VARIATIONS IN THE DIMENSIONS OF SUB AXIAL VERTEBRAE AND ITS CLINICAL SIGNIFICANCE

Address for Correspondence: Dr.V.Ananthi, Tutor, Department of Anatomy, Rajah Muthiah Medical College, Chidambaram, Tamil Nadu, India. E-Mail: ananthisricharan@gmail.com Introduction: cervical vertebrae are the upper most vertebrae in vertebral column. They are more prone to damage during road traffic accidents. Their dimensions are important for various spinal surgical procedures to access the spinal cord for decompression procedures. Aim and Objective: Variations in the dimensions of sub axial vertebrae is of very important for spinal surgical procedures like Transpedicular screwing, Laminectomy, Foraminectomy, Transcorporeal Micro decompression surgery. The present study was done in the C3–C7 vertebrae of south Indians to know the Mean values of various dimensions of sub axial vertebrae. Materials and Methods: The present study was done in 60 sub axial vertebrae, which were done in Rajah Muthiah Medical College, Chidambaram. Dimensions of Body (Antero posterior Length, Transverse Length & Height), Pedicle (Height, Length & Width), Lamina (Length, width & Height), Foramen Transversorium (Antero posterior Diameter, Transverse Diameter), Spinous process (Length) were studied. Main outcome measure: Variations in the dimensions of body, pedicle, lamina, Spinous process, Foramen transversorium were observed. Result: The Mean values of dimensions of vertebral body, lamina, pedicle, Foramen Transversorium & Spinous process were measured. Dimensions of body was maximum at C6 level. Length of pedicle was maximum at C3, Minimum at C6. Height & width of pedicle gradually increase from C3 to C7. Height of Lamina was maximum at C6, Length & width of Laminae was gradually increases from C3 to C7. Conclusion: This study will provide the knowledge about dimensions of sub axial vertebrae in South Indian population. This will be helpful for spinal Surgeries & Radiological Interpretations.


INTRODUCTION
The cervical part of vertebral column presents a curvature which is formed around 3 -4 months after birth.When the infant learns to erect its The cervical vertebrae are seven in number; They developed from sclerotome around notochord.
head.Normally there are 2 primary curvatures -thoracic and sacral curvatures.The other two secondary curvatures are cervical & lumbar; cervical curvature is formed during 3 -4 months after birth; Lumbar curvature formed when the baby learns to walk.The cervical vertebrae, the smallest of the movable vertebrae are typified by a foramen in each transverse process.Among 7 vertebrae 1, 2, 7 are having special features, so they are called as atypical vertebrae other 4 vertebrae are typical vertebrae they have common features.
The typical cervical vertebrae has a body, pedicles, lamina, spinous process, Transverse process, superior and Inferior articular processes, and foramens in the transverse process.The mature transverse process is formed by fusion of costal element with body and true transverse process Sixty sub axial vertebrae were studied.The differences for all the evaluated between right left side were found insignificant except Foramen transversorium.
Bodies: Transverse length of the body was maximum at C6 and minimum at C3; AP length of body was maximum at C6 minimum at C3.But Height of body gradually increases from C3 to C7 (Table 1).
Pedicles: Pedicle length was maximum at C3, minimum at C6; the pedicle height and width gradually increases from C3 to C7.(Table 2) Laminae: Laminae length gradually decreases from C3 to C7; but Lamina height was minimum at C3 and Maximum at C6; width of lamina was minimum at C5, maximum at C3.(Table 3) Spinous Process: Length of spinous process was maximum at C3, Minimum at C7.(Table 4)       Foramen transversorium: AP and transverse length of Foramen transversorium of both sides was measured; AP length of FT on RT side was maximum at C4 but on left side it was maximum at C6; Transverse length of FT on RT side was maximum at C7, it was also maximum at C7 on left side (Table 4).It is also useful during corpectomy procedure where removal of entire body is done to gain access to disc material, also for transcorporeal micro decompression (TCMD).TCMD procedure accesses the cervical spine from front of Neck.

DISCUSSION
The morphometry of cervical vertebral pedicles was studied by Kayalioglu et al. [12] In that study greatest pedicle length was at C3.In our present study pedicle length was maximum at C3 Minimum at C6 level .But pedicle width gradually increases from C3 to C6 level.Pedicle height was also gradually increases from C3 to C6 level.These dimensions were varied from previous studies [11,12].These may be due to geographical factors, food habits, and environmental conditions.
The pedicle dimensions will be useful for selecting the screw size in transpedicular screwing techniques [Abumi et al [13] ).They have spent their valuable time in these analyses.But there are variations in the dimensions due to life style changes, genetic makeup, geographic factors and also varies in the races (yusof et al [8]).Our present study will provide knowledge about the dimensions of sub axial vertebrae in south Indian population.In our present study transverse length of body was minimum at C3 maximum at C6 (Table 1).Body height was minimum at C4, maximum at C7(Table 1) .The morphometry of cervical vertebra which was studied by Gajendran Prabavathy et al [11] where maximum pedicle length was noted at C3, Minimum pedicle length was noted at C5, This was in variance with our present study.The Lamina dimensions are very important for laminotomy (where making hole in lamina to create more space for spinal cord), laminectomy where removal part all of lamina to reduce pressure on spinal cord & also in laminoplasty procedure [15,16,19,20].These are all decompression procedures frequently used for the treatment of cervical spondylosis, mylopathy, tumors of spinal medulla (wang et al [16]).In our present study the maximum lamina length was at C6, was minimum at C3; the maximum lamina height was at C3, minimum lamina height was at C7.According to Bazaldua et al [10] the length of spinous process was minimum at C3 and maximum at C7.In our present study spinous process length was minimum at C3, it gradually increases from C3 to C7 was maximum at C7. Spinous process dimensions are important for decompression procedures from behind.
According to Richa gupta et al [17] foramen transversorium AP length was minimum at C3,maximum at C6.Transverse length was minimum at C3, maximum at C5.In our present study AP length was minimum at C6,maximum at C4 and transverse length was minimum at C6,maximum at C7.These dimensions were varied from previous study.The dimensions of foramen Transversorium are very important for foraminotomy procedure where Intervertebral disc or a bony spur is pressing on a Nerve as it exits through the foramen, a foraminotomy may be done.This is making the opening of the foramen larger, so the Nerve can exist without being compressed.
factors and environmental conditions.These results will be helpful in spinal fixation surgeries, decompression surgeries and also useful for orthopaedicians to diagnose and interpret radiological images.

