False profile view can help identify cam lesions in patients with FAI
CHICAGO — The false profile radiographic view can be used to effectively characterize cam lesions in the femoral head-neck junction for the diagnosis and treatment of cam-type femoroacetabular impingement, according to a presenter here at the American Orthopaedic Society for Sports Medicine Annual Meeting.
“The false profile view when used with the pelvic AP and 90° Dunn lateral has an excellent sensitivity and specificity for identifying cam lesions and should be used as a screening tool for femoroacetabular impingement,” Michael D. Hellman, MD, said. “The false profile view mainly looks at that 3 o’clock to 2 o’clock position, so the far anterior side the femoral head-neck junction.”
Michael D. Hellman
The objective of the study was to verify the accuracy of the false profile radiographic view compared to 3-D CT findings. The researchers retrospectively reviewed the preoperative radial oblique reformatted CT scans and plain radiographs of 45 patients (24 women and 21 men) who underwent hip arthroscopy between January 2011 and September 2012 at Rush University Medical Center. There were 32 right hips and 13 left hips. Average patient age was 35 years. Two physicians independently measured alpha angles on plain radiographs (AP, Dunn and false profile view), and alpha angles greater than 55° were considered abnormal.
Overall, the researchers found that 32 hips had a cam lesion on reformatted CT and 31 hips had a cam lesion present about the 2 o’clock position of the femoral head-neck junction. In addition, 19 hips had a cam lesion present about the 3 o’clock position of the femoral head-neck junction.
“For the false profile view, the sensitivity was about 60% and the specificity was 89%, so not quite there for a good screening radiograph. But if you combine all three views, the sensitivity went up to 86% and the specificity stayed fairly high at 75%,” he said.
Hellman and colleagues found 76% agreement when reviewers compared the false profile radiographic views with the 2 o’clock view and 83% agreement when they compared the false profile radiographic view with the 3’ o’clock view. Interobserver and intraobserver correlation coefficients were 0.81 and 0.88, respectively, he said.
“The false profile view should be used as a screening radiograph because you can both access both the acetabulum. You get a nice lateral view of the acetabulum so you can see the anterior coverage, and also you can assess the femoral head-neck junction,” Hellman said.
Hellman MD. Paper #7. Presented at the: American Orthopaedic Society for Sports Medicine Annual Meeting; July 11-14, 2013; Chicago.
Disclosure: Hellman has no relevant financial disclosures.