• 1. Shores A, Tepper LC. A modified ventral approach to the atlantoaxial junction in the dog. Vet Surg 2007;36:765770.

  • 2. Beaver DP, Ellison GW, Lewis DD, et al. Risk factors affecting the outcome of surgery for atlantoaxial subluxation in dogs: 46 cases (1978–1998). J Am Vet Med Assoc 2000;216:11041109.

    • Search Google Scholar
    • Export Citation
  • 3. Denny HR, Gibbs C, Waterman A. Atlantoaxial subluxation in the dog: a review of thirty cases and an evaluation of treatment by lag screw fixation. J Small Anim Pract 1998;29:3747.

    • Search Google Scholar
    • Export Citation
  • 4. McCarthy RJ, Lews DD, Hosgood G. Atlantoaxial luxation in dogs. Compend Contin Educ Pract Vet 1995;17:215226.

  • 5. Thomas WB, Sorjonen DC, Simpson ST. Surgical management of atlantoaxial subluxation in 23 dogs. Vet Surg 1991;20:409412.

  • 6. Geary JC, Oliver JE, Hoerlein BF. Atlantoaxial subluxation in the canine. J Small Anim Pract 1967;8:577582.

  • 7. Parry AT, Upjohn MM, Schlegl K, et al. Computed tomography variations in morphology of the canine atlas in dogs with and without atlantoaxial subluxation. Vet Radiol Ultrasound 2010;51:596600.

    • Search Google Scholar
    • Export Citation
  • 8. Watson AG, de Lahunta A. Atlantoaxial subluxation and absence of transverse ligament of the atlas in a dog. J Am Vet Med Assoc 1989;195:235237.

    • Search Google Scholar
    • Export Citation
  • 9. Downey RS. An unusual cause of tetraplegia in a dog. Can Vet J 1967;8:216217.

  • 10. Zaki FA. Odontoid process dysplasia in a dog. J Small Anim Pract 1980;21:227234.

  • 11. Johnson SG, Hulse DA. Odontoid dysplasia with atlantoaxial instability in a dog. J Am Anim Hosp Assoc 1989;25:400404.

  • 12. Ladds P, Guffy M, Blauch B, et al. Congenital odontoid process separation in two dogs. J Small Anim Pract 1971;12:463471.

  • 13. Forterre F, Precht C, Riedinger B, et al. Biomechanical properties of the atlantoaxial joint with naturally-occurring instability in a toy breed dog. Vet Comp Orthop Traumatol 2015;28:355358.

    • Search Google Scholar
    • Export Citation
  • 14. Takahashi F, Hakozaki T, Kanno N, et al. Evaluation of the dens-to-axis length ratio and dens angle in toy breed dogs with and without atlantoaxial instability and in healthy Beagles. Am J Vet Res 2017;78:14001405.

    • Search Google Scholar
    • Export Citation
  • 15. Warren-Smith CM, Kneissl S, Benigni L, et al. Incomplete ossification of the atlas in dogs with cervical signs. Vet Radiol Ultrasound 2009;50:635638.

    • Search Google Scholar
    • Export Citation
  • 16. Owen MC, Davis SH, Worth AJ. Imaging diagnosis — traumatic myelopathy in a dog with incomplete ossification of the dorsal lamina of the atlas. Vet Radiol Ultrasound 2008;49:570572.

    • Search Google Scholar
    • Export Citation
  • 17. Watson AG, Evans HE, de Lahunta A. Ossification of the atlas-axis complex in the dog. Anat Histol Embryol 1986;15:122138.

  • 18. Evans HE. The skeleton. In: Miller's anatomy of the dog. 3rd ed. Philadelphia: WB Saunders Co, 1993;166170.

  • 19. Currarino G, Rollins N, Diehl JT. Congenital defects of the posterior arch of the atlas: a report of seven cases including an affected mother and son. Am J Neuroradiol 1994;15:249254.

    • Search Google Scholar
    • Export Citation
  • 20. Gangopadhyay S, Aslam M. Posterior arch defects of the atlas: significance in trauma and literature review. Eur J Emerg Med 2003;10:238240.

    • Search Google Scholar
    • Export Citation
  • 21. Schulze PJ, Buurman R. Absence of the posterior arch of the atlas. AJR Am J Roentgenol 1980;134:178180.

  • 22. Schrödel MH, Braun V, Stolpe E, et al. Coincidental deficiency of the posterior arch of the atlas and thalassaemia minor: possible pitfalls in a trauma victim. Emerg Med J 2005;22:526528.

