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Item type:Publication, Access status: with files , Clinical and wear analyses of 9 large metal-on-metal total hip prostheses(Public Library of Science (PLoS), 2016-10-06); ; ; ; Metal-on-Metal (MoM) total hip arthroplasties (THA) are associated with pseudotumor formation and high revision rates. This prospective study analysed the clinical and wear analyses of 9 large Metal-on-Metal (MoM) total hip arthroplasties (THA) to understand the underlying mechanisms of failure. The MoM bearings were revised for multiple reasons; the main reason was pseudotumor formation.Publicationtype: Journal ArticleScopus© Citations 6 191 289 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Contamination of modular hip taper interfaces increases post-assembly interface seating(British Editorial Society of Bone and Joint Surgery, 2016-05-01); ; ; 9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Quantification of the contact area at the head-stem taper interface of modular hip prostheses(Public Library of Science (PLoS), 2015-08-17); ; ; Corrosion of modular taper junctions of hip implants may be associated with clinical failure. Taper design parameters, as well as the intraoperatively applied assembly forces, have been proposed to affect corrosion. Fretting corrosion is related to relative interface shear motion and fluid ingress, which may vary with contact force and area. It was hypothesised in this study that assembly forces modify the extent and distribution of the surface contact area at the taper interface between a cobalt chrome head and titanium stem taper with a standard threaded surface profile. Local abrasion of a thin gold coating applied to the stem taper prior to assembly was used to determine the contact area after disassembly. Profilometry was then used to assess permanent deformation of the stem taper surface profile. With increasing assembly force (500 N, 2000 N, 4000 N and 8000 N) the number of stem taper surface profile ridges in contact with the head taper was found to increase (9.2±9.3%, 65.4±10.8%, 92.8±6.0% and 100%) and the overall taper area in contact was also found to increase (0.6±0.7%, 5.5±1.0%, 9.9±1.1% and 16.1±0.9%). Contact was inconsistently distributed over the length of the taper. An increase in plastic radial deformation of the surface ridges (-0.05±0.14 μm, 0.1±0.14 μm, 0.21±0.22 μm and 0.96±0.25 μm) was also observed with increasing assembly force. The limited contact of the taper surface ridges at lower assembly forces may influence corrosion rates, suggesting that the magnitude of the assembly force may affect clinical outcome. The method presented provides a simple and practical assessment of the contact area at the taper interface.Publicationtype: Journal ArticleScopus© Citations 32 343 288 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The influence of stem taper re-use upon the failure load of ceramic heads(2015-06-01); ; ; Ceramic components are frequently used in total hip replacement due to their good tribological properties. In revision of broken ceramic heads clinical uncertainties arise, whether the taper of the stem can be re-used with a new ceramic head, especially if the stem is well fixed. Ceramic is a brittle material. Even small damage on the male stem taper can lead to stress concentrations causing premature failure of a new ceramic head. As a consequence, manufactures strictly prohibit stem taper re-use for ceramic heads. The aim of this study was to determine the fracture strength of ceramic heads assembled to re-used male stem tapers, which were subjected to prior head fracture. Five 12/14 Ti6Al4V male tapers and 15 Al2O3 ceramic heads (BIOLOXforte® θ 28mm, L) were used for three consecutive fracture tests. Before and after every fracture test, all components were inspected visually and the surface geometry was analyzed. Mean fracture force (52.5kN) did not decrease with the number of taper re-uses (p≥0.77) but the range increased significantly from initially 4.1kN to 31.8kN for the first and 52.6kN for the second re-use due to some components failing at very low loads. Visual inspection was not sufficient to predict the reduced failure loads. Ceramic heads should therefore not be put on used male tapers without metal adapter sleeves.Publicationtype: Journal Article117 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Severe wear and pseudotumor formation due to taper mismatch in a total hip arthroplastyCase: We describe the case of a seventy-six-year-old woman who had undergone bilateral total hip arthroplasty with Zweymüller-Metasul prostheses in 1996. After a fall sixteen years after the index procedures, radiographs suggested a taper fracture of the left total hip arthroplasty. However, revision surgery showed pseudotumor formation, with no evidence of taper fracture. Analysis of the prosthesis showed massive wear of the male stem taper caused by a mismatch between the stem taper and the head taper. Conclusion: This case vividly demonstrates how taper size mismatch can cause dramatic metal wear and increased release of metal ions, resulting in pseudotumor formation.Publicationtype: Journal Article118 - 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 , The relation between titanium taper corrosion and cobalt-chromium bearing wear in large-head metal-on-metal total hip prostheses : a retrieval study(American Academy of Orthopaedic Surgeons, 2014-09-17); ; ; Background: Revision of hip implants due to adverse tissue reactions to metal debris has been associated with wear and corrosion of the metal-on-metal bearing articulation and the modular taper interface. Bearing articulation wear is increased in conditions of poor lubrication, which can also lead to high friction moments that may cause corrosion at the taper interface. This suggests that wear of the bearing and increased corrosion of the taper interface should occur simultaneously, which was investigated in this study.Publicationtype: Journal Article10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Wear of a composite ceramic head caused by liner fracture(2014-06-26); ; ; ; Dalla Pria, PaoloThird-generation composite ceramics (eg, Delta; DePuy Orthopaedics, Warsaw, Indiana; Ceramtec, Plochingen, Germany) have greatly improved material characteristics compared with second-generation products. This case report presents a patient after total hip arthroplasty with a fractured ceramic liner and a heavily worn ceramic head (both third-generation ceramics) retrieved 9 months after surgery. The patient showed no symptoms in the involved hip but presented to the hospital because of other symptoms. The failure was caused by a tilted liner that was overlooked after surgery and fractured consecutively. Rim chipping and splitting were the 2 fracture modes observed for the liner. The head did not fracture completely because of its high strength but became roughened by the ceramic fragments, causing major wear of the metal back of the cup. The phase transformation of the zirconium grains from tetragonal to monoclinic in the aluminum oxide matrix was shown by radiographic diffraction analysis in the heavily worn areas of the head. This transformation increases the fracture strength of the head. Metal debris caused by a roughened ceramic head without fracture is an unreported phenomenon for third-generation ceramic bearings in hip arthroplasty. This case shows that proper impaction of the ceramic liner into the metal shell to prevent later tiling during reduction is as important as correct component positioning. If a tilted ceramic liner is observed postoperatively, the position must be corrected immediately to prevent the major consequences observed in this patient.Publicationtype: Journal Article14 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Arthroprosthetic cobaltism and pseudotumour also occur in patients with small diameter femoral ball head metal-on-metal total hip arthroplastiesMetal-on-metal implants have been widely discredited in public during the past few months. At the same time patients' awareness has risen leading to an increased number of consultations regarding the topic. As hip resurfacings and total hip arthroplasties with large diameter femoral ball heads are already known for excessive metal wear, even small diameter ball heads with low friction get into focus now. We report a case of a 75-year-old man with recurrent hip pain almost 14 years after low friction metal-on-metal total hip arthroplasty. In addition to elevated serum cobalt levels, a type IV sensitivity reaction to cobalt could be noted. Explantation of a highly worn small diameter femoral ball head as well as development of the so-called pseudotumour indicate that all patients should be screened for signs of metal wear regardless of their specific risk factors or the type of metal-on-metal implant.Publicationtype: Journal Article28