A literature review and expert consensus statement on diagnostics in suspected metal implant allergy

BACKGROUND

Although rare, allergic reactions to metal implants represent a diagnostic challenge in view of missing guidelines.

OBJECTIVES

To develop an European expert consensus on characteristics of metal allergy reactions and the utility of various diagnostic tools in suspected metal implant allergy.

METHODS

A nominal group technique (NGT) was applied to develop consensus statements. Initially an online literature database was created on a secure server to enable a comprehensive information. Twenty-three statements were formulated on potential aspects of metal implant allergy with a focus on diagnostics and grouped into five domains. For the consensus development, the panel of 12 experts initially did refine and reformulate those statements that were ambiguous or had unclear wording. By face-to-face (9/12) or virtual participation (3/12), an anonymous online voting was performed.

RESULTS

Consensus (≥80% of agreement) was reached in 20/23 statements. The panel agreed that implant allergy despite being rare should be considered in case of persistent unexplained symptoms. It was, however, recommended to allow adequate time for resolution of symptoms associated with healing and integration of an implant. Obtaining questionnaire-aided standardized medical history and standardized scoring of patient outcomes was also considered an important step by all experts There was broad consensus regarding the utility/performance of patch testing with additional late reading. It was recognized that the lymphocyte transformation test (LTT) has to many limitations to be generally recommended. Prior to orthopaedic implant, allergy screening of patients without a history of potential allergy to implant components was not recommended.

CONCLUSIONS

Using an expert consensus process, statements concerning allergy diagnostics in suspected metal implant allergy were created. Areas of nonconsensus were identified, stressing uncertainty among the experts around topics such as preoperative testing in assumed allergy, histological correlate of periimplant allergy and in vitro testing, which underscores the need for further research.

Invasive electrical stimulation in the treatment of avascular osteonecrosis of the femoral head - mid-term results

The study aimed to evaluate the outcomes of osteonecrosis of the femoral head (ONFH) in adults after surgical treatment including invasive electromagnetic osteostimulation (E-Stim). Further, the influence of disease stage and several comorbidities on the joint preservation rate should be examined. Sixty patients (66 hip joints) with ONFH were included in this retrospective cross-sectional analysis (mean follow-up: 58 months, 19-110 months). Potential ONFH risk factors and comorbidities (ONFH stage, age, sex, alcohol, smoking, cortisone medication, chemotherapy) were recorded. The influence of specific parameters on the joint preservation rates was evaluated by a multivariate logistic regression analysis. Finally, patients with preserved hip joints underwent an assessment of their last available X-rays. The joint preservation rate depended on the initial ONFH Steinberg stage (I+II: 82.8%, III: 70.8%, ≥ IVa: 38.5%). Initially collapsed ONFH (p ≤ 0.001) and cortisone therapy (p = 0.004) significantly decreased the joint preservation rates. In case of progressed ONFH, the presence of ≥ 2 risk factors resulted in higher THA conversion rates (stage III: OR 18.8; stage ≥IVa: OR 12). In 94% of the available X-rays, the ONFH stage improved or did not progress. No complications could be attributed to the E-Stim device or procedure. The present surgical protocol including minimally invasive E-Stim revealed high joint preservation rates for non-collapsed ONFH after mid-term postoperative follow-up. Especially in progressed ONFH, the-risk profile seems to be crucial and hence, for joint preserving surgery, careful patient selection is recommended.

Novel approach to estimate distraction forces in distraction osteogenesis and application in the human lower leg

PURPOSE

In distraction osteogenesis (DO) of long bones, new bone tissue is distracted to lengthen limbs or reconstruct bone defects. However, mechanical boundary conditions in human application such as arising forces are mainly based on limited empirical data. Our aim was the numerical determination of the callus distraction force (CDF) and the total distraction force (TDF) during DO in the tibia of adults to advance the understanding of callus tissue behavior and optimize DO procedures.

METHOD

We implemented a mathematical model based on an animal experiment to enable the calculation of forces arising while distracting callus tissue, excluding the influence of surrounding soft tissue (muscles, skin etc.). The CDF progression for the distraction period was calculated using the implemented model and varying distraction parameters (initial gap, area, step size, time interval, length). Further, we estimated the CDF based on reported forces in humans and compared the results to our model predictions. In addition, we calculated the TDF based on our CDF predictions in combination with reported resisting forces due to soft tissue presence in human cadavers. Finally, we compared the progressions to in vivo TDF measurements for validation.

RESULTS

Due to relaxation, a peak and resting CDF is observable for each distraction step. Our biomechanical results show a non-linear degressive increase of the resting and peak CDF at the beginning and a steady non-linear increase thereafter. The calculated resting and peak CDF in the tibial metaphysis ranged from 0.00075 to 0.0089 N and 0.22-2.6 N at the beginning as well as 20-25 N and 70-75 N at the end of distraction. The comparison to in vivo data showed the plausibility of our predictions and resulted in a 10-33% and 10-23% share of resting CDF in the total resting force for bone transport and elongation, respectively. Further, the percentage of peak CDF in total peak force was found to be 29-58% and 27-55% for bone transport and elongation, respectively. Moreover, our TDF predictions were valid based on the comparison to in vivo forces and resulted in a degressive increase from 6 to 125 N for the peak TDF and from 5 to 76 N for the resting TDF.

