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Comparison of Cervical Spine Anatomy in Calves, Pigs and Humans

  • Sun-Ren Sheng,

    Affiliation Department of Orthopedic Surgery, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, China

  • Hua-Zi Xu,

    Affiliation Department of Orthopedic Surgery, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, China

  • Yong-Li Wang,

    Affiliation Department of Orthopedic Surgery, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, China

  • Qing-An Zhu,

    Affiliation Nan Fang Hospital of Southern Medical University, Guangzhou, China

  • Fang-Min Mao,

    Affiliation Department of Orthopedic Surgery, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, China

  • Yan Lin,

    Affiliation Department of Orthopedic Surgery, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, China

  • Xiang-Yang Wang

    Affiliation Department of Orthopedic Surgery, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, China


Background Context

Animals are commonly used to model the human spine for in vitro and in vivo experiments. Many studies have investigated similarities and differences between animals and humans in the lumbar and thoracic vertebrae. However, a quantitative anatomic comparison of calf, pig, and human cervical spines has not been reported.


To compare fundamental structural similarities and differences in vertebral bodies from the cervical spines of commonly used experimental animal models and humans.

Study Design

Anatomical morphometric analysis was performed on cervical vertebra specimens harvested from humans and two common large animals (i.e., calves and pigs).


Multiple morphometric parameters were directly measured from cervical spine specimens of twelve pigs, twelve calves and twelve human adult cadavers. The following anatomical parameters were measured: vertebral body width (VBW), vertebral body depth (VBD), vertebral body height (VBH), spinal canal width (SCW), spinal canal depth (SCD), pedicle width (PW), pedicle depth (PD), pedicle inclination (PI), dens width (DW), dens depth (DD), total vertebral width (TVW), and total vertebral depth (TVD).


The atlantoaxial (C1–2) joint in pigs is similar to that in humans and could serve as a human substitute. The pig cervical spine is highly similar to the human cervical spine, except for two large transverse processes in the anterior regions ofC4–C6. The width and depth of the calf odontoid process were larger than those in humans. VBW and VBD of calf cervical vertebrae were larger than those in humans, but the spinal canal was smaller. Calf C7 was relatively similar to human C7, thus, it may be a good substitute.


Pig cervical vertebrae were more suitable human substitutions than calf cervical vertebrae, especially with respect to C1, C2, and C7. The biomechanical properties of nerve vascular anatomy and various segment functions in pig and calf cervical vertebrae must be considered when selecting an animal model for research on the spine.


Due to the potential for infection, the limited supply of human cadavers, and the ethical concerns surrounding the use of human specimens, vertebrae from animal models, such as pigs [19], calves [1019], dogs [2027], sheep [2831] and deer [3234],have been widely used in spine research to replace human vertebrae. Several factors must be considered when choosing a model animal species, including size, cost, disc geometry, cellularity and biomechanics.

Several studies [4,7,15,18,35] have discussed the anatomy and biomechanics of pig and calf vertebrae, particularly in lumbar and thoracic vertebrae. However, a systematic quantitative comparison of anatomical data corresponding to pig, calf, and human cervical vertebrae has not been reported. In the current study, we evaluated the geometries of cervical vertebrae in two animal models and normalized these parameters for comparison against human cervical vertebrae. Through these comparisons, we assessed the appropriateness of utilizing pig and calf cervical vertebrae as human substitutes for in vitro and in vivo experiments.

Materials and Methods

Twelve one-year-old pig cervical spines (C0-T1) (weight, 60–80 kg) and twelve one-week-old calf cervical spines (C0-T1) (weight, 40–50 kg) were obtained from a local abattoir. Twelve human cervical spines (C0-T1) from adults between30 and 40 years of age (weight, 60–80 kg) were obtained from WenZhou Medical College. A spine specialist evaluated the human vertebrae to ensure that cervical syndrome and osteoporosis were not present. The WenZhou Medical College Ethics Committee reviewed and approved the study and waived the need for informed consent. The cervical spines were stored at -20°C prior to preparation and testing. All musculature and ligaments were carefully removed so that the underlying bony structures were not damaged.

