Geometry Of Thoracolumbar Vertebral Endplate

Accurate knowledge of the bony anatomy of the vertebral endplate is necessary for the design of novel artificial vertebral body, for reason that perfect morphological matching could improve load transmission in endplate-construct interface as well as increase stability, leading to better and faster osseous fusion. Indeed, numerous investigators have conducted studies on the morphology of the vertebral bodies in the sagittal and coronal planes, in which results offered specific information about sagittal and maximum transverse diameters of the vertebral bodies. However, there is a lack of study concerning the geometry of vertebral endplates, especially concavity parameters of endplates. Furthermore, all those reports have focused on cervical or lumbar spines, but no thoracolumbar region. In fact, as a common place of spine fracture, malformation and tumor, thoracolumbar spine is very often concerned in vertebroplasty, so the morphological study of this region is also interesting and might be useful in designing novel artificial vertebral body. Besides, in previous studies, investigators have measured the morphological parameters by employing imaging technique or caliper measurement on cadaveric specimens; however, rarely articles have testified the reliability of imaging techniques for the purpose of geometric measurement.OBJECTIVE:To analyze morphological parameters of vertebral endplates from inferior T10 to superior L3, by employing multiple-planar reformatted computed tomography (CT) images of adults without spine-related symptoms. These parameters were used to provide an accurate geometric description of the endplates from a different point of view. Also, to testify the reliability of morphologic measurement on CT images.Two separate parts have been included in this research:1. Measurement of geometric parameters of thoracolumbar vertebral endplates by employing CT images of adults without spine-related symptoms.2. Comparison of measurement values of CT images and objects by using cadaveric specimens.Method:1. Measurement of geometric parameters of thoracolumbar vertebral endplates by employing CT images of adults without spine-related symptoms. Thoracoabdominal CT images of 65 adults complaining of no spine-related symptoms have been retrospectively selected. All those images have been divided into 4 groups according to the age (>40 or≤40 years) and gender of the subjects, there were 18, 14, 16, 17 participants in each group, respectively. Multiple-planar reformat technology has been used in processing the images by employing GE image work station. Measurements were taken out in midsagittal plane (MSP) as well as specified coronal plane (SCP). The following parameters were measured or calculated: 1. Sagittal concave angle (SCA); 2. Sagittal diameter of endplate (SD); 3. Location of concave region in MSP (LCR); 4. Coronal concave angle (CCA); 5. Transverse diameter of endplate (TD). Statistical evaluation was performed with SPSS software version 17.0. The significance level was set at P<0.05.2. Comparison of measurement values of CT images and objects. Thoracolumbar spines (T10-L3) of 10 cadaveric specimens have been prepared, scanned and multiple-planar reformatted, SCA and SD values were measured in MSP. All those specimens were cut along their MSP into two identical pieces subsequently, and then photos were taken for the measurement of SCA and SD values by employing Photoshop software version CS 8.0.1. Statistical analysis was performed to compare the measurement results of CT images and objects. Inter-modality correlation coefficient was obtained to testify the reliability of CT measurement.Results:1. Measurement of geometric parameters of thoracolumbar vertebral endplates by employing CT images of adults without spine-related symptoms. There was no significant difference of SCA, LCR and CCA values among each groups (P>0.05). From T10 inferior to L3 superior endplate, SCA values were between 162.5°and 163.9°, showing no significant difference (P>0.05); this was also true for the LCR (P>0.05), with the smallest value being 42.5% and the largest 44.2%; however, the values of CCA ranged from 170.9°to 175.7°, and in each vertebrae, superior endplate had a significantly larger CCA than its counterpart except T11 (T11: 0.6°, P=0.346; T12: 2.7°, P<0.05; L1: 2.3°, P<0.05; L2: 4.2°, P<0.05). With respect to SD and TD values, the age of participants showed no significant influence for those two parameters (P>0.05), however, the values of females were significantly smaller than those of males (P<0.05), the former one being about 88% of the latter one. In both genders, the average sagittal diameters (aSD) of each lumbar vertebral endplate (L1-L3) was larger by about 1.6 mm than the value of each thoracic vertebral endplate (T10-T12), showing significant difference (P<0.05). For males, the mean thoracic aSD was 27.6 mm, and the mean lumbar aSD was 29.3 mm; for females, those values were 24.2 and 25.8 mm, respectively. In each vertebrae, TD value of superior endplate was significantly smaller than its counterpart (P<0.05) except T12, the former one being about 91% of the latter one. In thoracolumbar spine, for males, TD values of superior endplates ranged from 34.5 to 42.4 mm, and the values of inferior endplates ranged from 35.6 to 44.5 mm; for females, the maximum and minimum TD values of superior endplates were 29.6 and 37.2 mm, the maximum and minimum TD values of inferior endplates were 30.7 and 38.3 mm, respectively.2. Comparison of measurement values of CT images and objects. With respect to SCA, the mean difference of values measured on CT images and objects was 0.3°, with the inter-modality correlation coefficient being 0.8191. For SD values, the mean difference was 0.3 mm, with the inter-modality correlation coefficient being 0.8806.Conclusion:1. In participants aged 21-65 years, there is no significant difference of sagittal concavity parameters among each thoracolumbar vertebral endplate (T10-L3); however, CCA of superior endplate is almost constantly significantly larger than its counterpart in each vertebrae. Age and gender show no significant influence on concavity parameters in both planes. SD values of lumbar spine (L1-L3) are significantly larger than those of thoracic spine (T10-T12). In each vertebrae, there is no significant difference of SD values between superior and inferior endplates. With respect to TD, the superior endplate is tended to be smaller than the inferior endplate, being about 91% of the latter one. Both the SD and TD values are significantly smaller in females than in males, the former one being about 88% of the latter one.2. There is no significant difference of values measured on CT images and objects, the CT measurement could be regarded as a reliable method in vertebral morphologic study.