Osteochondrosis In The Dog
James Tomlinson, DVM, Diplomate American College of Veterinary Surgeons
There are four main joints that are affected with osteochondrosis in the dog. These are the shoulder, elbow, hock and the knee. Common features of affected dogs include being a young, rapidly growing large to giant breed with a higher incidence of males being affected than females. A significant radiographic incidence of bilateral involvement is also present, though not all dogs will show lameness bilaterally.
Osteochondritis Dissecans of the Humeral Head
Osteochondritis dissecans of the humeral head is the most common form of osteochondrosis recognized in the dog. It is characterized by a partially detached flap of cartilage located on the caudal aspect of the humeral head. Occasionally, the piece of cartilage is completely detached and is found in the caudal most aspect of the joint. Great Danes and Irish wolfhounds seem to have a high incidence of this lesion. Lameness usually is first noticed between 4 and 8 months of age. The dog is presented for a rather sudden onset of unilateral lameness, even though radiographically a lesion may be present in both shoulders. The lameness is generally a weight-bearing lameness best seen when the animal is walking. The swing phase of the gait is shortened and the head will be raised when the painful leg starts to bear weight. Depending on the duration of the lameness, atrophy of the scapular muscles may be evident. Pain is elicited during manipulation of the shoulder joint, especially on extension. The diagnosis is confirmed radiographically by seeing the typical radiolucent defect on the caudal aspect of the humeral head. Arthrography can be used to outline the defect and the cartilage flap. Detached flaps can ossify and thus become visible in the caudal aspect of the joint or in the bicipital tendon area.
Three forms of treatment for OCD of the shoulder have been used: rest, exercise, and surgery. Strict exercise restriction can be used if the radiographic lesion is small, a cartilage flap is not visible, and the lameness is of a short duration. The drawback to this form of treatment is that the animal may not improve and surgery will have to be done anyway, more arthritic changes may develop, and the problem of restricting a young, energetic large breed of dog for a prolonged period of time. The second form of therapy, exercise, is based on the idea that exercise will cause the flap to break off. Once the flap is detached, it will reabsorb and the pain will disappear. The problem with this treatment is that it will cause the animal pain until the flap breaks off, the flap may cause mechanical damage to the cartilage of the glenoid surface and cartilage breakdown products will cause synovitis and further cartilage destruction in the joint, leading to degenerative joint disease. In most cases, surgery is the best treatment for this problem. Surgery is recommend if the dog has been lame for 4-6 weeks, if the defect is large radiographically, or if a flap or joint mouse is present. Animals over 8 months of age are also considered surgical candidates. Always give the owner the option of surgery right from the start because of the predictable satisfying results of the surgery. Arthroscopic removal of the lesion is the preferred method of treatment if available.
Numerous surgical approaches to the shoulder joint for removal of OCD lesions have been recommended. The cranial lateral approach to the shoulder (Piermattei and Greeley 3nd ed, pp 98-101) followed by luxation of the humeral head gives tremendous exposure of the humeral head making the surgery very easy.
Exposure of the humeral head is gained by the following manipulation and it is the secret to the exposure. With one hand on the dog's shoulder and the other hand a little further distally on the limb, the elbow is held in extension as the shoulder is internally rotated and flexed by swinging the limb caudal and parallel to the dog's spine. While maintaining this position, continued internal rotation of the limb results in tearing of the joint capsule incision if it has not been cut far enough and luxation of the humeral head. Caudal retraction (Gelpi retractor) of the acromial belly of the deltoideus muscle will provide exposure of the lesion. The humeral head will usually maintain this position if the foot is far enough up over the spine. Once the lesion is identified, a scalpel is used to detach the cartilage flap. The edge of the cartilage should be trimmed so no abnormal cartilage is left. The cut through the cartilage should be perpendicular to the surface of the cartilage to insure good attachment of the new granulation tissue. The base of the lesion is curetted down to healthy bleeding bone. Excessive curettage should be avoided. The joint should be inspected for any loose cartilage and then irrigated with saline. Once removal of the loose cartilage fragments and curettage of the lesion is complete, the humeral head will reduce itself as the limb is externally rotated and brought down into a normal position. A standard closure of the joint capsule is performed along with reattachment of the infraspinatus tendon. Postoperatively, the dog should have very limited exercise for the first 2 weeks. Seroma formation is the most common postoperative problem and can be prevented by careful tissue closure and exercise restriction. At this point, the dog's exercise is slowly increased over the next month. Prognosis for return to normal activity is excellent.
Osteochondritis Dissecans of the Hock
The hock is the third most common joint in the dog affected with osteochondrosis. The incidence though, is considerably less than that seen in the shoulder or elbow. Rottweilers and Labrador retrievers seem to have the highest incidence of this problem but any of the large and giant breeds can be affected. Lameness starts around 5 to 7 months of age and is usually very apparent. Typically, the dog will have a decreased exercise tolerance. Affected dogs stand with their hocks very extended. Other clinical features of this disease are a shortened stride, muscle atrophy, joint effusion, and pain on manipulation of the joint. Radiographically, most dogs have bilateral lesions, though the dog may only appear lame in one leg.
