Three-dimensional evaluation of volume change in ossification of the posterior longitudinal ligament of the cervical spi
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ORIGINAL ARTICLE
Three-dimensional evaluation of volume change in ossification of the posterior longitudinal ligament of the cervical spine using computed tomography Tomohiro Izumi • Toru Hirano • Kei Watanabe Atsuki Sano • Takui Ito • Naoto Endo
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Received: 21 November 2012 / Revised: 3 July 2013 / Accepted: 29 August 2013 / Published online: 3 September 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract Background Two-dimensional imaging is not adequate for evaluating ossification of the posterior longitudinal ligament (OPLL). This study was designed to evaluate the accuracy of a novel computed tomography (CT)-based three-dimensional (3D) analysis method that we had devised to measure volume changes in OPLL. Subjects and methods Twenty OPLL patients (12 male and 8 female; mean age 63.6 years) who were being followed conservatively were examined twice with an interval of at least 1 year between the two scans. The mean interval was 22 (range 12–45) months. A 3D model was created with DICOM data from CT images, using the MIMICSÒ software to calculate the volume. The mean ossification volume was determined from two measurements. Since ossification size varies widely, evaluation of change in volume is generally affected by the original size. Therefore, the change in ossification volume between the first and second CT examinations was calculated as the annual rate of progression. Results The type of OPLL was classified as continuous in 3 patients, segmented in 3, and mixed in 14. The mean ossification volume was 1,831.68 mm3 at the first examination and 1,928.31 mm3 at the second, showing a
T. Izumi (&) T. Hirano K. Watanabe A. Sano N. Endo Division of Orthopedic Surgery, Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi Dori, Chuo-ku, Niigata 951-8510, Japan e-mail: [email protected] T. Ito Niigata City General Hospital, 463-7 Syumoku, Chuo-ku, Niigata 950-1197, Japan
significant mean increase in ossification volume. The mean annual rate of lesion increase was 3.33 % (range 0.08–7.79 %). Conclusion The 3D method used allowed detailed OPLL classification and quantification of change in the ossified volume. Thus, this method appears to be very useful for quantitative evaluation of OPLL with only minimal measurement error. Keywords
OPLL 3D analysis CT Ossification
Introduction Ossification of the posterior longitudinal ligament (OPLL) of the cervical spine is one of the main causes of myeloradiculopathy in Asian populations, especially in Japan [1– 4]. Accurate determination of the size of OPLL and the nature of its growth in terms of length and thickness is important because these factors crucially relate to spinal canal stenosis and can cause myelopathy [5]. Evaluating the size and growth of OPLL is important to determine the timing of the operation and the risk factors for rapid progression of OPLL. Previous attempts have already been made to measure the size of OPLL [6–10]. However, these methods involved t
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