Spondylosis deformans (eg, spinal osteophytosis and spondylosis) is a noninflammatory osteophytic reaction associated with cartilaginous joints of the vertebral column. The condition is common in dogs, reportedly1–3 affecting 17.8% to 32.8% of dogs if the diagnosis is made on the basis of radiographs alone and 61% to 75% of dogs if diagnosis is made on the basis of necropsy examination. The German Shepherd Dog, Boxer, Cocker Spaniel, and Airedale Terrier are breeds suspected of having a predisposition for developing spondylosis deformans.2,4–6
Different sites in the vertebral column are associated with different frequencies of spondylosis. Cross-sectional comparative analysis of dogs in England, Sweden, and the United States revealed that joints at L2-3 and L7-S1 were most frequently affected, with other areas of high incidence centered around the midthoracic portion of the vertebral column (ie, T4 through T6), at the T9-10 disk space, and in the midlumbar portion of the vertebral column.2 In a study7of female Beagles, the L1 through L6 disk spaces and C6-7 disk space had the highest frequency of spondylosis.
Given that development of spondylosis deformans is ubiquitous among humans and dogs, the underlying pathophysiologic features and clinical importance of the condition have been investigated in both species. Osteophyte formation is thought to be initiated by abnormalities at the site of attachment of peripheral annular fibers to the vertebral endplate.8,9 Weakened disk-to-endplate attachments lead to annular tears and result in small ventral or ventrolateral disk herniations. The combination of annular tearing and small-volume disk herniation is likely the cause of spondylosis.1,7,9,10 Although spondylosis may result in nerve root impingement and meningeal irritation when it develops on the dorsal aspect of vertebrae, the clinical importance of vertebral column osteophytes in dogs is generally regarded as small.2,7
In humans, evidence suggests that there are shared pathophysiologic associations among development of spondylosis deformans, degeneration of the nucleus pulposus, and annular hypertrophy. Endplate attachment abnormalities that drive development of spondylosis can also incite nucleus pulposus degeneration via impairment of disk nutrition and generation of stress forces.9,11,12 Annular tears responsible for inciting spondylosis deformans may also result in annular hypertrophy, a finding that has been reported1,10 in dogs. In veterinary medicine, whether an association exists between development of spondylosis deformans and clinically apparent IVDD has been questioned.2,13,14 Results of earlier studies,1,15 however, indicate that there are intrasegmental correlations between the location of sites of type II disk herniation and spondylosis deformans in dissected vertebral columns of dogs.
The purpose of the retrospective case series reported here was to investigate whether spondylosis deformans was associated with clinical signs of IVDD in dogs in which myelography had been performed. Our hypothesis was that sites of development of spondylosis would be positively associated with sites of type II IVDD (protrusion of the annulus without nuclear extrusion), which, similar to spondylosis, is thought to develop as a result of annular tearing and stress. We also hypothesized that type I IVDD (extrusion of the nucleus pulposus through an annular tear into the vertebral canal), which is linked to chondrocyte metabolic anomalies, would not be associated with spondylosis.16 Because spondylosis can alter biomechanical features of the vertebral column, we also hypothesized that associations existed among locations of spondylosis and sites of disk herniation.
Intervertebral disk disease
Morgan JP, Ljunggren G, Read R. Spondylosis deformans (vertebral osteophytosis) in the dog. A radiographic study from England, Sweden and U.S.A. J Small Anim Pract 1967;8:57–66.
Read RM, Smith RN. A comparison of spondylosis deformans in the English and Swedish cat and in the English dog. J Small Anim Pract 1968;9:159–166.
Breit S, Kunzel W. The position and shape of osteophyte formations at canine vertebral endplates and its influence on radiographic diagnosis. Anat Histol Embryol 2001;30:179–184.
Carnier P, Gallo L, Sturaro E, et al. Prevalence of spondylosis deformans and estimates of genetic parameters for the degree of osteophytes development in Italian Boxer dogs. J Anim Sci 2004;82:85–92.
