The uncertainty of the biological effects of wear and corrosion from Metal-on-metal (MoM) implants has initiated a debate on their safety and use. Generally, the release of wear particles from MoM hip implants can clinically manifest in aseptic osteolysis. In our study, the effect of MoM-wear particles and particle originated Co and Cr ions on mesenchymal stromal cells (MSCs) was investigated [1]. The lead hypotheses were that (1) dissociated Co and Cr, originated from MoM-wear particles, accumulate in the bone marrow and (2) apparently impair the osteogenic function of local MSCs. This impairment could be one element contributing to the manifestation of periprosthetic osteolyses. The study was approved by the local ethical committee (EA1/194/13); all donors gave written informed consent. Blood (B), Synovial fluid (SF) periprosthetic tissue (PT) and bone marrow (BM) were collected from patients with at least one osteolytic lesion, undergoing a revision of a MoM hip implant. Patients undergoing primary THA served as controls. Metal wear particles were isolated from PT by enzymatic digestion and their size and shape characterized by transmission electron microscopy (TEM). Local and systemic levels of Co and Cr were analyzed by graphite furnace atomic absorption spectroscopy. MoM-MSCs and control-MSCs were isolated from BM for INTRODUCTION
METHODS
Despite the lack of data regarding the diagnostic validity of synovial aspiration in Girdlestone hips a Girdlestone-aspiration is often performed before reimplantation to detect a possible persistence of infection during two staged revision total hip arthroplasty (THA). The aim of this study was to assess the diagnostic performance of the synovial aspiration in Girdlestone hips, without a PMMA-Spacer, for the detection of infection persistence prior to THA reimplantation. Seventy four patients undergoing a two staged revision THA surgery between 2006 and 2013 were included in this retrospective cohort study. Both synovial cultures and CRP values were acquired before explantation of the THA and of the Girdlestone hip before reimplantation. An antibiotic holiday of 14 days was observed prior to synovial aspiration. A PJI was defined according to the following criteria: intraarticular presence of pus or a sinus tract, a periprosthetic membrane indicative of infection in the histological analysis, or a positive microbiological isolation in a minimum of two samples.Introduction
Methods
The efficacy of tranexamic acid (TXA) to reduce blood loss in various surgical procedures has been proven. However, there is little data about the effect of TXA on blood loss, rate of blood transfusion and thromboembolic events during periacetabular osteotomy (PAO). The reduction of blood loss during PAO promotes postoperative mobilization and reduces the risk of complications, associated with blood transfusions. The aim of the following study was to determine, if TXA can reduce both blood loss and the rate of blood transfusions. In addition we analyzed whether TXA was associated with an increased risk of thromboembolic events. A consecutive series of 96 PAO procedures was reviewed to compare the groups immediately prior to and following the routine implementation of TXA. The TXA group received a continuous infusion of TXA with a rate of 10mg/kg/h. The outcome was blood transfusion rate, total blood loss, length of hospital stay, and thromboembolic events.INTRODUCTION
METHODS
The main reasons for hip prosthesis failure are aseptic loosening and periprosthetic joint infection (PJI). The real frequency of PJI is probably largely underestimated because of non-standardized definition criteria, diagnostic procedure, treatment algorithm and other confounders. Therefore, data from joint registries are not reflecting the frequency of PJI and can be misleading; particularly low-grade PJI can be frequently misdiagnosed as aseptic failure. Therefore, prospective clinical studies with standardized protocol, comprehensive diagnostic procedure and sufficient follow-up should be performed. Sonication of explanted prosthesis is highly sensitive for detection of biofilms on prosthetic surface and allows quantitative analysis of biofilm formation. We hypothesize that by using sonication, ceramic components (BIOLOX®delta, BIOLOX®forte) will show higher resistance against biofilm adhesion compared to polyethylene (PE) and metal (CoCrMo). In this prospective multicentre study (level of evidence: Ia), we included all consecutive adults ≥18 years of age, who underwent explantation of the hip prosthesis for infection or aseptic reason. Excluded were patients in whom part of the prosthetic components were retained. A standardized and comprehensive diagnostic algorithm was applied, including sonication of all removed prosthetic components for qualitative and quantitative microbiological analysis (ultrasound bath 40 kHz, 1 W/cm2, 1 min). Individual components (metal, PE, ceramic) were separately placed in sterile boxes for investigation. All patients were simultaneously included in the European Prosthetic joint infection cohort (EPJIC, Background
Methods
A timely isolation of the causative bacterial species is of paramount importance in the treatment of periprosthetic joint infection (PJI). Sonication of the explanted endoprosthesis and the microbiological culture of sonicate fluid (SFC) has been proven to increase the rate of bacterial isolations in comparison to the conventional microbiological methods. The cultivation of aspired synovial fluid in blood culture bottles (BCB) has been shown to yield a higher rate of bacterial isolations and produce a lower rate of contaminants than cultivation on conventional agar plates. The primary aim of this study was to investigate whether the inoculation of BCB with sonicate fluid leads to a higher rate of bacterial isolations than the culture on agar plates. Secondly, we wanted to investigate whether the utilization of BCB leads to an earlier identification of the causative bacterial species. To our knowledge this is the first study to investigate the effects of BCB use on SFC. We performed a retrospective analysis comparing the results of the two different culture methods. To detect slow growing species all microbiological cultures, regardless of the culture method, were incubated for 14 days.Introduction
