Osteolysis

Osteolysis was originally described in 1976 by Harris et al10 about the femoral stern of hip arthroplasties. They described focal endosteal scalloping and periprosthetic bone erosion. This term, also known as particle disease and aggressive granulomatosis, now refers to both focal and linear periprosthetic bone loss adjacent to any joint replacement.

Osteolysis results from a foreign-body response to particulate debris from the wear of arthroplasty components and cement. The most common inciter is polyethelene debris.11 Large particles are sequestered in fibrous tissue, but small particles are taken up by macrophages and multinucleated giant cells which may release cytokines that initiate a cascade reaction ultimately resulting in osteolysis.12 Osteolysis is usually asymptomatic. Follow-up radiographs are used to identify the process early on, before progressive, catastrophic bone loss occurs.

Radiographs demonstrate focal areas of lytic bone. Large areas can occur, but do not necessarily indicate prosthesis loosening. Thinned cortex and weakened bone places patients at risk of pathologic fracture, prothesis subsidence and loosening. Osteolysis occurs adjacent to tibial, femoral or patellar components. Large amounts of particulate may dissolve in joint fluid, staining the fluid and synovium a blackish color. This is termed metallosis.

AP and lateral radiographs demonstrating focal area of osteolysis (arrows) involving the posteromedial femoral condyle. Note dense knee effusion (arrowheads) related to particulate debris and metallosis.



Osteolysis proximal tibia complicated by pathologic fracture.



Axial CT of distal femur demonstrating osteolysis (arrow) of posterior femoral condyle.
Images obtained more proximally and filmed in bone and soft-tissue windows demonstrate metallic, bone and cement debris in the suprapatellar bursa.



Osteolysis high power. Mthylmethacralate debris (arrows) surrounded by giant cells (arrowheads).


Osteolysis high power polarized microscopy. Polyethylene flakes (arrow) surrounded by foreign body giant cell reaction (arrowhead).


Osteolysis low power. Polyethylene flakes (arrows) surrounded by foreign body giant cell reaction and histiocytes.

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