Levels of silver ions in body fluids and clinical results in silver-coated megaprostheses after tumour, trauma or failed arthroplasty

Introduction: Infection in megaprostheses remains an unsolved problem, with a rate of occurrence ranging from 5% to 12%. Silver coating of medical devices has recently been proposed to reduce infection rate because of the antibacterial effect of silver. This innovation could be particularly interesting for megaprostheses, but few data have been reported in the literature. Materials and methods: From June 2010 to August 2014 a modified MegaC System megaprosthesis with an innovative peripheral silver-added layer of titanium alloy ('Porag') was implanted in 33 patients after previous infection (21 patients) or at high risk for infection because of local or general conditions (12 patients). Previous infection followed megaprosthesis or standard arthroplasty procedures in 14 patients and trauma surgery in seven patients. A proximal femur replacement was performed in 13 patients, distal femur replacement in 13, total femur in one, and knee arthrodesis in six. Clinical results and levels of silver in blood, urine and wound drains were examined. Results: Minimum follow-up of the patients was one year (average 25.9 months).There was no infection during the first two years after surgery in the 12 patients who received a silver-coated megaprosthesis and had no previous history of infection. An infection developed in one patient at 25 months after surgery following two further surgical procedures.Infection recurred at seven months and 24 months in two out of the 21 patients (9.5%) who had received the implant because of previous septic complications.There was no clinical evidence of argyria, and no local or systemic side effects related to silver were detected.Mean levels of silver ranging from 0.41 to 5.33. μg/L in blood and from 0.28 to 0.86. μg/L in urine were detected at 24. h to 36 months after surgery. Conclusions: Silver-coated megaprostheses showed promising results in this series in terms of prevention of infection in a high-risk group of patients, many of whom had a history of infection. No side-effects were detected. The circulating silver levels confirm both the persistence of silver-coating activity after three years and the safety of silver-coated implants. Longer follow-up and larger series are needed.