Metalosis

Metalosis is a term associated with the issues and complications resulting from metal ion wear debris generated by joint replacement.  Although metalosis can occur in hip, knee, or other joint replacements, traditionally it was a rare phenomenon occurring only after complete bearing surface failure with contact between the metal components on either side of a replaced joint that were never designed to be in contact with one another.

Recent new implant designs in total hip arthroplasty have resulted in an increase in the occurrence of metalosis in joint replacement, with metal debris being generated in two main ways.  In the first instance, metal debris are generated by a metal-on-metal articulation (metal ball contacting a metal socket.)  In the second instance, metal debris are generated at the stem neck-stem body interface of modular neck stems.  The metalosis associated with modular neck stems seems to cause a more aggressive soft tissue reaction, which can be referred to as a pseudotumor, and which can damage the soft tissues, bone, and tendon attachments around the hip joint.  There may also be increased metal wear debris generated at the head-neck junction associated with the larger metal femoral heads used in metal-on-metal articulations.

Metal ions, particularly cobalt, are known to be toxic to cells and tissues, and at elevated levels can cause systemic issues including: skin rashes or reactions, cardiomyopathy, neuropathy, compromised renal function, thyroid dysfunction, psychological status changes including depression or cognitive impairment, and cancer and other malignancies.

Because of metalosis concerns, several implants have been removed or withdrawn from the market, and others have been formally recalled.  Implants that have been recalled include the Stryker Rejuvenate and ABG II modular neck stems, and the Depuy ASR metal-on-metal(MOM) articulation.  Other implants with recognized metalosis issues include the Biomet Magnum and Depuy Pinnacle, and Wright Medical metal-on-metal(MOM) articulations.  However, not just these recalled or withdrawn implants are being called into question.  There are progressive concerns that the basic designs (large head metal-on-metal articulations and modular neck stems) are flawed, and that many more patients with implants of these design types need to be screened and evaluated for metalosis issues.

Evaluation and workup of total hip arthroplasty for metalosis involves a careful history, physical exam, and x-rays.  Additional studies include blood work to assess for infection/inflammation, metal ion testing of blood and urine, a hip aspiration arthrogram with fluid evaluated for cells/crystals/organisms, and a MARS (Metal Artifact Reduction Sequence) MRI to assess the periarticular area for a pseudotumor/fluid collection which can be associated with metalosis.

Joint Replacement Surgeon in Palm Beach Gardens, FL

Addressing these problematic implants usually requires revision surgery.  In the least invasive scenario, only the bearing surface need be exchanged.  However, more advanced problems may require revision of one or all components, depending on the issues.  Also, patients with metalosis with soft tissue reactions and damage to surrounding hip tissue and bone may require more complex reconstruction including bone grafting, and this soft tissue and bone damage can lead to increased risk and problems with hip joint function and instability in the future.

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