Can Surgery Be Proposed to Adolescent Idiopathic Scoliosis Patients With Structural Lumbar Curves Associated With Nonreducible Iliolumbar Angle?

Background: Lower instrumented vertebra (LIV) selection for adolescent idiopathic scoliosis (AIS) with structural lumbar curves (Lenke 3, 5, and 6) remains debated. The iliolumbar angle (ILA) measurement is useful for assessing the lumbosacral junction flexibility. If it is nonreducible, surgeons need to make a difficult choice between a potential "imperfect" L4, associated with a residual lumbosacral curve, or a more distal fusion performed later in life due to poorer functional outcomes. The goal of this study was, therefore, to evaluate the postoperative radiographic and functional outcomes of AIS patients with nonreducible ILA.

Methods: All consecutive AIS patients (2017 to 2022) with a structural lumbar curve and a posterior fusion ending on L4 were retrospectively included. Radiographic and functional outcomes (SRS-30 score) were reported with a minimum 2-year follow-up. Standing low dose stereoradiographs in both erect and maximum lateral bending positions were performed in all patients, and 2 groups of subjects were compared based on preoperative ILA flexibility [reducible group (R) or nonreducible group (NR)].

Results: A total of 122 patients were included (30% NR and 71% R). At a mean follow-up of 2.3±0.1 years, surgery was efficient in correcting the major curve (77% reduction rate in the R group and 76% in the NR group, P <10 -5 ), and significantly improved coronal balance (R, P <10 -5 and NR, P =0.03) as well as the ILA [mean ILA gain 14 degrees (R group), P <10 -5 and 16 degrees (NR group), P <10 -5 ]. The proportion of excellent results was higher in the R group, but 97% of outcomes were either excellent or acceptable in the NR group, and only 1 case of poor result (residual ILA >10 degrees) was reported in each group. No significant difference was found in SRS 30 scores between groups, but scores were significantly improved in the NR group for the excellent outcomes' subgroup [self-image ( P =0.04) and satisfaction ( P =0.02) domains].

Conclusions: The current study confirms that posterior fusion ending on L4 can still be proposed to young AIS patients with structural lumbar curves, even if the lumbosacral flexibility is limited.

Level of evidence: Level III-comparative study.