Lately, there has been an increase in the use of artificial cervical disc arthroplasty (ACDA) for degenerative conditions as an alternative to spinal fusion [
Limited data has been reported on the morphology of cervical endplate. Previous investigators have sought to analyze the anatomy of the cervical vertebral bodies and endplates based on measurements derived from plain radiographs, cadaveric specimens, and computed tomography (CT) scans [
Cervical disc arthroplasty does not take racial differences into consideration and most of the prosthesis are designed according to anthropometric data obtained from White patients. Furthermore, with the increasing use of CDA in China [
41 Chinese subjects (21 females and 20 males) and 24 White subjects (12 females and 12 males) were recruited for our study. The subjects were evaluated for no history of neck pain, cervical spinal disorders, and anatomical anomalies using clinical and radiographic examinations. The study was approved by our Institutional Review Board, and written consent was obtained from all subjects. The mean age and height of the subjects are listed in Table
The mean age and height of the subjects.
Characteristic | Female | Male | ||||
---|---|---|---|---|---|---|
Chinese | White | | Chinese | White | | |
Age (years) | | | | | | |
Height (cm) | | | | | | |
For the Chinese subjects, a CT scan of the endplate was obtained using a helical CT scanner (Siemens, Germany). The scanning procedure was performed to acquire 0.625 mm axial CT slices with a resolution of 512 × 512 pixels. For the White subjects, the scanning procedure was performed to acquire 0.625 mm axial CT slices in a General Electric Light Speed Pro16 CT scanner and resolution of 512 × 512 pixels were obtained.
The images of the upper and lower bony endplates from C3 to C7 (total of 650 endplates) were then 3D reconstructed using a solid modeling software (Rhinoceros Robert McNeel & Associates, Seattle, Washington). Window settings for cortical digitization had a width of 100 Hounsfield units (HU) and center at 500 HU (Figure
(a) Digitization of the endplates from sagittal CT images. (b) Reconstruction of the 3D models of upper and lower endplates from C3 to C7.
To analyze the 3D surface anatomy of the middle and lower cervical vertebral endplates, an automatic algorithm was programmed to systematically calculate the endplate from the obtained 3D models. To do this, first a characteristic transverse plane for each endplate was generated through fitting based on least distances of the points on the endplate to the plane (Figure
Two orthogonal views (coronal plane (a) and sagittal plane (b) of a cervical vertebra are shown. EPWu: upper endplate width; EPWl: lower endplate width; EPDu: upper endplate depth; EPDl: lower endplate depth.
A Student’s
The article described the results from 650 middle and lower cervical (C3–C7) endplates. The morphological measurements of the endplate were summarized by race (Table
Dimensions of linear parameters categorized by race.
Race | C3 | C4 | C5 | C6 | C7 | |
---|---|---|---|---|---|---|
EPWu (mm) | Chinese | | | | 17.2 ± 2.3 | |
White | | | | 18.7 ± 2.5 | | |
| 0.03 | 0.02 | 0.02 | 0.03 | 0.36 | |
| ||||||
EPDu (mm) | Chinese | | | | 15 ± 2 | |
White | | | | 16.5 ± 2 | | |
| 0.38 | 0.65 | 0.04 | 0.03 | 0.03 | |
| ||||||
EPWl (mm) | Chinese | | | | 19.3 ± 2.8 | |
White | | | | 20.6 ± 2.4 | | |
| 0.01 | 0.03 | 0.04 | 0.39 | 0.16 | |
| ||||||
EPDl (mm) | Chinese | | | | 16.5 ± 2 | |
White | | | | 18.4 ± 1.7 | | |
| 0.56 | 0.43 | 0.03 | 0.01 | 0.04 | |
| ||||||
EPWu/EPDu | Chinese | | | | 1.16 ± 0.15 | |
White | | | | 1.16 ± 0.24 | | |
| 0.66 | 0.33 | 0.79 | 0.93 | 0.82 | |
| ||||||
EPWl/EPDl | Chinese | | | | | |
White | | | | | | |
| 0.24 | 0.03 | 0.43 | 0.26 | 0.78 |
All area parameters were observed to constantly increase from C3 to C7 in both the Chinese and White subjects. The average areas of cervical endplates at different levels ranged from 169.9 mm2 to 281.5 mm2 and 204.5 mm2 to 316.8 mm2 for Chinese and White subjects, respectively (Table
Dimensions of area parameters categorized by race.
