Antibacterial coating of implants in orthopaedics and trauma: a classification proposal in an evolving panorama

Abstract

Implanted biomaterials play a key role in current success of orthopedic and trauma surgery. However, implant-related infections remain among the leading reasons for failure with high economical and social associated costs. According to the current knowledge, probably the most critical pathogenic event in the development of implant-related infection is biofilm formation, which starts immediately after bacterial adhesion on an implant and effectively protects the microorganisms from the immune system and systemic antibiotics. A rationale, modern prevention of biomaterial-associated infections should then specifically focus on inhibition of both bacterial adhesion and biofilm formation. Nonetheless, currently available prophylactic measures, although partially effective in reducing surgical site infections, are not based on the pathogenesis of biofilm-related infections and unacceptable high rates of septic complications, especially in high-risk patients and procedures, are still reported.In the last decade, several studies have investigated the ability of implant surface modifications to minimize bacterial adhesion, inhibit biofilm formation, and provide effective bacterial killing to protect implanted biomaterials, even if there still is a great discrepancy between proposed and clinically implemented strategies and a lack of a common language to evaluate them.To move a step forward towards a more systematic approach in this promising but complicated field, here we provide a detailed overview and an original classification of the various technologies under study or already in the market. We may distinguish the following: 1. Passive surface finishing/modification (PSM): passive coatings that do not release bactericidal agents to the surrounding tissues, but are aimed at preventing or reducing bacterial adhesion through surface chemistry and/or structure modifications; 2. Active surface finishing/modification (ASM): active coatings that feature pharmacologically active pre-incorporated bactericidal agents; and 3. Local carriers or coatings (LCC): local antibacterial carriers or coatings, biodegradable or not, applied at the time of the surgical procedure, immediately prior or at the same time of the implant and around it. Classifying different technologies may be useful in order to better compare different solutions, to improve the design of validation tests and, hopefully, to improve and speed up the regulatory process in this rapidly evolving field.

Fast-resorbable antibiotic-loaded hydrogel coating to reduce postsurgical infection after internal osteosynthesis: A multicenter randomized controlled trial

“…It is also the first clinical demonstration that short-term local prophylaxis may significantly reduce post-surgical septic complications in internal osteosynthesis for closed fractures. Clinical demonstration of safety is a basic requirement of any novel coating technology [18,35]. The reported combined data from five European centers indicate that the device under study can be considered clinically safe, when used in combination with internal osteosynthesis, without any detectable local side-effects both concerning wound and bone healing, at a medium-term follow-up.…”

“…A strong recommendation was delivered in a recent international Consensus meeting on peri-prosthetic joint infections, concerning the need for developing effective antibacterial surfaces that prevent bacterial adhesion and colonization of implants and proliferation into the surrounding tissues [16]. However, only few antibacterial coating technologies are currently available in orthopedics and trauma and, for various reasons, they are still far from large-scale application [17,18].…”

Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application

“…Two major strategies have been employed to solve the above mentioned Gordian knot. One is surface modification1819 and the other is adding alloying elements in order to form novel TiNi-based alloy systems1620. For the surface modification strategy, Ag has been reported to implanted into TiNi biomedical alloy surfaces to provide antibacterial properties182122, besides, Graphene oxide based coatings have been applied into TiNi alloy surface for antibacterial purposes23.…”

Design of Nanostructured Functional Coatings by Using Wet-Chemistry Methods

“…Antibacterial coating technologies have been recently classified by Romanò et al [99] in three main groups: pre-operative antibacterial local carriers or coatings, active surface modification and passive surface modification. The passive surface modification group includes all surfaces chemically or physically modified to prevent or reduce bacterial adhesion without releasing antibacterial agents.…”