Breakage of intramedullary femoral nailing or femoral plating: how to prevent implant failure

Introduction: Intramedullary (IM) fixation is the dominant treatment for pertrochanteric and femoral shaft fractures. In comparison to plate osteosynthesis (PO), IM fixation offers greater biomechanical stability and reduced non-union rates. Due to the minimally invasive nature, IM fixations are less prone to approach-associated complications, such as soft-tissue damage, bleeding or postoperative infection, but they are more prone to fat embolism. A rare but serious complication, however, is implant failure. Thus, the aim of this study was to identify possible risk factors for intramedullary fixation (IMF) and plate osteosynthesis (PO) failure. Materials: and methods We searched our trauma surgery database for implant failure, intramedullary and plate osteosynthesis, after proximal-pertrochanteric, subtrochanteric-or femoral shaft fractures between 2011 and 2019. Implant failures in both the IMF and PO groups were included. Demographic data, fracture type, quality of reduction, duration between initial implantation and nail or plate failure, the use of cerclages, intraoperative microbiological samples, sonication, and, if available, histology were collected. Results: A total of 24 femoral implant failures were identified: 11 IMFs and 13 POs. The average age of patients in the IM group was 68.2 +/- 13.5 years and in the PO group was 65.6 +/- 15.0 years, with men being affected in 63.6% and 39.5% of cases, respectively. A proximal femoral nail (PFN) anti-rotation was used in 7 patients, a PFN in one and a gamma nail in two patients. A total of 6 patients required cerclage wires for additional stability. A combined plate and intramedullary fixation was chosen in one patient. Initially, all intramedullary nails were statically locked. Failures were observed 34.1 weeks after the initial surgery on average. Risk factors for implant failure included the application of cerclage wires at the level of the fracture (n = 5, 21%), infection (n = 2, 8%), and the use of an additional sliding screw alongside the femoral neck screw (n = 3, 13%). In all patients, non-union was diagnosed radiographically and clinically after 6 months (n = 24, 100%). In the event of PO failure, the placement of screws within all screw holes, and interprosthetic fixation were recognised as the major causes of failure. Conclusion: Intramedullary or plate osteosynthesis remain safe and reliable procedures in the treatment of proximal femoral fractures (pertrochanteric, subtrochanteric and femoral shaft fractures). Nevertheless, the surgeon needs to be aware of several implant-related limitations causing implant breakage. These may include the application of tension band wiring which can lead to a too rigid fixation, or placement of cerclage wires at the fracture site

Error estimation in multitemporal InSAR deformation time series, with application to Lanzarote, Canary Islands

Interferometric Synthetic Aperture Radar (InSAR) is a reliable technique for measuring crustal deformation. However, despite its long application in geophysical problems, its error estimation has been largely overlooked. Currently, the largest problem with InSAR is still the atmospheric propagation errors, which is why multitemporal interferometric techniques have been successfully developed using a series of interferograms. However, none of the standard multitemporal interferometric techniques, namely PS or SB (Persistent Scatterers and Small Baselines, respectively) provide an estimate of their precision. Here, we present a method to compute reliable estimates of the precision of the deformation time series. We implement it for the SB multitemporal interferometric technique (a favorable technique for natural terrains, the most usual target of geophysical applications). We describe the method that uses a properly weighted scheme that allows us to compute estimates for all interferogram pixels, enhanced by a Montecarlo resampling technique that properly propagates the interferogram errors (variance-covariances) into the unknown parameters (estimated errors for the displacements). We apply the multitemporal error estimation method to Lanzarote Island (Canary Islands), where no active magmatic activity has been reported in the last decades. We detect deformation around Timanfaya volcano (lengthening of line-of-sight ∼ subsidence), where the last eruption in 1730–1736 occurred. Deformation closely follows the surface temperature anomalies indicating that magma crystallization (cooling and contraction) of the 300-year shallow magmatic body under Timanfaya volcano is still ongoing.Peer reviewe

