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Biomedical subjects

B Derbyshire

Publications and source records attributed to B Derbyshire.

9 recordsLinked to original sources
PubMed1998

The estimation of acetabular cup wear volume from two-dimensional measurements: a comprehensive analysis.

This paper describes a mathematical investigation of the relationship between wear volume, wear depth and wear direction in acetabular components. The analysis takes into account the cylindrical and conical portions at the mouth of certain types of socket and also incorporates the effect of an initial radial discrepancy between the femoral head and socket. Published formulae for converting linear wear measurements to wear volumes are shown to be incorrect. Wear volume is shown to be highly dependent on the wear direction, increasing by more than 90 per cent over a 60 degrees range. Cylindrical and conical portions of a 22.225 mm cup may contribute up to about a third as much wear as the hemispherical socket. At low wear depths, the neglect of a radial discrepancy between the components can result in an overestimation of wear volume in excess of 100 per cent.

Acetabulum↗
PubMed1994

Comparative study of the wear of UHMWPE with zirconia ceramic and stainless steel femoral heads in artificial hip joints.

The wear of ultra high molecular weight polyethylene (UHMWPE) when sliding against zirconia ceramic and stainless steel counterfaces has been compared in a pin-on-plate reciprocator and in a hip joint simulator. A lower wear factor was found for the UHMWPE when sliding on the zirconia ceramic counterfaces in the pin-on-plate tests. In the hip joint simulator test, the acetabular cups articulating on zirconia heads showed consistently lower volume changes than the cups articulating on stainless steel heads. The higher volume changes found with the stainless steel heads were associated with an increased roughness of the femoral heads during the tests. This roughening was caused by the adherence of a rough polymer transfer film.

Biocompatible Materials↗
PubMed1989

A shapeable foot-pressure measuring device.

Measurement of foot pressure distribution for clinical purposes should ideally be made inside the shoe with a shaped insole and raised heel. Pressure measuring platforms cannot do this and transducers inserted inside the shoe can be obtrusive and inaccurate. The main clinical benefit of foot pressure measurement is the assistance it gives to shoe insole design. A shapeable foot pressure measuring device is being developed. The device can be accurately shaped to the contours of the foot and can indicate the pressure distribution over the entire surface of the foot. By adjusting the shape locally, high pressure areas can be relieved and the resulting shape can be used to vacuum-form a shoe insole. The device also has potential for the manufacture of special seating.

Equipment Design↗
PubMed1980

Problems of encapsulation of total joint replacements.

Particulate wear debris of artificial joints, metallic and plastic, and solutions of metals in body fluids are known to have adverse effects. Encapsulation of the articulating parts would prevent wear debris from entering the surrounding tissue and check tissue ingrowth into the joint. The capsule could contain an artificial lubricant to reduce friction and wear and increase the joint life. For the capsule material, several bioelastomers are being tested in an environment of body fluids and lubricants. Three fatigue rigs have been developed for these tests. Tests have shown that a bovine synovial fluid environment causes a tenfold increase in the fatigue life of silicone rubber. A special capsule shape for minimizing stresses due to creasing is being investigated. Electrophoresis has been explored as a method of filtration of wear debris. It has been shown that Co-Cr-Mo alloy wear particles are attracted to polymers having permanent negative surface charge.

Filtration↗