Race | C3 | C4 | C5 | C6 | C7 | |
---|---|---|---|---|---|---|
EPAu | Chinese | 169.9 ± 39.2 | 183.5 ± 46.4 | 198.7 ± 59.5 | 234.1 ± 56.4 | 263.1 ± 64.8 |
White | 204.5 ± 42.4 | 221.4 ± 40.5 | 230.8 ± 39.6 | 264.2 ± 45.4 | 291.2 ± 47.2 | |
| 0.00 | 0.00 | 0.02 | 0.03 | 0.06 | |
| ||||||
EPAl | Chinese | 203.1 ± 41.8 | 211.2 ± 49.9 | 237.6 ± 52.7 | 261.3 ± 59.1 | 281.5 ± 64.6 |
White | 231.2 ± 45.2 | 243.7 ± 50.1 | 266.1 ± 46.5 | 300.2 ± 51.8 | 316.8 ± 39.4 | |
| 0.01 | 0.01 | 0.03 | 0.01 | 0.02 |
The average width of cervical endplates at different levels ranged from 14.6 mm to 20.3 mm and from 16.1 mm to 22.4 mm in Chinese and White females, respectively. The average depth of cervical endplates at different levels ranged from 13.0 mm to 15.8 mm and from 13.8 mm to 17.5 mm for Chinese and White females, respectively (Table
Dimensions of linear parameters categorized by race and sex.
Race and sex | C3 | C4 | C5 | C6 | C7 | |
---|---|---|---|---|---|---|
EPWu (mm) | Chinese female | 14.6 ± 1.5 | 15.4 ± 1.7 | 15.8 ± 1.9 | 16.9 ± 1.7 | 18.8 ± 2.1 |
White female | 16.1 ± 1.8 | 16.9 ± 2.0 | 17.3 ± 1.5 | 18.4 ± 1.4 | 20.1 ± 1.8 | |
| 0.02 | 0.03 | 0.03 | 0.01 | 0.08 | |
Chinese male | 15.1 ± 2.1 | 16.2 ± 1.9 | 16.4 ± 1.6 | 17.6 ± 1.2 | 19.6 ± 1.4 | |
White male | 17 ± 2.7 | 17.7 ± 1.1 | 17.9 ± 2.1 | 19.1 ± 1.4 | 20.9 ± 1.3 | |
| 0.03 | 0.02 | 0.01 | 0.03 | 0.01 | |
| ||||||
EPDu (mm) | Chinese female | 13.0 ± 1.8 | 13.4 ± 1.8 | 13.4 ± 1.6 | 14.1 ± 1.7 | 15.4 ± 1.9 |
White female | 13.8 ± 1.5 | 14.5 ± 1.1 | 15.0 ± 1.6 | 16.4 ± 2.0 | 17.2 ± 1.9 | |
| 0.30 | 0.06 | 0.00 | 0.00 | 0.01 | |
Chinese male | 14.4 ± 1.9 | 14.9 ± 2.1 | 15.4 ± 2.33 | 15.9 ± 2.0 | 17.0 ± 1.9 | |
White male | 14.8 ± 1.5 | 15.2 ± 2.1 | 15.4 ± 2.0 | 16.6 ± 2.2 | 18.0 ± 2.4 | |
| 0.28 | 0.69 | 0.99 | 0.35 | 0.19 | |
| ||||||
EPWl (mm) | Chinese female | 15.1 ± 1.8 | 15.6 ± 1.9 | 16.7 ± 2.0 | 18.4 ± 2.7 | 20.3 ± 2.4 |
White female | 16.8 ± 1.9 | 17.4 ± 2.7 | 18.1 ± 1.4 | 19.1 ± 1.9 | 22.4 ± 2.9 | |
| 0.02 | 0.03 | 0.04 | 0.44 | 0.08 | |
Chinese male | 16.0 ± 2.0 | 16.5 ± 2.1 | 18.2 ± 2.3 | 20.2 ± 2.8 | 22.5 ± 3.0 | |
White male | 18.0 ± 2.2 | 18.3 ± 2.8 | 20.1 ± 1.9 | 21.6 ± 2.4 | 23.2 ± 2.9 | |
| 0.01 | 0.04 | 0.04 | 0.15 | 0.51 | |
| ||||||
EPDl (mm) | Chinese female | 14.9 ± 1.9 | 15.2 ± 1.9 | 15.3 ± 2.1 | 15.5 ± 2.0 | 15.8 ± 2.2 |
White female | 15.1 ± 2.2 | 15.6 ± 2.0 | 16.5 ± 2.4 | 17.6 ± 2.0 | 17.5 ± 2.0 | |
| 0.78 | 0.12 | 0.01 | 0.01 | 0.03 | |
Chinese male | 15.7 ± 1.7 | 16.0 ± 1.8 | 17.0 ± 2.1 | 17.3 ± 1.9 | 17.3 ± 2.2 | |
White male | 16.1 ± 1.9 | 16.4 ± 2.3 | 17.1 ± 1.9 | 18.9 ± 1.5 | 18.4 ± 2.0 | |
| 0.07 | 0.33 | 0.34 | 0.01 | 0.16 | |
| ||||||
EPWu/EPDu | Chinese female | 1.12 ± 0.16 | 1.16 ± 0.19 | 1.19 ± 0.18 | 1.20 ± 0.14 | 1.23 ± 0.16 |
White female | 1.17 ± 0.18 | 1.16 ± 0.06 | 1.16 ± 0.14 | 1.14 ± 0.18 | 1.19 ± 0.20 | |
| 0.62 | 0.99 | 0.74 | 0.43 | 0.62 | |
Chinese male | 1.08 ± 0.18 | 1.10 ± 0.17 | 1.11 ± 0.15 | 1.12 ± 0.14 | 1.16 ± 0.12 | |
White male | 1.15 ± 0.15 | 1.18 ± 0.19 | 1.19 ± 0.20 | 1.17 ± 0.15 | 1.18 ± 0.19 | |
| 0.26 | 0.22 | 0.20 | 0.22 | 0.86 | |
| ||||||
EPWl/EPDl | Chinese female | 1.02 ± 0.12 | 1.02 ± 0.11 | 1.1 ± 0.14 | 1.19 ± 0.12 | 1.30 ± 0.26 |
White female | 1.11 ± 0.11 | 1.11 ± 0.13 | 1.07 ± 0.20 | 1.09 ± 0.13 | 1.31 ± 0.28 | |
| 0.04 | 0.04 | 0.59 | 0.03 | 0.99 | |
Chinese male | 1.01 ± 0.14 | 1.02 ± 0.11 | 1.06 ± 0.14 | 1.19 ± 0.13 | 1.31 ± 0.19 | |