CONCLUSION

Our approach enables the estimation of forces arising due to the distraction of callus tissue in humans and results in plausible force progressions as well as absolute force values for the callus distraction force during DO. In combination with measurements of resisting forces due to the presence of soft tissue, the total distraction force in DO may also be evaluated. We thus propose the application of this method to approximate the behavior of mechanical callus properties during DO in humans as an alternative to in vivo measurements.

Subject specific finite element modelling of periprosthetic femoral fractures in different load cases

Periprosthetic femoral fractures (PFF) around total hip replacements are one of the biggest challenges for orthopaedic surgeons. To understand the risk factors and formation of these fractures, the development of a reliable finite element (FE) model incorporating bone failure is essential. Due to the anisotropic and complex hierarchical structure of bone, the mechanical behaviour under large strains is difficult to predict. In this study, a state-of-the-art subject specific FE modelling technique for bone is utilised to generate and investigate PFF. A bilinear constitutive law is applied to bone tissue in subject specific FE models of five human femurs which are virtually implanted with a straight hip stem to numerically analyse PFF. The material parameters of the models are expressed as a function of bone ash density and mapped node wise to the FE mesh. In this way the subject specific, heterogeneous structure of bone is mimicked. For material mapping of the parameters, computed tomography (CT) images of the original fresh-frozen femurs are used. Periprosthetic fractures are generated by deleting elements on the basis of a critical plastic strain failure criterion. The models are analysed under physiological and clinically relevant conditions in two different load cases re-enacting stumbling and a sideways fall on the hip. The results of the analyses are quantified with experimental data from previous work. With regard to fracture pattern, stiffness and failure load the simulations of the load case stumbling delivered the most stable and accurate results. In general, mapping of material properties was found to be an appropriate way to reproduce PFF with finite element models.

Novel method for determining bone dimensions relevant for longitudinal and transverse distraction osteogenesis and application in the human tibia and fibula

BACKGROUND

In distraction osteogenesis (DO) of long bones, new bone tissue is formed and distracted to lengthen limbs or reconstruct bone defects. However, certain anthropometric quantities relevant for biomechanical modelling of DO are unknown, such as areas where new bone tissue is formed. We developed a novel method to facilitate the determination of these distraction areas (DA), which we applied in the tibia and fibula of adults for longitudinal and transverse DO to advance knowledge of anatomical boundary conditions.

METHODS

CT data sets of 21 adult human tibiae and 24 fibulae were selected for investigation. Volumetric models were created utilizing image segmentation. The DA for longitudinal DO was determined in a CAD environment using the total bone cross section in the proximal, central and distal diaphysis of the tibia and fibula. Additionally, the medullary canal area was determined in the fibula. Furthermore, we measured the total DA and medullary canal DA for transverse distraction using a longitudinally split fibula with an osteotomy length of 8, 12, 16 and 20 cm. The osteotomy plane was oriented in medial and anteromedial direction. Finally, Spearman analyses were conducted to assess the correlation between bone length and DA.

RESULTS

For longitudinal DO, the mean total DAs were 878, 535 and 482 mm² in the tibia and 132, 153, 124 mm² in the fibula for the proximal, central and distal diaphysis, respectively. Regarding transverse distraction, the mean total DAs for a medial and anteromedial osteotomy plane orientation were 962, 1423, 1868 and 2306 mm² as well as 925, 1387, 1844, 2279 mm² for an osteotomy length of 8, 12, 16 and 20 cm, respectively. Weak, positive, and non-significant correlations were observed when correlating bone length and DA in the tibia and fibula.

CONCLUSIONS

Quantification of DAs and hence distracted callus tissue in DO advances anatomical knowledge and improves biomechanical modelling by adding a parameter which cannot be approximated based on bone length.

Numerical simulation of the electric field distribution in an electrical stimulation device for scaffolds settled with cartilaginous cells

Electrical stimulation is a promising approach to enhance cell viability and differentiation. We aim to develop a stimulation device for the investigation and realization of cartilaginous cell engineering. The stimulation setup is capable of applying well-defined electric fields to several scaffolds at the same time. The setup consists of a flat plate with multiple test tubes for the scaffolds. A flexible printed circuit board containing a separate pair of electrodes for each tube is fixed at the bottom of the plate. In this context, numerical simulation using Finite Element Method (FEM) is a valuable tool to gain a better understanding of the electric field distribution in such devices. The thin insulating layer of the flexible printed circuit board allows sufficient field strength to be achieved at moderate input voltages but presents challenges for modelling. In simulations, thin layers would usually require a fine discretization with many degrees of freedom (DOF). This leads to large models, which are expensive regarding memory and computation time. Based on the 'contact impedance' boundary condition available in COMSOL Multiphysics® 5.4, an alternative approach is proposed that can model thin layers in capacitively coupled setups. The resulting electric field distribution in the new stimulation setup is presented and discussed.

