Rudolf Marx

University Hospital RWTH Aachen , Aachen, North Rhine-Westphalia, Germany

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Publications (54)95.82 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This study evaluates a novel adhesive fixation technique to affix cortical bone fragments to osteosynthesis plates using common PMMA cement. This technique utilizes a new amphiphilic bone bonding agent adhering with both hydrophilic bone and hydrophobic PMMA cement. After in vitro biomechanical testing of the bonding strength with explanted bovine and rabbit calvarian bone samples, osteosynthesis plates with screw holes of 1.3 and 1.5 mm were placed on the cranial bone of New Zealand white rabbits and the bond strength of these plates was determined through tension tests. In vitro bond strengths of 19.8-26.5 MPa were obtained. Control samples, prepared without a bone bonding agent, exhibited bone bonding strengths <0.2 MPa. In vivo respective bond strengths at the cranium of the white rabbits were 2.5-4.1 MPa 2 weeks post surgery and 1.9-2.5 MPa 12 weeks after implantation. This new innovative fixation method can be envisioned for cases in which conventional fixation techniques of screws and plates are insufficient or not possible due to the bone or trauma conditions. The observed bonding strengths support implementing this technique in nonload bearing regions, such as the central midface or frontal sinus, facilitating immobilization until bone reunion is complete. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.
    Journal of Biomedical Materials Research Part A 07/2013; 101A(7). DOI:10.1002/jbm.a.34505 · 3.37 Impact Factor
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    ABSTRACT: CoCrMo alloys are contraindicated for allergy patients. For these patients, cemented or uncemented prostheses made of titanium alloy are indicated. Uncemented prostheses, however, have low primary retention, particularly the tibial components of knee joint prostheses because of the lack of a positive locking. Therefore, for knee replacement cemented CoCrMo prostheses may be suitable also for allergy sufferers if these are masked by ZrN or TiNbN layers. Alternatively the CoCrMo alloy may be replaced by high-strength oxide ceramics. For adhesion of bone cement to the ceramic surface, however, only inefficient mechanical retention spots are exposed as compared with a metal surface. Undercuts generated by corundum blasting, although highly efficient on a CoCrMo surface, are not such efficient centres on a ceramic surface due to its brittleness. Therefore, the mechanical component of retention is significantly reduced. When specific adhesion between bone cement and surface does not exist due to physical and chemical forces, the hydrolytic stability will be insufficient. Micromotions are promoted and early aseptic loosening is predictable. Silicoating of the ceramic surface will allow specific adhesion and can result in better hydrolytic stability of bonding. In order to evaluate the effectiveness of silicoating the bond strengths of blasted (mean size of corundum grains 50 µm) and silicate layered alumina-toughened zirconia (ATZ) surfaces were compared with "as fired" surfaces by utilising TiAlV probes (diameter 6 mm) for traction-adhesive strength testing. Samples machined out of CoCrMo alloy were utilised for reference. After preparing the samples for traction-adhesive strength testing (sequence: substrate, silicate and silane, protective lacquer [PolyMA], bone cement, TiAlV probe) they were aged up to 360 days at 37 °C in Ringer's solution. The bond strengths observed for all ageing intervals were well above 20 MPa and much higher and more hydrolytically stable for blasted and silicate-layered compared with "as fired" ATZ samples. Silicoating may be effective for achieving a high initial bond strength of bone cement on surfaces of oxide ceramics and also suitable to stabilise bond strength under hydrolytic conditions as present in the human body. Activation by low grain size corundum (mean grain size 50 µm) seems to be effective for activation without deteriorating the bending strength of the ceramics investigated. Due to the proposed layer system migration, micromotions and debonding should be widely reduced or even eliminated.