Vernier calipers (Gaozhi_0–200, Shanghai, China; accuracy ±0.03 mm) and a protractor, both meeting international standards, were respectively used to take linear and angular measurements. The following anatomic parameters were measured directly from the surface of the spine specimens: vertebral body width (VBW), vertebral body depth (VBD), vertebral body height (VBH), spinal canal width (SCW), spinal canal depth (SCD), pedicle width (PW), pedicle depth (PD), pedicle inclination (PI), dens width (DW), dens depth (DD), total vertebral width (TVW), and total vertebral depth (TVD) (Table 1, Fig 1). Our sample size was consistent with previous similar studies [30,32,35,36]. Each measurement was repeated three times by two independent observers, and the mean value was recorded. All anatomic values are expressed as the mean ± standard deviation (SD). Differences among the calf, pig, and human spines were statistically analyzed using analysis of variance (ANOVA) followed by Dunnett’s test. P values less than 0.05 were considered significant.

Fig 1. Anatomical parameters.

(VBW) vertebral body width, (VBD) vertebral body depth, (VBH) vertebral body height, (SCW) spinal canal width, (SCD) spinal canal depth, (PW) pedicle width, (PH) pedicle height,(PI) pedicle inclination, (DD) dens depth, (DW) dens width, (TVD) total vertebral depth, and (TVW) total vertebral width.


Upper Cervical Vertebrae

There was no vertebral artery foramen around the atlas vertebra in the calf. Compared to the human atlas vertebra, the PI, DD and DW of the calf vertebra were larger, whereas the VBH and VBW were smaller. The calf atlas vertebra was similar to the human atlas vertebra in SCD and TVD. The odontoid process of the calf vertebra was a unique feature, and its length and width were greater than those of the human odontoid process (p<0.05) (approximately 1.7 and 2 times, respectively).

There were few differences in the atlas vertebral body and spinal canal between humans and pigs, but the pedicles of pigs were thicker than those of humans. The PI was greater in the pig upper cervical vertebrae. The pig cervical DD and DW were similar to those in humans (p>0.05). The pig SCD and SCW were larger than those in humans at C2 (p<0.05) (Table 2).

Table 2. The means and standard deviations of various anatomical dimensions of the atlantoaxial (C1-2) joints of calves, pigs and humans.

Middle and Lower Cervical Vertebrae

The pedicle angles in the middle and lower cervical vertebrae of calves had nearly the same profiles as those in humans. Compared to humans, the VBW and VBD of calf cervical vertebrae were larger, but the spinal canal was smaller (p<0.05). From C3–C7, the calf PW was 1 cm less than that in humans, whereas the PH was 1 cm larger. Compared to humans, the spinous process and transverse processes of calf vertebrae were shorter and more horizontal. From C3 to C7, the difference between human and calf vertebrae gradually decreased. Calf C7 was similar to human C7 in VBW, PI and PW (p>0.05).

Pig cervical vertebrae had larger VBWs than human cervical vertebrae, whereas pig vertebral PI and SCW were nearly the same as those of humans in the middle and lower cervical vertebrae. Similar VBD, VBH, PH, and PW were found between pigs and humans in the middle and lower cervical vertebrae (p>0.05). From C3–C7, the differences in SCD between pig and human cervical vertebrae decreased. There were two large transverse processes in the anterior regions of pig C4–C6 (S1 Table, Figs 26). C7 was nearly identical between pigs and humans.

Fig 2. Comparison of vertebral body width (mean ± stand deviation).

Fig 3. Comparison of vertebral body depth (mean ± stand deviation).

Fig 4. Comparison of vertebral body height (mean ± stand deviation).

Fig 5. Comparison of spinal canal properties (mean ± stand deviation).

Fig 6. Comparison of pedicle properties (mean ± stand deviation).


Cervical disease has become widespread due to lifestyle and environmental changes. With the development of internal fixation and surgical methods, an increasing number of spinal surgeons are participating in cervical spine research by testing new implants, spinal fusion techniques, and injury simulations. The majority of current research has utilized specimens derived from large mammals (e.g., sheep [29,30] and baboons [36]) to replace human cervical specimens. Differences exist in the cervical spines of humans and such mammals, although all of the mammals used to date possesss even cervical vertebrae. For example, baboons (Papio anubis) [36], which walk upright and are among the closest relatives to humans, have vertebrae with thinner pedicles, longer transverse processes, more prominent uncovertebral joints, and more horizontal spinous processes than humans. However, baboons are extremely rare and not easily obtained for research purposes. Therefore, to identify optimal animal models, we must assess the differences and similarities in the biomechanical properties of animal and human vertebrae. Additionally, we must consider species availability, cost, breeding ability and growth.

