ABSTRACT
Femoroacetabular impingement secondary to the cam effect is thought to be associated with an insufficient anterior concavity in the sagittal/axial plane of the femoral head-neck junction. Using three-dimensional computed tomography the anterior and posterior concavity of the femoral head-neck junction was assessed in 36 painful non-dysplastic hips (30 patients). The mean age of the symptomatic hips was 40.7 with 13 females and 17 males. Eighteen out of the 36 hips had a pistol grip deformity. Magnetic resonance gadolinium arthrography was performed to assess for labral and cartilage lesions. Alpha and beta angles measuring the anterior and posterior femoral head-neck junction concavities were also determined in 20 asymptomatic hips (12 patients; mean age 37, 5 females and 7 males) using three-dimensional computed tomography. The mean alpha angle for the symptomatic and the control group were: 66.4 versus 43.8 (p=0.001), and for the beta angle 40.2 versus 43.8 (p=0.011), respectively. All but one of the symptomatic hips had a labral tear with 61% of these hips having associated cartilage damage. Three-dimensional computed tomography represents an accurate tool to quantify the femoral head-neck concavity providing a non-invasive assessment of hips at risk of femoroacetabular impingement.