    Zeitschrift fur Orthopadie und Unfallchirurgie 02/2012; 150(1):40-7. DOI:10.1055/s-0031-1280249 · 0.62 Impact Factor
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    ABSTRACT: In the treatment of midface fractures, the fragments are immobilized using screws and plates for osteosynthesis until reunion has occurred. This method involves drilling holes for the insertion of the screws, which can be associated with additional fracturing of the corresponding bone owing to the complex architecture and thin layers of facial bone. To alleviate this problem, new adhesive techniques for fixing the plates for osteosynthesis have been investigated, mitigating the detrimental effects of screw hole drilling. In the present experimental study, the strength of this adhesive bond and its resistance to hydrolysis were investigated. To determine the adhesive bonding strength, a tension test was implemented. Osteosynthesis plates with screw holes 1.3 mm in diameter were fixed to cortical bone samples of bovine femur using ultraviolet (UV) light-curing polymethylmethacrylate bone cement. To facilitate bonding, the surface of the bone was conditioned with an amphiphilic bonding agent before cementing. UV light curing was implemented using either a conventional UV unit, such as is used in dentistry, or with a specialized UV unit with a limited emission spectrum but high luminosity. Reference control samples were prepared without application of the bone bonding agent. After this procedure, the samples were stored for 1 to 7 days at 37°C submerged in 0.9% saline solution before being subjected to the tension test. Without the bone bonding agent, the bonding strength was 0.2 MPa. The primary average bonding strength at day 0 was 8.5 MPa when cured with the conventional UV unit and 14 MPa for the samples cured with the specialized UV unit. An almost constant average bond strength of 8 and 16 MPa was noted for all samples stored up to 7 days after curing with the conventional and specialized UV unit, respectively. With the development of a new bone bonding agent, a method is now available to promote the bonding between the hydrophilic bone surface and the hydrophobic polymethylmethacrylate bone cement by creating an interlayer that is beneficial for adhesion. In the present in vitro study, the strength of this bond and its resistance to hydrolysis were investigated. This new method could have clinical bearing in cases in which conventional fixation with screws and plates is limited, such as can occur in comminuted fractures. The observed average bonding strengths of 8 to 16 MPa support the implementation of this technique in nonload-bearing regions such as the midface, facilitating immobilization until the bone reunion is complete.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 10/2010; 68(12):3028-33. DOI:10.1016/j.joms.2009.04.024 · 1.28 Impact Factor
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    ABSTRACT: To obtain scientific information on the loss of stability of tibias after removal of bone grafts, we performed a comparative study of 15 freshly preserved adult cadavers to determine the axial breaking loads of the operated and nonoperated tibial heads. From all cadavers, 1 tibia was randomly selected from which the maximum possible amount of cancellous bone was harvested. The respective contralateral side remained untouched. After maceration, the proximal tibias of each cadaver were removed bilaterally and adjusted to precisely equal lengths. Using a Zwick universal testing machine, the tibial heads were loaded by an axial force until fracture. As the final breaking load, the force value was recorded when the first distinct decrease in the feed-force curve was observed. To compare the mean breaking loads of the operated and nonoperated control tibias, a t test for related samples at P = .05 was used. The mean breaking load for the donor tibias was 3,767 N and was significantly lower than that of the control side with an average of 5,126 N. This finding was independent of age and gender. Bone removal from the proximal tibia leads to a significant reduction of the axial load capacity. Therefore, we recommend partial loading of up to one half of the body weight during the first postoperative week. For an additional 5 weeks, patients should bear their full body weight on the affected leg only when walking normally and on flat ground.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 01/2010; 68(1):60-7. DOI:10.1016/j.joms.2009.03.058 · 1.28 Impact Factor
  • Zeitschrift fur Orthopadie und Unfallchirurgie 03/2009; 147(02):175-182. DOI:10.1055/s-0029-1185456 · 0.62 Impact Factor
