Canine hip dysplasia (CHD), abbreviated as CHD, is a common disorder of hip development or growth abnormalities in medium to large dogs. The exact etiology and pathogenesis of CHD is determined by a number of factors. It is now generally recognized that polygenic inheritance, environment and nutritional status are the main factors affecting the formation and occurrence of the disease.
Side view of a German Shepherd Dog skeleton from the web
This is a detailed view of the side view of a dog's skeleton. The area circled in orange is where the pelvis meets the hind legs, and is the site of CHD, the "hip joint".
To understand CHD and read and understand this article successfully, we need to first understand a few terminology concepts through the diagram below.
Enlargement of the Hip Joint from the Web
As you can see in the diagram, the hip joint in dogs consists of two parts: the acetabulum and the femoral head. The head of the femur at the top of the femur is embedded in the acetabulum on the hip bone, with strong ligaments (not shown) and layers of cartilage between the two parts. The close union of these structures ensures that the joint can move flexibly while bearing a great deal of weight.
When these structures fail, the femoral head and acetabulum do not meet well, and it is the ligaments and cartilage between them that are at the root of the problem. When the ligaments and cartilage fail, the tight fit of the hip joint ceases to exist.
Let's take a closer look at CHD in the following section.
Cartilage and ligaments from the web
Ligamentous tissue
Location: in and around the femoral head.
Function: Holds the femoral head in the acetabulum with strong pulling forces.
Problem: In dogs with CHD, the ligaments can become lax, causing the femoral head to loosen and slip from the acetabulum.
Cartilaginous tissue
Location: Femoral head and outer layer of the acetabulum.
Function: Ensures smooth gliding between the joints.
Problem: In dogs with CHD, this layer of cartilage breaks down, erodes, and the joint goes from "cartilage to cartilage" to "bone to bone".
In summary: Because of the abnormalities in the ligaments and cartilage between the joints, there is erosion and subluxation of the normal structure, which leads to unnatural friction and collision between the head of the femur and the acetabulum.
What does CHD bring to the body?
Normal & Abnormal Comparison Source: Internet
Changes in the femoral head
Because of the unnatural friction caused by the structural abnormalities, the previously smooth and rounded femoral head is smoothed out or peppered with growths.
Changes in the acetabulum
The acetabulum, which used to be just big enough to hold the femoral head, likewise becomes rougher and at the same time shallower.
Inflammation and pain
Everything ****s together, the periosteal ligamentous protofibers form a synovial inflammation, the joint capsule becomes progressively thinner, the cartilage membrane overgrows to form bone spurs, and the entire hip joint becomes grotesquely twisted. With the development of time, inflammation and pain will have an increasing impact on the dog.
The process of CHD leading to these structural changes all takes time, either months or years, and each affected dog is affected by a combination of factors.
Which dogs commonly develop CHD?
CHD can occur in dogs of all breeds and sizes, but is most common in large, fast-growing young dogs, and is rare in adult dogs with a normal body weight of less than 11-12 kilograms. The likelihood and severity of CHD is higher in breeds with a normal body weight over 27kg.
Official data: According to the statistics of OFA (Orthopedic Foundation for Animals), the following dogs are most likely to suffer from CHD according to the incidence of the disease in descending order.
However, in China, because of the differences between the breeds of dogs raised by the people and those raised abroad, the common breeds of dogs will also be different. According to domestic clinical case statistics, CHD is more common in Golden Retrievers, Labradors, Alaskans, German Shepherds, Samoyeds, Rottweilers, etc.
Domestic dogs are more likely to suffer from CHD.
High prevalence of CHD in domestic dog breeds from the Internet
In addition to large dogs, bulldogs, pugs, etc. are also commonly affected by CHD breeds, due to the specificity of the bone structure, it is very easy to be affected by CHD. However, the development of CHD in these breeds is usually not fast, and even when it does occur, it often takes years to show significant abnormalities.
Manifestations of CHD
Clinical signs of canine hip dysplasia vary widely, from months to years of age, and from very mild discomfort to severe lameness.
In early puppies, hip dysplasia is not very painful without severe degenerative joint disease and wear and tear. Once degenerative arthritis occurs, pain will begin to appear; adult dogs develop more severe hip dysplasia, in addition to the symptoms of shifting the center of gravity of the body to the front limbs. the common clinical manifestations of CHD are as follows:
Behavioral abnormalities
1 hind legs stand in an X-shape, the thighs are thin and lack of muscle
2 jumping ability is poor, the hind limbs bouncy Like a rabbit
3 Walking posture is strange, running in a three-legged hopping position
4 Hesitantly refuses to climb stairs, and deliberately avoids using a particular hind limb
5 Barking and whimpering when touched to express pain
Activity abnormalities
1 Reluctance to be active and reduced activity at a young age
2 Appears hesitant to get up when resuming exercise from rest
2 Appears hesitant to get up when returning to work from a rest. hesitant and slow to get up when returning to exercise
3 frequent intermittent or persistent lameness of varying severity
4 distraction by licking the fur, and in severe cases, licking parts of the body bald
5 bedsores and calluses on elbows and hips due to prolonged lying down
Tests for CHD
There are three tests commonly used by physicians in veterinary hospitals Ortolani, PennHip, and OFA are commonly used by doctors in veterinary hospitals to diagnose CHD in hip disease.
