Similar outcome during short-term follow-up after coated and uncoated total knee arthroplasty: a randomized controlled study
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.
This project was supported by a research grant from Mathys.
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.
- 8.Lützner J, Krummenauer F, Lengel AM, Ziegler J, Witzleb WC (2007) Serum metal ion exposure after total knee arthroplasty. Clin Orthop Relat Res 461:136–142Google Scholar
- 13.Thomas P, Schuh A, Ring J, Thomsen M (2008) [Orthopedic surgical implants and allergies: joint statement by the implant allergy working group (AK 20) of the DGOOC (German association of orthopedics and orthopedic surgery), DKG (German contact dermatitis research group) and dgaki (German society for allergology and clinical immunology)]. Orthopade 37:75–88CrossRefPubMedGoogle Scholar
- 22.Reich J, Thomas P, Hovy L, Lindemaier HL, Zeller R, Schwiesau J (2007) Allergy solutions for orthopaedic Knee-Implants. Biomaterialien 8:109–110Google Scholar
- 24.Vertullo CJ, Lewis PL, Graves S, Kelly L, Lorimer M, Myers P (2017) Twelve-Year Outcomes of an Oxinium Total Knee Replacement Compared with the Same Cobalt-Chromium Design: An Analysis of 17,577 Prostheses from the Australian Orthopaedic Association National Joint Replacement Registry. J Bone Jt Surg Am 99:275–283CrossRefGoogle Scholar
- 28.van der Veen HC, Reininga IH, Zijlstra WP, Boomsma MF, Bulstra SK, van Raay JJ (2015) Pseudotumour incidence, cobalt levels and clinical outcome after large head metal-on-metal and conventional metal-on-polyethylene total hip arthroplasty: mid-term results of a randomised controlled trial. Bone Jt J 97-B:1481–1487CrossRefGoogle Scholar
- 36.National Joint Registry (2017) 14th Annual Report 2017. National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. http://www.njrreports.org.uk/Portals/0/PDFdownloads/NJR%2014th%20Annual%20Report%202017.pdf