Dynamic radiostereometry can objectively quantify the kinematic laxity patterns and rotation instability of the knee during a pivot-shift test.

PURPOSE: The pivot-shift test is used to clinically assess knee instability in patients with anterior cruciate ligament (ACL) lesions; however, it has low interobserver reliability. Dynamic radiostereometry (dRSA) is a highly precise and noninvasive method for the objective evaluation of joint kinematics. The purpose of this study was to quantify precise knee kinematics during a pivot-shift test using dRSA imaging. METHOD: Eight human donor legs, including hemipelvises, were evaluated. Arthroscopic intervention was performed inducing ligament lesions in the ACL, and anterolateral ligament (ALL) section was performed as a capsular incision. The pivot-shift test was recorded with dRSA on knees with intact ligaments, ACL-deficient and ACL + ALL-deficient knees. RESULTS: A pivot-shift pattern was identifiable after ligament lesion, as a change in tibial posterior drawer velocity from 7.8 mm/s (95% CI: 3.7; 11.9) in ligament intact knees to 30.4 mm/s (95% CI 23.0; 38.8) after ACL lesion to 35.1 mm/s (95% CI 23.4; 46.7) after combined ACL-ALL lesion. The anterior-posterior drawer excursion increased from 2.8 mm (95% CI 2.1; 3.4) in ligament intact knees to 7.2 mm (95% CI 5.5; 8.9) after ACL lesion to 7.6 mm (95% CI 5.5; 9.8) after combined lesion. A statistically significant increase in tibial external rotation towards the end of the pivot-shift motion was observed when progressing from intact to ACL + ALL-deficient knees (p < 0.023). CONCLUSION: This experimental study demonstrates the feasibility of dRSA to objectively quantify the kinematic laxity patterns of the knee during the pivot-shift test. The dynamic parameters obtained through dRSA revealed the kinematic changes from ACL to combined ACL-ALL ligament lesion. LEVEL OF EVIDENCE: Not applicable.

Radiostereometric analysis: comparison of radiation dose and precision in digital and computed radiography.

BACKGROUND: Radiostereometric Analysis (RSA) is used to measure fixation of joint prosthesis. This study compared radiation dose and image quality of a digital radiography (DR) RSA system and a computed radiography (CR) RSA system in a clinical setting. METHODS: RSA recordings of 24 hips and shoulders were analyzed. We compared two systems: (1) Arcoma T0 with ST-VI image plates and Profect CR-IR 363 reader to (2) AdoraRSA with CXDI-70C wireless DR detectors in a clinical uniplanar RSA set-up with a ± 20 degrees tube angulation and 35 cm × 43 cm detectors. Effective dose was calculated using dedicated software. Image quality was evaluated using calibration errors as calculated by the RSA software. RESULTS: The mean dose for hips was 0.14 (SD 0.04) mSv in the CR system and 0.05 (SD 0.02) mSv in the DR system. The mean dose for shoulders was 0.16 (SD 0.07) mSv in the CR system and 0.09 (SD 0.03) mSv in the DR system. Radiation dose was 64% (p < 0.001) and 43% (p = 0.03) lower in the DR system compared with the CR system for hip and shoulder RSA, respectively. Image quality was better for the DR system with 60-80% less calibration errors compared to the CR system. CONCLUSION: Owing to highly efficient detectors and added filtration at the x-ray tubes, the DR system considerably reduced radiation dose compared with the CR system without compromising image quality. Based on the findings in this study, we recommend replacing CR RSA systems with DR RSA systems. REGISTRATION: Patients were selected from clinical studies performed on the two systems and approved by the local ethics committee [20060165, M-20100112, M-20070082, M-20110224, and 20070258] and registered with ClinicalTrials.gov [NCT00408096, NCT01289834, NCT00913679, NCT02311179, and NCT00679120].

The Right to Repair Software-Dependent Medical Devices.

