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How to Interpret Your Test Results for the DePuy ASR Hip Implant

January 17, 2011

If your doctor recommended that you test for heavy metals, you may be confused by the jargon on your test results. We help you break it down so you understand what's going on.

Intraoperative Findings -  Things you may see in the surgeon's operative report


Metallosis - gray-tinged tissues indicating the presence of tiny metal particles accumulating in the area

Fluid

  • Yellow ("serous") - normal, physiologic and only usually a small amount
  • Blood-tinged ("sero-sanguinous") - usually indicating a loosened or non-ingrown component causing trauma to the local bone and thus bleeding
  • Thick, cloudy, milky - has the appearance of purulence (infection, pus) and can be mistaken for infection - but has now been shown to be a finding in hips with adverse reactions to metal-on-metal bearing surfaces
  • Also, please note that fluid from failed meta-on-metal replacements seems to be toxic to human tissue cells and could conceivably cause damage or unusual-appearing tissues in this way

Outside the joint itself

  • Thickened, friable (crumbly) extra tissue in the area around the hip - most likely related to fluid emanation from the joint and resultant thick-walled cyst-like formation by the body to contain it or maybe from changes in the tissues related to chronic inflammatory fluid in the area
  • 'Bursitis" - thickening of the bursa (normal fluid filled sac-area) over the trochanteric hip prominence - produces local swelling
  • Removal of the above tissue and bursa may or may not be necessary (no one knows), but seems to be performed in order to ensure that abnormal tissues are removed - this cause bleeding and trauma to the area

Tissue inside the joint

  • Failure of previous repair - tissue damage can breakdown the previous repair of the joint capsule (envelope) that was performed after the original THA. This also means that the soft-tissue envelope of the hip may not be repairable after this surgery because it's essentially gone. Although no one has really proven it, the worry is that this may lead to an increase in the dislocation rate after the revision
  • "Pseudo-tumor" - thickening of the joint lining (synovium) that makes it look like cancer or tumors in the joint. This is chronic inflammation in the joint itself related to the metal wear particles (see microscopic section below). This is a space-occupying lesion and can produce significant pain, swelling, and the typical mechanical symptoms (popping, catching) that a patient may describe, because it "gets in the way" when the patient moves their hip. Prevailing thought is that its expansion in the joint may lead to an increased dislocation rate after surgery because of the now-patulous nature of the joint lining. Also, its removal can generate significant bleeding. Finally, its removal may affect the ability to close the joint and therefore in itself increase the risk of dislocation postoperatively. No grading system exists for scoring the severity or prominence of pseudotumor. Its presence mereley means that there is chronic metal-on-metal problem.
  • Osteolysis - (loss of bone) - most-likely related to the inflammation in the joint invading the bone as a well and breaking down the bone. The patient's body is eating up the metal wear particles and then at the same time eats away the bone in a non-selective fashion (this was a big problem with plastics and why we went to metal-on-metal in the first place).
    • Osteolysis can be present in the tissues surrounding the socket, which can cause loosening of the socket itself. Osteolysis around the socket may make the revision more difficult as there is less dependable bone to work with and base the new socket placement on. This may have consequences for the future placement of another socket years later, as probably more bone will be lost as the new plastic liner wears out with use.
    • Osteolysis can also be present around the femur and, if severe, could cause fracture of the trochanter at the top of the femur, which is a devastating problem for the patient and tough to manage. In a less likely scenario, the amount of bone loss at the femur could be severe enough to loosen the femoral component
    • A grading system for osteolysis does exist and is based on xrays, but is probably not useful, as typically the osteolysis associated with the metal-on-metal problem doesn't get so severe. A surgeon may use terms such as "radiolucencies in zones 1,2 or 3 of the acetabulum" or "radiolucencies in zone 1 and 7 of the femur", indicating loss of bone behind the hip components.


Microscopic (Pathologist's) Findings

  • Lymphocytic Infiltration - Lymphocytes are white blood cells that are usually involved in allergic-type reactions. They are also involved in responses to chronic problems in the body (inflammation). These are different than the white cells involved in the response to an acute inflammatory problem, like infection (PMNs or polymorphonucleocytes). The response to metal-on-metal problems has been termed ALVAL (aseptic lymphocyte dominated vasculitis associated lesion). Under the microscope, this looks like a prominent perivascular reaction that is reminiscent of an allergic reaction. The lymphocytic aggregates are believed to be a response to metallic degradation products generated at the metal-on-metal bearing. They tend to cluster around microscopic blood vessels, which is why the word "perivascular" is used, but they can be present diffusely in the tissue as well. No grading system exists for scoring the severity of ALVAL. Its presence merely means that there is a chronic metal-on-metal problem.
  • Necrosis - typically present in areas where blood supply is poor. Any expanding tissue process can do this and necrosis is therefore not specific to ALVAL. Nonetheless, it is not good to have significant necrotic tissue in the joint. Tissues with poor blood supply do not heal well, and are at higher risk for infection. No grading system exists for scoring the severity of necrosis. Its presence merely means that there is a local problem.
  • Histiocytes - a.k.a macrophages - these are cells that eat foreign bodies - they may be seen microscopically in the area of the hip, eating up the metal debris, and can aggregate to form granulomas.
Contact Us

If you think you have a DePuy hip implant and would like to know more about the case, give our offices a call at 1-800-677-7095. Our people are standing by to answer your questions and explain how we can help.


DePuy Crib Sheets

Deciding what you want to do in the aftermath of this hip recall is extremely difficult. There are important medical and legal decisions to make, and you may not be feeling up to the task of figuring out the right questions to ask. We thought we'd try to make that a little easier for you.

Medical Crib Sheets
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Learn more about the DePuy Hip Recall Cheat Sheets or just go right ahead and download them - they're absolutely free and we hope they help during this difficult time.

DePuy Recall In The News

As new updates appear in the news on the DePuy hip recall and the ASR XL Acetabular System, we put those links up here so you can stay informed. If you'd like to be notified when we have news updates, please subscribe to our feed.

August 22, 2012
Johnson & Johnson Agrees to Pay About $200,000 Per Case to Settle Three ASR Lawsuits in Nevada
www.washpost.bloomberg.com

June 27, 2012
FDA Holds Hearing on Metal Hips But Dodges Fundamental Question of Inadequacy of Testing 
www.nytimes.com

March 12, 2012
Too Little Too Late? Researchers Conclude Metal on Metal Hip Replacements Should Not Be Used.
www.bbc.co.uk

»Read our complete archive of articles about the Depuy hip recall.

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