JOA - 2026-05-01 - Journal Article; Systematic Review; Review
Systematic Review of Metal Concentrations in Blood, Serum, and Tissue Following Primary and Revision Total Knee Arthroplasty.
Aslani S, Kurtz MA, Spece H, Mont MA, Mihalko WM, Kurtz SM
Topics
Key Takeaway
Revision and modular TKA produce significantly higher whole blood cobalt and chromium concentrations than primary and monobloc TKA (P<0.05), with median whole blood levels of 1.42 ppb cobalt and 1.44 ppb chromium across all primary TKA studies.
Summary Depth
Choose how much analysis to show on this article page.
Summary
This systematic review of PubMed and Embase asked what metal concentrations are reported after TKA, what thresholds are used, and whether implant design affects in vivo metal levels. Across 33 included studies, median whole blood cobalt and chromium were 1.42 and 1.44 ppb respectively, with cobalt-chromium release correlating linearly (R²=0.98); serum cobalt was higher at 3.19 ppb while serum chromium was lower at 0.95 ppb. Revision and modular TKA produced significantly higher whole blood cobalt and chromium than primary and monobloc designs, and 64% of studies reporting thresholds used ≥2 ppb—a cutoff derived from metal-on-metal THA literature rather than TKA-specific data.
Key Limitation
The absence of TKA-specific organ metal burden data and the reliance on heterogeneous, largely cross-sectional sampling protocols across included studies prevent any causal inference between measured metal concentrations and clinical or biological adverse outcomes.
Original Abstract
BACKGROUND
In a subset of total hip arthroplasty (THA) patients, investigators associate metal release with biological complications. Comparatively, metal release in the knee is less understood. In this study, we systematically reviewed total knee arthroplasty (TKA) metal release studies. We asked: (1) What are the metal concentrations reported in TKA patients? (2) What concentrations do studies use as thresholds? and (3) Does implant design affect metal concentrations in vivo?
METHODS
The PubMed and Embase databases were searched for studies reporting metal concentrations following TKA. There were 33 studies that met the inclusion criteria and were subsequently screened. Linear regressions were used to assess correlations in whole blood and serum, and nonparametric statistics were used to compare implant designs.
RESULTS
Following TKA, studies reported median whole blood concentrations of 1.42 parts per billion (ppb) (cobalt) and 1.44 ppb (chromium). Release of the two metals correlated linearly (R 2 = 0.98). In serum, the documented median values were 3.19 ppb (cobalt) and 0.95 ppb (chromium). Generally, investigators reported higher concentrations of metal release within the periprosthetic tissue. Of the 11 studies that reported a critical threshold value, most studies (64%) used ≥ two ppb. Revision and modular TKA studies measured significantly higher cobalt and chromium concentrations in whole blood compared to primary and monobloc TKA (P < 0.05).
CONCLUSIONS
In the knee, gaps persist in our knowledge of metal release. Few studies measure concentrations in the periprosthetic tissue, and the magnitude of metal transport to organs remains unknown. Additionally, studies largely use thresholds derived from metal-on-metal (MoM) total hip arthroplasty, necessitating new guidelines for the knee. Surgeons should (1) know that metal release occurs in primary TKA patients; (2) carefully weigh the necessity of constrained devices versus the potential for metal release; and (3) consider alternative bearings to metal-on-metal hinges due to the high cobalt and chromium concentrations documented in vivo.