Study Of One-stage Revision Total Knee Arthroplasty For Infection In Rabbits

Objective: Using a rabbit model of methicillin-resistant Staphylococcus aureus knee-prosthesis infection, the efficacy of one-stage revision total knee arthroplasty for infection resulting from high virulence germ was studied in the experiment. Methods: Establishment of animal model:A new kind of prosthesis, which consists of Co-Cr-Mo alloy femoral component and high molecular weight polyethylene tibial tray, was implanted into right knee of 48 New Zealand White rabbits. Four weeks after arthroplasty, the rabbits were randomly divided into four groups, ie, control group, experimental group A, group B and group C. Each right knee was inoculated with 0, 5×103, 5×105, 5×107 colony forming units (CFU) MRSA respectively. The levels of serum C-reaction protein and Erythrocyte sedimentation rate were monitored. Animals were sacrificed after 4 weeks. Joint aspirate, tissues, biomaterial and blood samples were examined for evidence of infection. Accessment of revision: Four weeks after total knee arthroplasty in 48 rabbits, the dose of 5×105 CFU MRSA was inoculated into all right knees to establish infection model. The rabbits were randomly divided into 2 groups:experimental group and control group. Four weeks after inoculation, the former was treated with one-stage revision, and the first procedure of two-stage revision was performed in the latter—inserting gentamycin-containing cement spacers into the knee after surgical debridment and removal of prostheses. The levels of serum C-reaction protein and Erythrocyte sedimentation rate were monitored in ten phase, i. e. prior to TKA and revision, 1, 3, 5, 7 days and 2, 4, 6, 12 weeks after revision. Twelve weeks after revision, animals were sacrificed to obtain joint samples to examine for evidence of infection. Results: Establishment of animal model: None of the knees in the control group was infected after injected with 0. 45% saline, seven of 12 knees developed a biomaterial centered infection in group A when 5×103 CFU MRSA was introduced. All knees developed a biomaterial centered infection in group B or group C when 5×105 CFU and 5×107 CFU MRSA were injected respectively. No evidence of septicemia was found in the control group, group A and group B. But five blood cultures were positive in group C. The levels of serum CRP elevated and reached their peaks at day 3, while that of ESR at day 7. Accessment of revision:All knees were infected after the dose of 5×105CFU MRSA was inoculated. Twelve weeks after revision, the recurrence rates of infection in experimental group and control group were 22. 7%(5/22)and 14. 3%(3/21)respectively. There was no statistical significance between the two groups(P>0. 05). The incidences of drug resistant strain in the re-infection was 80%(4/25)in the experimental group, while 66. 7%(2/3)in the control group(P>0. 05). The levels of serum CRP and ESR elevated after revision and reached their peaks at day 3 and day 5 respectively. They droped into the level prior to TKA at week 4 and week 12 respectively. Conclusions Four weeks after inoculating the dose of 5×105 CFU MRSA, A model of knee prosthesis joint infection in rabbits can be estabilished successfully;The short-term efficacy of one-stage revision total knee arthroplasty for infection resulting from methicillin-resistant Staphylococcus aureus is similar to that of two-stage revision. An important reason of re-infection is the occurrence of drug resistant strain. The existence of prosthesis does not increase the probability of the occurrence of drug resistant strain.