Introduction and Objectives: In this study we assessed the usefulness of preoperative urine cultures as a tool to prevent infections due to Gram negative microorganisms in patients undergoing prosthetic surgery.

Materials and Methods: In 2007 procedures were carried out to implant 259 knee prostheses and 101 hip prostheses, 47 of these were revision procedures. Pre-operative exams included urine culture to detect asymptomatic bacteriurias which could be treated before surgery with positive results. A urinary catheter was placed in all patients and removed after 24 hours.

Results: Asymptomatic bacteriuria was found in 13% of patients. In 6 patients the urine culture was positive for more than one microorganism. The most frequently found pathogen was E. coli. All cases were treated with antibiotics and a new urinary culture was carried out before surgery. Our infection rate is 0.8% in primary hip replacements and 8.1% in revisions. And 1.9% in primary knee replacements and 6.7% in revisions. An infection caused by a Gram negative microorganism in a revision THR was caused by a subclavian catheter colonized by Pseudomona aeruginosa.

Discussion and Conclusions: Our preoperative studies protocol includes urine culture. We have not seen any TKR or THR infections caused by Gram negative microorganisms. Therefore, based on this, we suggest that preoperative urine culture is useful to identify asymptomatic bacteriuria and treat it, thereby avoiding infections caused by Gram negative microorganisms in patients undergoing prosthetic surgery.

Some different biodegradable vehicles have been tried in vitro and in vivo as possible methods of local antibiotic therapy.

The aim of this study is to evaluate the effectiveness of collagen-gentamicine (Collatamp^®) to eradicate bacterial colonisation of different biomaterials used in orthopaedic surgery in an in vitro study.

Three samples of similar shapes and dimensions of 4 different materials: stainless steel screw, titanium screw, titanium canulated screw and a cylinder of polyethylene were used. Three different solutions of 49 cc of thioglicolate plus 1cc of solution of methicillin-susceptible and methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis (MacFarland: 3) were prepared. Each solution received one sample of each material so that every material be tested in all 3 preparations. After incubation during one week and confirmation of bacterial colonisation of each sample by swabbing cultures, all of them were introduced in an individual receptacle containing 50 cc of thioglicolate and a piece of 5x5 cm of collagen-gentamicine (corresponding to 650 mg/ml of gentamicine). After incubation we analysed results by new swabbing cultures of all samples.

All samples were highly contaminated with different bacteria before introducing them in thioglicolate with the piece of collagen-gentamicine. After one week all samples were free of bacteria.

This in vitro study demonstrates the effectiveness of collagen-gentamicine in order to eliminate colonisation of different biomaterials used in orthopaedic surgery by most frequent bacteria.