The Role of Sole Lift in Treating Pediatric Idiopathic Scoliosis with Mild Thoracolumbar/Lumbar Curve

Objective: Lower limb discrepancy (LLD) was frequently observed in patients with idiopathic scoliosis (IS), potentially associated with etiopathogenesis. Although sole lifts had been proposed as a conservative treatment for IS, evidence supporting their efficacy was limited. This study aimed to assess the effects of sole lift intervention on pediatric patients with mild IS, specifically focusing on thoracolumbar/lumbar (TL/L) curvature.

Methods: Twenty patients, with an average age of 12.3 ± 3.1 years and presenting mild TL/L curve (15.6° ± 6.2°), were selected from a pool of 267 pediatric IS patients in the outpatient of our spine center from February 2023 to August 2023. Inclusion criteria comprised a main TL/L curve ranging between 10° and 40°, the lower limb positioned at the convexity of the main curve, and LLD of less than 2 cm; individuals requiring bracing or surgical intervention were excluded. Custom sole lifts were used to address the shorter lower limb with the objective of leveling the pelvis. Radiographic evaluations were conducted both before and after intervention using standing full spine posteroanterior radiographs and full leg length radiographs. Statistical analysis was undertaken to evaluate curve correction and its associations with other influencing factors.

Results: The mean structural and functional LLD were 7.1 ± 4.5 mm and 7.1 ± 4.1 mm, respectively. Among the 20 patients, four exhibited structural LLD greater than 10 mm. The average follow-up duration was 6.4 ± 1.9 months (range: 3-8 months). Following sole lift intervention (7.0 ± 3.0 mm), a significant reduction was observed in the TL/L curve compared to the pre-sole lifting measurements (15.6° ± 6.2° vs. 12.1° ± 7.2°, p < 0.001), as well as a notable decrease in the thoracic curve (12.2° ± 4.0° vs. 8.6° ± 6.3°, p = 0.064). Nine patients experienced a significant curve reduction of ≥5°, while eight showed a reduction between 0° and 5°; however, two patients exhibited no change in curve magnitude. Furthermore, the correction rate of the TL/L curve correlated significantly with functional LLD (r = -0.484, p = 0.030) and pelvic obliquity (r = -0.556, p = 0.011), highlighting the active pelvic compensation in maintaining balance between the spine and lower limbs. Conversely, no significant correlation was observed between curve correction and structural LLD (p > 0.05). Additionally, even after adjusting for other influencing factors, the TL/L Cobb angle remained significantly different between pre- and post-sole lifting (p = 0.037).

Conclusion: This study confirmed the effectiveness of sole lift intervention in correcting TL/L and thoracic curves among the mild IS children with a main TL/L curve, providing a supplementary conservative treatment option for patients with the lower limb at the convexity of the main curve. Moreover, our findings underscored the active compensation of the lower limbs and the pelvis in the etiopathogenesis of IS, highlighting the importance of considering their influence in treatment strategies.