The effects of length and width of the stem on proximal humerus stress shielding in uncemented primary reverse total shoulder arthroplasty.

INTRODUCTION: To preserve humeral bone during RTSA, stems have been made shorter and cement avoided whenever possible. However, with the increased use of uncemented RTSA, a phenomenon comparable to the stress shielding of the hip has been described for the proximal humerus. The aim of this study was to investigate the influence of stem length and width on proximal humeral bone resorption after primary uncemented RTSA. MATERIALS AND METHODS: The prospective shoulder arthroplasty database of our institution was reviewed for all primary uncemented RTSAs from 2017 to 2020 in osteoarthritis and cuff tear arthropathy cases with > 2-year follow-up. We compared the clinical and the radiographic 2-year outcome of the short and standard length stems of the same prosthesis design. This allowed us to assess the effects of stem length and width with regard to stress shielding. Furthermore, we defined a cut-off value for the filling ratios to prevent stress shielding. RESULTS: Fifty patients were included in the analysis, nineteen were in the short stem group (SHORT) and thirty-one in the standard stem group (STANDARD). After 2 years, SHORT showed a relative Constant Score of 91.8% and STANDARD of 98.3% (p = 0.256). Stress shielding was found in 4 patients (21%) in SHORT and in 16 patients (52%) in STANDARD (p = 0.03); it occurred more frequently in patients with higher humeral filling ratios (p < 0.05). The calculated cut-off to prevent stress shielding was 0.7 (± 0.03) for the metaphyseal and distal filling ratio. CONCLUSION: While short and standard stems for RTSA have good results after 2 years, we found a significant negative effect of higher length and width of the stem with regard to stress shielding. Even though the clinical effects of stress shielding have to be assessed, short stems should be chosen with a filling ratio at the metaphyseal and distal position below 0.7. LEVEL OF EVIDENCE (A RETROSPECTIVE CASE-CONTROL STUDY): III.

Cemented vs. uncemented reverse total shoulder arthroplasty for the primary treatment of proximal humerus fractures in the elderly-a retrospective case-control study.

BACKGROUND: Uncemented reverse total shoulder arthroplasty (RTSA) for the primary treatment of proximal humerus fractures (PHF) in elderly patients was introduced at our institution in 2017. Recent reports have raised concerns about increased rates of early bone resorption at the proximal humerus with uncemented fracture stems. The aim of this study was to find out whether there was any difference in functional or radiographic outcomes between cemented and uncemented RTSA for PHF. METHODS: Seventeen consecutive patients who underwent uncemented RTSA (group nC) in 2017 and 2018 were age and sex matched (propensity score matching 1:2) to 34 patients with cemented RTSA implanted between 2011 and 2016 (group C) for the primary treatment of PHF. These two groups were compared in terms of clinical and radiographic outcomes at 2 years after the index surgery. RESULTS: The mean bone quality was low in both groups: in group nC the deltoid tuberosity index (DTI) was 1.43 (1.22-1.72) and in group C 1.42 (1.22-1.67). At the final 2 year follow-up, the relative CS was 98.3% (71-118) in group nC and 97.9% (36-125) in group C (p = 0.927); the absolute CS was 70.2 (49-89) in group nC and 68.0 (30-94) in group C (p = 0.509). Lucent lines at the humeral site were seen in 8 cases (47%) in group nC and in 13 cases (38%) in group C (p = 0.056). Compared to 3% in group C, all patients in group nC showed at least grade 1 and 65% showed grade 3 bone resorption at the proximal humerus (p < 0.001). CONCLUSION: Compared to cemented RTSA bone resorption at the proximal humerus was significantly more frequent in patients with uncemented RTSA for PHF. So far, this is rather a radiographic than a clinical finding, because both groups showed very satisfying functional outcomes and low revision rates at the 2 year follow-up. LEVEL OF EVIDENCE III: A retrospective case-control study.

Automated tube voltage adaptation in head and neck computed tomography between 120 and 100 kV: effects on image quality and radiation dose.

