Degenerative spinal disease, a common ailment in people and dogs,1,2 is characterized by degeneration of different spinal structures, and IVD degeneration has been most investigated.3–5 To date, MRI is considered the most reliable diagnostic tool to evaluate IVD degeneration status and to grade IVD degeneration in people6,7 and dogs.8,9 Although the gold standard for evaluating the degenerative status of IVDs is postmortem macroscopic and histologic evaluation, for antemortem classification purposes, several MRI-based and gross morphologically based grading schemes for lumbar and cervical IVD degeneration have been described in people.6,7,10–14 Of these, the MRI-based grading scheme reported by Pfirrmann et al7 and the macroscopic observation-based grading scheme reported by Thompson et al10 are most widely used and validated for systematic evaluation of IVD degeneration. More recently, these 2 grading schemes have been successfully adapted and validated for evaluating IVD degeneration in dogs.8,15 Additionally, both of these schemes are known to have substantial agreement with each other,15 indicating that MRI, to a large extent, reflects gross pathological changes in IVDs.
Intervertebral disk degeneration in cats has been investigated less extensively than that in people and dogs, and the incidence of IVD disease in cats is lower,16–19 although the disease is still common.20–24 Additionally, studies20,21,24 dating from the 1960s show that cats seem to have IVD degeneration with morphological characteristics similar to those in affected people and dogs. Although the macroscopic and histologic aspects of IVD degeneration in cats have been described,20–22,24,25 the condition in cats has not been analyzed systematically with standardized grading schemes.
Therefore, the objectives of the present study were to evaluate the agreement and correlation between an MRI-based grading scheme (modified from that reported by Pfirrmann et al7) and a macroscopic observation-based grading scheme (modified from that reported by Thompson et al10) when used to assess IVD degeneration in cats. We hypothesized that the results for the 2 grading schemes would have substantial to almost perfect inter- and intraobserver agreement and that there would be almost perfect agreement and a strong, positive correlation between results for the 2 grading schemes.
The authors declare that there were no conflicts of interest. Presented in part as a poster at the 30th Annual Symposium of the European Society of Veterinary Neurology and European College of Veterinary Neurology, Helsinki, Finland, September 2017.
The authors thank Dr. Christian W. A. Pfirrmann for consultation regarding the interpretation of results from the present study.
Bitterli T, Ettinger L, Pozzi A, et al. Investigation and grading of intervertebral disc degeneration in the cat by way of magnetic resonance imaging and macroscopic evaluation (abstr). Vet Comp Orthop Traumatol 2016;29:A18-A19.
Philips Ingenia 3T, Philips Healthcare, Hamburg, Germany.
Philips dStream HeadNeckSpine and FlexCoverage posterior coils, Philips Healthcare, Hamburg, Germany.
Osirix, Pixmeo SARL, Bern, Switzerland.
Microsoft Excel 2016, Microsoft Corp, Redmond, Wash.
EXAKT, Exakt Advanced Technologies GmbH, Norderstadt, Germany.
Leica DC 480, Leica Microsystems, Wetzlar, Germany.
Leica RL 30120201, Leica Microsystems, Wetzlar, Germany.
Leica IM1000, Leica Microsystems, Wetzlar, Germany.
Preview, MacOS, Apple Inc, Cupertino, Calif.
R: a language and environment for statistical computing, R Foundation for Statistical Computing, Vienna, Austria. Available at: www.R-project.org. Accessed Dec 14, 2015.
Kappa as a measure of concordance in categorical sorting, Lowry R, Avon, Conn. Available at: vassarstats.net/kappa.html. Accessed Jan 27, 2018.
Pedowitz DI, Auerbach JD, Gibson BW, et al. Correlation of MRI and gross morphologic grading of lumbar intervertebral discs (abstr). Trans Orthop Res Soc 2005:378.
2. Bergknut N, Smolders LA, Grinwis GCM, et al. Intervertebral disc degeneration in the dog. Part 1: anatomy and physiology of the intervertebral disc and characteristics of intervertebral disc degeneration. Vet J 2013;195:282–291.
3. Bergknut N, Rutges JPH, Kranenburg H-J, et al. The dog as an animal model for intervertebral disc degeneration?. Spine (Phila Pa 1976) 2012;37:351–358.
4. Hansen T, Smolders LA, Tryfonidou MA, et al. The myth of fibroid degeneration in the canine intervertebral disc: a histopathological comparison of intervertebral disc degeneration in chondrodystrophic and nonchondrodystrophic dogs. Vet Pathol 2017;54:945–952.
5. Roberts S, Evans H, Trivedi J, et al. Histology and pathology of the human intervertebral disc. J Bone Joint Surg Am 2006;88(suppl 2):10–14.
