Viral RNA in Mosquitoes (Diptera: Culicidae) Collected between 2019 and 2021 in Germany.

Due to globalisation and climate change, mosquito-borne pathogens are emerging in new areas on all continents, including Europe, which has recently faced outbreaks of dengue, chikungunya and West Nile fever. The present study complements previous investigations to evaluate the circulation of mosquito-borne viruses in Germany, with the aim of identifying potential vector species and risk areas. Mosquitoes collected from 2019 to 2021 and identified to species or species group level were screened for viruses of the families Flaviviridae, Peribunyaviridae and the genus Alphavirus of the family Togaviridae. In total, 22,528 mosquitoes were examined, thus providing the most comprehensive study on West Nile virus (WNV) circulation so far in the German mosquito population. Usutu virus (USUV) RNA was detected in six samples, Sindbis virus (SINV) RNA in 21 samples and WNV RNA in 11 samples. Samples containing RNA of USUV and WNV consisted of mosquitoes collected in the East German federal states of Brandenburg, Saxony and Saxony-Anhalt, while samples with RNA of SINV originated from more widespread locations. Although minimum infection rates have remained relatively low, the intensity of virus circulation appears to be increasing compared to previous studies. Continuous mosquito screening contributes to the early detection of the introduction and spread of mosquito-borne pathogens.

Cellular co-infections of West Nile virus and Usutu virus influence virus growth kinetics.

The mosquito-borne flaviviruses West Nile virus (WNV) and Usutu virus (USUV) pose a significant threat to the health of humans and animals. Both viruses co-circulate in numerous European countries including Germany. Due to their overlapping host and vector ranges, there is a high risk of co-infections. However, it is largely unknown if WNV and USUV interact and how this might influence their epidemiology. Therefore, in-vitro infection experiments in mammalian (Vero B4), goose (GN-R) and mosquito cell lines (C6/36, CT) were performed to investigate potential effects of co-infections in vectors and vertebrate hosts. The growth kinetics of German and other European WNV and USUV strains were determined and compared. Subsequently, simultaneous co-infections were performed with selected WNV and USUV strains. The results show that the growth of USUV was suppressed by WNV in all cell lines. This effect was independent of the virus lineage but depended on the set WNV titre. The replication of WNV also decreased in co-infection scenarios on vertebrate cells. Overall, co-infections might lead to a decreased growth of USUV in mosquitoes and of both viruses in vertebrate hosts. These interactions can strongly affect the epidemiology of USUV and WNV in areas where they co-circulate.

Excretion Dynamics of Arboviruses in Mosquitoes and the Potential Use in Vector Competence Studies and Arbovirus Surveillance.

The increasing threat of arboviruses such as West Nile virus (WNV) and Usutu virus (USUV) requires the fast and efficient surveillance of these viruses. The examination of mosquitoes takes up an important part; however, these investigations are usually very time-consuming. An alternative sample type for arbovirus surveillance might be mosquito excreta. In order to determine the excretion dynamics under laboratory conditions, laboratory colonies of Aedes vexans and Culex pipiens biotype molestus were infected with WNV, USUV or tick-borne encephalitis virus (TBEV). After infection, the excreta were sampled and investigated for viral RNA. Excretion of viral RNA together with infectious blood meal could be detected up to five days after infection. Further excretion seemed to correlate with a disseminated infection in mosquitoes, at least after USUV infection. In addition, it could be determined that the amount of viral RNA in the excretions correlated positively with the viral load in the mosquito bodies. Overall, this study shows that the usage of mosquito excreta as a sample type for surveillance enables the detection of endemic viruses (WNV, USUV) as well as non-mosquito-borne viruses (TBEV). In addition, examination of viral shedding during vector competence studies can provide insights into the course of infection without sacrificing animals.

A dsRNA-binding mutant reveals only a minor role of exonuclease activity in interferon antagonism by the arenavirus nucleoprotein.

