Introduction: Leg discrepancy is known as a symptomatic skeletal asymmetric in scoliosis. We hypothesized that leg discrepancy is correlated to the pelvic frontal alignment which in turn is correlated to the entire spinal deformities.
Objective: To investigate the correlation between leg discrepancy, pelvic alignment and spinal parameters in AIS.
Methods: Three-dimensional reconstructions of the spine and pelvis of 80 adolescents with right main thoracic (MT, Lenke1), 80 with left thoracolumbarlumbar (TL/L, Lenke 5) idiopathic scoliosis and 36 asymptomatic control subjects were included in this study. Also 4 anatomical landmarks on the pelvis (contralateral ASIS and PSIS) and two femoral heads were selected to define pelvic alignment i.e. pelvic tilt in the coronal plane and pelvic rotation in the transverse plane and leg discrepancy in subjects.
Results: The 160 subjects were classified in four classes (PC1 to PC4) based on the pelvic transverse and coronal planes orientation. A majority of Lenke1 subjects had their pelvis rotated towards the major carve (58% in the frontal and 84% in the transverse plane). 72% of Lenke 5 subjects had their pelvis tilted in the coronal plane towards the thoracolumbar curve while the pelvis rotation tends to be more affected by the direction of the main thoracic curve (70% of subjects)(Fig 1). Pelvic frontal tilt (Obliquity) found to be correlated to the leg discrepancy in Lenke1 (r=0.70) and Lenke5 (r=0.80) p<0.001. 91% of the controls had pelvic tilted counter clockwise in the posterior view and less than 4° ccw pelvic axial rotation.
Conclusion: The findings suggest that pelvic rotation is more affected by the direction of main thoracic rotation while pelvis aligns itself towards the direction of the major curve i.e. thoracic in Lenke 1 and lumbar in Lenke 5 in the frontal plane and is correlated to the lower limb discrepancy.