Methods
The leading cause for total hip arthroplasty (THA) revision remains aseptic loosening due to bearing wear. The younger and more active patients currently undergoing arthroplasty present unprecedented demands on THA-bearings. Ceramic-on-ceramic (CoC) bearings have consistently shown the lowest wear rates. The recent advances, especially in alumina CoC bearings, have solved many past problems and produced preferable results in vitro. Alumina ceramics are extremely hard, scratch resistant, biocompatible, offer a low coefficient of friction, superior lubrication and lower wear rates in comparison to other bearings in THA. The major disadvantage of ceramics used to be fracture. The new generation of alumina ceramics, has reduced the risk of ball fracture to 0.03–0.05%. The risk for liner fracture is even lower. Assuming an impingement-free component implantation, CoC bearings have major advantages over other bearing combinations. Due to the superior hardness, CoC bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A complication specific to CoC bearings is squeaking. Squeaking occurs if the friction in the joint articulation is sufficient to excite vibrations to audible magnitudes (due to loss of lubrication). The high range of reported squeaking (0.45% to 10.7%) highlights the importance of correct implant position. If a correct implant position can be guaranteed, then squeaking is rare and without clinical significance. The improved tribology and presumable resulting implant longevity make CoC the bearing of choice for young and active patients. Especially the alumina matrix (Biolox delta) offers increased burst strength and greater fracture toughness.
The endoprosthetic treatment of secondary osteoarthritis resulting from congenital hip dysplasia is difficult due to the small diameter of the acetabulum and the hypoplastic anterolateral bone stock. On the femoral side the increased femoral anteversion, insufficient femoral offset and proximal femoral deformities (mostly valgus deformities) as well as the small diameter and straight form of the intramedullary canal pose challenges. Careful preoperative planning is mandatory. The Crowe classification is usually used to describe these pathologies. In severe cases (Crowe 3 and especially Crowe 4) a shortening and derotating femoral osteotomy should be taken into account. Small acetabular components, acetabular augments, and modular femoral components must be available at all times. For acetabular fixation press-fit cups are preferred today, but excellent results were also described for threaded cups. The advantage of press-fit cups is the extensively documented and superior track record, but threaded cups allow for an easier reconstruction of the original hip center as well as slight medialization. As a result of medialization a reduction in polyethylene wear together with a low rate of loosening lead to very good long-term results in a younger patient population. Cementless straight stems are documented to be preferable for the small femoral diameter and the straight anatomic shape of the proximal femur. Nevertheless, the higher complication rate, especially the increased rate of nerve palsies, should be preoperatively discussed with the patient. The ideal bearing surface is currently unclear, ceramic-on-ceramic seems to be promising, although the longest data available support the use of metal-on-polyethylene.
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
Acetabular retroversion has been implicated as a risk factor for the development of early hip osteoarthritis. In clinical practice standard osseous signs such as the cross-over sign (COS) and the posterior wall sign (PWS) are widely used to establish the diagnosis of acetabular retroversion on plain radiographs. Despite standardized radiological evaluation protocols, an increased pelvic tilt can lead to a misdiagnosis of acetabular retroversion in AP radiographs and 2D MR or CT scans. Previous studies have shown that the elimination of observer bias using a standardized methodology based on 3D-CT models and the anterior pelvic plane (APP) for the assessment of COS and PWS results in greater diagnostic accuracy. Using this method a prevalence of 28% for COS and 24% for PWS has been found in a cohort of patients with symptoms indicative of FAI, however the prevalence of both signs in asymptomatic adults remains unknown. This study therefore sought to establish the prevalence of the COS and PWS in relation to the APP in an asymptomatic population using a reliable and accurate 3 D-CT based assessment. A large pool of consecutive CT scans of the pelvis undertaken in our department for conditions unrelated to disorders of the hip was available for analysis. Scans in subjects with a Harris hip score of less than 90 points were excluded leaving a sample of 100 asymptomatic subjects (200 hips) for this study. A previously established 3D analysis method designed to eliminate errors resulting from variations in the position and orientation of the pelvis during CT imaging was applied to determine in order to assess the prevalence of the COS and PWS in relation to the APP. Here, the acetabuli were defined as retroverted if either the COS, PWS or both were positive.INTRODUCTION:
METHODS:
