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- Author or Editor: Herman A. Hazewinkel x
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Objective—To assess the extent of agreement between computed tomography (CT), magnetic resonance imaging (MRI), and surgical findings in dogs with degenerative lumbosacral stenosis.
Animals—35 dogs with degenerative lumbosacral stenosis.
Procedures—Results of preoperative CT and MRI were compared with surgical findings with respect to degree and location of disk protrusion, position of the dural sac, amount of epidural fat, and swelling of spinal nerve roots.
Results—A lumbosacral step was seen on radiographic images from 22 of 32 (69%) dogs, on CT images from 23 of 35 (66%) dogs, and on MR images from 21 of 35 (60%) dogs. Most dogs had slight or moderate disk protrusion that was centrally located. There was substantial or near perfect agreement between CT and MRI findings in regard to degree of disk protrusion (kappa, 0.88), location of disk protrusion (0.63), position of the dural sac (0.89), amount of epidural fat (0.72), and swelling of spinal nerve roots (0.60). The degree of agreement between CT and surgical findings and between MRI and surgical findings was moderate in regard to degree and location of disk protrusion (kappa, 0.44 to 0.56) and swelling of spinal nerve roots (0.40 and 0.50).
Conclusions and Clinical Relevance—Results indicate that there is a high degree of agreement between CT and MRI findings in dogs with degenerative lumbosacral stenosis but that the degree of agreement between diagnostic imaging findings and surgical findings is lower.
Objective—To quantitatively assess distractioninduced bone formation in a crural lengthening model in dogs by use of delayed-image bone scintigraphy.
Animals—12 mature Labrador Retrievers.
Procedure—Dogs were randomly allocated to 1 of 3 groups. A circular external skeletal fixation system was mounted on the right crus of each dog. Osteotomy of the distal portion of the tibia and fibula was performed in groups 1 and 2 and was followed by a lengthening procedure of 10 mm in the first group only. The third group served as sham-operated controls. Delayed-image bone scintigraphy with technetium-99m hydroxy methylene diphosphonate was performed 2, 4, and 6 weeks after surgery. Delayedimage–to–region-of-interest, delayed-image–to–crural, and delayed-image–to–femoral scintigraphic activity ratios were calculated. New bone formation was quantified by use of densitometric image analysis, and values for the scintigraphic ratios were compared.
Results—In the distraction and osteotomy groups, delayed-image–to–region-of-interest and delayedimage-to-crural ratios increased significantly. Although densitometric image analysis revealed increased bone formation after distraction, the region-of-interest ratios and crural ratios were similar in both groups. All dogs had increased delayedimage–to–femoral ratios.
Conclusions and Clinical Relevance—Delayed-image bone scintigraphy ratios were not effective at differentiating between the amounts of distraction-induced bone and osteotomy-induced bone. Metabolic bone activity in the adjacent femur was increased as a consequence of circular external skeletal fixator placement. Delayed-image bone scintigraphy was not adequately sensitive to quantitatively monitor bone formation but may be useful as an early predictor of bone healing.
Objective—To study radiographic and genetic aspects of hereditary radial head subluxation in Bouviers des Flandres.
Animals—26 related Bouviers des Flandres affected with bilateral subluxation of the radial head, 10 unaffected related dogs, and 29 unrelated Bouviers des Flandres with diagnoses of nonskeletal diseases.
Procedures—All dogs were radiographically studied, and their DNA was analyzed with a genome-wide screen of 1,536 single nucleotide polymorphisms. In addition, karyotyping was performed in an unaffected dam and its affected offspring.
Results—Both forelimbs of affected dogs were disproportionately short with caudolateral subluxation or luxation of the radial head. Angulation of the radial axis at the mid-diaphysis ranged from 9.3° to 30.3° (mean ± SD, 14.9 ± 6.1°), with an estimated age of onset from 0 to 4 months. Poorly defined medial coronoid processes and osteoarthritis of the elbow joint, cranial bowing of the olecranon, and disturbed growth in length of the ulna with sharply demarcated spurs were noticed on radiographs of affected dogs. Genealogical analysis indicated that most affected dogs were closely related, but the mode of inheritance was not clear. The DNA analysis found that 205 single nucleotide polymorphisms were monomorphic in the affected dogs. Conventional chromosome staining revealed no numerical chromosomal aberration.
Conclusions and Clinical Relevance—Congenital radial head luxation and subluxation in the studied Bouviers des Flandres were characterized by angulation of the radial axis leading to caudolateral subluxation of the radial head and insufficient growth of the distal portion of the ulna together with cranial bowing of the olecranon.
Objective—To evaluate the involvement of various collagen genes in the development of fragmented medial coronoid process (FCP) in Labrador Retrievers.
Sample Population—93 dogs originating from 13 litters were used in the study; FCP was diagnosed in 35 dogs, and each affected dog had at least 1 sibling that was also affected. Twelve dams and sires were included in the analysis. All dogs were purebred Labrador Retrievers except for 2 litters (offspring of a female Golden Retriever-Labrador Retriever mixed-breed dog).
