Normative Relationships Between Spinopelvic Alignment and Femoroacetabular Orientation: A Cross-Sectional Study.

Study DesignCross-sectional study.ObjectivesNormative data describing the relationship between spinopelvic and femoroacetabular alignment is not thoroughly described in the literature; we aimed to explore potential associations in healthy young adults.MethodsVolunteers with no hip or spine pathology were recruited for this study (N = 395.) Full body EOS scans were used to obtain 3D reconstructions of participants' acetabula and femurs. Associations between femoroacetabular parameters (acetabular anteversion (AA), acetabular inclination (AI), femoral version (FV)) and spinopelvic parameters (pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL)) were tested using multiple linear regression analyses.ResultsWe included 395 healthy volunteers (mean age 28.90 ± 5.1; 57% female; mean BMI 24.8 ± 4.2). Linear regression analysis demonstrated that AA is associated with PI, PT, age, sex and weight (R² = 0.381). AI is largely conserved across participants, but associated with FV, PT, age, height and weight (R² = 0.0949).ConclusionWe identified that normative relationships exist between acetabular orientation and spinopelvic parameters; however there remains residual variability in AA that is not comprehensively predicted by spinopelvic parameters alone. This knowledge provides the foundation for understanding changing alignment with normal aging and compensatory mechanisms. This will ultimately help guide restoration of pre-degenerative acetabular orientation in THA and spinopelvic alignment in spinal fusion in order to optimize patient care and reduce the need for revision surgery.