Introduction: Various antibiotic coatings have been proposed to prevent bacteria colonization and infection of orthopaedic implants. While most of the available technologies seem to provide an effective implant protection from infection, unknown long-term effects of antibiotic coatings raise some concerns for extensive application. Aim of the present study was to develop and test a new fast-resorbable antibacterial carrier to be used as a temporary coating to prevent early bacteria colonization of metallic implants.

Methods: The patented tested hydrogel is a co-polimer comprising hyaluronic acid (HA) and a biocompatible polyester (poly-lactic acid) with or without polyethylene glycol chains to further modulate hydrophilicity and anti-fouling characteristics of the compound. The HA derivative is then added to water and mixed, just before its use, with the chosen antibacterial agent. For the purpose of this study, different HA-PLA derivatives have been tested, with two vancomycin and tobramycin concentrations and manually spread to uniformly cover the surface of a titanium specimen. To evaluate the release of vancomycin or tobramycin, high performance chromatographic analysis (HPLC) was carried out.

Results: Antibacterial hydrogels provided vancomycin release ranging from 47 % to 80 % in two hours to 100 % (complete release) in 24 to 72 hours, with antibiotic concentrations up to 400 times the minimum inhibiting concentration. The combined release of the two antibiotics (1 % w/v) showed 26.8 % release of vancomycin and 35.8 % of tobramycin at 2 hours and complete release at 72 hours. Doubling antibiotic concentration (2 % w/v), yielded 56.6 % and 76.6 % antibiotic release, respectively for vancomycin and tobramycin at 2 hours and complete release at 48 hours.

Discussion and Conclusion: HA chemical derivatization with polyesters leads to the formation of copolymers which can be used to produce antibacterial hydrogels with promising applications in the orthopedic field. These antibacterial hydrogels are in fact easily prepared and spread over a surface, showing the ability of releasing high concentrations of antibiotics for a desired, limited, period of time. Adding antibiotics to the hydrogel just before its use, allows customized antibiotic choice and dosing, avoiding shelf-life problems.

Introduction: Surgical site infection is a growing and expensive complication. Surgical site surveillance is performed with the aid of laboratory tests and clinical evaluation; the latter has some limits, including reproducibility and validation of results and, as suggested by many authors, the need of a dedicated well trained staff. At present no imaging instruments are available for routine objective monitoring of “normal” or complicated surgical site healing. Recently, technological improvement made available for clinical use high resolution portable digital telethermocameras at relatively low-costs. No data are available in the literature, concerning the “physiological” thermographic pattern of surgical wounds in orthopaedics. The aim of this study is then to evaluate the physiological telethermographic pattern of surgical site healing after hip and knee prosthetic surgery, to provide a reference value for further analysis.

Methods: The surgical site of 60 consecutive patients undergoing total hip replacement and 40 patients unde-going total knee replacements were examined at fixed intervals from the day before surgery to six weeks after intervention, using a portable telethermographic camera (AVIO TVS-200EX). Results were compared with contralateral side and with laboratory data.

Results: A physiological “telethermographic pattern” of wound healing was observed and showed to be remarkably reproducible among different patients. A thermographic peak was observed at day 3, with a mean temperature elevation (hottest spot) of 2.3 +− 1.3 ^C after hip replacement and of 2.8 +− 1.5 ^C after total knee replacement. Similar results were obtained when considering the mean surface temperature in a 10 cm rectangle area identified around the surgical wound. Temperature at the surgical site slowly returned to baseline (contralateral side as reference) in a six weeks period.

Discussion and Conclusion: Telethermography through a portable camera appears a reliable, not invasive, not irradiating and easy-to-use tool to monitor surgical site following hip or knee arthroplasty at the patient’s bed. Surgical site show a highly reproducible physiological thermographic pattern, with peak values at day 3 and a constant decrease until normal values at week 6 after surgery. This findings may be used as a reference for further studies, to establish the relevance of abnormal thermographic patterns in connection with surgical site complications.

Introduction: Staphylococci are a well recognized cause of orthopaedic implant infections, due to their ability to produce biofilms, that limit antibiotic and host defence capabilities. To detect serum IgM levels against staphylococcal slime polysaccharide antigens (SSPA), an original immunoenzymatic assay has been previously developed and tested in patients affected by staphylococcal vascular graft infections [The Lancet • 359:2166–2168, 2002]. This is the first report on the efficacy of this serum ELISA testing of anti-SSPA IgM in Staphylococcal Orthopaedic Implant-Related Infections (SOIRI).

Methods: SSPA is extracted and purified using a suitable original patented bacterial strain and method. The immunoenzymatic assay to detect anti-SSPA IgM was performed on sera collected from 53 patients with joint prosthesis (24 hips, 17 knees, 2 shoulders). Each serum sample was tested in triplicate in two different assays and values are expressed as means. Main exclusion criteria were: time from implant < 6 months, rheumatoid arthritis, concurrent known infections. The study was approved by the local ethical committee and all patients gave their informed consent.

28 sera were collected from controls (patients with uninfected joint prosthesis, as judged from clinical, laboratory and radiological data) and 25 sera were obtained from patients with known SOIRI, sustained by S. aureus or coagulase-negative Staphilococci (CNS) (positive joint aspiration and/or intra-operative cultural examination).

Results: 25 patients were classified as true negative, 21 true positive, 4 false negative, 3 false positive. Test efficacy calculation provided the following Results: sensitivity: 84 %, specificity: 89.3 %, positive predictive value: 87.5 %, negative predictive value: 86.2 %.

Discussion and Conclusion: Anti-SSPA IgM immunoenzymatic assay showed interesting sensitivity and specificity in this preliminary prospective study. The test appear as an innovative, user-friendly, cheap and non-invasive diagnostic tool for orthopaedic implant-related infections. Further studies should be devoted to better define the cut-off value, testing reproducibility and standardization for large scale application.

Two-stage revision is the most widely accepted and performed intervention for chronically infected joint prosthesis. The choice of this option relies on the following considerations:

higher antibiotic concentrations may be used in the spacers, compared to the cement used for prosthetic fixation in a single-stage procedure, since high dose antibiotic-loaded cement may be too fragile for long term prosthesis fixation (Bucholz, 1986);

Two-stage reimplantation using an articulated interval spacer of antibiotic-impregnated bone-cement has been previously investigated and proved as an effective Method:

to adequately fill the void created by the implant removal,

However a considerable variation in the form and function of interval spacers exists. A spacer may in fact be commercially made, or it may be custom-made in the operating room. It may be made entirely of polymethylmethacrylate cement, or it may be a cement-coated metal composite. Favorable results have been reported with each of these types of spacers.

Preformed antibiotic-loaded spacers (InterSpace® Hip and InterSpace® Knee, Tecres SpA, Verona, Italy – Hexactech Inc. Gainesville, Florida) offer:

known mechanical resistance;