Morgan JP, Hansson K, Miyabayashi T. Spondylosis deformans in the female Beagle dog: a radiographic study. J Small Anim Pract 1989;30:457–460.
Resnick D. Degenerative diseases of the spine. In: Resnick D, ed. Diagnosis of bone and joint disorders. Philadelphia: WB Saunders Co, 2002;1382–1475.
Osti OL, Vernon-Roberts B, Moore R, et al. Annular tears and disc degeneration in the lumbar spine. A post-mortem study of 135 discs. J Bone Joint Surg Br 1992;74:678–682.
Adams MS, McNally DS, Dolan P. “Stress” distributions inside intervertebral disks: the effect of age and degeneration. J Bone Joint Surg Br 1996;78:965–972.
Van den Hooff A. Histologic age changes in the annulus fibrosus of the human intervertebral disk with a discussion of the problem of disk herniation. Gerontologia 1964;9:136–149.
Hansen HJ. A pathologic-anatomical study on disc degeneration in the dog, with special reference to the so-called enchondrosis intervertebralis. Acta Orthop Scand Suppl 1952;11:1–117.
Bray JP, Burbidge HM. The canine intervertebral disk. Part two: degenerative changes—nonchondrodystrophoid versus chondrodystrophoid disks. J Am Anim Hosp Assoc 1998;34:135–144.
Jones JC, Sorjonen DC, Simpson ST, et al. Comparison between computed tomographic and surgical findings in nine largebreed dogs with lumbosacral stenosis. Vet Radiol Ultrasound 1996;37:247–256.
Morgan JP, Biery DN. Spondylosis deformans. In: Newton CD, Nunamaker D, eds. Textbook of small animal orthopedics. Ithaca, NY: International Veterinary Information Services, 1985;733–738.
Thornbury JR, Fryback DG, Turski PA, et al. Disk-caused nerve compression in patients with acute low-back pain: diagnosis with MR, CT myelography, and plain CT. Radiology 1993;186:731–738.
Janssen ME, Bertrand SL, Joe C, et al. Lumbar herniated disk disease: comparison of MRI, myelography, and post-myelographic CT scan with surgical findings. Orthopedics 1994;17:121–127.
Seiler G, Hani H, Scheidegger J, et al. Staging of lumbar intervertebral disc degeneration in nonchondrodystrophic dogs using low-field magnetic resonance imaging. Vet Radiol Ultrasound 2003;44:179–184.
Macias C, McKee WM, May C, et al. Thoracolumbar disc disease in large dogs: a study of 99 cases. J Small Anim Pract 2002;43:439–446.
Badoux DM. General biostatistics and biomechanics. In: Getty R, ed. Sisson and Grossman's anatomy of domestic animals. 5th ed. Philadelphia: WB Saunders Co, 1975;48–83.
Goggin JE, Li A, Franti CE. Canine intervertebral disk disease: characterization by age, sex, breed, and anatomic site of involvement. Am J Vet Res 1970;31:1687–1692.
Brown NO, Helphrey ML, Prata RG. Thoracolumbar disk disease in the dog: a retrospective analysis of 187 cases. J Am Anim Hosp Assoc 1977;13:665–672.
Ferreira AJ, Correia JH, Jaggy A. Thoracolumbar disc disease in 71 paraplegic dogs: influence of rate of onset and duration of clinical signs on treatment results. J Small Anim Pract 2002;43:158–163.
Park P, Garton HJ, Gala VC, et al. Adjacent segment disease after lumbar or lumbosacral fusion: review of the literature. Spine 2004;29:1938–1944.
Hino H, Abumi K, Kanayama M, et al. Dynamic motion analysis of normal and unstable cervical spines using cineradiography. An in vivo study. Spine 1999;24:163–168.
Mayhew PD, McLear RC, Ziemer LS, et al. Risk factors for recurrence of clinical signs associated with thoracolumbar intervertebral disk herniation in dogs: 229 cases (1994–2000). J Am Vet Med Assoc 2004;225:1231–1236.