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Item type:Publication, Access status: without files , Comparative biomechanical in vitro study of different modular total knee arthroplasty revision stems with bone defects(Elsevier, 2020-06-17); ; ; ; The aim of this study is to investigate the effects of different stem lengths and types including cones on primary stability in revision total knee arthroplasty with different femoral bone defects and fixation methods in order to maximize bone preservation. It is hypothesized that longer stems provide little additional mechanical stability. Methods: Thirty-five human femurs were investigated. A distal bone defect, Anderson Orthopedic Research Institute classification (s. 33) type-F2a, was created in group 1-3 and type-F3 in group 4-6. A cemented, rotating hinge femoral component was combined with different stems (100 and 160 mm total or hybrid cemented cones, or a 100-mm custom-made anatomical cone stem). The femora were loaded according to in vivo loading during gait. Relative movements were measured to investigate primary stability. Pull-out testing was used to obtain a parameter for the primary stability of the construct. Results: Relative movements were small and similar in all groups (<40 μm). For small defect, the pull-out forces of cemented long (4583 N) and short stems (4650 N) were similar and about twice as high as those of uncemented stems (2221 N). For large defects, short cemented stems with cones showed the highest pull-out forces (5500 N). Long uncemented stems (3324 N) and anatomical cone stems (3990 N) showed similar pull-out forces. Conclusion: All tested stems showed small relative movements. Long cemented stems show no advantages to short cemented stems in small bone defects. The use of cones or an anatomical cone stem with hybrid cementation seems to offer good stability even for larger bone defects. The use of a short cemented stem (with or without cone) may be a suitable choice with a high potential for bone preservation in total knee arthroplasty revision with respective bone defects.Publicationtype: Journal Article453 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Head taper corrosion causing head bottoming out and consecutive gross stem taper failure in total hip arthroplasty(Elsevier, 2018-07-24); ; ; ; Taper corrosion in total hip arthroplasty for bearings with metal heads against polyethylene has developed from an anecdotal observation to a clinical problem. Increased taper wear and even gross taper failure have been reported for one particular design. It is hypothesized that corrosion of the female head taper results in taper widening, allowing the cobalt-chromium head to turn on the stem and wear down the softer titanium alloy by abrasive wear, ultimately causing failure. The purpose of this study is to investigate the time course of this process and the general role of taper dimensions and material in this problem.Publicationtype: Journal ArticleScopus© Citations 42 308 827 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The Influence of Contamination and Cleaning on the Strength of Modular Head Taper Fixation in Total Hip Arthroplasty(2017-10); ; Background Intraoperative interface contamination of modular head-stem taper junctions of hip implants can lead to poor fixation strength, causing fretting and crevice corrosion or even stem taper fracture. Careful cleaning before assembly should help to reduce these problems. The purpose of this study was to determine the effect of cleaning (with and without drying) contaminated taper interfaces on the taper fixation strength. Methods Metal or ceramic heads were impacted onto titanium alloy stem tapers with cleaned or contaminated (fat or saline solution) interfaces. The same procedure was performed after cleaning and drying the contaminated interfaces. Pull-off force was used to determine the influence of contamination and cleaning on the taper strength. Results Pull-off forces after contamination with fat were significantly lower than those for uncontaminated interfaces for both head materials. Pull-off forces after application of saline solution were not significantly different from those for uncontaminated tapers. However, a large variation in taper strength was observed, pull-off forces for cleaned and dried tapers were similar to those for uncontaminated tapers for both head materials. Conclusion Intraoperative contamination of taper interfaces may be difficult to detect but has a major influence on taper fixation strength. Cleaning of the stem taper with saline solution and drying with gauze directly before assembly allows the taper strength of the pristine components to be achieved. Not drying the taper results in a large variation in pull-off forces, emphasizing that drying is essential for sufficient and reproducible fixation strength.Publicationtype: Journal Article146 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Mechanical Stability of the Taper Connection of Large Metal Femoral Heads With Adapter Sleeves in Total Hip Arthroplasty Analyzed Using Explicit Finite Element SimulationsBackground Large diameter heads (LDHs) of metal-on-metal bearings in total hip arthroplasty