INTRODUCTION: Low tube voltage allows for computed tomography (CT) imaging with increased iodine contrast at reduced radiation dose. We sought to evaluate the image quality and potential dose reduction using a combination of attenuation based tube current modulation (TCM) and automated tube voltage adaptation (TVA) between 100 and 120 kV in CT of the head and neck. METHODS: One hundred thirty consecutive patients with indication for head and neck CT were examined with a 128-slice system capable of TCM and TVA. Reference protocol was set at 120 kV. Tube voltage was reduced to 100 kV whenever proposed by automated analysis of the localizer. An additional small scan aligned to the jaw was performed at a fixed 120 kV setting. Image quality was assessed by two radiologists on a standardized Likert-scale and measurements of signal- (SNR) and contrast-to-noise ratio (CNR). Radiation dose was assessed as CTDIvol. RESULTS: Diagnostic image quality was excellent in both groups and did not differ significantly (p = 0.34). Image noise in the 100 kV data was increased and SNR decreased (17.8/9.6) in the jugular veins and the sternocleidomastoid muscle when compared to 120 kV (SNR 24.4/10.3), but not in fatty tissue and air. However, CNR did not differ statistically significant between 100 (23.5/14.4/9.4) and 120 kV data (24.2/15.3/8.6) while radiation dose was decreased by 7-8%. CONCLUSIONS: TVA between 100 and 120 kV in combination with TCM led to a radiation dose reduction compared to TCM alone, while keeping CNR constant though maintaining diagnostic image quality.

MyCases-a portable application for radiologic case collections.

Radiologists come across interesting patient cases almost every day. This work proposes a novel case database server for quick and easy storage of such cases including whole image series, patient data, and annotations. Cases can be added to the database by saving DICOM images into a predefined directory on the local network. The application automatically extracts patient and study data from the DICOM header and saves it in the database while images are stored as anonymized JPEG files. Users can mark their cases as private or public (visible to all users). Different data fields for annotations and categorization of a case are available. The user frontend also provides several retrieval mechanisms allowing for browsing the cases and performing different kinds of search queries. The stored series can be scrolled interactively in the form of scrollable image stacks. The project is realized as a web-based application using a portable web and database server software package (XAMPP). This makes the system very lightweight and easy to run on almost any desktop computer, even from a USB flash drive, without the need for deeper IT knowledge and administrative rights.

Blunt rupture of the biceps brachii muscle - The "parachute injury" in a wake surfer - A case report.

Case: A 40-year-old man fell while wake surfing and his left arm got tangled in the rope. This caused a closed complete rupture of the M. biceps brachii. A primary muscle suture led to unrestricted function and excellent patient satisfaction after two years. Conclusions: The mentioned muscle rupture is a rare injury mainly described for paratroopers. As it has also been described for wakeboarding, this is the first description in wake surfing. Whereas in wakeboarding mainly experts are at risk during jumps, in wake surfing beginners are in danger and must be advised accordingly. Generally, the muscle suture leads to excellent function in these patients.

Iterative Metal Artifact Reduction in Head and Neck CT Facilitates Tumor Visualization of Oral and Oropharyngeal Cancer Obscured by Artifacts From Dental Hardware.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the diagnostic utility of iterative metal artifact reduction (iMAR) in computed tomography (CT)-imaging of oral and oropharyngeal cancers when obscured by dental hardware artifacts and to determine the most appropriate iMAR settings for this purpose. MATERIALS AND METHODS: The study retrospectively enrolled 27 patients (8 female, 19 male; mean age 64±12.7years) with histologically confirmed oral or oropharyngeal cancer obscured by dental artifacts in contrast-enhanced CT. Raw CT data were reconstructed with ascending iMAR strengths (levels 1/2/3/4/5) and one reconstruction without iMAR (level 0). For subjective analysis, two blinded radiologists rated tumor visualization and artifact severity on a five-point Likert scale. For objective analysis, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and artifact index (AI) were determined. RESULTS: iMAR reconstructions improved the subjective image quality of tumor edge and contrast, and the objective parameters of tumor SNR and CNR, reaching their optimum at iMAR levels 4 and 5 (P<.001). AI decreased with iMAR reconstructions reaching its minimum at iMAR level 5 (P<.001). Tumor detection rates increased 2.4-fold with iMAR 5, 2.1-fold with iMAR 4, and 1.9-fold with iMAR 3 compared to reconstructions without iMAR. Disadvantages such as algorithm-induced artifacts increased significantly with higher iMAR strengths (P<.05), reaching a maximum with iMAR 5. CONCLUSION: iMAR significantly improves CT imaging of oral and oropharyngeal cancers, as confirmed by both subjective and objective measures, with best results at highest iMAR strengths.