White male | 1.08 ± 0.18 | 1.11 ± 0.12 | 1.17 ± 0.10 | 1.15 ± 0.17 | 1.27 ± 0.23 | |
| 0.29 | 0.04 | 0.02 | 0.45 | 0.59 |
(a), (b), (c), and (d) show the linear dimensions of the upper and lower endplates. (e) and (f) show the ratio of endplate width to depth for the upper and lower endplates. #: differed significantly between the Chinese females and White females;
The average areas of cervical endplates at different levels ranged from 169.9 mm2 to 281.5 mm2 and from 204.5 mm2 to 316.8 mm2 for Chinese females and White females, respectively. Measurement of area showed that the EPAu of Chinese females was generally smaller than that of White females from C3 to C6
Dimensions of area parameters categorized by race and sex.
Race and sex | C3 | C4 | C5 | C6 | C7 | |
---|---|---|---|---|---|---|
EPAu | Chinese female | 170.9 ± 33.2 | 180.6 ± 32.9 | 188.9 ± 32.5 | 214.5 ± 42.5 | 252.1 ± 47.1 |
White female | 199.2 ± 44.3 | 208.5 ± 42.5 | 224.4 ± 43.3 | 245.4 ± 51.2 | 278.2 ± 46.6 | |
| 0.04 | 0.04 | 0.001 | 0.01 | 0.13 | |
Chinese male | 171.2 ± 44.6 | 185.5 ± 57.6 | 207.1 ± 42.3 | 251.5 ± 33.7 | 274.5 ± 55.6 | |
White male | 216.1 ± 49.6 | 228.8 ± 40.7 | 234.4 ± 41.2 | 275.4 ± 41.7 | 298.2 ± 50.6 | |
| 0.01 | 0.03 | 0.04 | 0.03 | 0.23 | |
| ||||||
EPAl | Chinese female | 201.2 ± 42.1 | 203.6 ± 41.7 | 225.5 ± 48.7 | 246.1 ± 42.8 | 272.7 ± 49.8 |
White female | 202.7 ± 42.7 | 215.3 ± 43.1 | 245.1 ± 44.7 | 270.7 ± 47.8 | 285.2 ± 41.4 | |
| 0.92 | 0.44 | 0.26 | 0.13 | 0.46 | |
Chinese male | 204.6 ± 44.9 | 217.4 ± 57.6 | 248.2 ± 56.3 | 275.8 ± 60.3 | 290.7 ± 62.3 | |
White male | 248.1 ± 42.7 | 260.3 ± 52.3 | 278.1 ± 54.4 | 317.7 ± 57.8 | 335.2 ± 36.4 | |
| 0.01 | 0.04 | 0.14 | 0.03 | 0.03 |
The average width of cervical endplates at different levels ranged from 15.1 mm to 22.5 mm and from 17.0 mm to 23.2 mm for Chinese and White males, respectively. The average depth of cervical endplates at different levels ranged from 14.4 mm to 17.3 mm and from 14.8 mm to 18.4 mm for Chinese and White males, respectively (Table
The average areas of cervical endplates at different levels ranged from 171.2 mm2 to 290.7 mm2 and 216.1 mm2 to 335.2 mm2 for Chinese and White males, respectively. Measurement of area showed that the EPAu of Chinese males was generally smaller than that of White males from C3 to C6
The present study showed that the subaxial cervical spine endplates of Chinese males and females were smaller than those of their White counterparts in most linear and area parameters. In Chinese females, the EPWu and EPWl were smaller than in White females from C3 to C5; and the EPDu and EPDl were smaller than in White females from C5 to C7. The ratio of EPWl/EPDl was smaller in Chinese females than in White females at C3, C4, and C6 levels. The EPAu of Chinese females was smaller than that of White females from C3 to C6. In Chinese males, the EPWu and EPWl were significantly smaller than in White males from C3 to C5, and the only significant difference was observed at C6 in EPDl. The ratio of EPWl/EPDl was significantly different between the Chinese and White men at C4-5 levels. The EPAu and EPAl of Chinese males were smaller than those of White males at C3, C4, and C6 levels. These results proved the hypothesis that there are distinct differences in size and shape between the Chinese and White subaxial cervical spine endplates.
