Elbow Arthroplasty - Osteolysis
Osteolysis was originally described in 1976 by Harris et all  about the femoral stem 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 polyethylene debris . 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 . 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, prosthesis subsidence and loosening. Osteolysis may occur adjacent to the humeral and ulnar components. Large amounts of particulate may dissolve in joint fluid, staining the fluid and synovium a dark metallic color. This is called metallosis.
| Osteolysis (red arrow) about the ulnar stem with progressive lucency. Follow-up study demonstrates migration of the ulnar stem, a finding diagnostic for loosening.|
|Severe ostelysis about ulnar stem with cement fragmentation (blue arrow) and interface widening. The findings are consistent with loosening. The ulnar cortex is markedly thinned anteriorly (red arrows), placing patient at high risk for pathologic fracture.|
|Osteolysis high power. Methylmethacralate 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.|
|Synovial fluid aspirated from joint, demonstrating greyish color related to metallosis.|