Stimulating a Canadian narrative for climate

ABSTRACT: This perspective documents current thinking around climate actions in Canada by synthesizing scholarly proposals made by Sustainable Canada Dialogues (SCD), an informal network of scholars from all 10 provinces, and by reviewing responses from civil society representatives to the scholars' proposals. Motivated by Canada's recent history of repeatedly missing its emissions reduction targets and failing to produce a coherent plan to address climate change, SCD mobilized more than 60 scholars to identify possible pathways towards a low-carbon economy and sustainable society and invited civil society to comment on the proposed solutions. This perspective illustrates a range of Canadian ideas coming from many sectors of society and a wealth of existing inspiring initiatives. Solutions discussed include climate change governance, low-carbon transition, energy production, and consumption. This process of knowledge synthesis/creation is novel and important because it provides a working model for making connections across academic fields as well as between academia and civil society. The process produces a holistic set of insights and recommendations for climate change actions and a unique model of engagement. The different voices reported here enrich the scope of possible solutions, showing that Canada is brimming with ideas, possibilities, and the will to act

Current concept of abdominal sepsis : WSES position paper

Peer reviewe

Surviving Sepsis Campaign: international guidelines for management of severe sepsis and septic shock, 2012

OBJECTIVE: To provide an update to the "Surviving Sepsis Campaign Guidelines for Management of Severe Sepsis and Septic Shock," last published in 2008. DESIGN: A consensus committee of 68 international experts representing 30 international organizations was convened. Nominal groups were assembled at key international meetings (for those committee members attending the conference). A formal conflict of interest policy was developed at the onset of the process and enforced throughout. The entire guidelines process was conducted independent of any industry funding. A stand-alone meeting was held for all subgroup heads, co- and vice-chairs, and selected individuals. Teleconferences and electronic-based discussion among subgroups and among the entire committee served as an integral part of the development. METHODS: The authors were advised to follow the principles of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to guide assessment of quality of evidence from high (A) to very low (D) and to determine the strength of recommendations as strong (1) or weak (2). The potential drawbacks of making strong recommendations in the presence of low-quality evidence were emphasized. Recommendations were classified into three groups: (1) those directly targeting severe sepsis; (2) those targeting general care of the critically ill patient and considered high priority in severe sepsis; and (3) pediatric considerations. RESULTS: Key recommendations and suggestions, listed by category, include: early quantitative resuscitation of the septic patient during the first 6 h after recognition (1C); blood cultures before antibiotic therapy (1C); imaging studies performed promptly to confirm a potential source of infection (UG); administration of broad-spectrum antimicrobials therapy within 1 h of the recognition of septic shock (1B) and severe sepsis without septic shock (1C) as the goal of therapy; reassessment of antimicrobial therapy daily for de-escalation, when appropriate (1B); infection source control with attention to the balance of risks and benefits of the chosen method within 12 h of diagnosis (1C); initial fluid resuscitation with crystalloid (1B) and consideration of the addition of albumin in patients who continue to require substantial amounts of crystalloid to maintain adequate mean arterial pressure (2C) and the avoidance of hetastarch formulations (1B); initial fluid challenge in patients with sepsis-induced tissue hypoperfusion and suspicion of hypovolemia to achieve a minimum of 30 mL/kg of crystalloids (more rapid administration and greater amounts of fluid may be needed in some patients (1C); fluid challenge technique continued as long as hemodynamic improvement is based on either dynamic or static variables (UG); norepinephrine as the first-choice vasopressor to maintain mean arterial pressure ≥65 mmHg (1B); epinephrine when an additional agent is needed to maintain adequate blood pressure (2B); vasopressin (0.03 U/min) can be added to norepinephrine to either raise mean arterial pressure to target or to decrease norepinephrine dose but should not be used as the initial vasopressor (UG); dopamine is not recommended except in highly selected circumstances (2C); dobutamine infusion administered or added to vasopressor in the presence of (a) myocardial dysfunction as suggested by elevated cardiac filling pressures and low cardiac output, or (b) ongoing signs of hypoperfusion despite achieving adequate intravascular volume and adequate mean arterial pressure (1C); avoiding use of intravenous hydrocortisone in adult septic shock patients if adequate fluid resuscitation and vasopressor therapy are able to restore hemodynamic stability (2C); hemoglobin target of 7-9 g/dL in the absence of tissue hypoperfusion, ischemic coronary artery disease, or acute hemorrhage (1B); low tidal volume (1A) and limitation of inspiratory plateau pressure (1B) for acute respiratory distress syndrome (ARDS); application of at least a minimal amount of positive end-expiratory pressure (PEEP) in ARDS (1B); higher rather than lower level of PEEP for patients with sepsis-induced moderate or severe ARDS (2C); recruitment maneuvers in sepsis patients with severe refractory hypoxemia due to ARDS (2C); prone positioning in sepsis-induced ARDS patients with a PaO (2)/FiO (2) ratio of ≤100 mm Hg in facilities that have experience with such practices (2C); head-of-bed elevation in mechanically ventilated patients unless contraindicated (1B); a conservative fluid strategy for patients with established ARDS who do not have evidence of tissue hypoperfusion (1C); protocols for weaning and sedation (1A); minimizing use of either intermittent bolus sedation or continuous infusion sedation targeting specific titration endpoints (1B); avoidance of neuromuscular blockers if possible in the septic patient without ARDS (1C); a short course of neuromuscular blocker (no longer than 48 h) for patients with early ARDS and a PaO (2)/FI O (2) 180 mg/dL, targeting an upper blood glucose ≤180 mg/dL (1A); equivalency of continuous veno-venous hemofiltration or intermittent hemodialysis (2B); prophylaxis for deep vein thrombosis (1B); use of stress ulcer prophylaxis to prevent upper gastrointestinal bleeding in patients with bleeding risk factors (1B); oral or enteral (if necessary) feedings, as tolerated, rather than either complete fasting or provision of only intravenous glucose within the first 48 h after a diagnosis of severe sepsis/septic shock (2C); and addressing goals of care, including treatment plans and end-of-life planning (as appropriate) (1B), as early as feasible, but within 72 h of intensive care unit admission (2C). Recommendations specific to pediatric severe sepsis include: therapy with face mask oxygen, high flow nasal cannula oxygen, or nasopharyngeal continuous PEEP in the presence of respiratory distress and hypoxemia (2C), use of physical examination therapeutic endpoints such as capillary refill (2C); for septic shock associated with hypovolemia, the use of crystalloids or albumin to deliver a bolus of 20 mL/kg of crystalloids (or albumin equivalent) over 5-10 min (2C); more common use of inotropes and vasodilators for low cardiac output septic shock associated with elevated systemic vascular resistance (2C); and use of hydrocortisone only in children with suspected or proven "absolute"' adrenal insufficiency (2C). CONCLUSIONS: Strong agreement existed among a large cohort of international experts regarding many level 1 recommendations for the best care of patients with severe sepsis. Although a significant number of aspects of care have relatively weak support, evidence-based recommendations regarding the acute management of sepsis and septic shock are the foundation of improved outcomes for this important group of critically ill patients

