Mon, 08/30/2021 - 2:02pm

Hemivertebra and Kinked Tails

Merry Fitzgerald discusses spinal anomalies in dogs


The vet says my dog has a hemivertebra. What is that?


Hemivertebra in dogs is a congenital condition where the dog has one or more deformed segments of vertebra, which are the bones that make up the spine.

“Congenital” means that they are born with the deformity. “Hemi” means half, and, in this case, it refers to the formation of a partial vertebra. Normal vertebrae, are spool-shaped when viewed from the side. A hemivertebra will appear as a wedge or triangle. It may be fused to another vertebra or wedge-shaped, leading to misalignment and twisting in the spine.

This condition may or may not cause problems. The symptoms your dog experiences as a result of hemivertebra depend on the location of the hemivertebra and how many vertebrae are deformed. If the deformed bones compress the spinal cord or weaken the spinal column, the dog may experience pain, weakness and difficulty walking, as well as urinary leaking and/or fecal incontinence.

In problem cases, most symptoms occur at a young age. Initially, the signs continue to worsen until reaching a stable plateau once the vertebrae stop growing.

Hemivertebra is a common finding in many breeds, especially those bred to have “screw tails,” including the Bulldog, Boston Terrier, Pug and French Bulldog. German Shorthaired Pointers and German Shepherd Dogs can experience this condition by inheriting an autosomal recessive gene. The mode of inheritance in other breeds is not known.

A preliminary diagnosis of hemivertebra is made by taking simple radiographs. The affected vertebrae are usually in the thoracic, or rib cage, region of the spine. When dogs have signs of related spinal disease, a more defined diagnosis may require sophisticated imaging studies. In veterinary medicine, compression of the spinal cord is usually diagnosed by myelography. This X-ray technique uses an injectable dye to show where and how the compression is occurring.

Advanced imaging is increasingly available, and the use of CT scans and MRIs can give detailed information to aid in reaching a definitive diagnosis. Cost is definitely a factor, as the price of these scans can range from $1,000 to $3,000.

Dogs experiencing mild pain associated with hemivertebra-associated spinal compression respond well to rest and anti-inflammatory drugs. If the compression is more significant, surgery is usually necessary to relieve the pain. The surgical procedure is called a hemilaminectomy. The material of the disc that is pressing against the spinal cord is removed and the spine is stabilized. Surgery can cost anywhere from $1,500 to $4,000 for one location, and significantly more if multiple segments of the spinal cord are affected.


What causes kinked tails?


The tail is an extension of the spinal column, which is made up of several different kinds of vertebrae. These different types of spinal segments vary slightly in size and shape according to their function. Some dogs are born with abnormalities in the shape of their tail. As long as the defect is only found on the tail, the problem is only cosmetic. The exception to this would be a deformity in the vertebra close to the base of the tail, which interferes with the dog’s ability to lift the tail while defecating.

Another concern is that using a dog with a malformed tail in a breeding program might result in puppies with serious defects in other parts of the body, as well as the tail. When the skeleton of an unborn puppy develops, the heart, blood vessels and urogenital systems develop in the same embryologic layer. Defects in the development of the spinal column are an indication there may also be abnormalities in the formation of the skull, kidney, bladder and heart. In more serious cases, cleft palate, hydrocephalus (water on the brain), wry jaw, deformed ribs, extra or missing toes, and short legs can be seen.

The presence of kinks in the tail, especially the tip of the tail, often go unnoticed in breeds that are docked. The breeds that are docked typically have the procedure done when the puppies are three to five days of age. It may be important to note in their medical records which puppies have a kinked tail when they are docked to see if any other anomalies develop as the puppy grows. This is also information to consider when planning a breeding program and to pass on to the future owner.

Smaller kinks that are the result of tendon or ligament contractions, and not deformed vertebrae, can often be straightened out with gentle manipulation in the first few days of life. You can use masking tape to make a light splint around the tail. The tape should be tight enough to straighten the tail, but not so tight that the blood circulation may be affected. The splint should be changed every two days as the puppy grows. Usually, you only need to lightly splint the tail for seven to 10 days.

Tails can also become kinked as a result of injury. If a bone segment in the tail is fractured or if two vertebrae are dislocated, the tail may kink as it heals. Certain types of trauma can lead to a crooked tail. People accidentally step on or close a door on their dog’s tail. Rough play, bite wounds, and striking the tail against a wall or hard object while wagging can also lead to kinks. These types of injury are definitely painful initially, but once the hurt subsides, the bent-tail problem is strictly cosmetic.


What is “screw tail”?


Screw tail is a descriptive slang term for the short, corkscrew-like deviation of the tail most commonly seen in the Bulldog, French Bulldog, Pug and Boston Terrier. The shape of the tail is due to the malformation of one or several vertebrae in the tail. A straight, normal-length dog’s tail can be made up of up to 23 vertebrae. The abbreviated length in a screw tail is the result of genetic selection for shortening of the tail by eliminating the number of vertebrae in the tail. Some screw tails only have four or five vertebrae. These two traits – the misshape and small number of spinal segments – produce the characteristic screw tail.

When the bend in the tail is close to the body, the tail can appear inverted or ingrown. Deep skin folds have a natural tendency to accumulate moisture. This can lead to an infected, painful and itchy skin-fold dermatitis, known as intertrigo, surrounding the tail. Severe cases of screw tail partially obstruct the anus, making it difficult to defecate. Feces and anal-sac fluid accumulate, worsening the infection. These dogs have a terrible odor from the infection, and may scoot and rub their rears on the floor or carpeting.

Mild cases can be treated with antibiotics and managed by keeping the skin folds clean and dry. More severe cases require surgery, which involves amputating the end of the tail and removing the infected skin fold. This is a challenging procedure and is best performed by a board-certified veterinary surgeon. The risk of fecal incontinence is a real concern, but a rare complication under the care of an experienced surgeon.



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