The "right to repair" movement highlights opportunities to reduce health care costs and promote public health resilience through increased competition in the way in which medical devices are serviced and updated over their lifespan. We review legislative and legal facets of third-party repair of medical devices, and conclude with specific recommendations to help this market function more efficiently to the benefit of patients and health care systems.

Development, construction, and validation of a thinner uniplanar calibration cage for radiostereometry.

Radiostereometric analysis (RSA) is an accurate and precise radiographic method that can be used to measure micromotion of implants and study joint kinematics in vivo. A calibration cage with radiopaque markers is used to calibrate the RSA images; however, the thickness (250 mm) of the calibration cage restricts the available area for the patient and equipment during RSA recordings. A thinner calibration cage would increase the recording area, facilitate handling of the cage, and ease integration of the cage with the RSA system. We developed a thinner calibration cage without compromise of accuracy and precision. First, we performed numerical simulations of an RSA system, and showed that the calibration cage thickness could be decreased to 140 mm maintaining accuracy and precision using 40 fiducial and 30 control markers. Second, we constructed a new calibration cage (NRT cage) according to the simulation results. Third, we validated the new calibration cage against two state-of-the-art calibration cages (Umeaa cage and Leiden cage) in a phantom study. All cages performed similar for marker-based analysis, except for y-rotation, where the Umeaa cage (SD = 0.064 mm) was less precise compared to the NRT (SD = 0.038 mm) and Leiden cages (0.042 mm) (p = .01). For model-based analysis the NRT cage had superior precision for translations (SD ≤ 0.054 mm) over the Leiden cage (SD ≤ 0.118 mm) and Umeaa cage (SD ≤ 0.093 mm) (p < .01). The combined study confirmed that the new and thinner calibration cage maintained accuracy and precision at the level of existing thicker calibration cages.

Assessment of knee kinematics with dynamic radiostereometry: Validation of an automated model-based method of analysis using bone models.

Radiostereometic analysis (RSA) is a precise method for the functional assessment of joint kinematics. Traditionally, the method is based on tracking of surgically implanted bone markers and analysis is user intensive. We propose an automated method of analysis based on models generated from computed tomography (CT) scans and digitally reconstructed radiographs. The study investigates method agreement between marker-based RSA and the CT bone model-based RSA method for assessment of knee joint kinematics in an experimental setup. Eight cadaveric specimens were prepared with bone markers and bone volume models were generated from CT-scans. Using a mobile fixture setup, dynamic RSA recordings were obtained during a knee flexion exercise in two unique radiographic setups, uniplanar and biplanar. The method agreement between marker-based and CT bone model-based RSA methods was compared using bias and LoA. Results obtained from uniplanar and biplanar recordings were compared and the influence of radiographic setup was considered for clinical relevance. The automated method had a bias of -0.19 mm and 0.11° and LoA within ±0.42 mm and ±0.33° for knee joint translations and rotations, respectively. The model pose estimation of the tibial bone was more precise than the femoral bone. The radiographic setup had no clinically relevant effect on results. In conclusion, the automated CT bone model-based RSA method had a clinical precision comparable to that of marker-based RSA. The automated method is non-invasive, fast, and clinically applicable for functional assessment of knee kinematics and pathomechanics in patients.

Mechanism Based Flow Stress Model for Alloy 625 and Alloy 718.

To predict the final geometry in thermo-mechanical processes, the use of modeling tools is of great importance. One important part of the modeling process is to describe the response correctly. A previously published mechanism-based flow stress model has been further developed and adapted for the nickel-based superalloys, alloy 625, and alloy 718. The updates include the implementation of a solid solution strengthening model and a model for high temperature plasticity. This type of material model is appropriate in simulations of manufacturing processes where the material undergoes large variations in strain rates and temperatures. The model also inherently captures stress relaxation. The flow stress model has been calibrated using compression strain rate data ranging from 0.01 to 1 s-1 with a temperature span from room temperature up to near the melting temperature. Deformation mechanism maps are also constructed which shows when the different mechanisms are dominating. After the model has been calibrated, it is validated using stress relaxation tests. From the parameter optimization, it is seen that many of the parameters are very similar for alloy 625 and alloy 718, although it is two different materials. The modeled and measured stress relaxation are in good agreement.