provide increased range of motion and reduced dislocation rates. However, major concerns grew over high wear rates from the modular connection between femoral stem and head, especially in combination with adapter sleeves. Methods A computational study on the taper connection stability of LDH (50 mm) with adapter sleeves of different lengths (S, M, L, and XL) compared with a standard femoral head (32 mm) without adapter sleeves was conducted using explicit finite element analyses. Four different impact configurations were considered resulting from varied mallet mass (0.5 vs 1.0 kg) and velocity (1.0 vs 2.0 m/s). The taper stability was evaluated by determination of the pull-off forces and micromotions due to simulated joint loads during walking (2 kN and 7.9 Nm, respectively). Moreover, the deformations of the adapter sleeves and the contact area in the taper connections were evaluated. Results Although the pull-off forces of the LDH with different-sized adapter sleeves were comparable, contact area decreased and adapter sleeve deformations increased (up to 283%) with an increasing adapter sleeve length. Moreover, the micromotions of LDH with adapter sleeves were up to 7-times higher, as compared with the standard femoral head without an adapter sleeve. Conclusion The present numerical study confirms that the assembly technique of LDH with adapter sleeves reveals increased micromotions compared with standard femoral head sizes. We could demonstrate that deviations of the stem trunnion geometry and improper surgical instructions led to worse mechanical stability of the taper connection.Publicationtype: Journal Article183 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The Influence of Cement Morphology Parameters on the Strength of the Cement-Bone Interface in Tibial Tray Fixation(2017-02-01); ; ; ; Background The strength of the cement-bone interface in tibial component fixation depends on the morphology of the cement mantle. The purpose of this study was to identify thresholds of cement morphology parameters to maximize fixation strength using a minimum amount of cement. Methods Twenty-three cadaveric tibiae were analyzed that had been implanted with tibial trays in previous studies and for which the pull-out strength of the tray had been measured. Specimens were separated into a group failing at the cement-bone interface (INTERFACE) and one failing in the bulk bone (BULK). Maximum pull-out strength corresponds to the ultimate strength of the bulk bone if the cement-bone interface is sufficiently strong. 3D models of the cement mantle in situ were reconstructed from computed tomography scans. The influences of bone mineral density and 6 cement morphology parameters (reflecting cement penetration, bone-cement interface, cement volume) on pull-out strength of the BULK group were determined using multiple regression analysis. The threshold of each parameter for classification of the specimens into either group was determined using receiver operating characteristic analysis. Results Cement penetration exceeding a mean of 1.1 mm or with a maximum of 5.6 mm exclusively categorized all BULK bone failure specimens. Failure strength of BULK failure specimens increased with bone mineral density (R2 = 0.67, P <.001) but was independent of the cement morphology parameters. Conclusion To maximize fixation strength, a mean cement penetration depth of at least 1.1 mm should be achieved during tibial tray cementing.Publicationtype: Journal Article129 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Does impaction matter in hip resurfacing? A cadaveric study(Churchill Livingstone, 2011); ; 11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Absence of surface roughness changes after insertion of one type of matte cemented femoral component during 2 to 15 years(Churchill Livingstone, 2003); ; ; Foerstér, Götz vonTheoretically, micromotion might occur even in stable cement-implant interface conditions. It was hypothesized that smoothing of the matte surfaces of femoral components because of abrasion or corrosion phenomena is a possible consequence of micromotion. Two new and 11 femoral components that were retrieved after 2 to 15 years of stable cement-implant interface conditions were inspected, investigated with light microscopy, and evaluated with surface roughness measurement by a profilometer. No surface changes were observed such as abrasion or corrosion phenomena except at the tip and the collar of the femoral components. The surface roughness was Ra = 1.0 and 1.1 μm in the new femoral components and Ra (mean) = 0.96 μm (range: 0.8-1.5 μm) in the retrieved components. There was no correlation between time in situ and surface roughness as confirmed by regression analysis. These data suggest that significant micromotion was not present at the studied interface.Publicationtype: Journal Article6 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Mismatched wear couple Zirconium oxide and Aluminium oxide in total hip arthroplasty : a case report(Elsevier, 2001); ; ; 4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Mismatched wear couple zirconium oxide and aluminum oxide in total hip arthroplasty(Churchill Livingstone, 2001); ; ; 4