Background: Previous research has suggested a correlation between
pulmonary impairment and thoracic spinal deformity. The curve magnitude,
number of involved vertebrae, curve location, and decrease in thoracic
kyphosis independently contribute to pulmonary impairment, but the strength of
these associations has been variable. The objectives of this study were to
test the hypothesis that increased thoracic deformity is associated with
decreased pulmonary function and to determine which, if any, radiographic
measurements of deformity predict pulmonary impairment.
Methods: Preoperative pulmonary function testing and radiographic
examination were performed on 631 patients with adolescent idiopathic
scoliosis. Correlation analysis and subsequent stepwise multiple regression
analysis were carried out to assess the associations between radiographic
measurements of deformity and the results of pulmonary function testing.
Results: The magnitude of the thoracic curve, the number of
vertebrae involved in the thoracic curve, the thoracic hypokyphosis, and
coronal imbalance had a minimal but significant effect on pulmonary function.
While these four factors were associated with an increased risk of moderate or
severe pulmonary impairment, they explained only 19.7%, 18.0%, and 8.8% of the
observed variability in forced vital capacity, forced expiratory volume in one
second, and total lung capacity, respectively. The degrees of scoliosis that
were associated with clinically relevant decreases in pulmonary function were
much smaller than previously described, but the majority of the observed
variability in pulmonary function was not explained by the radiographic
characteristics of the deformity.
Conclusions: Some patients with adolescent idiopathic scoliosis may
have clinically relevant pulmonary impairment that is out of proportion with
the severity of the scoliosis, and this may alter the decision-making process
regarding which fusion technique will produce an acceptable clinical result
with the least additional effect on pulmonary function.