No description available.

No description available.

The high incidence of long bone fractures and appreciable rate of delayed and non-union (5-10%) necessitates the development of non-invasive tools to monitor healing progression. The objective of this study was to develop a novel µCT-based measure of three-dimensional bone connectivity and to compare its ability to assess fracture callus mechanical stability to previously described measures. Bone connectivity parameters local to the failure surface were found to significantly correlate with mechanical stability, and proved superior to previously developed measures of torsional rigidity. Visualization of the failure surfaces demonstrated a consistent failure pattern indicative of the applied torsional loading, however the locations of the failure surfaces showed varying levels of fracture callus involvement. The results of this proof of concept work indicate the potential utility of bone connectivity analysis in non-invasive assessment of fracture callus stability.

The high incidence of long bone fractures and appreciable rate of delayed and non-union (5-10%) necessitates the development of non-invasive tools to monitor healing progression. The objective of this study was to develop a novel µCT-based measure of three-dimensional bone connectivity and to compare its ability to assess fracture callus mechanical stability to previously described measures. Bone connectivity parameters local to the failure surface were found to significantly correlate with mechanical stability, and proved superior to previously developed measures of torsional rigidity. Visualization of the failure surfaces demonstrated a consistent failure pattern indicative of the applied torsional loading, however the locations of the failure surfaces showed varying levels of fracture callus involvement. The results of this proof of concept work indicate the potential utility of bone connectivity analysis in non-invasive assessment of fracture callus stability.

The mechanics applied to healing fractures vary widely. At one extreme rigid internal fixation is advocated, while at the other early mobilisation is recommended using external splints. Kuhn's method of paradigm orientated research was used to define the historical context of current assumptions regarding fracture healing. Conflict between the various schools of thought is the main evidence for failure of these assumptions and the need to evolve a new perspective on fracture healing. A paradigm is presented which proposes healing by external callus as an early stage and 'primary healing' as the later stage as of one continuous but changing process. A fundamental hypothesis was tested: that mechanics is the major control of fracture healing in man. A multicentre study of 102 patients with serious fractures were treated with external skeletal fixation. In 60 patients rigid external fixation was applied. In the remaining 42 the same fixation device was used, but adapted to apply 1 to 2mm of cyclic axial micromovement across the fracture. A piston applied 500 cycles of movement over a 30 minute period each day until this could be achieved by the patient on weight-bearing. Objective assessment required development of new techniques of measuring fracture stiffness and defining the point of healing. This objective measure, and clinically defined healing, were significantly faster in the group treated with micromovement (two-way analysis of variance, p = 0.005 and 0.03, respectively). Repeated injury by plastic deformation is proposed to maintain callus growth in the first phase of healing. Evidence for the required parameters of movement was gathered from the trial of micromovement, from measurements in 4 cases of epiphyseolysis and also 8 patients undergoing arthrodesis. It would appear appropriate to apply cyclic axial displacement of 2mm within the first two weeks from injury and of consistent direction until sufficient bulk of callus is formed. Thereafter axial compaction is appropriate in a second phase where callus matures. The mechanics that govern remodelling were considered to apply to the final phase. Failure of a cell culture model to display obvious results from cyclic loading may indicate that the response to mechanical loading is indirect. Intermediate and mechanically dependent biochemical and bioelectrical factors are discussed.

No description available.

No description available.

No description available.

