Understanding Angular Deformities in Dachshunds

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Dachshund breeders and owners have likely heard about bowlegged syndrome, angular hock deformity, easty-westy feet, and Queen Anne fronts, terms describing potentially crippling angular limb deformities (ALDs). These inherited developmental abnormalities that occur during growth relate to the spatial misalignment of bones in a dog’s legs resulting in joint incongruity and oftentimes painful lameness.

Although ALDs have been recognized for more than 40 years, they continue to baffle breeders and owners when they see the legs and feet of their pick-of-the-litter puppy turn inward or outward. These otherwise happy, boisterous puppies often struggle to walk, sometimes dragging their feet or hopping along.

Dachshunds chosen to continue a breeding program, many slated as hopefuls for dog shows, field trials or companion sports, end up in pet homes. Because the mode of inheritance of the conditions is unknown, breeders could unwittingly proliferate the occurrence of ALDs in the breed.

ALDs affecting the rear legs are pes varus, which is Latin for “foot inward,” an apt description of the bowlegged syndrome or angular hock deformity, and pes valgus, meaning “foot outward” in Latin and describing the easty-westy appearance. Similarly, ALDs affecting the front legs are carpal varus, Latin for “wrist inward,” and carpal valgus, Latin for ”wrist outward,” also known as a Queen Anne front or easty-westy. These conditions can be unilateral, occurring in one leg, or bilateral, seen in both legs.

ALDs are diagnosed in all coat color and size varieties of Dachshunds. Anecdotally, these orthopedic disorders are believed to be occurring more commonly.  

Deneice “Denny” Van Hook, DVM, president of the Dachshund Club of America Health & Welfare Trust Fund, says, “ALDs are cropping up in bloodlines you would not expect to see them in. Because the conditions are not apparent at 8 weeks of age, they are not recognized early and often puppies have been placed in homes before being diagnosed.”

Early detection and treatment of ALDs improve the prognosis for long-term health. While mild-to-moderate cases can be treated medically via supplementation, proper nutrition and weight management, severe cases may require surgery. The surgical cost varies based on the geographical area and specialty clinic, though it averages $5,000 per leg to correct a pes varus deformity.

“Surgical correction for ALDs should be considered with dogs having clinical signs of lameness and pain,” says Bryan Torres, DVM, PhD, DACVS-SA, DACVSMR, associate profess of veterinary orthopedic surgery at the University of Missouri. “The key with these dwarf breeds is to identify what is ‘expected’ versus what is ‘excessive’ in regard to changes in the bones and limbs.”

Dachshunds and other chondrodysplastic or dwarf breeds, such as Basset Hounds, Pembroke and Cardigan Welsh Corgis, have a genetic predisposition for developing ALDs. Notably, ALDs also occur from growth plate injuries or trauma, though this is seldom the case with Dachshunds.

“ALDs in Dachshunds are associated with chondrodysplasia,” says Danika Bannasch, DVM, PhD, the Maxine Adler Endowed Chair of Genetics at the University of California-Davis. “An FGF4 retrogene insertion on canine chromosome 18 explains the short-legged phenotype known as chondrodysplasia, which contributes to orthopedic disorders such as ALDs by causing the stunted growth of certain bones.”

The FGF4-18 retrogene insertion discovery was made in 2009 by researchers at the National Institutes of Health who were studying breed sizes and morphology.1 A retrogene results from the retrotransposition of messenger RNA (mRNA). All cells have an RNA molecule that transcribes the DNA from the cell’s nucleus to the cytoplasm, or ribosomes, where it is synthesized into protein.

“Other factors besides having chondrodysplasia are likely to be contributing to the ALDs’ phenotype,” says Dr. Bannasch, who discovered the FGF4-12 retrogene insertion linked to the causative variant of the chondrodystrophy phenotype.2 “We do know that chondrodysplasia is associated with carpal valgus, while chondrodystrophy is not. How these two retrogenes may work together to exacerbate proper bone development leading to ALDs is unknown. Since most Dachshunds have two copies of both retrogenes, there may be additional genetic or environmental factors involved.”

Advising breeders on how to avoid producing dogs with an ALD can’t be done. “Until more is known about the genetics behind each of the ALDs affecting Dachshunds, it is impossible to provide sure recommendations to breeders,” Dr. Bannasch says.

Pes varus is the most common ALD seen in Dachshunds, according to Dr. Torres.

The bowlegged appearance of a dog with pes varus is usually the first clinical sign. It occurs when the growth plate of the distal tibia, or shinbone, closes prematurely. This causes asymmetrical growth of the tibia and an inward, or varus, angulation of the distal tibia. Because the distal portion of the affected tibia is not level to the ground, though the lateral side is, the affected leg looks bowlegged.

Pes varus usually occurs in Dachshunds between 4 and 6 months of age and ranges from mild to severe. Those with a mild case may show no clinical signs, though the younger the age in which the growth plate closes, the more severe the deformity.

“Patients that have lameness typically need surgery to straighten the leg and to help get the loading of the joint as close to normal as possible,” says Dr. Torres. “Without treatment, dogs can develop arthritis in affected joints as they age. On the other hand, mildly and some moderately affected dogs adapt well with seemingly no pain or limitation in their ability to get around.”

Surgery to correct pes varus is an opening-wedge osteotomy. “We essentially make a cut in the bone, straighten out the bone and put either a bone plate on the inside of the tibia or use an external skeletal fixator to stabilize the bone,” explains Dr. Torres. “As the bone is straightened, a pie-shaped wedge is created and in some cases bone graft is used to help encourage and speed bone healing.

The encouraging news is that once the surgeries are completed and the dog is on the mend, the outlook for his being able to participate in normal activities is good.

1 Parker HG, VonHoldt BM, Quignon P, et al. An Expressed FGF4 Retrogene Is Associated with Breed-Defining Chondrodysplasia in Domestic Dogs. Science. 2009;325:995-998.

2 Brown EA, Dickinson PJ, Mansour T, et al. FGF4 Retrogene on CFA12 Is Responsible for Chondrodystrophy and Intervertebral Disc Disease in Dogs. PNAS. 2017;114(43): 11476-11481.

 

 

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