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    ABSTRACT: For cemented hip prostheses, all requirements can be fulfilled by using forged Co/Cr/Mo stems. Co/Cr/Mo alloys, however, are contraindicated for allergy sufferers. For these patients, a cemented prosthesis made of titanium (alloy) would be indicated. Cemented stems from titanium (alloy), depending on the geometry of the prosthesis and its specific surface texture, however, may have loosening rates which are clinically not tolerable. In comparison to Co/Cr/Mo alloys, the greater roughness in conjunction with lesser abrasion resistance of titanium-based alloys leads to high loosening rates caused by abrasion. On the other hand, the greater surface roughness permits good mechanical retention of bone cement to the surface. Good mechanical retention enhances migration behaviour and reduces micromotions. However, there is no stable hydrolytic bond between bone cement and metallic surface; intermediate-term debonding between metal and bone cement is predictable. This debonding results in relative movements, consequently in wear particles which have their origin both from the rough metallic surface and from the PMMA cement. The roughness of the metallic surface operates as emery and with that, a rubbing wear from the PMMA. For the above reasons, a low or moderate roughness is essential for easily abradable implants such as shafts made of titanium (alloy) because low roughness provides a fail-safe running function in case of debonding. Thus, one must allow for inappropriate migration behaviour accompanied by greater micromotions due to insufficient mechanical retention in the case of low roughness. This can be accomplished by a silicate layer coating applied to the metal shaft surface via electrochemical "ECD" or physical vapour deposition "PVD". For analysis, specimens (screws for pull-out, cones for push-out tests) were sand-blasted, so that roughnesses between Ra = 0.8 microm (Rz = 4 microm) and Ra = 2.0 microm (Rz = 9 microm) were generated. The bond strengths observed in tensile tests for roughnesses of Ra = 1.7 mm were always well above 25 MPa for all periods of hydrolytic load. Therefore, the investigation shows that surfaces of moderate roughness (Ra = 1.7 microm), however coated, provide a steady retention. Cave-in and micromotions should widely be prevented. The abrasion, which is a consequence of and reason for debonding and loosening at the same time, should be avoidable if the bonding of cement on the metallic shaft is stabilised with the help of a suitable chemical bond system.
    Zeitschrift fur Orthopadie und Unfallchirurgie 01/2009; 147(2):175-82. · 0.62 Impact Factor
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    ABSTRACT: Even following the introduction of the "third generation" cementing technique, an improvement of the fixation of the acetabular component similar to that of the femoral has not been shown in clinical studies. The goal of the present study was to achieve a better stability with the use of an amphiphilic bonder while preserving the mechanically important subchondral sclerosis. In a total of 20 sheep, a cemented total hip replacement was implanted. In the treatment group (n = 10), the implantation was carried out following surface conditioning of the acetabular bed with an amphiphilic bonder. All the sheep were followed for 9 months. To assess the biocompatibility, the osseous ingrowth at the cement-bone interface was depicted with the help of an in vivo fluorescent marking of the osteoblasts. Additionally, conventional radiographs were obtained over the course of treatment. Finally, the ovine pelvic regions were split following a standardized technique allowing for histological evaluation of the cement-bone interfaces. The acetabular components of the treatment group revealed a stable cement-bone compound. In the control group, the implants were easily dislodged from their beds. This finding was consistent with the radiological and histological results, which had revealed increased, progressive lytic radiolucent lines and the interposition of fibrous tissue at the cement-bone interface in the control group compared to the treatment group. The bonder was biocompatible. Following the application of the bonder, the cemented acetabular components revealed an improved stability without signs of inflammation or neoplasia in a viable acetabular osseous bed. With the help of this technique, the in vivo longevities of cemented acetabular components can be increased in the clinical setting without sacrificing the biomechanical relevant subchondral sclerosis.
    Archives of Orthopaedic and Trauma Surgery 08/2008; 128(7):701-7. DOI:10.1007/s00402-007-0408-6 · 1.36 Impact Factor
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    ABSTRACT: The aseptic loosening of cemented total hip and knee arthroplasties is still an unsolved problem. In this regard, the hydrolytic resistance in the metal-to-bone cement interface is of major importance. Cemented pretreated femur stems and tibia components coated by means of a silica/silane interlayer system were dynamically loaded with the help of a hip and knee simulator similar to DIN ISO Norm. After loading, the components were microscopically analysed concerning both debonding in the metal-to-bone cement interface and cement mantle defects. These data were matched with uncoated components. Unloaded coated and uncoated femur and tibia components acted as controls. Compared with uncoated components, the pretreated and coated ones yielded a significant reduction in cement defects as well as of debonding in the metal-to-bone cement interface. Using the silica/silane interlayer system for cemented femur and tibia components, hydrolytic debonding in the metal-to-bone cement interface with following cement mantle failure can be reduced. This could help increase the long-term stability of the metal-to-bone cement compound, with decreased aseptic loosening.
