Introduction: Biodegradable systems releasing antibiotics are promising candidates for the management of chronic osteomyelitis. Gentamicin and fluoroquinolones are the commonest antibiotics applied with these systems. The effectiveness of a new system from polymerized dilactide (PLA) with incorporated linezolid has been investigated in a rabbit model for treating osteomyelitis by methicillin-resistant Staphylococcus Aureus (MRSA).

Methods: The PLA – Linezolid system was made after thorough stirring 2gr of polymer with 100 mg of linezolid. Experimental osteomyelitis was established in 40 rabbits by a modification of the Norden model. Methicillin-resistant Staphylococcus aureus (MRSA) was applied as the test isolate. After drilling a hole in the upper right femur, the isolate was inoculated along with a thin needle working as a foreign body. After three weeks the needle was removed and cultured and PLA-Linezolid system was implanted in half of the animals. Animals were sacrificed at regular time intervals and tissue around the site of implantation was sent for histologic examination and quantitative cultures.

Results: At 2 – 4 – 6 – 8 – 10 weeks time after removal of the needle results (mean values) were as follows (Controls/PLA-Linezolid): Log10 (cfu/g) at infection site: 2.99/5.68 – 3.44/3.20 – 3.22/2.39 – 1.00/1.27 – 1.00/1.00 respectively and Δlog10 (cfu/g) compared to start: −0.05/−3.23 – 0.23/0.13 – 0.05/0.93 – 1.34/1.09 – 3.31/3.34 respectively. Histology confirmed the previous mentioned results, showing an early decrease following by late recurrence of the infectious reaction at the animals that PLA-Linezolid system was used.

Conclusions: It is concluded that the applied system achieved an early decrease of the tissue bacterial load which was not maintained until late on follow-up. This might be explained by the bacteriostatic mode of action of linezolid.

Aims: The effectiveness of the local treatment of experimental osteomyelitis caused by MRSA (Methicillin Resistant Staph. aureus) performed with the implantation of acrylic bone cement (PMMA) mixture plus 4% grepaßoxacin into the femur of rabbits. Methods: 36 rabbits with chronic MRSA osteomyelitis of the right femur (Norden Model) were treated with a new local grepaßoxacin delivery system prepared by a mixture of PMMA plus 4% grepaßoxacin. Osteomyelitis was introduced by inoculating of the MRSA and the placement of a needle serving as a foreign body. The follow-up of the infection was performed by clinical, microbiological and x-rays þndings. On the 3rd week all animals were reoperated and the needle was removed followed by implantation of the mixture. One control and þve treated animals were sacriþced each week thereafter until the 6th week. Results: Osteomyelitis was induced in all rabbits. The in vitro grepaßoxacin levels were high for 6 weeks at least. Concerning the histological þndings serious tissue reactions were not observed. The lesions and the bone structure are progressively rehabilated after the implantation. The biomechanical study didnñt inßuence the mechanical properties of bone cement due to grepaßoxacin. Conclusions: The above mixture could be an approved supplementary method for the treatment of bone infections. In the chronic osteomyelitis itñs possible to replace the gentamycin PMMA beads. Furthermore could be use as a spacer in loosen arthroplasties due infection in combination with antibiotic administration.