Introduction

Elbow dysplasias (ED) are recognized by veterinarians and breeders as a serious problem for certain populations. ED can be separated into different disease entities including ununited anconeal process (UAP), fragmented coronoid process (FCP), osteochondritis dissecans (OCD) of the medial humeral condyle and incongruities of the elbow joint (INC). Depending on the specific sub-population and the method of investigation, elbow dysplasia is seen in 46-50% of the Rottweilers, 36-70% of the Bernese Mountain Dogs, 12-14% of the Labradors, 20% of the Golden Retrievers, 30% of the Newfoundlanders, and 18-21% of the German Shepherds (1) but also in Great Danes, St Bernards, Irish Wolfhounds, Great Pyrenees, Bloodhounds, Bouviers, Chow chows and chondrodystrophic breeds (2,3). ED should be considered as different diseases, which may cause lameness and which may cause osteoarthrosis (OA). The clinical and radiological protocols for diagnosis of UAP, FCP and OCD will be discussed as well as surgical treatments. In addition, information on hereditary aspects and the work of the International Elbow Working Group will be given.

Clinical investigation

The clinical investigation starts with registration of the breed and age of the dog. From the above it is clear which breeds are at risk, like FCP (in Labradors, Bernese Mountain Dogs, Rottweilers, German Shepard's), OCD (in Retrievers and New Foundlanders), INC (in Bernese Mountain Dogs and chondrodystrophic breeds) and UAP (in German Shepard dogs, Bloodhounds, Bassets, St Bernards and Great Danes). The typical age of the patient suffering from ED is 4-10 months of age, although in increasing frequency dogs with elbow pain (without any signs of OA on radiographs!) are seen at >3 years of age. Inspection: almost 50% of the cases the paw of the affected leg is externally rotated and slightly abducted. Palpation: the elbow is effused. Passive movements of the elbow joint: the range of motion (ROM) of the elbow joint, crepitation, and pain is registered. In case of a UAP, there is in particular crepitation and pain sensation at a firm hyperextension of the elbow joint. In case of FCP and/or OCD, crepitation and pain reaction can be evoked at prolonged hyperextension, in particular when the radius and ulna are exorotated at the same time (i.e., supination).

Radiological examination

Diagnosis of ED can be confirmed by radiography. Bony union between the anconeal process and the olecranon should be complete at the age of 16-20 weeks (3). When a radiolucent area is present at an older age it is suggestive of an anconeal process which is not bony united, i.e., an UAP, due to a partial or complete separation in the cartilage between anconeal process and olecranon, preferable demonstrated on a mediolateral flexed (ML flexed) view. Sclerosis at the fracture site and osteophytes at the margins of the joint can be visible at a later stage.

OCD of the medial humeral condyle is best assessed on anterior posterior medial oblique (APMO) views, whereas on anteriorposterior (AP) views one third of the cases of OCD will be missed (4). Is a small amount of the cases a carcified flap can be seen located near the indentation of the contour of the medial condyle. In case of FCP, the fragment can only be seen on high quality films when the coronoid process is displaced cranially (as in Bernese Mountain Dogs), whereas the cranial alignment of the ulna at the level of the medial coronoid can give an indication of fragmentation. However, it can be in particular the secondary signs which help to confirm the clinical diagnosis. Osteophytes and sclerosis of the semilunar notch are taken into account for making the diagnosis. Small osteophytes are especially visible mediolateral views of the flexed elbow at the dorsal margin of the anconeal process. Extended views help to visualize also osteophytes at the radial head, and AP views demonstrate irregularities at the medial aspect of the humerus as well as the ulna.

Most entities of ED occur bilaterally in 30-70% of the cases, and therefore both elbow joints should be investigated, even in case of unilateral lameness. In case there are no radiographic abnormalities visibly in dogs with clinical lameness, and other causes of front leg lameness are excluded (including panosteitis, ocd in the shoulder joint, sesamoid fractures, and biceps tendon pain) auxiliary techniques including computed tomography, bone scintigraphy, and arthroscopy can be of value.

Therapy

1. Ununited anconeal process (UAP)

The ununited anconeal process can be removed, in case of sclerosis at the fracture line in the olecranon, or reattached in case of more acutely detached anconeal processes. When necessary, the other elbow can be operated immediately or, preferably after 6 weeks. Arthrosis formation will continue to develop but probably slower than when an irritating ununited anconeal process remains in place (9). Reattachment can be considered, in case of a partial separation of the anconeal process due to elbow incongruity. Than an osteotomy of the ulna (ulotomy) can be performed take away the bowstring effect.

2. FCP and/or OCD

The dog is positioned with the affected leg on the surgical table with the medial side of the elbow joint upwards and placed at the edge of the table, allowing exposition of the joint space between humerus and ulna to inspect the medial coronoid process caudal to the collateral ligament. Using a curved mosquito the medial humeral condyle is palpated: roughening is caused by a FCP (a "kissing lesion"), cartilage in unattached in case of OCD, and completely smooth surface makes the presence of FCP questionable. The cartilage flap is removed when present and the lesion curetted carefully. When the apex of the coronoid process is fractured, it is removed and the edges smoothened with a small curette. When the FCP is sandwiched between the ulna and the medial aspect of the radial head, the intact apex and the FCP are removed taking great care not to damage humeral condyle or radius cartilage. When fissures are present in the apex of the coronoid, the apex will also be removed. The joint is frequently flushed with saline to improve the surgical view and remove the debris. In follow up study, with a follow-up period ranging from 0.5-8 years (mean 2.7 years) the success rate was 78% in a group of 64 Retrievers (with 67.8% males) operated at young age. Only 33% of the conservatively treated dogs with a FCP (i.e., low body weight and controlled activity but no surgery), were not lame (13). This stresses the importance of an early diagnosis and surgical treatment. Results with arthroscopy are comparable, depending on availability of the equipment and the skills of the surgeon