The Ortolani test
This method is often performed when the dog is 10-12 weeks of age. It is a relatively simple palpation that does not require special equipment, but is not generally accurate enough to be of definitive diagnostic and prognostic value.
The test is usually performed by laying the dog on its side, stretching the hind legs back and trying to rotate the base of the thighs to see if the dog is in pain. In addition, the doctor may also ask you to take your dog for a few steps, and if your dog has CHD, there may be an audible and visible movement in the hip area.
Ortolani test image from the web
PennHip
This is an early diagnostic method using x-rays to determine the degree of hip laxity in puppies by calculating the Dissociation Index (DI), which can screen for CHD in dogs as young as 4 months old. This test was invented at the Pennsylvania College of Zoological Medicine in Pennsylvania.
How it works: A qualified veterinarian takes three precise X-rays of the joint in three states: relaxed, stretched, and squeezed. The smaller the difference between the three, the greater the stability of the joint - and the lower the chance of CHD.
PennHip test image from the web
OFA
This method is a subjective hip scoring method that is performed at 24 months of age and has a high degree of accuracy. the OFA technique has a high degree of authority in the diagnosis of CHD, but is clinically late in the diagnosis of a 2 year old adult dog, when the morphology of the hip joint has already been established.
Test method: 2 standard radiographs (ventral-dorsal and ventral-frog) are taken and the dog is scored by 3 OFA specialists by the position of the hip in relation to the femoral head and the degree of inflammation of the joint, which is categorized into 7 grades, i.e., normal (excellent, good, satisfactory), probable, or dysplastic (mild, moderate, severe, and very severe).
OFA scoring criteria Source from the Internet
X-ray test, can only let us know to a certain extent that the dog has no joint disease at present , but in general, if the X-ray taken at the age of 2 years has not shown signs of CHD, according to the scientific way of raising, the dog later on the probability of CHD is not too high. Another common method of assessing CHD by radiography is the Norberg Angle Diagnostic Method, which is a quantitative method of assessing hip laxity and will not be discussed in detail in this article.
For radiographic evaluation, positioning is very important. Most dogs will inevitably be nervous, fearful, and mobile during an x-ray, so a shot of sedation is needed during the x-ray to ensure more accurate results.
Treatment of CHD
Currently, there are three types of treatment for CHD: conservative treatment, early intervention, and post-treatment.
Conservative treatment
Conservative treatment is a non-surgical treatment that reduces the pressure on the hip joint and prevents the further development of hip dislocation through weight control, exercise restriction, impact protection, and warmth and cold protection in the early stages of detection.
The dog's joint pain can be relieved with medication prescribed by the doctor. If necessary, you can use physiotherapy to treat your dog's hip, such as hip manipulation and hydrotherapy.
Conservative treatment from the internet
Early intervention
Early intervention is a surgical procedure that is performed in puppies after the Ortolani test and imaging of the joints and hips have been evaluated. If the dog is found to be at risk of developing severe hip dysplasia, surgical intervention at the appropriate age can result in a high cure rate.
At 3.5 to 4.5 months of age, a puppy symphysis pubis anastomosis (JPS) is performed; at 5 to 8 months of age, a double pelvic osteotomy (DPO) is performed.
Postoperative radiographs of a case of PDO
Postoperative treatment
Postoperative treatment includes the use of femoral head and neck excision (FHO) and canine total hip replacement (THR).
FHO is a surgical procedure that removes the head of the femur so that the hip joint does not wear out and become painful. FHO is not indicated for dogs weighing more than 20 kilograms and requires more than six months of recovery time for mobility after surgery.
Diagram of the FHO procedure from the web
THR surgery can be performed at any stage of a dog's disease, and hip replacement is the only option for dogs with severe CHD weighing more than 20 kilograms. The success rate of this procedure is about 95%, and the joint prosthesis can last for more than 15 years, which is basically for the lifetime of the dog. However, the difficulty of THR surgery is that it is expensive and there is a scarcity of surgeons in China who can do hip replacement for dogs, who are generally orthopedic specialists.
THR surgery illustration from the web
In summary, all treatments should be done in a timely and effective manner to maximize your dog's freedom from the pain of CHD.
Be a qualified scientific breeder
CHD is a polygenic genetic factor dominated disease. We know that breeding relatively healthy dogs through eugenics at the genetic level will result in a much lower incidence and severity of the disease.
However, correcting the disease through selection is a complex systematic program, and it is difficult to breed to avoid or prevent the development of severe hip dysplasia in the offspring. Our priority is to try to improve the quality of life of our puppies through comprehensive early diagnosis and selection for early intervention to correct potential CHD.
Healthy Running Photo from the web
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