The arenavirus nucleoprotein (NP) plays an important role in the virus' ability to block interferon (IFN) production, and its exonuclease function appears to contribute to this activity. However, efforts to analyze this contribution are complicated by the functional overlap between the exonuclease active site and a neighboring region involved in IKKε-binding and subsequent inhibition of IRF3 activation, which also plays an important role in IFN production. To circumvent this issue, we mutated a residue located away from the active site that is involved in binding of the dsRNA substrate being targeted for exonuclease digestion, i.e. H426A. We found that expression of Tacaribe virus (TCRV) NP containing this RNA-binding H426A mutation was still able to efficiently block IFN-ß promoter activity in response to Sendai virus infection, despite being strongly impaired in its exonuclease activity. This was in contrast to a conventional exonuclease active site mutant (E388A), which was impaired with respect to both exonuclease activity and IFN antagonism. Importantly, growth of a recombinant virus encoding the RNA-binding mutation (rTCRV-H426A) was similar to wild-type in IFN-deficient cells, unlike the active site mutant (rTCRV-E388A), which was already markedly impaired in these cells. Further, in IFN-competent cells, the TCRV-H426A RNA-binding mutant showed more robust growth and delayed IFN-ß mRNA upregulation compared to the TCRV-E388A active site mutant. Taken together, this novel mutational approach, which allows us to now dissect the different contributions of the NP exonuclease activity and IKKε-binding/IRF3 inhibition to IFN antagonism, clearly suggests that conventional exonuclease mutants targeting the active site overestimate the contribution of the exonuclease function, and that rather other IFN antagonistic functions of NP play the dominant role in IFN-antagonism.

Vector Competence of German Aedes punctor (Kirby, 1837) for West Nile Virus Lineages 1 and 2.

West Nile virus (WNV) is a zoonotic flavivirus transmitted by mosquitoes as a biological vector. Because of its biting behavior, the widespread snow-melt mosquito Aedes punctor could be a potential bridge vector for WNV to humans and nonhuman mammals. However, little is known on its role in transmission of WNV. The aim of this study was to determine the vector competence of German Ae. punctor for WNV lineages 1 and 2. Field-collected larvae and pupae were reared to adults and offered infectious blood containing either an Italian WNV lineage 1 or a German WNV lineage 2 strain via cotton stick feeding. Engorged females were incubated for 14/15 or 21 days at 18 °C. After incubation; surviving mosquitoes were dissected and forced to salivate. Mosquito bodies with abdomens, thoraces and heads, legs plus wings and saliva samples were investigated for WNV RNA by RT-qPCR. Altogether, 2/70 (2.86%) and 5/85 (5.88%) mosquito bodies were found infected with WNV lineage 1 or 2, respectively. In two mosquitoes, viral RNA was also detected in legs and wings. No saliva sample contained viral RNA. Based on these results, we conclude that Ae. punctor does not play an important role in WNV transmission in Germany.

Phenotypic plasticity in clutch size regulation among populations of a potential invasive fruit fly from environments that vary in host heterogeneity and isolation.

Phenotypic plasticity is thought to evolve in response to environmental unpredictability and can shield genotypes from selection. However, selection can also act on plastic traits. Egg-laying behaviour, including clutch size regulation, is a plastic behavioural trait among tephritid fruit flies. We compared plasticity in clutch size regulation among females of Anastrepha ludens populations stemming from environments that differed in the degree of predictability in egg-laying opportunities. Clutch size regulation in response to hosts of different sizes was compared among flies from (a) a wild, highly isolated population, (b) a wild population that switches seasonally from a small wild host fruit that varies greatly in abundance to an abundant large-sized commercial host, and (c) a laboratory population. Flies from all three populations adjusted clutch number and size according to host size. However, flies from the heterogeneous wild environment were more plastic in adjusting clutch size than flies from agricultural settings that also laid fewer eggs; yet both populations were more plastic in adjusting clutch size in line with host size when compared with laboratory females. When wild and orchard females encountered the largest host, clutch size was extremely variable and egg regulation did not follow the same trend. Heterogeneity in host availability in space and time appears to be as important as seasonal variation in host size in maintaining plastic clutch size regulation behaviour. In stable environments, there was a clear reduction in the plasticity of these traits.

Microbial composition affects the performance of an artificial Tephritid larval diet.

