Estabilización de fracturas Schatzker I de la meseta tibial. Estudio numérico comparativo mediante elementos finitos. Placas bloqueadas vs tornillos canulados

ResumenObjetivoLa estabilización quirúrgica de las fracturas SchatzkerI de meseta tibial se realiza principalmente mediante la colocación de tornillos canulados o mediante la aplicación de una placa con tornillos bloqueados proximales. En el postoperatorio, los pacientes realizan generalmente una descarga de 6 u 8 semanas. Usando el método de elementos finitos (EF), este estudio intenta analizar si la carga inmediata del paciente después de la cirugía genera un exceso de desplazamiento interfragmentario (DI).MétodosUtilizando un modelo validado de EF de paciente sano, el modelo tibial se reprodujo geométricamente, y se realizó una fractura SchatzkerI tipo a partir de radiografías y TAC de diferentes pacientes. Se modelizaron tornillos canulados de 6,5mm y una placa Polyax (Biomet Inc, EE.UU.), implantándose virtualmente en la tibia fracturada, y aplicando una fuerza de 400N, equivalente a 80kg de peso del paciente en bipedestación. Los DI se calcularon a partir del desplazamientos de diferentes nodos en el área fractuaria.ResultadosLos DI máximos calculados con la placa Polyax y los tornillos canulados fueron de 0,1-0,15mm y 0,25-0,3mm, respectivamente. Sin embargo, aplicando un peso de un 20% existía riesgo de fractura por compresión con los tornillos canulados. Con la placa Polyax se obtuvo una mejor distribución de las cargas, manteniéndose en zona segura por debajo de 100Mpa con la aplicación del 50% del peso del paciente.ConclusiónEste estudio sugiere que ambos sistemas tienen un resultado similar en cuanto al DI, pero la placa realiza una mejor distribución de las cargas en la zona de la fractura, permitiendo la carga parcial inmediata de un 50% del peso del paciente.AbstractObjectiveSurgical stabilization of split fractures of the lateral tibial plateau may involve percutaneous insertion of cannulated screws or more invasive implantation of locked plating systems. In any case, six to eight weeks of non-weight-bearing are recommended. By using the finite element (FE) method, this study aimed to assess whether immediate weight bearing can generate excessive interfragmentary motions (IM).MethodsA validated femur-tibia FE model of a healthy patient was used. The tibia model was reconverted into geometry, and a SchatzkerI fracture was re-created based on patient x-rays. Cannulated 6.5mm cancellous bone screws, and a Polyax tibial locked plating system (Biomet Inc, USA) were modelled, and virtually implanted into the fractured tibia geometry. An axial force of 400N pressed the femur model against the tibial plateau, simulating the weight of an 80Kg patient in bipedal stance. IM were calculated as the displacements between two nodes initially superimposed in the fracture areaResultsMaximum IM calculated with the Polyax and with the cannulated screw fixations were around 0.1-0.15mm, and 0.25-0.3mm, respectively. Both systems led to similar IM up to 80-90% of applied body weight. However, applying over 20% of the simulated body weight might lead to a risk of compression bone fracture. With the Polyax system, bone stresses were better distributed, and remained below 100MPa at 30% of body weight. Maximum stresses in the implants were about half the reported strength for the alloy simulated.ConclusionThis study suggested that IM caused by weight bearing might not impede bone healing in a fracture stabilized with either a Polyax locked plating system or cannulated screws. However, cannulated screw systems could lead to harmful load concentrations in the bone with immediate weight bearing. Plate systems will allow around 50% of immediate weight bearing

Investigación de la biomecánica y mecanobiología de las fracturas de la meseta tibial mediante un modelo de elementos finitos

Las fracturas de la meseta tibial afectan a una gran articulación de carga como es la rodilla y son lesiones graves que conducen frecuentemente a anomalías funcionales. Para preservar la función normal de la rodilla, se debe mantener la congruencia articular, conservar el eje mecánico normal, asegurar la estabilidad de la fractura y recuperar el rango de movilidad completo. Alcanzar estos objetivos presenta dificultades por la importante afectación de tejidos blandos, los distintos tipos de calidad ósea y, en ocasiones, la presencia de comorbilidades de los pacientes. El mecanismo de lesión principal que da lugar a las fracturas de la meseta tibial es una tensión en varo o valgo con una carga axial asociada. La meseta lateral resulta afectada en el 55%-70% de los casos, mientras que la medial se ve afectada en el 10%-30%. Todavía no existe una práctica totalmente estandarizada en las fracturas de la meseta tibial debido a la falta de estudios biomecánicos concluyentes, y coexisten diferentes técnicas usadas para el tratamiento de estas fracturas. Tener un mejor conocimiento biomecánico de las fracturas de la meseta tibial y comparar los tratamientos más utilizados ha sido uno de los objetivos principales de esta