The Spinopelvic Geometry in Different Lenke Curve Types of Adolescent Idiopathic Scoliosis

The Lenke classification is well established in differentiation of curve types in adolescent idiopathic scoliosis (AIS) and guides selection of fusion levels. However, to date, it has neglected the spinopelvic parameters that have been associated with compensatory mechanisms in balancing the human erect posture and adjacent segment problems after spinal fusion. The aim of this study was to investigate spinopelvic parameters in different types of AIS curves.

Preoperative whole-spine radiographs from 100 patients with AIS were reviewed and the curves were classified according to Lenke. In addition, sagittal spinopelvic parameters (pelvic incidence, sacral slope, pelvic tilt) were measured and compared between different curve types and to normal population values.

The spinopelvic balance was not statistically distinguishable in different Lenke curve types. Slight differences of the spinopelvic balance, compared with normal population values, were found in AIS Lenke Type 5 and 6 curves (major curve at the lumbar/thoracolumbar region) with a pelvic incidence of 44° ± 8° (norm 49°), sacral slope of 34° ± 7° (norm 41°), and pelvic tilt of 10° ± 7° (norm 8°).

Overall, the variances of spinopelvic parameters in different AIS curve types do not seem statistically large enough for a potential clinical relevance. However, the sacrum is more verticalized in AIS curves with major curves located in the lumbar/thoracolumbar region. It remains to be investigated whether such a verticalized sacrum might be a compensatory mechanism to keep the whole spine balanced and if it reverses with correction of the scoliosis.