Comparison of methods for assigning the material properties of the distraction callus in computational models.

In silico models of distraction osteogenesis and fracture healing usually assume constant mechanical properties for the new bone tissue generated. In addition, these models do not always account for the porosity of the woven bone and its evolution. In this study, finite element analyses based on computed tomography (CT) are used to predict the stiffness of the callus until 69 weeks after surgery using 15 CT images obtained at different stages of an experiment on bone transport, technique in which distraction osteogenesis is used to correct bone defects. Three different approaches were used to assign the mechanical properties to the new bone tissue. First, constant mechanical properties of the hard callus tissue and no porosity were assumed. Nevertheless, this approach did not show good correlations. Second, random variations in the elastic modulus and porosity of the woven bone were taken from previous experimental studies. Finally, the elastic properties of each element were assigned depending on gray scale in CT images. The numerically predicted callus stiffness was compared with previous in vivo measurements. It was concluded firstly that assignment depending on gray scale is the method that provides the best results and secondly that the method that considers a random distribution of porosity and elastic modulus of the callus is also suitable to predict the callus stiffness from 15 weeks after surgery. This finding provides a method for assigning the material properties of the distraction callus, which does not require CT images and may contribute to improve current in silico models.

Histological study of the docking site after bone transport. Temporal evolution in a sheep model.

INTRODUCTION: Bone transport appears to be a solution for segmental bone defects; specifically, the "docking site" is where the transported segment meets the target segment at the end of the process. A lack of its consolidation is one of the major causes of failure for this technique. Many studies have been performed in order to enhance the consolidation of the docking site, but histological changes occurring in it remain unknown. The aim of this study was to determine microscopic changes present in this area, from distraction to remodeling, in order to clarify the best options to facilitate the success of this technique. MATERIALS AND METHODS: Ten adult sheep were submitted to bone transport using an Ilizarov external fixator. Histomorphometry and immunohistochemical studies were performed in the docking site to determine the main types of ossification, the evolutions of tissues and blood vessels and the distributions of collagen I and II. RESULTS: Ossification was mainly intramembranous with some areas of endochondral ossification. Fibrous tissue was predominant until 98 days after surgery. The area occupied by blood vessels increased until 50 days after surgery, when it decreased slowly until the end of the study. CONCLUSIONS: As far as the authors know, this is the first histological study performed in the docking site reporting the complete evolution of tissues until the end of remodeling, showing results contrary to those published by others authors. This could help to clarify information about its union and may be useful for future investigations about techniques for improving the consolidation of the docking site in humans.

Pelvic post-traumatic asymmetry: Assessment and sequenced treatment.

The most common cause of post-traumatic pelvic asymmetry is, by far, initial nonoperative treatment.Open reduction and internal fixation of unstable pelvic fractures are recommended to avoid pelvic nonunion or subsequent structural deformities.The most common symptom is pelvic pain. Pelvic instability is another symptom, as well as persistent urogenital problems and neurological sequelae.Preoperative evaluation of these patients requires careful clinical and functional assessment, in addition to a complete radiological study.Surgical treatment of pelvic fracture nonunions is technically demanding and has potentially serious complications.We have developed a new classification that modifies and completes Mears and Velyvis's classification in which we highlight two types of post-traumatic sequelae with different clinical conditions and whose basic differentiating element is whether pelvic deformity is present or not. Based on this classification, we have established our strategy of surgical treatment. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170069.

