Lumbosacral transitional vertebra (LTV) in rhodesian ridgebacks

“Dogs of medium and large size of breed can suffer from a condition called lumbosacral transitional vertebrae (LTV), which means that the dog has a malformed vertebra in the caudal end of the spinal cord. Different types of LTV exist and radiographic screening is used to determine the form of LTV in dogs. The disorder can be seen right after birth and it is hereditary.”

http://www.akcchf.org/research/research-portfolio/02606.html

Firstly it’s important to understand that the lumbosacral transitional vertebra (LTV) isn’t necessarily a disease with clinical signs of illness but a structure of bone which a dog is born with. Most ridgebacks live a completely normal life despite having a lumbosacral transitional vertebra. The unlucky ones may show various symptoms, ie. lameness and unwillingness to jump.

Today screening for the LTV is performed at least in Finland, Germany, Austria, Czech and Slovakia. The scoring in the countries mentioned is not equal and the Finnish Kennel Club has the only fully open health database.

LTV0, rhodesian ridgeback

The prevalence of the LTV in dog breeds ranges from 0% to 40%. The highest prevalence 40% is found in German shephards (Lappalainen A. 2013). Rhodesian ridgebacks are not that far behind; in the Finnish Kennel Club’s database the prevalence is 36% (Dec 2019). The numbers are likely high compared to other countries due to the differences in scaling. In the study of the LTV in Parsonrussellterriers (Järvinen P. 2019) the prevalence was 30%. In this study it was found that dog’s with any grade of the LTV are also more prone to vertebral anomaly (VA). Therefore it’s suggested that all anomalies in spinal area should be payed attention in it’s entirety.

Giffaffes are beautiful wild animal with a very long neck. But how many cervical vertebras they have?

To determinate if a dog has or has not the LTV it needs to be radiographed. The body length, angle of pelvis, hock angulation or something else in dog’s presence do not give any indication of how the sacrum is formed. Even a dog with 8 lumbosacral vertebras has exactly the same total amount of vertebras as a dog with 7 lumbosacral vertebras. It’s just that one lumbosacral vertebra has taken the form from another vertebra!

Back to the giraffe. Majority of the mammals, including giraffes, have 7 cervical vertabras, just like dogs. The length of neck is not affected by the number of the cervical vertebras but the size of them!

LTV predisposes to premature degeneration of the lumbosacral junction, is a frequent cause of cauda equina syndrome, especially in German shepherd dogs and is thought to be hereditary.”

(Lappalainen A., Salomaa R. et al 2012)

By radiographing the cervical spine, thoracix spine, lumbosacral spine and sacrum it’s possible to get grading for the LTV, spondylosis (SP) and vertabral anomaly (VA). InFinland for the LTV and VA scoring the must be at least 12 months old and 24 months old for the spondylosis. Instructions for radiography: https://www.kennelliitto.fi/en/forms/idd-ltv-and-spondylosis-instructions-radiography

normal spine

A normal canine spine consists of 7 cervical (C1-7), 13 thoracic (T1-13), 7 lumbar (L1-7) and 3 sacral vertebras (S1-3) resulting the total of 30 vertebras. Calculation starts from first thoracic vertebra (T1). The number of caudal vertebras (CD) vary.

© Anu Lappalainen

Sacrum connects the lumbar spine to pelvis. It’s a part of the pelvis and it lies between the lumbar spine and tail. Sacrum is strong, triangular in shape and it sits between the hip bones. Normal sacrum consists of three fused vertebral segments; S1, S2 and S3.

https://veteriankey.com/canine-anatomy/
https://veteriankey.com/canine-anatomy/
https://veteriankey.com/canine-anatomy/

the LTV scoring by the finnish kennel club

13+7 = Normal
13+8 = LTV4 (lumbarization)
13+6 = LTV4 (sacralization)
12+8 = LTV0 + VA1 (transitional T13)
14+6 = LTV0, VA1 (transitional L1)

LTV0
LTV0

LTV1; divided median crest (s1-s2)

LTV1
LTV1

LTV2; symmetrical

LTV2
LTV2

LTV3; asymmetrical; on the right in the VD photo the left side of S1 is shaped like a sacral vertebra and on the right side S1 is shaped like a lumbar vertebra including the spinous process.

LTV3
LTV3

LTV4; 8 lumbosacral vertebras. L8 shaped like a lumbosacral vertebra and it has complete spinous prosesses.

LTV4
LTV4

CliniCal relevance

The LTV predisposes ie. to early disc degeneration, disc protrusion and cauda equina syndrome. We are lacking knowledge for instance ridgebacks with cauda equina; have these dogs had some form of the LTV? Based on my personal experience ridgebacks rarely show symptoms due to the LTV but there are individuals with clinical signs of illness too. Some, luckily very few, has had such severe symptoms that putting the dog down has been the only reasonable choice.

There is very little literature existing but divided median crest (LTV1) is supposed to be completely harmless for the dog. 6/8 lumbar vertebras is argued to have a clinically irrelevant nature in some sources while some see it as a risk for early degeneration of the lumbosacral junction.

