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Chiropractic Journal of Australia : CJA September 2012
Chiropractic Journal of Australia Volume 42 Number 3 September 2012 93 Physical Examination The gait pattern of a patient with FAI may reveal a positive Trendelenburg sign (hip abductor weakness during the stance phase of gait).6,7,19 Passive range of motion of the affected hip is restricted, and often painful, in fexion, internal rotation and adduction, which is unlike the global restriction of motion found in advanced cases of DJD.7,12,14 Internal rotation with the hip in 90° of fexion is markedly limited in comparison to the other side.19 Possibly the most important clinical fnding indicative of FAI, is a positive impingement test (impingement sign).19 It has been demonstrated that in patients with a positive impingement test, there is a signifcant association with labral pathology.20 The anterior hip impingement test is performed with the patient in a supine position (Figure 2). The hip is internally rotated and adducted, as it is passively fexed to 90°.12,14 A reproduction of the patients symptoms is considered a positive sign.12,14 The anterior impingement test results in contact between the junction of the femoral head-neck and acetabular rim which cause pain where there is a labral or chondral lesion.14 The Log roll test, FABERE test and other provocative maneuvers may also be positive, but are nonspecifc for FAI.21 Radiographic Features Radiographic examination for FAI includes an anteroposterior (AP) pelvic view, and a lateral hip view on both sides. It is benefcial to use 10-15° of hip internal rotation on the AP pelvic view to compensate for femoral anteversion, providing optimal visualisation of a Cam lesion.13 Additional radiographs include an axial cross-table lateral view, frog-leg lateral view, and a false-profle view.7,12 All lateral views should be obtained bilaterally for the purpose of comparison.3 The AP pelvic radiograph provides visualisation of the contour of the lateral femoral head-neck junction, and should be routinely evaluated for the Cam lesion (pistol-grip or tilt deformity; Figure 3), acetabular protrusion, acetabular retroversion, and/or the pincer lesion (excessive arching of the acetabular roof; Figure 3).3,7 The lateral hip view will allow visualization of subchondral sclerosis and early subchondral cyst formation within the anterior acetabular rim, as well as joint space narrowing and acetabular over-coverage of the femoral head (Figure 4).13 FAI can be further quantifed on the lateral hip view, through measurement of the alpha angle (Figure 5A, 5B). A line is drawn along the axis of the femoral neck, and a second line drawn from the centre of the femoral head through the femoral head-neck junction.7,12 It has been concluded that an alpha angle of greater than or equal to 55° is an indicator of FAI.4 The radiographic signs of the Cam and pincer morphological abnormality are often overlooked because they are not looked for routinely.3 When detected, these radiographic signs provide the diagnosis of FAI, provided they are consistent with the clinical fndings.3 Additional radiographic features of FAI may include herniation pits (Pitt’s pits, geode) within the femoral neck, or an accessory ossicle along the superior acetabular rim (os acetabulum). Both fndings are historically viewed as normal physiological variants,3,7 however femoral herniation pits have been found in up to 33% of FAI patients.22 It is suggested that the high prevalence of these fbrocystic changes are the result of recurrent FAI rather than an incidental fnding in FEMOROACETABULAR IMPINGMENT JAROSZ Figure 3: Combination of Cam-type and pincer-type FAI. AP pelvic radiograph of a 33-year-old male patient demonstrating a combina- tion of Cam (arrow) and pincer lesions (arrowhead). Note the early degenerative changes to the acetabulum. Figure 4: Combination of Cam-type and pincer-type FAI. Lateral hip radiograph of a 33-year-old male patient demonstrating a combina- tion of Cam (arrow) and pincer lesions (arrowhead). Note the early degenerative changes to the acetabulum.
CJA June 2012
CJA December 2012