Osteochondritis dissecans is a condition in which a segment of articular cartilage with its underlying subchondral bone gradually separates from the surrounding osteocartilaginous tissue.
The separation of the fragment may be partial or complete.
The osteochondral segment may remain in situ, it may become partially detached, or it may become completely detached and lodge in the contiguous joint as a loose body. It is important to differentiate the word dissecans from dessicans, the latter being derived from desiccare, “to dry up”.
The disease was first described in 1870 by Sir James Paget and the term osteochondritis dissecans was given in 1887 by Konig.
The name osteochondritis dissecans was given so as to describe the pathologic process that led to atraumatic loose bodies of femoral origin in the knee and hip joints as Konig believed it to be an inflammatory process [ osteochondritis] dissecans, [derived from the Latin word dissec].
However, the name is a misnomer as investigators have failed to identify inflammation on histologic examination. But the name has persisted.
Osteochondritis dissecans is characterized by separation of an osteochondral fragment from the articular surface of a bone with normal blood supply. This characteristic distinguishes it from osteonecrosis, in which the underlying bone is avascular.
Problem and Distribution
Osteochondritis dissecans affects two forms. Juvenile which affects children between age 5-15 years and adult form that affects adolescents with closed physes and adults.
The exact occurrence is not known but in the femoral condyles, osteochondritis dissecans has a prevalence of approximately 6 cases per 10,000 men and 3 cases per 10,000 women.
The disease affects knee in 75% of the cases, the elbow in 6%, and the ankle 4% of the cases.
Osteochondritis dissecans of knee affects medial femoral condyle 75% of the time. In the ankle, it affects the posteromedial aspect of the talus 56% of the time and in the anterolateral aspect 44% of the time.
Osteochondritis dissecans has a male-to-female ratio of 2-3 to 1.
The average age at presentation of juvenile osteochondritis knee is 11.3-13.4 years. In adults, this age is 17-36 years but can occur at any age. The average age at presentation of OCD in the ankle and elbow is 15-35 years and 12-21 years respectively.
Causes of Osteochondritis Dissecans
The exact cause of osteochondritis dissecans is not known yet. There are various theories that try to explain the causation. There appear multiple factors that decide this condition include trauma, ischemia and genetic factors.
The initial change takes place in the bone. A segment of the bone undergoes avascular necrosis. The changes in the overlying cartilage are secondary.
Initially, the cartilage overlying an area of dissecans appears to be normal, but with loss of subchondral bony support, it undergoes degenerative changes resulting in softening, fibrillation, fissuring of the cartilage. The cartilage loses its sheen also.
Local trauma can cause separation of the subchondral bony fragment.
Healing of the avascular bone occurs by revascularization and repair by creeping substitution. If healing does not occur, a dense fibrous tissue fills the gap.
The pathologic picture invokes both ischemic necrosis and trauma as factors in the pathogenesis of osteochondritis dissecans.
The source of the tissue that fills the defect is subchondral.
Once a lesion is present, it typically progresses through 4 stages unless appropriately treated.
A small area of compression of subchondral bone.
A partially detached osteochondral fragment. A radiograph of the bone may reveal a well-circumscribed area of sclerotic subchondral bone separated from the remainder of the epiphysis by a radiolucent line.
A completely detached fragment that remains within the underlying crater bed.
A completely detached fragment that is completely displaced from the crater bed. This is also termed a loose body.
Clinical Presentation Osteochondritis Dissecans
The usual presenting complaints are
- Intermittent pain in the joint on strenuous physical activity
- Clicking and locking of the joint
The symptoms vary with the stage of the lesion. Early knee lesions in the knee are associated with vague pain and swelling. The symptoms such as catching, locking, and giving-way occur as the lesion progresses. Intermittent symptom-free periods and exacerbation are common.
On examination, in osteochondritis dissecans of the knee, the affected leg may be externally rotated during walking. Quadriceps weakness may be noted. An important finding is localized tenderness over the lesional area.
Wilson test may elicit tenderness [see below]. The test is only valid for osteochondritis dissecans of the medial femoral condyle.
