Elbow Dysplasia

What is canine elbow dysplasia?

The word “dysplasia” means “abnormality of development”. The elbow is a complex joint because it involves the articulation of three bones. If the three bones do not fit together absolutely perfectly as a result of abnormal development, the consequence is abnormal concentration of forces on a specific region of the elbow joint.

Forms of primary cartilage disease may also constitute abnormal development of the elbow joint resulting in significant clinical consequences. The term ‘developmental elbow diseases’ may be a more descriptive nomenclature for this condition since most people will have heard of ‘dysplasia’ only in reference to the hip joint. Elbow dysplasia and hip dysplasia both mean that the conformation of the joint is abnormal. In hip dysplasia, the end result of the abnormality in all dogs will be osteoarthritisaccompanied by pain and reduced range of motion. Treatment mostly consists of management of the osteoarthritis or joint replacement. In elbow dysplasia, the forces concentrated on specific areas of the joint will not only result in osteoarthritis (as happens with hip dysplasia) but also in discrete pathological entities like fractures within the joint that may need to be managed separately and alongside the osteoarthritis.

Until recently it was believed that these disease entities were the manifestations of different elbow pathology but as they were commonly seen in combination with each other and they all resulted in elbow osteoarthritis, the term elbow dysplasia was used as an umbrella term for all of them. We now believe that these disease entities are the manifestation of the same pathology, which is the abnormal conformation of the joint and therefore we often see them in combination with each other. Although we still use the term elbow dysplasia to describe them, this term is now mostly used to describe the main pathology and not as an umbrella term for different joint disease entities.

How can I tell if my dog has elbow dysplasia?

Elbow dysplasia is the most common cause of forelimb lameness in young, large and giant breed dogs. Most dogs have a limp on one or both front legs. This can be seen as a nodding of the head when the good leg is placed and lifting of the head when the bad leg is placed. Some dogs that limp on both front legs will not have a limp, but will have an unusual “paddling” gait. Lameness is often triggered by prolonged rest and exercise. For this reason, many dogs will be lame when they wake up but after a warm up they will exercise freely and limp again afterwards. Although most dogs will be diagnosed before they are two years old, some dogs will not limp until they are older. Collectively, elbow dysplasia and elbow osteoarthritis are the commonest causes of forelimb lameness in dogs of any age. Small dogs can also be affected by elbow dysplasia and this problem should be suspected in any dog with forelimb lameness that has not been caused by trauma.

What is the cause of elbow dysplasia?

Picture 2: This is a microscopic image of a crack forming beneath the surface before it is visible at the surface. Fitzpatrick Referrals were responsible for the landmark research that showed that medial coronoid disease began in the bone beneath the surface and was not primarily a disease of cartilage.

Figure 1: This image shows the pattern of stress fracture radiating from part of the coronoid process of the ulna.

What is happening inside an affected joint?

In most dogs affected by elbow dysplasia, the pathology involves concentration of abnormal forces on a part of the joint called the coronoid process of the ulna. These abnormal forces cause microscopic stress fractures within this process, resulting in pain and lameness. In many dogs, either a small portion of the process or the entire process, will separate from the remaining bone. This problem is called fragmented coronoid process (FCP) and is one of the disease entities accompanying elbow dysplasia. Whilst standard radiographs are very helpful in diagnosis of this condition, CT can provide more specific information regarding the “fit” of the bones and regarding subtle bone pathology below the cartilage. Arthroscopy can provide additional information regarding the joint surfaces which, in combination with the findings from radiography and CT, will allow efficacious treatment. Investigation of the joint with radiographs and/or CT and subsequent arthroscopy is considered the standard of care at Fitzpatrick Referrals.

The pattern of abnormal development is not the same in all affected elbow joints. In order to offer the optimal treatment for a dog with elbow dysplasia, it is essential that we identify and neutralise the abnormal forces acting on the affected elbow. These forces are summarised below:

Elbow incongruity due to a relatively short radius:

Elbow incongruity can be transient or permanent. Subtle differences in the growth rate of the two bones that make up the forearm (the radius and ulna) can cause severe overloading of the prominent coronoid process of the ulna. In some dogs, it may be that this incongruity has resolved by the time the diagnosis of elbow dysplasia is made, but the consequence of this transient incongruity is stress fracturing of the coronoid process. Treatment of this problem is usually by arthroscopic fragment removal or subtotal coronoid ostectomy. With the latter, not only do we remove the fragmented coronoid process but also some of the unfragmented part which could still contribute to joint pathology due to its abnormal conformation and ongoing inflammation. In elbows, in which this type of incongruity is permanent, treatment is usually accompanied by proximal ulnar osteotomy in an effort to allow the longer bone (ulna) to find a more “convenient” place in the joint.

