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All in all implant associated infection rarely occurs in orthopaedics. Nevertheless it is a serious complication that may result in decelerated fracture healing, loosened implants, function loss and osteomyelitis. The pathogenesis of numerous infections in surgical orthopaedics is influenced by microorganisms in biofilm. Biofilm bacteria make up 60 % of entire nosocomial infections. For the first time ever, the survey here presents analyses of the incidence of infection of explants and associated complications as well as the spectrum of pathogens, to find possible risk factors regarding plate osteosynthesis. The study includes 51 dogs and 14 cats of differents breeds having had plate osteosynthesis with screws which were removed between February 2010 and March 2013 and Microbiologic samples were taken. In 49,3 % of those explants (n = 35) microorganisms were detected. Staphylococcus ssp. was detected most frequently.
The healing process was uncomplicated in 26 of 68 operations examined although 12 explants of this group showed microbiological agents. In 21 out of 42 patients having complications (50%) microorganisms were detected. Likelihood of infection increases by ascending age and weight. Infection risk was influenced by body weight and age. Sex was not a relevant parameter
for risk of infection.
Areas distales of the elbow (n = 18/21, 85,7%) and knee joint (n = 10/14, 71,4 % ) were infected more often compared to proximal locations. Explants of trauma patients suffering from lung lesions were significantly more often infected. (p = 0,028). Additional lesions such as superficial wounds and fractures had no significant influence on the manifestion of an infection of the explant.
With 59, 5% infections of non-contact-plates occured more frequently compared to infections of dynamic-compression-plates (39,3%) and t-plates (33,3%). 38,5% of thin 2 to 2,7 mm explants were infected as well as 62,5% of thick 3,5 to 4,5 mm explants.
There is a percental higher risk of infection of the explant in surgery performed by an experienced surgeon (52%) in comparison to an inexperienced surgeon (42,9%). The risk of infection increases by the number of persons attending. One person assisting led to a 42,9% risk of infection, as with two it made 66,7%. 14 out of 16 operations with three assistants attending were performed by an experienced surgeon.
Risk of infection decreased with duration of hospitalization. Time in situ has no significant influence on the risk of infection. In 36 out of 68 cases no abnormality was detected radiographically at time of explantation. In 32 cases the following findings were diagnosed most often: osteolysis (n =20, 29,4%), demineralisation of the bone in plate zone (n = 9, 13,2%), implant break (n = 2, 2,9%), loosened screws (n = 6, 8,8 %), deflection of plates (n = 2, 2,9%) and sequestration (n = 2, 2,9%). 60% of the explants of patients showing visible osteolysis were infected. Just as well in 55,6, % (n = 5) of the explants of those patients dealing with evident bone deterioration, 50% with loosend screws and 28,6 % (n=2) with implant break.
73,3 % of animals showing dysfunctional mobility at time of explantation, with limb in a misalignment or swollen had infected explants. In 5 patients (n = 51 9,8%) an osteomyelitis was detected clincially and radiographically at time of explantation.
The survey hardly determined statistically significant factors but revealed those which by trend promote infections. Almost 50% of the entire explants were colonised with microorganisms, although just 7,4% of the patients fell ill.
Following clincial trails should establish defined sampling plans for microbial analysis (at time of opening the operation field, before wound closure and explantation) as well as increase the number of patients participating to substantiate the relevance of results.