lateral center-edge angle, acetabular index and/or extrusion index The radiological report should include the description of the following 2,3: In addition to the three-dimensional assessment of the acetabular and femoral morphology, which highly benefits from 3D imaging in this situation, MRI allows for assessment of concomitant labral, chondral or ligamentum teres injury as well as the evaluation of the joint capsule 1. Horizontal acetabular sector angle: a value of ≤140° indicates dysplasia Posterior acetabular sector angle: a value of ≤90° indicates dysplasia Other than the crossover sign on the anterior-posterior view of the pelvis, CT can also differentiate posterior under-coverage in the setting of acetabular dysplasia from anterior overcoverage in the setting of pincer morphology or plain acetabular retroversion and it can better assess the grade of posterior deficiency than the posterior wall sign 3.ĬT measurements for the assessment of acetabular dysplasia include the following and are conducted one cut above the greater trochanters 2:Īnterior acetabular sector angle: a value of ≤50° indicates dysplasia It should also comprise the assessment for excessive acetabular anteversion or acetabular retroversion. The main role of CT is improved characterization of the three-dimensional acetabular morphology in a setting of preoperative planning. The anterior center-edge angle of Lequesne (assessed on false profile view – moderate reproducibility)įemoral head-neck-shaft angle (to assess for coxa valga and surgical planning) The cut-off should be also adapted to the measurement and whether the lateral bony acetabular rim or the lateral edge of the acetabular sourcil was taken to measure the lateral center-edge angle 7.įurther measurements to confirm insufficient acetabular coverage are the following 2,4,5: Patients should be in the supine position with both legs in 15° of internal rotation to maximize femoral neck length 2.Ī value of ≤25° is considered abnormal or borderline and a value of ≤20° is an indicator for dysplasia 2,4,5. The most common measurement in acetabular dysplasia is the lateral center-edge angle on a plain anterior-posterior radiograph of the pelvis 2,4. Radiographic assessment of acetabular dysplasia or adult hip dysplasia includes plain radiographs of the pelvis and additional planes as the false profile view of Lequesne, cross-table lateral or frog-leg lateral views.Ĭross-sectional imaging is advised for better three-dimensional characterization, preoperative planning 3 and the detection of chondral and labral lesions. Other schemes differentiate anterior, posterior and global or lateral deficiencies 2. One grading scheme subdivides the acetabular dysplasia into the following patterns with lateral acetabular deficiency being constantly present 3: SubtypesĪcetabular dysplasia can be divided into different patterns concerning 3-D morphology. It may be also due to other hip pathologies that have occurred during childhood as septic arthritis, trauma or Legg-Calve-Perthes disease ref. EtiologyĪcetabular dysplasia might be the result of abnormal growth after treatment or missed developmental dysplasia of the hip during childhood, the etiology of which is multi-factorial in nature. This adds to cartilage and/or labral injury as well as damage to the joint capsule 2-4. ComplicationsĢ5-50% of patients with acetabular dysplasia will develop early hip osteoarthritis if left untreated 1-6.Īcetabular dysplasia is characterized by a smaller weight-bearing surface than the normal acetabulum, which ultimately leads to increased contact stress and static overload due to under-coverage of the femoral head and structural instability. Clinical signs include a positive hip impingement test 11 and/or anterior apprehension test. In addition, there may be limping or signs and symptoms of hip instability 11. Patients can present with hip pain or groin pain especially with extreme positions e.g. The clinical presentation of acetabular dysplasia has been described as variable 11.
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