Introduction

Elbow dysplasia is common in growing dogs of several large breeds, and it leads to varying degrees of degenerative joint disease. Underlying causes of elbow dysplasia include ununited anconeal process (UAP), fragmented coronoid process (FCP) and osteochondritis dissecans (OCD) of the medial humeral condyle. Elbow dysplasia and its underlying cause are most often diagnosed when forelimb lameness is persistent and not controlled by antiinflammatory drugs; unfortunately, by this time, degenerative joint disease has already been established and surgical treatment will not be able to avoid its progression, providing only minimal benefits for the dog.

Early signs of joint pain in puppies are often overlooked, because of the hyperactive nature of the young animal and it is often bilateral so clinical signs are subtle. The first radiographic signs of elbow dysplasia are often missed, which delays the diagnosis. When a definitive diagnosis of elbow dysplasia is made, the surgeon can improve elbow function but cannot entirely prevent the progression of osteoarthritis (OA). Early diagnosis of elbow dysplasia is possible if a routine orthopaedic examination is carried out at 4-5 months of age in puppies of susceptible breeds (Bernese Mountain Dog, Labrador Retriever, Golden Retriever, Newfoundland, Rottweiler, German Shepherd Dog) or when the first signs of forelimb lameness or abnormal gait occur in any breed of dog. Early diagnosis of elbow dysplasia allows prompt surgical treatment, aimed at restoring joint congruity and preventing or reducing the progression of the disease and osteoarthrosis.

Early Evaluation of Elbow Dysplasia

An early orthopaedic evaluation should be done between the 15th and 20th week of life in canine breeds susceptible to elbow dysplasia; it can be planned at the time of vaccination. The goal is to detect the disease as early as possible. When no elbow dysplasia is detected, further evaluation at 6-7 months of age is advised because elbow disease can develop later on. When elbow dysplasia is detected, the disease is confirmed and proper countermeasures undertaken.

An early orthopaedic evaluation consists of clinical and radiographic examination of the elbows and of other joints susceptible to developmental abnormalities, using a breed-orientated approach. The puppy is observed while walking and standing to detect lameness or abnormal gait and posture. The radiographic examination of both elbows is carried out under mild sedation, using a film cassette in contact with the elbow. A mediolateral view is taken with the elbow held in a neutral position, at an angle of approximately 120 degrees. No traction is applied to the limb, and the paw is gently held with a sandbag on the table to achieve a true mediolateral view and to avoid pronation or supination of the limb. The X-ray beam is centered on the medial prominence of the humeral condyle. A second mediolateral view is taken with the elbow flexed approximately 45 degrees to assess the fusion of the anconeal process, if required. A craniocaudal view with the limb pronated 15 degrees, and fully extended, is also taken.

Early Diagnosis of Elbow Dysplasia

Ununited Anconeal Process

Early diagnosis of ununited anconeal process (UAP) is based on radiographic evidence of nonfusion of the anconeal process. This can be determined by comparing radiographs of the diseased and opposite elbows or, in cases with bilateral disease, comparing the radiographs with those of healthy puppies of the same age and breed. Incongruity caused by a longer radius can be assessed in both the neutral mediolateral and in the craniocaudal views. It is also possible to evaluate the mobility of the anconeal process, the degree of incongruity and to grade the disease by comparing the neutral and the flexed mediolateral views.

Fragmented Coronoid Process

An early diagnosis of fragmented coronoid process (FCP) is based on the first radiographic signs of overloading of the medial coronoid process (MCP), which are: subchondral sclerosis of the troclear notch; incongruity between the radius and ulna due to a shorter radius, seen in the neutral mediolateral and craniocaudal views; and a wider and uneven joint rim between the radial head and humeral condyle seen in the neutral mediolateral view. Abnormalities, however minor, must be seriously considered, because in most cases these lesions will worsen as the puppy grows. In the neutral mediolateral view of a normal elbow joint, the subchondral area of the trochlear notch has a regular trabecular pattern without any bone sclerosis. In addition, the joint rim between the radius and humeral condyle is thin and uneven. In the craniocaudal view, the radial joint profile is continuous with that of the medial coronoid process; there is no step.

Osteochondritis Dissecans

In early diagnosis of osteochondritis dissecans (OCD), the first radiographic signs are seen in the craniocaudal view. The distal profile of the medial condyle is flattened when the osteochondrosis has not caused detachment of a cartilaginous flap. When the flap is present, the subchondral bone shows areas of bone resorption and, later, bone sclerosis. In cases with OCD, joint incongruity can also be detected, as occurs in dogs with FCP.

Early Treatment of Elbow Dysplasia

Early treatment of elbow dysplasia is indicated when radiographs show that the disease process has started and further development of OA may be expected, based on observations from conservatively treated dogs with similar lesions.