3. INC with or without FCP

Elbow incongruity (INC) due to a short radius is frequently seen in Bernese Mountain Dogs (BMD), but also other breeds (Retrievers, Mastiff Napolitano) may be affected. An ad random study in the Dutch BMD population, revealed that 72% of the dogs had INC. A longitudinal study by Bienz (1985) demonstrated that this incongruity may normalize spontaneously and is most probably genetical. The joint surface supporting the humerus is decreased in case of a short radius. This leads to an increased pressure on the remaining joint surface, e.g., the lateral and medial coronoid process. Bernese Mountain Dogs with FCP or with INC were lame, but dogs with LCP ánd INC were all lame. In dogs with lameness due to FCP we remove the coronoid, in cases with lameness due to FCP and severe incongruity, congruity is restored first followed by removal of the FCP at the same surgical intervention. In dogs under one year of age INC surgery includes a partial (approx. 2 cm) ulnectomy as described above. In animals over one year of age, the restoration of elbow incongruity can be reached with the aid of the Ilizarov external ring fixator (IERF) after partial ulnectomy and/or loosening the musculature between radius and ulna, since the quadratus muscle is too rigid to allow for spontaneous correction.

The role of nutrition in ED

A combination of FCP and OCD has been explained by Olsson (1993) as a disturbance of endochondral ossification and as such expressions of the same disease. Osteochondrosis is seen more frequently in certain breeds and sub-populations and can be aggravated by high food intake and excessive calcium intake (17) as well as by oversupplementation of balanced food with vitamin D (Tryfonidou, 2002). In a study in Labradors it has been shown that OA in multiple joints (including hips, elbows and shoulders) was seen in overweight dogs and less frequently in slim littermates. The frequency and severity of the occurrence of osteochondrosis can thus be prevented by dietary management, including a food with a lowered calcium to energy ratio, a quantitative restriction of food intake, and without adding vitamin D to a balanced diet.

The role of neutraceuticals is yet under investigation. The supplementation with chondroitin sulphate, glucosamine glycans and other elements including manganese ascorbate may act as prophylactic protection against synovitis or to retard OA development when given at the right time, dosage and for duration. In a controlled study dogs treated with a mixture of chondroitin sulphate, glucosamine glycans and manganese ascorbate showed no significant response in terms of objectivated gait analysis after 60 days treatment (22). Omega 3 fatty acids may decrease the formation of leucotrins, mediators of joint inflammation, and thus optimize the healing process; an increased intake of omega 3 fatty acids at the expense of omega 6 fatty acids is therefore recommended, again for a sufficient long duration and at the right ratio (Hazrewinkel, 2000).

Management of ED affected populations

In some breeds a combination of UAP plus FCP, FCP plus OCD, or FCP plus INC is seen. The combination UAP plus FCP may be explained by the smaller diameter of the joint surfaces of the ulna (i.e., the ulnar trochlear notch) than of the humeral trochlea, forcing both bony protuberances from their origin (15).

The radiological findings included in a dendrogram of a Labrador population revealed that FCP and OCD occurred in two different groups of closely related dogs although in one related subgroup both entities were present (17). In a dendrogram of the Dutch Berneses Mountain Dog population it became clear that INC and FCP originate from two different groups of non-related ancestors but are now seen in 80% of the Bernese Mountain Dogs with ED. This indicates that there are different diseases (FCP, OCD, INC) which may occur in the same animal.

There is strong evidence that FCP in Retrievers is a inherited disease, either recessive autosomal or dominant with a variable expression; therefore dogs which are highly related to an affected animal can have a normal phenotype, the family history should be taken into account before including dogs in the breeding stock (18).

Although the scoring of arthrosis according to the guidelines of the IEWG can be performed on the MLflexed view alone, this underestimates the occurrence of the primary cause of elbow dysplasia with 12-25%, and the presence of arthrosis with approximately 12% (5,6). For screening elbow joints on the presence of a FCP a variety of views is advocated, including the AP, APMO, MLflexed, MLextended and the ML view with the joint extended plus the exorotation of radius-ulna 15 degrees (4). In a survey, we studied the value and additional value of each of the first four mentioned views, using the complete set of four views as a golden standard. We demonstrated that the MLflexed and the APMO views had a limited value as a sole view, but their great value as an additional view. False negatives of almost 20% when only a MLflexed view is used in a screening program for FCP, may explain the difference in percentage of positive Bernese Mountain Dogs between countries (5,6). Read et al. (1997) reported that 57% of a group of 55 Rottweilers in a prospective study developed radiographic signs of FCP but "only"15% showed physical signs including joint effusion, pain and crepitation during examination and 10% developed lameness (7).

The IEWG-protocol can be helpful for breeders to screen the elbow joints of their stock. Making the results of screening available to all breeders, a significant improvement in elbow status can be achieved as has been demonstrated to occur in Norway and Sweden in Bernese Mountain Dogs, Rottweilers, Labrador Retrievers and German Shepherds (3, 20). The differences in level of judging and thus of results warrants a certification which makes clear to breeders and buyers how a particular dog was screened. It is up to the veterinary community to come to these international appointments. The IEWG update (when applicable) is published on the web page: http://www.vetmed.ucdavis.edu/iewg/iewg.htm

References

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