The Carrot Not The Stick: Creating Incentives for Voluntary Enforcement of Smoke-Free Policies Through Smoke-Free Zone Certification

Background and context: Jordan's Public Health Law bans smoking in public places. However, law-enforcement mechanisms are lagging and Jordanians continue to be exposed to second-hand smoke. The Global Tobacco Control Report 2017 rates enforcement at 2/10 dropping even below the previous 3/10 rating of 2015. Aim: Our intervention aims to provide alternative routes for protection from exposure to second-hand smoke. Strategy/Tactics: The intervention builds on results from a 2012 survey which indicated that 85% of the public supports banning smoking in healthcare institutions, schools, and work places. In 2013 King Hussein Cancer Foundation and Center launched the Smoke-free Zone Certificate Program in collaboration with Global Smoke-free Worksite Challenge. The program, currently in its fifth round, recognizes institutions that voluntarily enforce smoke-free environments. Program/Policy process: Interested institutions submit an application requesting certification. Applications go through a screening process to confirm initial alignment with the program criteria. Institutions passing the initial screening are physically inspected for compliance through unannounced spot-check visits. Those passing the inspection receive certification. To qualify, an institution should meet two criteria. The first is enforcing a 100% smoke-free policy within all indoor premises. Designated smoking areas are not allowed. For schools, the criteria require that the smoke-free policy extends to cover both indoor and outdoor premises. The second criterion is that the smoke-free policy should be in effect for a minimum of 9 months on the day of certification. The appeal of the program builds on (1) the institution's belief in the importance of providing a safe and healthy environment, (2) the association of the program with the name of a well-respected national organization, and (3) the media exposure that the certified institutions receive. Active promotion of the program is performed during the application period to recruit additional applicants. Outcomes: Fig. 1 depicts the growth in numbers of applications and of certified organizations. On average 67% of applicants receive certification. Interest varies by category with schools outweighing all other applicants (62%). What was learned: Incentives for voluntary enforcement of smoke-free policies have the potential to support law enforcement. The growing interest and the modifications that institutions undergo to meet the program criteria are a testimony to our success. Several institutions went through three rounds of applications prior to receiving certification, indicating the ability of the program to motivate compliance. There is a need to continue to grow the number of applicants especially in the 'restaurants' and 'healthcare' categories. Sensitization about the benefits of smoke-free environments, technical assistance to interested institutions, and additional media exposure can help.

[Figure: see text]

Multicentric Evaluation of a New PT Reagent Based on Recombinant Human Tissue Factor and Synthetic Phospholipids

A new PT reagent based on recombinant human tissue factor and synthetic phospholipids (phosphatidyl choline and phosphatidyl serine) with defined fatty acid side chains was calibrated against BCT/253 and CRM 149R. A small but consistent bias in the International Sensitivity Index (ISI) value was obtained using either the human or rabbit brain reference material. ISI values were around 1.0 or slightly lower depending on the respective instrument. Mixing studies with factor deficient plasmas showed a high factor sensitivity especially for factor VII as compared to commercial rabbit brain or human placenta thromboplastin. In an international field trial the reagent was tested using fully or semi automated Electra™ coagulometers in 4 different laboratories. Results with normal samples were in excellent agreement among the different laboratories. Mean values were 10.9, 10.9, 11.0, 11,7 s with a range of 9.5 to 12.5 s. Results of males and females were not different. In patients with liver disease very similar PT activities were found as compared to sensitive rabbit brain or human placental thromboplastins. In normals and patients with oral anticoagulation INR values correlated very well against BCT (r = 0.98, regression line y =-0.07 + 0.9 x). The distribution of samples was linear over the whole range. In the comparison against sensitive rabbit brain thromboplastin or human placental thromboplastin similar correlations were found. In a few cases higher INR values were observed for the recombinant reagent especially in patients with intensive treatment. Factor assays in those patients showed at least the strong reduction of one vitamin Independent coagulation factor. Over all the linearity was better against the rabbit brain reagent than against the human placental reagent which is slightly less factor VII sensitive as shown in mixing studies with normal and factor VII deficient plasma. Precision studies in the 4 laboratories showed excellent reproducibility of lyophilised controls or local patient plasma pools for all reagents with a better performance of the recombinant reagent. C. V. values from day to day ranged from 1.3% to 5% for normal and abnormal controls.

These results show that the recombinant PT reagent, especially in conjunction with a precise automated instrument, may improve the results of PT testing and thus may lead to better patient care.

Effects of interfacial micromotions on vitality and differentiation of human osteoblasts

Objectives

Enhanced micromotions between the implant and surrounding bone can impair osseointegration, resulting in fibrous encapsulation and aseptic loosening of the implant. Since the effect of micromotions on human bone cells is sparsely investigated, an in vitro system, which allows application of micromotions on bone cells and subsequent investigation of bone cell activity, was developed.

Methods

Micromotions ranging from 25 µm to 100 µm were applied as sine or triangle signal with 1 Hz frequency to human osteoblasts seeded on collagen scaffolds. Micromotions were applied for six hours per day over three days. During the micromotions, a static pressure of 527 Pa was exerted on the cells by Ti6Al4V cylinders. Osteoblasts loaded with Ti6Al4V cylinders and unloaded osteoblasts without micromotions served as controls. Subsequently, cell viability, expression of the osteogenic markers collagen type I, alkaline phosphatase, and osteocalcin, as well as gene expression of osteoprotegerin, receptor activator of NF-κB ligand, matrix metalloproteinase-1, and tissue inhibitor of metalloproteinase-1, were investigated.