Sonicate fluid cultures (SFC) are more sensitive than conventional microbiological methods in identifying periprosthetic joint infections (PJI), because sonication enables a sampling of the causative bacteria directly from the surface of the endoprosthetic components. Because of their high sensitivity SFC can be positive while all other microbiological methods remain negative. It is therefore difficult to interpret a single SFC as being truly or falsely positive. The aim of this prospective study was to improve the interpretation of SFC in the diagnosis of PJI in patients after total hip arthroplasty through the use of multiple SFC. 102 patients of which 37 had a defined PJI according to the following criteria were included: intraarticular pus or a sinus tract, a periprosthetic membrane (PM) indicative of infection, or a positive microbiological culture in a minimum of 2 separate microbiological samples. A single positive microbiological sample was classified as false positive. In 35 patients multiple SFC were acquired from the separate endoprosthetic components.Introduction
Material and methods
Head sizes used in total hip arthroplasty (THA) has increased drastically from the original 22mm used by Charnley. This is due to two factors: the use of hard-on-hard materials for the bearing articulation and the increasing problem of dislocation. Hard-on-hard materials enable mixed or fluid film lubrication due to their good wettability. The development of a fluid film layer is encouraged by smaller surface pressures (larger area) and higher velocity at the articulating interface (larger radius), suggesting that larger diameters exhibit better lubrication and such less wear. This was effectivly proven in pre-clinical simulator studies and used as argument to increase the diameters of metal-on-metall and ceramic-on-ceramic bearings. Clinically the tribological advantage of larger diameters has not yet been shown. For hard-on-soft bearings the situation is different. Due to the bad wettability of Polyethylene (PE), the abrasive wear regime is dominant. This means that the longer wear path of a larger diameter will inevitably carry a larger amount of wear debris. Despite this relation, the heads used in combination with PE were also increased up to 40mm diameter, justified by the overall greatly reduced wear amount of the new generation(s) of cross-linked PE and favourable simulator results. First in-vivo studies have shown that larger heads carry larger amounts of wear particles. Whether this increase is relevant with respect to osteolysis is still unclear and will have to be shown in longer term studies. Larger heads require a larger “jumping” distance until they dislocate. Consequently the use of larger heads reduces dislocation rates, which was shown in multiple clinical studies. However, the reduction in dislocation rate achieved by increasing diameters varies greatly. Some centres achieve dislocation rates below 1% with 28mm heads, other centres require 36mm heads to achieve the same result. No study shows any further advantage with head diameters larger than 36mm. Despite their obvious biomechanical advantage with regard to stability, larger heads also have large disadvantages. Larger heads carry inevitably larger friction moments, requiring better anchoring of the components. In unfavourable conditions (start-up, break-down of lubrication film), friction moments of hard-on-hard bearings can get very high and reach or even exceed the losening torque of the head on the taper. Depending on the head impaction foce during assembly, the loosening torques amount to 8 to 17Nm. Movement at the head-taper connection possibly causes wear and increased corrosion at this interface. Larger head diameters also require thinner shells and/or liners, leading to problems with liner chipping or incomplete seating. Large head diameters have also lead to the use of sub-hemispherical cups with reduced covering surface, increasing the risk of fluid film break down due to edge loading if not well positioned. Finally, larger heads might give the surgeon a wrong feeling of security regarding a sub-optimal positioned cup. The question regarding “the optimal” head diameter is open for discussion and needs to consider the bearing material used. Head size should be limited to a reasonable compromise, which based on the information currently available, could be 36mm. Join the “36 and under” club.The tribological aspect
The biomechanical aspect
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.
Total hip arthroplasty is a challenging problem in case of high hip dislocation. In order to reduce the hip, a femoral shortening osteotomy is necessary to prevent damage to the neurovascular structures. In this study we present the mid-term results of a simple technique of simultaneous derotating and shortening osteotomy of the femur without the necessity of additional osteosynthesis. In this retrospective study we included 28 patients with high hip dislocation. In these patients 30 consecutive cementless primary total hip arthroplasties with femoral shortening osteotomy were performed. 20 cases were previously operated. All patients were clinically and radiologically followed up after a mean of 4.5 years (range 2 – 5.7 years). Time point of consolidation was determined on consecutive radiographs for each patient. The average operative time was 116 minutes (range 65 to 150 minutes). There were no intraoperative complications. Postoperatively no femur fractures, no pseudarthroses and no pareses were observed. The mean consolidation time of the osteotomy was 4.4 months. At the time of follow-up, one aseptic loosening had been verified. In this case a very small stem (size 03) had been used. The mean Merle d’Aubigne score for the unrevised hips improved from 8.2 points preoperatively to 15.1 points at follow-up. In conclusion the presented technique allowed an easy and fast implantation of total hip arthroplasty in patients with high hip dislocation. The Zweymueller stem design with its rectangular cross-section seems responsible for the sufficient stability of the osteotomy resulting in a short consolidation time. Any additional osteosynthesis is obsolete. This leads to additional advantages including a short duration of surgery and a low complication rate. The good clinical results are attributable to the fact, that by shortening the femur, the physiological hip joint biomechanics could be approximated. The mid-term results of the described technique are very promising.
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.