by Chong Wai Sing, Wilson. / Thesis submitted in: August 2002. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 116-126). / Abstracts in English and Chinese. / ACKNOWLEDGEMENT --- p.i / ABBREVIATION --- p.ii / ABSTRACT (Chinese & English) --- p.iii / TABLE OF CONTENT --- p.vii / INDEX FOR FIGURES --- p.x / INDEX FOR TABLES --- p.xiii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- "Bone-tendon junction - types, structures and functions" --- p.2 / Chapter 1.1.1 --- Indirect insertion --- p.3 / Chapter 1.1.2 --- Direct insertion --- p.3 / Chapter 1.1.3 --- Functional adaptations of insertions --- p.4 / Chapter 1.2 --- Incidence and type of injuries near insertion site --- p.5 / Chapter 1.3 --- Treatment protocol for injuries near insertion site --- p.5 / Chapter 1.3.1 --- Non-operative versus operative approach --- p.5 / Chapter 1.3.2 --- Previous studies on validations of outcomes of difference repair methods --- p.6 / Chapter 1.4 --- Modes of healing underlying different repair approach --- p.7 / Chapter 1.4.1 --- Fracture healing --- p.7 / Chapter 1.4.2 --- Tendon healing --- p.8 / Chapter 1.4.3 --- Bone-tendon healing --- p.9 / Chapter 1.5 --- Objectives --- p.9 / Chapter 2. --- Materials and Methods --- p.12 / Chapter 2.1 --- Animal model --- p.13 / Chapter 2.2 --- Experimental design --- p.13 / Chapter 2.3 --- Surgery --- p.13 / Chapter 2.3.1 --- Bone-to-bone repair --- p.14 / Chapter 2.3.2 --- Bone-to-tendon repair --- p.14 / Chapter 2.3.3 --- Tendon-to-tendon repair --- p.15 / Chapter 2.4 --- Post-operative follow-up --- p.15 / Chapter 2.4.1 --- Radiographic examination --- p.15 / Chapter 2.4.2 --- Polychrome sequential labeling --- p.16 / Chapter 2.4.2.1 --- Reagents --- p.16 / Chapter 2.4.2.2 --- Route of administration --- p.16 / Chapter 2.5 --- Sampling --- p.17 / Chapter 2.6 --- Histology --- p.17 / Chapter 2.6.1 --- Decalcification --- p.17 / Chapter 2.6.1.1 --- Tissue decalcification --- p.17 / Chapter 2.6.1.2 --- Tissue processing --- p.17 / Chapter 2.6.1.3 --- Immunohistochemistry of collagen type II and III --- p.18 / Chapter 2.6.1.3.1 --- Reagents and solution preparation --- p.18 / Chapter 2.6.1.3.2 --- Experimental procedures --- p.20 / Chapter 2.6.2 --- Undecalcification --- p.22 / Chapter 2.6.2.1 --- Specimen preparations --- p.22 / Chapter 2.6.2.2 --- Toluidine blue staining --- p.22 / Chapter 2.7 --- Mechanical test --- p.23 / Chapter 2.7.1 --- Sample preparation --- p.23 / Chapter 2.7.2 --- Embedding procedures --- p.23 / Chapter 2.7.3 --- Measurement of cross-sectional area of healing interface --- p.23 / Chapter 2.7.3.1 --- CSA for BB --- p.23 / Chapter 2.7.3.2 --- CSA for BT and TT --- p.24 / Chapter 2.7.4 --- Tensile test --- p.24 / Chapter 2.7.4.1 --- Testing procedures --- p.24 / Chapter 2.7.4.2 --- Interpretation of testing results --- p.25 / Chapter 2.7.5 --- Statistical analysis --- p.26 / Chapter 3. --- Results --- p.42 / Chapter 3.1 --- Surgical outcome --- p.43 / Chapter 3.1.1 --- Radiographic examination --- p.43 / Chapter 3.1.1.1 --- Bone-to-bone healing --- p.43 / Chapter 3.1.1.2 --- Bone-to-tendon healing --- p.44 / Chapter 3.1.2 --- Fluorochrome injection --- p.44 / Chapter 3.2 --- Histology --- p.45 / Chapter 3.2.1 --- Bone-to-bone healing --- p.45 / Chapter 3.2.1.1 --- Gross anatomy --- p.45 / Chapter 3.2.1.2 --- Microscopic examination --- p.45 / Chapter 3.2.1.3 --- Polarised light microscopy --- p.46 / Chapter 3.2.1.4 --- Fluorochrome microscopy --- p.46 / Chapter 3.2.2 --- Bone-to-tendon