Computed Tomographic and Morphometric Study of Cervical Vertebrae in Healthy White New Zealand Rabbit (Oryctolagus Cuniculus)

Document Type : Anatomy- Biochemistry

Authors

1 Department of Surgery and Radiology, Faculty of Veterinary Medicine University of Tehran, Tehran, Iran

2 Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.

3 Department of Internal Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

Abstract

BACKGROUND:
Nowadays, use of rabbits in research as laboratory animals is quite prevalent, however imaging modal-ities for producing anatomical illustrations are rare. Computed tomography (CT) is a nonaggressive modality which provides more anatomical detailed data.
OBJECTIVES:
This study aimed to create a plenary and exact deliniation and morphometric evaluation of cervical ver-tebrae in rabbits.
METHODS:
A CT scanner with two detectors was used in this study. Several parameters were measured in 10 healthy, adult female white New Zealand rabbits and the results were evaluated.
RESULTS:
Some parameters including VBH, SCH, PDL, PDW, VBL, EPH, and EPW had no significant difference through cervical vertebrae but other parameters such as SPH, TPL, TPW, SPA, and TPA were significantly different. In the fifth cervical vertebrae, transverse process had three parts, as well as having a big transverse foramen while in the sixth vertebra, transverse process resembled a wide plate
CONCLUSIONS:
VBH had an invariable measure from the second to seventh cervical vertebrae. SPH had an invariable measure from the second cervical vertebra to the sixth one, then once more it increased at the location of the seventh cervical vertebra and was invariable up to the first thoracic vertebra. This study presents a complete and precise description and morphometric evaluation of cervical vertebrae in rabbits using CT scan. As an important feature of this study, no specimen was killed and anatomical studies were performed using the CT scan technique .

Keywords


Article Title [فارسی]

مطالعه سی تی اسکن و ارزیابی مورفومتریک مهره های گردنی در خرگوش نیوزیلندی سالم

Authors [فارسی]

  • بنفشه شاطری امیری 1
  • سارنگ سروری 1
  • امید زهتاب ور 2
  • امیر رستمی 3
  • ریحانه سفلایی 1
2 گروه علوم پایه دانشکده دامپزشکی دانشگاه تهران، ایران
Abstract [فارسی]

زمینه مطالعه: امروزه استفاده از خرگوش‌ها در تحقیقات به عنوان حیوان آزمایشگاهی بسیار رایج است ولی اطلاعات کمی در مورد به آناتومی رادیوگرافی این حیوانات وجود دارد. سی تی اسکن یک روش تشخیصی غیرتهاجمی است که اطلاعات آناتومی جزئی‌تر و دقیق‌تری در اختیار قرار می‌دهد.
هدف: هدف از این مطالعه توصیف کامل و دقیق آناتومی مهره‌های گردنی و ارزیابی مورفومتری این مهره‌ها درخرگوش به وسیله روش سی تی اسکن است.
روش کار: در این مطالعه از دستگاه سی تی اسکن دو آشکارسازه استفاده شده است و چندین پارامتر در تصاویر دو بعدی در10 خرگوش سالم، بالغ، ماده سفید نیوزیلندی اندازه‌گیری شدند و نتایج حاصل مورد ارزیابی قرار گرفتند.
نتایج: اندازه برخی پارامترها از قبیل VBH, SCH, PDL, PDW, VBL, EPH و EPW در تمامی مهره‌های گردنی تفاوت معنی‌داری نداشتند، ولی اندازه سایر پارامترها از قبیل SPH, TPL, TPW, SPA و TPA دارای تفاوت معنی‌دار بود. در پنجمین مهره گردنی زائده عرضی سه قسمتی بود و دارای سوراخ عرضی بزرگ بود. در ششمین مهره، زائده عرضی شبیه یک صفحه پهن بود.
نتیجه گیری نهایی: پارامتر VBH بین مهره‌های دوم تا هفتم گردنی اندازه ثابتی داشته است. پارامتر SPH نیز دارای اندازه ثابت بین مهره‌های دوم تا ششم گردنی است و در محل هفتمین مهره گردنی دارای افزایش اندازه بود و سپس تا اولین مهره سینه‌ای اندازه ثابتی داشته است. این مطالعه شامل توصیف دقیق و کاملی از مهره‌های گردنی و نیز ارزیابی مورفومتری این مهره‌ها در خرگوش به وسیله سی تی اسکن است. شاخص مهم این مطالعه عدم کشته شدن هیچ یک از نمونه‌ها و مطالعه آناتومی و مورفومتری مهره‌های گردنی به وسیله تصویربرداری سی تی اسکن است.