6. Kettler A, Wilke HJ. Review of existing grading systems for cervical or lumbar disc and facet joint degeneration. Eur Spine J 2006;15:705–718.
7. Pfirrmann CW, Metzdorf AZanetti M, et al. Magnetic resonance classification of lumbar intervertebral disc degeneration.. Spine (Phila Pa 1976) 26:1873–1876.
8. Bergknut N, Auriemma E, Wijsman S, et al. Evaluation of intervertebral disk degeneration in chondrodystrophic and nonchondrodystrophic dogs by use of Pfirrmann grading of images obtained with low-field magnetic resonance imaging. Am J Vet Res 2011;72:893–898.
9. Kärkkäinen M, Punto L, Tulamo R. Magnetic resonance imaging of canine degenerative lumbar spine diseases. Vet Radiol Ultrasound 1993;34:399–404.
10. Thompson JP, Pearce RH, Schechter MT, et al. Preliminary evaluation of a scheme for grading the gross morphology of the human intervertebral disc. Spine (Phila Pa 1976) 1990;15:411–415.
11. Viikari-Juntura E, Raininko R, Videman T PL. Evaluation of cervical disc degeneration with ultralow field MRI and discography. An experimental study on cadavers. Spine (Phila Pa 1976) 1989;14:616–619.
12. Silberstein CE. The evolution of degenerative changes in the cervical spine and an investigation into the “joints of Luschka.” Clin Orthop Relat Res 1965;40:184–204.
13. Yu S, Haughton VM, Sether LA, et al. Criteria for classifying normal and degenerated lumbar intervertebral disks. Radiology 1989;170:523–526.
14. Brant-Zawadzki MN, Jensen MC, Obuchowski N, et al. Interobserver and intraobserver variability in interpretation of lumbar disc abnormalities. A comparison of two nomenclatures. Spine (Phila Pa 1976) 1995;20:1257–1263.
15. Bergknut N, Grinwis G, Pickee E, et al. Reliability of macroscopic grading of intervertebral disk degeneration in dogs by use of the Thompson system and comparison with low-field magnetic resonance imaging findings. Am J Vet Res 2011;72:899–904.
16. Delisser PJ, Burton NJ. What Is Your Diagnosis? 3-year-old neutered male Burmese cat with a 3-month history of nonspecific hind limb gait abnormalities. J Am Vet Med Assoc 2012;240:1289–1290.
17. Danielski A, Bertran J, Fitzpatrick N. Management of degenerative lumbosacral disease in cats by dorsal laminectomy and lumbosacral stabilization. Vet Comp Orthop Traumatol 2013;26:69–75.
18. De Decker S, Warner A-S, Volk HA. Prevalence and breed predisposition for thoracolumbar intervertebral disc disease in cats. J Feline Med Surg 2017;19:419–423.
22. King A, Smith R. Disc protrusions in the cat: distribution of dorsal protrusions along the vertebral column. Vet Rec 1960;72:335–337.
25. Butler WF, Smith RN. Age changes in the nucleus pulposus of the non-ruptured intervertebral disc of the cat. Res Vet Sci 1967;8:151–156.
27. Landis JR, Koch GG. An application of hierarchical kappa-type statistics in the assessment of majority agreement among multiple observers. Biometrics 1977;33:363–374.
28. Koch GG, Landis JR, Freeman JL, et al. A general methodology for the analysis of experiments with repeated measurement of categorical data. Biometrics 1977;33:133–158.
29. Bergknut N, Meij BP, Hagman R, et al. Intervertebral disc disease in dog—part 1: a new histological grading scheme for classification of intervertebral disc degeneration in dogs. Vet J 2013;195:156–163.
30. Hansen HJ. A pathologic-anatomic study on disc degeneration in dog, with special reference to the so-called enchondrosis intervertebralis. Acta Orthop Scand 1952;23(suppl 11):1–117.
31. Wijayathunga VN, Ridgway JP, Ingham E, et al. A nondestructive method to distinguish the internal constituent architecture of the intervertebral discs using 9.4 Tesla magnetic resonance imaging. Spine (Phila Pa 1976) 2015;40:E1315–E1322.
32. Welsch GH, Trattnig S, Paternostro-Sluga T, et al. Parametric T2 and T2* mapping techniques to visualize intervertebral disc degeneration in patients with low back pain: initial results on the clinical use of 3.0 Tesla MRI. Skeletal Radiol 2011;40:543–551.
34. Seiler G, Häni 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.
36. Bossens K, Bhatti S, Van Soens I, et al. Diffuse idiopathic skeletal hyperostosis of the spine in a nine-year-old cat. J Small Anim Pract 2016;57:33–35.