Biomechanical evaluation of tibial bone adaptation after revision total knee arthroplasty: A comparison of different implant systems

The best methods to manage tibial bone defects following total knee arthroplasty remain under debate. Different fixation systems exist to help surgeons reconstruct knee osseous bone loss (such as tantalum cones, cement, modular metal augments, autografts, allografts and porous metaphyseal sleeves) However, the effects of the various solutions on the long-term outcome remain unknown. In the present work, a bone remodeling mathematical model was used to predict bone remodeling after total knee arthroplasty (TKA) revision. Five different types of prostheses were analyzed: one with a straight stem; two with offset stems, with and without supplements; and two with sleeves, with and without stems. Alterations in tibia bone density distribution and implant Von Mises stresses were quantified. In all cases, the bone density decreased in the proximal epiphysis and medullary channels, and an increase in bone density was predicted in the diaphysis and around stem tips. The highest bone resorption was predicted for the offset prosthesis without the supplement, and the highest bone formation was computed for the straight stem. The highest Von Mises stress was obtained for the straight tibial stem, and the lowest was observed for the stemless metaphyseal sleeves prosthesis. The computational model predicted different behaviors among the five systems. We were able to demonstrate the importance of choosing an adequate revision system and that in silico models may help surgeons choose patient-specific treatments

Using artificial neural networks to predict impingement and dislocation in total hip arthroplasty

Dislocation after total hip arthroplasty (THA) remains a major issue and an important post-surgical complication. Impingement and subsequent dislocation are influenced by the design (head size) and position (anteversion and abduction angles) of the acetabulum and different movements of the patient, with external extension and internal flexion the most critical movements. The aim of this study is to develop a computational tool based on a three-dimensional (3D) parametric finite element (FE) model and an artificial neural network (ANN) to assist clinicians in identifying the optimal prosthesis design and position of the acetabular cup to reduce the probability of impingement and dislocation. A 3D parametric model of a THA was used. The model parameters were the femoral head size and the acetabulum abduction and anteversion angles. Simulations run with this parametric model were used to train an ANN, which predicts the range of movement (ROM) before impingement and dislocation. This study recreates different configurations and obtains absolute errors lower than 5.5° between the ROM obtained from the FE simulations and the ANN predictions. The ROM is also predicted for patients who had already suffered dislocation after THA, and the computational predictions confirm the patient’s dislocations. Summarising, the combination of a 3D parametric FE model of a THA and an ANN is a useful computational tool to predict the ROM allowed for different designs of prosthesis heads

Biomechanical assessment and clinical analysis of different intramedullary nailing systems for oblique fractures

The aim of this study is to evaluate the fracture union or non-union for a specific patient that presented oblique fractures in tibia and fibula, using a mechanistic-based bone healing model. Normally, this kind of fractures can be treated through an intramedullary nail using two possible configurations that depends on the mechanical stabilisation: static and dynamic. Both cases are simulated under different fracture geometries in order to understand the effect of the mechanical stabilisation on the fracture healing outcome. The results of both simulations are in good agreement with previous clinical experience. From the results, it is demonstrated that the dynamization of the fracture improves healing in comparison with a static or rigid fixation of the fracture. This work shows the versatility and potential of a mechanistic-based bone healing model to predict the final outcome (union, non-union, delayed union) of realistic 3D fractures where even more than one bone is involved

Rotura distal del tendón de la porción larga del bíceps braquial. ¿por qué está aumentado su incidencia? ¿Cuándo se debe reparar?

Introduction and objectives: The breaking of the distal biceps tendon is rare and represents only 3% of all breakings of this tendon. However, for the last decade this percentage has increased up to 10%. They are characteristic of middle-aged men with a predominance of the dominant arm. Local risk factor (high functional demand) and systemic ones (smoking, dyslipidemia, steroids, analogies, obesity) are associated with this pathology. Our goal is to analyze the risk factors which are associated with this condition and evaluate the results after surgical repair of the tendon. Materials and methods: Retrospective study of 13 patients diagnosed with distal biceps tendon breaking in our hospital from May 2012 to January 2014. All patients were treated surgically with anatomic reattachment single trak (69, 23 % with Endobutton''s technique and 30, 77 % remembering using harpoons). There have been assessed factors such us potential risk factors, joint mobility, early and late complications and the patient''s degree of satisfaction (scale Karunakar). Their clinical follow-up was carried out for at least 6 months after the surgery. Result: All patients were male, with an average age of 42, 69 years, the 92, 3 % were in the dominant arm, 76, 92 % of the patients usually exercised the biceps while training and 53, 84 % were taking medication for dyslipidemia. The results obtained after the treatment were excellent, shawing that all patients were satisfied with it. Conclusion: The risk factors that are known so far such us smoking, dyslipidemia, steroids, anabolics and obesity do not justify the increase in the currents incidence rate. Regular exercise involving the biceps brachial muscle in patients with risk factors increases the probability of breaking the distal biceps tendon and anatomic reattachment anterior approach is a correct treatment option

