Choice of spirometric reference values for compensation assessment

Scoliosis and chest cage deformity measures predicting impairments in pulmonary function: a cross-sectional study of 492 patients with scoliosis to improve the early identification of patients at risk

STUDY DESIGN

This study examines the correlations between pulmonary function tests (PFTs) and radiographical measures of spinal deformities in patients with scoliosis.

OBJECTIVE

To define the parameters that enable more accurate predictions of restricted pulmonary function (PF) in patients with scoliosis.

SUMMARY OF BACKGROUND DATA

The early identification of patients with scoliosis who are at risk of developing severe curve progression and restricted PF is critical to improving patient care.

METHODS

A total of 492 patients with a thoracic/thoracolumbar curve (TC) and preoperative PFTs as well as radiographical analysis of the TC and thoracic kyphosis (TK) were assessed. The forced vital capacity (FVC) was expressed as a percentage of the predicted value (FVC%). According to guidelines for the severity of pulmonary impairments, classifications were used: no impairment (FVC > 80%), mild (65 < FVC ≤ 80%), moderate (50 < FVC ≤ 65), and severe impairment (FVC ≤ 50%). Main radiographical parameters were included and statistical analyses were used to identify radiographical predictors and to develop prediction models.

RESULTS

The average age was 17 years, 94% of the patients had adolescent idiopathic scoliosis, 20% had lordoscoliosis (TK <10°). The average FVC% was 75% ± 17%, their average TC was 57° ± 21°, and TK was 26° ± 25°. A total of 38% had no impairment, 37% exhibited mild impairment, 15% had moderate impairments, and 10% were severely impaired. Spinal deformities identified by radiographical analysis (TC, TC-flexibility, apical vertebral rotation, TK, and rib hump) significantly influenced FVC% (P < 0.01). TK logistic regression analysis revealed that 2 factors are predictive for an FVC 50% or less: increased scoliosis with a low TK less than 0° (odds ratio = 7.3) or a high TK more than 60° (odds ratio = 20). A model for predicting FVC values more than 50% was established and shown to achieve a correct classification rate of 94%.

CONCLUSION

Patients with increasing coronal and sagittal plane deformities with a high thoracic scoliosis apex are at the highest risk for reduced FVC%. The models developed provided improved estimations of actual PF based on the magnitude of the radiographical deformity.

Correlation of preoperative deformity magnitude and pulmonary function tests in adolescent idiopathic scoliosis

STUDY DESIGN

Clinical study correlating preoperative pulmonary function tests (PFTs) to radiographic measures of thoracic deformity severity in adolescent idiopathic scoliosis (AIS) patients.

OBJECTIVE

To determine (1) the incidence of clinically relevant (<65% predicted value) pulmonary impairment in AIS patients; (2) if patients with more severe deformity have greater impairment of PFTs than those with lesser deformity; (3) the effect, if any, of juvenile onset deformity (onset<age 10) on preoperative PFTs.

SUMMARY OF BACKGROUND DATA

Patients with late-onset (adolescent) spinal deformity are generally believed to have no respiratory morbidity except in severe curves exceeding 100°.

METHODS

A large multicenter database of surgically treated AIS patients with Lenke 1 to Lenke 4 curves was queried to report preoperative PFTs and correlate them with radiographic measures of coronal, sagittal, and axial plane deformities.

RESULTS

Nineteen percent of 858 patients had <65% predicted forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) before surgery, and had larger main thoracic (MT) curves and greater axial rotation than those with predicted PFT values>65%. Patients with MT curves>70°, and especially >80°; proximal thoracic (PT) curves which were >30° or structural; or T5-T12 kyphosis<10° had significantly (P≤0.001) lower FEV1 or FVC compared to those with less deformity. Axial plane deformity did not correlate with PFT impairment. Juvenile-onset patients had greater PFT impairment than AIS patients, along with slightly larger MT curves. Patients who were braced before surgery had worse PFTs than those had no treatment before surgery.

CONCLUSION

Preoperative PFTs are clinically impaired in 19% of AIS patients, and correlate significantly with the MT and sagittal plane deformity severity, and with PT curve severity to a lesser degree. PFTs do not correlate with degree of axial deformity. From a purely pulmonary standpoint, attention directed to coronal and sagittal plane deformity correction appears warranted, to address the specific deformities which are associated with PFT impairment.