Effect of a Direct Thrombin Inhibitor Compared with Dalteparin and Unfractionated Heparin on Human Osteoblasts

Purpose:Osteoporosis is a relevant problem after long term administration of unfractionated heparin (UFH) and low molecular weight heparin. Melagatran is a representative of a new group of direct thrombin inhibitors with comparable data in the prevention of thromboembolic events after orthopaedic surgery. The aim of ourin vitrostudy was to investigate the effect of a direct thrombin inhibitor compared with dalteparin and UFH on human osteoblasts.Materials and Methods:Melagatran, dalteparin and UFH were added to primary osteoblast cultures in their therapeutic range and two decimal powers below and above. Cell number, protein synthesis, mitochondrial and alkaline phosphatase activity and collagen type I synthesis were evaluated.Results:Melagatran showed the least influence on protein synthesis and cell proliferation with a reduction of cell number to 83.5 ± 9% (p = 0.027) of the control group only in the highest investigated concentration after 15 days of incubation.Mitochondrial and alkaline phosphatase activity and collagen type I synthesis in osteoblasts incubated with melagatran and dalteparin showed similar patterns. UFH showed the most pronounced influence on cellular metabolism.Conclusions:Melagatran showed less inhibitory in vitro effects on human osteoblasts than dalteparin or UFH. The presented study gives first hints that direct thrombin inhibitors may help prevent heparin-induced negative effects on bone metabolism.</jats:sec

Patella Infera in an HIV Positive Patient Following Total Knee Arthroplasty

A lowering of the patella after total knee arthroplasty is accompanied by pain and a restriction of the range of motion. With its etiology being unclear at present, a multifactorial genesis is under discussion. For the first time, we present a case report describing an HIV infection as a possible cause of patella infera

CTLA-4 mediates inhibitory function of mesenchymal stem/stromal cells

Mesenchymal stem/stromal cells (MSCs) are stem cells of the connective tissue, possess a plastic phenotype, and are able to differentiate into various tissues. Besides their role in tissue regeneration, MSCs perform additional functions as a modulator or inhibitor of immune responses. Due to their pleiotropic function, MSCs have also gained therapeutic importance for the treatment of autoimmune diseases and for improving fracture healing and cartilage regeneration. However, the therapeutic/immunomodulatory mode of action of MSCs is largely unknown. Here, we describe that MSCs express the inhibitory receptor CTLA-4 (cytotoxic T lymphocyte antigen 4). We show that depending on the environmental conditions, MSCs express different isoforms of CTLA-4 with the secreted isoform (sCTLA-4) being the most abundant under hypoxic conditions. Furthermore, we demonstrate that the immunosuppressive function of MSCs is mediated mainly by the secretion of CTLA-4. These findings open new ways for treatment when tissue regeneration/fracture healing is difficult

Osteogenic Predifferentiation of Human Bone Marrow-Derived Stem Cells by Short-Term Mechanical Stimulation

It is commonly accepted that bone marrow-derived stem cells (BMSCs) have to be expanded in vitro, but a prolonged time in culture decreases their multilineage potential. Mechanical and biological stimuli have been used to improve their osteogenic potential. While long-term stimulation has been shown to improve osteogenic differentiation, it remains to be seen whether short-term stimulation is also sufficient

The bactericidal effect of vancomycin is not altered by tranexamic acid, adrenalin, dexamethasone, or lidocaine in vitro

One of the most challenging complications of total knee arthroplasty (TKA) is periprosthetic joint infection (PJI). There is growing evidence of a good anti-infective effect of intrawound vancomycin powder in total joint arthroplasty. At the same time, various different locally applied substances have become popular in total joint arthroplasty. The objective of this study was therefore to investigate a possible inhibition of the bactericidal effect of vancomycin by tranexamic acid, adrenalin, lidocaine, or dexamethasone. The bactericidal effect of vancomycin was quantified using the established method of the agar diffusion test. The plates were incubated with Staphylococcus aureus or Staphylococcus epidermidis and four wells were stamped out. The wells were filled with vancomycin alone, the tested substance alone or a mixture of the two. The fourth well remained empty as a control. The plates were incubated overnight at 37 °C and the zone of inhibition in each field was measured on the next day. All tests were run three times for each pathogen and mean values and standard deviations of the measurements were calculated. Differences between the substances were tested using the t-test at a level of significance of 0.05. The bacterial growth was homogeneous on all plates. The baseline value for the zone of inhibition of vancomycin was on average 6.2 ± 0.4 mm for Staphylococcus aureus and 12 ± 0.3 mm for Staphylococcus epidermidis . In all other substances, no inhibition was detected around the well. The combination of vancomycin and each other substance did not show any different result compared to vancomycin alone. The bactericidal effect of vancomycin on staphylococci is not altered by tranexamic acid, adrenalin, dexamethasone, or lidocaine in vitro

Plain radiographic indices are reliable indicators for quantitative bone mineral density in male and female patients before total hip arthroplasty

