[Partial exchange in total hip arthroplasty : What can we combine?] / Gelenkteilwechsel in der Hüftarthroplastik : Was dürfen wir kombinieren?

BACKGROUND: In case of hip revision arthroplasty, one component (cup/stem) is often well fixed and does not need to be exchanged. The newly implanted component needs to be compatible with the well-fixed implant. The combination of implants from different companies leads to "mix and match" or even mismatch between the implants. OBJECTIVES AND METHODS: The objective of this work was to describe possible combinations including their specifications that need to be considered in partial exchange of hip prostheses. For this purpose the literature, surgical techniques of companies and judgements concerning this topic were analysed and our own results and experiences were included. RESULTS AND CONCLUSIONS: Partial revision arthroplasty can be challenging and needs to be planned in detail. In case of isolated cup or inlay revision with exchange of a modular head the cone of the stem needs to be identified. A ceramic head may be used in revision with a titanium sleeve even from a different company as long as they are compatible. Patients however need to give their informed consent for this mix and match procedure. This procedure is done frequently and good study results support this, however from a juristic point of view a definite recommendation cannot be given. If the inlay of a cup is replaced, the original inlay should be used. If this is not available anymore, it can be manufactured as a special product in many cases. If this is also not possible, an inlay can also be cemented into a well-fixed cup. Biomechanical and clinical studies support this off-label technique. In case of an isolated exchange of the stem with a ceramic inlay that is retained in a well-fixed cup, the revision stem and ceramic head need to be from the same company as the cup. In case of ceramic fracture, a ceramic head with a titanium sleeve should be combined with a PE or ceramic inlay, a metal head or inlay should never be used.

[Does the certification according to EndoCert lead to a better quality of treatment?] / Bringt die Zertifizierung nach EndoCert eine messbare Verbesserung der Versorgungsqualität?

BACKGROUND: Certification according to EndoCert in the field of arthroplasty in Germany aims at standardization of treatment and with this optimization of its quality. However, huge capital investment and efforts are necessary. There are currently more than 400 certified centres in Germany. Our Department of Orthopaedics at a German medical school was certified in the pilot phase. The aim of this study was to analyse whether there was a difference in the quality in the year after the certification. A second aim was to analyse whether the defined quality criteria are adequate for a university hospital. MATERIALS AND METHODS: The quality criteria as defined by EndoCert were analysed in the year before (2011) and after certification (2012). The observed complications were noted for 1 year postoperatively. The clinical outcome was analysed with Western Ontario and McMaster University Osteoarthritis Index Score (WOMAC) 1 year postoperatively. RESULTS: There was no difference concerning the criteria analysed, including the clinical outcome in the year before and that after certification. In both years, nearly all criteria could be reached except the operation time and the infection rate in hip and knee revision surgery. CONCLUSION: Certification did not lead to a measurable change of the quality of care. Nearly all criteria, except the infection rate in revision arthroplasty (required: less than 3% at 1 year postop.) and the operation duration could be fulfilled. This rate as well as the operation duration should be revised. Certification according to EndoCert is an important tool to prove quality care, however big efforts and capital are needed. The criteria should be constantly revised and reduced, as these resources should not be missed in patient care.

[What can we learn in future from the data of the German Arthroplasty Registry (EPRD) in comparison to other registries?]. / Welcher Zusatznutzen ergibt sich in Zukunft aus den Daten des EPRD im Vergleich zu anderen Registern?

The German Arthroplasty Registry (EPRD) was founded in 2010 and has been in full operation since 2014. Previous attempts at a systematic data collection of elective and non-elective knee and hip replacement in Germany failed mainly because of the long-term lack of funding. The EPRD is an interdisciplinary collaborative partnership between the German Association of Orthopedics and Orthopedic Surgery (DGOOC), all implant manufacturers of the German Medical Technology Association (BVMed), health insurers (AOK and the Association of Additional Healthcare Insurance) and hospitals (German Hospital Federation). As part of this cooperation a worldwide unique implant database has been set up, which includes all relevant components and a detailed description of implant specifications. This implant library enables a detailed evaluation of implant survival, revision rates and possible inferior implant performance of knee and hip replacements in Germany. At the end of 2015 the EPRD encompassed over 200,000 registered operations. Due to the high number of hip and knee arthroplasties in Germany with many different implants from different manufacturers there will be a rapid growth of data that are available for a national and also international comparison of the results.

Development and validation of a weight-bearing finite element model for total knee replacement.

