Vertebral and spinal malformations in small brachycephalic dog breeds: Current knowledge and remaining questions

Small brachycephalic dog breeds, such as the French bulldog, English bulldog and pug have become increasingly popular. These breeds are predisposed to a variety of vertebral and spinal malformations, including hemivertebra, caudal articular process dysplasia, transitional vertebra, cranial thoracic vertebral canal stenosis, spinal arachnoid diverticulum and meningeal fibrosis. Recent studies have provided new insights into the prevalence, anatomical characteristics, pathophysiology and treatment of these conditions. Thoracic hemivertebra, caudal articular process dysplasia, transitional vertebra, and cranial thoracic vertebral canal stenosis occur commonly in neurologically normal dogs. Although the clinical relevance of these vertebral anomalies has therefore been questioned, severe kyphosis and hemivertebra in pugs have been associated with an increased likelihood of neurological signs. Meningeal fibrosis is characterised by the formation of dense intradural fibrotic adhesions, constricting the spinal cord. This condition has been heavily associated with the pug breed. It is in pugs further common to observe multiple concurrent spinal disorder in association with chronic progressive pelvic limb gait abnormalities. This clinical presentation has been referred to as 'pug dog thoracolumbar myelopathy' and potential genetic risk factors have recently been identified. Despite our increased knowledge, many questions remain currently unanswered. This review discusses our current understanding and controversies surrounding vertebral and spinal malformations in small brachycephalic dog breeds.

Lumbosacral transitional vertebra in 14 dog breeds in Norway: Occurrence, risk factors and association with hip dysplasia

A lumbosacral transitional vertebra (LTV) is a congenital anomaly of the spine and has been suggested to predispose to canine hip dysplasia (CHD). This retrospective, cross-sectional study investigated the prevalence of LTV and CHD among 14 dog breeds in Norway, the possible associations with risk factors, and whether LTV was a risk factor for the development of hip dysplasia. The results were based on evaluation of ventrodorsal radiographs from the CHD screening program from the Norwegian Kennel Club from February 2014 to January 2022. A total of 13,950 dogs were included in the study. For statistical analysis, CHD grades were reclassified from the official Federation Cynologique Internationale (FCI) grades into three grades: CHD free (CHD=A, B), CHD mild (CHD=C), and CHD severe (CHD=D, E). In the study sample, the overall occurrence of LTV was 18.5%, of which 32.9% were type 1, 45.7% type 2% and 21.4% type 3. The occurrence of LTV varied significantly among the included breeds, ranging from 9.5% to 46.2%. There was no association between sex and LTV. The frequencies of CHD grades were A: 43.1%; B: 31.4%; C: 18.4%; D: 6.0%; E: 1.1%. There was a statistically significant association with mild and severe CHD in dogs with LTV type 2 and LTV type 3 (P< 0.001). In the population studied, the prevalence of LTV was different among breeds. This supports initial data on the heredity of LTV and the diverse occurrence of LTV among breeds. Our results indicate that LTV type 2 and type 3 are associated with mild and severe CHD development. Therefore, this study has potentially identified an additional risk factor for the development of hip dysplasia.

Influence of Femoral Position and Pelvic Projection on Norberg Angle Measurements

OBJECTIVE

 Canine hip dysplasia is a common orthopaedic disease in dogs. The Norberg angle value is a measure of hip joint laxity. The aim of this study was to quantify the degree of rotation necessary to consider the radiograph as inadequately positioned and to determine the influence of rotation on the Norberg angle.

STUDY DESIGN

 Three sets of radiographs with different positioning and projections were acquired using 10 canine cadavers. Rotation of the pelvis was simulated by rotating the X-ray tube without changing the position of the patient.

RESULTS

 In dorsoventral projections, the Norberg angle value is increased by 3.2 to 5.8%. Due to rotation along the long axis, the Norberg angle increases on one side and decreases on the contralateral side by approximately the same value. Rotation of greater than 2 degrees in a lateral direction is visually perceived by the observer as tilted. Rotation of the projection in the caudoventral to craniodorsal direction causes mild increase of the Norberg angle (≤1%), while rotation of the projection in a cranioventral to caudodorsal direction causes moderate (≤2%) decrease of the Norberg angle. Rotation of less than -10 degrees (caudoventral to craniodorsal) or greater than 10 degrees (cranioventral to caudodorsal) is visually perceived as tilted.

