Fragmented coronoid process and osteochondrosis dissecans in the elbowjoint of joung, fast growing dogs.

Fragmented coronoid process and osteochondrosis dissecans in the elbowjoint of young, fast growing dogs.

(S. Schleich)

Introduction:

Osteochondrosis (-chondritis) of the elbow joint and/or fragmented coronoid process of the ulna are diseases of increasing importance in young and fast growing dogs of larger breeds for the last twenty years after they had been described for the first time. These diseases result in lameness and secondary arthrotic changes which influence the dog's further employment.

Aetiology:

Osteochondrosis (OCD) of the elbow joint is, like in other joints, defined as disturbance of enchondral ossification of the jointcartilage during the period of fast growing. The cartilage of the medial humeral condyle thickens, resulting in nutritional failure and leading to the development of fissures or cracks in the surface of the cartilage. In many cases cartilaginous pieces can be found, sometimes as free jointbodies.

Fragmented coronoid process (FCP):

The distal joint surface of the elbowjoint is shaped by two different bones. The proximal radius, carrying about 80% of the bodyweight during load and the proximal part of the ulna with a small lateral coronoid process and a bigger medial coronoid process both contributing about 20% of the bodyweight received from the distal humerus.

The medial coronoid process consists of cartilage until the 4.-5. month of life until ossification starts. During this period it is very sensitive for stress.

Picture 1: distal humerus with lateral and medial epicondyle, Picture 2: distal part of the elbowjoint capitulum humeri and humeral trochlea, which articulates consisting of the proximal ulna and

with the med. coronoid process radius

Since it is not entirely understood why the coronoid process fractures, many possible aetiologies have been discussed, some of them representing a combination of individual theories.

Disturbance of enchondral ossification like in OCD-lesions is one possibility.

In addition a step between ulna and radius (ulna too long) during growth can result in a stressfracture of the medial coronoid process. A to small semilunar trochlear notch leading to cranial subluxation of the humeral condyle and overload of the medial coronoid process can be an alternative reason.

Both diseases, FCP and OCD can occur in one joint, but frequently both frontlegs are affected.

Picture 3: dorsal view of the distal part of the elbowjoint

with an intact small lateral and bigger medial coronoid process

Both, fissures or cracks in the region of humeral trochlea and fractures of the medial coronoid process allow a contact between subchondral bone and degenerated material with synovial fluid causing inflammation, joint effusion, pain and lameness and secondary arthrosis (degenerative arthrotic changes) later on.

FCP and OCD occur frequently in breeds like Rottweiler, Golden Retriever, Labrador Retriever, Bernese Mountain Dog, Newfoundland, St. Bernhard and German Shepherd dog.

Most of the affected dogs show a higher bodyweight compared to other puppies of the same age ( weight about 17-25 kg and higher).

Males are up to three or four times as much affected as females (possibly the result of the higher bodyweight and the faster growth of males).

The disease develops during the 4.-5. month of age, when the highest rate of growth takes place.

The development of OCD and/or FCP is promoted by overnutritition (high protein, high energy, additional supply of minerals, Ca++) because the genetic predisposition for fast growing will be used and disturbances of enchondral ossification becomes more likely.

Dogs with early exercise are more often affected.

Clinical examination:

Lameness can occur in the age of four or fife month. In the beginning the puppy shows a mild to moderate lameness sometimes intermittent and mutual. Occasionally only a stiff and shortened gait is visible. Particular when the disease affects both elbows, owners notice first signs of lameness of one leg after an additional trauma, resulting in intensified pain of one elbow. At this time the dogs may have reached an age of 10-14 month and secondary arthrotic changes have increased.

In addition to lameness the dogs hold their elbows close to their chest and show an outward rotation of the paws.

The affected joints may show effusion, pain on full flexion, extension and palpation in the region of the anconeal process and the medial jointspace. In advanced cases crepitation and muscular atrophy can occur.

Lameness can increase to extreme degrees and is often resistant to conservative therapy.

Radiology:

Radiology plays an important, if not a key role, in the diagnosis of FCP and OCD. Different views of x-ray projections have been recommended in the past in order to diagnose the changes, but there is no doubt amongst all veterinarians that the pictures taken must be of excellent quality, since changes in the bone/joint structure can be sophisticated. Therefor the following standard techniques/projections are recommended: 1. extended medio-lateral ml; maybe some degree of supination), 2. flexed medio-lateral, 3. cranio-caudal (crcd), 4. a craniolateral-caudomedial oblique (crl-cdmo) and a 5. craniomedial-caudolateral-oblique (crm-cdlo) view.