Ununited Anconeal Process

Early treatment of UAP consists of dynamic ulnar osteotomy to release the pressure on the anconeal process. It is carried out proximally to restore full joint congruity. Screw fixation of the anconeal process in lag fashion is performed to enhance the chances of its bony fusion. When these procedures are done in 4-6-month-old puppies, restoration of joint congruity and fusion of the anconeal process are very likely. However, in older puppies, joint degeneration is already present and increased mobility of the anconeal process may prevent complete healing.

Fragmented Coronoid Process

In 4-6-month-old puppies with FCP that have joint incongruity, subchondral bone sclerosis of the subtrochlear notch with or without lameness and no osteophytes, treatment consists of distal dynamic ulnar ostectomy (DUO). This releases the pressure on the medial and lateral coronoid processes. The procedure is performed subperiosteally by removing 4-5 mm of ulna with a rongeur, bite by bite, approximately 2-4 cm proximal to the distal ulnar physis. The operated puppies are rechecked clinically and radiographically 3-4 weeks later to assess joint congruity and clinical signs. In cases with persistent clinical signs and worsening radiographic lesions with osteophyte formation, which indicates fragmenting of the coronoid process, conventional joint inspection and FCP treatment are carried out with arthroscopy or miniarthrotomy. In more advanced cases with more severe radiographic signs of OA that suggest fragmentation of the coronoid process, joint inspection and treatment with arthroscopy or with miniarthrotomy are performed in conjunction with distal ulnar ostectomy in puppies less than 8 months of age. After that age, thickening and hardening of the interosseous ligament between the radius and ulna inhibits the dynamic effect of distal ulnar ostectomy.

Osteochondritis Dissecans

Early treatment of OCD with radiographic signs of cartilage dissection consists of conventional OCD treatment with arthroscopy or miniarthrotomy (removal of loose cartilage and micropicking of the floor). In addition, distal dynamic ulnar ostectomy may be carried out after radiographic and intraoperative evaluation of joint incongruity. Because of the wide exposure of subchondral bone and continuous activation of inflammatory mediators, low-dose corticosteroids are given (prednisolone 0.2 mg/kg, orally q24h for 1-2 weeks) postoperatively in conjunction with low-dose non-steroidal antiinflammatory drugs (NSAIDs) (meloxicam 0.075 mg/kg, orally q24h for 3-4 weeks).

Discussion

In a number of puppies with radiographic signs of elbow dysplasia at 15-20 weeks of age, follow-up evaluation after conservative treatment revealed that OA continued to progress to a varying degree. In contrast, in puppies with the same early radiographic signs, treated very early with dynamic ulnar ostectomy, elbow dysplasia did not persist and there was no or very mild progression of OA. Early treatment of UAP with dynamic ulnar osteotomy has been widely demonstrated to be effective in restoring joint congruity and biomechanics. Early treatment of FCP is more controversial because it has been argued that initial joint incongruity could improve spontaneously during the remaining growth period, thereby eliminating the development of OA. However, in our experience, this occurs very rarely. Because of this and the low morbidity associated with distal ulnar ostectomy, we feel that it is a clinically relevant procedure that is justified for early treatment of FCP.

Distal ulnar ostectomy is well tolerated by patients and has no side effects when performed properly. This procedure entails a minimally invasive subperiosteal approach and the avoidance of injury to the radial periosteum and the interosseous vessels; damage may result in synostosis between the radius and ulna during the healing process. The efficacy of distal ulnar ostectomy to correct or improve joint incongruity caused by a short radius is proportional to the age of the puppy. In younger puppies, the interosseous ligament is more adaptable to sliding forces, which lower the ulna and raise the radial head so that there is better contact with the lateral condyle. In young growing puppies, the joint surfaces have moulding properties that allow them to adapt to one another when they are in intimate contact. Thus, if joint congruity is restored early enough, the joint surfaces of the radial head, ulnar trochlea and humeral condyle will match and adapt properly. These moulding properties are no longer present in older puppies; the interosseous ligament becomes stronger and osteophytes form on the borders of the radial head, which reduces or inhibits improvement in joint congruity after dynamic ulnar osteotomy. In older puppies with joint incongruity, proximal dynamic ulnar osteotomy can still improve joint congruity; however, the high morbidity and prolonged healing time should be carefully considered when deciding on treatment.

We found that the correlation of various findings, such as incongruity in the neutral mediolateral and craniocaudal views and subtrochlear bone sclerosis, was consistent in puppies with early signs of elbow dysplasia. In contrast, the evaluation of joint congruity alone in the flexed mediolateral view was inconsistent. Joint incongruity without signs of subchondral bone sclerosis is usually artefactual due to traction and positioning during radiography. Subtrochlear bone sclerosis is a consistent and direct sign of overloading of the corresponding joint surface, due to joint incongruity or malformation; it represents a very early and distinct sign of elbow dysplasia.

In conclusion, we found that early diagnosis and treatment of different elbow dysplastic conditions was useful for preventing or at least limiting the progression of OA.