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Establishment of drug delivery system (DDS) in bone substitute materials for local treatment of bone defects still requires ambitious solutions for a retarded drug release. We present two novel DDS, a weakly cationic dendritic glycopolymer and a cationic polyelectrolyte complex, composed of dendritic glycopolymer and cellulose sulfate, for the proteasome inhibitor bortezomib. Both DDS are able to induce short-term retarded release of bortezomib from calcium phosphate bone cement in comparison to a burst-release of the drug from bone cement alone. Different release parameters have been evaluated to get a first insight into the release mechanism from bone cements. In addition, biocompatibility of the calcium phosphate cement, modified with the new DDS was investigated using human mesenchymal stromal cells.

Bioresorbable implants may serve as an alternative option for the fixation of bone fractures. Because of their minor inherent mechanical properties and insufficient anchorage within bone bioresorbable implants have so far been limited to mechanically nondemanding fracture types. By briefly liquefying the surface of the biomaterial during insertion, bioresorbable implants can be ultrasonically fused with bone to improve their mechanical fixation. The objective of this study was to investigate the biomechanical fixation performance and in vivo biocompatibility of an ultrasonically fused bioresorbable polymeric pin (SonicPin). First, we biomechanically compared the fused pin with press fitted metallic and bioresorbable polymeric implants for quasi-static and fatigue strength under shear and tensile loading in a polyurethane foam model. Second, fused implants were inserted into cancellous bovine bone and tested biomechanically to verify the reproducibility of their fusion behavior. Finally, the fused pins were tested in a lapine model of femoral condyle osteotomies and were histologically examined by light and transmission electron microscopy. While comparable under static shear loads, fixation performance of ultrasonically fused pins was significantly (p = 0.001) stronger under tensile loading than press fit implants and showed no pull-out. Both bioresorbable implants withstood comparable fatigue shear strength, but less than the K-wire. In bovine bone the ultrasonic fusion process worked highly reproducible and provided consistent mechanical fixation. In vivo, the polymeric pin produced no notable foreign body reactions or resorption layers. Ultrasonic fusion of polymeric pins achieved adequate and consistent mechanical fixation with high reproducibility and exhibits good short-term resorption and biocompatibility.

Summary Although bone minerals have been widely studied by various techniques in previous studies, crystal structures, morphology of bone minerals and its building pathway remained still controversy. In this work, the ultrastructure of the mineralization front of rabbit femur has been studied by conventional and high-resolution (HR) transmission electron microscopy (TEM). In order to induce a healing and demineralization process the animals were subjected to a standardized osteotomy stabilized with titan screws and sonic pins. After 84 days follow-up time the newly build bone was investigated. The mineralization front of rabbit femur osteotomy contains partly mineralized collagen fibrils with a pronounced striped pattern together with a large number of agglomerated apatite platelets. The striation is caused by mineralization in the hole zones of the collagen fibrils, corresponding to the early stage of mineralization. In the TEM micrographs, the mineralization zone appears denser and compact when compared with fully mineralized bone, although most of the collagen fibrils are completely mineralized in the latter (higher concentration of interfibrillar apatite platelets within the mineralization zone). In bone some partly mineralized collagen fibrils are also observed, revealing the same arrangement, regular shape, and size of apatite platelets as collagen fibrils in the mineralization zone. Apatite platelets with irregular shapes are observed at the vortex-shaped outer boundary of the mineralization zone, i.e. at the interfaces with nonmineralized collagen or osteoblasts. HR TEM micrographs reveal that the platelets are assumably semicrystalline and that within the platelet nanocrystalline domains of apatite are embedded in an amorphous calciumphosphate matrix. SCANNING 35: 169-182, 2013. © 2012 Wiley Periodicals, Inc.

Polymethylmethacrylate (PMMA) is the most commonly used bone void filler for vertebral augmentation in osteoporotic fracture. It provides mechanical stability and immediate pain relief; however, PMMA is not osteointegrated and is separated from the surrounding bone tissue by a thin fibrous layer. The aim of this study was to investigate the effect of nanocrystalline hydroxyapatite (HA) on osteointegration of PMMA in a sheep model. A composite material, consisting of PMMA and nanocrystalline HA (70:30, v/v), was implanted in one distal femur, with pure PMMA in the other femur as a control. Three and 6 months after implantation, the distal femora were histologically investigated. All composite implants exhibited a tight junction to the surrounding bone tissue, with minimal bone ingrowth into the outer surface of the implant. In comparison, with use of the control implants, we observed an overall bone resorption around pure PMMA, with fibrous connective tissue encapsulating the implant. These results suggest that nanocrystalline HA enables osteointegration of PMMA in bone tissue, which might alter the biomechanical characteristics of the osteoporotic vertebral body after augmentation.

To have knowledge of the physiological closure of a particular physeal plate is necessary to understand fractures close to the end of growth (transitional fractures). Most frequent fractures involve the distal radius in adolescents. However, there are no systematic investigations on the topic of growth plate closure concerning the distal radius plate, so far. Twenty-two healthy female volunteers underwent MRI investigations of their left wrist. Absolute width, percentage and localization of the physeal part, closed at the time of investigation were recorded. Sequential MRI scans were performed. In this series T1-weighted sequences were most useful to distinguish open and closed parts of the physis. Total area was 291-469 mm(2) (average, 399 mm(2) ). It did positively correlate with body height (P < 0.01), but not with weight (P = 0.241) or BMI (P = 0.394). Physeal closure took place at 15-18 years. There was no significant correlation between menarche and closure (P = 0.091). Bony bridging of the growth plate begins centroradial and ends with a small limbus dorsoradial. Sequential scans showed that there are only a few months from beginning to end of physeal closure. Physiological closure of the distal radius growth plate takes place in late adolescence, varying individually. There seems to be no influence of the menarche in female individuals. The process happens within a very short time of less than a year. This may be one rationale for the fact, that transitional fractures of the distal radius are rare.

Bone gluing is an attractive surgical technique; however, its use in patients is hampered by a variety of side effects. Therefore, it was the aim of this ethically approved study to evaluate a novel biodegradable β-Tri-Calciumphosphate (β-TCP, Cerasorb®)-enhanced bone adhesive regarding its toxicity and biocompatibility in a rabbit model. Fifty healthy New Zealand White rabbits were assigned in the study (n = 21) and sham-operated control group (n = 29). In the study group, a cylindrical part (4.6 × 10.0 mm) of the proximal tibia and distal femur was removed, reimplanted, and bone adhesive was applied. Blinded physical examination and sampling for hematology, clinical chemistry, and acute phase proteins (haptoglobin, C-reactive protein (CRP)) was performed before surgery and after 12, 24, 48, 72, 240, and 504 h. Significant findings of the physical examination included a slightly higher grading of warmth (p = 0.0019) and pain (p < 0.0001) of the wound 240 h after surgery in the study group. No significant differences between albumin, haptoglobin, CRP, and urea concentrations in both groups were evident, whereas the study group demonstrated significantly lower leukocyte count, total protein, and globulin concentrations (p < 0.0001). As expected, both groups showed a marked transient increase in muscle enzymes (Creatine Kinase and Aspartate Aminotransferase) following the surgery (p < 0.0001). Twelve to 24 h after surgery, a significant decrease in ionized calcium from 1.38 ± 0.12 mmol/L to 1.06 ± 0.13 mmol/L was noted in the study group (p < 0.0001). The results clearly indicated that the novel β-TCP-enhanced bone adhesive showed good biocompatibility without significant evidence of acute or subacute local or systemic toxicity. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009

Management of bone and soft tissue infections generally includes surgical procedures as well as attendant treatment and prevention with gentamicin-loaded fleeces. Conventional gentamicin-containing collagen fleeces currently in use are strongly acidic and exhibit limited biocompatibility thereby adversely affecting wound healing. To improve the antibiotic delivery system, a new phosphate-buffered, gentamicin-loaded fleece with pH–neutral properties has been developed (Jason G®). This study aimed at comparing the elution kinetics of gentamicin release and the antimicrobial efficacy of conventional fleeces with the newly developed fleece in vitro. In addition, degradation and microvasculature of implanted fleeces were examined in a rat model and assessed using histology, as well as detection of ED-1 and PECAM-expression using immunohistochemistry. We show that the phosphate-buffered fleeces have reduced release (p < 0.05) of the integrated gentamicin. However, all of the fleeces tested had a significant antimicrobial effect on the growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa strains (p < 0.01). Among the fleeces tested, the new Jason G® fleece had the weakest but nevertheless sufficient antimicrobial effectiveness. Evaluation of the antibiotic effect in the prevention of an infection showed no differences between the applied fleeces. Following surgical implantation of fleece in the backs of Wistar rats we observed, on day 5 after implantation, an increase in cell infiltration and microvascularization with the phosphate-buffered fleece as compared with conventional fleeces, which show necrotic cells on their surface. Unlike the acidic fleeces, on day 15 after implantation the pH–neutral fleece was resorbed widely. Here, we show that the new, pH–neutral, gentamicin-containing fleece Jason G® exhibits good overall antimicrobial effectiveness against both gram-positive and gram-negative bacteria in vitro with improved degradation properties and microvasculature formation in vivo. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009

The combination of hydroxyapatite (HA) implants serving as osteoconductive scaffold with growth factors is an interesting approach for the improvement of bone defect healing. The purpose of this study was to test whether recombinant human bone morphogenetic protein-2 (rhBMP-2) coating of solid HA-implants improves bone formation in a cortical bone defect. Cylindrical trephine mill defects (diameter: 9.8 mm, depth: 10 mm) were created into the cortical tibia shaft of minipigs and subsequently filled either by plain HA cylinders (Endobon®) or by rhBMP-2-coated HA cylinders. Fluorochrome labeling for the evaluation of time-dependent bone formation was done on days 8, 9, and 10 postsurgery with tetracyclin-100, at days 25 and 30 with alizarin-komplexon, and finally on days 32, 37, 73, and 79 with calcein green. Twelve weeks after implantation, the tibiae were harvested and were prepared for standard histological staining, fluorochrome analysis, and histomorphometry. Coating of HA implants with rhBMP-2 led to significant enhanced new bone formation of 84.7% (±4.6%) of the implant area with almost complete bony incorporation compared with only 27.7% (±8.5%) in the uncoated HA implants (p = 0.028). In both types of implants, osteoconduction of HA led to bone ingrowth of the surrounding host bone into the implants. However, only rhBMP-2-coated implants showed multitopic de novo bone formation reflecting the osteoinductive properties of rhBMP-2 in all areas of the HA implant. This study showed that the coating of HA ceramic implants with rhBMP-2 can significantly enhance new bone formation attributable to its osteoinductive effects. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009

In this work, a novel bioresorbable bone adhesive based on radically polymerizable polylactide with methacrylate endgroups known from polymethylmethacrylate (PMMA) cements and varying amounts of bioresorbable/biodegradable lactide moieties was developed. The swelling and degradation properties as well as the hardening time, viscosity, and adhesion properties (tension and shear resistance) were subsequently measured in vitro and optimized. For a broad use in surgery the handling properties, the shelf life and the storage temperature are important issues. The finally developed material consists of three substances that have to be mixed to start the reaction: a highly viscous mixture of oligomers and two β-tricalcium phosphate (β-TCP, Cerasorb®) powders with the radical starter and the promoter. The material has a processing time of 2 min and is completely cured after another minute. The tension and shear resistance of the material is 3.1–13.9 MPa that will decrease by storing the substance in a humid atmosphere. Degradation experiments showed a mass loss of 20–35% during the first 5 weeks. Tests with MC3T3-E1 cells showed an increase of the alkaline phosphatase activity over a period of 14 days. The mechanical and handling properties and the in vitro data are showing a promising biomaterial for bone regeneration. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009

We report the case of an isolated cuboid bone fracture in a child that was missed on radiography but was diagnosed on sonography. Plain radiographs of the patient's right foot showed no fracture, whereas sonograms demonstrated a fracture of the cuboid bone that appeared as a steplike discontinuity in the cortical bone. The diagnosis was confirmed on MRI. The fracture was treated with cast immobilization and no weight bearing for 4 weeks. In 8 weeks, the patient had no symptoms and good motor and sensory function of her right foot. Other imaging modalities are usually advocated for diagnosing fractures that are missed by radiography. Over the last decade, sonography has been increasingly used for diagnosing occult fractures. Although its use in such cases is not yet fully established, we believe that in the future, the sonographic detection of an injury that corresponds to the site of the reported pain will be adequate for initiating treatment of many types of fractures.

In the present study the in vivo mechanism of calcium-phosphate (CaP) ceramic degradation has been investigated by means of transmission electron microscopy. The results revealed osteoclast-mediated degradation of hydroxyapatite ceramic implanted into sheep bone by simultaneous resorption and phagocytosis. After 6 weeks of implantation, osteoclasts were localized immediately beneath the ceramic surface. They had formed resorption lacunae and exhibited typical ultrastructural features, such as the ruffled border, the clear zone, and the dorsal microvilli. Their resorption capacity also had become evident by alterations of the electron density and the shape of the CaP crystals localized within the acidic microenvironment of the ruffled border. Moreover, the osteoclasts simultaneously were capable of phagocytosing the resorbed CaP crystals. The formation of endophagosomes was performed (1) by the uptake of particles into large intracellular vacuoles, which were generated by deep invagination of the membranes of the osteoclastic ruffled border, and (2) by the encircling of particles due to the development of pseudopodia-like plasmaprotrusions of the ruffled border. The formation of endophagosomes was followed by the in situ fragmentation of the inclusion material, which subsequently was released into the extracellular space and phagocytosed by macrophages.

Implant-related infections are often devastating situations in orthopaedic trauma surgery particularly if multiresistant bacteria are involved. Protection of the implant surface by an antimicrobial coating exhibiting activity against multiresistant bacterial strains is of high interest. Aim of this study was to investigate the antimicrobial effects of an Ag/SiO(x)C(y) plasma polymer coating for fracture fixation devices, such as nails, plates, and external fixators, including tests against methicillin-resistant Staphylococcus aureus (MRSA) and its biocompatibility. The antimicrobial activity of the coating deposited onto 12 x 3 mm(2) stainless steel implants was tested in vitro against Staphylococcus aureus, Staphylococcus epidermidis, and MRSA using different testing methods (ASTM E-2810, JIS Z 2801, proliferation assay). Additionally, the coated devices were implanted into the paravertebral muscle of rabbits and explanted after 2, 7, 14, and 28 days to test the remaining ex vivo antimicrobial activity. For biocompatibility assessment the Ag/SiO(x)C(y) plasma polymer coating was tested in vitro according to ISO 10993-5. The Ag/SiO(x)C(y) coating exhibited excellent antimicrobial activity against all tested bacterial strains in all three in vitro tests. Ex vivo testing proved suppression of more than 99.9 % of bacterial proliferation by the coating compared to non-coated samples even after 28 days. ISO 10993-5 showed good biocompatibility of the coating without any indications of cytotoxic effects. In summary, Ag/SiO(x)C(y) plasma polymer coating showed excellent antimicrobial activity including effectiveness against MRSA and good in vitro biocompatibility. Therefore, it possesses high potential as a prophylactic agent in orthopaedic trauma surgery.