OCD: Typical radiological changes of OCD can be found in the medial aspect of the distal humerus (trochlea humeri). They are best visible in the ml-flexed or the crcd and crl-cdmo projection and consist of a crescend shaped area of radiolucency at the trochlea humeri, sometimes including a sclerotic margin. In some cases ossified ossicles or free joint bodies occur. Secondary changes are similar to those in OCD

Picture 5: typical OCD-lesion of the trochlea humeri

FCP: The fragmented piece of cartilage and/or bone often lays on the lateral side of the medial coronoid process between the ulna and the radius. Therefore sometimes it is impossible to localise a loose fragment in the X-ray, no matter, how many different projections are available.

Sometimes fragments can be visualised in the Ml projections close to the anterior portion of the coronoid process or in the crcd-projections medial to it (possibly between radius and ulna).

In the majority of cases the diagnosis of FCP must be made on the basis of combined clinical symptoms and secondary (indirect) radiological signs

Amongst them are a step between radius and ulna (a shorter radius compared to the length of the ulna) or other signs of an irregular jointspace.

Furthermore arthrotic changes are important for an early diagnosis. First changes consist of sclerotic areas posterior to medial coronoid process or deformation of it, arthrotic changes at the dorsal part of the anconeal process and anterior to the head of the radius. Later on osteophytes in the area of the med. epicondyle and anterior notch of the trochlea occur.

Picture 6: dorsal view of the distal part of the elbowjoint with a typical fissure in the region of med. coronoid process

Therapy:

Basically in cases of OCD and/or FCP two different possibilities of medical treatment exist.

One is the conservative treatment: The dog receives non steroidal antiinflammatory drugs (NSAIDs), exercise is decreased and further examination 3-4 weeks later is recommended.

In some cases of OCD, with only small defects and no isolated jointbodies the complaints will disappear (occasionally very tiny pieces of cartilage can dissolve).

All others require early surgical treatment, before secondary arthrotic changes occur and the prognosis deteriorate.

Different approaches for surgery of OCD of the humeral trochlea and FCP, have been described, most of them being medial approaches. The common target amongst all is to remove the fragments of bone and/or cartilage and curette the defect in order to fill the defect with fibrocartilage.

Prevention:

The actual situation of FCP and OCD in breeds with genetic disposition for these diseases can be improved and manifestation can possibly be avoided in young growing dogs, if their surrounding conditions, like feeding, exercise and playing activities are changed or improved..

Once the puppies are three month of age, they must not be overfeed with proteins and minerals, (Protein app. 22-25%, no additional minerals (Ca++)), controlled exercise is of great importance as well. Controlled feeding will not lead to a smaller size, but the dogs will grow slower and they will be less susceptible for growth disturbances, which occur between the 3.-7. month, when fastest growing rates are present.

For early diagnosis it is important to perform a detailed examination in young dogs of affected breeds (first with about 4-5 month of age including clinical and radiological techniques). In case lameness exists without visible changes in the x-ray, continuos control of the dog's lameness is mandatory and all examination techniques should be repeated four weeks later (often secondary arthrotic changes have increased by this time and diagnosis is now possible).

The most important target is to prevent OCD/FCP by selection for breeding since both have proved to be a hereditary disease.

In 1989 a group of specialised veterinarians, like in hipdysplasia programs, from different countries formed a society in order to study the incidence of FCP/OCD and statistically analyse the disease in affected breeds (International elbow working group). Since numerous x-rays of different views are required to diagnose FCP/OCD, members of this group basically ask for one x-ray (flexed ml view) only, differentiating mainly some degrees of arthrosis (proceeding on the assumption that all different elbow diseases lead to the development of arthrosis). As a main condition for this examination dogs must be at least one year of age (similar to HD), in case lameness occurs earlier, the examination will be performed immediately.

The results of all these examinations should be open to the public and to all interested people (veterinarians, breeders, genetic scientists .a.f.m.) so that information about dames and sires are available before a partner for mating is selected.

Scandinavian countries, where these breeding programs operated for many years already, dogs with arthrosis are not automatically excluded from breeding, but the owners use the possibilities of the database to select healthy (unaffected) dogs for breeding. In consequence, the incidence of FCP and OCD and the severity of arthrosis was reduced already!

Sigrid Schleich

Chirurgische Veterinärklinik der

Justus-Liebig-Universität

Frankfurterstrasse 108

35292 Giessen