    • Search Google Scholar
    • Export Citation
  • 23. Sharma A, Gaikwad SB, Deol PS, et al. Partial aplasia of the posterior arch of the atlas with an isolated posterior arch remnant: findings in three cases. Am J Neuroradiol 2000;21:11671171.

    • Search Google Scholar
    • Export Citation
  • 24. O'Sullivan AW, McManus F. Occult congenital anomaly of the atlas presenting in the setting of acute trauma. Emerg Med J 2004;21:639640.

    • Search Google Scholar
    • Export Citation
  • 25. Rivero MA, Vázquez JM, Gil F, et al. CT-soft tissue window of the cranial abdomen in clinically normal dogs: an anatomical description using macroscopic cross-sections with vascular injection. Anat Histol Embryol 2009;38:1822.

    • Search Google Scholar
    • Export Citation
  • 26. Sogo M, Ikebe K, Yang Tsung-Chieh, et al. Assessment of bone density in the posterior maxilla based on Hounsfield units to enhance the initial stability of implants. Clin Implant Dent Relat Res 2012;14:e183e187.

    • Search Google Scholar
    • Export Citation
  • 27. Stalin C, Gutierrez-Quintana R, Faller K, et al. A review of canine atlantoaxial joint subluxation. Vet Comp Orthop Traumatol 2015;28:18.

    • Search Google Scholar
    • Export Citation
  • 28. Schulz KS, Waldron DR, Fahie M. Application of ventral pins and polymethylmethacrylate for the management of atlantoaxial instability - results in nine dogs. Vet Surg 1997;26:317325.

    • Search Google Scholar
    • Export Citation
  • 29. Hoerlein BF, Gage ED. Hydrocephalus. In: Canine neurology. 3rd ed. Philadelphia: WB Saunders Co, 1978;733760.

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Epidemiological and morphological characteristics of incomplete ossification of the dorsal neural arch of the atlas in dogs with atlantoaxial instability

Fumitaka Takahashi DVM1,2, Takaharu Hakozaki DVM, PhD3, Shigenori Kouno DVM4, Shuji Suzuki DVM, PhD5, Asaka Sato DVM, PhD6, Nobuo Kanno DVM, PhD7, Yasuji Harada DVM, PhD8, Shinya Yamaguchi DVM, PhD9,10, and Yasushi Hara DVM, PhD11
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  • 1 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
  • | 2 YPC Tokyo Animal Orthopaedic Surgery Hospital, 7-1-13 Oojima, Koutou-ku, Tokyo, 136-0072, Japan.
  • | 3 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
  • | 4 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
  • | 5 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
  • | 6 Azabu University Veterinary Teaching Hospital, 1-17-71 Fuchinobe, Chuou-ku, Sagamihara-shi, Kanagawa, 252-5201, Japan.
  • | 7 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
  • | 8 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
  • | 9 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
  • | 10 YPC Tokyo Animal Orthopaedic Surgery Hospital, 7-1-13 Oojima, Koutou-ku, Tokyo, 136-0072, Japan.
  • | 11 Division of Veterinary Surgery, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.

Abstract

OBJECTIVE To retrospectively evaluate the epidemiological and morphological features and outcome of surgical treatment of incomplete ossification of the dorsal neural arch of the atlas (IODA) in dogs with atlantoaxial instability (AAI).

ANIMALS 106 AAI-affected dogs that underwent ventral fixation of the atlantoaxial joint.

PROCEDURES Medical records and CT images for each dog were reviewed. Dogs were allocated to 1 of 2 groups on the basis of the presence or absence of IODA or of dens abnormalities (DAs) in CT images.

RESULTS Of the 106 dogs with AAI, 75 had and 31 did not have IODA; 70 had and 36 did not have DAs. Incomplete ossification was present in the cranialmost, central, or caudalmost portion of the dorsal neural arch of the atlas in 59, 39, and 28 dogs, respectively; 2 or 3 portions were affected in 29 and 11 dogs, respectively. The mean CT value (in Hounsfield units) for the midline of the dorsal neural arch of the atlas in dogs with IODA was significantly lower than that for the same site in the dogs without IODA. The mean age at surgery for dogs with central IODA was significantly higher than that of the non-IODA group. The severity of spinal cord injury before or after atlantoaxial ventral fixation did not differ between the IODA and non-IODA groups.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that concomitant DAs or IODA is common in dogs with AAI. In dogs with incomplete ossification in the central part of the dorsal neural arch of the atlas, surgical treatment of AAI generally occurs at a middle to advanced age.

Contributor Notes

Address correspondence to Dr. Takahashi (takataka.pc1138@gmail.com).