Keywords [فارسی]

  • کالبدشناسی
  • مهره‌های گردنی
  • سی تی اسکن
  • مورفومتری
  • خرگوش

Introduction


Nowadays, use of rabbits in research as laboratory animals is quite prevalent, however imaging modalities for producing anatomical illustrations are rare. The vertebral column is one of the most important parts of the skeleton of the rabbits that can be injured easily. Diagnostic imaging techniques are very useful in finding vertebral column injuries, however anatomical data (morphological and morphometric) are needed for this purpose. The cervical region is one of the important parts of vertebral column, consisting seven vertebrae (Worth, 2019; Riggs, 2016; Zehtabvar et al., 2015).

Computed tomography (CT) scan is a nonaggressive modality which provides more detailed data for the evaluation of vertebral column and is a good diagnostic aid for different skeletal and neurological diseases. An accurate diagnosis of abnormalities requires sufficient knowledge around normal situation of these structures.

CT scan is one of the most practical diagnostic methods used in small animal orthopedic purposes. In 2010, Sheng and colleagues evaluated vertebral columns of large animals and compared them with that of human (Sheng, et al., 2010). Jeffcott et al. (1979) evaluated anatomical radiography of thoracic and lumbar vertebra in horses. Furthermore, Cotterill et al. (1986) compared thoracic- lumbar vertebrae of cows with those of humans. Our study was based on the measurements of vertebrae and evaluation done on 2D and 3D CT scan. For many reasons, there is a possibility of traumatic injury to the spinal canal and intervertebral disc and these factors may contribute to the poor function of vertebral column. Nowadays, diagnostic imaging methods which are in use for numerous purposes are one of the best ways of evaluating the organs of body. These methods are also used for imaging the laboratory animals such as rabbits. One of these methods is CT scan which is remarkably useful for skeletal evaluations (Varga, 2014). Using CT scan, Zotti, Banzato, and Cozzi (2009) evaluated the anatomy of the neck, thorax, and abdomen in four rabbits (two males and two females). Van Caelenberg et al. (2010) evaluated the skull and the related soft tissues in rabbit with CT scan. These researchers reported that continuous growth of the teeth in rabbits predisposed them to dental diseases to which cheek teeth are mostly prone. In 2012, De Rycke et al. declared that dental disease is very common in rabbits, and radiographic techniques are useful in the diagnosis of these diseases. On the other hand, they displayed that because of the small size of skull in rabbits and superimposition of structures in radiographic images, CT could be a better modality for the evaluation of skull and teeth. They further stated that micro CT has higher quality though they are expensive. According to their reports, like Helical CT, micro CT provides lower soft tissue contrast than the CT technique (Van Caelenberg, et al., 2010). CT is one of the fastest and accurate methods for the study of vertebral columns in small animals. CT scan is also regarded as one of the best methods for topographic studies. While some use this technique in their anatomical studies, some others prefer ultrasonography and radiography. One of the advantages of these techniques is the investigation of anatomical structures in live animals (Zehtabvar, et al., 2014, 2016, 2018, 2019).

In contrast to the frequent uses of rabbits in different areas of study, the normal structure of different parts of cervical vertebrae especially normal morphometric parameters have not been studied by CT. In this study, a thorough description and morphometric evaluation of cervical vertebrae was presented in rabbits using CT scan, and several parameters were measured in cervical vertebrae.

Materials and Methods

Animals

Ten adult female white New Zealand rabbits (Oryctolagus cuniculus) with an average body weight of 1.95±0.5 kg were evaluated in this study. All rabbits were in good health.