The present study investigated the patterns of microorganisms in an artificial larval diet during Dacus ciliatus (Diptera; Tephritidae) larval development. Microbial population contents in the diet of total heterotrophic bacteria, yeast and molds, coliform and lactobacilli, and their dynamics during development, were monitored. Initially, the microbial composition in diet trays failing to produce viable pupae and in trays successfully producing pupae and adult flies was characterized. The failing diet trays contained large populations of lactobacilli that increased during larval development, and low populations of coliforms. In contrast, the successful diet showed an increasing population of coliforms and a low, or undetected, population of lactobacilli. To study the hypothesis that lactobacilli affect D. ciliatus larval development, we conducted controlled inoculation experiments in which Lactobacillus plantarum was added into fresh diet at the time of egg seeding. L. plantarum inoculated trays showed no production of D. ciliatus. Control trays without lactobacilli inoculation showed variable results. One tray successfully produced viable pupae and adults, and showed a slight and slow increase in the indigenous populations of lactobacilli. The second tray, however, failed to produce pupae and showed a fast increase of the indigenous lactobacilli to very high levels. Monitored pH trends in L. plantarum-inoculated diet showed a sharp pH decrease during the first 4 days of larval development from 5 to less than 4 units, while successful diet, producing viable D. ciliatus pupae and adults, showed a moderate pH drop during most of the larval development period. The paper discusses the possible ecological interactions between D. ciliatus larvae, the microbial content of the diet and the physical properties of the diet. The discussion also points out at the usefulness of this approach in understanding and managing mass production parameters of tephritid fruit flies industrial diets used for Sterile Insect Technique.

Do mothers really know best? Complexities in testing the preference-performance hypothesis in polyphagous frugivorous fruit flies.

The preference-performance hypothesis (PPH) has widely been used to explain host exploitation patterns by phytophagous insects. However, this hypothesis often fails in the case of polyphagous species when compared with specialists. One explanation, validated by the information-processing hypothesis (IPH), considers that polyphagous insects are unable to process a large array of cues, which hinders females from distinguishing between high- and low- quality hosts. Here we analyzed Anastrepha ludens female host preference and offspring performance, and tested if neuronal limitations could possibly play a role in the incapacity of the polyphagous A. ludens to make 'accurate decisions' and therefore partially explain mismatches related to PPH. Results testing the PPH by correlating female preference to six naturally occurring hosts and its offspring outcomes show that A. ludens females oviposited greater proportions of eggs on fruit according to hierarchical preferences. Infestation level was low in white sapote, the preferential and seemingly putative ancestral host, likely due to sapote defence mechanisms. Pupal weight and adult size were lower when A. ludens larvae developed in guava (conditional host that was artificially infested) and peach, a lower ranked host compared with 'Marsh' grapefruit, white sapote, and 'Manila' mango (three preferred hosts). Larvae reared in 'Manzano' pepper, a low-ranked host, performed better than in peach and guava. Results testing the IPH, show that polyphagous A. ludens females were less accurate when discerning between a non natural host (guava) when compared with a preferred, natural host (grapefruit): error rate was significantly higher, number of oviposited fruit in a 6-h period was extremely low, time searching and ovipositing took longer, and pupae recovery was extremely low. Our findings indicate that both hypotheses tested are complementary and help better understand host use by A. ludens. However, we also discuss the complexity of polyphagy considering other factors such as plant resistance/defence mechanisms which are not fully addressed in both theories tested.

Costly Nutritious Diets do not Necessarily Translate into Better Performance of Artificially Reared Fruit Flies (Diptera: Tephritidae).

Protein, lipid, carbohydrate, and energy contents of three artificial diets (Xal2, Met1, and Met2) used for laboratory-rearing and mass-rearing the Mexican fruit fly, Anastrepha ludens (Loew), for a sterile insect technique program were measured. The larval survival, pupation, pupal weight, adult emergence, sex ratio, and flight capacity of the flies reared on each of these diets were also quantified. The diet with the highest nutrient and energy content was Xal2 followed by Met2 and Met1, but larval recovery and percent pupation was significantly higher in flies reared on either the Met1 or Met2 diets. A. ludens reared on Xal2 exhibited the highest proportion of adults capable of flight. No other response variable differed significantly among the three diets tested. This suggests that a high content of nutrients and multiple sources of protein (dried yeast and wheat germ in the case of the Xal2 diet) do not necessarily improve overall performance or fly quality. We conclude that nutritious diets for A. ludens can be modified to reduce their cost without compromising the performance of artificially reared flies.

Limits to the host range of the highly polyphagous tephritid fruit fly Anastrepha ludens in its natural habitat.

