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A CT-free hip navigation system using an anteroposterior plain radiograph of the hip
International Congress Series 1256 (2003) 1345
A CT-free hip navigation system using an anteroposterior plain radiograph of the hip W. Yamanashi a,*, N. Sugano a, T. Sasama b, T. Nishii a, H. Miki a, Y. Sato b, H. Yoshikawa a a
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 565-0871, 2-2 Yamadaoka, Suita, Japan b Division of Interdisciplinary Image Analysis, Osaka University Graduate School of Medicine, 565-0871, 2-2 Yamadaoka, Suita, Japan Received 14 March 2003; received in revised form 14 March 2003; accepted 17 March 2003
Keywords: CT-free navigation; Plain radiograph; Accuracy
1. Introduction We have developed a new CT-free hip navigation system for the lateral decubitus position by using an anteroposterior (AP) plain radiograph of the hip that is used for giving a pelvic coordinate to measure the cup orientation. The purpose of this study is to evaluate the accuracy of this method by computer simulation using pelvic CT image data of 40 patients. 2. Methods Digitally reconstructed radiographs (DRRs) of the hip that simulate AP plain radiographs and pelvic computer models were generated from 40 sets of the CT images. On the DRRs, contours of the lateral border of the ilium, acetabular rim, and acetabular floor were determined and were defined as three boundary strings. On the three corresponding areas of the pelvic computer models, three sets of 10 points were acquired by touching the surface digitally. The acquiring points were registered to the X-ray path surface models that were made by connecting the given X-ray source point and the three boundary strings on DRRs. The angular errors of registration were calculated from the resultant matrix of registration. The acetabular center using the best-fit sphere technique was defined as a target, and the target registration error (TRE) was calculated. 3. Results and conclusion The mean angular errors were 1.9 F 1.4j for flexion – extension, 1.3 F 1.0j for adduction – abduction, and 1.6 F 1.2j for internal – external rotation. The mean TRE at the acetabular center was 1.8 F 0.9 mm. AP radiographs of the hip are not only most common imaging modality in the hip practice but also usually reflect the functional pelvic position of each patient. Moreover, this method with a small TRE could enable to navigate the acetabular cup position as well as the cup orientation. The CT-free hip navigation using AP plain radiographs is suggested to be quite accurate and can be an alternative method of THA navigation. * Corresponding author. Tel.: +81-6-6879-3552; fax: +81-6-6879-3559. E-mail address: [email protected] (W. Yamanashi). 0531-5131/03 D 2003 Published by Elsevier Science B.V. doi:10.1016/S0531-5131(03)00294-2
A CT-free hip navigation system using an anteroposterior plain radiograph of the hip W. Yamanashi a,*, N. Sugano a, T. Sasama b, T. Nishii a, H. Miki a, Y. Sato b, H. Yoshikawa a a
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 565-0871, 2-2 Yamadaoka, Suita, Japan b Division of Interdisciplinary Image Analysis, Osaka University Graduate School of Medicine, 565-0871, 2-2 Yamadaoka, Suita, Japan Received 14 March 2003; received in revised form 14 March 2003; accepted 17 March 2003
Keywords: CT-free navigation; Plain radiograph; Accuracy
1. Introduction We have developed a new CT-free hip navigation system for the lateral decubitus position by using an anteroposterior (AP) plain radiograph of the hip that is used for giving a pelvic coordinate to measure the cup orientation. The purpose of this study is to evaluate the accuracy of this method by computer simulation using pelvic CT image data of 40 patients. 2. Methods Digitally reconstructed radiographs (DRRs) of the hip that simulate AP plain radiographs and pelvic computer models were generated from 40 sets of the CT images. On the DRRs, contours of the lateral border of the ilium, acetabular rim, and acetabular floor were determined and were defined as three boundary strings. On the three corresponding areas of the pelvic computer models, three sets of 10 points were acquired by touching the surface digitally. The acquiring points were registered to the X-ray path surface models that were made by connecting the given X-ray source point and the three boundary strings on DRRs. The angular errors of registration were calculated from the resultant matrix of registration. The acetabular center using the best-fit sphere technique was defined as a target, and the target registration error (TRE) was calculated. 3. Results and conclusion The mean angular errors were 1.9 F 1.4j for flexion – extension, 1.3 F 1.0j for adduction – abduction, and 1.6 F 1.2j for internal – external rotation. The mean TRE at the acetabular center was 1.8 F 0.9 mm. AP radiographs of the hip are not only most common imaging modality in the hip practice but also usually reflect the functional pelvic position of each patient. Moreover, this method with a small TRE could enable to navigate the acetabular cup position as well as the cup orientation. The CT-free hip navigation using AP plain radiographs is suggested to be quite accurate and can be an alternative method of THA navigation. * Corresponding author. Tel.: +81-6-6879-3552; fax: +81-6-6879-3559. E-mail address: [email protected] (W. Yamanashi). 0531-5131/03 D 2003 Published by Elsevier Science B.V. doi:10.1016/S0531-5131(03)00294-2