Computed Tomographic Study

 Rabbits were first anesthetized using ketamine (35 mg/kg body weight, IM) and xylazine (4 mg/kg body weight, IM) (Carpenter, Marion, 2017).

A CT Scanner with two detectors (SOMATOM Spirit, Siemens, Germany) was used in this study. Images were taken in ventral recumbency. The images were taken as transverse and perpendicular to vertebral column and in 2-mm slices. Technical factors for CT were as follows: rotation time, 1 s; slice thickness, 1 mm; reconstruction interval, 0.5–1 mm; pitch, 1; X-ray tube potential, 120 kV; and X-ray tube current, 130 mA. In images produced in CT scan, several structures of cervical vertebrae were evaluated and different parts were named. For evaluating each part, proper window level (WL) and window width (WW) were chosen for the evaluation of bone window and thorax (chest) window.

Morphometric Study

 Morphometric mensuration of CT images was done with Syngo MMWP VE40A software. The measured parameters are shown in Tables 1-3. The results of measured parameters were analyzed by SPSS version 16.0 (SPSS Inc. Chicago, IL. USA). Paired sample t test was used to compare the values of means (P>0.05). Due to the structural characteristics of some vertebrae, some parameters were not measured in the cases referred to in the tables.

 

 

Table 1.Anatomical parameters

        
  

Description

  
  

Abbreviation*

  
  

Parameter

  

Distance between the base of vertebra to   vertebral canal in transverse view

VBH

Vertebral body height

Distance between base of spinous process to   apex of process in sagittal view

SPL

Spinous process length

Distance between base of spinous process to   apex of process in transverse view

SPH

Spinous process height

Distance between the base of transverse   process to extremity of process in transverse view

TPL

Transverse process   length

Distance between left extremity of process to   right extremity in transverse view

TPW

Transverse process width

The angle between spinous process with   horizontal line in sagittal view

SPA

Spinous process angle

The angle between transverse process with   horizontal line in transverse view

TPA

Transverse process angle

Distance between proximal extremity of   vertebral canal to distal extremity of vertebral canal in transverse view

SCD

Spinal canal depth

Distance between left extremity of vertebral   canal to right extremity of vertebral canal in transverse view

SCW

Spinal canal width

Distance between proximal extremity of   pedicle to distal extremity in transverse view

PDL

Pedicle length

The width of pedicle in transverse view

PDW

Pedicle width

The length of vertebral body in sagittal view

VBL

Vertebral body length

The width of end plate in transverse view

EPW

Endplate width

The height of end plate in transverse view

EPH

Endplate height

       

*Notes about abbreviations: in rabbits like other domestic animal, atlas has no prominent spinous process and also because of the presence of wing instead of transverse process, this parameter is named as WPL and also for transverse process width in this vertebra, WPW is used instead of TPW. In rabbits like other animals, atlas has no prominent pedicle and endplate. In the first to sixth cervical vertebra in sagittal view, because of the small size of spinous process, in this vertebrae SPA was unmeasurable.

 

Table 2.Computed tomographic measurements of cervical vertebrae of rabbit (Mean ± SD in cm anddegree*)

VBH

SPH

TPL

WPL(C1, S)

TPW

WPW(C1, S)

SPA*

TPA*

WPA(C1,   S)

Cervical vertebrae

-

-

1±0.07b

2.7±0.08a

-

7.9±0.4a

C1

0.3±0.04a

0.6±0.05a

0.4±0.04a

1.2±0.06b

-

29.3±0.9b

C2

0.3±0.01a

0.3±0.03a

0.5±0.04a

1.4±0.1b

-

24.1±0.7b

C3

0.3±0.02a

0.3±0.03a

0.6±0.06a

1.6±0.2b

-

24±0.3b

C4

0.3±0.02a

0.4±0.06a

0.7±0.06a

1.9±0.08c

-

13.6±5.06c

C5

0.3±0.03a

0.4± 0.1a

0.7±0.04a

1.9±0.08c

-

11±6.06c

C6

0.3±0.04a

0.9±0.2ba

0.7±0.05a

2±0.1c

69.5±0.5a

12.8±0.5c

C7

The different letters (a,b,c) in each column, represent significant difference between vertebrae (n=10, P<0/05)