The diagnosis is confirmed radiographically. At times, this lesion may be hard to recognize. A cranial-caudal, lateral, flexed lateral, and flexed caudal-cranial view may all be needed to reach a diagnosis. The radiographic signs include a radiolucent defect in the medial trochlear ridge of the talus, widening of the tibial tarsal joint space, presence of a joint mouse in the medial tibial tarsal joint space, DJD, and joint effusion.
Two modes of therapy have been recommended for this lesion, and some debate exists as to which method is best. Exercise restriction is one mode of therapy. Severe DJD and prolonged lameness may result, however. Surgery has been traditionally recommended as the treatment of choice. Surgical repair has not always produced favorable results, however. Generally, if surgery is selected as the method of treatment, it should be undertaken as soon as possible before arthritic changes become advanced. The lesion is exposed by a plantaromedial approach to the hock (JAAHA, 1990, vol 26, pp. 13-24). After the joint has been opened, the lesion will be seen as a cartilage flap located on the dorsal aspect of the medial condyle of the talus. A scalpel blade is used to detach the cartilage flap. The base of the lesion is not curetted. The joint is flushed and closed as described. A soft padded bandage is applied to the leg for 10-14 days and exercise restriction is enforced for 1 month. Prognosis is fair for most of these dogs. The severity of DJD will greatly affect the prognosis. It is not unusual for these dogs to occasionally be lame, especially during cold, damp weather and after strenuous exercise. Arthroscopic removal of the cartilage flap is possible in some dogs but is much more difficult than in other joints.
Osteochondritis Dissecans of the Stifle
This is probably the least commonly affected joint of the four that will be covered. The lesion can occur in any of the large or giant breeds of dogs, but especially occurs in the retrievers. Lameness will be noticed at 6-9 months of age and will vary from a mild to severe lameness. Muscle atrophy and poor conformation of the rear legs is often noticed. Joint effusion often can be palpated.
The lesion is diagnosed radiographically. Good quality craniocaudal and mediolateral views are usually diagnostic. Flexed mediolateral views are helpful at times to delineate small lesions. The lesion is most commonly found on the medial side of the lateral condyle of the femur, but it can also be found on the medial condyle. Radiographic signs include a radiolucent defect or flattening of one of the condyles, subchondral sclerosis, and DJD.
Early surgical treatment is indicated to remove the cartilage flap and decrease DJD. The lesion is approached by a standard lateral arthrotomy of the stifle as described by Piermattei and Greeley in An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat, 3rd ed., pages 276-277. After exposure of the lesion, a scalpel is used to remove the cartilage flap. Light curettage of the bed of the lesion is performed. Postoperatively, the leg is placed in a soft padded bandage for 10-14 days. Activity is sharply restricted for another 2 weeks, followed by gradual resumption of normal activity. Prognosis is variable and depends on the size of thelesion and the amount of DJD already present at the time of surgery. Arthroscopic removal of the cartilage flap is easily accomplished.
The elbow has three growth problems recognized clinically: ununited anconeal process of the ulna, fragmented medial coronoid process of the ulna, and osteochondritis dissecans of the medial condyle of the humerus. One or more of these lesions may be found in a single elbow joint, though usually only one is present at a time.
Ununited Anconeal Process
Ununited anconeal process was the first one of the three lesions discovered in the elbow joint and was originally called elbow dysplasia. It is now considered to be the second or third most common lesion in the elbow, depending on which source one reads. This condition is found in any of the large and giant breeds with German shepherds having the highest incidence. This problem is generally recognized between 6-9 months of age but some dogs are middle-age before clinical signs develop. Affected dogs are presented with variable degrees of lameness from a slight limp to being nonweight-bearing. The limb is usually kept slightly abducted and the elbow circumducts laterally during the swing phase of the gait. About 25% of the dogs will have bilateral involvement which may make the lameness not as apparent. Pain is present on flexion and extension of the joint. Joint capsule distension from joint effusion can generally be palpated in the area between the epicondyles of the humerus and the olecranon. Crepitus may also be present if DJD is present in the elbow.
A tentative diagnosis is made based on the signalment and clinical signs. The diagnosis is confirmed radiographically. A flexed lateral radiograph of the elbow is the best view from which to diagnosis this problem. In the young dog, the anconeus is first seen radiographically at 10-13 weeks age as it starts to ossify. In a normal German shepherd, the anconeus should be united with the rest of the ulna by 18-20 weeks of age. Radiographically, one will see a separation between the anconeus and the rest of the ulna. Variable amounts of DJD may also be present. The other feature of this disease is a stair step between the radial head and the coronoid process. The radial head is more proximal in location compared to the coronoid process than normal. This results in pressure being applied to the anconeus by the humeral condyle and is thought to contribute to the anconeus not fusing to the rest of the ulna.
