Canine Elbow Dysplasia
Elbow dysplasia is the commonest cause of fore limb lameness in young large and giant breed dogs.
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. 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, and elbow dysplasia has little in common with hip dysplasia. Furthermore, the term elbow dysplasia intimates a discrete entity, when in fact there are many forms of developmental elbow diseases, which have very different causes and treatments.
How can I tell if my dog has elbow dysplasia?
Elbow dysplasia is the commonest cause of fore limb 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 exercise, although many dogs will exercise freely and limp afterwards. Although most dogs will be diagnosed before they are 2 years old, some dogs will not limp until they are older. Collectively, elbow dysplasia and elbow osteoarthritis are the commonest causes of fore limb 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 fore limb lameness that has not been caused by trauma.
What is the cause of elbow dysplasia?
This condition is primarily of genetic cause, although environmental factors such as obesity during puppyhood may influence whether an animal with the genes coding for elbow dysplasia will develop a clinical problem. Current estimates state that more than one hundred genes code for elbow dysplasia. Our ultimate goal will be to genetically map affected animals and tailor breeding programmes to minimise this disease.
Figure 1: This image shows the pattern of stress fracture radiating from part of the coronoid process of the ulna.
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.
What is happening inside an affected joint?
There are several different disease processes that are collectively termed elbow dysplasia. In most affected dogs, 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). Whilst standard radiographs are very helpful in diagnosis of this condition, CT and MRI scans can provide more specific information regarding “fit” of the bones and ultimately only arthroscopy (keyhole examination) can provide all the information regarding the joint surfaces which will allow efficacious treatment.
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, 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. In elbows in which this type of incongruity is permanent, treatment is usually by proximal ulnar osteotomy
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. Treatment of this problem may be undertaken by biceps ulnar release.
Pictures 3 and 4: effect of contraction of the biceps brachialis complex on the medial coronoid process.
Videos 4 and 5: Radio-ulnar conflict is evident in this first video and in the second one of the major factors influencing this, motion of the biceps brachialis muscle-tendon complex is illustrated
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 can include proximal ulnar osteotomy, sliding humeral osteotomy , unicompartmental elbow replacement , or total elbow replacement.
Videos 6 and 7: Ulnar notch incongruity
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 minimize the likelihood of osteoarthritis progression. Non-surgical treatments for elbow dysplasia aim to treat elbow pain, but do not have the potential to minimize osteoarthritis progression.
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, 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?
You will have noticed lameness or stiffness and your vet will have noticed elbow pain in your dog. We will perform a thorough examination to isolate pain to the elbow definitively.
If your 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. Sometimes 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 great bearing on ability to perceive pathology. At Fitzpatrick Referrals we have the most advanced direct digital radiography yielding crystal clear images to optimise diagnostic opportunity.
Pictures 5 and 6: These two images are appropriately positioned medio-lateral flexed images of the elbows of two young Labrador retrievers. The first image shows new bone formation and increased whiteness under the ulnar notch (known as sub-trochlear sclerosis, STS) and as such it s easy to see the osteoarthritis. In the second image however, there is only subtle STS and therefore medial coronoid disease could easily be missed in this dog.
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. CT gives us very useful information for planning the best treatment of elbow dysplasia in an individual. We offer CT to every dog owner when elbow dysplasia is suspected. The entire study can be completed in minutes and gives us a three dimensional picture of the disease process.
Pictures 7 and 8: These images represent sagittal and transverse planar images of fragmentation of the medial coronoid process clearly visible on a CT scan.
Pictures 9 and 10: These images represent sagittal and transverse planar images of fragmentation of the medial coronoid process from the Labrador Retriever for whom the second radiograph above was taken. It s clear that though the fissuring is impossible to see radiographically, its clearly evident on the CT scan images.
Pictures 11,12 and 13: This series of images also show radiography and CT scan from the same patient. Again it s clear to see that the radiograph simply shows STS whilst the CT scans show obvious fragmentation. It s important to realise that radiographs alone are sentinel for disease of the coronoid process and that other imaging modalities may be necessary for definitive diagnosis.
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. We will always couple diagnostic arthroscopy with keyhole surgical procedures in dogs requiring surgical treatment. In dogs requiring treatment of problems in both elbows, this is performed as part of a single surgical procedure. When surgery can be arthroscopically achieved, the patient is generally walking well the following day and recovery times are generally rapid.
