| Objective: To establish an animal model of hemiprosthetic hip joint infections and to select optimal timing for two-stage revision arthroplasties for infected hemiprosthetic hip joints in rabbits.Methods: Methicillin-resistant Staphylococcus epidermidis (MRSE) of 1×108CFU was injected into the hemiprosthetic hip joints immediately after the left femoral heads of 96 rabbits were replaced with prostheses, and an animal model of hemiprosthetic hip joint infections was established four weeks later. The infected joints were performed debridements and then two-stage revision arthroplasties. According to the intervals between debridements and revision arthroplasties the rabbits were divided into six groups, i.e., group S0, S2, S3, S4, S6 and S12, each group had 16 rabbits with correspondent intervals of 0, 2, 3, 4, 6 and 12 weeks, and all rabbits were sacrificed 8 weeks after revisions. X-ray graphs were taken to demonstrate dislocations or subluxations after replacements, before debridements and revisions and before sacrifices. Before debridements, revisions and sacrifices samples were collected from inside the joints for bacterial cultures after homogenized with 0.5 ml PBS and for rhodamine-labelled antiserum stains after fixed with 10% formaldehyde. Concentrations of serum CRP and ESR were measured at replacements, debridements, revisions and sacrifices. After the rabbits were sacrificed, samples from around the prostheses and the right and the left femurs were collected. The samples were fixed with 10% formaldehyde, prepared and stained with HE, then the pathological changes were observed with lightmicroscope. The femurs were prepared for prostheses extraction tests.Results: 1. X-ray demonstrated no dislocations or subluxations at replacements, while at debridements 11 hemiprosthetic hip joints were found dislocated and at sacrifices 12 joints dislocated. 2. All hemiprosthetic hip joints were infected 4 weeks after injections. At revisions the rates of infections were 100.0%, 35.7%, 30.7%, 13.3%, 6.2% and 6.2% for group S0, S2, S3, S4, S6 and S12 respectively, while at sacrifices they were 26.7%, 42.8%, 23.1%, 6.7%, 6.7% and 7.1% respectively. Both at revisions and at sacrifices the rates for group S4, S6 and S12 were significantly lowered than that for group S0 (P<0.05). 3. All samples collected from inside the infected hemiprosthetic hip joints showed positive reactions when stained with rhodamine-labelled antiserum. At revisions the rates of positive reactions for group S0, S2, S3, S4, S6 and S12 were 100.0%, 50.0%, 38.4%, 13.3%, 12.5% and 6.2% respectively, and at sacrifices they were 33.3%, 50.0%, 23.1%, 6.7%, 6.7% and 14.3% respectively. Both at revisions and at sacrifices the rates for group S4, S6 and S12 were significantly lowered than that for group S0 (P<0.05). 4. The concentrations of serum CRP and ESR were significantly elevated when the hemiprosthetic hip joints were infected (P<0.01). At revisions and at sacrifices concentrations of CRP for group S4, S6 and S12 were significantly lowered than that at debridements (P<0.05), while for ESR only that for group S12 lowered at revisions (P<0.05). 5. The extraction strength of the left prostheses was lower than that of the right ones. 6. When observed with light microscope, the samples showed much less inflammatory cells infiltration if infections were controlled than that if not controlled.Conclusions: 1. An animal model of hemiprosthetic hip joint infections can be established reliably 4 weeks after MRSE of 1×108 CFU was injected into the joints when the femoral heads were replaced with prostheses. 2. After debridements the infected hemiprosthetic hip joints could be revised and thusan animal model for two-stage revision arthroplasties can be established successfully. 3. Bacterial culture acts as "gold standard" for detecting hemiprosthetic hip joint infections though rhodamine-labelled antiserum stain owns more sensitivity. 4. Measuring of serum CRP and ESR is important in detecting hemiprosthetic hip joint infections and in... |
PDF Full Text Request