Two modes of surgical intervention have been used to treat this problem; removal and reattachment of the anconeus. Both methods of treatment utilize the Caudal Lateral Approach to the Elbow as described by Piermattei and Greeley in An Atlas of the Surgical Approaches to the Bones of the Dog and Cat (3rd Ed, pages 150-153) to expose the ununited anconeus. In cases with severe DJD, removal of the anconeus is the desired treatment. The anconeus generally is attached to the rest of the ulna with fibrous tissue. To remove the anconeus, a scalpel blade is used to cut through this connecting tissue. A pair of towel forceps works well to grasp the anconeus and remove it from the joint. The anconeus may have an attachment to the medial joint capsule which will have to be cut once the anconeus is part way out of the joint.
A new method of encouraging the anconeus to fuse to the rest of the ulna involves performing a proximal ulnar osteotomy. In a significant number of cases, the anconeus will fuse to the rest of the ulna. Reattachment of the anconeus should be tried for young dogs that have minimal arthritic change in the joint. Reattachment of the anconeus by means of a lag screw technique to compress the bone edges together typically will fail because the screw breaks.
Postoperatively, the dog's leg is placed in a soft padded bandage for 14 days. Exercise restriction for 1 month is encouraged with a gradual increase to normal after this time. Prognosis is good for limb use after removal of the anconeus if minimal DJD is present. Some dogs will have a peculiar "wobble" of the elbow, however, if the anconeus is removed. Prognosis for dogs with reattachment of the anconeus is very good is done at a young age.
Fragmented Medial Coronoid Process of the Ulna andOsteochondritis Dissecans of the Medial Humeral Condyle
The comments made below generally apply to both fragmented medial coronoid process and OCD of the distal humerus. Though both lesions can occur simultaneously, generally only one is present. Fragmented medial coronoid process is the most common lesion in the elbow. Any of the large and giant breeds can be affected, but Labrador and Golden retrievers, Rottweilers, Newfoundlands, and German shepherds seem to have a higher incidence of the problem. In particular, the barrel-chested dogs seem to be more affected than the narrow chested dogs. Clinical signs show up at a little older age than for ununited anconeal process with most affected dogs showing signs around 8-10 months. Dogs may be up to 3 years of age before they show signs of lameness. The lameness is usually much more subtle than that seen with ununited anconeal process. The owner may describe a stiff gait that improves with mild exercise. The lameness will become more apparent after strenuous exercise. In that most of the lesions are bilateral, the lameness is not as noticeable because both legs are somewhat painful. Pain may be elicited by full flexion of the elbow and by deep palpation over the medial collateral ligament. Crepitus and joint effusion may be present if DJD is present.
The diagnosis is confirmed radiographically. Lateral, flexed lateral, cranial-caudal, and cranial-caudal oblique (10 degrees lateral to medial) radiographic views are taken. The OCD lesion is best seen on the oblique view. The OCD lesion is seen as a small half-circle defect on the medial aspect of the humeral condyle. The actual fragmented medial coronoid process is rarely visible on plain radiographs because of where the fragmented piece is located. The signs are non-specific and are mainly related to the DJD that develops in the joint. One of the first places that osteophytes are visible is along the dorsal aspect of the anconeus. One of the most reliable signs is seeing an osteophyte that develops on the medial side of the medial coronoid process and is best seen on the oblique view. As the problem becomes more chronic, osteophytes will be seen on the humeral epicondyles and radial head. Sclerosis of the trochlear notch area also will become evident.
There is some question as to the best method of treatment. Surgery is generally the treatment of choice for most dogs with either of these problems. The only reason not to recommend surgery is if the DJD is very severe. The surgery should be undertaken as soon as possible to prevent further DJD of the joint from developing. Arthroscopic removal of the lesion is the ideal method of treatment. For an open approach to the joint, the lesion is exposed by either a muscle separation approach or osteotomy approach as described by Piermattei and Greeley in An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat, (3rd Ed., pp 178-1181 or pp 182-185). Separation between the tendons of the pronator teres and flexor carpi radialis will allow adequate exposure of the joint. Once the medial side of the joint is exposed, the medial humeral condyle and coronoid process are inspected. If an OCD lesion is found, the cartilage flap is removed and the cartilage edges smoothed up with a scalpel blade. The base of the lesion is not curetted down to bleeding bone as is done in the shoulder. Most of the fragmented medial coronoid processes will have a fibrous attachment to the ulna but some will be completely free-floating. If the fragment is attached, a curette is used to detach the piece of cartilage. The base of the lesion is gently scraped to remove any remaining cartilage fragments. The joint is vigorously lavaged before closure of the joint. Postoperative care consists of 4 weeks of house confinement followed by 4 weeks of gradual increase in activity. The prognosis is dependent on the amount of DJD present at the time of surgery and is generally good if minor changes are present.