Sunday, January 30, 2011

Continuing Medical Education Panel sponsored by the American Orthopedics Association for Surgeons: Total hip Atheroplasty: Is there a MOM bearings controversy? (Part Two of Five)

Part Two of Five/My notes:

Dr. John Cuckler MD:  Complications of MOM bearings   (Complications of total hip athroplasty with adverse tissue response in 11 patients.)
Initial experience over last 10 years
·         More than 1 million MOM couples in use today with patients
o   resurfacing and conventional
o   conventional hip replacements outnumber resurfacing by 4:1
·         Head size of implants have grown over the years
Known Issues (history):
·         Hypersensitivity (adverse tissue response/osteolysis/tissue necrosis)
o   Initially in 2005 seen as rare
o   No one knows what the prevalence of this occurrence is
o   As MOM implant use increased, so did the occurrence of this hypersensitivity in patients
o   Dr. Cuckler thought it was likely present in about 1 in every 1000 cases.
o   If you suspect osteolysis, might consider sending a frozen section to a pathologist and ask them to look for the lymphocytes. Look for the lymphoreticular response in the synovial fluid (aspirate the joint.)
o   Ask the patient if they have a history of metal allergies especially should look for women who complain that they can’t wear cheap jewelry due to rashes they get from it.  This is an important sign to look for.
o   If you postpone revision of the surgery, after having identified the osteolyis, this could degrade to tissue necrosis.
·         Tissue response to wear debris.
o   Pseudotumors initially associated mostly with resurfacing not total hip replacements
§  Present in MoM, Ceramics and Poly
§  Pseudotumor described as an aggressive response to rapid wear of the implant
·         Tests recommended:
o   Sedimentation rate (ERP)
o   CRP
o   Ultrasound if you can’t do the MARS MRI
o   Aspirate the joint
§  Culture and sensitivity
§  Cell count of more than 2500 per CC and cell block with more than 95% monocytes would indicate a hypersensitivity response.
·         Revision options:
o   Go to a non MOM articular couple
o   Going to CoCr on poly is generally acceptable
o   Should get frozen section path report
·         Results from revision:
o   Tissue necrosis (muscle damage) may be a severe challenge
o   Revise early if suspicious with a constrained component even if you suspect the tissue damage is  minor!
§  Permanent non-repairable tissue damage may occur if left as is.
§  Repairing soft tissue necrosis is very difficult
·         Indications for MOM:
o   Young, active , heavy male with no metal allergies
·         Contraindications for MOM
o   Female, small socket, high risk for renal failure, allergies

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