Anastepha ludens (Diptera: Tephritidae) is a highly polyphagous fruit fly that is able to develop in a wide range of hosts. Understanding the limits of this pest's host range could provide valuable information for pest management and plant breeding for pest resistance. Previous studies have shown that guavas (Psidium guajava (Myrtaceae) L.), are not attacked under natural conditions by A. ludens. To understand this phenomenon, guavas were exposed to natural infestation by A. ludens and to other fruit fly species that infest guavas in nature (Anastrepha striata Schiner, Anastepha fraterculus (Wiedemann), Anastepha obliqua (Macquart)). Once the susceptible phenological stage of guavas was determined, fruit infestation levels were compared between A. ludens and A. striata. Choice and non-choice tests were performed under field-cage conditions. Under field conditions, guavas were susceptible to A. striata and A. fraterculus attack all the way from when fruit was undeveloped to when fruit began to ripen. No infestation by A. ludens was recorded under natural conditions. Similar results were obtained when forced exposures were performed, indicating that unripe guavas were preferred by A. striata over ripe fruit, and that infestation rates were higher at early fruit maturity stages. Under forced oviposition conditions, A. ludens larvae were unable to develop in unripe guavas but did so in fully ripe fruit. However, A. ludens fitness parameters were dramatically affected, exhibiting reduced survival and reduced pupal weight compared to conspecifics that developed in a natural host, grapefruit. We confirm that P. guajava should not be treated as a natural host of this pestiferous species, and suggest that both behavioral aspects and the fact that larvae are unable to adequately develop in this fruit, indeed represent clear limits to A. ludens's broad host range.

Susceptibility of 15 mango (Sapindales: Anacardiaceae) cultivars to the attack by Anastrepha ludens and Anastrepha obliqua (Diptera: Tephritidae) and the role of underdeveloped fruit as pest reservoirs: management implications.

We evaluated the susceptibility of 15 mango cultivars to the attack of Anastrepha ludens (Loew) and Anastrepha obliqua (Macquart) (Diptera: Tephritidae), the main tephritid pests of this crop in Mexico. In a field experiment, bagged fruit-bearing branches were exposed to gravid females of both fly species. Infestation rates, developmental time, adult eclosion, and F1 adult longevity, fecundity, and fertility were recorded, ranking cultivars in terms of susceptibility to fly attack and development. We also compared the volatile profile in selected resistant and susceptible cultivars in search of possible correlations. In a second experiment, clutch size for A. ludens was determined in each cultivar. Infestation rates, developmental time, and F1 demographic parameters varied sharply among cultivars and between fly species for bagged fruit. Cultivars 'Vishi,' '74-82,' and 'Brooks' were most susceptible to A. ludens infestation while "Tommy,' 'Sensation,' and 'Ataulfo "niño"' (parthenocarpic fruit) were most susceptible to A. obliqua infestation. 'Edward,' 'Kent,' 'Brooks late,' 'Palmer, and 'Ataulfo' exhibited tolerance to attack of both fly species. Fruit of susceptible and resistant cultivars exhibited unique volatile profiles. Fly development and F1 adult demographic parameters varied significantly among cultivars. A. ludens females laid larger clutches in larger and harder fruit. We highlight the important role of Ataulfo "niño" as pest reservoir if fruit is left unharvested on trees. We discuss the possible use of highly resistant cultivars as trap crops or egg sinks.

EWI-2wint promotes CD81 clustering that abrogates Hepatitis C Virus entry.

CD81 is a major receptor for Hepatitis C Virus (HCV). It belongs to the tetraspanin family whose members form dynamic clusters with numerous partner proteins and with one another, forming tetraspanin-enriched areas in the plasma membrane. In our study, we combined single-molecule microscopy and biochemistry experiments to investigate the clustering and membrane behaviour of CD81 in the context of cells expressing EWI-2wint, a natural inhibitor of HCV entry. Interestingly, we found that EWI-2wint reduces the global diffusion of CD81 molecules due to a decrease of the diffusion rate of mobile CD81 molecules and an increase in the proportion of confined molecules. Indeed, we demonstrated that EWI-2wint promotes CD81 clustering and confinement in CD81-enriched areas. In addition, we showed that EWI-2wint influences the colocalization of CD81 with Claudin-1 - a co-receptor required for HCV entry. Together, our results indicate that a change in membrane partitioning of CD81 occurs in the presence of EWI-2wint. This study gives new insights on the mechanism by which HCV enters into its target cells, namely by exploiting the dynamic properties of CD81.

X-ray structure of the Yersinia pestis heme transporter HmuUV.