Calves and pigs are four-legged mammals with relatively easy-to-obtain cervical spines. In the present study, we evaluated one-year-old pigs weighing 60–80 kg and one-week-old calves weighing 40–50 kg because of their suitable size. Aerssens [37] compared bone composition, density and mechanical competence between humans and animals and suggested that pig bones were the most comparable to human bones. However, Aerssens [37] did not compare differences in morphology. Our current study addressed this deficiency by providing detailed morphological data that can be used in future research.

Calf C1-2 had a different morphology than human C1-2. The calf middle and lower cervical spine were large enough to test new implant systems; however, there were many differences between calf and human vertebrae.

Pig and human cervical vertebrae had similar anatomy, particularly the upper cervical vertebrae. The atlantoaxial joint (C1-2) in pigs was nearly identical to that in humans, particularly with respect to the odontoid process, which could be used to simulate dens fractures and surgical procedures. Cervical vertebrae widths and heights were nearly identical between pigs and humans (phase contrast in 0.1 cm). There was no significant difference in pedicle angle between pig and human cervical vertebrae, while the height and width of the pig pedicle were slightly larger. The pig cervical spine was large enough to test pedicle screws. The largest difference between pig and human middle and lower cervical vertebrae was the presence of two anterior transverse processes in pigs; these were located in the coronal area. The upper and lower vertebral transverse processes were connected, which might affect their biomechanics.

In conclusion, the pig atlantoaxial (C1-2) joint was anatomically identical to the human atlantoaxial joint and could therefore serve as a human substitute. Few differences existed between pig and human vertebrae with respect to the spinal canal, vertebral body, pedicle and articular process. While pig cervical vertebrae were found to have gross similarity to human cervical vertebrae, it must be noted that pigs possess two large transverse processes in the anterior region of the C4–C6 vertebral body. Pig cervical vertebrae were more similar to the human spine than to the calf spine, particularly with respect to C1, C2, and C7.

Several differences existed between humans and calves: 1. Calf cervical vertebrae were approximately 75% larger than those in humans; 2. the calf pedicle was thicker and the pedicle angle larger than those in humans; and 3. the width and depth of the calf odontoid bone were greater than those in humans. Calf C7 was relatively similar to human C7 and therefore may be a good substitute.

This current study is the first to compare cervical vertebrae anatomy between pigs, calves and humans. We present detailed and complete anatomical configuration data for pig and calf cervical spines. When considering these two animal models as human substitutes for in vitro and in vivo experiments, the biomechanical properties of their nerve vascular anatomies and functions across various spinal segments must be taken into account.

Supporting Information

S1 Table. Anatomical dimensions of the middle and lower cervical vertebrae.



This work was supported by grants from the Qianjiang Talents Project of Technology Office of Zhejiang Province (Grant No:2010R10075), the Natural Science Foundation of Zhejiang Province for Distinguished Young Scholars (Grant No: LR12H06001),the Science and Technology Bureau of Wenzhou City (Grant No: Y20100091) and the National Nature Foundation of China (Grant No. 81371988).

Author Contributions

Conceived and designed the experiments: XYW HZX. Performed the experiments: SRS. Analyzed the data: FMM YL. Contributed reagents/materials/analysis tools: YLW QAZ. Wrote the paper: SRS.


