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Multicenter Study
. 2021 Nov;9(6):1569-1579.
doi: 10.1007/s43390-021-00382-8. Epub 2021 Jul 3.

Defining risk factors for adding-on in Lenke 1 and 2 AR curves

Brendon C Mitchell  1 , David L Skaggs  2 , Lawrence G Lenke  3 , Tracey P Bastrom  4 , Carrie E Bartley  4 , Peter O Newton  5   6   7
Affiliations
Multicenter Study

Defining risk factors for adding-on in Lenke 1 and 2 AR curves

Brendon C Mitchell et al. Spine Deform. 2021 Nov.

Abstract

Purpose: To identify curve/correction characteristics associated with adding-on at 2 years after posterior spinal fusion (PSF) in Lenke 1/2 AR curves.

Methods: A prospective multicenter registry was queried to identify patients with adolescent idiopathic scoliosis (AIS), Lenke 1/2 AR curves, who underwent PSF with a minimum of 2-year follow-up. Patient characteristics as well as pre- and post- operative radiographic variables were evaluated using Classification and Regression Tree (CART) analysis to determine which factors contribute to adding-on.

Results: 253 patients treated with PSF were assessed for adding-on, of which 50 met our adding-on criteria. Univariate analysis revealed adding-on was associated several factors including: post-operative thoracic and lumbar curve magnitude (p > 0.001), first erect (FE) end instrumented vertebra (EIV) angulation (p = 0.009) and EIV translation (p = 0.001), younger age (p = 0.027), Risser stage (p = 0.024), and a more proximal lowest instrumented vertebra (LIV) (p < 0.001). Multivariate CART analysis showed the chance of adding-on was more than 2 times greater (42 vs 16%) when the chosen LIV was translated more than 2.7 cm from the CSVL. When the LIV was within 2.7 cm, the post-op risk of adding-on was increased when the LIV was not perfectly leveled (> 0.5°).

Conclusion: In Lenke 1 and 2 AR curves, pre-operative LIV translation appears to be an independent risk factor for adding-on; and in those with < 2.7 cm of LIV translation, FE LIV angulation also seems to increase the risk of adding-on. These factors are relevant in determining appropriate LIV selection and aid in identifying patients at risk for developing adding-on.

Keywords: Adding-on; Adolescent idiopathic scoliosis; Central sacral vertical line; Lowest instrumented vertebra; Posterior spinal fusion.

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References

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