CONCLUSION

 Tilted images that are subjectively perceived evaluable have only little effect on the Norberg angle and are therefore probably acceptable. Dorsoventral projections can be recognized based on the proximal position of the patella and should be excluded from evaluation, as the Norberg angle value can be falsely increased.

Canine Mobility Maintenance and Promotion of a Healthy Lifestyle

This article highlights the recommendations and considerations for maintaining a healthy canine lifestyle. A key component of a healthy lifestyle is the enhancement and optimization of mobility. Mobility is essential in maintaining a high quality of life and involves the interplay of a dog's structure, posture, body condition score, physical exercise, and a healthy human-animal bond throughout a dog's lifetime.

Comparing Hip Dysplasia in Dogs and Humans: A Review

Hip dysplasia (HD) is common in both humans and dogs. This interconnection is because humans and dogs descended from a common ancestor and therefore have a similar anatomy at micro- and macroscopic levels. Furthermore, dogs are the animals of choice for testing new treatments for human hip dysplasia and orthopedic surgery in general. However, little literature exists comparing HD between the two species. Therefore, the aim of this review is to describe the anatomy, etiology, pathogenesis, diagnostics, and treatment of HD in humans and dogs. HD as an orthopedic condition has many common characteristics in terms of etiology and pathogenesis and most of the differences can be explained by the evolutionary differences between dogs and humans. Likewise, the treatment of HD shows many commonalities between humans and dogs. Conservative treatment and surgical interventions such as femoral osteotomy, pelvic osteotomy and total hip arthroplasty are very similar between humans and dogs. Therefore, future integration of knowledge and experiences for HD between dogs and humans could be beneficial for both species.

The Prevalence of Feline Hip Dysplasia, Patellar Luxation and Lumbosacral Transitional Vertebrae in Pedigree Cats in The Czech Republic

Simple Summary

Hip dysplasia, patellar luxation and lumbosacral transitional vertebra are not well described in cats, most likely because cats can often much better compensate for pelvic limb lameness and hide their pain and, as a result, owners are less likely to notice this condition. Pedigree cats at least 10 months old were recruited prospectively in this study to find the prevalence of feline hip dysplasia, patellar luxation and lumbosacral transitional vertebra. The prevalence of hip joint dysplasia in all pedigree cats was 46.7%, of which 78% of cats had bilateral dysplasia. Dysplasia was mainly from mild (grade 1) to moderate (grade 2); however, 6.1% of hip joints showed signs of severe hip dysplasia (grade 3) in Maine Coon and Siberian cats. Patellar luxation was noted in 32.7% of the pedigree cats, was present bilaterally in 91.4% and was grade 1 or 2 in most cats. The presence of lumbosacral transitional vertebra was noted in 7.5% of the pedigree cats. The high prevalence of hip dysplasia in pedigree cats should be considered and screening pedigree cats for hip dysplasia is recommended before they are used in breeding programs.

Abstract

(1) Background: The aim of this study was to find the prevalence of feline hip dysplasia (HD), patellar luxation and lumbosacral transitional vertebra (LTV) in pedigree cats in the Czech Republic. (2) Methods: 107 pedigree cats at least 10 months old were recruited prospectively at the Small Animal Clinic at the University of Veterinary and Pharmaceutical Sciences Brno, CZ, between April 2019 and July 2020. (3) Results: The prevalence of hip joint dysplasia in all pedigree cats was 46.7%, of which 78% of cats had bilateral dysplasia. The HD was mainly from mild (grade 1) to moderate (grade 2); however, 6.1% of hip joints showed signs of severe HD (grade 3) in Maine Coon and Siberian cats. Patellar luxation was noted in 32.7% of the pedigree cats, was present bilaterally in 91.4% and was grade 1 or 2 in most cats. The presence of LTV was noted in 7.5% of pedigree cats. (4) Conclusions: The high prevalence of HD in pedigree cats should be considered and screening pedigree cats for HD is recommended before they are used in breeding programs.

Genetic background of lumbosacral transitional vertebrae in German shepherd dogs

OBJECTIVES

Estimation of genetic parameters of lumbosacral transitional vertebrae based on data derived from radiographic screening of 27,597 German shepherd dogs.

