Feasibility study of production of radioactive carbon black or carbon nanotubes in cyclotron facilities for nanobioscience applications

A feasibility study regarding the production of radioactive carbon black and nanotubes has been performed by proton beam irradiation. Experimental and theoretical excitation functions of the nuclear reaction (nat)C(p,x)(7)Be in the proton energy range 24-38 MeV are reported, with an acceptable agreement. We have demonstrated that sufficient activities of (7)Be radioisotope can be produced in carbon black and nanotube that would facilitate studies of their possible impact on human and environment.

Measurement techniques for tracer kinetic studies with stable isotopes of zirconium

Biokinetic models are used in radiation protection to assess internal radiation doses. Experiments with stable isotopes as tracers can be performed to obtain characteristic parameters of these models. Two methods for the measurement of zirconium isotopes in human biological samples are presented--thermal ionisation mass spectrometry (TIMS) and proton nuclear activation analysis (PNA). Descriptions include sample preparation, operating conditions, relative uncertainties and method detection limits as well as important properties of both methods.

Tribological characterization of surface-treated commercially pure titanium for femoral heads in total hip replacement: a feasibility study

Most noncemented total hip replacements combine a titanium alloy stem, a CoCrMo femoral head and an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. In spite of its nickel content of up to 1% and the resulting biocompatibility issues in some clinical situations, the higher cost and some difficulties in machining, CoCrMo alloy is preferred to titanium alloys thanks to its outstanding tribological properties, higher hardness and elastic modulus. Nowadays most of the heads of hip prostheses use CoCrMo as bearing material. The present study investigates the effect of various surface treatments and combinations of treatments, such as electrochemical oxidation (anodization), laser surface melting and barrel polishing, on the tribological properties of commercially pure grade 2 titanium. The aim of the study was to characterize surface treatments capable of improving the tribological properties of titanium surface to the same extent as CoCrMo. The tribological properties were characterized by multidirectional pin-on-flat screening wear tests, using UHMWPE pins as bearing surface. The experiments showed the possibility of improving the wear resistance of titanium to the degree of CoCrMo. Although further efforts will be required to optimize the treatments studied, the results are encouraging enough to warrant pursuing this direction of investigation.

[Allergic reaction to components of bone cement after total knee arthroplasty]

There are many reports about allergic reactions in association with total hip or knee arthroplasty. While most studies focus on allergic reactions to metallic components, only few reports exist about reactions to bone cement or its ingredients. We report about a patient who developed eczema at the knee and the lower leg one year after cemented TKR. Patch testing showed as potential causes contact allergic reactions to nickel and benzoylperoxide, an ingredient of the here used bone cement. The local and temporal association between onset of eczema and knee arthroplasty suggests a causal link. Benzoylperoxide as potential contact allergen in bone cement is so far almost neglected. The development of extended testing procedures and data collection should provide further information and better care of these patients. The development of special bone cements for patients with allergic diathesis is requested.

[Results of operative therapy of idiopathic clubfoot using a dorsomedial approach with soft tissue preparation "à la carte"]

INTRODUCTION

Several concepts have been published for therapy of idiopathic clubfoot. Actually the Cincinnati approach is the "gold-standard" in operative treatment of idiopathic clubfoot. Using this approach delayed wound healing and overcorrection are wellknown complications. During the last 30 years a dorsomedial approach is used in operative treatment of idiopathic clubfoot in our clinic. Using this approach a dorsal, medial and/or lateral release can be performed. Postoperatively a plaster cast is used. The following years a rigid therapy with orthosis and support is requested.

PATIENTS AND METHOD

Between June 1986 and December 2000 130 clubfoot operations with soft tissue release were performed. 119/130 (91 %) patients could be clinically and radiologically followed-up after a mean of 4.5 years (min: 2, max: 17) including 65.5 % male and 34.5 % female patients. Average age at time of operation was 7.6 months. The findings were classified according to Dimeglio. To evaluate the clinical results the score according to Laaveg and Ponseti was used. X-rays with load (a. p. and lateral view) were evaluated preoperatively and at follow-up for a. p. and lateral talocalcaneal angle, talometatarsal-I-angle, calcaneometatarsal-V-angle and the angle of the first ray. Additionally complications and recurrences were documented.