Results

Live and dead cell numbers were higher after 25 µm sine and 50 µm triangle micromotions compared with loaded controls. Collagen type I synthesis was downregulated in respective samples. The metabolic activity and osteocalcin expression level were higher in samples treated with 25 µm micromotions compared with the loaded controls. Furthermore, static loading and micromotions decreased the osteoprotegerin/receptor activator of NF-κB ligand ratio.

Conclusion

Our system enables investigation of the behaviour of bone cells at the bone-implant interface under shear stress induced by micromotions. We could demonstrate that micromotions applied under static pressure conditions have a significant impact on the activity of osteoblasts seeded on collagen scaffolds. In future studies, higher mechanical stress will be applied and different implant surface structures will be considered.

Cite this article: J. Ziebart, S. Fan, C. Schulze, P. W. Kämmerer, R. Bader, A. Jonitz-Heincke. Effects of interfacial micromotions on vitality and differentiation of human osteoblasts. Bone Joint Res 2018;7:187–195. DOI: 10.1302/2046-3758.72.BJR-2017-0228.R1.

Cellular fluid shear stress on implant surfaces-establishment of a novel experimental set up

Background

Mechanostimuli of different cells can affect a wide array of cellular and inter-cellular biological processes responsible for dental implant healing. The purpose of this in vitro study was to establish a new test model to create a reproducible flow-induced fluid shear stress (FSS) of osteoblast cells on implant surfaces.

Methods

As FSS effects on osteoblasts are detectable at 10 dyn/cm², a custom-made flow chamber was created. Computer-aided verification of circulation processes was performed. In order to verify FSS effects, cells were analysed via light and fluorescence microscopy.

Results

Utilising computer-aided simulations, the underside of the upper plate was considered to have optimal conditions for cell culturing. At this site, a flow-induced orientation of osteoblast cell clusters and an altered cell morphology with cellular elongation and alteration of actin fibres in the fluid flow direction was detected.

Conclusions

FSS simulation using this novel flow chamber might mimic the peri-implant situation in the phase of loaded implant healing. With this FSS flow chamber, osteoblast cells’ sensitivity to FSS was verified in the form of morphological changes and cell re-clustering towards the direction of the flow. Different shear forces can be created simultaneously in a single experiment.

Devitalisation of human cartilage by high hydrostatic pressure treatment: Subsequent cultivation of chondrocytes and mesenchymal stem cells on the devitalised tissue

The regeneration of cartilage lesions still represents a major challenge. Cartilage has a tissue-specific architecture, complicating recreation by synthetic biomaterials. A novel approach for reconstruction is the use of devitalised cartilage. Treatment with high hydrostatic pressure (HHP) achieves devitalisation while biomechanical properties are remained. Therefore, in the present study, cartilage was devitalised using HHP treatment and the potential for revitalisation with chondrocytes and mesenchymal stem cells (MSCs) was investigated. The devitalisation of cartilage was performed by application of 480 MPa over 10 minutes. Effective cellular inactivation was demonstrated by the trypan blue exclusion test and DNA quantification. Histology and electron microscopy examinations showed undamaged cartilage structure after HHP treatment. For revitalisation chondrocytes and MSCs were cultured on devitalised cartilage without supplementation of chondrogenic growth factors. Both chondrocytes and MSCs significantly increased expression of cartilage-specific genes. ECM stainings showed neocartilage-like structure with positive AZAN staining as well as collagen type II and aggrecan deposition after three weeks of cultivation. Our results showed that HHP treatment caused devitalisation of cartilage tissue. ECM proteins were not influenced, thus, providing a scaffold for chondrogenic differentiation of MSCs and chondrocytes. Therefore, using HHP-treated tissue might be a promising approach for cartilage repair.

Genome wide array-CGH and qPCR analysis for the identification of genome defects in Williams' syndrome patients in Saudi Arabia

Background

Williams-Beuren Syndrome (WBS) is a rare neurodevelopmental disorder characterized by dysmorphic features, cardiovascular defects, cognitive deficits and developmental delay. WBS is caused by a segmental aneuploidy of chromosome 7 due to heterozygous deletion of contiguous genes at the long arm of chromosome 7q11.23. We aimed to apply array-CGH technique for the detection of copy number variants in suspected WBS patients and to determine the size of the deleted segment at chromosome 7q11.23 in correlation with the phenotype. The study included 24 patients referred to the CEGMR with the provisional diagnosis of WBS and 8 parents. The patients were subjected to conventional Cytogenetic (G-banding) analysis, Molecular Cytogenetic (Fluorescent In-Situ Hybridization), array-based Comparative Genomic Hybridization (array-CGH) and quantitative Real time PCR (qPCR) Techniques.

Results

No deletions were detected by Karyotyping, however, one patient showed unbalanced translocation between chromosome 18 and 19, the karyotype was 45,XX, der(19) t(18;19)(q11.1;p13.3)-18. FISH technique could detect microdeletion in chromosome 7q11.23 in 10/24 patients. Array-CGH and qPCR confirmed the deletion in all samples, and could detect duplication of 7q11.23 in three patients and two parents. Furthermore, the size of the deletion could be detected accurately by both array-CGH and qPCR techniques. Three patients not showing the 7q11.23 deletion were diagnosed by array-CGH to have deletion in chr9p13.1-p11.2, chr18p11.32-p11.21 and chr1p36.13.

Conclusion

Both FISH and array-CGH are reliable methods for the diagnosis of WBS; however, array-CGH has the advantage of detection of genome deletions/ duplications that cannot otherwise be detected by conventional cytogenetic techniques. Array-CGH and qPCR are useful for detection of deletion sizes and prediction of the interrupted genes and their impact on the disease phenotype. Further investigations are needed for studying the impact of deletion sizes and function of the deleted genes on chromosome 7q11.23.

Trial registration

ISRCTN ISRCTN73824458. MOCY-D-16-00041R1. Registered 28 September 2014. Retrospectively registered.

Potential infection control risks associated with roaming healthcare industry representatives

BACKGROUND

Healthcare industry representatives (HCIR) visit multiple hospitals every day. Most enter hygiene sensitive areas and work in close proximity to caregivers and patients.

OBJECTIVE

The objective of the present study was to evaluate the HCIRs' current status in hygiene training and vaccination.

METHODS

An anonymous walking intercept study was used based on questionnaires to evaluate industry representatives in comparison to physicians and nurses (n = 311 participants, participation rate 30.2%) after their visit to the MEDICA Congress. The valid participants consisted of HCIR (n = 208), hospital nurses (n = 49) and physicians (n = 41). A total of 82.2% (n = 171) HCIR worked in varying hospitals.

RESULTS

They frequently request access to hygiene and data-privacy sensitive areas: Among them 51.9% (n = 108) accessed the outpatient clinic, 41.8% (n = 87) the operating room (OR), 33.7% (n = 70) the central supply and sterilisation department (CSSD), and 32.7% (n = 68) the intensive care unit. HCIR requesting access to hygiene sensitive areas showed the lowest scores in hygiene training and a significantly lower Hepatitis B vaccination status, i.e. 37.5% compared to 70.7% for physicians and 53.1% for nurses.

DISCUSSION

Status of HCIR hygiene training was inadequate - as was vaccination and contamination control. Therefore, HCIR are exposed to increased infection risk and may unknowingly act as infection vector between different hospitals.

Investigation of the inverse piezoelectric effect of trabecular bone on a micrometer length scale using synchrotron radiation

In the present paper we have investigated the impact of electro stimulation on microstructural parameters of the major constituents of bone, hydroxyapatite and collagen. Therapeutic approaches exhibit an improved healing rate under electric fields. However, the underlying mechanism is not fully understood so far. In this context one possible effect which could be responsible is the inverse piezo electric effect at bone structures. Therefore, we have carried out scanning X-ray microdiffraction experiments, i.e. we recorded X-ray diffraction data with micrometer resolution using synchrotron radiation from trabecular bone samples in order to investigate how the bone matrix reacts to an applied electric field. Different samples were investigated, where the orientation of the collagen matrix differed with respect to the applied electric field. Our experiments aimed to determine whether the inverse piezo electric effect could have a significant impact on the improved bone regeneration owing to electrostimulative therapy. Our data suggest that strain is in fact induced in bone by the collagen matrix via the inverse piezo electric effect which occurs in the presence of an adequately oriented electric field. The magnitude of the underlying strain is in a range where bone cells are able to detect it.

STATEMENT OF SIGNIFICANCE

In our study we report on the piezoelectric effect in bone which was already discovered and explored on a macro scale in the 1950. Clinical approaches utilize successfully electro stimulation to enhance bone healing but the exact mechanisms taking place are still a matter of debate. We have measured the stress distribution with micron resolution in trabecular bone to determine the piezo electric induced stress. Our results show that the magnitude of the induced stress is big enough to be sensed by cells and therefore, could be a trigger for bone remodeling and growth.

[Quality of Outcome after Primary Total Hip Replacement at a Maximum Care Hospital in Relation to Preoperative Influencing Factors]

BACKGROUND

As the need for joint replacements will continue to rise, the outcome of primary total hip replacement (THR) must be improved and stabilised at a high level. In this study, we investigated whether pre-operative risk factors, such as gender, age and body weight at the time of the surgery or a restricted physical status (ASA-Status > 2 or Kellgren and Lawrence grade > 2) have a negative influence on the post-operative results or on patient satisfaction.

MATERIAL AND METHODS

Retrospective data collection and a prospective interview were performed with 486 patients who underwent primary total hip replacement between January 2007 and December 2010 in our hospital. The patients' satisfaction and quality of life were surveyed with the WOMAC-Score, SF-36 and EuroQol-5. Differences between more than two independent spot tests were tested with the non-parametric Kruskal-Wallis test. Differences between two independent spot tests were tested with the non-parametric Mann-Whitney U test. The frequencies were reported and odds ratios calculated. The confidence interval was set at 95 %. The level of significance was p < 0.05.

