TP3.3 Lateral Center-Edge Angle Measurements on Computed Tomography Are Higher Compared To Measurements On Plain Radiograph But Alpha Angle and Tönnis Angle Are Similar: A Systematic Review and Meta-Analysis

Abstract

Abstract Introduction Radiographic evaluation is central to the assessment of femoroacetabular impingement and acetabular dysplasia, with key parameters including the lateral center-edge angle (LCEA) and Tönnis angle (TA) for acetabular coverage and the alpha angle (AA) for cam morphology. This purpose of this systematic review was to evaluate studies comparing plain radiography (XR) and computed tomography (CT) measurements of LCEA, AA, and TA in hip preservation patients. Methods A systematic review was conducted in October 2025 in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and Scopus databases. Studies comparing CT and plain radiography measurements of hip preservation parameters were included. Meta-analysis was performed where applicable; heterogeneity was assessed using I2 statistics. P<0.05 was considered statistically significant. Results Twelve studies comprising 1,188 hips (1,008 patients) met inclusion criteria. The cohort was predominantly female (70.7%), with mean ages ranging from 25 to 39 years. XR measurements of LCEA were significantly lower than CT in four of six studies (range: −9.14° to +1.3°). AA differences ranged from −6.49° to +11.4°, with three of five studies reporting significantly higher values on XR and one reporting the inverse. TA differences ranged from −2.60° to +3.92° with inconsistent directionality. Interobserver reliability was excellent (Intraclass coefficient (ICC) > 0.75) for LCEA and TA on both modalities, while AA demonstrated greater variability across studies (ICC 0.09–0.929 for CT, 0.43–0.89 for XR). Meta-analysis demonstrated that LCEA was underestimated on XR relative to CT (SMD 0.34, 95% CI 0.08–0.61, p = 0.01), while AA and TA showed no significant differences. Heterogeneity was substantial (I2=79–83%). Conclusion LCEA measurements were consistently lower on XR than CT. AA differences were inconsistent and largely view-dependent; insufficient TA data precluded any conclusion. Reliability was excellent for LCEA and TA but more variable for AA. Significance/Clinical Relevance These findings suggest that LCEA measurements on XR underestimate acetabular coverage relative to CT, potentially overestimating the degree of acetabular dysplasia.