RESULTS

21.8 % of the feet were classified IV degrees , 39.5 % III degrees and 38.7 % II degrees according to Dimeglio. Recurrent clubfoot was found in 7.6 % of all cases. All angles showed a significant improve. At latest follow-up 95.6 +/- 9.2 points according to the score of Laaveg and Ponseti were achieved. Flat top talus was found in 37 cases.

CONCLUSION

The dorsomedial approach allows an excellent correction of clubfeet with a low rate of complications and recurrences in comparison to other studies.

Cyclotron production of 64Cu by deuteron irradiation of 64Zn

The short-lived (12.7h half-life) (64)Cu radioisotope is both a beta(+) and a beta(-) emitter. This property makes (64)Cu a promising candidate for novel medical applications, since it can be used simultaneously for therapeutic application of radiolabelled biomolecules and for diagnosis with PET. Following previous work on (64)Cu production by deuteron irradiation of natural zinc, we report here the production of this radioisotope by deuteron irradiation of enriched (64)Zn. In addition, yields of other radioisotopes such as (61)Cu, (67)Cu, (65)Zn, (69m)Zn, (66)Ga and (67)Ga, which were co-produced in this process, were also measured. The evaporation code ALICE-91 and the transport code SRIM 2003 were used to determine the excitation functions and the stopping power, respectively. All the nuclear reactions yielding the above-mentioned radioisotopes were taken into account in the calculations both for the natural and enriched Zn targets. The experimental and calculated yields were shown to be in reasonable agreement. The work was carried out at the Scanditronix MC-40 Cyclotron of the Institute for Health and Consumer Protection of the Joint Research Centre of the European Commission (Ispra site, Italy). The irradiations were carried out with 19.5 MeV deuterons, the maximum deuteron energy obtainable with the MC-40 cyclotron.

[Metallurgical differentiation of cobalt-chromium alloys for implants]

BACKGROUND

Cobalt Chromium alloys are used in cemented total hip or knee arthroplasty as well as in metal-on-metal bearings in total hip arthroplasty. An increasing number of publications report about (allergic) reactions to wear particles of Cobalt Chromium alloys. Reactions to nickel are more frequent in comparison to Cobalt or Chromium particles. It is well known that different kinds of Cobalt Chromium alloys contain different amounts of alloying elements; nevertheless. The aim of the current work was to compare the different Cobalt Chromium alloys according to ASTM F or ISO standards in respect to the different alloying elements.

MATERIAL AND METHODS

Co28Cr6Mo casting alloys according to ASTM F 75 or ISO 5832-4 as well as forging alloy types according to ASTM F 799 and ISO 5832 such as Co20Cr15W10Ni, Co35Ni20Cr, Fe40Co20Cr10Ni, Co20Cr20Ni, and Co28Cr6Mo were analyzed in respect to their element content of Co, Cr, Ni, Mo, Fe, W, and Mn.

RESULTS

In 1935 the Cobalt based alloy "Vitallium" Co30Cr5Mo basically used in the aircraft industry was introduced into medicine. The chemical composition of this alloy based on Cobalt showed 30 wt.% Chromium and 5 wt.% Molybdenum. The differentiation using alloy names showed no Nickel information in single alloy names.

CONCLUSION

The information given about different alloys can lead to an unprecise evaluation of histopathological findings in respect to alloys or alloying constituents. Therefore, implant manufacturers should give the exact information about the alloys used and adhere to European law, Euronorm 93/42/EWG.

[Residual particle free surfaces after shot peening in modular hip arthroplasty are feasible]

INTRODUCTION

Shot peening with steel balls is used for introduction of compressive stress in the production of morse taper junctions of modular hip endoprostheses. After this procedure, significant contamination with residual particles can be detected, which may lead to increased corrosion and third body wear. Additionally, the European norm EN 12010 requires surfaces free of residual particles. The aim of this study is to evaluate the effects of several cleaning procedures with regard to complying with EN 12010.