RESULTS

The average WOMAC-Score was 77.1 and the total score of the SF-36 was 66.9 points. The patients declared an average EuroQol Index of 0.81. Our data show that the patients' gender did not influence the duration of surgery or the scores. However, female patients tended to exhibit more postoperative complications. However, increased patient age at the time of surgery was associated with an increased OR for duration of surgery, length of stay and risk of complications. Patients who had a normal body weight at time of the surgery showed better peri- and post-operative results. We showed that the preoperative estimated Kellgren and Lawrence grade had a significant influence on the duration of surgery. The ASA classification influenced the duration of surgery as well the length of stay and the rate of complications.

CONCLUSION

The quality of results after primary THR depends on preoperative factors. Existing comorbidities have a significant influence on the duration of surgery and therefore on the perioperative rate of complications and the postoperative outcome. Despite improvements in the functional and subjective outcome after primary THR, an adverse preoperative symptomatic status is associated with less favourable postoperative results.

Influence of short-term fixation with mixed formalin or ethanol solution on the mechanical properties of human cortical bone

Bone specimens obtained for biomechanical experiments are fresh-frozen for storage to slow down tissue degradation and autolysis in long-term storage. Alternatively, due to infectious risks related to the fresh tissues, fixative agents are commonly used. However, fixatives will likely change the mechanical properties of bone. Existing studies on this issue gave controversial results that are hardly comparable due to a variety of measurement approaches. For this reason, the influence of ethanol and a formalin-based fixative agent was evaluated on the mechanical properties of human cortical bone specimens by means of four-point-bending tests. 127 prismatic specimens with rectangular cross sections (2.5 x 2.5 x 20 mm3) were obtained from different regions of two fresh human femora (medial, lateral, dorsal, ventral). Specimens were either fixed in ethanol or in a mixed formalin solution or frozen following a given scheme. After two weeks of storage the samples were re-hydrated in isotonic saline and subsequently tested mechanically. The elastic bending modulus and ultimate bending strength were computed considering the actual dimensions of each specific specimen. For statistical analysis a one-way-ANOVA and an LSD post-hoc-test were performed. For ultimate bending strength no significant differences due to formalin or ethanol fixation, as compared to unfixed-fresh bone specimens could be found. And only for few cases significant differences in elastic bending modulus were observed when the two bones were evaluated separately. Since more differences of significant level due to the anatomical region of the samples were determined, the original location seems to have more influence on the evaluated mechanical properties than the method of (chemical) fixation. Consequently, ethanol and the mixed formalin solution can be recommended as a fixation agent for samples in biomechanical testing, if these samples are rinsed in isotonic saline prior to static mechanical testing.

The influence of metallic ions from CoCr28Mo6 on the osteogenic differentiation and cytokine release of human osteoblasts

Inflammatory reactions associated with osteolysis and implant loosening can be the result of generated CoCr particles and the simultaneous release of ions, which are the consequence of wear at the articulating surfaces of metallic implants. By now, there is little knowledge about the influence of CoCr ions on the viability of human osteoblasts (hOB).

Therefore, metallic ions were generated from solid CoCr28Mo6 alloys using electric potentials against hydrogen bridge electrodes. For the cell experiments, hOBs (n ≥ 4) in the third passage were used. Cells were cultured for 24 h before incubated with the generated ion solution in two different concentrations (100 µg/l and 500 µg/l in DMEM with 10 % FCS). Cells incubated without ions served as controls. After 48 h and 96 h cell viability was determined (WST-1 assay, live-dead-stainings). Additionally, gene expression levels of osteogenic markers and cytokines were analysed.

A significant increase of metabolic activity and vital cells could be shown for both ion concentrations. Gene expression of alkaline phosphatase and Col1 was highly induced after 96 h for 100 µg/l whereas Col1 protein was significantly reduced on both time points (48 h: p=0.008 (100 µg/l, 500 µg/l); 96 h: p=0,029 (500 µg/l)) compared to the control. Additionally, MMP1 expression was decreased after 48 h and 96 h. IL6 mRNA was concentration-dependent increased after 48 h whereas a significant decrease could be shown for the highest ion concentration (p=0.029). Compared to the lower ion concentration, IL8, MCP1 (p=0.029) and TNF mRNA were clearly reduced for the higher ion solution after 96 h. Our results suggest that ions from CoCr28Mo6 alloys have only marginal effects on osteoblast viability whereas Col1 expression is reduced and cytokine release is induced. In further studies, the effects of metallic ions and particles from CoCr28Mo6 on other cells will be examined.

Simulation of varying femoral attachment sites of medial patellofemoral ligament using a musculoskeletal multi-body model

The medial patellofemoral ligament (MPFL) is a key structure in the treatment of habitual and traumatic patellofemoral instability. However, there exists little knowledge about its behaviour during deep knee flexion after femoral refixation. Since improper femoral attachment sites may lead to unnatural length change patterns in the ligament and consequently to osteoarthritis due to pathological femoro-patellar contact pressure, the understanding of the patella kinematics and MPFL behaviour is crucial.

The purpose of this numerical study was to compute the six-degree-of-freedom motion pattern of the human patella during deep knee flexion for systematic analysis of varying landmarks for the femoral attachment in medial patellofemoral ligament reconstruction surgery by means of multibody simulation.

Therefore, based on a previously presented musculoskeletal model [1] the dynamic pathways of the patella were computed. Then, the spatial motion was approximated by rheonomic polynomials and exploited for systematic evaluation of the MPFL length change patterns. Hence, 16 femoral attachment points at a radius of 5 mm and 10 mm around the radiographic centre point [2] were defined and the absolute length changes were recorded during deep knee flexion to 120 degree.

