Der Einfluss von Knochenzement auf die Thrombozytenkonzentration bei Hüftgelenkersatz

Polymethylmethacrylate (PMMA) as bone cement is widely used in orthopaedic surgery with good clinical results. Thrombocytopenia has been described to occur after total hip arthroplasty (THA). It has been discussed in several in vitro studies whether the application of bone cement could be a possible origin for toxic agents that interfere with platelet function and survival. The aim of this study was to screen patient data for postoperative thrombocytopenia and the level of platelet concentrations in dependence of the fixation method of the THA. Although the fixation of implants using PMMA has been a very successful concept for the last decades, some side-effects have been observed. These include intraoperative cardiovascular reactions like hypotension (Powell, McGrath et al. 1970), arrhythmia (Schulitz, Koch et al. 1971) and even cardiac arrest (Powell, McGrath et al. 1970). There are many different theories about the cause of such reactions. Postoperative drops of platelet levels in peripheral blood are usually attributed to the intervention itself or to low molecular weight heparin, that is largely applied for prevention of deep vein thrombosis in THA (Bading, Blank et al. 1994). However, PMMA bone cement has been under suspicion to interfere with platelet function and survival in experimental in vitro studies. Cenni et al. found a significant decrease in platelet numbers for some PMMA cements (Cenni, Granchi et al. 2002). Gebauer et al. showed a significant increase. In this retrospective approach 499 consecutive THA were included. Of these, 123 (24.6%) patients received a fully cemented, 227 (45.5%) a partially cemented (stem cemented, sup uncemented) and 149 (29.9%) a fully cemented prosthesis. Refobacin Palacos R+G bone cement was used in all cemented procedures (Heraeus Kulzer, Wehrheim, Germany). The following data were collected from medical records: gender, age at time of operation, patients’ height and weight, body mass index (BMI), type of component fixation (cemented, partially cemented or uncemented), indication and duration of the operation. At the author’s institution, blood samples were taken on the day prior to surgery, the evening after THA, on the first postoperative day and the day before discharge: Sodium, potassium, calcium, alkaline phosphatase, lactate dehydrogenase, protein, leucocytes, erythrocytes, haemoglobin, haematocrit, MCH, MCV, MCHC, platelets, CRP, PT, aPTT and fibrin levels were recorded. Blood or fresh frozen plasma transfusions were recorded as well as anticoagulation regimens prior to THA. The null hypothesis was that there is no difference in platelet levels after THA between patients with cemented or uncemented technique at the day of operation. Analysis of demographics at index procedure showed significant differences between the two subgroups. This is mainly attributable to the fact that patients receiving an uncemented prosthesis were significantly younger. Also were the preoperative platelet concentrations significantly higher in the uncemented group. Correlation analysis revealed a significant connection between patient age and platelet count (r= -0.103, p<0.027), which means that Thrombocyte levels tend to be lower with higher age. There were no differences in between groups in postoperative platelet level drops as recorded the evening after THA. Student’s t-tests for independent variables delivered no statistically significant differences for the differences in platelet concentrations between groups at any point in time. The percentage of postoperative relative thrombocytopenia (<150.000/μl) was slightly higher in the cemented group and was mainly found in patients that had relatively low preoperative Thrombocyte levels. These differences were not statistically significant. From the data presented in this study it can be concluded that PMMA bone cement does not affect platelets at a clinically relevant dimension in THA.