Abstract Osteoporosis is underdiagnosed in patients undergoing total hip arthroplasty (THA). Bone mineral density measurement by dual-energy X-ray absorptiometry (DXA) is the gold standard, but indices on plain hip radiographs also seemed to be reliable screening tools in female or Asian ethnicities in previous studies. Given the lack of knowledge about male patients and Caucasian ethnicities, this study was conducted to evaluate plane hip radiographic indices as a screening tool for osteopenia and osteoporosis in Caucasian female and also male patients before undergoing THA. A retrospective analysis of 216 elderly patients with pre-existing DXA before hip arthroplasty was performed and four indices were calculated on plain hip radiographs: Canal-Flare-Index (CFI), Canal-Calcar-Ratio (CCR), Canal-Bone-Ratio (CBR) 7 and 10 cm below the lesser trochanter. They were correlated with femoral neck DXA T-scores by Pearson’s correlation and intraclass correlation coefficient, and a ROC analysis was performed. A total of 216 patients (49.5% male) were included. CBR-7 and -10 were highly correlated (p < 0.001) with femoral neck T-score in males (Pearson’s correlation CBR-7 r = − 0.60, CBR-10 r = − 0.55) and females (r = − 0.74, r = − 0.77). CBR-7 and -10 also showed good diagnostic accuracy for osteoporosis in the ROC analysis in males (CBR-7: AUC = 0.75, threshold = 0.51; CBR-10: 0.63; 0.50) and females (CBR-7: AUC = 0.87, threshold = 0.55; CBR-10: 0.90; 0.54). Indices such as the Canal Bone Ratio (CBR) 7 or 10 cm below the lesser trochanter on plain hip radiographs are a good screening tool for osteopenia and osteoporosis on plain hip radiographs and can be used to initiate further diagnostics like the gold standard DXA. They differ between male and female patients

Defining the canal for ischial and pubic screws in cup revision surgery

Abstract Purpose When revising acetabular cups, it is often necessary to provide additional stabilisation with screws. In extensive defect situations, the placement of screws caudally in the ischium and/or pubis is biomechanically advantageous. Especially after multiple revision operations, the surgeon is confronted with a reduced bone stock and unclear or altered anatomy. In addition, screw placement caudally is associated with greater risk. Therefore, the present study aims to identify and define safe zones for the placement of caudal acetabular screws. Methods Forty-three complete CT datasets were used for the evaluation. Sixty-three distinctive 3D points representing bone landmark of interests were defined. The coordinates of these points were then used to calculate all the parameters. For simplified visualisation and intra-operative reproducibility, an analogue clock was used, with 12 o’clock indicating cranial and 6 o’clock caudal. Results A consistent accumulation was found at around 4.5 ± 0.3 hours for the ischium and 7.9 ± 0.3 hours for the pubic bone. Conclusions The anatomy of the ischium and pubis is sufficiently constant to allow the positioning of screws in a standardised way. The interindividual variation is low — regardless of gender — so that the values determined can be used to position screws safely in the ischium and pubis. The values determined can provide the surgeon with additional orientation intra-operatively when placing caudal acetabular screws

Impact of stem profile on the revisability and the need for osteotomy in well-fixed cemented revision total knee arthroplasty implants

Introduction: While re-revision total knee arthroplasty (ReRTKA) steadily increases, the ease and bone-sparing removal of RTKA implants is gaining more and more in importance. Biomechanical data suggest that cemented conical stems can be removed significantly easier than cylindrical stems. However, no clinical evidence exists supporting this observation. Aim of this study was to compare the revisability and need for osteotomy (OT) between removals of well-fixed cemented conical vs. cylindrical RTKA stems. Materials and methods: 55 removals of well-fixed full-cemented RTKA stems (29 knees) performed between 2016 and 2018 were retrospectively analyzed. Main outcome variables were: bone loss, fractures, osteotomy incidence, surgery duration, early postoperative complications (EPC), hemoglobin drop and blood transfusion. SPSS was used for the statistical analysis. Results: 44.8% were conical, 48.3% cylindrical, and 6.9% combined stem designs. Causes for re-revision were PJI (75.9%), malposition (17.2%) and persistent pain (6.9%). 10 stem removals (18.2%) required an OT (four femoral, six tibial): eight stems (14.5%) had cylindrical and two (3.6%) conical designs ( P  = 0.041). Fractures were noted solely in removals without OT (11.1% vs. 0%,). There was a tendency to more bone loss in cylindrical stem revisions (53.8% vs. 32%, P  = 0.24). A longer overall surgery time was observed in revisions of cylindrical stems (+ 37 min, P  = 0.05). There was higher hemoglobin drop and need for blood transfusion in revisions of cylindrical stems or after OT but without reaching statistical significance. The EPC rates were slightly higher in ReRTKA on cylindrical stems ( P  = 0.28). Conclusion: Well-fixed cemented conical stems may be revision friendlier with less demands on OT and shorter overall surgery time than cemented cylindrical stems

Impaction bone grafting for segmental acetabular defects: a biomechanical study

Abstract Introduction Implant loosening is the most common indication for revision after total hip arthroplasty and is associated with progressive bone destruction. Contained defects can be treated with impaction bone grafting (IBG). Segmental defects are successfully restored with metal augmentation. Considering the increasing number of hip arthroplasty cases in young patients, it would appear sensible to reconstruct the bone stock for future revisions by biological bone defect reduction. The data on the treatment of segmental defects with IBG without additional stabilization are lacking. Materials and methods Paprosky type IIB defects were milled into 15 porcine hemipelves with segmental defect angles of 40°, 80° and 120°. Contained defects without segmental defects (Paprosky type I) and acetabula without defects served as controls. After IBG, a cemented polyethylene cup (PE) was implanted in each case. Cup migration, rotational stiffness and maximum rupture torque were determined under physiological loading conditions after 2500 cycles. Results Compared with the control without defects, IBG cups showed an asymptotic migration of 0.26 mm ± 0.11 mm on average. This seating was not dependent on the size of the defect. The maximum rupture moment was also not dependent on the defect size for cups after IBG. In contrast, the torsional stiffness of cups with an 120° segmental defect angle was significantly lower than in the control group without defects. All other defects did not differ in torsional stiffness from the control without defects. Conclusions IBG did not show inferior biomechanical properties in segmental type IIB defect angles up to 80°, compared to cups without defects