140. SAGITTAL CORRECTION OF IDIOPATHIC SCOLIOSIS BY IN SITU CONTOURNAGE

Abstract

Purpose of the study: The in situ contournage technique can be used to correct the 3D spinal deformity resulting from scoliosis; the manoeuvres enable rotational corrections, medialisation, and kyphosis and lordosis of strategic segments of the spine. A preliminary study identified a prolonged zone of thoracolumbar sagittal rectitude in thoracic, double major and lumbar scoliosis, indicating the vertebrae with the maximal rotation and the zones of hypokyphosis and hypolordosis. The purpose of the present study was to analyse the correction and sagittal balance of these segments after in situ contournage.

Material and methods: The pre- and postoperative radiographs of 54 patients (48 female, 6 male, mean age 21 years, mean follow-up 8 years) with idiopathic scoliosis (36–104) were analysed with Spineview. The types of curvatures, the levels included in the sagittal rectitude and the vertebrae with the maximal rotation were determined. The kyphosis was measured on T4-T12, T4-T8 and T9-T12. Lordosis was measured on L1-S1, T12-L2, L3-S1. Tilt on T1 and T9 and sacral slop as well as pelvic version and incidence were determined.

Results: Three characteristic configurations were analysed: thoracic curvature with sagittal rectitude T8-L1 and maximal rotation at T7-T8, double major curvatures with sagittal rectitude T9-L2 and maximal rotation at T8-T9 and L2-L3, and lumbar curvatures with sagittal rectitude T12-L4 and maximal rotation at L1-L2. After posterior instrumentation, the T4-T12 hyperkyphosis decreased on average from 24.1 to 17.4° (p=0.0001) and the T9-T12 hypokyphosis increased from 3.6 to 8.6° (p=0.0001) for the thoracic and double major curvatures. The T12-L2 hyperlordosis increased from 6.6 to 10.3° (p=0.027) and the L3-S1 lordosis decreased from 42.1 to 38.9° (p=0.463) in the lumbar and double major curvatures. Tilts, sacral slope, and pelvic version and incidence did not vary significantly.

Conclusion: The prolonged thoracolumbar sagittal rectitude exhibits three distinctive configurations. Each configuration indicates the level of maximal rotation at the superior or inferior end. It enables a decomposition of the overall thoracic kyphosis into a superior segment of hyperkyphosis and an inferior segment of hypokphosis and to identify a zone of superior lumbar hypolordosis. In situ contournage corrects the vertebral rotation, the kyphosis and the lordosis and acts on the strategic vertebrae. The rectitude can be used to better identify the zones requiring correction in order to optimise the balance between the thoracic kyphosis and the lumbar lordosis while improving vertebral rotation by traction or compression.