Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement.
OBJECTIVE
To retrospectively analyze magnetic resonance (MR) arthrographic findings in patients with clinical cam-type femoroacetabular impingement.


METHODS
This study was approved by the institutional review board, and informed consent was waived. Study was compliant with the Health Insurance Portability and Accountability Act. Forty-two MR arthrograms obtained in 40 patients with clinical femoroacetabular impingement were analyzed retrospectively by two radiologists. Quantitative analysis by using alpha angle measurement was performed to assess anterosuperior femoral head-neck morphology. Presence of labral tears, articular cartilage lesions, paralabral cysts, os acetabuli, and synovial herniation pits was recorded. Presence of the typical triad of anterosuperior labral tear, anterosuperior cartilage lesion, and abnormal alpha angle was recorded. Surgical comparison was available for 11 patients.


RESULTS
At imaging, in 40 patients (22 male, 18 female) with a mean age of 36.5 years, 39 of 42 hips (93%) had an abnormal alpha angle, with a mean angle of 69.7 degrees ; 40 of 42 (95%) had an anterosuperior cartilage abnormality; and 42 of 42 (100%) had an anterosuperior labral tear. Thirty-seven of 42 hips (88%) had the triad. Six had paralabral cysts, 17 had an os acetabuli, and two had synovial herniation pits. Surgical comparison for 11 hips led to confirmation of all labral and cartilage abnormalities seen at imaging.


CONCLUSIONS
MR arthrography demonstrated a triad of abnormal head-neck morphology, anterosuperior cartilage abnormality, and anterosuperior labral abnormality in 37 of 42 patients with cam-type femoroacetabular impingement.
Department of Radiology, Division of Musculoskeletal Radiology, Massachusetts General Hospital, 55 Fruit St, Yawkey Center, 6th Floor, Boston, MA 02114, USA. akassarjian@partners.org
Ara
A
Kassarjian
Luke S
LS
Yoon
Etienne
E
Belzile
Susan A
SA
Connolly
Michael B
MB
Millis
William E
WE
Palmer
D000077:Acetabulum; D000293:Adolescent; D000328:Adult; D000368:Aged; D001175:Arthrography / Q000379:methods*; D005260:Female; D005269:Femur; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D007592:Joint Diseases / Q000145:classification / Q000175:diagnosis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies