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Biomedical subjects

L A Dauphinais

Publications and source records attributed to L A Dauphinais.

4 recordsLinked to original sources
PubMed1992

Enhanced ingrowth of porous-coated CoCr implants plasma-sprayed with tricalcium phosphate.

Tricalcium phosphate (TCP) is an osteo-conductive bioceramic which, when applied to a porous-coated prosthesis, may enhance osseous ingrowth and mechanical stability. TCP plasma-sprayed and unsprayed porous-coated tibial intramedullary rods were bilaterally implanted in seven adult rabbits. All rabbits were killed at 12 weeks. Pull-out tests were performed on 4 rabbits while all were evaluated histologically for osseous response and adverse tissue reaction. TCP-sprayed implants showed significantly greater osseous ingrowth in comparison to unsprayed implants. Neither implant type exhibited adverse tissue reactions. Average pull-out strengths were 69 lb for treated rods and 72 lb for controls (p greater than 0.05); quality of fit for all pull-out specimens except one was deemed poor. We conclude that plasma-sprayed TCP enhances osseous ingrowth into porous-coated devices. However, our data further suggest that enhanced ingrowth may not always lead to enhanced fixation.

Alloys↗
PubMed1990

The biomechanical problems of polyethylene as a bearing surface.

The metal backings of acetabular components can reduce the available polyethylene thickness, often to an alarming extent. This study indicated that the pitting and cracking of thin polyethylene surfaces have some similarities to tibial and patellar bearings and that creep-related deformation occurred more frequently in thin polyethylene components. Additionally, it appears that dimensional tolerances of the polyethylene inserts are difficult to maintain and may result in a nonuniform fit of both the femoral head into the component and the component into its own metal backing, which can lead to component separation. It is difficult to accurately measure the changes in material and mechanical properties of polyethylene over time. An additional ramification is that flaws, such as voids in the polyethylene, cannot be attributed to problems of bulk supply, fabrication, or postmanufacturing treatment. Orthopedic device manufacturers should keep samples of each lot of polyethylene used and provide components with serial numbers so that the source, composition, and properties of the original bulk material and material "as fabricated" can be documented. This would permit researchers studying revisions or postmortem samples to determine the changes in the polyethylene over time in vivo, thus improving the understanding of this crucial material. If manufacturers were to include dimensions and tolerances of the polyethylene inserts in their product literature, accurate measurements of wear of retrieved specimens may be possible.

Acetabulum↗
PubMed1988

Macroscopic and microscopic evidence of prosthetic fixation with porous-coated materials.

The host response to porous-coated prostheses appears favorable; there is little evidence of any adverse tissue response or significant osteoclastic activity except in grossly loose specimens. While the nature of retrieval specimens makes any statistical correlation problematic, some generalizations can be made. Femoral hip prostheses are most likely to present bone ingrowth along the lateral quadrant of their porous coating. The frequency of bone ingrowth of femoral components was nearly twice that of acetabular devices. Pore size, geometry, and porous-coating composition did not appear to influence the appearance of bone and fibrous tissue ingrowth. Direct bonding of bone to the uncoated portion of the prosthesis was rarely seen and occurred only in closest proximity to the porous-coated regions. Indications of pain and looseness are evidence that fibrous tissue ingrowth alone is not always sufficient to ensure stability. Additionally, some bone-ingrown prostheses were retrieved because of pain, which leads to the conclusion that local bone ingrowth cannot ensure a general freedom from pain, especially with partially coated prostheses. Bone and fibrous tissue response to the porous coatings generally consists of interdigitation, while the response to uncoated regions is fibrous tissue encapsulation. Burnishing the distal tips of many of the partially coated femoral prostheses is an indication of relative motion in that region, which may be a potential source of pain.

Acetabulum↗