Lowest instrumented vertebrae in early onset scoliosis: is there a role for a more selective approach?

Purpose: This purpose of this study was to assess the impact of patient and implant characteristics on LIV selection in ambulatory children with EOS and to assess the relationship between the touched vertebrae (TV), the last substantially touched vertebrae (LSTV), the stable vertebrae (SV), the sagittal stable vertebrae (SSV), and the LIV.

Methods: A multicenter pediatric spine database was queried for patients ages 2-10 years treated by growth friendly instrumentation with at least 2-year follow up. The relationship between the LIV and preoperative spinal height, curve magnitude, and implant type were assessed. The relationships between the TV, LSTV, SV, SSV, and the LIV were also evaluated.

Results: Overall, 281 patients met inclusion criteria. The LIV was at L3 or below in most patients with a lumbar LIV: L1 (9.2%), L2 (20.2%), L3 (40.9%), L4 (29.5%). Smaller T1 - T12 length was associated with more caudal LIV selection (p = 0.001). Larger curve magnitudes were similarly associated with more caudal LIV selection (p = < 0.0001). Implant type was not associated with LIV selection (p = 0.32) including MCGR actuator length (p = 0.829). The LIV was caudal to the TV in 78% of patients with a TV at L2 or above compared to only 17% of patients with a TV at L3 or below (p < 0.0001).

Conclusions: Most EOS patients have an LIV of L3 or below and display TV-LIV and LSTV-LIV incongruence. These findings suggest that at the end of treatment, EOS patients rarely have the potential for selective thoracic fusion. Further work is necessary to assess the potential for a more selective approach to LIV selection in EOS.

Level of evidence: III.