healing --- p.47 / Chapter 3.2.2.1 --- Gross anatomy --- p.47 / Chapter 3.2.2.2 --- Microscopic examination --- p.47 / Chapter 3.2.2.3 --- Polarised light microscopy --- p.48 / Chapter 3.2.2.4 --- Fluorochrome microscopy --- p.49 / Chapter 3.2.3 --- Tendon-to-tendon healing --- p.49 / Chapter 3.2.3.1 --- Gross anatomy --- p.49 / Chapter 3.2.3.2 --- Microscopic examination --- p.49 / Chapter 3.2.3.3 --- Polarised light microscopy --- p.50 / Chapter 3.3 --- Mechanical testing --- p.50 / Chapter 3.3.1 --- Bone-to-bone healing --- p.50 / Chapter 3.3.1.1 --- Change of cross sectional area --- p.50 / Chapter 3.3.1.2 --- Load at failure --- p.50 / Chapter 3.3.1.3 --- Strength --- p.51 / Chapter 3.3.1.4 --- Energy --- p.51 / Chapter 3.3.2 --- Bone-to-tendon healing --- p.51 / Chapter 3.3.2.1 --- Change of cross sectional area --- p.51 / Chapter 3.3.2.2 --- Load at failure --- p.52 / Chapter 3.3.2.3 --- Strength --- p.52 / Chapter 3.3.2.4 --- Energy --- p.52 / Chapter 3.3.3 --- Tendon-to-tendon healing --- p.52 / Chapter 3.3.3.1 --- Change of cross sectional area --- p.53 / Chapter 3.3.3.2 --- Load at failure --- p.53 / Chapter 3.3.3.3 --- Strength --- p.53 / Chapter 3.3.3.4 --- Energy --- p.53 / Chapter 3.3.4 --- "Comparison of healing quality among BB, BT, and TT repair" --- p.54 / Chapter 3.3.4.1 --- Change of cross sectional area --- p.54 / Chapter 3.3.4.2 --- Load at failure --- p.54 / Chapter 3.3.4.3 --- Strength --- p.54 / Chapter 3.3.4.4 --- Failure mode --- p.55 / Chapter 4. --- Discussion --- p.102 / Chapter 4.1 --- Use of goat calcaneus-Achilles junction as a bone-tendon reseach model --- p.103 / Chapter 4.2 --- "Bone-to-bone, bone-to-tendon, and tendon-to-tendon fixation" --- p.104 / Chapter 4.3 --- Histological characterization of different healing tissues --- p.105 / Chapter 4.3.1 --- Bone-to-bone healing (Fracture healing) --- p.105 / Chapter 4.3.2 --- Bone-to-tendon healing --- p.106 / Chapter 4.3.3 --- Tendon-to-tendon healing --- p.106 / Chapter 4.3.4 --- Regeneration versus repair --- p.107 / Chapter 4.4 --- Spatial and temporal expression of different type of collagen in different form of healing --- p.108 / Chapter 4.5 --- Mechanical properties of healing interface under different form of fixation --- p.108 / Chapter 4.5.1 --- Failure mode --- p.110 / Chapter 4.6 --- Limitations --- p.111 / Chapter 4.6.1 --- Goat animal model --- p.111 / Chapter 4.6.2 --- Immunohistochemistry --- p.111 / Chapter 4.7 --- Future study --- p.112 / Chapter 5. --- Conclusion --- p.113 / Chapter 6. --- References --- p.116

The purpose of this study was to compare the effects of two types of stem/progenitor cells on the healing of critical sized bone defects in a rat model. Endothelial progenitor cells (EPCs), a novel cell type with previously demonstrated effects on both osteogenesis and angiogenesis, were compared to both a control group (no cells), and a treatment group of mesenchymal stem cells (MSCs). The hypothesis was that EPCs would demonstrate both superior bone healing and angiogenesis, when compared to MSCs and controls. EPCs, MSCs, or a control carrier were placed in surgically stabilized bone defects in a rat femur and both bone formation and angiogenesis were assessed. EPC treated defects demonstrated significantly more bone formation and angiogenesis at the bone defect site than MSC or control treated defects. These results strongly suggest that EPCs are more effective than MSCs for therapeutic osteogenesis and angiogenesis in a bone defect model.