investigación para intentar dar respuesta a la pregunta de cuál es el mejor método para tratarlas. La base de esta investigación ha sido el uso del método de elementos finitos (EF) para el estudio de las fracturas de meseta tibial y sus tratamientos. Este método consiste en subdividir geometrías complejas en un ensamblado discreto de elementos de geometría sencilla en los que los desplazamientos relativos de puntos pueden ser fácilmente calculados en función de las cargas que se ejercen sobre el elemento. Según la dimensión del problema, estos elementos podrán ser líneas (1D), triángulos o cuadrados (2D), o tetraedros o hexaedros (3D). Los desplazamientos relativos de puntos calculados dentro de los elementos están asociados a valores de tensiones vía la introducción de ecuaciones de comportamiento para el material del elemento virtualmente constituido. El objetivo del primer trabajo (Fixation of a split fracture of the lateral tibial plateau with a locking screw plate instead of cannulated screws would allow early weight bearing: a computational exploration) fue evaluar con cálculos de EF si la carga inmediata de peso sería posible tras la estabilización quirúrgica, ya sea con tornillos canulados o con una placa bloqueada en una fractura de la meseta tibial lateral. El segundo trabajo (An intact fibula may contribute to allow early weight-bearing in surgically treated tibial plateau fractures) intenta dar respuesta a la estabilidad que el peroné proximal aporta en las fracturas de la meseta tibial lateral. Se realizó un modelo de geometría tridimensional mediante elementos finitos a partir de la base de datos VAKHUM (http://www.ulb.ac.be/project/vakhum) y se creó una reconstrucción del modelo a partir de las imágenes de tomografía computarizada. Posteriormente se simuló una fractura tipo de meseta tibial lateral usando datos geométricos a partir de imágenes radiológicas y de TC. Se simularon los sistemas de tratamiento, con y sin peroné, la placa bloqueada Polyax® (Biomet Inc, IN, USA) y un set de tornillos canulados de 6,5 mm (Biomet Inc, IN, USA). Las fracturas de la meseta tibial lateral, fijadas ya sea con placa bloqueadas o con tornillos canulados, no mostraron movimientos interfragmentarios clínicamente relevantes en un modelo de EF. La fijación de la fractura con una placa bloqueada mostró una mayor estabilidad mecánica que la fijación con tornillos canulados. La placa bloqueada podría también permitir una capacidad de carga completa o al menos parcial bajo postura estática. Este modelo de EF mostró que un peroné intacto podría contribuir a la estabilidad mecánica de las fracturas de la meseta tibial lateral, y combinado con placa, la integridad mecánica que aporta el peroné puede permitir una capacidad de carga temprana y sin movimientos interfragmentarios significativos.Tibial plateau fractures affect to the knee joint and they are injuries that often cause functional impairment. To preserve the normal function of the knee, articular congruence must be achieved, stable fixation must be obtained as well as physiological knee aligment in order to recover full range of motion. This goals are often difficult to be achieved due to the soft tissue damage, bone quality and patient comorbidities. The most frecuent injury mechanism is an axial load of the knee combined with and excessive valgus or varus force. Lateral plateau is affected on 55%-70% of the cases and medial plateau on 10%-30%. There is not yet a totally standardized technique to approach all tibial plateau fractures due to the little number of biomechanic studies, therefore there are diferent techniques to treat the same fractures. The aim of this study was to have a better biomechanic understanding of tibial plateau fractures and to compare the most common treatments to asses what is the best way to treat these injuries. This investigation was conducted using finite elements (FE). FE method consists on subdividing complex geometries in a less complex geometry element assemblement. Therefore relative movements in the geometry can be easily measured and accurate calculations can be obtained. Depending on the dimension of the geometry studied the elements can be linear (1D), triangles or squares (2D)or tetrahedrons or hexahedrons (3D). Relative displacements of calculated points inside the elements are associated to tension values with behavioral equations for virtually simulated material and geometry. The purpose of the first study (Fixation of a split fracture of the lateral tibial plateau with a locking screw plate instead of cannulated screws would allow early weight bearing: a computational exploration) was to assess, with finite element (FE) calculations, whether immediate weight bearing would be possible after surgical stabilization either with cannulated screws or with a locking plate in a split fracture of the lateral tibial plateau (LTP). The purpose of the second study ( An intact fibula may contribute to allow early weight-bearing in surgically treated tibial plateau fractures ) was to assess differences in interfragmentary movement (IFM) in a split fracture of