    Der Orthopäde 04/2008; 37(3):240-4, 246-50. · 0.67 Impact Factor
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    ABSTRACT: HintergrundDie aseptische Lockerung von zementierten Hüft- und Knieendoprothesen ist ein aktuell ungelöstes Problem. Diesbezüglich ist unter anderem eine hydrolysestabile Verbundfestigkeit der Grenzschicht Metall/PMMA (Polymethylmethacrylat) von entscheidender prognostischer Bedeutung. Material und MethodikMittels Silikatisierung/Silanisierung beschichtete Femurschaft- und Tibiaplateauendoprothesen wurden in „Kunstknochen“ zementiert implantiert und nach DIN-ISO-Norm belastet. Nach dynamischer Belastung erfolgte die auflicht- und fluoreszenzmikroskopische Grenzschicht- und Zementmantelanalyse. Unbeschichtete Endoprothesen dienten als Kontrollgruppen. ErgebnisseDie silikatisierten/silanisierten femoralen und tibialen Endoprothesen zeigten verglichen mit den unbeschichteten eine statistisch hoch signifikante Reduktion hinsichtlich Spalt- und Rissbildung in der Grenzschicht Metall/PMMA sowie im Zementmantel selbst. SchlussfolgerungDurch die silikatisierte/silanisierte Implantatoberflächenbeschichtung von zementierten Femurschaft- und Tibiaplateauendoprothesen kann ein hydrolytisches Debonding in der Grenzschicht Metall/PMMA mit konsekutiver Zementmantelzerrüttung vermieden werden. Dieses könnte eine längerfristige Stabilität des Metall-PMMA-Verbundes mit reduzierter mechanischer Lockerungsrate bewirken. BackgroundThe aseptic loosening of cemented total hip and knee arthroplasties is still an unsolved problem. In this regard, the hydrolytic resistance in the metal-to-bone cement interface is of major importance. MethodsCemented pretreated femur stems and tibia components coated by means of a silica/silane interlayer system were dynamically loaded with the help of a hip and knee simulator similar to DINISONorm. After loading, the components were microscopically analysed concerning both debonding in the metal-to-bone cement interface and cement mantle defects. These data were matched with uncoated components. Unloaded coated and uncoated femur and tibia components acted as controls. ResultsCompared with uncoated components, the pretreated and coated ones yielded a significant reduction in cement defects as well as of debonding in the metal-to-bone cement interface. ConclusionUsing the silica/silane interlayer system for cemented femur and tibia components, hydrolytic debonding in the metal-to-bone cement interface with following cement mantle failure can be reduced. This could help increase the long-term stability of the metal-to-bone cement compound, with decreased aseptic loosening.
    Der Orthopäde 03/2008; 37(3):240-250. DOI:10.1007/s00132-008-1198-4 · 0.67 Impact Factor
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    ABSTRACT: The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market. The adhesive bonding strengths were measured using tension tests. For this, metal plates with 2.0 mm diameter screw holes were cemented with PMMA bone cement to cortical bovine bone samples from the femur diaphysis. The bone was conditioned with an amphiphilic bone bonding agent prior to cementing. The samples were stored for 1 to 42 days at 37 degrees C, either moist or completely submerged in an isotonic NaCl-solution, and then subjected to the tension tests. Without the bone bonding agent, the bonding strength was close to zero (0.2 MPa). Primary stability with bone bonding agent is considered to be at ca. 8 MPa. Moist storage over 42 days resulted in decreased adhesion forces of ca. 6 MPa. Wet storage resulted in relatively constant bonding strengths of ca. 8 MPa. A new amphiphilic bone bonding agent was developed, which builds an optimizied interlayer between the hydrophilic bone surface and the hydrophobic PMMA bone cement and thus leads to adhesive bonding between them. Our in vitro investigations demonstrated the adhesive bonding of PMMA bone cement to cortical bone, which was also stable against hydrolysis. The newly developed adhesive fixing technique could be applied clinically when the fixation of osteosynthesis plates with screws is impossible. With the detected adhesion forces of ca. 6 to 8 MPa, it is assumed that the adhesive fixation system is able to secure bone fragments from the non-load bearing midfacial regions in their orthotopic positions until fracture consolidation is complete.
