I have a 50 year old patient with a partial knee replacement done in 2011. She is recently having problems with swelling and erythema with a sanguinous effusion. Synovial fluid with positive polyethylene particles.  Are these microscopic particles released secondary to "rubbing inside." Is there anyway to test for this? Can we patch test with a piece of the hardware?


Thank you for your inquiry.

The components of knee replacements may be metal, polyethylene glycol, and cement such as methylmethacrylate. The presence of polyethylene in an effusion indicates osteonecrosis and an inflammatory reaction related to the implant with accompanying degeneration of the polyethylene component of the implant. There are many possible causes of this finding, one of which could conceivably be an allergic reaction to a component of the replacement itself.

The components most commonly implicated are the cements or the metals employed. I could not find any report of an allergic reaction to the polyethylene glycol, and characteristically, polyethylene glycol is not a sensitizer in this regard. The appearance of polyethylene glycol, as mentioned, is a marker for degeneration of the implant and osteonecrosis (1, 2), but not necessarily a reaction to the polyethylene glycol which would not normally produce a delayed hypersensitivity response (3).

You can test to the metal as well as the cement components via patch testing, and there is also an in vitro test known as MELISA that looks at lymphocyte transformation to metals used in implants. The difficulty, however, lies in the interpretation of the information gathered (4). To help you understand this, I would suggest your reading through Reference Number 4 below which is available to you free of charge via the link above the reference.

In order to patch test, of course, you would need to know the metals and cements used in the implant. On occasion, the manufacturer has a patch test kit containing these substances which you can request. If not, this type of material for patch testing can be ordered from Dormer. For your convenience, here is the link to Dormer as well as to the laboratory performing the MELISA, should you wish to pursue the testing. However, again, there is the strong caveat that the clinical significance of a positive test (or a negative test for that matter) has not been well clarified.

Finally, we have responded to a number of inquiries submitted to the Academy "Ask the Expert" website regarding allergic reactions to implants. Our responses to these inquiries might also be of help to you. They can be accessed by clicking here and typing "metal allergy" or "implant" into the search box.

Thank you again for your inquiry and we hope this response is helpful to you.

1) Periprosthetic bone loss in total hip arthroplasty. Polyethylene wear debris and the concept of the effective joint space The Journal of Bone & Joint Surgery, Volume 74, Issue 6

2) The Role of Access of Joint Fluid to Bone in Periarticular Osteolysis: A Report of Four Cases JBJS Case Connector, Volume 79, Issue 3

3) Skin Sensitization Potential of Polyethylene Glycols Evaluated in the Guinea Pig Maximization Test and the Human Repeat Insult Patch Test
1998, Vol. 17, No. 1 , Pages 81-88 (doi:10.3109/15569529809049304)
Hon-Wing Leung and Bryan Ballantyne

4) Skin Patch Testing and Associated Total Knee Outcomes William M. Mihalko, MD; Stuart B. Goodman, MD; Nadim J. Hallab, PhD; and Joshua J. Jacobs, MD

Phil Lieberman, M.D.

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