Prediction of respiratory function in patients with severe scoliosis on the basis of the novel individualized spino-pelvic index.

OBJECTIVE: Our study aimed to evaluate the pulmonary function of patients with severe scoliosis after correcting standing height with spino-pelvic index (SPI).
METHODS: Inclusion criteria: (1) with a coronal Cobb angle of more than 90°; (2) diagnosed as congenital (CS) or idiopathic scoliosis (IS); (3) aged between ten and 20 years; (4) with pulmonary function test (PFT) at the primary consultation. Patients with previous surgical intervention, with angular kyphosis, and with neuromuscular disease were excluded. Length of spine (LOS), height of spine (HOS), and height of pelvis (HOP) were measured on coronal films. SPI was defined as the ratio between LOS and HOP. The corrected body height was calculated: corrected body height = body height + (SPI × HOP - HOS). The PFTs included the following parameters: VCmax, FVC, FVC% predicted, FEV1, FEV1% predicted, PEF, and MVV. PFT results were recalculated using the corrected body height.
RESULTS: Thirty patients were diagnosed as IS and 27 as CS with average Cobb angles of 99.88° ± 11.83 and 98.06° ± 14.27, respectively. Significant differences were observed in VCmax and FVC between IS and CS patients (P < 0.05). All the corrected PFT parameters were significantly lower than the original PFT parameters (P < 0.05).
CONCLUSION: For the first time, this study proposed a method to predict pulmonary function of patients with severe scoliosis using SPI, as an age-independent parameter in normal adolescents. After body height correction, pulmonary function of patients with severe scoliosis was found to be significantly decreased, indicating that pulmonary function impairment was underestimated in patients with severe scoliosis when evaluating pulmonary function with arm span.