Quantum gravitational contributions to the cosmic microwave background anisotropy spectrum.

We derive the primordial power spectrum of density fluctuations in the framework of quantum cosmology. For this purpose we perform a Born-Oppenheimer approximation to the Wheeler-DeWitt equation for an inflationary universe with a scalar field. In this way, we first recover the scale-invariant power spectrum that is found as an approximation in the simplest inflationary models. We then obtain quantum gravitational corrections to this spectrum and discuss whether they lead to measurable signatures in the cosmic microwave background anisotropy spectrum. The nonobservation so far of such corrections translates into an upper bound on the energy scale of inflation.

Validation of optical three-dimensional plagiocephalometry by computed tomography, direct measurement, and indirect measurements using thermoplastic bands.

The aim of the study was to validate optical three-dimensional surface imaging for plagiocephalometry by comparing it with established direct and indirect plagiocephalometric measurements. From head models with symmetric and asymmetric shapes, a number of distances were determined for plagiocephalometry. Data were acquired by optical three-dimensional surface imaging, direct and indirect measurements, and computed tomography. Data acquisition was repeated 10 times with each method. In 10 patients with positional plagiocephaly, optical three-dimensional surface data were acquired, and thermoplastic strips were used to reproduce the largest circumferences of the patients' heads. All measurements were carried out by the same observer. The measurements for the head models were used to assess the reproducibility of the different measurement techniques and to check if there were statistically significant differences between them. The patient measurements were also used to determine if there were statistically significant differences between the different techniques in clinical use. None of the plagiocephalometric distances showed statistically significant differences when the 4 different methods were compared on the head models (P > 0.05). Comparison of plagiocephalometric distances obtained from optical three-dimensional imaging and from thermoplastic strips in clinical use showed also no significant difference (P > 0.05). The results of the current study reveal that optical three-dimensional imaging is a relevant alternative to other established techniques in plagiocephalometry that should be tested in larger patient series.

Cellular Aspects of Muscle Specialization Demonstrate Genotype - Phenotype Interaction Effects in Athletes.

INTRODUCTION: Gene polymorphisms are associated with athletic phenotypes relying on maximal or continued power production and affect the specialization of skeletal muscle composition with endurance or strength training of untrained subjects. We tested whether prominent polymorphisms in genes for angiotensin converting enzyme (ACE), tenascin-C (TNC), and actinin-3 (ACTN3) are associated with the differentiation of cellular hallmarks of muscle metabolism and contraction in high level athletes. METHODS: Muscle biopsies were collected from m. vastus lateralis of three distinct phenotypes; endurance athletes (n = 29), power athletes (n = 17), and untrained non-athletes (n = 63). Metabolism-, and contraction-related cellular parameters (such as capillary-to-fiber ratio, capillary length density, volume densities of mitochondria and intramyocellular lipid, fiber mean cross sectional area (MCSA) and volume densities of myofibrils) and the volume densities of sarcoplasma were analyzed by quantitative electron microscopy of the biopsies. Gene polymorphisms of ACE (I/D (insertion/deletion), rs1799752), TNC (A/T, rs2104772), and ACTN3 (C/T, rs1815739) were determined using high-resolution melting polymerase chain reaction (HRM-PCR). Genotype distribution was assessed using Chi2 tests. Genotype and phenotype effects were analyzed by univariate or multivariate analysis of variance and post hoc test of Fisher. P-values below 0.05 were considered statistically significant. RESULTS: The athletes demonstrated the specialization of metabolism- and contraction-related cellular parameters. Differences in cellular parameters could be identified for genotypes rs1799752 and rs2104772, and localized post hoc when taking the interaction with the phenotype into account. Between endurance and power athletes these concerned effects on capillary length density for rs1799752 and rs2104772, fiber type distribution and volume densities of myofibrils (rs1799752), and MSCA (rs2104772). Endurance athletes carrying the I-allele of rs1799752 demonstrated 50%-higher volume densities of mitochondria and sarcoplasma, when power athletes that carried only the D-allele showed the highest fiber MCSAs and a lower percentage of slow type muscle fibers. DISCUSSION: ACE and tenascin-C gene polymorphisms are associated with differences in cellular aspects of muscle metabolism and contraction in specifically-trained high level athletes. Quantitative differences in muscle fiber type distribution and composition, and capillarization in knee extensor muscle explain, in part, identified associations of the insertion/deletion genotypes of ACE (rs1799752) with endurance- and power-type Sports.

