 1). Many included studies had suboptimal methodological quality. Notably, they did not justify the sample sizes, and did not report response rates, information about ethics approval, and confounders. Conclusion and Significance: Severe spinal deformities were related to clinically significant pulmonary impairments in AIS patients. However, these findings were not adjust for confounders (e.g. physical activity levels). Future studies should consider the influences of other factors (e.g., physical activity levels) in restoring the lung functions of these patients by non-surgical and surgical means.