    BioMedical Engineering OnLine 02/2008; 7:16. DOI:10.1186/1475-925X-7-16 · 1.75 Impact Factor
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    ABSTRACT: The mechanical properties of acrylic bone cements are an important factor in determining an efficient load transmission between prosthesis and bone to guarantee the long-term stability in cemented hip arthroplasty. Palacos and Refobacin Palacos specimens from 21 aseptically loosened femoral compoments of cemented hip arthroplasties manufactured by the first to third generation cementing technique have been mechanically tested in a standardised four-point bending test (ISO 5833). In vitro manufactured Palacos and Refobacin Palacos specimens served as a control group. The fatigue fracture surfaces were morphologically analysed with light microscopy. Under in vitro conditions manufactured specimens had higher values of bending strength, with the exception of blood contaminated ones, compared to ex vivo specimens. Ex vivo specimens of the second and third generation cementing technique had higher values than specimens of the first generation. Acrylic bone cements are subjected to a multifactorial material fatigue in vivo. Here, the art and quality of cementing technique is of eminent importance in determining the long-term stability of cemented hip arthroplasty.
    Zeitschrift fur Orthopadie und Unfallchirurgie 01/2008; 146(1):99-107. DOI:10.1055/s-2007-989324 · 0.62 Impact Factor
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    ABSTRACT: Hydrolytic debonding of the metal-cement interface is one of the main reasons for aseptic loosening in cemented hip arthroplasty. BiContact femur stems (CoCrMo-/TiAl6V4-alloy) were coated by a silica/silane interlayer coating system. The stems were cemented into artificial femurs. The cyclical loading (DIN ISO 7206-4) was performed within a hip-simulator. Uncoated stems (CoCrMo-/TiAl6V4-alloy) were prepared and loaded the same way. After loading, the metal-cement and the bone-cement interfaces were analysed. Unloaded uncoated and unloaded coated BiContact stems served as a control. The coated loaded stems showed a significant reduction in debonding and cement failure (P < or = 0.05). A high correlation was documented between debonding and cement failure (rSpear> or = 0.9). There was no significant difference between CoCrMo- and TiAl6V4-stems (P > or = 0.05). The silica/silane coating significantly decreased hydrolytic debonding at the metal-bone cement interface with consecutively less cement failure.
    Archives of Orthopaedic and Trauma Surgery 11/2007; 128(8):773-81. DOI:10.1007/s00402-007-0463-z · 1.31 Impact Factor
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    ABSTRACT: INTRODUCTION The long-term stability in cemented hip arthroplasty depends not only on the mechanical properties of the acrylic bone cements but also on an improvement of cementing techniques. The bending strengths of 15 commonly used bone cements (CMW 3 Gentamycin; CMW 3; Refobacin Palacos R; Palacos R; Palamed G; Palamed; Cerafixgenta; Cerafix; Duracem; Simplex Tobramycin; Simplex P; Versabond; Sulcem; Sulcem 3 Genta; Copal) have been mechanically tested in a standardised in vitro four-point bending test (ISO 5833). The fatigue fracture surfaces were morphologically analysed with light microscopy. The highest values of bending strength were found in vacuum mixed specimens cured under pressure. The lowest values of strength were seen in with blood contaminated specimens. Fatigue cracks were often initiated from air bubbles or other inclusions such as antibiotics or blood in the bone cement. The present in vitro study highlights the supposition that the quality of the cementing technique is of eminent importance in determining the long-term stability of cemented hip arthroplasties.
    Zeitschrift fur Orthopadie und Unfallchirurgie 09/2007; 145(5):579-85. DOI:10.1055/s-2007-965666 · 0.62 Impact Factor
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    ABSTRACT: One of the main causes of cup loosening in cemented total hip replacement is the lack of a hydrolysis stable compound between the hydrophobic bone cement and the hydrophilic acetabular bone stock. Thus, the long-term adhesive strength between bone and bone cement is decreased resulting in premature aseptic loosening. Accordingly, an amphiphilic bonding system was developed to prevent hydrolytic debonding in the interface bone-to-bone cement. Polyethylene cups were cemented in cadaver sheep hips. The hips were prepared with (n = 10) a multilayer bonding system as well as with an improved monolayer bonding system with (n = 10) and without (n = 10) UV-light hardening. The hips were dynamically loaded (10(6) cycles; 3 Hz; upper/lower load 1,500/200 N) and afterwards turned out with a defined strength to determine the interface compound strength. Dynamically loaded cemented cups without using the bonding system (n = 10) function as a control group. The interface adhesive strength improved significantly by a factor of 1.9 (using the multilayer bonding system) compared to the unconditioned ones (P < or = 0.05); for the monolayer bonding system without (with) UV-light hardening the compound strength was 11.9-fold (> or =22.2-fold) higher (P < or = 0.001). The bonding system significantly improves the adhesive strength between bone and bone cement in cemented cup arthroplasty.
