Objective  To evaluate the severity and features of pelvic coronal plane tilt in individuals with adolescent idiopathic scoliosis (AIS) who had lumbar curvature during the gait cycle.

  Methods  AIS patients with lumbar curvature and patients with microcurvature (Cobb Angle less than 10 degrees) treated in Peking Union Medical College Hospital from September 2020 to February 2023 were retrospectively included. According to PUMC conservative classification system and Spinal Full-length Standing X-ray, AIS patients with lumbar curvature were enrolled. The bilateral iliac crest was used as the bony marker of the pelvic coronal surface, and the bilateral iliac crest height and its changes were measured during the standing position and walking cycle, so as to evaluate the degree of pelvic coronal tilt in AIS patients with lumbar curvature.

  Results  A total of 209 AIS patients with lumbar curvature and 36 patients with microcurvature who met the inclusion and exclusion criteria were enrolled. The proportion of AIS patients with lumbar curvature who had a "congruent" relationship between the higher iliac crest and the convex side of the spine in standing position (iliac crest lower on the convex side than on the concave side) was significantly higher in AIS patients with lumbar curvature than patients with microcurvature(58.9% vs. 30.6%, P=0.002). AIS patients with lumbar curvature had statistically different bilateral iliac crest height change values throughout the gait cycle (including minimum, maximum, swing phase minimum, and swing phase maximum) (all P < 0.001), and the iliac crest height change values on the convex side were significantly higher than those on the concave side (all P < 0.05), whereas the patients with microcurvature did not have any statistically significant bilateral iliac crest height change values throughout the gait cycle (all P > 0.05).

  Conclusion  The height of the iliac crest on the convex side of the lumbar spine is lower than that on the concave side in the standing position of AIS patients with lumbar curvature, and the value of the change of the iliac crest on the convex side of the pelvis is greater than that on the concave side in walking to maintain the balance of the body, which may provide a new direction for the intervention in the clinical rehabilitation treatment of AIS patients with lumbar curvature.