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Metal-on-metal THA increases HLA DR+CD8+ T-cells & correlates with immunological reactions
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April 2013
Metal-on-metal THA increases HLA DR+CD8+ T-cells & correlates with immunological reactions
Study Type:Therapy
OE Level Evidence:2
Journal Level of Evidence:N/A
Elevation of circulating HLA DR(+) CD8(+) T-cells and correlation with chromium and cobalt concentrations 6 years after metal-on-metal hip arthroplasty
Acta Orthop. 2011 Feb;82(1):6-12. Epub 2010 Dec 29Did you know you're eligible to earn 0.5 CME credits for reading this report? Click Here
Synopsis
85 patients undergoing total hip arthroplasty (THA) were randomized to receive either a metal-on-metal bearing or a metal-on-polyethylene prosthesis. The primary outcome was elevation of circulating HLA DR+ CD8+ T-cells and correlation with chromium and cobalt concentrations. Results indicated that metal-on-metal THA increased chromium and cobalt concentrations which resulted in a correlation in immunological reactions. This was associated with the increase in HLA DR+CD8+ T-cells and a decrease in B-cells.
Publication Funding Details
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Funding:
Non-Industry funded
Sponsor:
Sven Noren Bequest Fund
Conflicts:
None disclosed
Was the allocation sequence adequately generated?
Was allocation adequately concealed?
Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?
Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?
Blinding Patients: Was knowledge of the allocated interventions adequately prevented?
Was loss to follow-up (missing outcome data) infrequent?
Are reports of the study free of suggestion of selective outcome reporting?
Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?
Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?
Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?
Yes = 1
Uncertain = 0.5
Not Relevant = 0
No = 0
The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.
1/4
Randomization
3/4
Outcome Measurements
4/4
Inclusion / Exclusion
4/4
Therapy Description
4/4
Statistics
Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.
Why was this study needed now?
A number of immunological reactions occur after metal-on-metal total hip arthroplasty (THA). The hypothesis was that an increased concentration of metal ions caused changes in the lymphocyte sub-populations. This study examines the change in concentration of HLA DR+ CD8+ T-cells and correlation with chromium and cobalt concentrations.
What was the principal research question?
What are the elevation of circulating HLA DR+ CD8+ T-cells and correlation with chromium and cobalt concentrations in patients 6 years after undergoing metal-on-metal total hip arthroplasty (THA)?
Study Characteristics
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Population:
85 patients undergoing total hip arthroplasty (THA). (Age: 40-75 years)
Intervention:
Metal-on-metal total hip arthroplasty. A high-carbon cobalt-chromium alloy against a cobalt-chromium liner in a polyethylene cup. A standard posterior approach was used for THA. (n=41)
Comparison:
Metal-on-polyethylene total hip arthroplasty. Cobalt chromium head against an all-polyethylene cup. A standard posterior approach was used for THA. (n=44)
Outcomes:
Chromium, cobalt, manganese, and nickel concentration (Measured by high-resolution inductively coupled plasma mass spectrometry), leukocyte subpopulations and immunoglobulins in patient blood (Measured by standard laboratory methods), implant migration relative to surrounding bone, and Harris Hip Score (HHS).
Methods:
RCT
Time:
Mean 82 (72-97) months. (Follow-up at 3, 6, 12, 24, and 72 months)
What were the important findings?
- Serum concentrations of chromium and cobalt were higher in patients who received the metal-on-metal total hip arthroplasty (THA) compared to patients who underwent metal-on-polyethylene THA when examined at follow-up. (Chromium: 1.05 vs. 0.36 microgram/L; p<0.001; Cobalt: 0.86 vs. 0.24 microgram /L; p<0.001)
- The metal-on-metal group had a higher percentage of HLA DR+ CD8+ T-cells. (10.6 vs. 6.7%; p=0.03) This had a positive correlation with cobalt and chromium concentrations in patient blood (Pearsons correlation coefficient for cobalt: 0.36, p=0.03; Chromium: 0.39, p=0.02).
- The metal-on-metal group had a lower percentage of B-cells. (9.3% compared to 12.9% in the metal-on-polyethylene group) (p=0.01)
- Comparable immunoglobulin concentrations and Harris hip scores were seen between the two groups. No radiographic signs of loosening, wear or periprosthetic osteolysis were seen with either group at follow-up.
- Both groups of patients had similar concentrations of immunoglobulins IgG (and subgroups 1-4), IgM, and IgA.
What should I remember most?
Metal-on-metal THA increases cobalt and chromium concentrations at 6-years and produces immunological alterations. Allergic reactions, implant loosening, and lymphocytic pseudotumors may be the result of HLA DR+ CD8+ T-cells, and these cells occur more in patients who have undergone metal-on-metal THA. There is also a positive correlation with HLA DR+ CD8+ T-cells and chromium and cobalt concentrations. Finally, the metal-on-metal group had a reduction in the percentage of B-cells.
How will this affect the care of my patients?
There is still a lack of evidence that the increase in HLA DR+ CD8+ T-cells associated with metal-on-metal THA causes allergic reactions, aseptic loosening, or periprosthetic pseudotumors. Further studies are required to further elicit the pathogenesis of pseudotumor formation.
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