Hip dysplasia (HD)

The canine hip dysplasia (HD) is one of the most common musculoskeletal disorders that affects medium-sized to large dogs, both pedigree and mixed-breed dogs. For a few decades, veterinarians, scientists and breeding organizations have been dealing in detail with this disease. Today we know relatively exactly how the disease develops; the causes of the disease are also largely known. Even if there are sometimes different opinions about the triggering factors or their weighting, there is nowadays agreement that HD is largely hereditary and, due to its polygenic inheritance and its multifactorial expression, is influenced by some non-genetic factors.

Disease emergence

If there are genetically determined deviations in the form or interaction of the structures mentioned, such hip joints are referred to as dysplastic. Such a malformation or malformation of one or both hip joints can have different degrees of severity. The form of HD is also diverse. The acetabulum may be too flat and / or the femoral head too small. Any discrepancy in the correspondence of the cup and head is called an incongruence.
Some authors blame muscle anomalies (primarily a shortened pectineus muscle). As a result, the femoral head attached to this muscle is permanently pulled up against the socket wall, which in turn is supposed to lead to the known sequelae.
Another cause of HD is that the joint is too loose, ie the head is not seated firmly and tightly enough in the socket. Reasons for this are, for example, slack ligaments or joint capsules.
Both incongruence and too loose joint closure can lead to secondary degenerative changes over time. These appear sooner or later as a loss of the articular cartilage as well as exostoses and arthroses due to the permanent incorrect loading of the joint surfaces. As an extreme consequence of this, a dislocation of the hip joint can occur. The bony changes that are often found on the x-ray in advanced HD are not symptoms of the actual disease, but rather sequelae. This is known as coxarthrosis.

Causes of the appearance of HD

HD is a genetic condition. In contrast to certain body characteristics and also certain hereditary diseases (including metabolic diseases), not a single gene is responsible. Rather, the ability to develop HD is influenced by different genes; this type of inheritance is also called polygenetic (poly = a lot). This is also one of the reasons why there is no "all-or-nothing principle" with the HD, but all conceivable degrees of severity.
The involvement of various environmental factors also plays a role here. Particularly noteworthy are feeding and exercise. Lately, in particular, the opinion has been heard that HD is an exclusively environmental disease. However, it has been certain for some time that this is not the case. The only question is what part do genes play and what part do rearing and environmental conditions play. A factor of 50/50 is largely assumed today.

The occurrence of HD is different in the individual dog breeds, sometimes even the same breed has a different frequency in different countries. Primarily medium-sized to large breeds are affected.

As we now know, the dog inherits a certain predisposition to develop HD. He already has this disposition at birth. At this point in time, however, a diagnosis is not yet possible, as the features of dysplasia only develop in the course of skeletal development. In some cases, these features can already be identified at an age of a few weeks to months, but a clear and definitive diagnosis can only be made after growth has ended, i.e. from an age of 12 to 18 months. The above-mentioned environmental factors also affect the dog from birth. The type of feeding and the type and extent of exercise are of the greatest importance here. Feeding that is too high in energy or too high in protein has proven to be disadvantageous, especially for large-bred dogs. Excessive physical work, e.g. exercising too early and too long, especially on the steep face, has a negative effect on the development of the hip joints. Tight croup and thigh muscles through moderate, even movement, on the other hand, are beneficial for stabilizing the hips. Optimal rearing conditions, which should be a matter of course for conscientious breeders and owners anyway, are an absolute must for rearing HD-endangered breeds and dogs.

The clinical symptoms of HD range from reduced activity, which is of course particularly noticeable in young dogs, through pain when standing up to passive movement of the hip joint. The veterinarian can use a certain manipulation to provoke a snapping sound of the joint, which is also typical for HD. A reliable diagnosis, however, can only be made through x-rays.

diagnosis

X-rays are still the most important diagnostic tool. For some breeds, breeding approval is mandatory, in general every dog from medium size (including mixed breeds) should be x-rayed at a certain age (at least 12 months) in order to be able to determine incongruences or deformed joint parts.

The dog is sedated for correct HD recording. This is necessary in order to achieve complete relaxation of the muscles. The dog is placed on its back, one person pulls it forward by the front legs, another stretches the hind legs and turns them inward at the same time. The image must be absolutely symmetrical, apart from the hip joints and the iliac wings, the knee joints and kneecaps must also be completely in the picture.