Finite Element Analysis of Osteosynthesis Screw Fixation in the Bone Stock: An Appropriate Method for Automatic Screw Modelling

The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent bone stock and can be used for further investigations

Frequency and characteristics of familial melanoma in Spain: The FAM-GEM-1 Study

Similar to that observed in other countries, familial melanoma accounts for 6.6% of melanoma diagnoses in Spain. Although no differences in the multivariate analysis were found, some better prognosis factors, such as Breslow index, seem more frequent in familial melanoma, which reflect a better early detection marker and/or a different biological behavior

Incidencia y factores predictivos del delírium en pacientes neurológicos hospitalizados

Resumen: Introducción: El delírium es una afección con una prevalencia elevada entre los pacientes ingresados (10-30%), con importantes implicaciones pronósticas. Existen pocos estudios prospectivos de incidencia en España y la mayoría se han realizado en plantas quirúrgicas o en unidades de cuidados intensivos. Nuestro objetivo es conocer su incidencia en una planta de neurología y describir las características de estos pacientes. Métodos: Se ha realizado un estudio longitudinal descriptivo, incluyendo a todos los pacientes ingresados en la planta de neurología durante 8 semanas, realizándose la escala CAM para el diagnóstico de delírium el primero, segundo y quinto días de ingreso y recogiéndose de cada paciente datos demográficos, antecedentes patológicos, analíticos (incluyendo marcadores inflamatorios), toma de fármacos anticolinérgicos, situación cognitiva y funcional al ingreso, causa de ingreso, tiempo de estancia y eventos durante la misma. Resultados: Se estudió a 115 pacientes con una incidencia de delírium del 16,52%. Se observó una relación significativa con la edad, la situación cognitiva al ingreso valorada por el test de Pfeiffer, la situación funcional al ingreso medida por la escala Canadiense, la insuficiencia renal, los antecedentes de ACV, la toma de fármacos con actividad anticolinérgica, VSG y PCR. Se observó, además, una mayor estancia media en estos pacientes. Conclusiones: Estos resultados confirman una alta incidencia de esta afección en nuestro medio y, aunque son necesarios más estudios, con muestras mayores, destacamos la importancia de unos factores de riesgo que podrían contribuir a una detección precoz de pacientes en riesgo de desarrollar delírium durante el ingreso, permitiendo actividades preventivas y un tratamiento precoz de estos pacientes. Abstract: Introduction: Delirium is a condition with a high prevalence in hospitalised patients (10%-30%), and it has important prognostic implications. There are few prospective studies of the incidence of delirium in Spain, and most of these were carried out in surgical wards or intensive care units. Our objective is to calculate the incidence of delirium in a neurological department and describe characteristics of affected patients. Methods: Longitudinal descriptive study including all patients admitted to the neurology department in an 8-week period. The CAM score for diagnosing delirium was recorded on the first, second and fifth day of hospitalisation and we recorded demographic data, medical history, analytical data (including inflammatory markers), use of anticholinergic treatments, cognitive and functional state at admission, reason for admission, length of stay, and other events during hospitalisation. Results: We studied 115 patients and found an incidence of delirium of 16.52%. There was a significant correlation between delirium and age, cognitive state at admission according to the Pfeiffer test, functional situation at admission according to the Canadian Neurological Scale, kidney failure, history of stroke, anticholinergic treatment, erythrocyte sedimentation rate, and C-reactive protein. These patients were also hospitalised for longer periods of time. Conclusions: These results confirm a high incidence of delirium in our geographical area. Although additional studies with larger samples are needed, we would like to emphasise the importance of several risk factors which may enable early detection of patients who are at risk for developing delirium during hospitalisation. This would permit preventive action and early treatment for these patients. Palabras clave: Delírium, Síndrome confusional agudo, Fármacos anticolinérgicos, Deterioro cognitivo, Marcadores inflamatorios, Keywords: Delirium, Acute confusional state, Anticholinergic treatments, Cognitive impairment, Inflammatory marker