Procedures—For each dog, DNA was isolated from blood samples. Polymorphic microsatellite markers adjacent to 14 candidate genes (ie, COL1A1, COL1A2, COL2A1, COL3A1, COL5A1, COL5A2, COL6A3, COL9A1, COL9A2, COL9A3, COL10A1, COL11A1, COL11A2, and COL24A1) were analyzed by use of PCR assays; genotypes were determined via automated detection of DNA products. The level of allele sharing between pairs of affected siblings was assessed.
Results—Among the 93 dogs, allele sharing of the 14 collagen genes was determined as follows: COL1A1, 45%; COL1A2, 47%; COL2A1, 37%; COL3A1, 32%; COL5A1, 43%; COL5A2, 32%; COL6A3, 36%; COL9A1, 45%; COL9A2, 49%; COL9A3, 38%; COL10A1, 46%; COL11A1, 52%; COL11A2, 47%; and COL24A1, 47%.
Conclusions and Clinical Relevance—Because siblings share 50% of their genome at random, the fact that the percentages of allele sharing among the analyzed collagen genes were not significantly > 50% indicates that these genes are not determinant candidates for FCP in Labrador Retrievers. The gene for the vitamin D receptor could also be excluded because of its proximity to COL2A1.
Objective—To assess whether the Pfirrmann system for grading lumbar intervertebral disk (IVD) degeneration in humans can also be used in dogs.
Procedures—Magnetic resonance imaging was used to obtain images of vertebral segments from dogs, which were reviewed separately by 3 observers who graded the extent of degeneration in each visible IVD by use of the Pfirrmann classification system used for grading lumbar IVD degeneration in humans. Grading was validated against 2 factors associated with the extent of disk degeneration: type of dog (chondrodystrophic or nonchondrodystrophic breeds) and age.
Results—Interobserver and intraobserver agreement for Pfirrmann grading of IVD degeneration were good (κ scores, 0.81 to 0.93). An increase in the extent of disk degeneration was positively correlated with increases in age and with chondrodystrophic breed.
Conclusions and Clinical Relevance—The Pfirrmann system was reliably used to grade IVD degeneration in dogs of various breeds and ages. An increase in the extent of IVD degeneration was positively correlated with increases in age and with chondrodystrophic-type dogs.
Objective—To evaluate the reliability of the Thompson system for use in grading the gross pathological changes of intervertebral disk (IVD) degeneration in dogs and to investigate the agreement between gross pathological findings and low-field (0.2-T) magnetic resonance imaging (MRI) findings.
Sample—Vertebral columns from cadavers of 19 dogs of various ages, breeds, and origins.
Procedures—182 intervertebral segments were collected from 19 canine cadavers. Sagittal T2-weighted MRI of the T11 through S1 portion of the vertebral column was performed within 24 hours after the dogs were euthanized. The vertebral columns were subsequently divided in the midsagittal plane, and high-resolution photographs were obtained of each intervertebral segment (end plate—disk—end plate). The MRI images and photographs were graded separately in a blinded manner by 4 observers who used both Pfirrmann and Thompson grading criteria.
Results—The interobserver agreement for Thompson scores ranged from 0.76 to 0.88, and the intraobserver agreement ranged from 0.88 to 0.94 (Cohen weighted κ analysis). Agreement between scores for the Pfirrmann and Thompson grading criteria was κ = 0.70.
Conclusions and Clinical Relevance—Grading of IVD degeneration in dogs by use of the Thompson system resulted in high interobserver and intraobserver agreement, and scores for the Thompson system had substantial agreement with low-field MRI findings graded by use of the Pfirrmann system. This suggested that low-field MRI can be used to diagnose IVD degeneration in dogs.
Objective—To determine the incidence and distribution of intervertebral disk (IVD) degeneration–related diseases in a large population of dogs of various breeds, ages, and sexes and to determine mortality rates among dogs with these diseases.
Sample—Insurance data for dogs with veterinary health-care and life insurance coverage (n = 665,249 and 552,120, respectively).
Procedures—Insurance claim records of 1 company in Sweden were searched to identify dogs with IVD degeneration–related diseases; incidence and mortality rates were determined for affected dogs < 12 years old and < 10 years old, respectively. Only the first paid IVD degeneration–related claim for a dog was included in incidence rate calculations.
Results—The incidence rate of IVD degeneration–related diseases was 27.8 (95% confidence interval [CI], 27.2 to 28.4) occurrences/10,000 dog-years at risk (DYAR), indicating that approximately 0.3% of dogs/y in this population were affected. Miniature Dachshund was the most highly represented breed, followed by Standard Dachshund and Doberman Pinscher (237.1 [95% CI, 212.9 to 261.4], 141.5 [95% CI, 135.5 to 147.4], and 88.6 [95% CI, 72.1 to 105.2] occurrences/10,000 DYAR, respectively). The incidence rate of IVD degeneration–related disease was greater in male than in female dogs and increased with age. Overall mortality rate attributed to IVD degeneration–related diseases was 9.4 (95% CI, 8.9 to 9.8) deaths/10,000 DYAR and was greater in males than in females.
Conclusions and Clinical Relevance—Differences in incidence rates among various breeds suggested a genetic involvement. Knowledge of the distribution of IVD degeneration–related diseases among dogs of various breeds and ages may facilitate early diagnosis and preemptive treatments in patients at risk for developing these diseases.