    Archives of Orthopaedic and Trauma Surgery 08/2007; 127(6):409-16. DOI:10.1007/s00402-007-0340-9 · 1.31 Impact Factor
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    ABSTRACT: Cemented femoral stems have shown decreased longevity compared to cementless implants in hip revision arthroplasty. The aim of this study was to evaluate the effect of an amphiphilic bonder on bone cement stability in a biomechanical femur expulsion test. A simplified hip simulator test setup with idealised femur stem specimens was carried out. The stems were implanted into bovine femurs (group 1: no bonder, n=10; group 2: bonder including glutaraldehyde, n=10; group 3: bonder without glutaraldehyde, n=10). A dynamic loading (maximum load: 800 N; minimum load: 100 N; frequency: 3 Hz; 105 cycles) was performed. Subsequently, the stem specimens were expulsed axially out of their implant beds and maximum load at failure was recorded. The static controls showed a mean maximum load to failure of 4123 N in group 1, 8357.5 N in group 2 and 5830.8 N in group 3. After dynamic loading, the specimens of group 2 reached the highest load to failure (8191.5 N), followed by group 3 (5649.5 N) and group 1 (3462 N), respectively. In group 2, we observed nine periprosthetic fractures at a load of 8400 N without signs of interface loosening. Application of an amphiphilic bonder led to a significant improvement of bonding stability, especially when glutaraldehyde was added to the bonder. This technique might offer an increased longevity of cemented femur revision stems in total hip replacement.
    Biomedizinische Technik 02/2007; 52(6):391-7. DOI:10.1515/BMT.2007.064 · 2.43 Impact Factor
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    ABSTRACT: For the prognosis and long-term stability of an implant, for example a hip- or knee-implant, the anchorage to the bone is of critical importance. Normally for this anchorage bone cement is used, which achieves sufficient retention to spongious bone structure. If there is the need for osteosynthesis of midfacial fractures for surgical therapy, in some situations it would be clinically preferable to fix the reconstruction plates without the usual system using screws. This is the aim of the new adhesive fixing technology which is presented in this article. The structure of bone in midface, however, is cortical and such a smooth surface will allow only insufficient retention forces between bone and bone cement. In order to obtain a good adhesion at cortical bone nevertheless, we have to apply a bone bonding agent similar to techniques used in dentistry, which are based on dentin bonding agents, because there are different wetting properties of the hydrophilic bone and the hydrophobic bone cement monomers. Determination of achievable bond strength was done in a tension test ex vivo. Reconstruction plates were fixed with bone cement at bovine bone conditioned with a bone bonding agent developed for this field of application. With bond strengths up to 6 Mpa it is assumed that an adhesive fixation of reconstruction plates at cortical bone structure is possible using the developed amphiphilic bone bonding agent.
    Materialwissenschaft und Werkstofftechnik 02/2007; 38(2):178 - 180. DOI:10.1002/mawe.200600100 · 0.43 Impact Factor
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    ABSTRACT: Cemented revision of femoral components in total hip arthroplasty has shown high rates of early loosening due to reduced micro- and macroretention of the cement to the endostal bone stock. Enhanced stability can be reached by an amphiphilic bonder, which offers a covalent bonding of the hydrophobic cement to the hydrophilic bone. The aim of this study is to evaluate the biocompatibility of such a bonder and its effects on the mechanical stability of cemented hip arthroplasty stems in vivo. Total cemented hip arthroplasties were performed in 20 sheep. In the verum group (n = 10) the implant bed was preconditioned by application of the bonder prior to femoral stem implantation. To study the biocompatibility around the bone-cement interface fluorescent marking of osteoblasts was applied in vivo throughout the observation period of 9 months. Native X-rays of the hip joints were obtained immediately after implantation and after euthanasia. The bone-cement interface was examined histologically. All stems of the verum group showed firm bonding of cement to bone in manual testing, while in 7 of the 10 controls the stems with adherent cement could be easily pulled out off the bony implant bed. This was coherent with significantly higher rates of progredient radiolucent lines and soft-tissue interpositions between bone and cement in the control group. The bonder was biocompatible. When preconditioned with an amphiphilic bonder, cemented stems showed a markedly higher adhesive strength to the cancellous bone without signs of inflammation or neoplasia. This procedure might offer enhanced longevity of cemented femoral revision stems in hip arthroplasty.