Contrast-enhanced T1-weighted fluid-attenuated inversion-recovery BLADE magnetic resonance imaging of the brain: an alternative to spin-echo technique for detection of brain lesions in the unsedated pediatric patient?

RATIONALE AND OBJECTIVES: We compared contrast-enhanced T1-weighted magnetic resonance (MR) imaging of the brain using different types of data acquisition techniques: periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER, BLADE) imaging versus standard k-space sampling (conventional spin-echo pulse sequence) in the unsedated pediatric patient with focus on artifact reduction, overall image quality, and lesion detectability. MATERIALS AND METHODS: Forty-eight pediatric patients (aged 3 months to 18 years) were scanned with a clinical 1.5-T whole body MR scanner. Cross-sectional contrast-enhanced T1-weighted spin-echo sequence was compared to a T1-weighted dark-fluid fluid-attenuated inversion-recovery (FLAIR) BLADE sequence for qualitative and quantitative criteria (image artifacts, image quality, lesion detectability) by two experienced radiologists. Imaging protocols were matched for imaging parameters. Reader agreement was assessed using the exact Bowker test. RESULTS: BLADE images showed significantly less pulsation and motion artifacts than the standard T1-weighted spin-echo sequence scan. BLADE images showed statistically significant lower signal-to-noise ratio but higher contrast-to-noise ratios with superior gray-white matter contrast. All lesions were demonstrated on FLAIR BLADE imaging, and one false-positive lesion was visible in spin-echo sequence images. CONCLUSION: BLADE MR imaging at 1.5 T is applicable for central nervous system imaging of the unsedated pediatric patient, reduces motion and pulsation artifacts, and minimizes the need for sedation or general anesthesia without loss of relevant diagnostic information.

Vascular mapping of head and neck: computed tomography angiography versus digital subtraction angiography.

PURPOSE: The aim of the study was to compare multislice computed tomography angiography (MSCTA) to digital subtraction angiography (DSA) for vascular mapping of the head and neck. PATIENTS AND METHODS: In 50 patients who were scheduled for microvascular reconstruction of the mandible with osteomyocutaneous flaps, MSCTA was carried out before surgery. DSA served as the method of reference. Selective common carotid angiograms were acquired in 2 projections for both sides of the neck. A 64-slice spiral computed tomography (CT) was carried out with a dual-phase protocol, using the arterial phase images for 3-dimensional CTA reconstruction. Volume rendering was used to visualize MSCTA data. RESULTS: No adverse reactions or complications occurred during or after the procedures. All CT angiograms were of diagnostic quality. No statistically significant differences between MSCTA and DSA were found for the detection of branches of the external carotid artery that are relevant host vessels for microsurgery neither in the group of 26 patients who had not had surgical treatment before (P = .687), nor in the group of 24 patients who were affected by either a tumor recurrence or an infected osteoradionecrosis (P = .508). CONCLUSION: MSCTA proved to be a reliable alternative to DSA in vascular mapping for planning of microvascular reconstruction of the mandible.

Inter- and intra-operator reliability in patient-specific template positioning for total hip arthroplasty. A cadaver study.