In order to be able to evaluate the recording, the veterinarian must have some experience, at least with the lighter grades, whereby the signs of severe HD can often already be recognized by laypeople. The so-called "official" recordings must be sent to a central evaluation point for evaluation, which differs depending on the breed club.
As early as 1965, the first clubs introduced a breeding ban for dogs with medium and severe HD; since then, the importance of x-rays has not changed, either for diagnostic reasons on a veterinary level or for prophylactic reasons on a breeding level. Until recently, only veterinarians authorized by the relevant breed clubs were allowed to take official recordings, today the situation is such that every veterinarian is officially allowed to take HD X-rays, but is of course also responsible for correct storage and the quality of the recording. Under certain circumstances it can happen that images from the central evaluation point are returned as not evaluable and new recordings have to be made. The "unofficial" recordings, such as the pre-X-ray, should be made just as conscientiously as the official recordings in order to be able to make a reliable statement.
This pre-X-ray at the age of seven to nine months makes sense if a working dog owner wants to know whether the beginning of intensive training for the dog is acceptable from a veterinary point of view, or whether there are already corresponding changes in the hip joints. Of course, a statement at this age can only be made with reservations, specific information on the condition of the hip joints with regard to HD can only be made after the epiphyseal has finished growing, for this reason the time of the official X-ray is never before the end of the twelfth month of life.
As mentioned earlier, diagnosing HD based on X-rays requires a certain amount of experience on the part of the veterinarian. There are certain criteria for assessing the severity that the evaluator must also be familiar with. The position, the shape of the socket, the shape of the head of the femur, the position of the head in the socket, the neck of the femur and the joint space must be assessed.
In addition, the so-called NORBERG angle is measured. This measurement, which is carried out directly on the X-ray using a special template, allows an additional objective assessment of the hip condition. A value of 105 ° or more is desirable; lower values indicate flat pans or loose hips.

Of course, there are race-related anatomical differences in the hip joint that the assessor should be aware of. Chondrodysplastic breeds such as Basset, Dachshund and sometimes Cocker Spaniel are to be assessed differently than breeds with normal bone and cartilage growth such as German Shepherd Dog, Doberman, Hovawart, etc. Large breeds such as St. Bernard or Great Danes should also be X-rayed later than smaller breeds, because their bone growth is accordingly completed later. An age of 18 months is a guideline.

Depending on the extent of the radiographically detectable changes, a classification is made into different degrees of severity. These are normal (A) for joints with a NORBERG angle of 105 ° or more, almost normal, transition or HD suspicion (B) with minor changes in the head or socket and a NORBERG angle of at least 100 ° . Slightly more pronounced deviations can be found in slightly (C), as well as incongruence and possibly a diverging joint space. The NORBERG angle is around 100 °. With moderate HD (D) there are more serious changes with arthritic growths. The NORBERG angle is between 90 ° and 100 °. Finally, in severe HD (E) the entire joint is severely changed. There may be a complete dislocation, at first glance you can see the arthritic changes and the NORBERG angle is less than 90 °.

X-rays are therefore the most important means of diagnosing an existing HD. However, since not every dog is routinely x-rayed, we would also like to point out possible clinical symptoms that can occur with existing HD. Mind you, because even with a medium to severe HD according to the X-ray image, it can happen that the dog moves without major problems and is also pain-free. Last but not least, this should be a reason to have your dog X-rayed in any case, even if it is not a pedigree dog or an animal intended for breeding. In most cases of manifest HD, there are symptoms that the dog owner will notice and also cause him to visit the vet. These include primarily signs of lameness in the hindquarters, pain during both active and passive movement, and difficulty getting up.
Very often, especially in predisposed breeds such as the German Shepherd Dog, Rottweiler, etc., any movement disorder or pain in the pelvic area is already interpreted by the owner as HD. However, in order to differentiate between other diseases that can also occur in these breeds, a veterinary examination including an X-ray is essential.

HD Grade and their meaning:

HD - A1 HD- A2
No reference to HD


HD- B1 HD- B2
Borderline case, transitional form


HD- C1 HD- C2
Light HD


HD- D1 HD- D2
Medium HD


HD-E1 HD-E2
Heavy HD


The number after the degree stands for the tendency towards the previous or next degree.


The Cane Corso is approved for breeding in Germany up to HD-C.

