CT evaluation of periacetabular osteotomies

Abstract

W e have previously described a simple and reproducible three-dimensional technique of CT for the measurement of the cover of the femoral head in acetabular dysplasia in adults. We now describe the application of this technique in ten patients with symptomatic dysplasia to assess the degree and direction of dysplasia and to measure the cover obtained at acetabular osteotomy.The indices obtained gave a useful indication of the degree and direction of the dysplasia and confirmed which components had been used most efficiently to achieve cover. The information is easily presented in graphical form and gives a clearer indication of the cover obtained than the indices derived from plain radiographs. Accurate assessment of indices of dysplasia and of cover of the femoral head is difficult, 1-4 but is essential when planning and evaluating osteotomies around the hip. 1,5-7 Some information concerning lateral cover of the femoral head can be obtained from plain radiographs by measuring the centre-edge angle of Wiberg, and about anterolateral cover from the 'false-profile' view of Lequesne and de Seze. 1,[8][9][10][11][12][13] Complicated mathematical estimations of acetabular cover have also been made from plain radiographs but the methods are complex and include many assumptions regarding the geometry of the hip. 8,14 More information may be obtained from CT 7,11,[15][16][17][18][19] and three-dimensional (3D) CT studies, 20,21 but these involve high exposures to radiation and are difficult to interpret. No MRI techniques have been described for assessing acetabular dysplasia.We have devised a simple and reproducible 3DCT technique to measure cover of the acetabulum in adults. 22 We now describe its use in planning the correction required for periacetabular osteotomy and in assessing the amount obtained. Patients and MethodsWe studied ten women with a mean age of 26 years (16 to 41) who had symptomatic acetabular dysplasia. We measured the centre-edge angles (CEA) on the anteroposterior (AP) and false-profile views (VCA), the acetabular index of the weight-bearing zone (TA), the femoral head extrusion index (FHEI) and the lateral subluxation index (LSI) 1,[8][9][10]13,23,24 (Table I) before and after operation. All measurements were made on standing AP pelvic and falseprofile views by two independent observers. We also carried out 3DCT on all the patients before and after operation to identify the degree and direction of the dysplasia, to plan the correction required at the time of periacetabular osteotomy, to assess the correction obtained subsequently and to compare it with the preoperative plan, the contralateral side and a normal control group (Figs 1 to 6). For CT we used a GE HiLight Scanner (GE Medical Systems, Milwaukee, Wisconsin). The subject was positioned supine with the midline of the body aligned with the central axis of the scanning table. The hips were extended and the feet stabilised with the hips in 15° of external rotation. Care was taken to ensure that there was no pelvic tilt or flexion of the hip ...

Virtual Bernese osteotomy using three-dimensional computed tomography in hip dysplasia

“…However, this method is a two dimensional approach for a three-dimensional anatomic structure. The graph of CEAs after real Bernese osteotomy following their method showed lateral and anterior overcoverage and posterior acetabular deficiency [10,16]. This can be explained by our investigation.…”

“…These can induce some error in the normal data. While lateral pelvic tilt can be controlled by assessing the anteroposterior scout image, the vertical tilt is difficult to measure in the supine position and may lead to inaccurate measurements [10]. However, the data of sagittal spinopelvic alignment are normally quite variable according to the patient's position and the position for real Bernese osteotomy is also supine, we think it is also reasonable to take a CT in the same supine position.…”

“…Dandachli et al [9] suggested a new evaluation method for dysplastic hip from the view of weight bearing surface, but insufficient weight bearing surface is not the only cause of secondary osteoarthritis and they did not acknowledge the amount and direction of the correction. Janzen et al proposed more improved method to determine the direction and amount of rotation using 3D CT [4,10]. This method indicated that the amount and direction of angular correction needed to normalize the acetabular coverage could be determined in a straightforward way by the difference in center-edge angles (CEAs) between the normal and dysplastic acetabulum at any point of the acetabulum.…”

Ct Measurement of Proximal Femoral Medullary Cavity Morphology in Healthy Subjects From Northern China

“…In comparison with radiographic measurements, CT-based anatomical measurements have improved accuracy and reduced errors, as CT it is not affected by femoral rotation and the subjective determination of the bone threshold. Preoperative CT planning provides accurate anatomical information of the medullary cavity, and provides strong evidence for determining surgical goals and plans, especially in the preoperative design of custom prostheses [20].…”

Surgical treatment for young adult hip dysplasia: joint-preserving options

“…Computed tomography images can provide morphologic analysis of acetabular deficiencies by measuring the anterior acetabular sector angle (AASA), the posterior acetabular sector angle (PASA), and the horizontal acetabular sector angle (HASA) [12]. It indicates a dysplastic hip if the AASA is less than 50°, the PASA less than 90°and the HASA less than 140° [ 13].…”