The socio-economic conditions in many developing countries impede widespread general use of the assets of biomedical technology. In orthopedics this becomes evident from the large-scale, though illegal, reuse of osteosynthesis plates and screws. Scientific research into the issue of the safe reuse of osteosynthesis materials from a biological point of view has never been done. Therefore the aim of this study is to determine whether plates and screws after simple cleaning, applying means which are available in developing countries, are safe from a biological point of view. Cleaning methods evaluated include a toothbrush, water, detergent and bleach. X-ray photoelectron spectroscopy analysis of cleaned surfaces and water contact angle measurements indicate that application of these methods yield surface characteristics similar to those of new, sterilized plates. If desired, bleach can be applied without affecting the surface properties of the materials.

Subsequently, the reactivity of a mammalian monolayer in response to a used screw (ISO-10993-5) and endotoxin release (USP 27-NF 22) was evaluated, showing that all screws tested are non-cytotoxic with endotoxin release within the requirements of the FDA. This study shows that reuse is not necessarily unsafe from a biological point of view.

Addition of antibiotics to the bone cement decreases the incidence of infection. However, the antibiotic is only partially released. Ultrasound may increase the antibiotic release and furthermore the effectiveness of the antibiotic might be enhanced by the so-called bio-acoustic effect.

The objective of this study was twofold. The first aim was to evaluate to what extent antibiotic release from bone cement could be increased by ultrasound. The second aim was to investigate the viability of bacteria when antibiotic release from bone cements was combined with ultrasound.

Cylindrical bone cement samples of Palacos R-G (loaded with gentamicin) and Copal (loaded with gentamicin and clindamycin) were insonated and antibiotic release was compared with uninsonated samples. In addition, identical samples were used in combination with cultures of bacteria derived from prosthesis-related infections. The viability of these bacteria was determined with and without ultrasound, using unloaded Palacos R as a control.

There was a trend of increased gentamicin release under influence of ultrasound. Clindamycin release from Copal was significantly increased. Ultrasound alone did not affect bacterial viability, but the application of ultrasound in combination with antibiotic-loaded bone cements reduced both planktonic and biofilm bacterial viability.

The release of antibiotics from bone cement was increased by the application of ultrasound. Antibiotic release in combination with ultrasound increases the antimicrobial efficacy against a variety of clinical isolates. The enhanced efficacy against bacteria in the biofilm mode of growth, especially against a gentamicin-resistant strain, is clinically important with regard to the treatment of infected joint prostheses. Ultrasound may also be applied in the early postoperative period to prevent infections, because planktonic bacteria present in the wound and wound area due to inevitable contamination during surgery can then be more effectively prevented from forming a biofilm.

Copal bone cement loaded with gentamicin and clindamicin was developed recently as a response to the emerging occurrence of gentamicin-resistant strains in periprothetic infections. The objective of this study was to compare the in vitro antibiotic release and antimicrobial efficacy of gentamicin/clindamicin-loaded Copal bone cement and gentamicin-loaded Palacos R-G bone cement, as well as biofilm formation on these cements.

In order to determine antibiotic release, cement blocks were placed in phosphate buffer and aliquots were taken at designated times for measurement of antibiotic release. In addition, the bone cement discs were pressed on agar to study the effects of antibiotic release on bacterial growth. Biofilm formation on the different bone cements was also investigated after 1 and 7 days using plate counting and confocal laser scanning microscopy (CLSM). Experiments were done with a gentamicin-sensitive S. aureus and a gentamicin-resistant CNS.

Antibiotic release after 672 h from Copal bone cement was more extensive (65% of the clindamycin and 41% of the gentamicin incorporated) than from Palacos R-G (4% of the gentamicin incorporated). The higher antibiotic release from Copal resulted in a stronger and more prolonged inhibition of bacterial growth on agar. Plate counting and CLSM of biofilms grown on the bone cements showed that antibiotic release reduced bacterial viability, most notably close to the cement surface. Moreover, the gentamicin-sensitive S. aureus formed gentamicin-resistant small colony variants on Palacos R-G, and therefore, Copal was much more effective in decreasing biofilm formation than Palacos R-G.

Biofilm formation on bone cement could be more effectively reduced by incorporation of a second antibiotic, next to gentamicin. Antibiotic release from the cements had a stronger effect on bacteria close to the cement than on bacteria at the outer surface of the bio-film. Clinically, bone cement with two antibiotics may be more effective than cement loaded with only gentamicin. The clinical efficacy of antibiotic loaded bone cements in combination with systemic antibiotics can be explained because antibiotics released from cements kill predominantly the bacteria in the bottom of the biofilm, whereas systemic antibiotics can only deal with bacteria at the outer surface of the biofilm.

Introduction: Biomaterial implants in the human body constitute passive surfaces that are prone to bacterial adhesion as the on-set of biomaterials-associated infection. Antibiotic treatment of infected biomaterial implants is little successful clinically, because the biofilm-mode of growth protects the adhering organisms. Percutaneous implants, such as bone screws used in orthopedics or dental implants, constitute a special class of implants with infection rates exceeding the infection rate of deep body implants by far. Especially fixation frames, used in orthopedic surgery for the treatment of complicated fractures, inevitably become infected during the course of a treatment.