Elbow dysplasia

Elbow dysplasia (ED) is a chronic disease complex of the elbow joint in fast-growing dog breeds. ED is an inherited developmental disorder of the growing skeleton. High body mass growth and feeding errors are further favorable (predisposing) factors. ED begins in the late growth phase in four to eight month old young animals with a painful change in the joint and the joint-forming bone parts (osteoarthritis) with lameness. The range of motion of the elbow joint is restricted. Early signs are stiffness in the morning or after rest. The disease progresses lifelong and cannot be cured, but in many cases it is largely free from pain.


This image is based on the elbow dysplasia image from the free media database Wikimedia Commons and is licensed under the GNU Free Documentation License. The author of the picture is author Uwe Gille

Elle (left) and radius (right) with severe osteoarthritis (ED grade III).

Occurrence and causes


Elbow dysplasia can occur in any large breed of dog. Chow Chow, Rottweiler, Bernese Mountain Dog, Greater Swiss Mountain Dog, Newfoundland Dog, Labrador Retriever, German Shepherd Dog and Bordeaux Mastiff are most commonly affected. The frequency of occurrence (prevalence) is over 40% in some breeds.

ED is inherited polygenetically (through several genes). The exact inheritance and the genes involved are not yet known, so that no genetic test for the disease exists. So far, proof can only be provided through the veterinary assessment of the individual animal, some dog breeding associations require an X-ray examination for breeding animals. The degree of heritability is greater for males than for females and is given as values between 0.1 and 0.7 depending on the breed and population.

Clinical symptoms


The diseased animals are conspicuous by lameness in the area of the forelimbs. There is a mixed form of lame and support leg lameness, often the forearm and paw are moved away from the normal axis of the limb (abduction) and the elbow is drawn towards the body (adduction), whereby the limb is twisted. During the clinical examination, an increased filling of the joint capsule can often be found, the joint is usually painful and sometimes grinding noises such as pseudocrepitations can be triggered.

Manifestations


Elbow dysplasia occurs when the joint-forming bones of the upper arm bone (humerus), ulna (ulna) and radius (radius) do not fit together exactly enough. The imprecise fit or incongruence leads to chronic remodeling processes at the elbow joint and the joint-forming bone parts (osteoarthritis), which lead to sclerotherapy of the bones and the formation of osteophytes. If the joint surfaces are only slightly incongruent, osteoarthritis is the only sign of elbow dysplasia, and other changes can also occur:

1. Fragmentation of the medial coronoid process (FCP, detachment of the inner coronary process of the ulna)
2. Osteochondrosis dissecans on the condylus medialis humeri (OCD, cartilage detachment on the inner roll cusp of the humerus)
3. Isolation of the anconal process (IPA, detachment of the elbow process from the ulna)

It is common to have more than one of these complications at the same time. Occasionally, in German-speaking countries, other developmental disorders such as the lack of fusion of the three elbow-sided ossification nuclei of the humerus and the congenital elbow dislocation or subluxation in small (so-called chondrodystrophic) dog breeds are classified in the elbow dysplasia complex. The latter also favor the occurrence of an IPA or FCP, but are not counted as part of the ED complex by the International Elbow working Group.


Typical ED manifestations
1 step formation between ulna and radius
2 Isolated anconeal process
3 Fragmented medial coronoid process
4 OCD of the medial condyle

Fragmentation of the medial ulna coronoid process (FCP)
Various mechanisms are discussed as the cause of the detachment of the medial coronoid process (fragmented coronoid process, FCP):

* Growth retardation of the spoke with shortening of the same (short-radius syndrome), which leads to increased strain on the ulna. This leads to bone compression (sclerosis), deformation and finally to detachment of the medial coronoid process.
* Premature epiphyseal plate closure of the radial head.
* Disturbed fine blood circulation (microvascularization) due to mechanically induced sclerosis of the bone in the area of the coronary process.

The disease occurs at the earliest between five and seven months of age. Under certain circumstances, however, the owner does not notice it immediately, so that animals are only presented to the vet when they are two years old. Clinically, an FCP manifests itself as lameness, which occurs mainly after prolonged rest or greater exertion. The elbow is exposed to the side.

The clinical examination reveals painfulness when the joint is greatly extended or flexed. In the X-ray image, the shadows in the ulna area, the loss of the trabeculae, an indistinct anterior contour in the latero-lateral beam path (lateral projection) and, if applicable, the fracture line of the process are visible. However, a complete avulsion of the coronoid process is rare. Due to the lack of congruence, a step between the radius and ulna and an unevenly wide joint space can appear. This incongruence can be represented by means of a quotient. For this purpose, the length of the trochlear notch and the distance between the tip of the anconal process and the tip of the ulnar coronoid process are measured. If the quotient of both values is above 1.15, the elbow joint is considered incongruent. The arthrosis associated with FCP manifests itself in more severe forms in lip formations of the adjacent bone contours. Bone attachments occur mainly on the inner (medial) edge of the ulna and the humerus. Arthroscopy can support the diagnosis of FCP.


