Sagittal spine length moderately correlates with pulmonary function for the timing of definitive fusion in growth-friendly graduates with early onset scoliosis

PURPOSE: Severe spinal curvature in early onset scoliosis (EOS) impairs pulmonary development and function. The treatment requires imaging to assess spine growth and pulmonary function. The purposes of this study were to determine if radiographic sagittal spinal length (SSL) correlates with pulmonary function testing (PFT) and to compare SSL with T1-T12 coronal height (CH) to guide definitive fusion in EOS patients.

METHODS: Growth-friendly graduate EOS patients who underwent definitive spinal fusion and had postoperative PFT data were identified in a multi-center database. CH and SSL measurements were obtained from upright radiographs. The PFT results were compared between these measurements, using the percentage of the expected PFT value based on age, sex, and height (arm span).

RESULTS: Forty-four patients were included. The average age at definitive fusion was 12.1 years (range, 10 to 15) at a mean of 5.6 years after the growth-friendly procedure. The diagnoses were idiopathic scoliosis (22/44, 50%), congenital scoliosis (12/44, 27%), syndromic scoliosis (8/44, 18%), and neuromuscular scoliosis (2/44, 5%). 37.2% of patients had moderate pulmonary dysfunction (FVCp < 60%). SSL and CH were strongly correlated (r = 0.770, p < 0.001). Predicted FEV1 and FVC had statistically significant moderate correlation with SSL (FEV1 r = 0.438, p = 0.002; FVC r = 0.450, p < 0.001), and weak correlation with CH (FEV1 r = 0.207, p = 0.091; FVC r = 0.282, p = 0.033).

CONCLUSION: SSL strongly correlated with traditional CH measurements, averaging 10 mm longer (p < 0.001). SSL had a stronger correlation with PFT than traditional CH, suggesting that, by considering the sagittal plane, SSL may provide a better indicator than CH for determining the timing of definitive fusion in EOS patients.