Total knee arthroplasty (TKA) is a successful procedure for osteoarthritis. However, some patients (19%) do have pain after surgery. A finite element model was developed based on boundary conditions of a knee rig. A 3D-model of an anatomical full leg was generated from magnetic resonance image data and a total knee prosthesis was implanted without patella resurfacing. In the finite element model, a restarting procedure was programmed in order to hold the ground reaction force constant with an adapted quadriceps muscle force during a squat from 20° to 105° of flexion. Knee rig experimental data were used to validate the numerical model in the patellofemoral and femorotibial joint. Furthermore, sensitivity analyses of Young's modulus of the patella cartilage, posterior cruciate ligament (PCL) stiffness, and patella tendon origin were performed. Pearson's correlations for retropatellar contact area, pressure, patella flexion, and femorotibial ap-movement were near to 1. Lowest root mean square error for retropatellar pressure, patella flexion, and femorotibial ap-movement were found for the baseline model setup with Young's modulus of 5 MPa for patella cartilage, a downscaled PCL stiffness of 25% compared to the literature given value and an anatomical origin of the patella tendon. The results of the conducted finite element model are comparable with the experimental results. Therefore, the finite element model developed in this study can be used for further clinical investigations and will help to better understand the clinical aspects after TKA with an unresurfaced patella.

[Experience with medial unicompartmental prostheses with a mobile plateau]. / Erfahrungen mit medialen monokondylären Prothesen mit mobilem Plateau.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) has become an accepted therapy for medial osteoarthritis. The main reasons for its popularity are the minimally invasive surgical technique and the reports of excellent long-term results including high patient satisfaction and good knee joint function especially in younger patients. OBJECTIVES: The purpose of our retrospective study was to evaluate the physical activities of patients who had undergone an Oxford III medial UKA. Special attention was paid to implant positioning and osteoarthritis of the patellofemoral joint. MATERIALS AND METHODS: Of 181 implanted Oxford III prosthesis, 136 (75.1%) could be followed up. The mean age at time of surgery was 65.2 years; the average time of follow-up was 4.2 years. In addition to a physical examination and x-ray, the following scores were obtained: WOMAC (Western Ontario and McMaster Osteoarthritis Index), OKS (Oxford Knee Score), KSS (Knee Society Score), UCLA activity and the Turba score. RESULTS: The majority of the patients (81%) returned to their sporting activity following knee surgery. Higher complication rates or progression of osteoarthritis associated with sporting activities were not observed. The active patients had significantly higher scores for the OKS, KSS, WOMAC, and UCLA scores. The correct implant position, especially avoiding overcorrection to valgus malalignment, is important for good clinical outcome. CONCLUSION: Our results demonstrate that a high degree of patient satisfaction in terms of physical and sporting activity can be achieved using the Oxford III UKA for medial osteoarthritis without an increased risk for complications.

Core-shell potassium niobate nanowires for enhanced nonlinear optical effects.

We demonstrate the synthesis as well as the optical characterization of core-shell nanowires. The wires consist of a potassium niobate (KNbO3) core and a gold shell. The nonlinear optical properties of the core are combined with the plasmonic resonance of the shell and offer an enhanced optical signal in the near infrared spectral range. We compare two different functionalization schemes of the core material prior to the shell growth process: silanization and polyelectrolyte. We show that the latter leads to a smoother and complete core-shell nanostructure and an easier-to-use synthesis process. A Mie-theory based theoretical approach is presented to model the enhanced second-harmonic generated (SHG) signal of the core-shell wires, illustrating the influence of the fabrication-induced varying geometrical factors of wire radius and shell thickness. A spectroscopic measurement on a core-shell nanowire shows a strong localized surface plasmon resonance close to 900 nm, which matches with the SHG resonance obtained from nonlinear optical experiments with the same nanowire. According to the simulation, this corresponds to a wire radius of 35 nm and a shell thickness of 7.5 nm. By comparing SHG signals measured from an uncoated nanowire and the coated one, we obtain a 250 times enhancement factor. This is less than the calculated enhancement, which considers a cylindrical nanowire with a perfectly smooth shell. Thus, we explain this discrepancy mainly with the roughness of the synthesized gold shell.

[Implant position of total hip arthroplasty shafts. Establishment of a new method for comparison between planned and achieved shaft positions]. / Implantatposition von Hüftendoprothesenschäften. Etablierung einer neuen Methode zum Vergleich zwischen geplanter und erreichter Schaftposition.

