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Effects of Cobalt and Chromium Levels Following Modular Hip Stem Total Hip Arthroplasty
Insights
Revision total hip arthroplasty (THA) decisions for modular hip stem fretting rely solely on patient pain levels. Objective markers like serum cobalt, chromium, or MARS MRI findings did not reliably predict the need for revision THA.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Diagnostic Imaging
Background:
- Increasing rates of revision total hip arthroplasties (THAs) are linked to pain from modular hip stem fretting.
- Objective markers are sought to identify patients requiring revision THA due to fretting.
Purpose of the Study:
- To correlate serum cobalt (Co) and chromium (Cr) levels, and MARS MRI findings with the need for revision THA.
- To evaluate the utility of objective diagnostic tools in assessing fretting-related pain in THA patients.
Main Methods:
- Retrospective study of 66 patients undergoing THA.
- Measured serum Co and Cr levels, and utilized MARS MRI in a subset of patients.
- Correlated objective findings with patient-reported pain scores and need for revision surgery.
Main Results:
- Serum Cr levels showed a trend towards higher levels in patients with positive MARS MRI findings (P=.083).
- Serum Co levels approached significance in patients undergoing revision THA (P=.076).
- Patient pain scores were significantly higher in the revision THA group (P<.001).
Conclusions:
- No objective findings (serum metal ions or MARS MRI) reliably identified patients needing revision THA for fretting.
- Patient-reported pain remains the primary factor in deciding on revision THA for modular hip stem fretting.
Abstract:
Due to the increased number of revision total hip arthroplasties (THAs) to correct pain secondary to fretting from modular hip stems, this study was conducted in an effort to correlate objective findings of serum cobalt (Co) levels, serum chromium (Cr) levels, and/or reactive tissue seen on metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) with a patient's need for revision THA. The study group comprised 66 patients, 18 of whom received MARS MRI. Serum Co levels, serum Cr levels, and standard numeric rating scale for pain were documented for all patients. Statistical analysis was then performed to determine whether there was a correlation between the aforementioned variables and the need for revision THA. Serum Cr levels were higher in patients with positive reactive tissue findings on MARS MRI, although this only approached significance (P=.083). Serum Co levels were higher in those undergoing revision THA, but this also only approached significance (P=.076). Pain scores were significantly different between those undergoing revision and those not (P<.001). It is the opinion of the authors that there is no objective finding in this study that can be used to identify patients who require revision THA secondary to fretting of a modular hip stem prosthesis. Only a patient's stated pain level can assist a surgeon in the decision-making process regarding the need for revision THA secondary to fretting. [Orthopedics.2016; 39(5):288-292.].