  1. 1. Bozkus H, Crawford NR, Chamberlain RH, Valenzuela TD, Espinoza A, Yüksel Z, et al. Comparative anatomy of the porcine and human thoracic spines with reference to thoracoscopic surgical techniques. Surg Endosc.2005;19:1652–65. pmid:16211439
  2. 2. Hakalo J, Pezowicz C, Wronski J, Bedzinski R, Kasprowicz M. Comparative biomechanical study of cervical spine stabilisation by cage alone, cage with plate, or plate-cage: a porcine model. J Orthop Surg (Hong Kong).2008;16:9–13.
  3. 3. Kouwenhoven JW, Smit TH, van der Veen AJ, Kingma I, van Dieen JH, Castelein RM. Effects of dorsal versus ventral shear loads on the rotational stability of the thoracic spine: a biomechanical porcine and human cadaveric study. Spine.2007;32:2545–50. pmid:17978652
  4. 4. Schmidt R, Richter M, Claes L, Puhl W, Wilke HJ. Limitations of the cervical porcine spine in evaluating spinal implants in comparison with human cervical spinal segments: a biomechanical in vitro comparison of porcine and human cervical spine specimens with different instrumentation techniques. Spine.2005;30:1275–82. pmid:15928552
  5. 5. Tai CL, Hsieh PH, Chen WP, Chen LH, Chen WJ, Lai PL. Biomechanical comparison of lumbar spine instability between laminectomy and bilateral laminotomy for spinal stenosis syndrome—an experimental study in porcine model. BMC Musculoskelet Disord.2008;9:84. pmid:18547409
  6. 6. Yazici M, Pekmezci M, Cil A, Alanay A, Acaroglu E, Oner FC. The effect of pedicle expansion on pedicle morphology and biomechanical stability in the immature porcine spine. Spine.2006;31:E826–9. pmid:17047529
  7. 7. Yingling VR, Callaghan JP, McGill SM. (1999) The porcine cervical spine as a model of the human lumbar spine: an anatomical, geometric, and functional comparison. J Spinal Disord 12:415–23. pmid:10549707
  8. 8. Busscher I, Ploegmakers JJ, Verkerke GJ, Veldhuizen AG. Comparative anatomical dimensions of the complete human and porcine spine. Eur Spine J.2010;19:1104–14. pmid:20186441
  9. 9. Busscher I, van der Veen AJ, van Dieen JH, Kingma I, Verkerke GJ, Veldhuizen AG. In vitro biomechanical characteristics of the spine: a comparison between human and porcine spinal segments. Spine (Phila Pa 1976).2010;35:E35–42.
  10. 10. Cotterill PC, Kostuik JP, D'Angelo G, Fernie GR, Maki BE. An anatomical comparison of the human and bovine thoracolumbar spine. J Orthop Res.1986;4:298–303. pmid:3734937
  11. 11. Demarteau O, Pillet L, Inaebnit A, Borens O, Quinn TM. Biomechanical characterization and in vitro mechanical injury of elderly human femoral head cartilage: comparison to adult bovine humeral head cartilage. Osteoarthritis Cartilage.2006;14:589–96. pmid:16478669
  12. 12. Demers CN, Antoniou J, Mwale F. Value and limitations of using the bovine tail as a model for the human lumbar spine. Spine 29:2793–9. pmid:15599281
  13. 13. Lei W, Wu Z. (2006) Biomechanical evaluation of an expansive pedicle screw in calf vertebrae. Eur Spine J.2004;15:321–6. pmid:15864667
  14. 14. Lim TH, An HS, Hong JH,Ahn JY, You JW, Eck J, et al. Biomechanical evaluation of anterior and posterior fixations in an unstable calf spine model. Spine.1997;22:261–6. pmid:9051887
  15. 15. Riley LH 3rd, Eck JC, Yoshida H, Koh YD, You JW, Lim TH. A biomechanical comparison of calf versus cadaver lumbar spine models. Spine.2004;29:E217–20. pmid:15167671
  16. 16. Shirado O, Zdeblick TA, McAfee PC, Warden KE. Biomechanical evaluation of methods of posterior stabilization of the spine and posterior lumbar interbody arthrodesis for lumbosacral isthmic spondylolisthesis. A calf-spine model. J Bone Joint Surg Am.1991;73:518–26. pmid:2013591
  17. 17. Wilke HJ, Krischak S, Claes L. Biomechanical comparison of calf and human spines. J Orthop Res.1996;14:500–3. pmid:8676264