Simulation of Ti-6Al-4V Additive Manufacturing Using Coupled Physically Based Flow Stress and Metallurgical Model.

Simulating the additive manufacturing process of Ti-6Al-4V is very complex due to the microstructural changes and allotropic transformation occurring during its thermomechanical processing. The α -phase with a hexagonal close pack structure is present in three different forms-Widmanstatten, grain boundary and Martensite. A metallurgical model that computes the formation and dissolution of each of these phases was used here. Furthermore, a physically based flow-stress model coupled with the metallurgical model was applied in the simulation of an additive manufacturing case using the directed energy-deposition method. The result from the metallurgical model explicitly affects the mechanical properties in the flow-stress model. Validation of the thermal and mechanical model was performed by comparing the simulation results with measurements available in the literature, which showed good agreement.

Impact of solvent quality on the network strength and structure of alginate gels.

The influence of the mixture of water and alcohols on the solubility and properties of alginate and its calcium-induced gels is of interest for the food, wound care and pharmaceutical industries. The solvent quality of water with increasing amounts of ethanol (0-20%) on alginate was studied using intrinsic viscosity. The effect of ethanol addition on the rheological and mechanical properties of calcium alginate gels was determined. Small-angle X-ray scattering and transmission electron microscopy were used to study the network structure. It is shown that the addition of ethanol up to 15% (wt) increases the extension of the alginate chain, which correlates with increased moduli and stress being required to fracture the gels. The extension of the polymer chain is reduced at 20% (wt) ethanol, which is followed by reduced moduli and stress at breakage of the gels. The network structure of gels at high ethanol concentrations (24%) is characterized by thick and poorly connected network strands.

The Discover artificial disc replacement versus fusion in cervical radiculopathy--a randomized controlled outcome trial with 2-year follow-up.

BACKGROUND CONTEXT: Several previous studies comparing artificial disc replacement (ADR) and fusion have been conducted with cautiously positive results in favor of ADR. This study is not, in contrast to most previous studies, an investigational device exemption study required by the Food and Drug Administration for approval to market the product in the United States. This study was partially funded with unrestricted institutional research grants by the company marketing the artificial disc used in this study. PURPOSE: To compare outcomes between the concepts of an artificial disc to treatment with anterior cervical decompression and fusion (ACDF) and to register complications associated to the two treatments during a follow-up time of 2 years. STUDY DESIGN/SETTING: This is a randomized controlled multicenter trial, including three spine centers in Sweden. PATIENT SAMPLE: The study included patients seeking care for cervical radiculopathy who fulfilled inclusion criteria. In total, 153 patients were included. OUTCOME MEASURES: Self-assessment with Neck Disability Index (NDI) as a primary outcome variable and EQ-5D and visual analog scale as secondary outcome variables. METHODS: Patients were randomly allocated to either treatment with the Depuy Discover artificial disc or fusion with iliac crest bone graft and plating. Randomization was blinded to both patient and caregivers until time for implantation. Adverse events, complications, and revision surgery were registered as well as loss of follow-up. RESULTS: Data were available in 137 (91%) of the included and initially treated patients. Both groups improved significantly after surgery. NDI changed from 63.1 to 39.8 in an intention-to-treat analysis. No statistically significant difference between the ADR and the ACDF groups could be demonstrated with NDI values of 39.1 and 40.1, respectively. Nor in secondary outcome measures (EQ-5D and visual analog scale) could any statistically significant differences be demonstrated between the groups. Nine patients in the ADR group and three in the fusion group underwent secondary surgery because of various reasons. Two patients in each group underwent secondary surgery because of adjacent segment pathology. Complication rates were not statistically significant between groups. CONCLUSIONS: Artificial disc replacement did not result in better outcome compared to fusion measured with NDI 2 years after surgery.

Magnet design for a low-emittance storage ring.

