Introduction: Since the establishment of osteosynthesis as the treatment of choice for bone fractures, the issues relating to complications and their prophylaxis have become a major topic of scientific discussion and research in the field of traumatology. Infection of the bone and soft tissue represents one major complication that arises after the implantation of osteosynthetic material at the fracture site. The treatment of these infections is often time-consuming and involves repeated, extensive surgical interventions. The aim of this study was to acquire information about the effect of an antibacterial and biodegradable poly-L-lactide (PLLA) coated titanium plate osteosynthesis on local infection resistance.

Material and Methods: We compared infection rates in white New Zealand rabbits after titanium plate osteosynthesis of the tibia with or without antibacterial coating after local percutaneous bacterial inoculations at different concentrations (2x10⁵–2xlO⁸):

group I (n=12):uncoated titanium plate,

group II (n=12): PLLA coated titanium plate,

group III (n=12): titanium plate coated with PLLA + 3% Rifampicin and 7% Fusidic acid, group IV (n= 12): titanium plate coated with PLLA + 2% Octenidin und 8% Irgasan.

The plate, the contaminated soft tissues and the underlying bone were removed under sterile conditions after 28 days and quantitatively evaluated for bacterial growth. A stepwise experimental design with an “up-and-down” dosage technique was used to adjust the bacterial challenge in the area of the ID50 (50% infection dose). Statistical evaluation of the differences between the infection rates of both groups was performed using the two-sided Fisher exact test (p< 0.05).

Results: The overall infection rate was 50%. For group I and II the infection rate was both 83% (10 of 12 animals). In group III and IV with antibacterial coating the infection rate was both 17% (2 of 12 animals). The ID50 in the antibacterial coated groups III and IV was recorded as lxl10⁸ CFU, whereas the ID50 values in the groups I and II without antibacterial coating were a hundred times lower at lxl10⁶ CFU, respectively. The difference between the groups with and without antibacterial coating was statistically significant (p=0.033).

Conclusions: Using an antibacterial biodegradable PLLA coating on titanium plates, a significant reduction of infection rate in a canine infection model could be demonstrated. For the first time we were able to show, under standardized and reproducable conditions, that an antiseptic coating leads to the same reduction in infection rate as an antibiotic coating. Taking the problem of antibiotic-induced bacterial resistance into consideration, we thus regard the antiseptic coating, which shows the same level of effectiveness, as advantageous.

Resistance to infection may be influenced by foreign bodies such as devices for fracture fixation. It is known that stainless steel and commercially-pure titanium have different biocompatibilities. We have investigated susceptibility to infection after a local bacterial challenge using standard 2.0 dynamic compression plates of either stainless steel or titanium in rabbit tibiae. After the wounds had been closed, various concentrations of a strain of Staphylococcus aureus were inoculated percutaneously.

Under otherwise identical experimental conditions the rate of infection for steel plates (75%) was significantly higher than that for titanium plates (35%) (p < 0.05).

Any operation involving the implantation of a foreign body increases the risk of infection. The implant material and its surface, the dead space, and any necrosis or vascular changes play a significant role in susceptibility to infection. We investigated the effect of the dead space in an intramedullary nail on the rate of local infection. We inoculated the intramedullary cavities of rabbit tibiae with various concentrations of a human pathogen, of Staphylococcus aureus strain, and then inserted either a solid or a hollow slotted stainless-steel nail. We found a significantly higher rate of infection after use of the slotted nail (59%) than after the solid nail (27%) (p < 0.05).