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Item type:Publication, Access status: without files , The taper disaster - How could it happen?(2015-07-01)Corrosion of metallic implants in contact with body fluids is unavoidable, especially at interfaces where movement occurs or in gaps. Corrosion became clinically relevant with the introduction of large modular metal-on-metal total hip joint articulations (MoM THA) early in the 21st century. This review attempts to summarise the scientific knowledge about taper problems available at the time of introduction of these bearings, why this "disaster" could happen. It is speculated that changes to the taper connection made in the 1990s to increase the range of motion with small heads (28 and 32 mm) reduced the mechanical strength of this connection, which did not matter for small heads. With the use of large and very large metal heads in MoM articulations, which have a larger lever arm and can generate high friction in unfavourable situations, suddenly the taper interface exhibited corrosion problems on a previously unknown scale. It is speculated that due to the higher mechanical loading with larger heads, the taper connection became less forgiving with respect to assembly conditions, contamination, manufacturing tolerances and other factors, which are yet not known. Since no major clinical problems had been reported before the introduction of these bearings and the pre-clinical testing was very successful, the disaster took its course. The patient-implant-surgeon system is a very complex intrinsically hazardous system. Pre-clinical testing addresses few and defined factors and such, good results cannot be directly transferred to the clinical reality. A controlled stepwise introduction of innovations is required.Publicationtype: Journal Article105 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Basic principles and uniform terminology for the head-neck juncton in hip replacement(2015-01-11); ; ; ; Recent problems with large head metal on metal hip replacements have spiked renewed interest in the head-neck juncton. A thorough knowledge of the principles of the locking mechanism, the assembly technique and afectng factors on the strength of this juncton is needed. Currently a confusing variability in terms is used to describe this juncton. This overcomplicates an already complex issue. The purpose of this literature review is to collect and list the diferent terms used and to propose a uniform terminology. Two authors independently searched the electronic databases of PubMed, CINAHL and MEDLINE with specific key words and combinatons according to the PRISMA guidelines. The inital search yielded a total of 518 artcles with ultmately 53 artcles included in the present analysis. No consensus for a uniform term for the 2 sides of the head-stem juncton was found. Since there is already pronounced variability in taper designs between diferent manufacturers (even so similarly named, e.g. “12/14”), a uniform terminology could be the frst step to simplify the situaton. “Male” and “female taper” is proposed as the appropriate terminology for the stem and head juncton in hip replacement, respectvely. The importance of the assembly technique understanding the principles of the locking mechanism is emphasised.Publicationtype: Journal Article57 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Basic principles and uniform terminology for the head-neck junction in hip replacement(Sage Publications, 2015); ; ; ; Recent problems with large head metal on metal hip replacements have spiked renewed interest in the head-neck junction. A thorough knowledge of the principles of the locking mechanism, the assembly technique and affecting factors on the strength of this junction is needed. Currently a confusing variability in terms is used to describe this junction. This overcomplicates an already complex issue. The purpose of this literature review is to collect and list the different terms used and to propose a uniform terminology. Two authors independently searched the electronic databases of PubMed, CINAHL and MEDLINE with specific key words and combinations according to the PRISMA guidelines. The initial search yielded a total of 518 articles with ultimately 53 articles included in the present analysis. No consensus for a uniform term for the 2 sides of the head-stem junction was found. Since there is already pronounced variability in taper designs between different manufacturers (even so similarly named, e.g. “12/14”), a uniform terminology could be the first step to simplify the situation. “Male” and “female taper” is proposed as the appropriate terminology for the stem and head junction in hip replacement, respectively. The importance of the assembly technique understanding the principles of the locking mechanism is emphasised.Publicationtype: Journal Article3 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Consensus statement "Current evidence on the management of metal-on-metal bearings" April 16, 2012(Sage Publications, 2013-01-01); ; ; ; The following recommendations are based on expert opinions of an international multidisciplinary panel endorsed by the "European Federation of National Associations of Orthopaedics and Traumatology" (EFORT), the "European Hip Society" (EHS), the German "Arbeitsgemeinschaft Endoprothetik" (AE) and the "Deutsche Arthrosehilfe" (DAH). © 2013 Wichtig Editore - ISSN 1120-7000.Publicationtype: Journal ArticleScopus© Citations 38 27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The condition of the cement mantle in femoral hip prosthesis implantations : a post mortem retrieval study(Wichtig Publishing, 2009); ; ; ; Despite numerous studies demonstrating the characteristics of the optimal cement mantle in joint replacement, the clinical state of the cement mantle is rarely assessed. A random sample of 214 cemented implated femoral hip components was retrieved post mortem from Hamburg, Germany, and sectioned to investigate the quality of the cement mantle. The most common observation made in at least one measured region per retrieval was debonding (82% of stems), followed by a thin cement mantle (74%), stem-bone contact (48%), soft tissue at the stem interface (44%), no cement-bone interdigitation (30%), a gap at the stem interface (28%), voids in the cement (22%) and cracks and blood in the cement mantle (<10%). 21% of stems demonstrated complete debonding of the interface. However, distributions of all other defects were local, with less than 10% of stems demonstrating any imperfection in more than 21% of the regions assessed. No progressive damage was observed with implantation duration. The results suggest that current implantation technique may be adequate for proper implant function over the service life in the older patient population. However, for younger and more active patients, perfection of the cementation technique is crucial, particularly in modern implant systems such as resurfacing. The frequency of almost all defects could be further reduced by careful implantation technique, providing the increased service life necessary for the ever younger, more physically demanding, patient population. © Wichtig Editore, 2009.Publicationtype: Journal Article4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Biomechanics of a new short-stemmed uncemented hip prosthesis : an in-vitro study in human boneThe migration pattern, cyclic motion, system stiffness and failure load of a new short-stemmed hip prosthesis were compared to a clinically successful shaft prosthesis during the initial loading phase. The influence of implant-sizing on mechanical stability was also investigated for the new stem, in particular with relation to the bone quality. Prostheses were implanted in paired human femora and loaded cyclically up to 3515 cycles. Relative displacements between prosthesis and bone were measured using a 3D-camera and reflective marker system. Migration of the new stem was predominantly into varus and was higher than for the shaft prosthesis. The test set-up wes proposed to simulate a worst-case loading scenario since muscle forces, which tend to reduce bone deformation, were not simulated. It could therefore be expected that clinical migration of the implants would be less pronounced than that observed in this study. Cyclic motion for the new stem was similar to that for the clinically successful shaft prosthesis, suggesting that bone ingrowth could be expected for the new stem. No significant difference in fracture load was observed between the implants. The system stiffness with the new stem was lower than for the shaft prosthesis, indicating more physiological load transfer. Smaller implant sizing with 'cancellous' fixation seems favourable, as it led to similar migration and smaller cyclic motion values than with 'cortical' fixation. A trend for higher cyclic motion and migration was observed in femora with poor bone quality. Hence, sufficiently good bone stock is necessary when implanting the new short-stemmed prosthesis. © Wichtig Editore, 2006.Publicationtype: Journal Article4