Short radius syndrome.

Coronoid process overloading due to conflict with the radius:

In some affected elbow joints, stress fractures of the coronoid process of the ulna could be the consequence of repetitive impact from the adjacent radial head. The anatomical structure with most contribution to this repetitive impact is a branch of the biceps tendon. This could be because every time the biceps muscle contracts it causes the radius to impact the ulna around an area known as radial incisure of the ulna (incisuar radialis ulnae). Treatment of this problem may be undertaken by a surgical procedure called ‘biceps ulnar release

Ulnar notch incongruity

In some cases, the notch of the ulna is excessively elliptical or simply the wrong shape relative to the humerus, resulting in severe overload of the extremities of the notch. In some dogs, this can cause severe cartilage erosion. When this happens, treatment options depend on the disease entities accompanying the developmental disorder and the extent of osteoarthritis present.

What is the long-term consequence of elbow dysplasia?

Every dog with elbow dysplasia is affected by some degree of elbow osteoarthritis at the time of diagnosis. This can be the consequence of a loose fragment acting like a “stone in a shoe” within the joint or of untreated elbow incongruity such as radio-ulnar or humero-ulnar conflict.

Surgical treatments for elbow dysplasia aim to treat the current source of pain and also to minimise the likelihood of osteoarthritis progression. Non-surgical treatments for elbow dysplasia aim to treat elbow pain and maintain mobility but do not have the potential to minimise osteoarthritis progression. Rehabilitation of elbow dysplasia can be provided through our rehabilitation service whereby one of our chartered physiotherapists will design a home care physiotherapy and exercise plan for you to follow at home between outpatient physiotherapy and hydrotherapyappointments.

The clinical impact of elbow osteoarthritis is unpredictable and, regardless of treatment, arthritis will progress to some extent for all affected joints. In some dogs, lameness can be mild and intermittent, whilst in others, lameness can cause severe and permanent disability. Where persistent cartilage erosion occurs, it is generally in the inner (medial) part of the elbow, constituting the joint between the humerus and the ulna (coronoid process). This could be the result of any form of elbow incongruity, such as a short radius, an abnormally shaped ulnar notch or just abnormal three-dimensional rotation conflict. In these situations, depending on the degree of poor fit, surgical treatment could include proximal ulnar osteotomy, sliding humeral osteotomy, canine unicompartmental replacement or total elbow replacement.

How is elbow dysplasia diagnosed?

Clinical examination:

At home, you will have noticed lameness or stiffness and your primary care vet will have noticed elbow pain in your dog. During your consultation at Fitzpatrick Referrals, one of our orthopaedic clinicians will perform a thorough, clinical examination to isolate definitive pain to the elbow and will discuss further investigation requirements and possible surgical intervention options should they be indicated.

Radiography:

If your primary care vet had a suspicion of elbow dysplasia, they may have obtained radiographs of the elbow joints. Radiographs will usually show changes in affected dogs although this is not always the case. At times, changes can be very subtle and difficult to detect and therefore the position in which the elbow is placed and the type of radiograph taken will have a great bearing on the ability to perceive pathology. At Fitzpatrick Referrals, our advanced diagnostic imaging service has the most advanced direct digital radiography yielding crystal clear images to optimise diagnostic opportunity including more advanced imaging techniques such as CT and MRI.

Computed tomography (CT):

In addition to radiography, we use computed tomography (CT) and arthroscopy to facilitate diagnosis of elbow dysplasia. CT can be performed under sedation or general anaesthesia. It is a very sensitive method for the diagnosis of stress fracturing of the coronoid process of the ulna and for the assessment of elbow incongruity and the bone underneath the cartilage. CT gives us very useful information for planning the best treatment of elbow dysplasia in your dog. We offer CT to most cases when elbow dysplasia is suspected. The entire study can be completed in minutes and gives us a three-dimensional picture of the disease process.

Elbow arthroscopy:

Arthroscopy is the gold standard technique for diagnosis of problems within a joint. It is a keyhole surgical technique that is performed under general anaesthesia. Arthroscopy allows us to obtain a magnified panoramic view of the inside of a joint. In dogs requiring treatment of problems in both elbows, arthroscopy and surgery are performed as part of a single surgical procedure under the same general anaesthetic. When resolution of the problem can be arthroscopically achieved, your dog will generally be walking well the following day and recovery times are usually rapid.