Mechanotherapie der Knochenfraktur: Angepasste Fixationsbedingungen

While mechanical overloading caused a fracture, well-controlled mechanical loading can be an integral part of a coordinated fracture healing process. The relative movement of fracture segments affects tissue strain close to the fracture and thus controls the healing pathway. More specifically, moderate hydrostatic or volumetric strain improves osteogenic development while high distortional or deviatoric strain impairs the healing process. Strain is often not directly accessible, but fortunately in-fracture-plane and out-of-fracture-plane interfragmentary movement relative to gap volume correlate to the harmful and beneficial strain respectively. The locking plate configuration, i.e. specifically the screw location and screw type, and most importantly plate working length (bridge span) determine the interfragmentary movement as long as bony contact bridging can be neglected. With a plate-bone clearance and for large or comminuted gaps, the total amount of interfragmentary movement can be controlled. However, the components of in-plate and out-of-plane movement are coupled: Large transverse defects cannot be fixated with locking plates alone because a large plate working length leads to high shear compared to axial interfragmentary movement. Furthermore, the relative amount of shear strain to normal strain is determined by fracture configuration (gap size, comminution, slope as well as orientation of fracture lines). Small gaps up to 3mm can be fixated with locking plates reliably, but also for such small gaps, the optimal mechano-biology can only be achieved for certain orientations of the fracture lines (proximal lateral anterior to distal medial posterior). Fracture lines running proximal medial posterior to distal lateral anterior might need more adapted fixation. Furthermore, as soon as bony support occurs, e.g. with bone fragment to bone fragment contact under load or bridging with a graft or scaffold or bridging of the stiffening healing tissue, the importance of fixation stiffness diminishes dramatically. Analyzing individual case settings could allow for pre- or intra-operative planning for a certain fracture gap size and fracture line to find an individual fixation setting, which might be derived computationally. Finite element modeling of individual cases is possible, but the degree of process automation and the need for interpretation are currently barriers for a clinical use. A faster and easier tool for surgeon users is needed. The control of total interfragmentary movement can be achieved with screw positioning: Adjusting plate working length leads to increased axial interfragmentary movement, but even more increased shear in the presence of a gap. If stimulation within the desired range cannot be achieved, there are further options such as dynamic locking screws or active plates with sliding elements. If secondary fracture healing still cannot be expected before implant failure, bony contact support under load should be considered, which is also possible with a graft or scaffold. For small gaps, reduction using a lag screw and fixation with a neutralization locking plate are currently covered topics. For large gaps, double plating and additional scaffolding are currently under investigation. There should be sufficient options to treat most fractures already, but the selection procedure depends on the estimation of implant fatigue strength versus fracture healing speed. Additional opportunities for an acceleration of fracture healing with further reduction of shear have been identified.Während mechanische Überlastung zu einer Fraktur führt, kann eine kontrollierte mechanische Belastung ein integraler Bestandteil eines koordinierten Frakturheilungsprozesses sein. Die Relativbewegung der Fraktursegmente beeinflusst die Gewebeverformung nahe der Fraktur und steuert somit den Heilungsprozess. Insbesondere verbessert