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Serum metal ion concentration: comparison between small and large head metal-on-metal total hip arthroplasty
Rhett K Hallows1, Christopher E Pelt, Jill A Erickson
1Intermountain Orthopaedic Specialty Group, LDS Hospital, Salt Lake City, Utah, USA. *Intermountain Orthopaedic Specialty Group, LDS Hospital, Salt Lake City, Utah, USA.
Insights
Serum chromium and cobalt levels were compared in hip replacement patients. Metal-on-metal implants showed higher ion levels than metal-on-polyethylene, indicating potential concerns for these artificial hip joints.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Toxicology
Background:
- Metal-on-metal hip articulations have raised concerns regarding ion release.
- Understanding serum metal ion concentrations is crucial for evaluating implant safety and longevity.
- Previous studies have shown variable results regarding chromium and cobalt levels in patients with metal-on-metal hip prostheses.
Purpose of the Study:
- To compare serum metal ion concentrations (chromium and cobalt) in patients with metal-on-metal (MOM) hip articulations versus a metal-on-polyethylene (MOP) control group.
- To investigate the relationship between head size in MOM implants and serum ion levels.
- To assess the correlation between serum ion levels and patient-reported outcomes and radiographic findings.
Main Methods:
- A comparative study involving 46 patients with well-functioning hips.
- Three groups were analyzed: two with MOM articulations (small and large head sizes) and one control MOP group.
- Serum chromium and cobalt levels were measured. Harris Hip Score, UCLA activity score, and radiographs were also performed.
Main Results:
- Serum chromium concentrations were significantly lower in the large head MOM group compared to the small head MOM group (P = .013).
- No significant difference in serum cobalt concentrations was found between the two MOM groups (P = .087).
- Both MOM groups exhibited significantly higher serum chromium and cobalt levels compared to the MOP control group (P < .001 for all comparisons).
Conclusions:
- Metal-on-metal hip articulations result in elevated serum chromium and cobalt levels compared to metal-on-polyethylene implants.
- Larger head MOM implants may lead to lower serum chromium levels than smaller head MOM implants, though cobalt levels did not differ significantly.
- The findings underscore the systemic exposure to metal ions associated with MOM hip prostheses, necessitating careful patient monitoring.
Abstract:
The purpose of this study was to compare serum metal ion concentrations (chromium and cobalt) in 3 groups, 2 with metal-on-metal articulations and a control metal-on-polyethylene group. Forty-six patients with good to well-functioning hips were recruited for the study. Serum ion levels of all patients were drawn, and Harris Hip Score, University of California, Los Angeles activity score, and radiographs were performed. Serum chromium concentrations were significantly lower in the large head group compared with the small head group (P = .013). There was no difference in the cobalt concentrations between the 2 groups (P = .087). There was a significant difference between both metal-on-metal groups when compared with controls for both chromium and cobalt levels (P = .0005 and P = .0004, control vs small; P = .001 and P = .0001, control vs large, respectively).
