The determination of the volumetric polyethylene wear on explanted material requires complicated equipment, which is not available in many research institutions. Our aim in this study was to present and validate a method that only requires a set of polyetheretherketone balls and a laboratory balance to determine wear. The insert to be measured was placed on a balance, and a ball of the appropriate diameter was inserted. The cavity remaining between the ball and insert caused by wear was filled with contrast medium and the weight of the contrast medium was recorded. The volume was calculated from the known density of the liquid. The precision, inter- and intraobserver reliability, were determined by four investigators on four days using nine inserts with specified wear (0.094 ml to 1.626 ml), and the intra-class correlation coefficient was calculated. The feasibility of using this method in routine clinical practice and the time required for measurement were tested on 84 explanted inserts by one investigator.Objectives
Methods
The utilization of sonicate fluid cultures (SFC) has been shown to increase the detection rate of periprosthetic joint infection (PJI) in comparison to the use of conventional microbiological methods, because sonication enables a sampling of the causative bacteria directly from the surface of the endoprosthetic components. The hypothesis of this study is that not only will the detection rate of PJI be improved, but also the detection rate of polymicrobial infection in patients with total knee arthroplasty (TKA) revision surgery. 74 patients which underwent TKA revision surgery received a synovial aspiration, intraoperative tissue cultures, histological sampling of the periprosthetic membrane, and sonication of the explanted endoprosthesis. A PJI was defined according to the following criteria: presence of intraarticular pus or a sinus tract, positive isolation of causative bacteria in ≥2 microbiological samples or a histological membrane indicative of infection (type II or III periprosthetic membrane).Introduction
Material and methods
Skeletal muscle injuries often lead to severe functional deficits. Mesenchymal stem cell (MSC) therapy is a promising but still experimental tool in the regeneration of muscle function after severe trauma. One of the most important questions, which has to be answered prior to a possible future clinical application is the ideal time of transplantation. Due to the initial inflammatory environment we hypothesized that a local injection of the cells immediately after injury would result in an inferior functional outcome compared to a delayed transplantation. Twenty-seven female Sprague Dawley rats were used for this study. Bone marrow was aspirated from both tibiae of each animal and autologous MSC cultures obtained from the material. The animals were separated into three groups (each n=9) and the left soleus muscles were bluntly crushed in a standardized manner. In group 1 2×106 MSCs were transplanted into the injured muscle immediately after trauma, whereas group 2 and 3 received an injection of saline. Another week later the left soleus muscles of the animals of group 2 were transplanted with the same number of MSCs. Group 1 and 3 received a sham treatment with the application of saline solution in an identical manner. In vivo functional muscle testing was performed four weeks after trauma to quantify muscle regeneration. Maximum contraction forces after twitch stimulation decreased to 39 ± 18 % of the non injured right control side after crush trauma of the soleus muscles as measured in group 3. Tetanic stimulation showed a reduction of the maximum contraction capacity of 72 ± 12 % of the value obtained from intact internal control muscles. The transplantation of 2 x 106 MSCs one week after trauma improved the functional regeneration of the injured muscles as displayed by significantly higher contraction forces in group 2 (twitch: p = 0.014, tetany: p = 0.018). Local transplantation of the same number of MSCs immediately after crush injury was able to enhance the regeneration process to a similar extent with an increase of maximum twitch contraction forces by 73.3 % (p = 0.006) and of maximum tetanic contraction forces by 49.6 % (p = 0.037) compared to the control group. The presented results underline the effectivity of MSC transplantation in the treatment of severe skeletal muscle injuries. The most surprising finding was that despite of the fundamental differences of the local environment into which MSCs had been transplanted, similar results could be obtained in respect to functional skeletal muscle regeneration. We assume that the effect of the MSC after immediate injection can partly be explained by their known immunomodulatory competences. The data of our study provide evidence for a large time window of MSC transplantation after muscle trauma.
The aim of this study was to establish an atrophic non-union model in the rat femur under well defined biomechanical conditions and with minimised interactions between the processes in the healing zone and the implant by using external fixation.
While significant component malalignment in the frontal and sagittal plane may lead to early loosening and pain, even small errors in the rotational component alignment are not tolerated due to its complex impact on knee joint kinematics and especially the patella tracking. It is accepted that navigated implantation of total knee arthroplasties improves accuracy in the frontal plane but it is yet unclear weather navigation leads to a more precise rotational component alignment. The study evaluated the influence of navigated implantation on femoral and tibial component alignment. In a prospective randomized study 32 navigated and 28 conventionally implanted total knee arthroplasties were evaluated through a postoperative CT scan. In all cases the femoral component was referenced to the surgical epicondylar axis and the tibial component was referenced to the medial third of the tibial tuberosity. The angles between these bone landmarks and the components were measured on the CT scans and compared between both study groups. The rotational malalignment of the femoral component in the conventional operating technique was 0.1° ± 2.2° (range 3.3° of internal rotation and 5.0° of external rotation). Navigated implanted femoral components showed a malalignment of 0.3° ± 1.4° (range 4.7° of internal rotation and 2.2° of external rotation), the difference was not significant. The rotational malalignment of the tibial component in the conventional technique was 7.5° ± 6.0° (range 27.1° of internal rotation and 15° of external rotation). Navigated implanted tibial components showed a malalignment of 6.9° ± 4.7° (range 21.2° internal rotation and 11.0° external rotation), the difference was not significant. In conclusion the use of a navigation system did not improve the rotational alignment of the tibial or femoral component if only one bone landmark was used. Taking the relatively small errors of a navigation machine into account the error is attributable to the surgeon, who seems to be unable to precisely define bone landmarks. More than one landmark (e.g. additionally Whiteside’s line, posterior condyles, flexion gap for the femur and ankle joint for the tibia) should be used to define the component rotations. Consideration of different rotational landmarks is best done with a navigation system that, in contrast to the manual technique, has the possibility to show the degree of deviation of the components from each landmark.
The development of iron oxide nanoparticles, which are taken up and endosomally stored by stem cells, allows the evaluation of cellular behaviour in the muscle with the use of magnetic resonance imaging (MRI). Previous work has shown that labelling does not affect the proliferation and neurogenic differentiation capacity of embryonic stem cells. In the present study we are currently investigating the in vivo distribution and migration of locally transplanted MSC after blunt muscle trauma in a rat model.
Despite all gain of knowledge, septic and aseptic loosening of endoprostheses still remain unsolved problems. In loosening of joint arthroplasty a periprosthetic membrane is found between the bone and the loosened implant. The characteristics of the membrane are influenced by the process that leads to the loosening of the endoprosthesis. The aim of the study was to introduce a classification system that enables a standardized diagnostic evaluation and helps to determine the aetiology of the loosening process. Based on histomorphological criteria and polarized light microscopy, four types of periprosthetic membranes were defined: periprosthetic membranes of the wear particle type (type I), periprosthetic membranes of the infectious type (type II), periprosthetic membranes of the combined type (type III), and periprosthetic membranes of the indifferent type (type IV). Periprosthetic membranes of 268 patients were analyzed according to the defined criteria. The interobserver reproducibility was sufficient (95%). The correlation between histopathological and microbiological diagnosis was high (89%, p<
0,001). The four types of periprosthetic membranes showed a significantly different time of revision. This classification system enables a standardized diagnostic procedure. It therefore is a basis for further studies concerning the etiology and pathogenesis of prosthesis loosening. The reliability of this histomorphological examination in diagnosing infections is currently reviewed.