BACKGROUND: The implantation of the acetabular cup essentially determines the clinical outcome of total hip arthroplasty. To address this issue, the aim of this study was to build patient-specific instruments (PSIs) with various reference surfaces, followed by in vitro investigations to examine the inter- and intra-operator reliability as well as the overall precision of these patient-specific templates. METHODS: Seven human hemi-pelvis specimens were used for this study. After a CT scan, PSIs with different imprint heights were created. The overall precision of the templates and the inter- and intra-operator reliabilities were calculated. RESULTS: Strong differences in precision between the PSI designs could be observed. The desired orientation of the acetabular cup could be adjusted with a precision of up to 1.55°. CONCLUSION: Based on our results, we believe that the application of the PSI-based acetabular cup positioning in total hip arthroplasty procedures can potentially increase the precision of cup placement.

Pre-inflation from the multiverse: can it solve the quadrupole problem in the cosmic microwave background?

We analyze a quantized toy model of a universe undergoing eternal inflation using a quantum-field-theoretical formulation of the Wheeler-DeWitt equation. This so-called third quantization method leads to the picture that the eternally inflating universe is converted to a multiverse in which sub-universes are created and exhibit a distinctive phase in their evolution before reaching an asymptotic de Sitter phase. From the perspective of one of these sub-universes, we can thus analyze the pre-inflationary phase that arises naturally. Assuming that our observable universe is represented by one of those sub-universes, we calculate how this pre-inflationary phase influences the power spectrum of the cosmic microwave background (CMB) anisotropies and analyze whether it can explain the observed discrepancy of the power spectrum on large scales, i.e. the quadrupole issue in the CMB. While the answer to this question is negative in the specific model analyzed here, we point out a possible resolution of this issue.

Advanced Modeled Iterative Reconstruction (ADMIRE) Facilitates Radiation Dose Reduction in Abdominal CT.

RATIONALE AND OBJECTIVES: This study aimed to determine the potential degree of radiation dose reduction achievable using Advanced Modeled Iterative Reconstruction (ADMIRE) in abdominal computed tomography (CT) while maintaining image quality. Moreover, this study compared differences in image noise reduction of this iterative algorithm with radiation dose reduction. METHODS: Eleven consecutive patients scheduled for abdominal CT were scanned according to our institute's standard protocol (100 kV, 289 reference mAs). Using a proprietary reconstruction software, CT images of these patients were reconstructed as either full-dose weighted filtered back projections or with simulated radiation dose reductions down to 10% of the full-dose level and ADMIRE at either strength 3 or strength 5. Images were marked with arrows pointing on anatomic structures of the abdomen, differing in their contrast to the surrounding tissue. Structures were grouped into high-, medium-, and low-contrast subgroups. In addition, the intrinsic noise of these structures was measured. That followed, image pairs were presented to observers, with five readers assessing image quality using two-alternative-forced-choice comparisons. In total, 3000 comparisons were performed that way. RESULTS: Both ADMIRE 3 and 5 decreased noise of the anatomic structures significantly compared to the filtered back projection, with an additional significant difference between ADMIRE 3 and 5. Radiation dose reduction potential for ADMIRE ranged from 29.0% to 53.5%, with no significant differences between ADMIRE 3 and 5 within the contrast subgroups.The potential levels of radiation dose reduction for ADMIRE 3 differed significantly between high-, medium-, and low-contrast structures, whereas for ADMIRE 5, there was only a significant difference between the high- and the medium-contrast subgroups. CONCLUSION: Although ADMIRE 5 permits significantly higher noise reduction potential than ADMIRE 3, it does not facilitate higher levels of radiation dose reduction. ADMIRE nonetheless holds remarkable potential for radiation dose reduction, which features a certain dependency on the contrast of the structure of interest. Applying ADMIRE with a strength of 3 in abdominal CT may permit radiation dose reduction of about 30%.

What if? Exploring the multiverse through Euclidean wormholes.

