No abstract

We present the early results of 142 uncemented femoral stem revisions using the modular MRP-Titan system. There were 70 cases with marked preoperative femoral bone defects (Paprosky type 2C and type 3); and bone grafts were used in 31 cases. At a mean follow-up of 2.3 years five cases were re-revised due to dislocation and two due to aseptic loosening. The mean Harris hip score improved from 37.4 preoperatively to 92.4. In 122 cases progressive bone regeneration on X-ray was seen; and no further osteolysis was observed.

For patients suffering from allergies to nickel, chrome and cobalt, titanium implants are the implants of choice. Nevertheless, titanium implant sensitivity has been reported in the form of "allergies" and an increasing number of patients are confused. This paper aims to use spectral analysis as a diagnostic tool for analyzing different titanium implant alloys in order to determine the percentage of the alloy components and additions that are known to cause allergies. Different materials, such as sponge titanium, TiAl6Nb7, Ti21SRx, TiAl6V4 %. This paper demonstrates that all the investigated implant material samples contained a low but consistent percentage of components that have been associated with allergies. For example, low nickel contents are related to the manufacturing process and are completely dissolved in the titanium grid. Therefore, they can virtually be classified as "impurities". Under certain circumstances, these small amounts may be sufficient to trigger allergic reactions in patients suffering from the corresponding allergies, such as a nickel, palladium or chrome allergy.

Given the encouraging results with the MRP Titan Revision Stem, the principle of uncemented diaphyseal fixation appears to solve most of the technical problems in cases of significant bone loss and obviously offers good preconditions for bony restoration.

Ceramic-on-ceramic coupling is thought to be a durable alternative to metal- or alumina-on-polyethylene pairing. No evidence exists suggesting superior clinical and radiological results for hydroxyapatite-coated stems versus uncoated stems. The aim of this study is to report the performance of an alumina-on-alumina bearing cementless total hip arthroplasty and to compare stems with a tapered design with and without hydroxyapatite coating. We prospectively analysed the results of cementless tapered femoral stems (40 hydroxyapatite-coated versus 22 uncoated stems), a metal-backed fibre mesh hydroxyapatite-coated socket and alumina-on-alumina pairing. Of 75 hips studied, 62 were available for follow-up (mean of 10.5 years after surgery). The average Harris hip score was 90. Only one hydroxyapatite-coated stem was revised for aseptic loosening. One instance of non-progressive osteolysis was detected around a screw of a cup. All other components showed radiographic signs of stable ingrowth. Hydroxyapatite coating of the stem had no significant impact on the clinical or radiological results. Total hip arthroplasty with the presented implant and pairing provides a durable standard for all patients requiring hip joint replacement against which all newer generations of cementless implants should be judged.

Compressive residual stresses are commonly introduced into the near-surface regions of morse taper junctions of modular hip endoprostheses to prolong fatigue life. An increasing number of publications report that contamination of shot-peened surfaces can lead to enhanced corrosion and third body wear. This study evaluates deep rolling of titanium alloy rods as a possible alternative to shot peening. Ten rods of Ti6Al7Nb alloy with a diameter of 15 mm were deep rolled with various rolling parameters. The resulting surface topography and residual contamination was analyzed using a scanning electron microscope (SEM). The near-surface residual stress states after deep rolling were characterized by means of X-ray diffraction. The roughness of the surfaces before deep rolling was about R(z) = 14 microm, and after deep rolling surface roughness values of R(z) 0.4-7.5 microm were achieved. The results of the SEM and EDAX analyses of the sample surface showed no evidence of surface contamination by particles or abrasion products caused by any process. At a pressure of 300 bar, compressive stress reached the maximum of -1150 MPa at a depth of 0.1 mm. Deep rolling thus allows a smooth and particle-free surface to be obtained and therefore shows promise as a surface treatment for mating surfaces of morse tapers in modular hip endoprostheses.

Titanium alloys -type (a+b) -like Ti6Al7Nb or Ti6Al4V are widely used in cementless total hip arthroplasty due to their lower modulus, biocompatibility and enhanced corrosion resistance in comparison to Stainless Steel or Cobalt-Chromium implant materials. Several articles report about atrophy of the proximal femur in cases where long stems with a big diameter made of (a+b) Titanium alloys with a relatively high value of the Youngs' Modulus (110 GPa) in comparison to the Youngs' Modulus of cortical bone (15 -25 GPa) have been implanted using a prosthesis design with distal anchorage technique. Meanwhile several implant manufacturers have developed a new group of biocompatible Beta-Titanium alloys with a lower Youngs' Modulus around 70 GPa. This article gives an overview of the current status of available low modulus Titanium alloys including their mechanical characteristics and future developments.Keywords: Titanium alloy, Youngs' Modulus, total hip arthoplasty, atrophy Titanlegierungen vom a+b-Typ wie TiAl6Nb7 oder TiAl6V4 werden aufgrund der exzellenten Biokompatibilität, der Korrosionsresistenz und dem im Vergleich zu Implantatstahl oder CobaltChrom-Legierungen niedrigem E-Modul in der zementfreien Hüftendoprothethik verwendet. Mehrere Artikel berichten über die Atrophie des proximalen Femurs nach Implantation von Hüft-endoprothsenschäften, wenn Schäfte mit großem Durchmesser mit distaler Verankerung aus einer a+b-Titanlegierung verwendet wurden. Im Vergleich zu dem E-Modul von kortikalem Knochen von 15 -25 GPa ist der E-Modul bei den genannten Legierungen mit 110 GPa relativ hoch. Zwischenzeitlich haben mehrere Implantathersteller eine neue Gruppe von biokompatiblen b-Titanlegierungen mit einem deutlich niedrigeren E-Modul von etwa 70 GPa entwickelt. Dieser Artikel gibt einen Ü berblick über den gegenwärti-gen Stand von verfügbaren Titanlegierungen mit niedrigem E-Modul, deren mechanischen Eigenschaften und zukünftige Entwicklungen.

The low nickel content in the implant material results from the production process. The nickel atoms are in solid solution in the titanium lattice. Nickel allergic patients may develop hypersensitivity reactions even due to this low nickel content. Hence, this reaction may be falsely attributed to the titanium material itself. Measurements of ion concentration in the body are helpful for quantifying the maximum content of nickel in titanium materials for surgical implant applications. In addition, technical questions related to the production of nickel free titanium materials for allergic patients have to be solved.