Atrophy of the controlling muscles, synovial thickening, hydrarthrosis, and limited joint motion are common findings. A loose body may be palpated.
Patients with osteochondritis dissecans of the ankle, complain of swelling and symptoms of catching with walking. Pain may not or may occur.
There is an intermittent pain on weight-bearing aggravated by strenuous physical activity such as running and sports. At times, the condition is asymptomatic. Localized tenderness which can be detected by markedly plantar-flexing the ankle joint and palpating the medial and lateral corners of the dome of the talus. Atrophy of the calf is common.
Ankle examination would reveal effusion, crepitus, and diffuse or localized tenderness. As the lesion progresses, the symptoms become more severe and localized. Limp is common.
In elbow, patients report an insidious onset of pain, swelling, and intermittent limitation of their range of motion. Athletes are particularly vulnerable to osteochondritis dissecans of the elbow. Joint effusion, crepitus, and generalized tenderness may be noted.
Wilson Sign in Osteochondritis Dissecans knee
With the patient in supine position, the affected knee is flexed to a right angle, the leg is medially rotated fully, and then the knee is gradually extended. At 30 degrees of flexion, the patient will complain of pain over the anterior aspect of the medial femoral condyle. The pain is relieved on lateral rotation of the leg.
The radiograph shows a well-circumscribed fragment of subchondral bone is demarcated from the surrounding affected bone by a radiolucent saucer or crescent-shaped line. The affected bone may appear denser than the surrounding parent bone.
As the fragment separates, a depression is seen at the site of separation. However, the detached loose body in the joint continues to grow to derive its nutrition from synovial fluid. Osteochondritic fragment becomes radiopaque is due to subchondral bone with articular cartilage, secondary calcification in degenerating articular cartilage and new bone formation following revascularization.
Special views may be necessary to visualize the lesion.
The CT scan makes possible a definitive diagnosis and determines the precise location and true extent of the lesion. It also reveals whether the fragment is detached completely or partially.
This shows localized increased activity at the site of the lesion. It helps to differentiate the lesion from infection.
Management of Osteochondritis Dissecans
During the early part of this century various modalities of treatment of osteochondritis dissecans were recommended like a simple observation, restriction of physical activity, non-weight-bearing protection, immobilization and surgeries like drilling, transfixing with pins, bone grafting, and removal of the partially or completely detached osteochondral fragment.
The advent of arthroscopic surgery has opened new vistas in the management of osteochondritis dissecans.
In osteochondritis dissecans of the knee, the age of the patient generally guides the treatment. Children who do not have loose bodies upon x-rays should initially be treated with a conservative treatment that includes limitation of activity and protected weight bearing for 3 months to allow healing and prevent further displacement for 3 months.
If the patient responds well, a full activity may be permitted once the pain subsides, the physical examination is normal and there is radiographic evidence of healing.
Patients who still have symptoms after 3 months, or fail to show improvement on serial x-rays considered for surgery.
In children who are approaching physeal closure, early surgery can be considered.
Adults may are less likely to improve without surgical intervention.
If a patient is asymptomatic, radiography every 4-6 months should be done until the lesion has healed or until skeletal maturity is achieved. If the patient remains asymptomatic at skeletal maturity and the radiographic findings have not progressed, no further treatment is indicated.
In osteochondritis dessicans of the ankle, lateral or medial lesions with normal radiographic findings or a partially detached osteochondral fragment may be treated by non-weight bearing immobilization for 6-12 weeks.
Medial lesion with a completely detached fragment on the x-ray that remains in the underlying crater bed may also be treated non operatively. A similar lateral lesion, however, would need surgery.
In the elbow, the treatment of severe lesions is surgical. In patients with mild-to-moderate disease, conservative therapy with immobilization may be considered.
For knee, surgery is indicated in children in whom symptoms have persisted for 6-12 months, lesions heal inadequately on conservative treatment, inadequate healing with conservative measures, skeletal maturity will occur within 6 months or
if loose bodies are present.
Earlier operative intervention is considered appropriate in an adult with knee OCD.
For ankle, surgery is indicated in all patients with ankle OCD who have lateral talar lesion fragments that are completely detached but remain within the underlying crater bed, symptomatic patients with medial stage III talar lesions require surgery. Loose body lesions (stage IV lesions) on both the medial and lateral side require surgical intervention.
