Osteochondritis dissecans

Osteochondritis dissecans
Specialty	Orthopedic surgery

Osteochondritis dissecans (typically abbreviated to OCD) is defined as "a [form] of osteochondritis in which articular cartilage and associated bone becomes partially or totally detached to form joint loose bodies."

Presentation

In osteochondritis dissecans, fragments of cartilage or bone have become loose within a joint, leading to pain and inflammation. These fragments are sometimes referred to as "joint mice" due to a squeaking sound sometimes resulting from the joint. Specifically, OCD is a type of osteochondrosis in which a lesion has formed within the cartilage layer itself, giving rise to secondary inflammation.

Patients with OCD complain of activity-related pain that develops gradually. Subjective complaints usually consist of mechanical symptoms, including pain, swelling, catching, locking, and "giving way; the primary presenting symptom may be a restriction in the range of movement.

Physical examination typically reveals an effusion, tenderness, and crepitus. The tenderness may be diffuse initially but often changes to well-defined focal tenderness as the lesion progresses. Acute osteochondral fracture has a similar presentation, but is usually associated with a fatty hemarthrosis. Although there is no significant pathologic gait or characteristic alignment abnormality associated with OCD, the patient may walk with the involved leg externally rotated in an attempt to avoid tibial spine impingement on the lateral(outer) aspect of the medial (inner) femoral condyle.

A special test known as the "Wilson sign" has been described to locate OCD lesions of the femoral condyle. The test is performed by slowly extending the knee from 90 degrees while maintaining internal rotation. Pain reported at 30 degrees of [[flexion] and relief with tibial external rotation is a positive result.

The possibility of microtrauma contributing to OCD underscores the importance of evaluating biomechanical forces at the knee during the physical examination. Extrinsic and intrinsic abnormalities of the joint, including join laxity and ligamentous laxity, should also be considered.

Pathophysiology

Osteochondritis dissecans (OCD) is a condition affecting the subchondral bone of joints with secondary effects on articular cartilage that results in pain, effusions, loose-body formation, and mechanical symptoms. Left untreated, OCD can lead to the development of degenerative arthritis secondary to joint incongruity and abnormal wear patterns.

OCD occurs when a loose piece of bone or cartilage partially (or fully) separates from the end of the bone, often because of a loss of blood supply (osteonecrosis) and insufficient amounts of calcium. The loose piece may stay in place or slide around making the joint stiff and unstable. OCD in humans most commonly affects the knees or ankles, but can also affect other joints such as the elbow.

Functional Anatomy

In skeletally immature individuals, the vascularity to the epiphyseal bone (growth plate) is very good, supporting both osteogenesis and chondrogenesis. With disruption of the epiphyseal plate vessels, varying degrees and depth of necrosis occur, resulting in a cessation of growth to both osteocytes and chondrocytes. In turn, this pattern leads to nonspecific changes that produce disordered intracartilaginous ossification, resulting in subchondral (below cartilage) avascular necrosis or OCD.

Four stages of OCD have been identified, including revascularization and formation of granulation (scar) tissue, absorb of necrotic fragments, intertrabecular osteoid deposition, and remodeling of new bone. With delay in the revascularization stage, an OCD lesion develops. OCD lesions may lead to articular-surface irregularities, which can cause degenerative arthritic changes.

Causes

Although the etiology is not certain, possible causative factors include repetitive microtrauma, ischemia, genetic and endocrine factors, and anomalies of ossification. Deficiencies and imbalances in the ratio of calcium to phosphorus within the body may also predispose joints to OCD problems as both elements are critical components of bone.

Interestingly, the incidence of overuse injuries in young athletes is on the rise and accounts for a significant number of visits to the primary care office; this reinforces the theory that OCD may be associated with increased participation in sports.

Diagnosis

To determine whether pains are osteochondritis dissecans, an MRI or X-Ray can be performed to show whether the loose piece of bone is still in place. In specific cases if caught early enough, a harmless dye will be injected into the blood stream to show where the calcium will most likely continue to build up. Doing this makes the removal process much easier.

Also see: Joint locking, Wilson test, and crepitus.

Treatment

Treatment options include modified activity with or without weight-bearing; immobilization; cryotherapy; anti-inflammatories; drilling of subchondral bone to improve vascularity; microfracture; reattachment and or removal of loose bodies and OATS procedure (osteochondral allograft transplant). OCD is commonly treated through a form of articular cartilage repair.