The aim of this study is to determine whether it is possible to stimulate bacterial detachment from surgical stainless steel and decrease the viability of the remaining adhering bacteria using block currents. Method: Bacteria were allowed to adhere from a flowing suspension of high ionic strength in a parallel plate flow chamber, after which the suspension was replaced by a bacterium free solution with 10 mM potassium phosphate buffer. Block currents of 15, 60 and 100 ìA with different frequencies (0.1 to 2 Hz) and duty cycles (5 to 50%) were applied to induce bacterial detachment.

Results: Initial detachment rate increased with increasing frequency and duty cycle, namely from 0 to 3700 cm⁻²s⁻¹. The total detachment percentage for block currents of 100 ìA with 25% to 50% duty cycle and frequencies as of 0.5 Hz are similar for all conditions. The detachment percentage in this range amounts on average 76%, whereas DC currents around 100 ìA have an average of 60%, which was found to be significant lower (p=0.03).

The killing capacity of these current series can be up to two log scales depending on the current.

Conclusion: Current induced detachment of Staphylococcus epidermidis from surgical stainless steel seems very effective, especially for a 100 ìA, 50% duty cycle and 2 Hz block current. The viability of the remaining adhering bacteria decreased with 2 log scales. Clinically this could mean another way of preventing and curing pin tract infection.

Introduction: Local drug delivery yields higher gentamicin concentrations than can be safely achieved with systemic application. Unfortunately, both for beads as well as for bone cements, a sharp drop in release follows high initial gentamicin release. Aim of this study is to compare the effects of pulsed ultrasound on the release of gentamicin from antibiotic-loaded beads and bone cements. Mercury intrusion porosimetry is carried out to compare the pore size distribution in both materials before and after antibiotic release.

Materials and Methods: Ultrasound: Gentamicin release from three brands of gentamicin-loaded bone cement (CMW 1, Palamed G and Palacos R-G) and Septopal gentamicin-loaded beads was measured after 18 h of exposure in PBS to an ultrasonic field of 46.5 kHz in a 1:3 duty cycle with a peak intensity of 500 mW/cm² at the sample position. Ultrasound experiments were performed for 18h in 9-fold on bone cement and in 6-fold on beads. Samples not exposed to ultrasound were used as controls. The gentamicin release was measured with fluorescence polarisation immunoassay. Gentamicin release from insonated and control groups was compared using a two-tailed Student’s t test for independent samples.

Mercury intrusion porosimetry: In order to mimic bone cement and beads after prolonged stay in the human body (i.e. after initial release of the loaded gentamicin) samples were immersed for four and two weeks, in PBS. Immersed and not-immersed samples were compared.

Results: Pulsed ultrasound significantly enhanced gentamicin release from gentamicin-loaded beads, whereas gentamicin release from the gentamicin-loaded bone cements was not significantly enhanced. Mercury intrusion porosimetry revealed a rise in pores between 0.1 and 0.01 um in beads after gentamicin release, while in bone cements no increase in the number of pores before and after antibiotic release was found.

Conclusions: Ultrasound increases gentamicin release from antibiotic-loaded acrylic beads by 15%. Development of pores coincides with increased gentamicin release by ultrasound for beads. Application of ultrasound could optimise usage of an (antibiotic) reservoir in local drug delivery systems to treat bone and soft tissue infections more effectively.

Introduction: One of the primary complications in total hip and knee arthroplasty is infection. One of the major risk factors for deep periprosthetic infection is wound infection. This alone is associated with a substantial morbidity-increase which, in turn, increases hospital admittance time and therefore adds significant costs to the healthcare system. The aim of this study is to determine whether contamination of instruments used during primary insertion of a prosthesis, can be considered an early indicator for the occurrence of prolonged wound discharge. Early antibiotic treatment could then prevent this and decrease hospital admittance time and costs to the health care system.

Material and Methods: During 121 procedures, swabs were taken from the first unused broach at the beginning and at the end of the procedure. Removed material from the bone (acetabulum and femur in the hip joint; femur and tibia in case of the knee joint) was tested for contamination as well. During 50 procedures a control swab was taken. The patients on the ward were also monitored to find out whether prolonged wound discharge occurred and to see after how many days the patients were discharged.

Results: In 46 cases (38%) at least one culture showed microbial growth. In the other 75, there was no growth at all. If one of the cultures is positive, there is a 52% risk of prolonged wound discharge. Ifall cultures are negative, this risk is reduced to 13% (Chi-square: PO.001). Patients with a positive peroperative culture have to remain in the hospital for an additional 2.4 days (T-test: P-0.001).

Conclusion: Peroperative culturing during primary insertion of a knee or hip prosthesis, provides a reliable tool to predict postoperative duration of wound discharge and hospital-admittance time.