Measuring the osteochondral connection of the femoral head and neck in patients with impingement femoroacetabulare by determining the angle of two alpha in lateral and anteroposterior hip radiographic images

Abstract

Femoroacetabular impingement, a pathophysiological mechanism of small morphological changes of the hip leads to early arthritic changes. The aim of this study was to present a simple method for the quantification of femoral head and neck junction in patients with cam form of femoroacetabular impingement, in standardized anteroposterior and profile DUNN 90 radiograms of the hips. In standardized anteroposterior and profile DUNN 90 images of the hips we determined the angle of 2 alpha, defined by our own original method. We tested 141 hips in 81 patients without clinical signs of femoroacetabular impingement, and 153 hips in 76 patients with clinically clear signs of femoroacetabular impingement. The value of the angle 2 alpha in anteroposterior hip radiograms was on average 113.7 degrees for the patients with clinical symptoms of impingement, and 84.2 degrees for the control group of patients (p < or = 0.0001), and in DUNN 90 profile radiography of the hip, the value of 2 alpha angle in the patients group was 97.2 degrees, and 74.6 degrees in the control group (p < or = 0.0001). The proposed method of determining the angle 2 alpha showed a high level sensitivity (97.8%) and specificity (98.7) and positive predictive value (98.6%). It was false positive in only 1.3%, and false negative in 2.12% of patients. Using standardized anteroposterior and profile radiographs of the hips, and without determination of femoral neck axis in patients with femoroacetabular impingement with the cam effect at the junction of the femoral head and neck, we proposed the method of measuring joint abnormalities of femoral head and neck junction, very capable to predict the disease development in an asymptomatic risk group of patients and high sensitive in the diagnosis of the disease in the group of patients.