Pictures 14, 15, 16 and 117: these pictures illustrate tip and radial incisure fragmentation of the medial coronoid process, which are the two most common kinds of fragmentation. The arthroscopy images are accompanied by schematic representations to illustrate the two patterns of the disease. It s important to realise that these two forms may require different treatment and at Fitzpatrick Referrals we have pioneered research designed to optimise the most appropriate treatment for each individual patient.
How is elbow dysplasia treated?
Non-surgical treatments for elbow dysplasia
Non-surgical treatments are sometimes recommended for dogs that are affected by subtle pathology, and in dogs having no evidence of current elbow incongruity or radio-ulnar conflict. The cornerstones of non-surgical treatment are body weight management, physiotherapy, exercise modification, and medication (anti-inflammatory pain killers). These same techniques are also important in the short-term management of dogs who are treated surgically, although the primary surgical aim is to minimize the requirement for long-term exercise restriction and medication.
At Fitzpatrick Referrals, we have fully qualified physiotherapists and hydrotherapists formulating protocols for treatment of all forms of joint disease, including those patients not surgically treated and for postoperative rehabilitation of surgical patients. The protocols are custom designed to optimise outcomes. Physiotherapy will not cure arthritis or on its own remove pain, but it can significantly help mobility and improve function for arthritic joints; and it can significantly improve outcomes achieved after surgery.
Recent additions to our therapeutic arsenal for non-surgical management include intra-articular injections of autogenous substances (from the patient s own body). In this regard, autologous conditioned plasma (ACP) may be helpful. Blood is taken from the patient and processed in a specific way to concentrate the blood platelets and growth factors in the plasma. When activated outside the bloodstream, the morphogenic proteins elaborated may help ameliorate clinical signs associated with osteoarthritis. Fat-derived stem cells may hold promise, but the joint is an organ and there are complex mechanical and biological processes occurring which may benefit from multiple treatment modalities. It is unlikely in the elbow joint that biologic treatments alone will address pain and lameness effectively and sustainably in the presence of significant alterations of joint mechanics.
Surgical treatments for elbow dysplasia
Arthroscopic fragment removal: In some cases, the problem at the time of diagnosis is confined to an isolated fragment of the coronoid process of the ulna. In dogs having fragment removal alone (a keyhole procedure), the CT scan and arthrosopy will have shown no evidence of current elbow incongruity or radio-ulnar conflict, and any remaining coronoid process will have been assessed as having a low risk for stress microfracture. The majority of dogs will make a rapid clinical improvement after arthroscopic fragment removal, and in some cases this improvement will be maintained in the long term. The long-term prognosis is dependent on the degree of osteoarthritis in the rest of the elbow joint and this is discussed on an individual basis.
Subtotal coronoid ostectomy (SCO): In elbows where there is diffuse stress fracturing of the coronoid process of the ulna, the majority of the process should be removed using keyhole technique. This surgery was developed at Fitzpatrick Referrals. In common with arthroscopic fragment removal, the majority of dogs will make a good clinical improvement after SCO and in many cases this improvement is maintained in the longer term. However, osteoarthritis is progressive for all forms of medial coronoid disease regardless of whether fragment removal alone or SCO is performed. In many cases however, this does not produce noticeable lameness.
Picture 18: In many cases, the fragment represents the tip of the iceberg. SCO is used to remove the part of the coronoid process of the ulna that is affected by microscopic stress fracturing. This procedure is a keyhole surgical technique, as shown in video 10
Proximal ulnar osteotomy (PUO): In some elbow joints, stress fracturing of the coronoid process of the ulna is caused by the presence of a relatively short radius, and this incongruity can be permanent. In these elbows the incongruity is corrected in order to treat the current elbow pain and also to attempt to limit the future progression of osteoarthritis. This is achieved by cutting the ulna below the elbow joint. Cutting the bone at this point does not prevent the limb from being used normally, and healing of the bone occurs in a new position that provides a more congruent elbow joint. The same technique may be employed to treat elbows affected by a poor fit between the humerus and the ulnar notch. Appropriate motion of the cut portion of the ulna and subsequent healing is facilitated by a specific angle of cut termed dynamic oblique. The specific nature of this technique was established by Fitzpatrick Referrals.