    Zeitschrift fur Orthopadie und Unfallchirurgie 01/2007; 145(4):476-82. · 0.62 Impact Factor
  • Zeitschrift fur Orthopadie und Unfallchirurgie 01/2007; 145(4):476-482. DOI:10.1055/s-2007-965486 · 0.62 Impact Factor
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    ABSTRACT: Aseptic loosening of tibial components due to degradation of the interface between bone cement and metallic tibial shaft component is still a persistent problem, particularly for surface-cemented tibial components. The surface cementation technique has important clinical meaning in case of revision and for avoidance of stress shielding. This study was done to prove crack formation in the bone cement near the metallic surface when this is not coated. We propose a newly developed coating process by SiOx-PVD layering to avoid crack formation. A biomechanical model for a vibration fatigue test was done to prove that crack formation can be significantly reduced in the case of coated surfaces. It was found that coated tibial components showed a highly significant reduction of cement cracking near the metal/bone cement interface (p < 0.01) and a significant reduction of gap formation in the metal-to-bone cement interface (p < 0.05). Coating dramatically reduces hydrolytic- and stress-related crack formation at the prosthesis metal/bone cement interface. This leads to a more homogenous load transfer into the cement mantle which should reduce the frequency of loosening in the metal/bone cement/bone interfaces. With surface coating of the tibial component it should become possible that surface-cemented TKAs reveal similar loosening rates as TKAs both surface- and stem-cemented. This would be an important clinical advantage since it is believed that surface cementing reduces metaphyseal bone loss in the case of revision and stress shielding for a better bone health.
    Biomedizinische Technik 02/2006; 51(2):95-102. DOI:10.1515/BMT.2006.017 · 2.43 Impact Factor
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    ABSTRACT: For esthetical and biomechanical reasons root canal posts made of fibre-reinforced composite (FRC) have gained an important role in clinical application. Additionally, in contrast to metal or ceramic posts, FRC-posts offer the option of removal. Prior to adhesive placement of FRC-posts the root canal dentin of the non vital tooth and the post surface have to be preconditioned. Up to now the post preconditioning has to be proceeded in the chair side technique. This leads to an additional time expense in the clinical treatment schedule. Also a certain risk of errors in application during chair side conditioning procedure is of concern. Modern PVD-technologies can help to make the treatment by the manufacturer well in advance of the clinical use more efficient and reliable, as well as saving clinicians valuable chair-time. For this reason the apical surfaces of the posts were intensively cleaned and activated, PVD-layered and coated by a conserving transparent layer. This coating has the meaning to protect the surface against environmental contamination and allows the try-in of the posts without any risk of damage of the preconditioned surface. To prove the stability of the layer system under simulated clinical conditions pull out tests after 180 days'storage in physiological saline solution have been performed.
    Schweizer Monatsschrift für Zahnmedizin = Revue mensuelle suisse d'odonto-stomatologie = Rivista mensile svizzera di odontologia e stomatologia / SSO 02/2006; 116(10):992-9.

Publication Stats

614 Citations
95.82 Total Impact Points

Institutions

  • 2003–2010
    • University Hospital RWTH Aachen
      • • Division of Dental, Oral and Maxillofacial Surgery
      • • Department of Orthodontics
      Aachen, North Rhine-Westphalia, Germany
  • 1999–2009
    • RWTH Aachen University
      • • Department of Prosthodontics and Dental Materials
      • • Institute of Mineral Engineering
      Aachen, North Rhine-Westphalia, Germany
  • 2006
    • Ludwig-Maximilian-University of Munich
      • Department of Dental Prosthetics
      München, Bavaria, Germany
  • 2005
    • Orthopädische Universitätsklinik Friedrichsheim
      Frankfurt, Hesse, Germany