eine moderate hydrostatische oder volumetrische Verformung die osteogene Entwicklung, während eine hohe verzerrende Verformung die Heilung verlangsamt. Die Gewebeverformung ist oft nicht direkt erfassbar, aber glücklicherweise entsprechen die interfragmentären Bewegungen tangential zur Bruchebene und normal der Bruchebene relativ zum Spaltvolumen der schädlichen bzw. vorteilhaften Verformungsstimulation. Die Konfiguration winkelstabiler Verriegelungsplatten, d. h. insbesondere die Schraubenposition und der Schraubentyp, und vor allem die Plattenschwingstrecke (Überbrückungsspanne oder freie Biegelänge) bestimmen die interfragmentäre Bewegung, solange die knöcherne Kontaktüberbrückung vernachlässigt werden kann. Mit einem Platten-Knochen-Abstand und bei großem Frakturspalt oder Trümmerbruch kann der Betrag der interfragmentären Bewegung gesteuert werden. Die Komponenten der Bewegung tangential und normal der Frakturebene sind jedoch gekoppelt: Große transverse Defekte können nicht allein mit winkelstabilen Platten fixiert werden, da eine große Arbeitslänge der Platte im Vergleich zu einer axialen interfragmentären Bewegung zu einer hohen Scherung führt. Darüber hinaus wird der relative Betrag der Scherung zur normalen Dehnung durch die Bruchkonfiguration (Spaltgröße, Spaltanzahl bei Trümmerfrakturen, Steigung sowie Orientierung der Bruchlinien) bestimmt. Kleine Spalte von bis zu 3 mm können mit winkelstabilen Verriegelungsplatten zuverlässig fixiert werden, aber auch für solche kleinen Spalte kann die optimale Mechanobiologie nur für bestimmte Orientierungen der Frakturlinien (proximal lateral anterior nach distal medial posterior) erreicht werden. Frakturlinien, die proximal medial posterior nach distal lateral anterior verlaufen, müssen möglicherweise angepasst versorgt werden. Sobald eine knöcherne Abstützung auftritt, also wenn ein Knochenfragment mit dem anderen Knochenfragment unter Belastung Kontakt aufnimmt, oder die Segmente durch Überbrückung mit einem Transplantat oder Gerüst (Scaffold) oder durch versteiftes neues Gewebes verbunden ist, nimmt der Einfluss der Fixationssteifigkeit auf den weiteren Heilungsverlauf dramatisch ab. Durch Analyse individueller Fallparameter könnte eine prä- oder intraoperative Planung für eine bestimmte Frakturspaltgröße und Frakturlinie vorgenommen werden, um eine spezifische Fixation zu finden, die rechnerisch abgeleitet werden kann. Die Finite-Elemente-Modellierung von Einzelfällen ist möglich, aber der Grad der Prozessautomatisierung und der Interpretationsbedarf sind derzeit Hindernisse für eine klinische Anwendung. Ein schnelleres und einfacheres Werkzeug für Chirurgen als direkte Nutzer ist erforderlich. Die Steuerung des Betrags der interfragmentären Bewegung kann durch Schraubenpositionierung erreicht werden: Durch das Einstellen der Arbeitslänge der Platte wird die axiale interfragmentäre Bewegung erhöht, die Scherkraft jedoch noch stärker erhöht, solange ein Spalt vorhanden bleibt. Wenn die Verformungsstimulation den gewünschten Bereich nicht erreicht, gibt es weitere Optionen wie dynamische Verriegelungsschrauben oder „aktive“ Platten mit Gleitelementen. Wenn vor dem erwarteten Implantatversagen keine sekundäre Frakturheilung zu erwarten ist, sollte eine knöcherne Abstützung unter Last in Betracht gezogen werden, die auch mit einem Transplantat oder Gerüst möglich ist. Bei kleinem Spalt werden derzeit die Reduktion mit einer Zugschraube und die Fixierung mit einer Neutralisationsplatte diskutiert. Bei großem Spalt werden derzeit Doppelplattenfixationen und zusätzliche Scaffolds untersucht. Es sollten bereits ausreichend Optionen vorhanden sein, um die meisten Frakturen zu behandeln. Das Auswahlverfahren hängt jedoch von der Einschätzung der Implantatermüdung im Verhältnis zur Heilungsgeschwindigkeit der Frakturen ab. Zusätzliche Möglichkeiten für eine Beschleunigung der Frakturheilung mit weiterer Verringerung der Scherung wurden identifiziert

