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| ORIGINAL ARTICLE |
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| Year : 2022 | Volume
: 17
| Issue : 1 | Page : 38-42 |
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Sexual dimorphism in cervical spine – A magnetic resonance imaging study
Anita R Gune, Swati Sarjerao More
Department of Anatomy, D. Y. Patil Medical College, D. Y. Patil Education Society, Kolhapur, Maharashtra, India
| Date of Submission | 04-Sep-2021 |
| Date of Decision | 16-Nov-2021 |
| Date of Acceptance | 15-Dec-2021 |
| Date of Web Publication | 25-Jul-2022 |
Correspondence Address:
Dr. Swati Sarjerao More
Department of Anatomy, D. Y. Patil Medical College, D. Y. Patil Education Society, Kolhapur - 416 006, Maharashtra
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jdmimsu.jdmimsu_327_21
Background: Morphometric measurements of the spinal cord provide important clues regarding neural and spinal injuries. They are also of forensic importance and can be used to determine sex of an individual. These parameters have been shown to vary across age groups and ethnicity. Currently, there is a paucity of data regarding these parameters in Maharashtra, India. Therefore, studies are required to provide reference values for spinal canal parameters for this population. Aims: To study the cervical spinal canal morphometric differences in males and females in the west Maharashtra population. Materials and Methods: A comparative, retrospective study was conducted on 70 subjects aged between 18 and 70 years (36 males, 34 females). The sagittal vertebral body diameter, the sagittal spinal canal diameter, and the sagittal spinal cord diameter were measured at the C3–C7 level by magnetic resonance imaging. The space available for the spinal cord and Torg's ratio were determined. Statistical Analysis Used: Mann–Whitney U-test and unpaired t-test were used to calculate significant difference at P < 0.05. Results: Mean age of the patients was 48.53 ± 14.67 years. There was significant difference in the sagittal spinal canal diameter and spinal cord diameter (P = 0.000107 and P = 2.20e−16, respectively) from C3 to C7. In all the cases, the Torg's ratio of females (0.97–1.04) was higher than in males (0.89–0.95) and varied significantly (P < 0.05). Conclusions: The study provides reference morphometric values for combined Torg's ratio and individually in males and females in the Kolhapur population.
Keywords: Cervical canal, cervical stenosis, radiological study, spinal cord
How to cite this article:
Gune AR, More SS. Sexual dimorphism in cervical spine – A magnetic resonance imaging study. J Datta Meghe Inst Med Sci Univ 2022;17:38-42 |
| Introduction | |  |
The cervical vertebrae form the skeleton of the neck. It is also the most flexible part of the spinal column, making it the most accessible part in traumatic spinal injuries and internal stress. A significant predisposing factor for increasing incidence of acute neck pain is cervical spinal canal stenosis. Degenerative changes, history of trauma, and/or inflammation usually progress to cervical spinal canal stenosis, further leading to cervical spondylosis neuropraxia and cervical spondylotic myelopathy.[1],[2],[3] When the diameter of the spinal canal is reduced, less space is available for the spinal cord (SAC), a condition termed as cervical canal stenosis.[4] Previous studies have demonstrated that morphometric parameters of the spinal cord vary with age, and sex, usually represented in terms of Torg's ratio, and calculated as the ratio between the sagittal diameter of the spinal canal and the sagittal diameter of the vertebral body. In patients with complaints of neck pain, the mean Torg's ratio was 0.73 for men and 0.80 for women.[5] In general, a ratio of <0.8 indicates significant spine stenosis, coupled with an increased risk of neurologic injury.[6] Torg's ratio, commonly used with SAC value, is important in determining the symptoms and severity of spinal cord compression in cervical canal stenosis.[7]
In addition to providing clues about neurological injuries, morphometric parameters of the spinal cord also present significant forensic relevance. The ability to distinguish individual skeletal remains based on variation can be utilized to distinguish between ancestry groups, age groups, or sex.[8] Although the entire skeleton is ideal for determining sex, often remains are incomplete. Moreover, sexual dimorphism has also been noted in bones throughout the skeleton, including the cervical vertebrae. They are less susceptible to damage and more likely to be recovered from the site of disaster.[9]
Magnetic resonance imaging (MRI) is an efficient technique to accurately measure the morphological parameters of the spinal cord. Morphometric parameters generated by MRI are necessary for calculating the accurate values of SAC and Torg's ratio.[10],[11] Currently, there is a paucity of information regarding the morphometric parameters of the cervical spine and its sexual dimorphism, in the state of Maharashtra. Therefore, the study aimed to evaluate the differences between the morphometric measurements of cervical spinal canal in males and females of western Maharashtra population through MRI.
| Materials and Methods | | |
A retrospective study was undertaken at a tertiary care center in Kolhapur for the data from March to July 2018 (6 months) comprising 70 subjects between 18 and 70 years of age following approval by the institutional ethics committee. Images of individuals who underwent MRI of the cervical region for various reasons were included. Care was taken to exclude individuals with congenital anomalies of the vertebral column and cervical region.