HmuUV is a bacterial ATP-binding cassette (ABC) transporter that catalyzes heme uptake into the cytoplasm of the gram-negative pathogen Yersinia pestis. We report the crystal structure of HmuUV at 3.0 Å resolution in a nucleotide-free state, which features a heme translocation pathway in an outward-facing conformation, poised to accept a heme from the cognate periplasmic binding protein HmuT. A new assay allowed us to determine in vitro rates of HmuUV-catalyzed heme transport into proteoliposomes and to establish the role of conserved residues in the translocation pathway of HmuUV and at the interface with HmuT. Differences in architecture relative to the related vitamin B(12) transporter BtuCD suggest an adaptation of HmuUV for its smaller substrate. Our study also suggests that type II ABC importers, which include bacterial iron-siderophore, heme and cobalamin transporters, have a coupling mechanism distinct from that of other ABC transporters.

Transmembrane gate movements in the type II ATP-binding cassette (ABC) importer BtuCD-F during nucleotide cycle.

ATP-binding cassette (ABC) transporters are ubiquitous integral membrane proteins that translocate substrates across cell membranes. The alternating access of their transmembrane domains to opposite sides of the membrane powered by the closure and reopening of the nucleotide binding domains is proposed to drive the translocation events. Despite clear structural similarities, evidence for considerable mechanistic diversity starts to accumulate within the importers subfamily. We present here a detailed study of the gating mechanism of a type II ABC importer, the BtuCD-F vitamin B(12) importer from Escherichia coli, elucidated by EPR spectroscopy. Distance changes at key positions in the translocation gates in the nucleotide-free, ATP- and ADP-bound conformations of the transporter were measured in detergent micelles and liposomes. The translocation gates of the BtuCD-F complex undergo conformational changes in line with a "two-state" alternating access model. We provide the first direct evidence that binding of ATP drives the gates to an inward-facing conformation, in contrast to type I importers specific for maltose, molybdate, or methionine. Following ATP hydrolysis, the translocation gates restore to an apo-like conformation. In the presence of ATP, an excess of vitamin B(12) promotes the reopening of the gates toward the periplasm and the dislodgment of BtuF from the transporter. The EPR data allow a productive translocation cycle of the vitamin B(12) transporter to be modeled.

Reduced uptake of [¹8F]FDOPA PET in asymptomatic welders with occupational manganese exposure.

BACKGROUND: Welding exposes workers to manganese (Mn) fumes, but it is unclear if this exposure damages dopaminergic neurons in the basal ganglia and predisposes individuals to develop parkinsonism. PET imaging with 6-[(18)F]fluoro-l-dopa (FDOPA) is a noninvasive measure of nigrostriatal dopaminergic neuron integrity. The purpose of this study is to determine whether welding exposure is associated with damage to nigrostriatal neurons in asymptomatic workers. METHODS: We imaged 20 asymptomatic welders exposed to Mn fumes, 20 subjects with idiopathic Parkinson disease (IPD), and 20 normal controls using FDOPA PET. All subjects were examined by a movement disorders specialist. Basal ganglia volumes of interest were identified for each subject. The specific uptake of FDOPA, K(i), was generated for each region using graphical analysis method. RESULTS: Repeated measures general linear model (GLM) analysis demonstrated a strong interaction between diagnostic group and region (F(4,112) = 15.36, p < 0.001). Caudate K(i)s were lower in asymptomatic welders (0.0098 + 0.0013 minutes(-1)) compared to control subjects (0.0111 + 0.0012 minutes(-1), p = 0.002). The regional pattern of uptake in welders was most affected in the caudate > anterior putamen > posterior putamen. This uptake pattern was anatomically reversed from the pattern found in subjects with IPD. CONCLUSIONS: Active, asymptomatic welders with Mn exposure demonstrate reduced FDOPA PET uptake indicating dysfunction in the nigrostriatal dopamine system. The caudate K(i) reduction in welders may represent an early (asymptomatic) marker of Mn neurotoxicity and appears to be distinct from the pattern of dysfunction found in symptomatic IPD.

Two stacked heme molecules in the binding pocket of the periplasmic heme-binding protein HmuT from Yersinia pestis.