MATERIAL AND METHOD

The surfaces of 12 Ti6Al7Nb rods with a diameter of 15 mm was shot peened with steel balls (GS VERA, Fa. Würth, Bad Friedrichshall, Germany). A field emission scanning electron microscopy (SEM, LEO 1525) was used for the detection of residual particles on the surface of the rods with a backscattered electron detector. After SEM examination, one sample each was cleaned using shot peening with sugar or dry ice and 10 rods using a pH dependent cleaning procedure. After these cleaning procedures, the samples were again analysed with the SEM for residual particle contamination.

RESULTS

The surface of all rods showed a considerable contamination with steel particles after shot-peening with steel balls. After the cleaning procedure with dry ice or sugar steel contamination was lower, however, only the pH dependent cleaning procedure was able to achieve surfaces free of residual particles.

DISCUSSION

For smooth shot-peened surfaces in modular hip arthroplasty Euro Norm EN 12010 can be fulfilled using shot peening with steel balls followed by a pH dependent cleaning procedure.

A novel test method for evaluation of the abrasive wear behaviour of total hip stems at the interface between implant surface and bone cement

After total hip replacement, some cemented titanium stems show above-average early loosening rates. Increased release of wear particles and resulting reaction of the peri-prosthetic tissue were considered responsible. The objective was to develop a test method for analysing the abrasive wear behaviour of cemented stems and for generating wear particles at the interface with the bone cement.

By means of the novel test device, cemented hip stems with different designs, surface topographies and material compositions using various bone cements could be investigated. Before testing, the cemented stems were disconnected from the cement mantle to simulate the situation of stem loosening (debonding). Subsequently, constant radial contact pressures were applied on to the stem surface by a force-controlled hydraulic cylinder. Oscillating micromotions of the stem (± 250 μm; 3 × 106cycles; 5 Hz) were carried out at the cement interface initiating the wear process.

The usability of the method was demonstrated by testing geometrically identical Ti-6A1-7Nb and Co-28Cr-6Mo hip stems ( n = 12) with definite rough and smooth surfaces, combined with commercially available bone cement containing zirconium oxide particles. Under identical frictional conditions with the rough shot-blasted stems, clearly more wear particles were generated than with the smooth stems, whereas the material composition of the hip stems had less impact on the wear behaviour.

Optimisation study of α-cyclotron production of At-211/Po-211g for high-LET metabolic radiotherapy purposes

The production of no-carrier-added (NCA) alpha-emitter (211)At/(211g)Po radionuclides for high-LET targeted radiotherapy and immunoradiotherapy, through the (209)Bi(alpha,2n) reaction, together with the required wet radiochemistry and radioanalytical quality controls carried out at LASA is described, through dedicated irradiation experiments at the MC-40 cyclotron of JRC-Ispra. The amount of both the gamma-emitter (210)At and its long half-lived alpha-emitting daughter (210)Po is optimised and minimised by appropriate choice of energy and energy loss of alpha particle beam. The measured excitation functions for production of the main radioisotopic impurity (210)At-->(210)Po are compared with theoretical predictions from model calculations performed at ENEA.

Das Allergiepotenzial von Implantatwerkstoffen auf Titanbasis

AIM

The aim of this investigation is to evaluate the allergic potential of titanium and titanium alloys for surgical implant applications.

MATERIALS AND METHODS

Discs cut from rods supplied by five different titanium suppliers in several diameters were investigated. The samples were cp-Titanium as well as Ti6Al4 V and Ti6Al7Nb, 6 mm thick with a diameter of between 6 and 60 mm. The material was checked by optical spectral analysis.

RESULTS

In all samples except iodidtitanium, a Nickel content of 0.012-0,034 wt% could be detected.

CONCLUSION

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.

[Titanium deposits on the ceramic heads of dislocated total hip replacements]

INTRODUCTION

In cases of revision total hip replacement (THR) having acetabular titanium components with dislocations in the past, metallic deposits are frequently found on the ceramic heads. The aim of this study was to determine whether the metallic deposits increase surface roughness in definite areas.

