Influence of acetabular dysplasia and associated radiological indicators on hip joint motion in asymptomatic individuals.

Abstract

Recent studies for acetabular dysplasia (AD) have revealed its complex morphology and biomechanical implications. In this context, range of motion (ROM) assessment could provide insight into early functional changes not captured by static imaging. This retrospective study aimed to determine whether radiographic features of AD are associated with alterations in passive ROM among asymptomatic individuals. Participants (200 hips from 100 asymptomatic Asian volunteers aged 18 to 50 years) underwent standardized physical and radiological examinations to assess passive hip ROM and AD. Passive ROM comparisons were made between AD and non-AD groups. Subgroup analyses for posterior signs and coxa profunda were performed within the AD group. Compared to the non-AD group (<i>n</i> = 148), the AD group (<i>n</i> = 52) demonstrated significantly greater passive ROM in forward flexion (FF), abduction, adduction, and external rotation (<i>P</i> < .05 for all), with FF independently associated with AD presence (OR, 1.06; 95% CI, 1.01-1.11). In the AD group, sharp angle positively correlated with FF, abduction, and internal rotation (IR). Subgroup analysis revealed that posterior sign was associated with reduced FF, while coxa profunda was linked to increased FF and IR. Multivariate analysis confirmed that FF and IR were independently associated with these morphological features. Additionally, participants with coxa profunda exhibited significantly higher sharp angles. Hips with AD demonstrated greater ROM compared to non-dysplastic hips, with sharp angle showing the strongest correlation with hip joint ROM. Subgroup analysis revealed distinct motion patterns: posterior sign was associated with reduced FF, while coxa profunda correlated with increased IR.