Analytic guidelines for optimal stem designs of custom-made joint prostheses

Functional reconstruction of bones and joints by total joint replacement has become an attractive alternative to limb amputation. This paper addresses design of the stem to establish an optimal stem shape for a specific bone when its dimensions are known from x-rays, and to establish an optimal dimensional classification system. [2 Refs

A survey of finite element analysis in orthopedic biomechanics : the first decade

The finite element method (FEM), an advanced computer technique of structural stress analysis developed in engineering mechanics, was introduced to orthopedic biomechanics in 1972 to evaluate stresses in human bones. Since then, this method has been applied with increasing frequency for stress analyses of bones and bone-prosthesis structures, fracture fixation devices and various kinds of tissues other than bone. The aims of these investigations were to assess relationships between load carrying functions and morphology of the tissues, and to optimize designs and fixation techniques of implants. Although the amounts of significant findings and useful concepts generated by the FEM during the first decade of its application in this field were limited, many publications have served to illustrate its capabilities and limitations. The method is now well established as a tool for basic research and for design analysis in orthopedic biomechanics, and the number of publications in which it is used is increasing rapidly. In the meantime, following developments in engineering mechanics, the capabilities of the method are augmented which, together with an increasing sophistication of computers, guaranties exciting possibilities for the future. However, the biological structures and the clinical problems concerned are complex. Scientific progress in this area requires a sound understanding of engineering mechanics on the one hand, and a profound appreciation of the complex reality on the other. These features were not always apparent in the FEM work reported during the first ten years. In the following survey, the developments of FEM applications in orthopedic biomechanics during the first decade are discussed. Special problem areas are indicated and future trends anticipated

Guidelines for external fixation frame rigidity and stresses

Using results from FEM analyses and experiments as references, analytical methods are applied to develop simple approximate formulas to relate frame rigidity, maximal pin stresses, and peak pin-bone stresses in external fracture fixation (EFF) configurations in axial loading to the most important frame, pin, and bone parameters. It is found that, in a realistic range, the parameters can be adapted to vary the frame rigidity from about 13 N/mm to 17,000 N/mm, thereby reducing the maximal stresses in the pins and at the pin-bone interface by a factor of 140. In particular, when compromises have to be established in the frame characteristics in order to ensure a flexible configuration and limit the stress values at the same time, the formulas presented can provide useful guidelines. The side-bar separation and the pin modulus, in particular, can be adapted to decrease the rigidity, while only moderately increasing the stresses, thereby reducing changes for pin failure, pin-bone loosening, and pin-tract infection. A nomogram is presented for a quick reference to estimated relations between frame characteristics, rigidity, and stresses. It is believed that this material may be of use in EFF design and applications in clinical and animal experimental trials. [Journal Article; In English; United States]Specialty IndexingSource ID: NASA - 8614318

Biomechanical properties and design considerations in upper extremity external fixation

External fixation is an excellent technique for the osteosynthesis of fractures affecting the upper extremity. The rational use of the technique is based on sound principles of biology and biomechanics. Good pin design and application techniques are among the important factors for successful outcome. These factors are discussed in this article along with the advantages of external fixation.SCOPUS: re.jinfo:eu-repo/semantics/publishe