Subchondral insufficiency fracture

Subchondral insufficiency fracture refers to a type of stress fracture that occurs below the chondral surface on a weight-bearing surface of a bone due to mechanic failure of subchondral cancellous bone.

Pathology

They tend to occur when normal physiological forces are repeatedly applied to an area of bone. Callus formation occurs along with non-mineralized osteoid and the absence of bone infarction.

Risk factors
  • osteoporosis
  • obesity
  • abnormal loading through the joint
  • overuse
Location

Typical sites include:

Complications
  • secondary osteonecrosis
  • osteonecrosis with cavitation (crescent sign)
  • articular collapse
  • destructive arthropathy

Radiographic features

Plain radiography and CT

Radiographs are normal preceding the development of callus formation or collapse of the articular surface. Linear or patchy subchondral sclerosis may be present representing cancellous fracture.

MRI
  • T1: may be characteristically low signal intensity band through the affected region
    • parallels the subchondral bone plate whereas osteonecrosis is curvilinear
    • preservation of the articular cartilage whereas an osteochondral defect is involved
  • T2: florid marrow edema

Differential diagnosis

The DDx of subchondral marrow edema includes:

See also