The prevalence of femoroacetabular impingement in radiographs of asymptomatic subjects: a cross-sectional study

Background: There is a lack of uniformity in the diagnostic criteria for femoroacetabular impingement (FAI), and few studies discuss the prevalence of radiographic changes in asymptomatic individuals. These factors make it difficult to establish a natural history of this disease. The aim of this study was to assess the prevalence of radiographic signs of CAM and Pincer FAI in an asymptomatic population. Methods: A cross-sectional study was performed from July 2013 to December 2013. A total of 185 subjects were analysed. Inclusion criteria: no history of hip pain or orthopedic disease; and being 20-60 years old. Exclusion criteria: athletically active; or patients who would not allow acquisition of appropriate radiographs for analysis. Radiographs were obtained in anteroposterior and Dunn 45 degrees view to access: alpha angle (AA), triangular index (TI), crossover sign (CS), lateral-centre edge (LCE) angle and acetabular index (AI). Results: Median age was 34 years (27-49.5) and FAI was present in 53% of all subjects. 32.44% (60) was the overall CAM-type prevalence and 42.7% (79) the overall Pincer-type prevalence. Only 2 subjects presented the 3 overcoverage signs (AI, LCE and CS). An association was noted between the presence of AI <0 degrees and the LCE >40 degrees (p = 0.05). Conclusions: Our study established a higher prevalence of radiographic markers of FAI in an asymptomatic population.