BackgroundElective knee and hip arthroplasty is followed by infections in currently about 0.5–2.0 % of cases – a figure which is on the increase due to the rise in primary implants. Correct diagnosis early on is essential so that appropriate therapy can be administered. This work presents a retrospective analysis of the diagnoses of patients suffering infections after total hip or knee arthroplasty.Methods320 patients with prosthetic joint infection (PJI) following knee or hip arthroplasty were identified. They comprised a) 172 patients with an infection after total hip arthroplasty (THA): 56 % females (n = 96) and 44 % males (n = 76) with a mean age of 70.9 (39–92) years; and 148 patients with an infection after total knee arthroplasty (TKA): 55 % females (n = 82) and 45 % males (n = 66) with a mean age of 70.7 (15–87) years.ResultsAlthough significantly more TKA than THA patients reported pain, erythema, a burning sensation and swelling, no differences between the two groups were observed with respect to dysfunction, fever or fatigue. However, significant differences were noted in the diagnosis of loosening (THA 55 %, TKA 31 %, p < 0.001) and suspected infection using conventional X-rays (THA 61 %, TKA 29 %, p < 0.001). FDG-PET-CT produced very good results in nearly 95 % of cases. There were no differences between THA and TKA patients regarding levels of inflammation markers. Histological evaluation proved to be significantly better than microbiological analysis.SummaryThe clinical picture may be non-specific and not show typical inflammatory symptoms for a long time, particularly in PJI of the hip. As imaging only provides reliable conclusions after the symptoms have persisted for a long time, morphological imaging is not suitable for the detection of early infections. FDG-PT-CT proved to be the most successful technique and is likely to be used more frequently in future. Nevertheless, there are currently no laboratory parameters which are suitable for the reliable primary diagnosis of PJI. Diagnosis requires arthrocentesis, and the fluid obtained should always be examined both microbiologically and histologically.

BackgroundModular mega-endoprosthesis systems are used to bridge very large bone defects and have become a widespread method in orthopaedic surgery for the treatment of tumours and revision arthroplasty. However, the indications for the use of modular mega-endoprostheses must be carefully considered. Implanting modular endoprostheses requires major, complication-prone surgery in which the limited salvage procedures should always be borne in mind. The management of periprosthetic infection is particularly difficult and beset with problems.Given this, the present study was designed to gauge the significance of periprosthetic infections in connection with modular mega-implants in the lower extremities among our own patients.MethodsPatients who had been fitted with modular endoprosthesis on a lower extremity at our department between September 1994 and December 2011 were examined retrospectively. A total of 101 patients with 114 modular prostheses were identified. Comprising 30 men (29.7 %) and 71 women (70.3 %), their average age at the time of surgery was 67 years (18–92 years).ResultsThe average follow-up period was 27 months (5 months and 2 weeks to 14 years and 11 months) and the drop-out rate was about 8.8 %. Altogether, there were 19 (17.7 %) endoprosthesis infections: 3 early infections and 16 late or delayed infections. The pathogen spectrum was dominated by coagulase-negative staphylococci (36 %) and Staphylococcus aureus (16 %), including 26 % multi-resistant pathogens. Reinfection occurred in 37 % of cases of infection. Tumours were followed by significantly fewer infections than the other indications. Infections were twice as likely to occur after previous surgery.ConclusionIn our findings modular endoprostheses (18 %) are much more susceptible to infection than primary endoprostheses (0.5–2,5 %). Infection is the most common complication alongside the dislocation of proximal femur endoprostheses. Consistent, radical surgery is essential – although even with an adequate treatment strategy, the recurrence rate is very high. Unfortunately, the functional results are frequently unsatisfactory, with amputation often being the last resort. Therefore, the indication for implantation must be carefully considered and discussed in great detail, especially in the case of multimorbid patients with previous joint infections.

BackgroundHip and knee replacements in patients with bone defects after infection correlates with high rates of reinfection. In this vulnerable patient population, the prevention of reinfection is to be considered superordinate to the functionality and defect bridging. The use of silver coating of aseptic implants as an infection prophylaxis is already proven; however, the significance of these coatings in septic reimplantation of large implants is still not sufficiently investigated.MethodsIn a retrospective analysis, 34 patients who have been treated with a modular mega-endoprosthesis after a cured bone infection of the lower limb (femur or tibia) have been evaluated. One group with 14 patients (NSCG: non silver- coated group) was supplied with the non silver- coated implants: MML München- Lübeck™ modular endoprosthesis system (AQ Implants, Ahrensburg, Germany) or MUTARS® Modular Universal Tumor And Revision System (Implantcast GmbH, Buxtehude, Germany). The other group with 20 patients (SCG: silver- coated group) was supplied with the silver- coated system of MUTARS®. In addition to the clinical findings and the patients’ histories, specifically the reinfection rates, the patients’ mobility was assessed using the New Mobility Score (NMS, by Parker and Palmer).ResultsThe median follow-up period was 72 months, ranging from 6 to 267 months. The dropout rate was 5.8%. The reinfection rate after healed reinfection in SCG was 40% (8/20), in NSCG 57% (8/14), p = 0.34; α =0.05. The time for reinfection was, on average, 14 months (1–72 months) in SCG and 8 months (1–48 months) in the NSCG (p = 0.61; α =0.05). The two groups showed no differences in the NMS.ConclusionWith this retrospective analysis, it can be determined that the rate of reinfection of modular mega-endoprostheses on the hip and knee joint after healed periprosthetic joint infection (PJI) can be reduced by the use of silver coated implants. The time until reinfection can also be delayed by utilizing silver coated implants. Due to the low number of cases of this highly specific patient population, no statistical significance could be determined. A positive effect, however, can be assumed through the use of silver coatings in mega-endoprostheses after an infectious situation.

The modular endoprosthetic system Munich-Luebeck (MML) has been in clinical use since 1994. A total of 2.118 pelvic and lower extremity surgeries using the MML system were carried out up until 2010. The modular construction allows substituting or bridging any kind of bone defect. We analyzed 572 operative interventions, which were performed in 5 centers. The most frequent indications were tumors (50.3%) followed by revision arthroplasty due to loosening, periprosthetic fractures, and joint resection surgery due to infection (43.3%). Proximal and distal femoral replacement amounted to 78% of cases, whereas partial pelvic replacement accounted for 10.4% of the cases. Complications were reported in 27.27% of the cases, where dislocations (14.9% of the cases with simultaneous hip replacement) and infections (10.48%) were the most common, as expected. Revision surgery was necessary in 140 (24.8%) of the 572 patients, of which 68 were partial or total replacement of the implants, 16 removal of the implants and 10 above-knee amputations or rather exarticulations of the hip.