In the elbow, progressive joint contracture, unresolved symptoms after conservative treatment, and fixed contracture of more than 10° with elbow pain are common indications for surgical intervention.
Finally, all patients with symptomatic lesions in whom conservative management fails should be offered surgery.
Asymptomatic patients with lesions in weight-bearing joints should be considered for surgery because these lesions may lead to early degenerative joint disease.
PatLesions less than 3 cm in diameter should be offered arthroscopic intervention whereas lesions>3 cm may be approached through an open procedure. Patients may also be offered autologous chondrocyte transplantation or mosaicplasty.
Patients with lesions 8 cm or greater in diameter may be offered radical removal of sclerotic bone with bone grafting of the defect and autologous chondrocyte transplantation (sandwich technique).
Arthroscopic Subchondral Drilling
Multiple perforations of the lesion are made using Kirschner wires.
Arthroscopic Debridement and Stabilization
A bioresorbable bone fixation nail (eg, SmartNail) tip is used on the arthroscopic handle and inserted into the top of the fragment. after fracture reduction. Multiple pins may be placed for greater fixation. Nonabsorbable screws like Herbert screws may be used in larger lesions with a firm crater. Cancellous bone grafting may be required.
Arthroscopic Excision, Curettage, and Drilling
The lesion may be arthroscopically excised and the crater debrided and drilled. This promotes vascularity and healing.
The base of the crater is drilled, the fragment is trimmed, replaced, and securely fixed with Kirschner wires which are removed later.
Fixation with bone pegs
Autogenous matchstick-sized strips of the corticocancellous bone graft are used for internal fixation of the lesion to the site of the defect. The cancellous bone graft is used to restore articular congruity.
Autologous Osteochondral Mosaicplasty
Cylindrical osteochondral grafts from the minimal weight-bearing periphery are arthroscopically removed and transplanted into prepared defects in the affected area. Combinations of the different graft sizes are used to allow a greater filling rate.
Autologous Chondrocyte Transplantation
Chondrocytes are arthroscopically harvested and cultured in a cell culture laboratory for 2-3 weeks. Cultured cells are injected into the defect, which is covered with a periosteal flap. This technique is required for extensive defects in which other treatments have failed.
Radical Removal of Sclerotic Bone, Bone Grafting and Autologous Chondrocyte Transplantation (Sandwich Technique)
The defect is excised to the normal surrounding cartilage, and the sclerotic bone is removed deep down to the bleeding cancellous bone. The osseous defect is filled with cancellous bone and secured with harvested periosteal flap. Autologous chondrocyte transplantation is performed and secured with another periosteal flap.
Following arthroscopic subchondral drilling the affected joint is immobilized until signs of healing are evident upon radiographic examination. Once signs of healing are evident, patients should perform range-of-motion exercises for 20 minutes, 3 times per day. A similar rehabilitation protocol should be used after fixation with bone pegs.
Following all other surgeries, immobilization is not necessary. Continuous passive motion is administered for 48 hours. Rehabilitation exercises are begun after 48 hours and are continued for 8 weeks. Weight-bearing is gradually introduced into and progressed to full weight bearing by 6-8 weeks.
Juvenile osteochondritis dissecans of a knee, without a loose body lesion, frequently heals with conservative methods. Similarly, ankle lesions in children seem to respond significantly better to conservative treatment than do their adults.
Adult ankle osteochondritis dissecans, respond better with when surgical intervention.
Arthroscopic subchondral drilling in patients with juvenile osteochondritis dissecans in the knee yields an approximate 80% success and in adults, approximately 70% success.
Arthroscopic drilling with fixation in patients with knee OCD yields good or excellent results in approximately 94% of patients.
Open removal of loose bodies, reconstruction of the crater base, and replacement with fixation yield a success rate of approximately 70%.
Fixation with bone pegs: Fixation with bone pegs have been reported to have 85-100% effectiveness.
Autologous chondrocyte implantation and mosaicplasty are still relatively new procedures. Their initial results are promising but however, further studies are needed.