CONCLUSION
The dimensions of body and spinous process were increased from C3 to C6.But laminae length decrease gradually from C3 to C7.Pedicle length was gradually decreases from C3 to C6.But pedicle width and height gradually increases from c3 to c6.These results were varied with previous studies.This may be due to nutrition

International
Journal of Anatomy and Research, Int J Anat Res 2017, Vol 5(4.3):4740-45.ISSN 2321-4287 DOI: https://dx.doi.org/10.16965/ijar.2017.461 [1].The cervical curvature has its important functions.Due to fracture and disorders of cervical Spine serious damages may occur, approximately 5 to 10% of unconscious patients who come to emergency unit as a result of motor vehicle accidents or fall have a major injury to cervical spine.More Cervical spine fractures occur at 2 levels one at C1 -C2 level, other at C6 -C7 Level.Cervical Spine can be viewed as 3 columns: Anterior: Includes anterior longitudinal ligament, Anterior 2/3 of body.Middle: Includes posterior 1/3 of body & Posterior longitudinal ligament, IV discs.Posterior: Contains all bony elements pedicles, lamina, transverse process, spinous process [2].If one column is disrupted; other columns may provide sufficient stability to prevent spinal cord Injury.If 2 columns are disrupted, the spine may move as 2 separate units, increases the possibilities of spinal cord injury .Most of the injuries causes unstable spinal cord.In treatment of spinal cord instability and decompression of neurological structures, many procedures are followed like Kyphoplasty, Vertebroplasty, Vertebral column instrumentation and placement of Transpedicular Screws; The size and dimensions of various parts of vertebrae may vary one from another.It also varies among various population.The morphometric dimensions like vertebral body's Antero posterior(AP) length, Transverse(T) Length, Height, Foramen Transversorium's Length, breadth, width, Lamina length, width, Pedicle's length , width, length of spinous process of our study will be useful to spinal surgeons for their spinal fixation procedures.Many people spent their precious time in studying the dimensions of sub axial vertebrae.Our present study will provide knowledge about dimensions of cervical vertebrae in south Indian population.Sixty dry human sub axial vertebrae of unknown sex and age has been collected from Rajah Muthiah Medical College & Hospital, Annamalai Nagar, Chidambaram.Normal intact vertebras were only taken for the study.Damaged and fractured vertebras have been excluded.The dimensions of body, lamina, pedicle, spinous process, Foramen Transversorium were measured using spreading and gliding caliper.The measurements we observed were following: Body: AP length: Distance between anterior and posterior surface of body at midline (fig.1).Transverse length: Distance between two lateral surfaces of the vertebral body (fig.1).Height: Distance between superior & inferior borders of vertebral body at midline (fig.3).Pedicle: Length: Distance between the anterior limit of superior articular facet and posterior limit of the vertebral body(fig 2) Width: Distance between the medial & lateral borders(fig 2).Height: Distance between superior & inferior border of pedicle (fig 2) Lamina: Length: Distance between the spinous process and lateral border of superior articular process(fig 2) Height: Distance between superior & inferior borders of lamina (fig 2) Width: Distance between medial & lateral borders.(fig 2) Spinous process: Length: Distance from superior border to tip of the spinous process.(fig2) MATERIALS AND METHODS V.Ananthi, S.Umarani, V.Muniappan.VARIATIONS IN THE DIMENSIONS OF SUB AXIAL VERTEBRAE AND ITS CLINICAL SIGNIFICANCE.Foramen Transversorium: Anterio posterior and transverse diameter of Right & Left side has been measured(fig 1) Statistical analysis: Statistical analysis was done for each measurement.Mean and standard deviations were performed using SPSS Ver.20.

Fig
Fig. 3: Dimension of Body Height.
Bazaldua C.J.J et al[10]  study transverse length of body increases gradually from C3 to C7.According to Gajendran prabavathy et al[11]   body height was minimum at C3, maximum at C7.The body height dimensions were varied from Gajendren prabavathy et al[11]  study.Variations in the dimensions of body are important for many surgical procedures like Decompression Surgeries to remove disc or to remove bony spur which compresses spinal cord.

Table 1 :
Dimensions of Vertebral bodies.
V.Ananthi, S.Umarani, V.Muniappan.VARIATIONS IN THE DIMENSIONS OF SUB AXIAL VERTEBRAE AND ITS CLINICAL SIGNIFICANCE.

Table 5 :
Comparison of body dimensions with previous studies.

Table 6 :
Comparison of pedicle Dimensions.
.Ananthi, S.Umarani, V.Muniappan.VARIATIONS IN THE DIMENSIONS OF SUB AXIAL VERTEBRAE AND ITS CLINICAL SIGNIFICANCE.
These body dimensions were in concurrence with Ephrahim et al [9] study.InV