Anatomic grooved stem mitigates strain shielding compared to established total hip arthroplasty stem designs in finite-element models

Abstract Aseptic loosening remains a major problem for uncemented femoral components in primary total hip arthroplasty (THA). Ideally, bone adaptation after THA manifests minimally and local bone density reduction is widely avoided. Different design features may help to approximate initial, post-THA bone strain to levels pre-THA. Strain-shielding effects of different SP-CL stem design features are systematically analyzed and compared to CLS Spotorno and CORAIL using finite element models and physiological musculoskeletal loading conditions. All designs show substantial proximal strain-shielding: 50% reduced medial surface strain, 40–50% reduction at lateral surface, >120 µm/m root mean square error (RMSE) compared to intact bone in Gruen zone 1 and >60 µm/m RMSE in Gruen zones 2, 6, and 7. Geometrical changes (ribs, grooves, cross sections, stem length, anatomic curvature) have a considerable effect on strain-shielding; up to 20%. Combinations of reduced stem stiffness with larger proximal contact area (anatomically curved, grooves) lead to less strain-shielding compared to clinically established implant designs. We found that only the combination of a structurally flexible stem with anatomical curvature and grooves improves strain-shielding compared to other designs. The clinical implications in vivo of this initial strain-shielding difference are currently under evaluation in an ongoing clinical analysis