We present Euclidean wormhole solutions describing possible bridges within the multiverse. The study is carried out in the framework of third quantisation. The matter content is modelled through a scalar field which supports the existence of a whole collection of universes. The instanton solutions describe Euclidean solutions that connect baby universes with asymptotically de Sitter universes. We compute the tunnelling probability of these processes. Considering the current bounds on the energy scale of inflation and assuming that all the baby universes are nucleated with the same probability, we draw some conclusions about which universes are more likely to tunnel and therefore undergo a standard inflationary era.

Design considerations for a novel shape-memory-plate osteosynthesis allowing for non-invasive alteration of bending stiffness.

Biomechanical stimuli play a major role in fracture healing. Changing the fixation stiffness through the course of healing might accelerate bone healing and prevent healing complications. Shape memory alloy (SMA) based implants were developed to allow for non-invasive stiffness alteration during the fracture healing process. To gain a deeper understanding of the implant functionality based on the alloy characteristics and geometric design, the mechanical properties of different shape memory alloys where mechanically characterized. SMA bone plates were manufactured and the structural bending stiffness of the implants was determined at different temperatures and configurations. The temperature required for complete recovery of shape after deformation increased continuously with increasing pseudo-plastic deformation in SMA probes. Full recovery was observed at temperatures ranging from 38°C to 52°C after pseudo-plastic deformations ranging from 0.2% to 1.0% outer fibre strain, respectively. The small fragment inverse-dynamisation implants revealed bending stiffnesses ranging from 0.09Nm2 to 0.34Nm2 in the initial state and from 0.16Nm2 to 0.46Nm2 after shape alteration. Dependent on the design, a relative gain of the implant stiffness ranging from 18.8% to 115.0% could be observed. The large inverse-dynamisation implants revealed bending stiffnesses from 3.7Nm2 to 7.1Nm2 before and 4.1Nm2 to 12.6Nm2 after triggering the shape memory effect. Dependent on the design a gain in stiffness from 11.8% to 117.2% was observed. Warming the SMA implant to 40°C for a short period of time, leads to a moderate increase in implant stiffness of up to 64.5%, while triggering the implant with 50°C leads to a maximum increase in stiffness of up to 127.3%. The Nitinol shape memory bone plates have a huge potential for improving the treatment of long shaft fractures by allowing for the increase, decrease or incremental change of implant stiffness in fracture stabilization. However, the interaction between design, material properties, and manufacturing processes need to be carefully considered for each specific application to achieve optimum function of SMA-based, stiffness altering, fracture-fixation implants.

Nasolabial symmetry following Tennison-Randall lip repair: a three-dimensional approach in 10-year-old patients with unilateral clefts of lip, alveolus and palate.

AIM: To assess the degree of facial symmetry in patients suffering from unilateral cleft lip, alveolus and palate (UCLAP) by determining differences between the cleft and the non-cleft hemifaces from 3D surface data. PATIENTS AND METHODS: In twenty-two 10-year-old UCLAP patients, who had the lip repaired using the Tennison-Randall technique and did not undergo further revisional surgery, differences were determined between landmarks, surface areas of the upper lip vermilion and nostrils and virtual volumes of midface, nose and upper lip for cleft and non-cleft sides, separately, after having established a plane of symmetry calculated from optical 3D facial surface data. RESULTS: Statistically significant differences could be found between cleft and non-cleft sides for the nasal landmarks G(lat), G(sup) and La(med), the nostril angle and the virtual volume of the nose (p(Glat)=0.011, p(Gsup)<0.0005, p(Lamed)=0.002, p(nostril angle)=0.036 and p(nose volume)<0.0005, resp.). CONCLUSION: Analysis of 3D data shows that complete nasal symmetry is difficult to achieve with Tennison-Randall's lip repair without revisional surgery. Further trials on larger populations of patients will allow a more comprehensive and consistent analysis of the consequence of different methods for cp repair in order to identify the techniques with the best outcome in terms of facial symmetry.

Implant impingement during internal rotation after reverse shoulder arthroplasty. The effect of implant configuration and scapula anatomy: A biomechanical study.