All patients had undergone MRI of the cervical region on a 1.5 Tesla MRI (Avanto, Siemens, Germany) by a spinal coil and standardized neutral head position. T1-weighted and T2-weighted images were acquired. Sagittal T1-weighted fast spin echo (FSE) sequence (repetition time in ms/echo time in ms, 700/11; section thickness, 3 mm; field of view, 250 mm × 250 mm; matrix, 384 × 288), sagittal T2-weighted turbo-spin echo sequence (2920/101; section thickness, 3 mm; insertion gap, 1 mm), and transverse T2-weighted fast recovery FSE sequence at one or multiple levels (3960/88; section thickness, 3 mm; insertion gap, 0.5 mm; field of view, 200 mm × 200 mm; matrix, 384 × 214) were employed. The dimensions of the entities were measured by the Osirix DICOM viewer 64-bit software (Pixmeo, SARL, 266 Rue de Bernex, CH-1233 Bernex, Switzerland), and a mean value of three measurements was considered. All measurements were made mid-sagittal at each spinal level from C3 to C7 vertebra. For each measurement, there were two observers who recorded the readings in two independent desktops, and the mean of both the measurements was considered to avoid interobserver bias.
[Figure 1] depicts the measured parameters. To measure the sagittal vertebral body diameter, the midpoint between the superior and inferior endplates was considered. Likewise, the sagittal spinal canal diameter was measured from the center of the vertebral body's superior and inferior surfaces to a point of junction of spine and laminae. The sagittal spinal cord diameter was measured at midline transverse line of the vertebral body at the level of C3, C4, C5, and C6 and C7. To calculate SAC, i.e., SAC; sagittal cord diameter and the corresponding sagittal canal diameter were subtracted. Torg's ratio was calculated as the ratio between spinal canal diameter and vertebral body diameter. | Figure 1: A representative image showing the magnetic resonance imaging scan of the cervical region of the spinal cord and the corresponding morphometric parameters analyzed. The left part showing the diameter of the vertebral body (in cm), the right side showing the diameter of the spinal canal (in cm) and spinal cord (in mm)
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Descriptive data analyses were performed on MS-Excel. Significant mean differences were calculated by unpaired two-sample t-test and Mann–Whitney U-test wherever applicable. P ≤ 0.05 was considered statistically significant.
| Results | | |
The retrospective study comprised MRI images of 70 subjects. The mean age of the patients was 48.53 ± 14.67 years (47.88 ± 15.24 years for males and 49.20 ± 14.23 for females). As the study is a gender-based comparison, the sex distribution was balanced as 51% (n = 36) males and 49% (n = 34) females. The cumulative mean values (C3–C7) of the sagittal vertebral body diameter, sagittal spinal canal diameter, and sagittal spinal cord diameter in males and females are presented in [Table 1]. The diameter of the vertebral body varied insignificantly through C3–C7 (P = 0.9256). However, there was significant difference in the sagittal spinal canal diameter and spinal cord diameter (P = 0.000107 and P = 2.20e−16 respectively) from C3 to C7. The value of Torg's ratio was in the range of 0.94–0.99 and varied significantly, albeit very low (P = 0.05091). On the contrary, the difference in the SAC value was highly significant in C3 through C7 (P = 2.20e−16). | Table 1: Cumulative mean values (C3-C7) of the sagittal vertebral body diameter, sagittal spinal canal diameter, and sagittal spinal cord diameter in the sample population
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Following this, comparisons of cervical vertebrae (C3–C7) were made between males and females and are presented in [Table 2]. The vertebral body diameter was higher in males than in females, and interestingly, there was a significant difference among both genders, for each of the cervical vertebrae (C3–C7). In all the cases, the Torg's ratio of females (0.97–1.04) was higher than in males (0.89–0.95). Subsequently, there was also a significant difference in the Torg's ratio in all cases. The sagittal spinal canal diameter and the sagittal spinal cord diameter did not vary significantly in any of the cases (P > 0.05). Similarly, the SAC value also did not vary significantly, except for C5. | Table 2: Gender-wise distribution of mean values for cervical vertebra parameters
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| Discussion | | |
Morphometric measurements of the entities of the cervical spine (C3–C7) such as spinal canal diameter, spinal cord diameter, and vertebral body diameter are useful indicators of stenosis, risk of myelopathy, and prognosis following spinal cord injury.[12] In addition, they also have forensic and medicolegal applications.[13] These parameters have been shown to vary across gender, race, and age groups. It has also been suggested that postural and mechanical habits along with environmental and genetic factors contribute largely to these differences.[14],[15],[16] Owing to the application of these parameters; it becomes important to estimate them across sexes and regions. The scarcity of cervical spinal data estimates in western Maharashtra population calls for a study of this nature. The study evaluates the measurements of the cervical spinal canal in males and females by MRI.