The MAX IV 3 GeV storage ring, currently under construction, pursues the goal of low electron beam emittance by using a multi-bend achromat magnet lattice, which is realised by having several consecutive magnet elements precision-machined out of a common solid iron block, 2.3-3.4 m long. With this magnet design solution, instead of having 1320 individual magnets, the MAX IV 3 GeV storage ring is built up using 140 integrated `magnet block' units, containing all these magnet elements. Major features of this magnet block design are compactness, vibration stability and that the alignment of magnet elements within each unit is given by the mechanical accuracy of the CNC machining rather than individual field measurement and adjustment. This article presents practical engineering details of implementing this magnet design solution, and mechanical + magnetic field measurement results from the magnet production series. At the time of writing (spring 2014), the production series, which is totally outsourced to industry, is roughly half way through, with mechanical/magnetic QA conforming to specifications. It is the conclusion of the authors that the MAX IV magnet block concept, which has sometimes been described as new or innovative, is from a manufacturing point of view simply a collection of known mature production methods and measurement procedures, which can be executed at fixed cost with a low level of risk.

White light with phosphorescent protein fibrils in OLEDs.

Red and yellow phosphorescent insulin amyloid fibrils are used as guest-emitting species within a blue-emitting polyfluorene matrix in light-emitting diodes. The integration of the phosphorescent Ir-complex into the amyloid structures strongly improves the triplet exciton confinement and allows the fabrication of white-emitting device with a very low loading of phosphorescent complex. The overall performances of the devices are improved in comparison with the corresponding bare Ir-complexes. This approach opens a way to explore novel device architectures and to understand the exciton/charge transfer dynamics in phosphorescent light emitting diodes.

Enhanced current efficiency from bio-organic light-emitting diodes using decorated amyloid fibrils with conjugated polymer.

We demonstrate the use of self-assembled bionanostructures in polymer light-emitting diodes. Amyloid fibrils formed by protein misfolding were decorated with a soluble luminescent conjugated polymer. This conjugated polymer complex with amyloid fibrils was used as the active layer in a light emitting diode, resulting in a 10-fold increase in external quantum efficiency compared with pristine polymer, because of improved carrier injection.

Effect of supplementary amine fluoride gel in caries-active adolescents. A clinical QLF study.

OBJECTIVE: To investigate whether supplementary daily use of amine fluoride toothpaste with weekly brushing with amine fluoride gel enhances the remineralization of white spot lesions on smooth surfaces and also to investigate the possible effect of this treatment on salivary bacterial counts and oral hygiene. MATERIAL AND METHODS: The participants comprised 135 caries-active adolescents living in suburban Stockholm. They were given an amine fluoride dentifrice (1250 ppm F) to be used twice a day, and either a test gel (4000 ppm F) or a placebo gel for brushing for 2 min once a week. During the 12-month study period, the subjects were recalled every 3rd month (baseline, 3, 6, 9, and 12 months). At each visit, DF(average change in fluorescence, in%) and lesion area (in mm2) were measured using quantitative light-induced fluorescence(QLF), followed by dietary counseling, oral hygiene instruction, and professional tooth-cleaning. At baseline, 6, and 12 months, saliva was sampled for Streptococcus mutans and lactobacillus counts, and gingival bleeding index was registered. RESULTS: QLF indicated no enhancement of remineralization of white spot lesions by additional weekly brushing with amine fluoride gel. No inter-group differences emerged with regard to salivary bacterial counts. However, the oral hygiene of both groups improved, with a strong significance over time. CONCLUSION: Adjunctive weekly brushing of amine fluoride gel achieved no significant enhancement of remineralization of white spot lesions monitored with the QLF method.

Blood pharmacokinetics of various monoclonal antibodies labeled with a new trifunctional chelating reagent for simultaneous conjugation with 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid and biotin before radiolabeling.