This approach allows for a systematic evaluation of numerous MPFL attachment sites while exploiting the physiological patella kinematics. The patella kinematics including shift, flexion, tilt and rotation as well as the MPFL length change patterns were consistent to in vitro and in vivo data in the literature [3–7] and therefore indicate validity of the numerical approach. The parameter study on the femoral attachment site should enable to determine the most isometric point and non-isometric variations corresponding to patellofemoral instability, arthritis or high graft load.

[Influence of surgeon experience in total hip arthroplasty. Dependence on operating time and complication risk]

BACKGROUND

As a consequence of limited personnel and financial resources, the increase in total hip arthroplasties places higher demands on orthopedic surgeons.

OBJECTIVES

In order to maintain high quality treatment, the correlation between surgical experience, duration of surgery and risk of complications was examined.

MATERIAL AND METHODS

The surgery time and, if applicable, complications (until discharge from hospital) of 1129 total hip arthroplasties over a period of 4 years were evaluated retrospectively.

RESULTS

The group of most experienced surgeons needed an average time of 53.2 ± 17.6 min for each implantation, followed by moderately experienced surgeons (74.5 ± 25.5 min) and less experienced surgeons (80.8 ± 21.9 min). Of all included cases, a total of 41 complications until discharge from hospital occurred. The number of complications increased with duration of surgery, whereby the risk of complications was significantly lower for shorter surgery times conducted by the most experienced surgeons as well as moderately experienced surgeons. The complication risk of less experienced surgeons remained constant independent of surgery duration.

CONCLUSION

These results underline the recommendations of the German Endocert system, which determine a minimum number of total joint arthroplasties as a quality indicator not only for hospitals but also for individual surgeons.

[Reimbursement in psychiatry and psychosomatics: proof of concept for a system based on daily costs]

BACKGROUND

In Germany a new reimbursement system for psychiatry and psychosomatics is under development. Based on total costs of each case from selected hospitals and day clinics, in 2013 the Institute for the Hospital Remuneration System (InEK) proposed to reimburse the hospital costs daily with step-wise decreasing remuneration, mainly depending on the ICD-10 diagnosis, duration of stay and some complicating factors (PEPP grouper). It is controversial whether this degressive system will result in an inadequate remuneration of patients with longer duration of severe symptoms, such as suicidality in depression or autoaggressive behavior in borderline personality disorder and will eventually lead to advantages for acutely ill patients with short duration of stay compared to chronically ill patients.

OBJECTIVES

This study formulated and tested an alternative remuneration system (proof of concept) mainly based on an analysis of daily cost data instead of the total costs of each case.

MATERIAL AND METHODS

The study is based on 147,749 treatment days from 4,633 cases of patients with psychotic disorders (PEPP-PA03) in 6 hospitals. As possible cost separating factors the study analyzed days with and without intensive psychiatric care, 1 to 1 care, psychological diagnostics, magnetic resonance imaging (MRI), acute crisis intervention, age at admission, the first days of treatment and day of discharge.

RESULTS AND DISCUSSION

Nearly all factors tested were shown to be statistically significant in separating daily hospital costs. Based on these findings an alternative calculation algorithm (TEPPconcret), which grouped the cases with respect to age, intensive care, 1 to 1 care, treatment days 1-4 and day of discharge, was formulated and tested. For psychotic disorders TEPPconcret with a basic rate complemented by daily add-on payments depending on the effort involved, is a serious alternative to the PEPP system and awaits further evaluation.

[Failure analysis as basis for quality assurance strategies in implant technology]

BACKGROUND

Implant safety is a topic gaining more and more public interest. Implants are safety relevant medical devices which in the case of failure can lead to life-threatening situations.

OBJECTIVES

A well-founded failure analysis requires expert knowledge not only of materials and implant design but also a qualified explantation procedure and storage conditions.

METHODS

A selective literature search was carried out putting the main emphasis on implant failure analysis supplemented with own investigations.

RESULTS

The reasons for implant breakdown are mostly failures of materials and in the manufacturing process. In some cases false material combinations can lead to tribocorrosion effects under cyclic loading.

CONCLUSION

The increased level of knowledge gained from complex analyses of failed implants produces valuable evidence for better quality management.

The IGFBP7 homolog Imp-L2 promotes insulin signaling in distinct neurons of the Drosophila brain

In Drosophila, Insulin-like peptide 2 (Dilp-2) is expressed by insulin-producing cells in the brain, and is secreted into the hemolymph to activate insulin signaling systemically. Within the brain, however, a more local activation of insulin signaling may be required to couple behavioral and physiological traits to nutritional inputs. We show that a small subset of neurons in the larval brain has high Dilp-2-mediated insulin signaling activity. This local insulin signaling activation is accompanied by selective Dilp-2 uptake and depends on the expression of the Imaginal morphogenesis protein-late 2 (Imp-L2) in the target neurons. We suggest that Imp-L2 acts as a licensing factor for neuronal IIS activation through Dilp-2 to further increase the precision of insulin activity in the brain.

