Elbow Dysplasia - Causes

Causes

The most common cause is osteochondrosis, which is a disease of the joint cartilage, and specifically Osteochondritis dissecans (OCD or OD), the separation of a flap of cartilage from the joint surface as a result of avascular necrosis, which in turn arises from failed blood flow in the subchondral bone. Other common causes of elbow dysplasia included ununited anconeal process (UAP) and fractured or ununited medial coronoid process (FCP or FMCP).

In OCD, the normal change of cartilage to bone in the development of the joint fails or is delayed. The cartilage continues to grow and may split or become necrotic. The cause is uncertain, but possibly includes genetics, trauma, and nutrition (including excessive calcium and decreased Vitamin C intake). OCD lesions are found in the elbow at the medial epicondyle of the humerus. Specific conditions related to OCD include fragmentation of the medial coronoid process of the ulna (FMCP) and an ununited anconeal process of the ulna (UAP). All types of OCD of the elbow are most typically found in large breed dogs, with symptoms starting between the ages of 4 to 8 months. Males are affected twice as often as females. The disease often affects both elbows (30 to 70 percent of the time), and symptoms include intermittent lameness, joint swelling, and external rotation and abduction of the paw. Osteoarthritis will develop later in most cases.

UAP is caused by a separation from the ulna of the ossification center of the anconeal process. FMCP is caused by a failure of the coronoid process to unite with the ulna. OCD of the medial epicondyle of the humerus is caused by disturbed endochondral fusion of the epiphysis of the medial epicondyle with the distal end of the humerus, which may in turn be caused by avulsion of the epiphysis.