lateral tibial plateau, with and without intact fibula. It was hypothesized that an intact fibula could positively contribute to the mechanical stabilization of surgically reduced lateral tibial plateau fractures. A split fracture of the LTP was recreated in a FE model of a human tibia. A three-dimensional FE model geometry of a human femur-tibia system was obtained from the VAKHUM project database, and was built from CT images from a subject with normal bone morphologies and normal alignment. The mesh of the tibia was reconverted into a geometry of NURBS surfaces. A split fracture of the lateral tibial plateau was reproduced by using geometrical data from patient radiographs. A locking screw plate (LP) and a cannulated screw (CS) systems were modelled to virtually reduce the fracture and 80 kg static body-weight was simulated with and without fibula. While the simulated body-weight led to clinically acceptable interfragmentary motion, possible traumatic bone shear stresses were predicted nearby the cannulated screws. With a maximum estimation of about 1.7 MPa maximum bone shear stresses, the Polyax system might ensure more reasonable safety margins. Split fractures of the LTP fixed either with locking screw plate or cannulated screws showed no clinically relevant IFM in a FE model. The locking screw plate showed higher mechanical stability than cannulated screw fixation. The locking screw plate might also allow full or at least partial weight bearing under static posture at time zero. This FE model showed that an intact fibula contributes to the mechanical stability of the lateral tibial plateau. In combination with a locking plate fixation, early weight bearing may be allowed without significant IFM, contributing to an early clinical and functional recovery of the patient

Investigación de la biomecánica y mecanobiología de las fracturas de la meseta tibial mediante un modelo de elementos finitos

Premi Extraordinari de Doctorat concedit pels programes de doctorat de la UAB per curs acadèmic 2016-2017Las fracturas de la meseta tibial afectan a una gran articulación de carga como es la rodilla y son lesiones graves que conducen frecuentemente a anomalías funcionales. Para preservar la función normal de la rodilla, se debe mantener la congruencia articular, conservar el eje mecánico normal, asegurar la estabilidad de la fractura y recuperar el rango de movilidad completo. Alcanzar estos objetivos presenta dificultades por la importante afectación de tejidos blandos, los distintos tipos de calidad ósea y, en ocasiones, la presencia de comorbilidades de los pacientes. El mecanismo de lesión principal que da lugar a las fracturas de la meseta tibial es una tensión en varo o valgo con una carga axial asociada. La meseta lateral resulta afectada en el 55%-70% de los casos, mientras que la medial se ve afectada en el 10%-30%. Todavía no existe una práctica totalmente estandarizada en las fracturas de la meseta tibial debido a la falta de estudios biomecánicos concluyentes, y coexisten diferentes técnicas usadas para el tratamiento de estas fracturas. Tener un mejor conocimiento biomecánico de las fracturas de la meseta tibial y comparar los tratamientos más utilizados ha sido uno de los objetivos principales de esta investigación para intentar dar respuesta a la pregunta de cuál es el mejor método para tratarlas. La base de esta investigación ha sido el uso del método de elementos finitos (EF) para el estudio de las fracturas de meseta tibial y sus tratamientos. Este método consiste en subdividir geometrías complejas en un ensamblado discreto de elementos de geometría sencilla en los que los desplazamientos relativos de puntos pueden ser fácilmente calculados en función de las cargas que se ejercen sobre el elemento. Según la dimensión del problema, estos elementos podrán ser líneas (1D), triángulos o cuadrados (2D), o tetraedros o hexaedros (3D). Los desplazamientos relativos de puntos calculados dentro de los elementos están asociados a valores de tensiones vía la introducción de ecuaciones de comportamiento para el material del elemento virtualmente constituido. El objetivo del primer trabajo (Fixation of a split fracture of the lateral tibial plateau with a locking screw plate instead of cannulated screws would allow early weight bearing: a computational exploration) fue evaluar con cálculos de EF si la carga inmediata de peso sería posible tras la estabilización quirúrgica, ya sea con tornillos canulados o con una placa bloqueada en una fractura de la meseta tibial lateral. El segundo trabajo (An intact fibula may contribute to allow early weight-bearing in surgically treated tibial plateau fractures) intenta dar respuesta a la estabilidad que el peroné proximal aporta en las fracturas de la meseta tibial lateral. Se realizó un modelo de geometría tridimensional mediante elementos finitos a partir de la base de datos VAKHUM (http://www.ulb.ac.be/project/vakhum) y se creó una reconstrucción del modelo a partir de las imágenes de tomografía computarizada. Posteriormente se simuló una fractura tipo de meseta tibial lateral usando datos geométricos