BACKGROUND: One of the main goals of the preoperative planning of hip prostheses is adequate shaft positioning with reconstruction of leg length and offset. The purpose of this study was to compare the planned and achieved shaft positions using a modified program for migration measurement. METHODS: In 60 cases of total hip replacement the preoperative planning was compared with the postoperative radiograph using a modified version of the well-established EBRA-FCA program. The results of this new measurement were compared to conventional measurements. In 25 cases the intraobserver and interobserver reliability was determined. RESULTS: The novel measurements correlated best with the measured distance between the greater trochanter and the center of rotation and yielded the best intraobserver and interobserver reliability. In general, cementless stems had a slightly more proximal position (0.65 mm) compared to cemented stems. CONCLUSIONS: The modified program for migration measurement facilitates a reproducible and fast comparison of the planned and achieved shaft positions thus implementing an early and objective control of postoperative shaft position.

[Anatomy and biomechanics of the patellofemoral joint: physiological conditions and changes after total knee arthroplasty]. / Anatomie und Biomechanik des Patellofemoralgelenks : Physiologische Gegebenheiten und Veränderungen nach Implantation einer Knietotalendoprothese.

The patellofemoral joint constitutes a complex anatomical and functional entity. The tensile force of the quadriceps femoris muscle is transmitted through the patella and patellar ligament onto the tibial tuberosity. This particular three-dimensional arrangement increases the torsional moment acting on the knee joint. Dynamic alignment of the patella is determined by trochlear geometry and is supported by active muscular and passive connective tissue stabilizers. In addition to the retinaculum of the patella, the medial patellofemoral ligament is attracting increasing clinical attention. Multidirectional motion of the patella is closely connected to retropatellar pressure distribution which can be modulated by moving the patellar ligament insertion. Implantation of a knee endoprosthesis changes the joint surface geometry and consequently patella kinematics and retropatellar pressure distribution. Finite element analysis provides the possibility to assess retropatellar pressure distribution before and after implantation of prostheses.

Selectively deposited silver coatings on gold-capped silicon nanowires for surface-enhanced Raman spectroscopy.

Gold caps on silicon nanowires are selectively coated with silver by autometallography (electroless deposition). Changing the conditions of silver deposition, a variety of different coating morphologies can be produced [figure: see text]. The different silver coating morphologies are investigated in terms of their capabilities for surface enhanced Raman scattering (SERS) experiments.Gold caps on silicon nanowires are hemispherical and only a few tens of nanometers in diameter when grown from metal catalysts by the vapor-liquid-solid growth mechanism using chemical vapor deposition. These gold caps are capable of enhancing Raman signals based on the surface-enhanced Raman scattering effect. The Raman signal can be enhanced even further (by at least one order of magnitude) when silver is selectively deposited onto these gold caps by autometallography (electroless deposition). By changing the silver deposition conditions, different coating morphologies can be realized on the gold caps that range from very thin, smooth layers to uneven and extremely rough coatings. The SERS signal enhancement and the spatial homogeneity of the achievable enhancement are compared for the different silver coatings using a model dye molecule.

Gold-silver and silver-silver nanoparticle constructs based on DNA hybridization of thiol- and amino-functionalized oligonucleotides.

Metal nanoparticle constructs of particles of different sizes and materials were prepared, using DNA as connecting element. Therefore, gold and silver nanoparticles were functionalized with complementary DNA sequences that enabled a controlled coupling. The well-established system based on thiolated DNA was thereby complemented with amino-functionalized DNA. The realization of specific DNA-DNA bonds due to hybridization was controlled by the ionic strength. The results demonstrate the potential of the combination of different particle sizes, composition as well as coupling chemistry in order to realize controlled conjugates of nanoparticles.

Optically controlled thermal management on the nanometer length scale.

The manipulation of polymers and biological molecules or the control of chemical reactions on a nanometer scale by means of laser pulses shows great promise for applications in modern nanotechnology, biotechnology, molecular medicine or chemistry. A controllable, parallel, highly efficient and very local heat conversion of the incident laser light into metal nanoparticles without ablation or fragmentation provides the means for a tool like a 'nanoreactor', a 'nanowelder', a 'nanocrystallizer' or a 'nanodesorber'. In this paper we explain theoretically and show experimentally the interaction of laser radiation with gold nanoparticles on a polymethylmethacrylate (PMMA) layer (one-photon excitation) by means of different laser pulse lengths, wavelengths and pulse repetition rates. To the best of our knowledge this is the first report showing the possibility of highly local (in a 40 nm range) regulated heat insertion into the nanoparticle and its surroundings without ablation of the gold nanoparticles. In an earlier paper we showed that near-infrared femtosecond irradiation can cut labeled DNA sequences in metaphase chromosomes below the diffraction-limited spot size. Now, we use gold as well as silver-enhanced gold nanoparticles on DNA (also within chromosomes) as energy coupling objects for femtosecond laser irradiation with single-and two-photon excitation. We show the results of highly localized destruction effects on DNA that occur only nearby the nanoparticles.