The Myth of Fibroid Degeneration in the Canine Intervertebral Disc: A Histopathological Comparison of Intervertebral Disc Degeneration in Chondrodystrophic and Nonchondrodystrophic Dogs

Abstract

The myth of fibroid degeneration in the canine intervertebral disc -A histopathological comparison of disc degeneration in chondrodystrophic and nonchondrodystrophic dogs Myten om fibroid degeneration i hundens intervertebraldiskerEn histopatologisk jämförelse av diskdegeneration mellan chondrodystrofa och icke chondrodystrofa hundar Tove Hansen Supervisor: Niklas Bergknut, Department of Clinical Sciences Examiner: Ragnvi Hagman, Department of Clinical Sciences Degree Project in Veterinary Medicine SUMMARYIn the 1950's, the veterinary pathologist, Hans-Jörgen Hansen noticed several dissimilarities between so called chondrodystrophic and non-chondrodystrophic dog breeds regarding intervertebral disc degeneration and related diseases. Chondrodystrophic breeds are characterized by disproportionally short extremities due to disturbances in the endochondral ossification whereas non-chondrodystrophic breeds have normal bodily constitutions. The two breed types often differ regarding age of onset of disease, spinal location and severity of clinical signs. He also noted different histopathological patterns during the course of degeneration, foremost in the centre of the intervertebral disc, the nucleus pulposus. Due to this, he named the degenerative processes chondroid metamorphosis and fibroid metamorphosis in chondrodystrophic and non-chondrodystrophic breeds respectively. In general, chondroid metamorphosis refers to the replacement of the original cell type (the notochordal cell) with chondrocyte-like cells, whereas the fibroid metamorphosis refers to replacement of these cells with fibrocyte-like cells. This distinction has since then been an accepted distinction between the two breed types. However, more recent studies indicate that the histopathological patterns are more similar in the two breed types than previously described, and that the chondroid metamorphosis might be the degenerative process taking place in both breed types.In this study the histopathological appearances of 42 intervertebral discs from 16 chondrodystrophic and 17 non-chondrodystrophic dogs in early stage intervertebral disc degeneration were examined. After midsagittal transection of the spines, the intervertebral discs were graded macroscopically between one and three on a five-grade scale (the Thompson grading scheme). Subsequently, each intervertebral disc was individually fixated in formalin and decalcified in EDTA. After decalcification, the intervertebral discs were embedded in paraffin, sliced with a microtome and stained with Hematoxilin and Eosin and Alcian Blue/Picrosirius Red. The histological samples were thereafter graded according to a histological grading scheme (the Boos grading scheme) after which the histological scores were compared between chondrodystrophic and non-chondrodystrophic dogs.The results showed that there was a significant difference in total histological scores between chondrodystrophic and non-chondrodystrophic dogs in the two lowest macroscopical grades of degeneration. Chondrodystrophic dogs had a highe...

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“…Chondroid metaplasia was originally described in the classical work of Hansen (1952) 101 in the nonchondrodystrophic (non-ChD) canine 102,103 and the lapine IVD. 104 Chondroid metaplasia is considered to be a forerunner to the IVD calcification frequently found in ChD canine breeds.…”

Pathologic Features of the Intervertebral Disc in Young Nova Scotia Duck Tolling Retrievers Confirms Chondrodystrophy Degenerative Phenotype Associated With Genotype

“…In addition, studies have historically been confounded by the difficulty in accurately defining what constitutes a chondrodystrophic dog. Publications evaluating clinical differences between chondrodystrophic and nonchondrodystrophic dogs do not have consensus on which breeds fall into which category 3,4,11,14,18,26 or even how the classification into the 2 categories should be performed. 20,25,31 Classification based on gross morphological traits is problematic since a short-limbed phenotype may be associated with the CFA18 FGF4 retrogene or the CFA12 FGF4 retrogene, and only the latter appears to also result in the chondrodystrophic phenotype with concurrent degeneration of the IVD.…”

Intervertebral disc herniation in two coatis (Nasua nasua) and postoperative laminectomy membrane formation

“…This is traditionally considered a feature of Hansen type I disc herniation (16,17). It must be mentioned that the theory of two histopathologically differing types of disc degeneration in chondrodystrophic and non-chondrodystrophic dogs has been questioned recently (18). Although chronic clinical signs were also reported in the second coati, MRI findings were more consistent with intervertebral disc extrusion (Hansen type I).…”