Radiological assessment of femoroacetabular impingement morphology using computed tomography in an asymptomatic young population

Abstract

Background: Femoroacetabular impingement (FAI) is one cause of hip pain, and is an under-recognized cause of early osteoarthritis, especially in young and active people. The prevalence of FAI in adults is approximately 10 – 15% and depending on the clinical and radiographic findings, two types of impingement (which are often present in combination) can be distinguished: the cam type and the pincer type. Most patients (86%) have a combination of both forms of impingement. Objectives: The aim of our study was to evaluate the prevalence and gender differences in the radiological parameters associated with cam and pincer FAI morphologies in an asymptomatic young population, using computed tomography (CT). Patients and Methods: A retrospective study was performed on 200 individuals (400 hip joints), ranging from 15 - 40 years of age, who were seen in our hospital between July of 2013 and April of 2014 for nonspecific abdominal pain. Multiplanar reformatted CT images of these patients were assessed for the existence of radiological abnormalities, and six measurements (acetabular version angle, acetabular index, lateral center-edge angle, alpha angle in the oblique axial plane, alpha angle in the radial [one o’clock position] plane, and femoral head neck offset) were made relating to the FAI. Results: The data showed that 69.2% of the women’s joints and 60.5% of the men’s joints had at least one abnormal parameter associated with the FAI. Of the joints, 34.25% had two or more abnormal parameters, and in 38 (19%) of the patients, these abnormalities were bilateral. Unlike previous studies, we found that only 15% of the joints had mixed FAI morphologies. Conclusion: The prevalence of radiological parameters associated with FAI is high, even in an asymptomatic young population. This high frequency of features may suggest that the threshold values have been set too low in the current literature, or that these findings may reflect anatomical variation rather than true pathological abnormalities.