Preoperative LIV Tilt Affects Post Operative Coronal Imbalance in Patients with Lenke 5C Scoliosis

Introduction Lenke 5C curves are increasingly being treated through posterior pedicle screw based correction techniques. We evaluated different preoperative radiological parameters which could affect post operative coronal imbalance (POCI) in patients with Lenke 5C scoliosis treated with posterior instrumented correction. Methods We retrospectively evaluaed twenty-three cases with Lenke 5C scoliosis who underwent selective posterior pedicle screw based deformity correction. Fusion was performed from proximal neutral to distal stable vertebra. Preoperative, immediate post operative and final whole spine standing radiographs were analyzed. The pre-operavtive radiological parameters were assessed including lower instrumented vertebra(LIV) tilt and translation, Cobb angle,C7 offset from CSVL, lumbar lordosis and upper instrumented vertebra(UIV) tilt and translation. Post-operatively we assessed the correction in cobb angle and post-operative coronal imbalance. Results Twenty -three patients had a mean age: 11.8 ± 4.6 years, with 4 males and 19 females. There was a significant improvement in Cobb angle from mean of 55 ± 13.3° to mean of 14.7 ± 8.8°. Nineteen patients had lower instrumented vertebra at L4, 3 at L3 and one at L5. Correction was maintained with no significant loss in the late post op period (15.2 ±8.9 degrees). The mean pre op C7-CSVL distance was 24.7 mm While eight patients had immediate post operative coronal imbalance (POCI), six of them balanced at a mean 8.2 months. Four patients had POCI at the time of final follow-up including two, who developed late imbalance. POCI correlated with pre operative LIV tilt only > 25° ( p < 0.05) and not with LIV translation, UIV tilt or translation. Five of the eight patients with immediate POCI and all four patients with late POCI had preoperative LIV tilt > 25°. Conclusion In Lenke 5C scoliosis treated by posterior pedicle screw instrumentation, patients with a preoperative LIV tilt (>25°) have a risk of developing POCI.