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No description available.

No description available.

No description available.

No description available.

No description available.

The spinal column as a static structure is analysed in an attempt to quantify the mechanics of the system, of particular interest has been the derivation of forces, in operation in the muscles, required to maintain the equilibrium of the spine it various positions. Three approaches to the solution of the structural problem have been used, namely: (a) Establishing the equations of equilibrium for the thoracic and lumbar vertebrae, involving body weight, external dead load, muscle force and the intervertebral reactions. These equations are solved using the Linear Programming technique which minimizes the total force in the system. The solution gives numeric values for the muscle forces and intervertebral reactions; (b) An iteration technique, which derives the material properties of a structure from displacement and applied load data, is used to analyse simple element structures involving bars and beams; (c) Using both the Linear Programming technique and a structural analysis of the spine involving bar and beam finite elements to form a complete static model of the spine. The Linear Programming as in (a) is used in an initial upright position. The structural analysis is used to calculate the vertebral forces required to deform the spine to a deflected position. Combining the two studies gives values for the intervertebral reactions in the deformed position, these, the body weight and the dead load are input into a modified set of equations of equilibrium which are solved by Linear Programming. The method (a) has been used to give results for forward flexion, lateral flexion and a scoliotic curve with several orthopaedic supports. The approach (c) has been used for forward flexion alone.

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Tendons transmit tensile load from skeletal muscles to bone. They fundamentally consist of densely packed longitudinal collagen fibres separated by rows of tendon fibroblasts. The cells have extensive cell-cell contacts, longitudinally within the rows and between rows via cell processes. This thesis explores how cell-cell interactions and the cytoskeleton relate to matrix secretion and organisation in developing chicken tendons and cell cultures. In initial developmental stages, indicated by tenascin and type I collagen expression, cells were associated with cadherins, vinculin and connexin 32, and the presence of actin fibres. Subsequently, type III collagen delineated early fascicular structure, and later still connexin 43 appeared, relating to mechanical loading and formation of a cellular regulatory network. In culture, monolayers laid down minimal matrix, high density micromass cultures laid down more and pellet cultures produced an extensive matrix, although 75% of their collagen was lost to the medium. Micromasses and pellets expressed similar cytoskeletal and cell junctional markers to the in vivo tendons monolayers differed with early expression of connexin 43. TGF0, bFGF and PDGF singly or in combination had minor effects on collagen production and deposition and had no effect on cell junctional or cytoskeletal components. Finally, a novel suspension culture system was developed to allow large numbers of cells to interact and deposit matrix without interference from medium changes. After establishing that cells aggregated rapidly in suspension culture, suspensions were placed in dialysis tubes contained within 50ml sterile plastic tubes and cultured on rollers, with medium being changed only in the large tubes, leaving the cell suspensions undisturbed. This produced structures up to 3cm in length, with good cell and matrix organisation and seeming to incorporate more collagen into the extracellular matrix than pellet cultures. This could form the basis for a simple scaffold-free tissue engineering approach for tendons and ligaments.