a partir de imágenes radiológicas y de TC. Se simularon los sistemas de tratamiento, con y sin peroné, la placa bloqueada Polyax® (Biomet Inc, IN, USA) y un set de tornillos canulados de 6,5 mm (Biomet Inc, IN, USA). Las fracturas de la meseta tibial lateral, fijadas ya sea con placa bloqueadas o con tornillos canulados, no mostraron movimientos interfragmentarios clínicamente relevantes en un modelo de EF. La fijación de la fractura con una placa bloqueada mostró una mayor estabilidad mecánica que la fijación con tornillos canulados. La placa bloqueada podría también permitir una capacidad de carga completa o al menos parcial bajo postura estática. Este modelo de EF mostró que un peroné intacto podría contribuir a la estabilidad mecánica de las fracturas de la meseta tibial lateral, y combinado con placa, la integridad mecánica que aporta el peroné puede permitir una capacidad de carga temprana y sin movimientos interfragmentarios significativos.Tibial plateau fractures affect to the knee joint and they are injuries that often cause functional impairment. To preserve the normal function of the knee, articular congruence must be achieved, stable fixation must be obtained as well as physiological knee aligment in order to recover full range of motion. This goals are often difficult to be achieved due to the soft tissue damage, bone quality and patient comorbidities. The most frecuent injury mechanism is an axial load of the knee combined with and excessive valgus or varus force. Lateral plateau is affected on 55%-70% of the cases and medial plateau on 10%-30%. There is not yet a totally standardized technique to approach all tibial plateau fractures due to the little number of biomechanic studies, therefore there are diferent techniques to treat the same fractures. The aim of this study was to have a better biomechanic understanding of tibial plateau fractures and to compare the most common treatments to asses what is the best way to treat these injuries. This investigation was conducted using finite elements (FE). FE method consists on subdividing complex geometries in a less complex geometry element assemblement. Therefore relative movements in the geometry can be easily measured and accurate calculations can be obtained. Depending on the dimension of the geometry studied the elements can be linear (1D), triangles or squares (2D)or tetrahedrons or hexahedrons (3D). Relative displacements of calculated points inside the elements are associated to tension values with behavioral equations for virtually simulated material and geometry. The purpose of the first study (Fixation of a split fracture of the lateral tibial plateau with a locking screw plate instead of cannulated screws would allow early weight bearing: a computational exploration) was to assess, with finite element (FE) calculations, whether immediate weight bearing would be possible after surgical stabilization either with cannulated screws or with a locking plate in a split fracture of the lateral tibial plateau (LTP). The purpose of the second study ( An intact fibula may contribute to allow early weight-bearing in surgically treated tibial plateau fractures ) was to assess differences in interfragmentary movement (IFM) in a split fracture of lateral tibial plateau, with and without intact fibula. It was hypothesized that an intact fibula could positively contribute to the mechanical stabilization of surgically reduced lateral tibial plateau fractures. A split fracture of the LTP was recreated in a FE model of a human tibia. A three-dimensional FE model geometry of a human femur-tibia system was obtained from the VAKHUM project database, and was built from CT images from a subject with normal bone morphologies and normal alignment. The mesh of the tibia was reconverted into a geometry of NURBS surfaces. A split fracture of the lateral tibial plateau was reproduced by using geometrical data from patient radiographs. A locking screw plate (LP) and a cannulated screw (CS) systems were modelled to virtually reduce the fracture and 80 kg static body-weight was simulated with and without fibula. While the simulated body-weight led to clinically acceptable interfragmentary motion, possible traumatic bone shear stresses were predicted nearby the cannulated screws. With a maximum estimation of about 1.7 MPa maximum bone shear stresses, the Polyax system might ensure more reasonable safety margins. Split fractures of the LTP fixed either with locking screw plate or cannulated screws showed no clinically relevant IFM in a FE model. The locking screw plate showed higher mechanical stability than cannulated screw fixation. The locking screw plate might also allow full or at least partial weight bearing under static posture at time zero. This FE model showed that an intact fibula contributes to the mechanical stability of the lateral tibial plateau. In combination with a locking plate fixation, early weight bearing may be allowed without significant IFM, contributing to an early clinical and functional recovery of the patient

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London