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P De Meester

Publications and source records attributed to P De Meester.

14 recordsLinked to original sources
PubMed1983

Fatigue properties of implant materials in hip prosthesis form: a standardized test.

The determination of the fatigue properties on small specimens is not accurate. It does not take into account the considerable scatter in fatigue properties which may arise in the implants. Therefore, testing of the properties on the actual implant is needed. The working hypothesis of the present article is that four-point bending fatigue tests allow determination of the fatigue limit of the femoral component material in total hip prostheses. It eliminates the disadvantages of the previously proposed load on head test because (1) the reproducibility of the stress pattern is easy; (2) the fatigue testing is over the whole critical part of the stem; and (3) the stresses do not change during the test. Testing of a series of hip prostheses shows that (1) the measured fatigue limit is typical for the material tested; (2) the location of the fatigue fractures is over the critical medial third of the stem; and (3) the fractographic aspects correspond to those of in vivo failed prostheses. The four-point bending procedure is proposed as a standard method.

Biocompatible Materials↗
PubMed1983

The mechanical characteristics of cancellous bone at the upper femoral region.

Mechanical behaviour of trabecular bone at the upper femoral region of human bones has been studied by compression tests on trabecular bone specimens removed from normal femora obtained at autopsy. Compression tests were performed along three different axes of loading on wet specimens and high loading rates. Femoral head specimens proved to be the strongest for any axis of loading. Large variation in compressive strength and modulus of elasticity is seen within and between femoral bone samples. Anisotropy and differences in anisotropy for the different regions have been observed. A significant correlation between mechanical properties (sigma max - E) and bone mineral content of the specimen was found. Tests on whole bone structures demonstrate that removal of the central part of the trabecular bone at the proximal femur reduces the strength for impact loading considerably (+/- 50%).

Biomechanical Phenomena↗
PubMed1977

Microscopic fracture aspects of impact tested human bones.

The fracture aspects of impact twisted human femurs and tibias have been studied in their wet condition. The main tool used to correlate fracture behaviour with bone structure was the scanning electron microscope. Supplementary data were obtained from macroscopic fracture pattern analyses and stress coat experiments on slowly tested dried bone. The interest of the data reported concerns two major points. Firstly the analysis of the fractographic results leads to the conclusion that the fracture has presumably been initiated by shearing parallel with the torsion axis. The fracture propagates along so called spiral and oblique fracture lines. Secondly, the correlation of the macroscopic fracture pattern with microscopic fracture aspects indicates that the fracture is initiated along the cement lines, which can be considered as the weak matrix in an osteon-cement lining composite. The fracture propagates along the cement lines as well as through osteons and lamellae. Throughout the impact fracture surfaces ductile and brittle fracture aspects were observed, although the brittle fracture mode was predominant during propagation.

Bone and Bones↗
PubMed1975

Fatigue fractures of the femoral component of Charnley and Charnley-Müller type total hip prostheses.

A survey is given of the mechanical failures of the femoral component of Charnley and Charnley-Müller type total hip prostheses. Fractographic analysis reveals that all the prostheses have broken by metal fatigue. A review of the clinical data has been combined with a metallurgical and a mechanical study in order to assess the reasons of the mechanical failures. The following conclusions have been reached. The prosthesis should be inserted in varus position with regard to the axis of the intramedullary canal, and the prosthesis should be made of an alloy with appreciably higher yield stress and fatigue strength than the alloys of the investigated broken Charnley and Charnley-Müller type prostheses.

Alloys↗
PubMed1974

X-ray evidence for metal-N-7 bonding in a hydrated manganese derivative of guanosine 5'-monophosphate.

Single-crystal X-ray studies of a manganese(II) derivative of guanosine 5'-monophosphate, [Mn(5'-GMP)(H(2)O)(5)],3H(2)O, have shown that it is isostructural with its nickel analogue. The manganese atom therefore is bonded to five water molecules with the remaining octahedral co-ordination site being occupied by N-7 of the nucleotide base. No direct metal-phosphate bonding is involved, but there are structure-stabilizing intramolecular hydrogen bonds between two phosphate oxygen atoms and co-ordinated water molecules.

Guanine Nucleotides↗
PubMedDate not supplied

[Hypercalcemia].

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Adenoma↗