Picture 19 and video 10: This image and video represents the effect of a bi-oblique dynamic proximal ulnar osteotomy on the medial coronoid process
Biceps ulnar release (BURP): In some cases, we recognize a specific pattern of stress fracturing of the coronoid process of the ulna typical of radio-ulnar conflict. This conflict is contributed to by excessive and repetitive forces imparted by one of the branches of the biceps muscle which attaches on the coronoid process itself. Although the tendon itself is not diseased, it exerts force on a badly fitting bone geometry which contributes to the micro-fractures and ultimate fragmentation. Keyhole surgical release of this branch allows neutralization of these forces. The remaining biceps insertion on the radius is not affected, and because the biceps shares its function of flexing the elbow joint with another muscle (the brachialis), there is no deleterious mechanical consequence of biceps ulnar release. This procedure was also pioneered at Fitzpatrick Referrals.
Pictures 20 and 21: Biceps ulnar release involves sectioning of the part of the biceps tendon that is contributing to repetetive imaction of the radial head against the coronoid process of the ulna. This procedure can be performed arthroscopically as shown here.
Sliding humeral osteotomy (SHO): In some dogs with advanced elbow dysplasia, there is severe secondary osteoarthritis. A specific pattern of osteoarthritis in which cartilage is severely damaged or absent on the medial (inside) aspect of the joint but appears relatively healthy on the lateral (outside) aspect of the joint can be treated by SHO. This type of elbow pathology is known as medial compartment disease (MCD). SHO is an advanced procedure that is currently offered in only a few veterinary hospitals worldwide. It involves cutting the humerus (upper arm bone) and fixing it in a new position using a special stepped bone plate and screws. This transfers weight away from the diseased medial joint to the healthier lateral joint. In young dogs, there is the potential for some cartilage regeneration in the medial compartment after SHO. This isn t normal functional cartilage but serves as evidence of unloading and decrease of pain which is associated with friction between the humerus and the ulna (humero-ulnar conflict). SHO was refined by Noel Fitzpatrick based on the originally described technique of Dr Kurt Schulz and Mr Fitzpatrick has performed more of these procedures than anyone else in the world and has tutored training courses on this technique for other surgeons for the past four years.
Pictures 22, 23, 24, 25, 26: Sliding humeral osteotomy (SHO). A shift in the transfer of weight from the diseased medial part of the elbow to the unaffected lateral part of the elbow joint lessens elbow pain and improves function in most dogs treated in this way. The first image represents how the procedure is performed; the second shows radiographic healing at 6 weeks postoperatively; the third shows a typical elbow which may be treated in this fashion (with clearly evident full thickness cartilage erosion of the medial compartment); the fourth shows another elbow with no cartilage on the medial aspect of the distal humerus and the fifth image clearly shows fibrocartilage ingrowth several months later, demonstrating that the medial aspect of the joint has been unloaded and the patient is in considerably less pain.
Canine unicompartmental elbow replacement (CUE): CUE is an alternative to SHO in selected mature dogs suffering from medial compartment disease. This advanced surgical procedure involves the resurfacing of the weight-bearing portion of the medial (inside) of the elbow where cartilage is absent. Fitzpatrick Referrals is currently the only centre in Europe with experience in this technique.
Total elbow replacement (TER): In some dogs, elbow osteoarthritis can be extremely severe, with little or no healthy cartilage remaining. In these dogs, TER is used as a salvage procedure (i.e. it is performed as a last resort where other treatments will be ineffective). The entire elbow joint surface is replaced. Currently, we are one of the few practices in the UK able to provide this procedure routinely, and we offer a number of different types of elbow replacement prostheses, including custom prostheses. The image below is a radiograph of the Sirius Total Elbow System developed by Osteogen in collaboration with the University of Liverpool Vet School. The Sirius total elbow replacement is comprised of three components a stemmed humeral component, a radioulnar tray, and a ultra-high molecular weight polyethylene bearing. The Sirius elbow system uses special porus titanium surfaces and a coating called hydroxyapatite to help the implants integrate into the patient's bone providing a pain free elbow joint.