Elevated serum cobalt with metal-on-metal articulating surfaces

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Toxicology

Background:

• Total hip arthroplasty (THA) is a common procedure to address hip joint degeneration.
• Metal-on-metal (MoM) bearings in THA have raised concerns regarding ion release.
• Cobalt (Co) is a key component in many metal alloy implants.

Purpose of the Study:

• To quantify serum cobalt levels in patients following implantation of uncemented total hip arthroplasties.
• To compare cobalt release between metal-on-metal (Co-28Cr-6Mo-0.2C) and ceramic-on-polyethylene hip articulations.
• To investigate systemic cobalt exposure from MoM bearings.

Main Methods:

• A randomized, prospective trial involving 55 patients undergoing uncemented THA.
• Serum cobalt levels were measured using atomic absorption spectrophotometry before and after surgery.
• Comparison between 27 MoM hips and 28 ceramic-on-polyethylene hips, excluding other cobalt sources.

Main Results:

• Patients with MoM bearings showed detectable serum cobalt levels one year post-implantation (median 1.1 microg/l).
• Serum cobalt levels in the ceramic-on-polyethylene group remained below the detection limit (median < 0.3 microg/l).
• The difference in serum cobalt levels between the two groups was statistically significant (p < 0.0001).

Conclusions:

• Metal-on-metal bearings in total hip arthroplasty are associated with systemic release of cobalt.
• Ceramic-on-polyethylene bearings do not appear to contribute to systemic cobalt loading.
• The findings highlight potential toxicological concerns related to cobalt exposure from MoM implants.