Similar outcome during short-term follow-up after coated and uncoated total knee arthroplasty: a randomized controlled study
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Patients with known hypersensitivity to metals often require hypoallergenic TKA implants. Coating of a standard implant is a common solution, and although in vitro tests have demonstrated reduction of polyethylene wear for these coatings, it is still unknown whether these implants have any clinical benefit. This study was initiated to investigate metal ion concentrations, knee function and patient-reported outcome (PRO) after coated and uncoated TKA.
One hundred and twenty-two (122) patients were randomized to receive a coated or a standard TKA and, after exclusions, 59 patients were included in each group. Knee function and PRO were assessed with validated scores up to 3 years after surgery. Metal ion concentrations in blood samples were determined for chromium, cobalt, molybdenum and nickel, preoperatively and 1 year after surgery.
Chromium concentrations in patient plasma increased from a median of 0.25 to 1.30 µg/l in the standard TKA group, and from 0.25 to 0.75 µg/l in the coated TKA group (p = 0.012). Thirteen patients (3 coated, 10 standard TKA) had chromium concentrations above 2 µg/l. The concentrations of cobalt, molybdenum and nickel did not change. Patient-reported outcome measures (PROM) demonstrated a substantial improvement after TKA, without any differences between the groups.
The increase in chromium concentration in the standard group needs further investigation. If surgeons use coated implants, they can be confident that these implants perform as well as standard implants.
Level of evidence
KeywordsTotal knee arthroplasty Total knee replacement Results Coated implant Allergy Metal hypersensitivity Metal ions
American Society of Anesthesiologists physical status classification
Body mass index
General health perceptions index (SF-36)
Health-related quality of life
International Organization for Standardization
Length of hospital stay
Mental health index (SF-36)
Oxford Knee Score
Bodily pain index (SF-36)
Physical function index (SF-36)
Physical vapor deposition method
Role-emotional index (SF-36)
Role physical index (SF-36)
- SF 36
Short Form 36
Social functioning index (SF-36)
Total knee arthroplasty
University of Los Angeles
Ultrahigh-molecular-weight polyethylene insert
Vitality index (SF-36)
This study was supported by a research grant from Mathys AG (Bettlach, Switzerland). The authors thank Brit Brethfeld and Anne Schützer for their valuable assistance during follow-up and data management and Gary Jennings for language editing.
JL designed the study, all authors were involved in study implementation, CL and FB performed data management and statistical analysis, AP wrote the first draft, and all authors contributed to and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
Prof. Lützner has received payments for lectures from Aesculap and Mathys, all other authors declare no conflict of interest.
The study was performed in compliance with the Helsinki Declaration and is registered at ClinicalTrials.gov (NCT03047564). Institutional review board approval was granted from TU Dresden (EK 339092011).
All patients signed informed consent.
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