Features of implant-associated infection
Unlike contact or airborne routes of infection, where the contact between microflora and tissues is short-lived, implant-associated infection has a number of characteristic features:
- Microorganisms are present in the tissues for the entire time the implant remains in the body.
- Any implanted material acts as a foreign body, which helps maintain the inflammatory process.
- Conservative treatment is often ineffective; extracting the implant (prosthesis, ligature) is usually required to eliminate the focus.
- Transition into a "dormant" form is possible: the microflora becomes isolated together with the foreign body in a peculiar connective tissue capsule. In such cases, inflammation may manifest clinically only months or even years later.
Classification and requirements for suture material
Suture material (threads, staples, wire) is the leading cause of implant-associated infection.
There are two main groups of threads/sutures:
- Absorbable: natural (catgut, including chromic or silver catgut for longer absorption) and synthetic (Dexon, Vicryl).
- Non-absorbable: natural (silk, linen, cotton, horsehair) and synthetic (capron, nylon, Dacron/lavsan, etc.).
The ideal suture material must meet strict requirements:
- Have a smooth, even surface to prevent additional tissue trauma.
- Be elastic (to prevent tissue compression during edema) and have good glide.
- Be strong, non-hygroscopic (do not absorb moisture), and not swell.
- Be biologically inert: cause no allergies and be biocompatible.
- Absorption (biodegradation) time should correspond to the wound healing time.
There are also antimicrobial sutures (e.g., Letilan-Lavsan). Drugs (antibiotics, nitrofurans) are incorporated into their structure, which significantly reduces the risk of wound suppuration.
Methods of suture sterilization
The main and most reliable method is the factory method using $\gamma$-radiation. The material is supplied in special packaging (atraumatic sutures with a pre-crimped needle) or in ampoules. Such sutures cause minimal tissue trauma.
In healthcare facilities, hospital-based methods are used:
- Metallic material and most synthetic/natural sutures (lavsan, cotton) are sterilized by autoclaving or boiling.
- For catgut, chemical methods are used (if factory-sterilized is unavailable). The sutures are first degreased in ether (24 hours).
- Claudius method: catgut is kept in an aqueous Lugol's solution twice for 10 days, then transferred to 96% alcohol.
- Gubarev method: similar, but alcoholic Lugol's solution is used (twice for 10 days).
- Kocher method (for silk, capron): includes washing in soapy water, drying, degreasing in ether, keeping in 70% alcohol, and boiling in mercuric chloride solution (for silk).
Sterilization of prostheses and grafts
The choice of sterilization method depends on the type of implanted device:
- Metal structures (pins, screws, plates) are treated with high temperatures — in a dry heat sterilizer, autoclave, or by boiling.
- Complex prostheses (combination of metal and plastic, e.g., heart valves) are sterilized with gas sterilizers or chemical antiseptics (followed by mandatory rinsing with a sterile isotonic solution).
- Synthetic meshes and vascular grafts (made of lavsan, capron) are boiled or placed in antiseptics.
Organ transplantation requires the strictest asepsis at all stages: from donor and surgical team preparation to organ retrieval. After extraction, the organ is flushed with a sterile solution (washing blood out of the vessels), placed in a sealed sterile container with ice, and transported to the surgery site.
Briefly: answers to topical questions
What antiseptics are used for the chemical sterilization of complex prostheses?
For the chemical sterilization of complex-design prostheses (consisting of metal and plastic), chemical antiseptics are used, in particular chlorhexidine solution. After treatment with such solutions, the devices require mandatory rinsing. Before implantation, prostheses must be thoroughly rinsed with a sterile isotonic sodium chloride solution to remove chemical residues.
What specific complications are caused by leaving non-absorbable ligatures in a wound?
Leaving suture material in a wound can lead to suppuration around it. A specific complication is a suture fistula, caused by suppuration around the suture material. The implant sustains the inflammatory process, treatment of which is unsuccessful until the implant, including the ligature, is rejected or removed.
What gases are used in gas sterilizers for processing prostheses?
Toxic gases with high penetrating ability are used in gas sterilizers to process implants and complex prostheses. The following sterilizing agents are used:
- Ethylene oxide — used in pure form at a temperature of 18 °C.
- OB mixture — includes ethylene oxide and methyl bromide (methylene bromide), used at a temperature of 55 °C.
- Formaldehyde — frequently used in hospital settings.
These substances are alkylating agents that damage nucleic acids and cause microorganism death.
Class and exam questions
Because an implant is a foreign body around which a capsule forms, isolating the microflora. Until the foreign body is removed, the inflammatory process typically persists.
What is the advantage of atraumatic suture material?
Which method of catgut sterilization is preferred?
The factory sterilization method using $\gamma$-radiation (gamma radiation) is preferred.
What should be done with a prosthesis sterilized in an antiseptic solution before placement into the body?
It must be thoroughly rinsed with a sterile isotonic sodium chloride solution to wash away chemical residues.
What else to study on this topic
- Detailed composition of Lugol's solutions (aqueous and alcoholic) for sterilization
- Properties and types of antimicrobial suture materials (fluorlon, acetate)
- Steps of the Kocher method (detailed algorithm)
- Differences in the processing of natural and synthetic absorbable sutures
- Organization of sterile transport of donor organs
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Other topics in the section "CHAPTER 2. ASEPSIS AND ANTISEPSIS"
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