PURPOSE: Knowledge of the blood pharmacokinetics of monoclonal antibodies is crucial in deciding the optimal time for starting the administration of a "clearing agent" or using a "clearing device." The primary purpose was to investigate whether the pharmacokinetics of various antibodies labeled with the same chelator and (111)In differed significantly after i.v. injection in immunocompetent rats. A new trifunctional chelator called "1033" containing a biotin and a radiometal chelation moiety is introduced, making it possible to use only one conjugation procedure for the antibody. EXPERIMENTAL DESIGN: Sixty-five non-tumor-bearing rats were included and divided into four groups (I-IV). The blood pharmacokinetics was investigated for rituximab, BR96, and trastuzumab labeled with 1033 and (111)In (I-III). The whole-body activity and activity uptake in muscle, liver, and kidney, which might explain differences in the early pharmacokinetics in blood, were also measured. hMN14 labeled with another chelator [1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)], but with the same radionuclide ((111)In-biotin-DOTA-hMN14), was studied (IV). The blood pharmacokinetics from another 15 tumor-bearing rats was compared with those of non-tumor-bearing rats (III) by injection of (111)In-1033-BR96. RESULTS: No statistical difference was detected between the groups regarding the blood pharmacokinetics of rituximab, BR96, or trastuzumab. The pharmacokinetics and biodistribution of (111)In-biotin-DOTA-hMN14 exhibited a clear difference compared with others. There were no significant differences in the blood pharmacokinetics of (111)In-1033-BR96 between tumor-bearing rats and non-tumor-bearing rats. CONCLUSIONS: Different antibodies labeled with the trifunctional chelator 1033 and (111)In did not exhibit different blood pharmacokinetics, which means that the pharmacokinetics could be predicted irrespective of the IgG1 antibody chosen. A small tumor burden did not change the pharmacokinetics of the radioimmunoconjugates.

In vivo validity and reliability of IR fluorescence measurements for caries detection and quantification.

Studies of detection and quantification of dental caries by KaVo DIAGNOdent have shown high diagnostic accuracy and high inter-operator agreement in vitro. The aim of the present study was to determine whether comparable results could be achieved under clinical conditions. In Part I (occlusal surfaces), 52 occlusal sites (suspected caries) were examined by visual inspection, bitewing radiography, and two DIAGNOdent devices. The fissures were then opened, and lesion depth established according to a four point scale. In Part II (smooth surfaces), two operators performed DIAGNOdent measurements of incipient carious lesions on the buccal surface of 30 molar teeth. The readings were compared with corresponding measurements by Quantitative Light-induced Fluorescence (deltaF). The results for occlusal surfaces disclosed very low correlation between lesion depth and readings by the two DIAGNOdent devices. The intra-operator agreements were very good (0.80-0.92), and the inter-operator agreement was good (0.71-0.87). A significant systematic difference in readings by the two devices precludes general recommendations of cut-off levels. However, individually suitable cut-off values for dentinal lesions gave good qualitative information about the surface (77%-85% over all correct observations), rather than quantitative information in terms of lesion depth within the dentine. In this context, the DIAGNOdent device might be of help for the clinician in the process of decision making about invasive therapy. For smooth surfaces, the correlation between readings obtained with the DIAGNOdent device and deltaF were acceptable (0.57-0.73). The intra-operator agreement was 0.94 for both operators (excellent), and the inter-operator agreement ranged from 0.79 to 0.87 (very good).

In vivo repeatability and reproducibility of the quantitative light-induced fluorescence method.

In vivo repeatability and reproducibility of the quantitative light-induced fluorescence (QLF) method were tested with respect to three variables: lesion area, and average and maximum changes in lesion fluorescence. To test the image-capturing stages, three analysts each captured images of 15 incipient smooth surface lesions in vivo, and the images were analysed by one of the analysts. To test the analytical stage of the method, three analysts analysed the images of 15 in vivo incipient smooth surface lesions. For the image-capturing stage, inter-examiner reliability showed an intra-class correlation coefficient (r) between 0.95 and 0.98. For the analytical stage, intra-examiner reliability for all three analysts showed a value of r between 0.93 and 0.99. Inter-examiner reliability showed a value of r between 0.95 and 0.99. It was concluded that the in vivo repeatability and reproducibility of the QLF method are excellent.