It has been speculated that material loss, either as corrosion or wear, at the head-stem taper junction is implicated in the high revision rates reported for metal-on-metal total hip replacements. We measured the volume of material loss from the taper and bearing surfaces of retrieved devices, and investigated the associations with blood metal ion levels and the diagnosis of a cystic or solid pseudotumor. The median volumes of material lost from the female and male taper surfaces were 2.0 and 0.29 mm 3 , respectively, while the median volumes of wear from the cup and head bearing surfaces were 1.94 and 3.44 mm 3 , respectively. Material loss from the female taper was similar to that from the acetabular bearing surface (p ¼ 0.55), but significantly less than that from the femoral bearing surface (p < 0.001). Material loss from the male taper was less than that from both bearing surfaces (p < 0.001). Multivariable analysis demonstrated no significant correlations between the volume of material lost from the taper surfaces and either blood cobalt or chromium ions, or the presence of pseudotumor. While a substantial volume of material is lost at the taper junction, the clinical significance of this debris remains unclear. ß

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Abstract. Measuring the amount of material loss in the case of revised hip replacements is considered to be a prerequisite of understanding and assessing the true in vivo performance of the implant. This paper outlines a method developed by the authors for quantifying taper material loss as well as more general taper interface parameters. Previous studies have mostly relied on visual inspection to assess the material loss at the taper interface, whereas this method aims to characterize any surface and form changes through the use of an out-of-roundness measurement machine. Along with assessing the volumetric wear, maximum linear penetration and taper contact length can also be determined. The method was applied to retrieved large head metal-on-metal femoral heads in order to quantify the material loss at this junction. Material loss from the female femoral head taper can be characterized as a localized area that is in contact with the stem taper surface. The study showed that this method has good repeatability and a low level of interoperability variation between operators.

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Assessment of the head-stem taper junction requires the estimation of material loss from the taper surfaces of both femoral head and stem. This paper describes a method for the measurement and analysis of material loss from the modular taper junction of hip replacements, in particular femoral stem tapers where generally the entire taper surface has been engaged. In such cases no direct unengaged datum surface is readily identifiable to assess material loss. The highly anisotropic topology of some stem designs poses additional challenges to the measurement and analysis process. Estimation of material loss of retrieved femoral stems is further complicated by retrieval damage or surface deposits often present on the taper surface. The femoral head tapers typically exhibit areas of pristine surface attributed to the difference in taper length compared to the engaging stem. These areas can be selected as unworn when employed in the analysis process, provided they do not show surface damage or deposits. Measurement of the taper surfaces has been performed using a Talyrond (Ametek, Inc., US) outof-roundness measurement instrument equipped with a 5µm diamond tip stylus. Vertical axial traces were employed to digitize the surface of the taper. Measurement data has been analyzed using a multi stage process that has been specifically adapted for stem tapers. The underlying stem taper geometry is determined by means of a morphological filter applied to the high aspect ratio microstructure. This paper presents a study of 40 retrieved LHMoM hip replacements that have been analyzed to ascertain the material loss at the modular taper junction. The purpose of this study was to ascertain the viability of characterizing material loss from the stem taper junction and to provide insight into the overall material loss contribution.

In our research we aim to evaluate the effectiveness of Games-based learning (GBL) within a Computer Aided Design and Manufacture (CAD/CAM) undergraduate module. Although widely used in a selection of subject areas, there appears to be limited application of GBL in Engineering and Technology (E&T). Its effectiveness as a learning or training tool, especially in Mechanical Engineering subject area, has been unclear. This research follows on from previously presented research in novel approaches in delivery of engineering education. Games-based Learning has a potential to enhance student experience and learning process. In order to evaluate the outcomes of GBL approach and observe its effect on students" performance, a simple in-class game on assembly topics was designed and implemented as part of a laboratory exercise. There were two groups of students" considered in this case study: the student group "playing" an assembly game (experimental group) and the group which did not experience GBL (control group). The results of the assessment element in the experimental group were compared to the control group. Our work evaluates both the qualitative and quantitative data established from CAD assembly delivery using the game, and delivery using conventional method. In addition, the comparisons were made between the entry level in to Higher Education in terms of tariff points level (academic score) of participants and educational background. It thus concludes on the effectiveness of the Games-based learning process in Mechanical Engineering Education.

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