MATERIALS AND METHODS

Results of radiographic screening for lumbosacral transitional vertebrae classified according to a published scheme were collected. Obtained data were used for estimating variance components in single and multiple trait linear animal models to obtain heritabilities and additive genetic correlations for different types of lumbosacral transitional vertebrae.

RESULTS

Estimations indicated a moderate heritability of lumbosacral transitional vertebrae of h²  = 0.27. Trait definitions reflecting the different types of lumbosacral transitional vertebrae revealed positive additive genetic correlations of r_g  > 0.5 between those types usually categorised as pathologic.

CLINICAL SIGNIFICANCE

Results of comprehensive genetic analyses enable the development of breeding measures against lumbosacral transitional vertebrae to reduce their prevalence and support management of potentially correlated diseases in German shepherd dogs.

Radiographic evaluation of congenital vertebral anomalies in Korean raccoon dogs (Nyctereutes procyonoides koreensis)

Background

The normal vertebral anatomy of Korean raccoon dogs and their variants require research attention as a prerequisite for identifying pathologies and anomalies.

Objectives

This retrospective study aimed at describing the vertebral formula and congenital vertebral anomalies in Korean raccoon dogs (Nyctereutes procyonoides koreensis).

Methods

Radiographs of 82 raccoon dogs (42 males, 40 females) acquired from May 2013 to June 2020 in the Gangwon Wildlife Medical Rescue Center were reviewed to evaluate the cervical, thoracic, and lumbar vertebrae of the spine.

Results

Normal morphology of all vertebrae was observed in 50 of the 82 raccoon dogs, and the vertebral formula was cervical 7, thoracic 13, and lumbar 7. Congenital vertebral anomalies were found in 32 raccoon dogs: transitional vertebrae (TV) in 31 and block vertebrae in 2. Two raccoon dogs had 2 types of vertebral anomalies: one had TV and block vertebra, and the other had 2 types of TV. Twenty-nine raccoon dogs had thoracolumbar TV (TTV) and 3 had lumbosacral TV. TTV was morphologically classified into 4 different types: unilateral extra-rib in 5 raccoon dogs, bilateral extra-ribs in 14, bilateral elongated transverse processes in 4, and an asymmetric mixed formation of extra-rib with elongated transverse process in 6.

Conclusions

This study showed that TTV is common in Korean raccoon dogs, and that the vertebral formula is relatively diverse. The bilateral extra-ribs type TTV is the most common variant, which is almost similar to normal rib to be confused the radiographic evaluation.

Variation in the seventh lumbar vertebra and the lumbosacral junction morphometry associated with the sacrocaudal fusion in greyhounds

The lumbosacral joint is where the 7th lumbar vertebra (L.7) articulates within the sacrum. It is a clinically important area in the dog because of its relatively large range of motion. The current study aims to determine the possible differences in the length of the L.7 vertebra and the angle of the lumbosacral junction among greyhounds of standard and those of fused sacra, and to determine the potential association of sex, body mass and type of fused sacrum (standard and fused) on the morphology of the L.7 vertebra and the angle of the lumbosacral junction. Radiographs of 55 greyhound cadavers were used for radiographing; all radiographic images were stored and measured using X-ray acquisition software, and then analysed using descriptive statistics, multiple linear regression and logistic regression. The results of this study showed a significant increase (p < .008) in the length of the L.7 vertebra and the angle of the lumbosacral junction (p < .028) in greyhounds with fused sacra comparing with those of standard sacra, but the L.6 length was not significant (p = .431). Differences have been found in the length of L.7 vertebra and the angle of the lumbosacral junction in greyhounds. It was found that in greyhounds, any variation in the sacrum's anatomical features may alter the structure of the surrounding anatomical structures such as the L.7 vertebra and lumbosacral junction.

The slope of the pelvis is variable in dogs but does not show correlation with femoral subluxation

The aim of this study was to investigate the variability of the slope of the pelvis in different dog breeds and the correlation between pelvic slope and femoral subluxation. The sacrum-pelvis angle (SPA), the angulation between the sacrum and the axis of the ilium was created to represent the differences in the slope of the pelvis on lateral pelvic radiographs. The Norberg angle (NA) was used to quantify the femoral subluxation on hip-extended radiographs. Archived standard ventrodorsal hip radiographs and lateral lumbosacral radiographs of the same dogs were retrieved and a single observer measured the SPA and the NA in each case. A total of 180 dogs from six different breeds were sampled. The SPA varied between 40° and 71.5° and the NA between 71.2° and 113.9°. The findings indicated that there are significant individual and interbreed variations in the slope of the pelvis. However, no significant relationship between the slope of the pelvis and femoral subluxation could be identified.