A decrease in sagittal canal diameter and sagittal cord diameter going from C3 to C7, except for C4, was noted. Subsequently, there was also a significant decrease in the SAC value. A similar pattern was also seen in the studies on Swiss population by Ulbrich et al. and the Nigerian population by Ndubuisi et al.[14],[16] Contrarily, the cumulative vertebral body diameter of both sexes remained insignificantly altered. Previous studies have demonstrated individuals with lower SAC values have increased risk of cervical cord neuropraxia and cervical stenosis.[10] Herzog et al. have suggested that individuals with low SAC (<5 mm) value and associated with herniated discs, osteophytic spurs, etc., are more susceptible to spinal cord compression.[11] The minimum sagittal spinal canal diameter observed in this study was 13.8 mm, indicating that the participants in the study were not at a risk of spinal cord compression.
Here, vertebral body diameter was higher in males than in females in all C3–C7, findings consistent with previous studies.[17] The vertebral bodies and foramina were significantly wider, more elongated, and higher in males compared to females.[17] Torg's ratio was found to be higher in females than males and varied significantly among both genders similar to Gilsanz and Morishita.[8],[18] The data herein are also in close corroboration with a similar study, performed for the western Maharashtra population in the neighboring district of Kolhapur which shares the same racial as well as the geographical features.[19] The Torg's ratio in males ranged from 0.95 to 0.96 whereas in females 1.06 to 1.08.[19] In addition, it is also in agreement with the findings of studies across other geographical regions like for the North Bengal population by Kar et al. and Nepalese population by Rijal et al. However, they did not observe any significant difference among males and females.[7],[20] Similarly, a higher Torg's ratio in females than in males has also been demonstrated in South African, Korean, Singaporean, and Indonesian population.[20]
These morphometric differences among genders are compounded by the differences in the traditional occupations of males and females; for example, the men who were mainly farmers and artisans are expected to carry heavy loads compared with the females who also had their defined roles such as house hold. Subsequently, the data might also be subject to variations between the urban and rural population, who are engaged in different occupations.[14] In an early study, Wescott was successful in predicting sex from C1 with 77%–90% accuracy.[21] Similarly, in a recent study, cervical vertebrae (C1–C7) from cadavers were used to determine sex in a white Scottish population with 81.8%–100% accuracy.[22] This buttresses the fact that the cervical vertebra could successfully be applied in determining sex in populations. It has been suggested that the degree of sexual dimorphism of a vertebra is directly proportional to the duration of its growth and development.[23] In addition, the differing conclusions for the presence of sexual dimorphism in cervical vertebrae parameters among varying population studies are also subject to methodologies employed for research.[22]
The study establishes and verifies exiting reference values for SAC and Torg's ratio in the population of western Maharashtra published by Kar et al.[7] These values will also be useful as baseline values for further studies in this area, clinical screening, early identification of individuals predisposed to cervical spinal cord injuries, and follow-up of patients for early surgical decision-making and could also find forensic application. The small sample size, however, poses a limitation in that it might not be representative of the entire population. As cervical spinal parameters vary with age groups, a study involving different age groups will provide better insight into the baseline values [Table 3].
| Conclusions | | |
The study is probably one of the initial reports in providing the reference values of morphometric parameters of the cervical spinal canal in males and females of western Maharashtra. Torg's ratio was 0.97–1.04 in females and 0.89–0.95 in males.
Acknowledgments
The authors gratefully acknowledge the valuable input provided by Dr. J. K. Patil, Eureka Diagnostic Center, Kolhapur, over the course of this study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1]
[Table 1], [Table 2], [Table 3]
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