Osteochondrosis dissecans humeri
Osteochondrosis dissecans (OCD) occurs in the area of the elbow joint almost exclusively on the inner roll cusp of the humerus (condylus medialis humeri). It usually arises at the age of 5 months and usually on both sides. More commonly affected breeds are Labrador Retrievers, Golden Retrievers, and Rottweilers. [6]

This form of elbow dysplasia is often associated with a fragmented coronoid process. [9] However, a “real” OCD is usually confused with the cartilage erosions (kissing lesions) in an FCP, which do not affect the (subchondral) bone tissue located under the articular cartilage, so that Read [6] doubts the simultaneous occurrence of both lesions.

The diagnosis can usually be made on the basis of an X-ray image, especially in the anterior-posterior beam path (projection from front to back). However, X-ray evidence is not always successful, so that reliable exclusion can only be made using an arthroscopy or computer tomography (CT).

Isolated anconeal process (IPA)
An independent (isolated) elbow process of the ulna is a hereditary disorder of enchondral ossification and was first described in 1956. In the case of IPA, there is no fusion between the ulna and its anconeal process, which has its own ossification center, which usually fuses with the ulna between 18 and 24 weeks of age. At this age, there is a risk of partial or complete tear-off due to trauma or the failure of the joint to close due to high physical activity due to reduced elasticity. Another cause discussed is a reduced growth in length of the ulna (so-called short ulna syndrome). An oversupply of calcium and phosphorus favors the occurrence of an IPA. Rottweilers and German Shepherds are affected above average. The disease is more common in males than in females. In about 60% of the cases, an IPA occurs unilaterally.

The diagnosis is made on the basis of an X-ray with the joint in the flexed position, whereby it should be noted that the anconeus process only fuses with the ulna at about six months. The fracture line is clearly visible in most cases, there is also sclerosis of the affected area and, with prolonged existence, bone extensions.


Classification


According to the International Elbow Working Group, ED is divided into three clinical stages depending on the extent of the disease. Here, only the severity of the osteoarthritis is assessed via the extent of the bone formation (osteophytes). The occurrence of specific lesions (FCP, IPA, OCD) is only noted, but not used for classification:


Severity - Criteria


Grade 0: Normal - no osteophytes or sclerosis
Grade I: Mild osteoarthritis - osteophytes smaller than 2 mm or sclerosis of the joint surface (incisura trochlearis) of the ulna
Grade II: Moderate osteoarthritis - osteophytes between 2 and 5 mm in size
Grade III: Severe osteoarthritis - osteophytes larger than 5 mm

therapy
Detached skeletal (FCP and IPA) or cartilage parts (OCD) should be surgically removed, as they exert a constant stimulus on the joint capsule. This removal should be done as early as possible, i.e. before osteoarthritis develops. An IPA can also be fixed again by means of osteosynthesis. Then the animal should not be moved at all for two to four weeks if possible (leash, rest in the box) and then only little room to move for the same time. If there is also an incongruence in the joint, surgical removal of the detached fragments alone is not sufficient. Surgical cutting (osteotomy) of the ulna is usually performed here. However, all surgical measures often do not prevent the progression of osteoarthritis. It can be used as a companion dog, but harder work such as working dogs is not recommended. An endoprosthesis may be indicated in severe elbow dysplasia.

A pain reliever and anti-inflammatory therapy is useful. Here, mostly non-steroidal anti-inflammatory drugs such as carprofen are used. A study published in 2006 showed good tolerability of two-month therapy with carprofen in dogs and no evidence of toxicity to the kidneys or liver.

Weight reduction is strongly recommended for overweight animals.

The effectiveness of alternative medical forms of treatment (acupuncture, gold implants, homeopathy) has not yet been proven by randomized control studies. A current evidence-based study could not prove any positive effects of electroacupuncture. A daily administration of gelatine as granules in the feed should prevent osteoarthritis or at least delay it.

Dogs with ED should be excluded from breeding because of inheritance.



This article is based on the article Elbow Dysplasia-Status July 19, 2007 from the free encyclopedia Wikipedia and is under the GNU License for Free Documentation . A list of the authors is available on Wikipedia.