Osteochondrosis (OC) / Osteochondritis dissecans (OCD) of the hock joint
What is OC?
OC is a developmental disease. It involves failure of normal development of the bone and cartilage of a joint surface during the first few months of life, resulting in an area of excessive thickening of the cartilage. This thickening causes the cartilage to become malnourished and susceptible to cracking, resulting in a loose flap of cartilage within the joint. When the cartilage flap starts to separate, the condition becomes known as osteochondritis dissecans (OCD). It can occur in any joint of the body, but most commonly affects the shoulder, elbow, knee and hock (ankle).
Why does the disease happen?
OC is a “multi-factorial” disease. Genetic factors are most important, with strong breed predispositions, particularly in Labradors and giant breed dogs. Different breeds appear to be predisposed to developing the condition in different joints. For example, the shoulder joint is most commonly affected in Border Collies, Great Danes and Irish Wolfhounds, while the hock is more commonly affected in Bull Terriers, Rottweilers and Labradors.
Various other factors such as dietary or nutrition problems, high growth rate or calorie intake over the first few months of life, hormonal imbalances and joint trauma can also increase the risk of developing OC.
Will my dog develop osteoarthritis?
As soon as OC starts to develop, osteoarthritis (inflammation of the joint and associated bones) immediately starts to develop. Once present, osteoarthritis cannot be cured, but in most patients, it can be effectively managed.
How do I know if my dog has OC?
Most dogs with OC/OCD start to show clinical signs before they are 1 year old, although occasionally (particularly with shoulder OC), they may present as older dogs. The clinical signs are variable, and depend on the joint affected and the size of the cartilage defect. The most common signs include lameness, stiffness, joint pain or swelling, reluctance to exercise or play, or general depression.
How is OC diagnosed?
OC is typically diagnosed by a combination of examination by an experienced orthopaedic surgeon, radiography of the affected joints, and arthroscopy (examination of the joint by keyhole surgery). Because OC can occur at the same time as other developmental orthopaedic diseases (such as certain manifestations of elbow dysplasia), some dogs may require additional tests such as CT or MRI.
How can OC be treated?
Various treatment options are available. The best treatment option for each dog is recommended following thorough clinical, radiographic, and arthroscopic assessment.
1. Non-surgical management
Non-surgical management may allow some improvement in lameness or pain in the short term, although it is seldom recommended for dogs with OC except where the risks of a general anaesthetic or surgery are considered excessive (e.g. severe heart disease, immune conditions).
Four basic methods are usually recommended:
- Body weight management
- Exercise modification
- Anti-inflammatory / pain relief medications
- Nutraceutical supplements (e.g. glucosamine, chondroitin sulphate, pentosan polysulphate, Green-lipped Mussel extract)
2. Surgical removal of cartilage flap / débridement
Surgical removal of the cartilage flap allows the resultant defect to heal by scar cartilage formation over the course of several weeks. Scar cartilage (fibrocartilage) is less robust than healthy joint (hyaline) cartilage, so although this allows some of the joint inflammation to resolve in the short-term, the joint will remain abnormal, with ongoing development of osteoarthritis and cartilage wear. We currently recommend this surgery for very small or shallow disease lesions. In general the disruption of surface topography caused by hock OCD lesions causes profound long-term debilitation if left untreated.
3. Osteochondral Autograft Transfer System (OATS)
Over recent years, we have adopted the OATS™ (Arthrex, Naples, FL) system for use in multiple joints. This system has been used for many years in human joints to resurface cartilage lesions including OCD, with positive long-term results. It involves collection of a cylinder of bone and cartilage from a non-contact area of a healthy joint (usually the knee) and transplanting it into a joint affected by OCD in order to resurface the cartilage defect with healthy hyaline cartilage. In some cases, it may be more appropriate to use a synthetic resurfacing graft instead of a cartilage graft and we have pioneered this technique successfully at Fitzpatrick Referrals.
4. Total Joint Replacement / Arthrodesis
Occasionally in some dogs with long-standing OCD or very extensive OCD lesions, osteoarthritis may be extremely severe with little remaining healthy cartilage. In this circumstance, the procedures above may be unable to restore comfortable, functional joint use. Total Joint Replacement is a “salvage” procedure (i.e. it is performed as a last resort where other treatments will be ineffective) and involves replacing the entire joint surface with metal and/or plastic implants. This can be done in the hip, elbow, shoulder, knee and hock joints. At Fitzpatrick Referrals we have pioneered total hock replacement and have had considerable success with application of this technique. An alternative is arthrodesis - surgical fusion of the bones on either side of a joint to prevent painful joint movement. We have been instrumental in the development of a new plate for hock arthrodesis and have circumvented many of the problems associated with previous repair techniques.
Occasionally after severe trauma, especially with loss of soft tissues around the hock joint, such as after a road traffic accident, external skeletal fixation (ESF) may be particularly useful. This allows stabilization of the broken and dislocated bones using pins connected with an external scaffold and allows appropriate treatment of the tissue loss. At Fitzpatrick Referrals, we have pioneered new kinds of ESF for this application.