MATERIALS AND METHODS

Ten ceramic heads of revised THR which showed metallic deposits were investigated. The patients suffered from one to six dislocations. The prosthesis lifetime ranged from 2 weeks to 12 years. Surface structure was investigated in a scanning electron microscope (LEO 1525), and the metallic deposits characterised by means of energy dispersive x-ray analysis (EDX).

RESULTS

In the area of the metallic deposits, titanium was detected by EDX. Edges with a significant increase in surface roughness were observed, partially accompanied by damage to the surface structure and loosening of Al(2)O(3) particles.

DISCUSSION

Titanium deposits increase surface roughness in definite areas, which probably causes wear to the ceramic-ceramic or ceramic-polyethylene articulations due to different roughness values and surface properties. Further investigations are necessary in order to determine the importance of these findings with respect to wear and loosening of total hip arthroplasty.

Restpartikelfreie raue Oberflächen nach Stahldrahtkornstrahlen in der Hüftendoprothetik / Residual particle free rough surfaces after rough blasting with steel grit in total hip arthroplasty

INTRODUCTION

Several shot peening and grit blasting techniques are used to modify the surface in the production of hip endoprostheses. A number of publications in maxillo- facial- surgery and orthopedic surgery demonstrated significant contamination on alumina blasted surfaces. Latest research studies suspected an association between surface contamination and early failure of endoprostheses associated with third body wear. Additionally, the European standard EN 12010 requires surfaces free of residual particles. The aim of this study is to evaluate the effects of rough blasting using steel grit followed by a pH dependent cleaning procedures with regard to complying with EN 12010.

MATERIAL AND METHOD

Ti6Al7Nb rods were rough blasted 1 time using steel grit ("Stahldrahtkorn", hardness: 56 HRC; R+K Draht GmbH, Leisnig). All blasting procedures were carried out with a special grit blasting device with direct pressure. One Ti6Al7Nb rod each was grit blasted with 3 and 4 bar pressure and 10 rods with 5 bar pressure. Surface roughness was measured by means of Mitutoyo- Surftest 301 three times before and after grit blasting. The mean value was calculated. A field emission scanning electron microscopy (SEM, LEO 1525) was used for the detection of residual particles on the surface of the rods with a backscattered electron detector.

RESULTS

By rough blasting using steel grit a mean roughness of 54,9 microm and a maximum roughness of 61,4 microm could be achieved. The surface of all rods showed a considerable contamination with steel particles after grit blasting. After the a pH- dependent cleaning procedure a residual particle free surface was detected in all samples.

DISCUSSION

The European standard EN 12010 can be fulfilled using rough blasting with steel grit followed by a pH dependent cleaning procedure.

[Surface characterization of Al2O3-blasted titanium implants in total hip arthroplasty]

INTRODUCTION

Shot peening and grit blasting techniques are used in several surface modifications for producing hip endoprostheses. Corund blasting techniques using highly pure Al2O3 particles to create a rough surface of titanium implants in cementless total hip arthroplasty achieve better osteointegration. An increasing number of publications in maxillofacial surgery and orthopedic surgery show that there is a significant contamination on corund-blasted surfaces. The latest research studies reported an effect of contaminant particles on early failure of endoprostheses associated with third body wear. The aim of our work was to evaluate the amount and particle size of Al2O3 on the implant surface.

MATERIAL AND METHOD

The surface of four different geometries (five parts each, ARR titanium acetabular reinforcement ring, anisotropic Vektor cup, Vektor titanium stem and modular MRP Titan stem) were analyzed with respect to Al2O3 particles. Grit blasting was performed with Al2O3 particles, Alodur SWSK, Fa. Treibacher. Field emission scanning electron microscopy (LEO 1525) was used for the detection of the Al2O3 particles at the implant surface with a backscattered electron detector. The particle size distribution as well as the average area of the covered surface was calculated with image analyzing software (analySIS, Soft Imaging System GmbH).