  18. 18. Wilke HJ, Krischak ST, Wenger KH, Claes LE. Load-displacement properties of the thoracolumbar calf spine: experimental results and comparison to known human data. Eur Spine J.1997;6:129–37. pmid:9209882
  19. 19. Wittenberg RH, Shea M, Edwards WT, Swartz DE, White AA 3rd, Hayes WC. A biomechanical study of the fatigue characteristics of thoracolumbar fixation implants in a calf spine model. Spine.1992;17:S121–8. pmid:1631711
  20. 20. Ettema AM, Zhao C, An KN, Amadio PC. Comparative anatomy of the subsynovial connective tissue in the carpal tunnel of the rat, rabbit, dog, baboon, and human. Hand (N Y).2006;1:78–84.
  21. 21. Gomez M, Freeman L, Jones J, Lanz O, Arnold P. Computed tomographic anatomy of the canine cervical vertebral venous system. Vet Radiol Ultrasound.2004;45:29–37. pmid:15005358
  22. 22. Gregory CR, Cullen JM, Pool R, Vasseur PB. The canine sacroiliac joint. Preliminary study of anatomy, histopathology, and biomechanics. Spine.1986;11:1044–8. pmid:3576343
  23. 23. Koehler CL, Stover SM, LeCouteur RA, Schulz KS, Hawkins DA. Effect of a ventral slot procedure and of smooth or positive-profile threaded pins with polymethylmethacrylate fixation on intervertebral biomechanics at treated and adjacent canine cervical vertebral motion units. Am J Vet Res.2005;66:678–87. pmid:15900950
  24. 24. Panjabi MM, Pelker R, Crisco JJ, Thibodeau L, Yamamoto I. Biomechanics of healing of posterior cervical spinal injuries in a canine model. Spine.1988;13:803–7. pmid:3194789
  25. 25. Sato F, Yanohara K, Takenouchi S, Suzuki Y, Hisa Y, Hyuga M. Mechanical properties of the laryngeal muscles and biomechanics of the glottis in the dog. Nippon Jibiinkoka Gakkai Kaiho.1982;85:951–6. pmid:7143147
  26. 26. Shahar R, Milgram J. Biomechanics of tibial plateau leveling of the canine cruciate-deficient stifle joint: a theoretical model. Vet Surg.2006;35:144–9. pmid:16472294
  27. 27. Takeuchi T, Abumi K, Shono Y, Oda I, Kaneda K. Biomechanical role of the intervertebral disc and costovertebral joint in stability of the thoracic spine. A canine model study. Spine.1999;24:1414–20. pmid:10423785
  28. 28. Kandziora F, Pflugmacher R, Scholz M, Schnake K, Lucke M, Schröder R, et al. Comparison between sheep and human cervical spines: an anatomic, radiographic, bone mineral density, and biomechanical study. Spine.2001;26:1028–37. pmid:11337621
  29. 29. Wilke HJ, Kettler A, Claes LE. Were sheep spines a valid biomechanical model for human spines? Spine.1997;22:2365–74.
  30. 30. Wilke HJ, Kettler A, Wenger KH, Claes LE. Anatomy of the sheep spine and its comparison to the human spine. Anat Rec.1997;247:542–55. pmid:9096794
  31. 31. Zrunek M, Happak W, Hermann M, Streinzer W. Comparative anatomy of human and sheep laryngeal skeleton. Acta Otolaryngol.1998;105:155–62.
  32. 32. Kumar N, Kukreti S, Ishaque M, Mulholland R. Anatomy of deer spine and its comparison to the human spine. Anat Rec.2000;260:189–203. pmid:10993955
  33. 33. Kumar N, Kukreti S, Ishaque M, Sengupta DK, Mulholland RC. Functional anatomy of the deer spine: an appropriate biomechanical model for the human spine? Anat Rec.2000;266:108–17.
  34. 34. Seel EH, Davies EM. A biomechanical comparison of kyphoplasty using a balloon bone tamp versus an expandable polymer bone tamp in a deer spine model. J Bone Joint Surg Br.2007;89:253–7. pmid:17322448
  35. 35. Sheng SR, Wang XY, Xu HZ, Zhu GQ, Zhou YF. Anatomy of large animal spines and its comparison to the human spine: a systematic review. Eur Spine J.2010;19:46–56. pmid:19876658
  36. 36. Tominaga T, Dickman CA, Sonntag VK, Coons S. Comparative anatomy of the baboon and the human cervical spine. Spine.1995;20:131–7. pmid:7716616
  37. 37. Aerssens J, Dequeker J, Mbuyi-Muamba JM. Bone tissue composition: biochemical anatomy of bone. Clin Rheumatol.1994;13:54–62.