File:Treatment Algorithm OCD.gif

Fig. 1. A treatment algorithm for juvenile OCD lesions based on experiences from The Children's Hospital of Philadelphia. The patients are categorized into two broad categories: (1) asymptomatic or symptomatic with intact lesions, and (2) symptomatic with potentially detached lesions. Patients in the first category are managed non-operatively with immobilization, activity modification, and education. Routine plain radiographs are obtained to monitor progression. If progression occurs, or if patients are in the second category, then an MRI may be performed depending on the patients' symptoms to help determine the severity of the lesion. Intact lesions respond well to arthroscopic drilling, whereas detached lesions require more extensive surgical intervention.

Non-surgical Treatment

Candidates for non-operative treatment include those who are skeletally immature with an intact lesion and no loose bodies (Fig. 1).

Patients with OCD of the knee are immobilized for 4--6 weeks in a cylinder cast in extension to remove shear stress from the involved area. Patients with special considerations and concerns of skin breakdown may be treated in a knee immobilizer. Patients immobilized are permitted to ambulate with weightbearing as tolerated. If the plain radiographs taken three months after the start of non-operative therapy reveal that the lesion has healed, then a gradual return to activities is instituted. Patients with some component of healing demonstrated by increased radiodensity in the subchondral (below cartilage) region, or those patients whose lesions are unchanged, are candidates to repeat the above described three-month protocol until healing is noted.

Surgical Treatment

"The choice of surgical or non-surgical treatments for osteochondritis dissecans is... still controversial" according to some doctors. Nonetheless, surgery, such as fragment fixation, has proved effective in patients whose lesion thickness was "less than 9 mm." However, fixation by flexible wire or thread and revascularization by drilling for the fragment were "considered to be insufficient for large lesions with a thickness of 9 mm or more."

"Antegrade curettement, bone grafting and pinning of osteochondritis dissecans in the skeletally mature knee" is considered a reliable and generally successful surgery. However, the results of some studies tend to appear worse in those patients who "had more preoperative degenerative changes, a larger lesion, or a loose fragment. This suggests that intervention before these changes occur may improve results." Reconstruction of the articular surface with use of osteochondral plug grafts, autologous bone grafting and matrix-supported autologous chondrocyte transplantation (ACT) has also proved successful. "For large unstable lesions, fragment fixation or reconstruction of the articular surface leads to better results than simple excision."

Epidemiology

OCD is a relatively rare disorder. It commonly occurs in boys and young men from 10-20 years of age while they are still growing. As girls become more active in sports, it is becoming more common among them as well. Prevalence In knee, 30–60 cases per 100,000 population.

Veterinary aspects

In animals, OCD is considered a developmental and metabolic disorder related to cartilage growth and endochondral ossification. Osteochondritis itself signifies the disturbance of the usual growth process of cartilage, and OCD is the term used when this affects joint cartilage causing a fragment to become loose. OCD in animals is "well recognized but poorly understood".

According to Lowchens of Australia:

"Medium and large breeds are most commonly affected including the Rottweiler, Labrador Retriever, Golden Retriever, German Shepherd, Bernese Mountain Dog, Newfoundland, St. Bernard and Great Dane. OCD has also been reported in the cat. Joints commonly affected by OCD include the shoulder, elbow, stifle, and hock. Joints are often affected bilaterally."

The problem develops in puppyhood although often subclinically, and there may be pain or stiffness, discomfort on extension, or other compensating characteristics. Diagnosis is via scans such as X-ray, arthroscopy, or MRI, and treatment is often surgical although the best method remains open to debate.

Because an animal may compensate for painful forelegs by misuse of rear legs, there is a possibility that this condition can be masked by other skeletal and joint conditions such as hip dysplasia.

See also

• Osteochondrosis
• Osteochondropathy

References

• Kobluk, Calvin N. (1995), The Horse: diseases & clinical management vol. 2, W. B. Saunders, ISBN 0443087776 {{citation}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)

External links

• . GPnotebook https://www.gpnotebook.co.uk/simplepage.cfm?ID=-731185141. {{cite web}}: Missing or empty |title= (help)

Animal

• Fully detailed UPENN page on canine OCD
• Lowchen's resource and links page
• The Pet Center: OCD page