RESULTS

The surface of the anisotropic Vektor cup was contaminated at an average of 41.7+/-4.9%, the Vektor titanium stem at an average of 33.3+/-4.7%, the (MRP) Titan stem at an average of 30.6+/-4.2%, and the ARR titanium acetabular reinforcement ring at an average of 23.2+/-1.6 with Al2O3 particles over the whole surface orientated to the bone.

DISCUSSION

The results of this study clearly show that there is contamination of rough titanium surfaces with Al2O3 particles at an unexpectedly high percentage. With respect to third body wear in total hip arthroplasty, further studies are necessary to minimize contamination of roughened surfaces and maintain sufficient roughness for osteointegration.

Effect of surface finish on the osseointegration of laser-treated titanium alloy implants

It was the purpose of this study to examine the osseointegration of laser-textured titanium alloy (Ti6Al4V) implants with pore sizes of 100, 200, and 300 microm, specifically comparing 200-microm implants with polished and corundum-blasted surfaces in a rabbit transcortical model. Using a distal and proximal implantation site in the distal femoral cortex, each animal received all four different implants in both femora. The bone-implant interface and the newly formed bone tissue within the pores and in peri-implant bone tissue were examined 3, 6, and 12 weeks post-implantation by static and dynamic histomorphometry. Here we show that additional surface blasting of laser-textured Ti6Al4V implants with 200-microm pores resulted in a profound improvement in osseointegration, 12 weeks postimplantation. Although lamellar bone formation was found in pores of all sizes, the amount of lamellar bone within pores was linearly related to pore size. In 100-microm pores, bone remodeling occurred with a pronounced time lag relative to larger pores. Implants with 300-microm pores showed a delayed osseointegration compared with 200-microm pores. We conclude that 200 microm may be the optimal pore size for laser-textured Ti6Al4V implants, and that laser treating in combination with surface blasting may be a very interesting technology for the structuring of implant surfaces.

[Surface characterisation of shot peened implants with glas beads in total hip arthroplasty]

Alumina-blasting is used to create a rougher surface of Titanium implants in cementless total hip arthroplasty to achieve a better bony ingrowth. An increasing number of publications in maxillofacial surgery and orthopaedic surgery show that there is a significant contamination in Alumina blasted surfaces. Latest research published an effect of contaminant particles on early loosening of endoprostheses associated with third body wear. Due to our knowledge no previous study analysed surface contamination of hip endoprostheses with glass beads. Aim of our work was to evaluate the percentage of contaminated surface of hip endoprostheses with glass beads.

MATERIAL AND METHOD

The surface of 5 Ti-VPS sprayed Phoenix cups and 5 morse-taper-junctions of the MRP-Titan revision stem (Peter Brehm, Chirurgie Mechanik, Weisendorf) were analysed with respect to glass particles. Shot peening was performed with glass beads "BALLOTINI" MGL, Fa. Würth Strahlmittel. A field emission scanning electron microscopy (LEO 1525) was used for the detection of the glass-particles on the implant surface with a backscattered electron detector. The particle covering position was calculated by means of an imaging analyze software (analySIS, Soft Imaging System GmbH).

RESULTS

The surface of the Ti-VPS sprayed Phoenix cups showed a contaminated area at a mean of 9.2 +/- 1.3 %, morse-taper-junctions of the MRP-Titan stem at a mean of 9.6 +/- 2.1 % with glass particle contact.

DISCUSSION

The results of this study clearly show that there is a contamination of shot pinned Titanium surfaces with glass particles in a significant percentage. With respect to third body wear in total hip arthroplasty further studies are necessary to minimize contamination.

