The relationship of hip loading asymmetry and radiological parameters of the spine in Lenke type 1 idiopathic scoliosis.

BACKGROUND

Idiopathic scoliosis does not only cause structural changes in the spine, but also functional changes of the musculoskeletal system.

RESEARCH QUESTION

Does idiopathic scoliosis lead to asymmetric hip loading in severe Lenke type 1 deformity?

METHODS

23 patients (18 girls, 5 boys) aged 15 ± 2.8 years with an adolescent idiopathic main thoracic curve (Cobb angle 48.8°+/- 9.2°) were included. Measured X-ray parameters were: Cobb angle of primary thoracic and secondary lumbar curve, translation of the C7- plumb line, apical thoracic vertebra and apical lumbar vertebra from the central sacral vertical line. Subjects were examined by means of kinematic and kinetic gait analysis. The symmetry index (SI) was calculated as a ratio of hip frontal moments during a single stance for both sides when the symmetrical load was considered SI = 0 + /- 29.36 (0 +/- 1 SD of the mean SI of the healthy population). The Pearson correlation coefficient was used to show the relation between hip loading and radiologic measures of spinal deformity.

RESULTS

Only 34.8% of subjects with Lenke type 1 deformity showed symmetrical hip loading. Significant negative correlation was proved between SI and apical thoracic vertebra translation (R = - 0541; p < 0,05) as well as between SI and coronal imbalance (R = -0,5197; p < 0,05). There was no correlation between SI and the magnitude of the primary thoracic curve (R = -0.19; p = 0.385). Coronal imbalance correlates positively with translation of apical thoracic vertebra (R = 0,7255; p < 0,05).

SIGNIFICANCE

Two-thirds of subjects with Lenke type 1 deformity showed asymmetrical hip loading. This asymmetry is related to the translation of the apical thoracic vertebra and coronal imbalance and is not related to the magnitude of the main thoracic curve. On the contrary, the secondary lumbar curve plays role in the compensatory mechanism of the trunk.