BCCNSW

Elbow HD

 

Canine Elbow Dysplasia

This article was prepared by Dr R S Wyburn BVMS, DVR, PhD, FACVSc, MRCVS

Elbow dysplasia is a disease with a high inherited component, which primarily affects intermediate and large breed dogs. The incidence in Border Collies is low. Typically, both elbows are affected. However, unilateral elbow dysplasia is not uncommon.

DEVELOPMENT The elbow joint is formed by three bones (radius, ulna, and humerus) which must all grow synchronously and fit perfectly. The radius and ulna are paired bones with the radius being the main weight bearing bone. The normal elbow joint is characterized by a smooth transition from the ulnar articular surface to the radial surface. In a dysplastic elbow the edge of the ulnar surface lies above the level of the adjoining radius, creating a step between the radius and ulna and causing incongruity of the joint. The height of the step may vary from barely noticeable to 4 mm or more. When this occurs the weight bearing force on the ulna is increased, resulting in excessive pressure on the medial coronoid process. This leads to fragmentation of the coronoid process. The typical age for this to occur is between 5 and 7 months of age. A superficial to deeply grooved "kissing lesion" is often present on the humeral articular surface opposite the fragment. A cartilage flap or osteochondritis dissecans (OCD) lesion may also develop. Secondary arthritis becomes evident at 6-7 months. Compensatory adjustments during growth may occur in some dogs, tending to minimize unequal growth rates between the three bones and moving the ulna distally to better conform to the radius. . If the ulnar surface lies below the radial one, excessive force is then placed on the anconeal process at the top of the ulnar articular surface. This force will cause a failure of ossification, leading to an ununited anconeal process.

CLINICAL SIGNS

Affected dogs are frequently lame or have an abnormal gait. The gait is often characterized by excessive paddling or flipping of the front feet.

The animal may either hold the elbows out or tucked in and often stands with the feet rotated outward. Many sit or lie down much of the time, or play for shorter periods of time than other dogs of comparable age. They are often described as quiet or even lazy. Frequently, they are stiff when rising and tire easily. Exercise typically makes the lameness worse. In dogs with bilateral elbow dysphasia, the lameness may seem intermittent or shift from one front leg to the other. When both front legs hurt, dogs do not limp constantly. Rather, they shift weight off their elbows by altering their gait and stance. These dogs will only "limp" when one elbow is more painful than the other. On examination, manipulation of the elbow is often resisted. Swelling and crepitus (grating) may be palpated. The swelling may be worse after exercise. In some cases, the joint will be thickened. Muscle atrophy may also be present.

DIAGNOSIS

The routine monitoring for the presence of elbow dysplasia is carried out from a lateral x-ray of the flexed elbow joint taken when the dog is over 12 months of age. Correct radiographic technique is critical for making the diagnosis. The grade is derived by measuring the amount of new bone that has developed as a result of arthritis. Unlike the grading systems for hip dysplasia the system for elbow dysplasia is used internationally.

ADVICE

It is generally considered that dogs with grade 3 elbow dysplasia should not be used for breeding and that dogs with grade 2 should be considered a serious risk.

 

Reference: World Small Animal Veterinary Association web site

The information regarding OCD has been copied with permission from the NBCC website that was very kindly written by R S Wyburn BVMS, DVR, PhD, FACVSc, MRCVS.


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