Bilaterale umschriebene Osteolyse nach zementierter H�fttotalendoprothesenimplantation

The incidence of focal progressive osteolysis after THR is about 8% and 56%. Most often osteolysis is correlated with macrophage-induced osteoclastic bone resorption as a sequel of inflammatory reaction to wear particles. Recently these findings were published in respect to allergic reactions to implants, their alloying constituents, or bone cement. We report about a patient who developed bilateral localized osteolysis just below the cement mantle 5 years after cemented THR with a Müller straight stem. In the middle of the osteolysis small fragments of bone cement could be detected. Epicutaneous testing showed no reaction against cobalt, chromium, or nickel. Further epicutaneous testing in respect to ingredients of the bone cement were refused by the patient. Histological examination revealed a histiocytic reaction to wear particles and surrounding giant cells. To our knowledge, this is the first case of bilateral localized osteolysis after cemented total hip replacement. Taking all results of the current case into account, it is still unclear if a lymphocytic allergic contact reaction did contribute to the sequel of this case. Reports of immunologically induced incompatibility to components of bone cement, the development of extended testing procedures, and further scientific research should contribute to optimizing the care of patients.

Der modulare MRP-Titanrevisionsschaft in der Revisionsendoprothetik des H�ftgelenks

In revision arthroplasty of the hip, femoral defects and fractures must be bridged by a long stem. The implant has to be adapted exactly to the diameter of the cortical tube and has to be placed distally beyond the pathologic area. The titanium modular revision prosthesis (MRP) stem consists of the titanium alloy Ti6Al7Nb and is offered in various diameters, lengths, and special devices, which allows individual and load-stable reconstruction. The aim of the current study is to scrutinize first clinical and radiological results of the titanium MRP revision stem in revision arthroplasty of the hip. We report the midterm results of 130 non-cemented revision arthroplasties of the hip using the titanium MRP revision stem with a mean follow-up of 2.9 years (minimum: 1 year, maximum: 8 years), including 56 men and 74 women. The indication for revision arthroplasty was aseptic loosening of the cup and stem in 94 cases, loosening of the stem in 17 cases, reimplantation in a Girdlestone situation in 11, and periprosthetic fractures in 8 cases. The Harris hip score improved from 50.9+/-24.6 preoperatively to 88.5+/-11.5 postoperatively. The score according to Merle d'Aubigné improved from 9.8+/-4.0 preoperatively to 15.2+/-2.8 postoperatively. We found three recurrent dislocations, two lesions of the sciatic nerve, three cases of persisting deep infection, two periprosthetic fractures, and one case of subsidence of the stem of 2 cm required revision of the MRP stem. Atrophy of the proximal femur was visible in all cases with a stem diameter >17 mm (39/130). Stable primary fixation was achieved in 129 of 130 cases. The titanium MRP revision has proved to be a very reliable implant in cementless revision arthroplasty of the hip.

Modulare Hüftrevisionsschäfte auf Titanbasis – Einfluß und Optimierung des Steifigkeitsverhaltens / The Modular Hip Revision Stem Made of Titanium Alloy (MRP-Titan Revision Stem) – Influence and Optimisation of Bending Stiffness

The MRP-Titan Revision stem has proved to be a highly successful implant system for revision arthroplasty of the hip. Good and excellent clinical and radiological results with spontaneous filling of bony defects have been reported, The observation of atrophy of the proximal femur associated with stem diameters > 17mm prompted us to examine the bending stiffness of stems of various diameters. To determine their static bending characteristics, the stems were tested under axial pressure loads in accordance with Euler's buckling case. Dynamic tests were performed with the mono-axial servohydraulic test equipment MTS 810. From a stem diameter of 18 mm upwards, deflection of the stem under loading decreased disproportionately, in direct correlation with the stem stiffness. By optimising the geometry and varying the alloy it is possible to obtain a constant ISD factor for the modular MRP-Titan revision stem

CONCLUSION

The MRP-Titan revision stem is a reliable implant system for revision arthroplasty of the hip. Clinical findings of atrophy of the proximal femur associated with stem diameters > 17 mm was found to be correlated with a disproportionate increase in bending stiffness. The aim of further developments will be to reduce the stiffness of larger-diameter stems by making changes to the design and/or to the alloy (Ti15Mo, Ti13Nb13Zr, Ti12Mo6Zr2Fe2).

[The LSP test for determining oscillation resistance of spinal implants]

QUESTION

New spinal implants need to be tested for primary stability in vitro under standardized laboratory conditions. To ensure the reliability of the test procedures, quality assurance standards in accordance with ISO 9000 were introduced to standardize testing including experimental set ups, loading and test frequency. These standards, however, require a relatively long time to implement.

