Background: Patients with scoliosis present gait impairments compared to healthy subjects. Clinically, spine deformity is evaluated with Cobb angle, a standard measurement to determine and track the progression of scoliosis. Scoliosis is a biomechanical trouble, dependant of external forces and muscular activity. External work is currently analyzed in patients with scoliosis because this work sums up consequences and evolutions of spine deformity. Habitually, biomechanics approach is used to compute this work. For asymptomatic subjects, a regression model let to compute external work. So, considering the area of research to facilitate the follow-up at lower cost, this regression function could be applied to patients with scoliosis but need to be validated.

Research question: can external work during walking in scoliosis patients be estimated from spatiotemporal parameters with a regression model?

Method: This retrospective study included twenty untreated patients with idiopathic scoliosis and sixteen asymptomatic participants. We used a regression model defined in case of asymptomatic subjects in literature and proposed a new specific model in case of patients with scoliosis.

Findings: The external work in patients with scoliosis calculated with the Wirta's regression eq. (0.23 ± 0.04 J.kg^-1.m^-1) was underestimated compared to the external work calculated using a biomechanical method (0.33 ± 0.06 J.kg^-1.m^-1). A new regression model including Cobb angle and spatio-temporal parameter presents a high coefficient of determination.

Interpretation: In opposition to biomechanical method, our new model let to compute external work without expensive gait laboratory. This specific model is more reliable than the model developed from asymptomatic subjects.