Triad of MR Arthrographic Findings in Patients with Cam-Type Femoroacetabular Impingement 1
Department of Radiology, Division of Musculoskeletal Radiology, Massachusetts General Hospital, 55 Fruit St, Yawkey Center, 6th Floor, Boston, MA 02114, USA. Radiology
(Impact Factor: 6.87).
09/2005; 236(2):588-92. DOI: 10.1148/radiol.2362041987
To retrospectively analyze magnetic resonance (MR) arthrographic findings in patients with clinical cam-type femoroacetabular impingement.
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.
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.
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.
Available from: Marco Hagen
- "The first choice of imaging diagnostics for FAI after clinical impingement tests and case history is an anteroposterior (AP) pelvic radiograph and a second lateral or oblique view. To quantify FAI, the alpha angle of Nötzli is described as an adequate parameter to analyse the degree of the disorder of the headneck junction  . The alpha angle is formed by the mid-axis of the femoral neck and the connecting line between the head of femur and the point first exceeding the radius of the cartilage-covered femoral head . "
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ABSTRACT: BACKGROUND: In the clinical evaluation of femoroacetabular impingement (FAI), there is a lack of quantitative, reliable and informative assessment methods for the overall functional capability of an individual. OBJECTIVE: We compared clinical and radiological measurements of the hip joint with a new methodology based on the concept of 3-dimensional reachable workspace using Microsoft Kinect. METHODS: We assessed the correlation between the alpha angle of Notzli on full-length radiographs and the clinical internal rotation. We evaluated the accuracy of joint positions and angles of the hip between the Kinect system and clinical examination including range of motion (ROM). RESULTS: The results of our clinical trial with 24 study participants showed a significant difference between normal internal rotation (> 21 degrees) and reduced internal rotation (<= 21 degrees) in comparison to the radiological alpha angle of Notzli (P = 0.026). The acquired reachable Kinect data demonstrated a moderate agreement between the Kinect and clinical examination (correlation coefficients between 0.230 and 0.375). CONCLUSIONS: The findings suggest that a higher grade alpha angle of Notzli accompanies reduced clinical internal rotation. The Kinect system provides reliable results of hip ROM. However, further test series must be performed for the application of Kinect in the clinical evaluation of FAI.
Available from: Matthias Lahner
- "The alpha angle was analyzed using the technique described by Nötzli . We considered an alpha angle >55° as cut-off value because an alpha angle >55° is associated with FAI . The alpha angle was subsequently measured by a radiologist (C.L.) and an orthopaedic surgeon (M.L.) both experienced in musculoskeletal imaging. "
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ABSTRACT: Femoroacetabular impingement (FAI) is predominant in young male athletes, but not much is known about gait differences in cases of increased hip alpha angles. In our study, the hip alpha angle of Notzli of soccer players was quantified on the basis of magnetic resonance imaging (MRI) with axial oblique sequences. The aim of the current study was to compare the rearfoot motion and plantar pressure in male semiprofessional soccer players with increased alpha angles to age-matched amateur soccer players.
In a prospective analysis, male semiprofessional and amateur soccer players had an MRI of the right hip to measure the alpha angle of Notzli. In a biomechanical laboratory setting, 14 of these participants in each group ran in two shoe conditions. Simultaneously in-shoe pressure distribution, tibial acceleration, and rearfoot motion measurements of the right foot were performed.
In the semiprofessional soccer group, the mean value of the alpha angle of group was 55.1 +/- 6.58[degree sign] (range 43.2-76.6[degree sign]) and 51.6 +/- 4.43[degree sign] (range 41.9-58.8[degree sign]) in the amateur group. In both shoe conditions, we found a significant difference between the two groups concerning the ground reaction forces, tibial acceleration, rearfoot motion and plantar pressure parameters (P < 0.01, P < 0.05, P = 0.04). Maximum rearfoot motion is about 22% lower in the semiprofessional group compared to the amateur group in both shoe conditions.
This study confirmed that semiprofessional soccer players with increased alpha angles showed differences in gait kinematics compared to the amateur group. These findings support the need for a screening program for competitive soccer players. In cases of a conspicuous gait analysis and symptomatic hip pain, FAI must be ruled out by further diagnostic tests.
Available from: Xiao guang Cheng
- "Leunig et al. reported a high prevalence of HPs in patients with FAI (39 of 117 hips) . The alpha angle is an important index for evaluating the contour of the femoral head–neck junction [10-12]. An alpha angle >50° may indicate a cam type of FAI . "
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ABSTRACT: Herniation pits (HPs) commonly develop over time at the femoral head--neck junction in adults, but their cause is still under debate. The purpose of study reported here was to investigate the correlation between the prevalence of HPs of the femoral neck and the alpha angle of the hips of healthy Chinese adults, by using computed tomography (CT).
Six hundred seventy Chinese adults (representing 1145 hips) who had no known diseases affecting the proximal femur and had no symptoms of femoroacetabular impingement underwent a 64-slice CT scan for medical purposes that included the hip in the scan range. Their CT data were analyzed for the prevalence of HPs in the femoral necks and for hip alpha angles.
The overall prevalence of femoral-neck HPs was 12.5% (143 of 1145 hips). The prevalence in the left versus right femoral necks was 12.1% (69 of 569 hips) versus 12.8% (74 of 576 hips). There was no statistically significant difference between the two sides (chi2 = 0.136; p = 0.712). The prevalence of HPs was greater in men than in women (15.9% vs 7.7%; p < 0.01) and greater in adults older than 30 years than in adults younger than 30 years (chi2= 14.547; p < 0.01). The alpha angles were greater in the 143 proximal femora with HPs than in the 1002 without pits (39.95[degree sign] +/- 6.01[degree sign] vs 37.97[degree sign] +/- 5.14[degree sign]; p < 0.01).
The prevalence of HPs of the femoral neck in healthy adults was 12.5%, and the prevalence was greater in men than in women. There is a correlation between the prevalence of HPs and the contour of the femoral head--neck junction. The formation of pits may be attributed to the combination of degeneration and morphologic variances in the femoral head--neck junction.
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