METHOD

The LSP test was used to compare various surface treatments by different shot peening processes applied to spinal rods for dorsal spine implant systems. 6 rods made of two different cp-Titanium materials (Ti-2 and Ti-4) were tested. Dynamic tests were performed with the MTS 810 mono-axial servo-hydraulic test equipment. Beginning with a load of 200 N the rods were subjected to tensile and compressive loads, which were increased in steps of 100 N after every 50.000 cycles until rod failure.

RESULTS

Results were available after one to two weeks. The best results (LSP 167 million) were achieved with Ti-4 rods shot peened with steel balls and glass beads. In comparison, the lowest LSP value of 81 million was found with Ti-2 rods shot peened with glass beads only.

CONCLUSION

This high speed testing method has reduced the development time from two years to 6 months.

[Results of uncemented revision arthroplasty of the hip with the MRP-stem using an intrafemoral approach with vascularized distal fenestration]

AIM

THR is one of the most successful principles in orthopaedics. With the increasing number of primary THR more and more revision arthroplasties of the hip are necessary. Many factors including loss of bone stock, instability of the joint, infection, fractures, removal of the implant or cement mantles are a challenging condition for the surgeon. Many approaches and techniques for the removal of cement mantles are published. We prefer the intrafemoral approach with an distal vascularized femoral window.

METHOD

We want to describe our surgical technique and report the short term results of 45 revision arthroplasties of the hip using the uncemented modular titanium MRP stem. Mean follow-up was 2.6 years (min:1 year, max: 7 years).

RESULTS

Mean Harris hip score increased from preoperative 53,2 (16 - 89) to postoperative 90.4 (35 - 100) points. We could find remodelling of the bone and spontaneous refill of bony defects in all cases. After 14 weeks we could find bony consolidation of the femoral window. The Trendelenburg sign was positive preoperatively in 26 cases, postoperatively in 11 cases. Just one single dislocation of the revised hip occurred postoperatively.

CONCLUSION

The intrafemoral approach with distal vascularized femoral fenestration is a mild approach without further weakening of the pelvitrochanteric muscles. Removal of cement mantles is possible without any problems. Using the vascularized technique of the femoral fenestration prompt bony consolidation can be achieved.

A modular femoral implant for uncemented stem revision in THR

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.

The Morse taper junction in modular revision hip replacement--a biomechanical and retrieval analysis

All biomaterials used for total joint surgery are subjected to wear mechanisms. Morse taper junctions of modular hip revision implants are predilection sites for both fretting and crevice corrosion, dissociation and breakage of the components. The aim of this study is to quantify wear and study metallurgical changes of Morse taper junctions of in-vitro and in-vivo loaded modular revision stems. Three modular revision stems (MRP-Titan, Peter Brehm GmbH, Germany) were loaded by a servohydraulic testing machine. The loads and conditions used exceeded by far the values required by ISO-standard 7206. The tests were performed with maximum axial loads of 3,500 N to 4,000 N over 10-12 x 10(6) cycles at 2 Hz. Additionally, the female part of the taper junctions were coated with blood and bone debris. The free length of the implant was set to 200 mm. One other MRP stem was investigated after retrieval following 5.5 years of in-vivo use. All contact surfaces of the modular elements were assessed by visual inspection, optical microscopy and scanning electron microscopy (SEM). The degree of plastic deformation of the male part of the morse taper junction was determined by contouroscopy. None of the morse taper junctions broke or failed mechanically. Corrosion and wear affected all tapers, especially at the medial side. The retrieved implant showed no cracks and the amount of debris measured only one third of that for the stems tested in-vitro. The present retrieval and laboratory investigations have proven, that the morse taper junctions of the MRP-titanium stem are stable and resistant to relevant wear mechanisms. The longevity of the junctions for clinical use is given. If an optimal taper design is selected, the advantages of modular femoral components in total hip revision arthroplasty will outweigh the possible risks.