A Novel Model of Sacral Obliquity, Iliac Obliquity, and Hip Obliquity in Adolescent Idiopathic Scoliosis

Objective To propose and validate a novel model to explore the potential compensatory mechanism of sacral obliquity and pelvic obliquity in coronal balance. Summary of Background Data Sacral obliquity and pelvic obliquity are common phenomena in adolescent idiopathic scoliosis (AIS). However, their compensatory mechanisms in coronal balance remain unclear. Methods A total of 569 AIS patients were recruited. Coronal pelvic and lower limb parameters, including sacral obliquity (SO), iliac obliquity (IO), and hip obliquity (HO), were measured. Coronal spinal parameters, such as coronal distance (CD), clavicle angle (CA), thoracic curve (T), thoracolumbar/lumbar curve (TL/L), and tilt angle of L2∼L5, were measured. Correlation analysis was performed. Results The mean values of SO, IO, and HO were 3.34±2.81°, 1.40±2.04°, and 0.82±1.79°, respectively. The largest correlation coefficients with SO were L5 and IO (r=0.725, 0.701). The largest correlation coefficients with IO were SO and HO (r=0.701, 0.801). The largest correlation coefficients with HO were SO and IO (r=0.566, 0.801). Conclusion SO, IO, and HO have different implications for coronal balance, and their magnitude and direction can be deduced from the novel model. These parameters could be used to evaluate the compensation of the pelvis and lower limbs in AIS. In the coronal position, the pelvis and lower limbs extend the spinal sequence, similar to vertebrae and intervertebral discs. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The National Natural Science Foundation of China (82172392) ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Medical Ethics Committee of Chinese PLA General Hospital gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors.