Bone morphogenetic proteins − 7 and − 2 in the treatment of delayed osseous union secondary to bacterial osteitis in a rat model

Background: Bone infections due to trauma and subsequent delayed or impaired fracture healing represent a great challenge in orthopedics and trauma surgery. The prevalence of such bacterial infection-related types of delayed non-union is high in complex fractures, particularly in open fractures with additional extensive soft-tissue damage. The aim of this study was to establish a rat model of delayed osseous union secondary to bacterial osteitis and investigate the impact of rhBMP-7 and rhBMP-2 on fracture healing in the situation of an ongoing infection. Methods: After randomization to four groups 72 Sprague-Dawley rats underwent a transverse fracture of the midshaft tibia stabilized by intramedullary titanium K-wires. Three groups received an intramedullary inoculation with Staphylococcus aureus (103 colony-forming units) before stabilization and the group without bacteria inoculation served as healing control. After 5 weeks, a second surgery was performed with irrigation of the medullary canal and local rhBMP-7 and rhBMP-2 treatment whereas control group and infected control group received sterile saline. After further 5 weeks rats were sacrificed and underwent biomechanical testing to assess the mechanical stability of the fractured bone. Additional micro-CT analysis, histological, and histomorphometric analysis were done to evaluate bone consolidation or delayed union, respectively, and to quantify callus formation and the mineralized area of the callus. Results: Biomechanical testing showed a significantly higher fracture torque in the non-infected control group and the infected rhBMP-7- and rhBMP-2 group compared with the infected control group (p < 0.001). RhBMP-7 and rhBMP-2 groups did not show statistically significant differences (p = 0.57). Histological findings supported improved bone-healing after rhBMP treatment but quantitative micro-CT and histomorphometric results still showed significantly more hypertrophic callus tissue in all three infected groups compared to the non-infected group. Results from a semiquantitative bone-healing-score revealed best bone-healing in the non-infected control group. The expected chronic infection was confirmed in all infected groups. Conclusions: In delayed bone healing secondary to infection rhBMP treatment promotes bone healing with no significant differences in the healing efficacy of rhBMP-2 and rhBMP-7 being noted. Further new therapeutic bone substitutes should be analyzed with the present rat model for delayed osseous union secondary to bacterial osteitis

New methods for anechoic demixing with application to shift invariant feature extraction

Blind source separation problems emerge in many applications, where signals can be modeled as superpositions of multiple sources. Many popular applications of blind source separation are based on linear instantaneous mixture models. If specific invariance properties are known about the sources, e.g. translation or rotation invariance, the simple linear model can be extended by inclusion of the corresponding transformations. When the sources are invariant against translations (i.e. spatial displacements or time shifts) the resulting model is called anechoic mixing model. The main focus of this thesis is the development of new mathematical framework for the solution of the anechoic mixing problem and the successive derivation of concrete algorithms. This framework integrates approaches from many distinct fields of signal processing like stochastic time-frequency analysis, convex optimization, projection onto convex set methods, delay estimation and naturally blind source separation. The developed method is tested on a variety of applications including music recordings, natural two dimensional images, two-dimensional shapes and optic flow. However the main application is the analysis and synthesis of human motion trajectories, which is motivated by the idea in motor control that complex motor behavior can be explained by a superposition of simple basis components, or spatio-temporal primitives. The new anechoic demixing algorithm allows to approximate high-dimensional movement trajectories accurately based on a small number of learned primitives or source signals. It is demonstrated that the new method is significantly more accurate than other common techniques. This allows the modeling of subtle style changes, like the bodily expression of emotion as well as a sufficient synthesis quality for computer animation with only few mixture components

Blind

source separation for over-determined delayed mixture

Blind

source separation for over-determined delayed mixture