Many studies have reported on the measurement of cervical spine endplates. Panjabi et al. studied endplate morphology from 12 cadaveric cervical spine specimens using the morphometer, a device used to define points on the measuring surface. These results agree quite closely with our measurements of the endplates of living White subjects of the EPWu, EPDu, EPWl, and EPDl. Tan et al. studied 10 cadavers of Chinese Singaporean subjects with a digitizer, following the measurements proposed by Panjabi, and compared the results to the White population. They found similar trends with our study and noticed that the dimensions of the Singaporeans were smaller than the Caucasians. Kim et al. utilized CT scans to measure the endplate morphology of 57 Korean cadavers and compared them with the previous studies. They found deeper but narrower endplates in the Koreans than in the Caucasians and overall larger dimensions than in the Singaporeans, but still smaller than in the Whites. Interestingly, they reported smaller endplate width than depth from C3 to C6, which is different from the results of the current study of the Chinese, the study of the Caucasians reported by Panjabi, and that of the Singaporeans reported by Tan. Comparing our data to these previous studies, the values for all the selected parameters in living Chinese cervical endplates were considerably larger than those reported for Singaporean subjects by 1 to 2 mm. The EPWu values in living Chinese cervical endplate were considerably larger than those reported for Korean subjects by 1 to 2 mm. The EPDu, EPWl, and EPDl values in living Chinese cervical endplate were considerably smaller than those reported for Korean subjects by 1 to 3 mm. The width to depth ratio of the endplate increased from C3 to C7 and similar Singaporean subjects.
The anatomical results from this study on the cervical endplates could provide guidelines for implant sizing and prosthesis design. Multiple studies have reported from 1.2% to 11% reoperation rates after CDA at 2-year followup [
Morphometric evaluation of the vertebral is not a new subject in study of the cervical spine. With the numerous technologic advancements in CT over the last decade, the CT based methods of measurement is now able to precisely evaluate the cervical vertebral dimensions. Main methods of the previous studies used digitizers or CT scans on cadavers. However, it should be stated that our data were measured from the living subjects. Despite the little influence on morphological measurements, in vivo methods have potential advantages for subsequential biomechanical studies, such as kinematic/kinetic modeling, finite element analysis, and bone quality assessment [
The current study had several limitations. One of the prominent limitations of the present study is the relatively small size of the subjects. This study included data from 65 healthy subjects. If a larger size was studied then other significant differences may also have been revealed. In addition, all the Chinese subjects recruited in the present study perhaps only represented the subgroup population of Chinese. However, the magnitude of the difference likely remains small since other studies have also utilized a small number of subjects with reliable results. We are continuing to collect more subjects for each group. In future studies, we will also examine the ACD (artificial cervical disc) mismatch data for Chinese patients, and these data can be useful for designing systems. The study has been presented in the 8th International Congress of Chinese Orthopaedic Association [
To conclude, the present study used an in vivo CT approach to quantitatively investigate the dimensions and shape of cervical endplates. Significant differences were observed between Chinese and White men and women in most linear and area parameters at various vertebral levels. These statistically significant results provide baseline information for design of CDA implants and surgical techniques. These data should be used to create precise and accurate new disc prosthesis so complications arising from cervical disc arthroplasty could be reduced and patients’ health could be restored faster.
Qi Yao and Peng Yin are both co-first authors.
The authors declare that they have no conflicts of interest.
The authors would like to thank all subjects included in the research.