Radiographic signs associated with femoroacetabular impingement occur with high prevalence at all ages in a hospital population.

OBJECTIVES: Femoroacetabular impingement (FAI) is increasingly diagnosed clinically. Controversy exists about the significance of radiographic findings. Our goal is to determine the prevalence of radiographic FAI types and parameters in a hospital population clinically not suspected of having FAI. In addition we assessed whether pain, age and gender are associated with higher prevalences.
METHODS: Three hundred ten patients were included in this retrospective study. After applying the exclusion criteria, 262 patients (522 hips) remained. Two observers scored for radiographic parameters. A generalised estimation equation, Pearson's χ(2) test and logistic regression model were used.
RESULTS: Radiographic signs of FAI were absent in only 58 hips (11.1 %). In the 40 hips (7.7 %) with cam impingement, males were more affected (P < 0.001). In the 330 hips (63.2 %) with pincer impingement, females were more often affected (P < 0.001). In the 82 hips (15.7 %) with signs of mixed type impingement, male hips were significantly (P < 0.001) more often affected. Age had some effect on the prevalence of coxa vara, acetabular index and acetabular retroversion. No correlation with pain was found.
CONCLUSIONS: In this hospital population, signs occurred at a high rate. Radiographic parameters attributed to FAI are non-specific. Especially radiographic signs attributed to pincer type impingement have a high prevalence. KEY POINTS: • Femoroacetabular impingement is associated with an abnormal configuration of the hip joint. • The prevalence of femoroacetabular impingement parameters was high in our study population. • The diagnosis of femoroacetabular impingement should be made clinically.