[Principles of tribological analysis of endoprostheses]

For the tribological characterization of artificial joints, various experimental methods are currently available. However, the in vitro test conditions applied are only comparable in a limited way and transferability to the in vivo situation is also restricted. This is due to the different wear simulation concepts used and partly insufficient simulation of clinical worst case situations. In the present paper current scientific methods and procedures for tribological testing of artificial joints are presented. In addition, the biological effects of wear products are described enabling clinicians to challenge tribological studies and to facilitate specific interpretation of scientific results taking the clinical situation into account.

[Recommendations for documentation of incidents with medical devices in orthopaedic surgery]

The growing number of revisions in orthopaedic surgery as well as the multifactorial reasons for implant failure give cause for taking a closer look at the clinical documentation of adverse events. Based on our long-term experience it is our goal to present recommendations for an adequate documentation and filing. In the framework of the introduction of a quality management system (ISO 9001:2008) in our hospital, a process was developed for reportable incidents with medical devices regulating adequate documentation. Therefore, specific forms were developed. The retrievals are stored for subsequent damage analyses and are available for possible legal claims and tracking. A file should be opened for each reportable incident containing information about the event, a copy of the obligatory BfArM report, surgery report, medical device labels, radiographs and photographs. Declarations of agreement as well as handover certificates should be maintained in order to keep record of the retrievals. In order to assure consistent documentation, we recommend use of specific forms as presented in this paper. Identification of risk factors for implant failure and a long-term reduction of damage cases will only be possible under consequent incident reporting and responsible documentation of adverse events. Processing of cases of damage is accelerated and simplified by the presented recommendations and forms. Together with the newly established joint replacement registry, a higher quality of patient treatment and implant safety should be obtained.

[Musculoskeletal modeling of the patellofemoral joint. Dynamic analysis of patellar tracking]

Numerical simulations contribute to the understanding of patellofemoral diseases. Whereas cadaveric studies are limited with respect to reproducibility of results, the impact of different operative approaches can be systematically evaluated based on mathematical models. The objective of this study was to introduce a musculoskeletal model which is capable of describing the dynamic interactions within the patellofemoral joint. It contains major bony and soft tissue structures of the right leg including the medial patellofemoral ligament (MPFL). Two operative approaches were considered based on the model to illustrate the effect on patellofemoral biomechanics during active knee flexion: On the one hand the effect of femoral insertion during MPFL reconstruction on medial soft tissue tension, and on the other hand the difference in patella kinematics before and after total knee arthroplasty. Finally, the potential of musculoskeletal models is discussed.

Adenoviral transduction supports matrix expression of alginate cultured articular chondrocytes

The present study examines the effects of adenoviral (Ad) transduction of human primary chondrocyte on transgene expression and matrix production. Primary chondrocytes were isolated from healthy articular cartilage and from cartilage with mild osteoarthritis (OA), transduced with an Ad vector and either immediately cultured in alginate or expanded in monolayer before alginate culture. Proteoglycan production was measured using dimethylmethylene blue (DMMB) assay and matrix gene expression was quantified by real-time PCR. Viral infection of primary chondrocytes results in a stable long time transgene expression for up to 13 weeks. Ad transduction does not significantly alter gene expression and matrix production if chondrocytes are immediately embedded in alginate. However, if expanded prior to three dimension (3D) culture in alginate, chondrocytes produce not only more proteoglycans compared to non-transduced controls, but also display an increased anabolic and decreased catabolic activity compared to non-transduced controls. We therefore suggest that successful autologous chondrocyte transplantation (ACT) should combine adenoviral transduction of primary chondrocytes with expansion in monolayer followed by 3D culture. Future studies will be needed to investigate whether the subsequent matrix production can be further improved by using Ad vectors bearing genes encoding matrix proteins.

Evaluation of antimicrobial effects of novel implant materials by testing the prevention of biofilm formation using a simple small scale medium-throughput growth inhibition assay

Staphylococcal colonization of implants is a serious complication of orthopaedic surgery. Anti-infectious modification of implant surfaces may serve to prevent bacterial colonization. The authors set out to develop an in vitro test system for the analysis of prevention of biofilm formation by Staphylococcus epidermidis and Staphylococcus aureus on implant materials. Biofilm growth was monitored over 10 days on titanium disks in order to develop appropriate test parameters. Bacterial cell counts following ultrasonic treatment of the colonized samples were compared with scanning electron microscope images of the specimens. Copper ion containing surfaces (ie copper [Cu] and inter-metallic Ti-Cu films) were used for growth inhibition assays: copper ion releasing specimens led to reduced bacterial numbers in biofilms and decreased bacterial persistence in the model used. The assay used represents an inexpensive and quick in vitro screen for the antibacterial effects of novel implant surface materials.

[Biphosphonate-induced femoral stress fractures : A new problem and knowledge so far - case report]

During the last several years the treatment of osteoporosis with bisphosphonates has become accepted as a safe and effective procedure. However, recently there have been increasing numbers of reports of rare complications in the literature. Particularly the occurrence of atypical fractures of the femur has become a focus of interest but the problem is insufficiently known and only rarely addressed in the scientific discussion. The case illustrated here and a survey of the important facts in the recent literature highlight essential aspects of long-term bisphosphonate therapy.