One of the more common diseases found in juvenile dogs is known as osteochondrosis/osteochondritis dissecans (OCD) and is thought to occur as a result of a “hiccup” in normal endochondral ossification. Endochondral ossification is the process by which growth plates contribute to longitudinal growth of a bone and is gradually replaced by bone.
Disruption of this process may cause a separation between cartilage and underlying bone. As the young animal becomes more active, this separation in the cartilage may form and a flap of thickened cartilage can break free from the underlying bone and can be “free-floating” within the joint. The formation of this flap is known as osteochondritis dissecans. This flap causes pain and inflammation as well as initiating arthritis within the joint. This disease can be diagnosed in the shoulder, elbow, knee and ankle joints and in many cases, the disease can be found in the joints on both sides of the body (bilateral).
The Diagnosis of OCD
The onset of this problem is generally between 5-10 months of age. Clinical signs include mild to severe forelimb lameness that worsens with exercise. Clinical findings such as pain in a joint are usually evident. Radiographs (X-rays) reveal a characteristic flattening of the bone as well as subchondral sclerosis (hardening of the bone under the cartilage. CT is sometimes utilized to confirm the problem.
Treatment of OCD
Before the advent of arthroscopy (tiny cameras inserted into a joint), OCD lesions were typically addressed via an open arthrotomy (a large incision into the joint capsule). With use of arthroscopy, OCD lesions can be confirmed through the use of these tiny cameras inside the joint. Once confirmed, treatment can also be performed through arthroscopy. Several arthroscopic techniques are employed:
- As a first step, the cartilage flap is removed from the joint using arthroscopic graspers.
- Any remaining diseased cartilage can be removed with arthroscopic curettes (instruments that look like small spoons).
- Straight-walling of articular cartilage provides a clean healthy surface in which to start the healing process
- Underlying bone can be debrided (tissue removed) by an arthroscopic shaver until good blood supply is appreciated.
- In some cases, microfracture technique may be performed. Utilizing this technique pokes little holes into the underlying bone and improves access to a good blood supply.
The presence of a good blood supply will ensure that the OCD defect and tissue bed fills with blood. This encourages the formation of fibrocartilage (scar-cartilage). Fibrocartilage acts like a band-aid at the OCD site and improves the patient’s pain and mobility.
New techniques may aid in improving the outcomes in certain joints. Osteochondral autografting or a synthetic osteochondral cartilage plug can be utilized to treat this problem. Osteochondral autografting involves harvesting a donor cartilage plug from a non-weight bearing portion of the patient’s own knee. This cartilage plug is then placed into an OCD lesion that has been prepared to receive this plug. Following surgery, this donor plug is incorporated into the recipient site and surrounding bone. The synthetic osteochondral cartilage plug is placed in a similar manner, but utilizes an implant rather than the patient’s own tissue.
Outcomes
Overall, prognosis varies greatly with OCD based on its location. Prognosis is generally considered good to excellent for the shoulder, fair to good for the elbow and knee and guarded to poor in the ankle. The clinical outcomes in dogs that have received plugs as intervention have been encouraging and may improve the overall prognosis for OCD in the knee compared to its traditionally fair prognosis.