Rhodesian ridgeback with a rotated pelvis
© Anu Lappalainen

The asymmetrical form, LTV3, seems to be a bit more trouble than the other forms. In some cases asymmetrical form comes with rotated pelvis, which might lead to unilateral development in hips. This is actually very logical; when the pelvis is not straight and in balance there will be uneven bear of weight between hips. In long term this uneven state might cause the worse hip wear sooner than the better hip and lameness and osteoarthritis may occur.

In the Finnish Kennel Club’s database 42,9% of ridgebacks with LTV3 have one hip scored 1-2 degrees lower than the other one, ie. A/C. The score doesn’t tell if the dog’s pelvis is straight or rotated.

“Asymmetrical LTV favours pelvic rotation over its long axis, resulting in inadequate femoral head coverage by the acetabulum on one side. Inadequate coverage of the femoral head favours subluxation, malformation of the hip joint, and secondary osteoarthritis. Asymmetrical hip conformation may therefore be the sequela of a LTV and mask or aggravate genetically induced canine hip dysplasia.”

(Flückiger M., Frank Steffen F. et al 2017)

SPONDYLOSIS

Rhodesian ridgebacks are also affected with spondylosis, which is a degenerative spinal condition. Rhodesian ridgebacks with a LTV appear to have greater predisposition for spondylosis than the ones without it. In the group of 253 rhodesian ridgebacks with any LTV score 25 (9,9%) had also spondylosis. 7/253 had no scoring for spondylosis, mostly because of being too young at time of the radiographing. Dogs with LTV1-LTV4 seem to have double risk of spondylosis compared to dogs without. However the group of 25 dogs is yet too small to make conclusions and more data must be collected. If the dog is seemingly in discomfort and has both LTV and spondylosis it might be difficult to differentiate which one is causing clinical symptoms.

Inheritance

So far there is no study of LTV in rhodesian ridgebacks and there seem to be differencies between breeds. Some studies about LTV in German shephards exist, and it is known that the LTV is hereditary. The genetic pattern is not known yet but there is a ongoing study in Finland (koirangeenit.fi) trying to identify the risk loci.

The gene pool is globally small, and it’s probable that the situation is the same globally considering the spine health. The material in Finland represents lines around the world and “I don’t have it in my lines” definitely doesn’t suite here. If you haven’t screened, you don’t know if your dog has it not.

Breeding recommendations

In Finland all rhodesian ridgebacks that are used in breeding must be radiographed for LTV and spondylosis. There is no limitations based on scoring, but it is recommended not to combine 2 individuals with any spine issues (LTV, SP, VA). Any dog with clinical signs must always be closed out from breeding. In a situation where about one third of the population has some grade of the LTV it’s not even possible to close all dogs with the LTV out. What can be done is to radiograph all breeding material and avoid combining 2 individuals with spine anomaly. Wisdom is to breed with knowledge, not with assumptions!

THE LTV in Finnish RHODESIAN RIDGEBACK population

Finnish Kennel Club has the the offered the LTV scoring from 2013, and since 2018 it has been mandatory to examine all rhodesian ridgebacks used in breeding. In the end of 2019 there was 253 rhodesian ridgebacks with a LTV scoring in Finland. The estimated size of the breed is 861 (2019) dogs which means that 30% of the rhodesian ridgebacks has a LTV score.

36% had some grade of the LTV (LTV1-LTV4). 6 or 8 lumbosacral vertebras is not scored as the LTV in any other country but Finland. The prevalence of the LTV1-LTV3 is 27,4%.

50% of the LTVs is scored as LTV1, which is divided median crest (s1-s2) or other mildly abnormal structure. This mildest form of the LTV is supposed to be completely harmless for the individual, but yet something to think about when breeding. Other mildly abnormal structure is ie. 1st caudal vertebra attached to S3.

The second largest score is LTV4 (6 or 8 lumbosacral vertebras). Most of these dogs have 8 lumbosacral vertebras (lumbarization).

LTV3 was found in 15,2% and LTV2 in 10,9%.

summary

The prevalence of the LTV varies between the breeds and so does LTV’s clinical significance. Rhodesian ridgebacks are for sure yet less clinically affected than ie. German shephards are due to the LTV. More information is needed to make conclusions. It is already known than the LTV and other vertebral anomalies are inherited. To secure rhodesian ridgebacks future as an agile, capable and versatile dog for various sports it is my recommendation to take the spine radiographing as a standard procedure and part of breeding recommendations in all countries.

To discover the correlation between the LTV and cauda equina syndrome and other related conditions in rhodesian ridgebacks there will be an inquiry launched in January 2020.

thank you

My sincerest thanks to all rhodesian ridgeback owners, who shared information about their dog’s health and radiographies!

© 2020 Nina Lindqvist All Rights Reserved


References and must read:

http://www.akcchf.org/research/research-portfolio/02606.html

https://helda.helsinki.fi/bitstream/handle/10138/303809/Pilvi%20J%c3%a4rvinen%20Lisensiaatintutkielma.pdf?sequence=2&isAllowed=y

https://www.koirangeenit.fi/english/projects/ongoing-research-projects/bone-diseases/lumbosacral-transitional-vertebr/

https://helda.helsinki.fi/bitstream/handle/10138/39292/dissertation_lappalainen.pdf?sequence=1

https://pdfs.semanticscholar.org/ad22/73c9eb3fe12ad0d56e76104c971e205224fc.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3403972/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2822375/