BACKGROUND: Internal rotation after reverse shoulder arthroplasty is essential to perform fundamental daily living activities. The purpose of this study was to examine the impact of anatomical and implant related factors on impingement-free internal rotation of the glenohumeral joint. METHODS: CT-scans of 13 human shoulder specimens with implanted reverse shoulder prostheses were carried out and scapula neck length, lateral pillar angle, and implantation height of the metaglene were measured. Internal rotation testing of all specimens was performed by the use of a robot assisted shoulder simulator. Biomechanical variables were analyzed using a three-way ANOVA. Spearman's rank correlations were performed to determine the relationship between biomechanical and anatomical data. FINDINGS: The maximum internal rotation angle for a 38 mm centric glenosphere and a standard onlay was 93.4(SD 34.9°). The change of the diameter of the glenosphere resulted in no significant increase of the maximum rotation angle (P=0.16), while change of the glenosphere type from concentric to eccentric (P=0.005) as well as the change of the onlay type from standard to a more shallow one (P=0.002) both had a significant effect on the internal rotation. The distance between the inferior rim of the metaglene and the inferior aspect of the glenoid (P=0.21), scapula pillar angle (P=0.13) as well as the scapula neck length (P=0.81) showed no significant correlation with the maximum internal rotation angle. INTERPRETATION: Implant component selection shows strong influence on the impingement-free internal rotation. The use of an eccentric glenosphere and a shallow humeral cup may improve internal rotation after reverse shoulder arthroplasty.

Corrosion behavior, biocompatibility and biomechanical stability of a prototype magnesium-based biodegradable intramedullary nailing system.

Implants made of degradable magnesium alloys are a potential alternative to conventional orthopaedic implant materials, e.g. stainless steel or titanium. Intramedullary nails made of the magnesium alloy LAE442 were subjected to cyclic fatigue tests in both distilled water and Hank's Balanced Salt Solution (HBSS) at 37.5°C until implant failure or a limit of 500,000cycles was reached. In distilled water, four of the five nails were still intact after the end of the biomechanical test. In HBSS, a breakage within the first 70,000 bending cycles was observed. Additionally, the degradation rate of this alloy was determined in HBSS according to the weight loss method (0.24±0.12mmyear(-1)) and based on gas release (0.21±0.03mmyear(-1)) with a standard eudiometer. A cytotoxicity test with L929 cells was carried out in accordance with EN ISO 10993-5/12. This test demonstrated sufficient cell viability of the diluted extracts (50%, 25% and 12.5%). The relative metabolic activity of the 100% extract was reduced slightly below 70%, which is classified as a threshold value for cytotoxicity. In conclusion, this in vitro study indicates that intramedullary nails made of LAE442 may not have the required fatigue resistance for load-bearing applications and the development of a corrosion-protective coating may be necessary to prevent early failure of the implant.

Dose reduction potential of iterative reconstruction algorithms in neck CTA-a simulation study.

OBJECTIVES: This study aimed to determine the degree of radiation dose reduction in neck CT angiography (CTA) achievable with Sinogram-affirmed iterative reconstruction (SAFIRE) algorithms. METHODS: 10 consecutive patients scheduled for neck CTA were included in this study. CTA images of the external carotid arteries either were reconstructed with filtered back projection (FBP) at full radiation dose level or underwent simulated dose reduction by proprietary reconstruction software. The dose-reduced images were reconstructed using either SAFIRE 3 or SAFIRE 5 and compared with full-dose FBP images in terms of vessel definition. 5 observers performed a total of 3000 pairwise comparisons. RESULTS: SAFIRE allowed substantial radiation dose reductions in neck CTA while maintaining vessel definition. The possible levels of radiation dose reduction ranged from approximately 34 to approximately 90% and depended on the SAFIRE algorithm strength and the size of the vessel of interest. In general, larger vessels permitted higher degrees of radiation dose reduction, especially with higher SAFIRE strength levels. With small vessels, the superiority of SAFIRE 5 over SAFIRE 3 was lost. CONCLUSIONS: Neck CTA can be performed with substantially less radiation dose when SAFIRE is applied. The exact degree of radiation dose reduction should be adapted to the clinical question, in particular to the smallest vessel needing excellent definition.