The periplasmic binding protein HmuT from Yersinia pestis (YpHmuT) is a component of the heme uptake locus hmu and delivers bound hemin to the inner-membrane-localized, ATP-binding cassette (ABC) transporter HmuUV for translocation into the cytoplasm. The mechanism of this process, heme transport across the inner membrane of pathogenic bacteria, is currently insufficiently understood at the molecular level. Here we describe the crystal structures of the substrate-free and heme-bound states of YpHmuT, revealing two lobes with a central binding cleft. Superposition of the apo and holo states reveals a minor tilting motion of the lobes surrounding concomitant with heme binding. Unexpectedly, YpHmuT binds two stacked hemes in a central binding cleft that is larger than those of the homologous periplasmic heme-binding proteins ShuT and PhuT, both of which bind only one heme. The hemes bound to YpHmuT are coordinated via a tyrosine side chain that contacts the Fe atom of one heme and a histidine that contacts the Fe atom of the other heme. The coordinating histidine is only conserved in a subset of periplasmic heme binding proteins suggesting that its presence predicts the ability to bind two heme molecules simultaneously. The structural data are supported by spectroscopic binding studies performed in solution, where up to two hemes can bind to YpHmuT. Isothermal titration calorimetry suggests that the two hemes are bound in discrete, sequential steps and with dissociation constants (K(D)) of ∼0.29  and ∼29 nM, which is similar to the affinities observed in other bacterial substrate binding proteins. Our findings suggest that the cognate ABC transporter HmuUV may simultaneously translocate two hemes per reaction cycle.

Distinct gate conformations of the ABC transporter BtuCD revealed by electron spin resonance spectroscopy and chemical cross-linking.

BtuCD is a type II ABC importer that catalyzes the translocation of vitamin B12 from the periplasm into the cytoplasm of Escherichia coli. Crystal structures of BtuCD and the related HiF (or Hi1470/71) protein from Haemophilus influenzae have revealed distinct conformations of the transmembrane domains that form inner and outer gates. We used electron spin resonance spectroscopy to study the reaction cycle of BtuCD after labeling the protein at residues located at these gates. The results suggest that BtuCD as a prototype type II ABC importer may have a mechanism that is distinct from that of ABC exporters such as Sav1866 or type I ABC importers such as those specific for molybdate (ModBC) or maltose (MalFGK).

Structural basis of trans-inhibition in a molybdate/tungstate ABC transporter.

Transport across cellular membranes is an essential process that is catalyzed by diverse membrane transport proteins. The turnover rates of certain transporters are inhibited by their substrates in a process termed trans-inhibition, whose structural basis is poorly understood. We present the crystal structure of a molybdate/tungstate ABC transporter (ModBC) from Methanosarcina acetivorans in a trans-inhibited state. The regulatory domains of the nucleotide-binding subunits are in close contact and provide two oxyanion binding pockets at the shared interface. By specifically binding to these pockets, molybdate or tungstate prevent adenosine triphosphatase activity and lock the transporter in an inward-facing conformation, with the catalytic motifs of the nucleotide-binding domains separated. This allosteric effect prevents the transporter from switching between the inward-facing and the outward-facing states, thus interfering with the alternating access and release mechanism.

Asymmetry in the structure of the ABC transporter-binding protein complex BtuCD-BtuF.

BtuCD is an adenosine triphosphate-binding cassette (ABC) transporter that translocates vitamin B12 from the periplasmic binding protein BtuF into the cytoplasm of Escherichia coli. The 2.6 angstrom crystal structure of a complex BtuCD-F reveals substantial conformational changes as compared with the previously reported structures of BtuCD and BtuF. The lobes of BtuF are spread apart, and B12 is displaced from the binding pocket. The transmembrane BtuC subunits reveal two distinct conformations, and the translocation pathway is closed to both sides of the membrane. Electron paramagnetic resonance spectra of spin-labeled cysteine mutants reconstituted in proteoliposomes are consistent with the conformation of BtuCD-F that was observed in the crystal structure. A comparison with BtuCD and the homologous HI1470/71 protein suggests that the structure of BtuCD-F may reflect a posttranslocation intermediate.

[Bone defects in revision total knee arthroplasty: classification and management]. / Knochendefekte beim Knieendoprothesenwechsel: Klassifikation und Management.

The goal of bone reconstruction in revision total knee arthroplasty is to provide a stable support for the implant and to re-establish the correct joint line. Therefore, a useful, therapy-based classification of the defects is necessary. According to Stockley et al. (1992), the defects are classified into contained and uncontained defects. Uncontained defects can be reconstructed using structural allografts or metal wedges. In contained defects, cancellous allograft can be used. For aseptic loosening of total knee arthroplasty, the defect classification according to Engh and Parks (1994) can be helpful because of its recommendations for reconstruction. In case of the more common first or second graded defects, reconstruction is performed using modular revision components or allografts. For the rare third graded defects, bulk allografts or modular tumour endoprostheses are recommended. On the basis of more than 150 revision total knee arthroplasties performed in our hospital the classification of bone defects and their clinical consequences are presented in this review.