Abstract
Introduction
Mechanical or corrosive failure of total knee arthroplasties (TKAs) is difficult to diagnose with current laboratory and radiographic analyses. As such, the goal of this study was to determine the mean blood concentration of cobalt, chromium, and titanium in a series of revision TKAs with mechanical implant failure and evaluate whether they facilitated identification of the underlying TKA failure mechanism.
Methods
Serum cobalt, chromium, and titanium levels and synovial fluid characteristics were evaluated in 12 patients (13 aseptic revision TKAs) who underwent revision TKA between 2000 and 2020 at a single academic institution for mechanical implant failure or corrosion. Seventy-five percent were re-revisions of previously revised TKAs. Mean time to revision was 6 years. Modular metallic junctions were present in 100%. Twenty-five percent did not have another in situ total joint arthroplasty, and the remaining patients did not have a metal-on-metal articulation that could lead to elevation in serum metal ion levels. Mean follow-up after the revision TKA was 8 months.
Results
Mean serum cobalt, chromium, and titanium concentrations were 11 ng/mL, 6 ng/mL, and 3 ng/mL, respectively. Serum metal ion levels facilitated failure mechanism identification in 75%, which included modular junction failure (6 cases), constraint locking mechanism failure (3 cases), corrosion of modular metallic interfaces (2 cases), and implant fracture (1 case). Arthrocentesis was performed in 75%. Mean synovial fluid cell count was 950 cells/mcL. Monocytes were the predominant mean cell type (41%), followed by neutrophils (35%), and lymphocytes (22%).
Conclusion
Serum metal ion assessment should be considered when the etiology of painful primary or revision TKAs, particularly those with modular metallic junctions, remains elusive after routine evaluation.
