Total hip arthroplasty significantly improves the quality of life in majority of patients with osteoarthritis. However, prosthetic wear is a problem because of inducing the development of aseptic loosening and periprosthetic osteolysis which needs the revision surgery. Thus, the polyethylene wear measurement is the central to contemporary orthopaedics and this interesting has encouraged the development and improvement of both radiologic (in vivo) and non-radiologic (in vitro) methods for polyethylene wear quantification. The principles of polyethylene liner wear measurements are predominantly geometric; nevertheless, the realization of individual types of in vivo measurements brings with it the necessity of many simplifications and compromising steps to acquire approximately accurate values. In fact, the volumetric wear can be obtained by mathematical conversion based on the most linear shift of femoral head in the cup. However, such approach is understood to be somewhat insufficient. Our ongoing research pointed to the development of optical non-contact method for wear measurement and its results are introduced in this paper including the methodology designed for the usability validation of the method for the given purpose and the description of sensor, its principle, technical realization, design and parameters.
The purpose of the paper is to describe the measurement of shape of ceramic insert of coxal implant. In contrast to
polyethylene inserts, the ceramic inserts suffer very low wear during its usage, just about micrometers per year. It is
necessary to use coherence optical methods to sensitive enough to measure such small deformation. The contribution
describes principles of interferometry, the construction of experimental setup using Fizeau interferometer and discusses
the qualitative results of measurement of low-weared ceramic inserts of hip endoprothesis. These results will be used to
compare the wear of polyethylene and ceramic endoprothesis inserts and to create a statistic file of ceramic inserts wear.
This statistic file will be used to compare the wear of each ceramic insert with the age, gender, condition, way of life and
etc. of patients, who were using these implants.
Three dimensional measurements have great use today and it is quite large and important part of the experimental
physics. These methods are also used in biomedicine for measuring the abrasion of juncture implants, coxal cotyles and
knees. These implants are under stress in the patient's body and therefore they change their shape and waste some
material. This waste is a key parameter for examination of quality of the given type of implant. The surface of the used
implant is measured and compared with unused one. This comparison gives possibility to enumerate the waste of
material of implant. One of the three dimensional optic measurement methods is Fourier profilometry, based on the
analysis of harmonic structure projected on the surface of the measured object. It is profilometric method; it means that
the surface of measured object is specified in every point of result. Fundamentals of Fourier profilometry, its features
and used experimental setup are described in the beginning of the paper. The results of such measurement lead to
enumerate the waste of material of implant. The purpose of this contribution is the verification of used method to
measure the waste of material of implant. Its principle lies in artificial abrasion made by cutting tool, so the abrasion is
defined and known. The surface of the implant is measured before and after this machining and the waste of material of
implant is enumerated. This value is compared with an actual waste of material.
KEYWORDS: 3D scanning, Optical scanning, Metals, Surface finishing, 3D image processing, Particles, Bone, Global system for mobile communications, Adhesives, Abrasives
This article treats of using the 3D optical scanning topography as one of possible methods of an analysis of the cotyle
deformation. The object of this experiment is to quantify the decrease of cotyle material. The scanning object is
polyethylene coxa cotyle ABG I. We compare two identical coxa cotyle. One of them is artificially involved to simulate
a real using. We calculate material decrease of these cotyle, and then we compare the result with simulation and the
result of gravity surveying.
The presented paper is dealt with the calibration of methods of the optical 3D measurement of the shape of objects.
Methods can be divided into the two groups: topographic and profilometric methods. The topography is a method
giving a contour map as result. On the other hand, the result of the profilometry is the data file containing the
topographic depth (z-axis value) in the regular or irregular network of points (they are given by the x-axis and y-axis
values). Every method needs the calibration of these values that means the relation between measured and resulting
quantity. The x-axis and y-axis values are obtained as pixel distances from the record of optical image by the CCD
camera. The z-values are computed by various ways in dependence of the calibrated method character. It can be the
fringe orders, pixel distances again, phase differences or others. The paper describes the procedure of determination of
calibration constants. It is based on the known object measurement by the calibrated method and the following
evaluation of results.
The cotyle implantate is abraded in the body of patient and its shape changes. Information about the magnitude of
abrasion is contained in the result contour map of the implantate. The locations and dimensions of abraded areas can be
computed from the contours deformation. The method called the single-projector moire topography was used for the
contour lines determination. The theoretical description of method is given at first. The design of the experimental set-up
follows. The light grating projector was developed to realize the periodic structure on the measured surface. The method
of fringe-shifting was carried out to increase the data quantity. The description of digital processing applied to the moire
grating images is introduced at the end together with the examples of processed images.
Topography is a method giving a contour map as result of measurement describing three-dimensional shape of measured objects. The paper is focused to projection moire topography. The measurement model is compiled at first of all. The parameters of topography (accuracy, sensitivity, resolution, range) are introduced by virtue of this model. They are the great tool for description of measurement from the point of view of its quality. Some examples of topography of
object are introduced to illustrate the theoretical principles at the end.
The article is dealing with the measurement of three-dimensional shapes of objects. Such measurement is called the topography. The one of moire methods — the projection moire topography —is used. For improvement of measurement quality some methods are introduced. At first it is the washing-up method which deletes the linear background. At second the fringe-shifting method is described used for increasing of data quantity. And finally the optical/digital fringe multiplication is mentioned as a method for increasing the accuracy ofmeasurement. The topography is illustrated on the example ofmeasurement ofpump blade including its theory, experimental set-up and results.
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