Biomedical subjects

R B Lawrence

Publications and source records attributed to R B Lawrence.

6 recordsLinked to original sources

PubMed1985

The use of bicomponent fabrics for bonding polypropylene sockets in prostheses.

A technique has been established for bonding polypropylene sockets to the structural components of prostheses based on the use of bicomponent knitted fabrics which adhere to the surface of polypropylene sockets during thermoforming. The strength of adhesion of fabric bonded polypropylene with polyester resin based microballoon for instance is increased by more than 10 times relative to uncoated polypropylene. This procedure has been approved by the United Kingdom Department of Health for incorporating polypropylene sockets in conventional, laminated plastic patellar tendon bearing (PTB) prostheses. The bonding technique described should find general application for bonding polypropylene during the manufacture of both prosthetic and orthotic devices.

Artificial Limbs↗

PubMed1985

Prosthetic shape replication using a computer controlled carving technique.

This paper describes a carving machine which is the most recently developed module in the suite of CAD/CAM equipment for high technology manufacture and supply of prostheses. It provides the link between the Computer Aided Socket Design (CASD) system and the Rapidform socket manufacturing process. Using the coordinate data produced by the CASD system this machine, under computer guidance, carves from a large block of suitable material a three dimensional object; the equivalent of the rectified plaster model produced by conventional techniques. This provides the form for the fabrication of a socket and the facility completes an integrated system for fabricating, rapidly and cheaply, high quality lightweight prostheses for patients.

Amputation Stumps↗

PubMed1985

The Rapidform process for automated thermoplastic socket production.

This paper describes the genesis of the Rapidform process and its pioneering place in the new developments leading to complete control of the processes of manufacture of prostheses. The materials and geometric considerations involved in the development of a double deformation process under microprocessor control are described. Stages in the development of the system show the advance from the initial application to modular below-knee prostheses through extensions to special suspension systems (supracondylar and suprapatellar) to Syme's and above-knee sockets. The clinical and laboratory results are summarized along with an account of the current aspects of the project, ie advanced clinical trials, testing and analysis. Setting the scene historically for the other computer based modules in this high technology approach to prosthetics, Rapidform has proven to be swift, accurate and economical in its operation. Also, in common with the rest of the suite of equipment, this socket production facility, despite its flexibility and technical sophistication, requires no special services beyond standard single phase mains electricity supply.

Amputation Stumps↗

PubMed1985

Rotational moulding in the production of prostheses.

This paper discusses the place of rotational moulding in the provision of prosthetic shanks and shank sections. It covers the selection of thermoplastic material, the moulding conditions and their automation in a machine process, and the development of a suitable range of moulds. Also covered is the question of interfacing between the moulded shank sections and other limb components, fatigue strength as tested to date and early results of patient field trials. The most developed of the possible prosthetic options available consists of a hollow tapered column having inserts at each end by which it is clamped through alignment couplings to the socket and foot respectively. For a below-knee application, the complete tapered column prosthesis weighs typically 1 kg. Static and fatigue testing of representative samples by the simultaneous application of compressive and bending loads to the maximum values specified by international standards exposed no failures by the time a million cycles had been reached. This method of fabrication has the merit of being capable of implementation locally on an "as required" basis. Additional advantages include the low cost of the mould tooling and the flexibility to mould a variety of shapes. Prosthetic feet are a possibility as are special shoes and orthotic parts. These may require other materials and experimentation is proceeding using structural and resilient foams.

Biomedical Engineering↗

PubMed1984

Construction methods and materials for external prostheses--present and future.

In the first part of this paper the methods of constructing lower limb prostheses and their major components are discussed. Attention is paid to the foot, shank, knee joint, swing control, thigh, and hip joint. The second part is devoted to the use of thermoplastics in prosthesis and orthotics. Thermoplastics are polymers of varying chain length which can be moulded when heated. The properties of the various materials are discussed and their potential use described.

Amputation, Surgical↗

PubMed1979

Comparison of three methods for identification of pathogenic Neisseria species.

A radiometric procedure was compared with the Minitek and Cystine Trypticase Agar sugar degradation methods for identification of 113 Neisseria species (58 Neisseria meningitidis, 51 Neisseria gonorrhoeae, 2 Neisseria lactamica, 2 Neisseria sicca). Identification of meningococci and gonococci was confirmed by agglutination and fluorescent antibody techniques, respectively. The Minitek method identified 97% of meningococci, 92% of gonococci, and 100% of other Neisseria after 4 h of incubation. The radiometric (Bactec) procedure identified 100% of gonococci and 100% of miscellaneous Neisseria after 3 h, but problems were encountered with meningococci: 45% of the later strains yielded index values for fructose between 20 and 28 (recommended negative cut-off point, less than 20), with strongly positive (greater than 100) glucose and maltose and negative o-nitrophenyl-beta-D-galactopyranoside reactions in all 58 strains. The Cystine Trypticase Agar method identified 91% of meningococci, 90% of gonococci, and 100% of other Neisseria after 24 to 48 h. Prolongation of the Cystine Trypticase Agar incubation period led to abnormal lactose/sucrose reactions in some meningococci and gonococci. Radiometric and Minitek systems are more accurate and convenient than Cystine Trypticase Agar techniques, but, on the basis of these results, radiometric fructose sensitivity levels for meningococci need reevaluation.

Bacterial Infections↗