 

Table 3. Computed tomographic measurements of cervical vertebrae of rabbit (Mean ± SD in cm anddegree*)

SCH

SCW

PDL

PDW

VBL

EPW

EPH

Cervical vertebrae

0.5±0.05a

1±0.05a

-

-

-

-

-

C1

0.5±0.06a

0.5±0.05b

0.5±0.05a

0.2±0.04a

1±0.6a

0.6±0.3a

0.3±0.01a

C2

0.4±0.02a

0.5±0.04b

0.3±0.07a

0.2±0.03a

0.9±0.05a

0.7±0.04a

0.2±0.006a

C3

0.4±0.08a

0.5±0.06b

0.3±0.06a

0.3±0.04a

0.8±0.04a

0.7±0.05a

0.3±0.01a

C4

0.4±0.04a

0.6±0.05b

0.3±0.05a

0.3±0.02a

0.8±0.06a

0.7±0.07a

0.3±0.03a

C5

0.4±0.07a

0.6±0.03b

0.4±0.08a

0.4±0.04a

0.8±0.12a

0.6±0.07a

0.3±0.04a

C6

0.4±0.04a

0.6±0.02b

0.4±0.08a

0.4±0.04a

0.8±0.06a

0.7±0.1a

0.3±0.05a

C7

The different letters (a,b) in each column represent significant difference between vertebrae (n=10, P<0/05)

 

Results


Morphological Results

Atlas (C1)- Vertebral body and spinous process were not present in this vertebra, and transverse process changed to two wide horizontal wings (Figure 1). Atlantal fossa was in both right and left parts of ventral surface of atlas wings. Furthermore, in cranial part of wing, alar notch was observed and in the caudal part of wing, there were transverse foramens (Figure 1).

Axis (C2) - This vertebra had a slender spinous process which was located dorsally and met the arch of atlas. In cranial extremity of this vertebra in rabbits, there was cranial articular process which becomes dense and lies in fovea dentis of atlas. Dens in rabbits was round and filamentary and was located cranioventrally and continued to ventral surface of atlas (Figures 1, 2, 3).

Typical cervical vertebrae (C3, C4, C5) - In C3 and C4 in rabbits, transverse processes had two parts. Spinous process in these vertebrae was short and transverse process was seen clearly. In C5, transverse process had three parts, as well as having a big transverse foramen (Figures 3, 4, 5).

Sixth cervical vertebra (C6) - In C6, transverse process had three parts, but its two ventral portions had a distinct wide plate (Figures 6 and 8).

Seventh cervical vertebra (C7) - In C7, spinous process was a little higher than that in other cervical vertebrae. Furthermore, caudal part of the body in each side had an articular surface for rib articulation and this vertebra had a short body. Spinous process in C7 was more prominent (Figure 7).

Morphometric Results

 The results of measurements and statistical analysis are shown in Tables 2 and 3. Significant or non-significant differences in measured parameters are shown in Tables 2 and 3.

VBH had an invariable measure from C2 to C7. SPHhad an invariable measure from C2 to C6, then again it increased at C7. TPL was the longest in C1 and decreased at C2 and was invariable up to the location of C7. TPW was the widest in C1 and then it decreased at C2 and was invariable up to C4. It once more increased at C5 and was invariable up to the location of C7. TPA was the lowest at the location of C1. It increased at C2 and was invariable up to C4, then again it decreased at C5 and was invariable up to C7. SCWwas the widest in atlas between all cervical vertebrae, then it was invariable from C2 up to C7. PDL had different measurements from C2 up to C7. PDW had an invariable measure from C2 up to C7. VBL had different measures from C2 up to C7. EPW had different measures from C2 up to C7, and EPH had an invariable measure from C2 up to the location of C7. SPA was measured just in C7 and was not compared with that of other vertebrae.