Osteochondritis Dissecans

Not the Same as Osteochondral Defects (OCD)

• Osteochondritis dissecans (OCD) may cause an osteochondral defect but is not the same.

Aetiology (Causes)

The causes are unknown, but three suggested theories are:

1. Hereditary:
   • Associations: Perthes disease, dwarfism, Stickler's disease, tibia vara.
2. Vascular:
   • Paucity of blood supply just adjacent to the posterior cruciate ligament (PCL) on the medial femoral condyle (MFC).
3. Traumatic:
   • Repetitive microtrauma from shear forces.

Clinical Presentation

• Mechanical symptoms:
  • Pain
  • Activity-related swelling
  • Catching
  • Locking

Imaging

1. X-ray:

   • Standing AP/Lateral and Skyline views.
   • Notch view (knee flexed 30 degrees) shows posterior condyles better.
   • Malalignment may be contributory, especially in adults.

2. MRI:

   • Gold standard for assessment.
   • Identifies or eliminates concurrent pathology.
   • Can assess stability, fragmentation, and lesion size.

Classification

1. By Age of Onset:

   • Juvenile: Open physis.
   • Adult: Closed physis.

2. By Location:

   • Typically on the lateral aspect of the medial femoral condyle (MFC).
   • May occur anywhere, but lateral condyle lesions are least common.
   • Lateral condyle lesions, if present, are associated with discoid meniscus or meniscectomy.

3. Cahill Classification:

   • Classifies lesions by lateral position in relation to Blumensaat’s line.

4. By Stability:

   • Type 1: Subchondral bone compression.
   • Type 2: Partially detached lesion.
   • Type 3: Fully detached lesion but still within the underlying crater.
   • Type 4: Loose body.

Prognostic Factors

Lesions with poorer outcomes include:

• Closed physis (older children).
• Atypical location.
• Large size (>2 cm).
• Unstable fragment.
• Subchondral sclerosis on X-ray (poor response to drilling).

Management

1. Non-Surgical:

   • Goal: Allow healing and prevent displacement of fragment.
   • Includes:
     • Activity modification
     • Analgesia (avoid NSAIDs)
     • ROM (Range of Motion) program
     • Restricted weight-bearing

2. Surgical:

   • Goals: Stabilize fragments, restore articular congruity.
   • Treatment may be arthroscopic or open, with the same principles.

   If Fragments Are Preservable:

   • Antegrade transchondral microfracture: If the chondral surface is intact, it promotes healing underneath.
   • Fixation of fragments + microfracture/compression grafting: Used if the lesion is reparable; bioabsorbable pins are commonly used.
     • This is the treatment of choice for most cases.

   If Fragments Are Not Preservable:

   • Autologous Chondrocyte Implantation (ACI).
   • Autologous chondral plug transplantation.
   • Allograft transplantation.
   • Mosaicplasty.
   • Microfracture.

   If Malalignment in Adults:

   • Osteotomy +/- any of the above treatments.
   • Hemiepiphysiodesis to correct alignment if the physis is still open and limb malaligned.