Lumbosacral transitional vertebrae in cats and its relationship to lumbosacral vertebral canal stenosis

OBJECTIVES

Although a clear relationship has been demonstrated between the presence of lumbosacral transitional vertebrae and the development of lumbosacral stenosis in dogs, this relationship has not been evaluated in cats. The aim of this study was to investigate the relationship between the presence of lumbosacral transitional vertebrae and lumbosacral stenosis in cats.

METHODS

The medical records and diagnostic imaging studies of 13 cats diagnosed with lumbosacral stenosis were retrospectively reviewed for lumbosacral abnormalities and compared with findings of 405 cats that underwent CT for reasons unrelated to spinal disease.

RESULTS

Clinical signs associated with lumbosacral stenosis included lumbosacral pain, low tail carriage, difficulty jumping, and urinary or faecal incontinence. Neurological signs included proprioceptive deficits, ambulatory paraparesis, pelvic limb ataxia, reduced spinal reflexes and reduced perianal reflex. Duration of clinical signs ranged from 1 day to 10 months (mean 3 months). Of the 13 cats with lumbosacral stenosis, seven (53.8%) were diagnosed with lumbosacral transitional vertebrae. In the control population of 405 cats, 24 (5.9%) were diagnosed with lumbosacral transitional vertebrae. Results indicated that lumbosacral transitional vertebrae were significantly ( P <0.0001) more prevalent in cats with lumbosacral stenosis compared with the control feline population (odds ratio 18.52, 95% confidence interval 6.1-62.1). Development of clinical signs of lumbosacral stenosis in cats with lumbosacral transitional vertebrae (mean 10.8 years) was not significantly different from that of cats without lumbosacral transitional vertebrae (mean 12.7 years). Likewise, there was no significant influence of breed ( P >0.99) or sex ( P = 0.29) on the occurrence of lumbosacral transitional vertebrae.

CONCLUSIONS AND RELEVANCE

Despite lumbosacral stenosis being a rare spinal condition in cats, lumbosacral transitional vertebrae can be considered a risk factor for its development.

C7 vertebra homeotic transformation in domestic dogs - are Pug dogs breaking mammalian evolutionary constraints?

The number of cervical vertebrae in mammals is almost constant at seven, regardless of their neck length, implying that there is selection against variation in this number. Homebox (Hox) genes are involved in this evolutionary mammalian conservation, and homeotic transformation of cervical into thoracic vertebrae (cervical ribs) is a common phenotypic abnormality when Hox gene expression is altered. This relatively benign phenotypic change can be associated with fatal traits in humans. Mutations in genes upstream of Hox, inbreeding and stressors during organogenesis can also cause cervical ribs. The aim of this study was to describe the prevalence of cervical ribs in a large group of domestic dogs of different breeds, and explore a possible relation with other congenital vertebral malformations (CVMs) in the breed with the highest prevalence of cervical ribs. By phenotyping we hoped to give clues as to the underlying genetic causes. Twenty computed tomography studies from at least two breeds belonging to each of the nine groups recognized by the Federation Cynologique Internationale, including all the brachycephalic 'screw-tailed' breeds that are known to be overrepresented for CVMs, were reviewed. The Pug dog was more affected by cervical ribs than any other breed (46%; P < 0.001), and was selected for further analysis. No association was found between the presence of cervical ribs and vertebral body formation defect, bifid spinous process, caudal articular process hypoplasia/aplasia and an abnormal sacrum, which may infer they have a different aetiopathogenesis. However, Pug dogs with cervical ribs were more likely to have a transitional thoraco-lumbar vertebra (P = 0.041) and a pre-sacral vertebral count of 26 (P < 0.001). Higher C7/T1 dorsal spinous processes ratios were associated with the presence of cervical ribs (P < 0.001), supporting this is a true homeotic transformation. Relaxation of the stabilizing selection has likely occurred, and the Pug dog appears to be a good naturally occurring model to further investigate the aetiology of cervical ribs, other congenital vertebral anomalies and numerical alterations.