The association between aerobic capacity and spinal deformity in patients with adolescent idiopathic scoliosis – a systematic review

Abstract

Introduction: While patients with severe adolescent idiopathic scoliosis (AIS) are known to have poor aerobic capacity, it remains unclear if some components of spinal deformities are related to aerobic capacity in patients with various severity of AIS. However, no systematic review has summarized the relations between these components and aerobic capacity in AIS patients, which may inform clinical practice. Objective: To summarize the relations between various structural parameters and aerobic capacity of AIS patients during exercise tolerance tests. Methods: Potential citations were searched from 8 electronic databases, from inception to November 2016. Two reviewers independently screened the titles, abstracts, and full-text of potential articles based on the preset criteria. Two other independent reviewers extracted data and appraised the ethodological quality of the included studies using established evaluation tools. Associations between spinal parameters and aerobic capacity were summarized qualitatively. Results and Discussion: Eight of 1,045 identified citations (377 patients) were included. The overall methodological quality was low to moderate. Most included studies did not justify sample sizes nor adjust for confounders. Treadmill exercise tolerance tests (treadmill tests) and cycloergometer exercise tolerance tests ( bike tests) estimated diverse aerobic capacity of AIS patients (expressed as maximum oxygen intake (VO2max)). Using treadmill tests, 3 studies noted that the mean body weight normalized VO2max in patients with mild to moderate AIS (Cobb angles between 20° and 45°) was significantly lower than the normative values. Likewise, 2 studies found that patients with mild curves had significantly poorer ventilatory efficiency (i.e. higher ventilation volume per VO2max) than healthy controls during a treadmill test. A study found that increased thoracic Cobb angles were associated with decreased VO2max (r = -0.71; p < 0.01). Another study showed that patients with mild to moderate curves had significantly poorer exercise tolerance, lower anaerobic thresholds and a higher breathing frequency than healthy controls during treadmill tests. Conversely, using bike tests, 3 studies found that the curve angle or number of scoliotic vertebrae was unrelated to body weight normalized VO2max or maximum tidal volume/inspiratory capacity ratio. Interestingly, a study found that patients with Cobb angles >40° showed slightly decreased VO2max and mild hyperventilation during a bike test. Conclusion and Significance: While our results showed that patients with mild thoracic curves have suboptimal aerobic capacity, these findings might be confounded by other factors (e.g. muscularity). Future cohort studies should examine if suboptimal aerobic capacity in AIS patients is related to poor fitness level or spinal deformities. However, given the benefits of aerobic exercises on aerobic capacity, regular aerobic training is recommended for AIS patients.