Michael D Hellman1, Randy Mascarenhas2, Anil Gupta2, Yale Fillingham2, Bryan D Haughom2, Michael J Salata3, Shane J Nho2. 1. Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.. Electronic address: mdhellman@gmail.com. 2. Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A. 3. Department of Orthopedic Surgery, University Hospitals Case Medical Center, Cleveland, Ohio, U.S.A.
Abstract
PURPOSE: To identify the accuracy of measuring the alpha angle on the false-profile, anteroposterior (AP), and 90° Dunn lateral views of the hip as compared with computed tomography (CT) scan findings. METHODS: Forty patients were needed to have power greater than 80%. Forty-five consecutive patients undergoing hip arthroscopy were retrospectively reviewed with preoperative radial oblique CT reformatted scans and plain radiographs. Alpha angles were measured on plain radiographs (AP, 90° Dunn lateral, and false profile) and CT reformatted views. Abnormal alpha angles were considered greater than 50.5°. Two orthopaedic surgeons independently measured the images, and the results were compared between imaging modalities. RESULTS: The false-profile view was 60% sensitive and 89.0% specific for diagnosing cam deformities of the hip. All radiographs combined were 86% sensitive and 75% specific for diagnosing cam deformities. The false-profile view most strongly correlated with the 2-o'clock (R = 0.746, P = .001) and 3-o'clock (R = 0.698, P < .0001) positions. An intraclass correlation coefficient of 0.81 was found for measurement of the alpha angle on the false-profile view. CONCLUSIONS: This study has proved that the false-profile view effectively characterizes cam deformity, especially anterior deformity at the 3-o'clock position. Measuring the alpha angle on the false-profile view appears to be reproducible. The false-profile view along with standing AP pelvis and 90° Dunn lateral views of the hip comprises a good screening radiographic series for patients presenting with symptoms of femoroacetabular impingement. LEVEL OF EVIDENCE: Level III, diagnostic study.
PURPOSE: To identify the accuracy of measuring the alpha angle on the false-profile, anteroposterior (AP), and 90° Dunn lateral views of the hip as compared with computed tomography (CT) scan findings. METHODS: Forty patients were needed to have power greater than 80%. Forty-five consecutive patients undergoing hip arthroscopy were retrospectively reviewed with preoperative radial oblique CT reformatted scans and plain radiographs. Alpha angles were measured on plain radiographs (AP, 90° Dunn lateral, and false profile) and CT reformatted views. Abnormal alpha angles were considered greater than 50.5°. Two orthopaedic surgeons independently measured the images, and the results were compared between imaging modalities. RESULTS: The false-profile view was 60% sensitive and 89.0% specific for diagnosing camdeformities of the hip. All radiographs combined were 86% sensitive and 75% specific for diagnosing camdeformities. The false-profile view most strongly correlated with the 2-o'clock (R = 0.746, P = .001) and 3-o'clock (R = 0.698, P < .0001) positions. An intraclass correlation coefficient of 0.81 was found for measurement of the alpha angle on the false-profile view. CONCLUSIONS: This study has proved that the false-profile view effectively characterizes camdeformity, especially anterior deformity at the 3-o'clock position. Measuring the alpha angle on the false-profile view appears to be reproducible. The false-profile view along with standing AP pelvis and 90° Dunn lateral views of the hip comprises a good screening radiographic series for patients presenting with symptoms of femoroacetabular impingement. LEVEL OF EVIDENCE: Level III, diagnostic study.
Authors: Steffen J Haider; Alan H Siegel; Kevin F Spratt; James B Ames; J Allen Graham; Yvonne Y Cheung Journal: Skeletal Radiol Date: 2017-11-06 Impact factor: 2.199