Factores determinantes en la indicación de la prótesis invertida de hombro / Facteurs déterminant l'indication de prothèse d'épaule inversée / Determining Factors in Inverted Shoulder Prosthesis Indication

Objetivo: Desarrollar criterios para determinar las indicaciones apropiadas de la prótesis invertida de hombro en artropatías por lesión del manguito rotador y las variables determinantes de este proceso. Método: Se utilizó un panel de expertos mediante metodología RAND/UCLA con 9 expertos en Traumatología, 2 en Rehabilitación y 1 en Reumatología, que evaluaron 192 casos hipotéticos. Cada experto puntuó mediante una escala del 1 (extremadamente inadecuado) al 9 (extremadamente apropiado). Resultados: 22 casos hipotéticos fueron considerados adecuados. El dolor, limitación funcional, necesidad funcional, defecto glenoideo, edad, artrosis y posibilidad de reparación del manguito rotador son variables determinantes para indicar la implantación de una prótesis invertida de hombro. Conclusiones: El método RAND/UCLA es útil para el estudio de las indicaciones de procedimientos como la prótesis invertida de hombro, y proporciona una lista de las indicaciones adecuadas. Las variables requieren ser validadas mediante estudios prospectivos o revisión de historias clínicas(AU)

Objective: Develop criteria to determine the appropriate indications of inverted shoulder prosthesis in arthropathies due to rotator cuff injury and the variables that determine this process. Method: A panel of experts assessed 192 hypothetical cases using RAND/UCLA methodology. Nine Traumatology experts, two Rehabilitation experts and one Rheumatology expert comprised this panel. Each expert scored on a scale from 1 (extremely unsuitable) to 9 (extremely appropriate). Results: 22 hypothetical cases were considered adequate. Pain, functional limitation, functional need, glenoid defect, age, osteoarthritis and possibility of rotator cuff repair are determining as variables to indicate the implantation of an inverted shoulder prosthesis. Conclusions: The RAND/UCLA method is useful for the study of procedure indications such as the inverted shoulder prosthesis, and it provides a list of suitable indications. Prospective studies or medical record reviews should validate these variables(AU)

Objectif: Proposer les critères définissant l'indication appropriée de prothèse d'épaule inversée dans les arthropathies pour lésion de la coiffe des rotateurs, et les variables déterminant ce processus. Méthodes: Un panel d'experts, compris par 9 traumatologues, 2 kinésithérapeutes et 1 rhumatologue, a été utilisé pour évaluer 192 cas hypothétiques par la méthode RAND/UCLA. Chaque expert a fait son évaluation sur une échelle de 1 (extrêmement inapproprié) à 9 (extrêmement approprié). Résultats: Vingt-deux cas hypothétiques ont été considérés comme appropriés. Des variables telles que la douleur, la limitation fonctionnelle, la nécessité fonctionnelle, le défaut glénoïdien, l'âge, l'arthrose et la possibilité de correction de la coiffe des rotateurs, ont déterminé l'indication de prothèse d'épaule inversée. Conclusions: La méthode RAND-UCLA est utile pour l'étude des indications de procédés, tels que la prothèse d'épaule inversée, et procure une liste des indications appropriées. Il faut valider les variables avec des études prospectives ou une révision des dossiers médicaux(AU)

Histological evolution of the regenerate during bone transport: an experimental study in sheep.

INTRODUCTION: Bone transport (BT) for segmentary bone defects is a well-known technique as it enables correction with new bone formation, which is similar to the previous bone. Despite the high number of experimental studies of distraction osteogenesis in bone lengthening, the types of ossification and histological changes that occur in the regenerate of the bone transport process remain controversial. OBJECTIVE: The aim of this study is to provide the complete evolution of tissues and the types of ossification in the regenerate during the different phases of bone formation after BT until the end of the remodelling period. METHODS: A histological study was performed using ten adult sheep that were submitted to BT. The types of ossification as well as the evolution of different tissues in the regenerate were determined using histomorphometry and inmunohistochemical studies. The evolution of trabeculae thickness, osteoblast and osteoclast densities, relationship between collagen types and changes in vascularization were also studied. RESULTS: Ossification was primarily intramembranous, with some focus of endochondral ossification in isolated animals. The cell counts showed a progression of cellular activity from the periphery to the centre, presenting the same progression as the growth of bone trabeculae, whose trabeculae thickness was quadrupled at the end of remodelling. Inmunohistochemical studies confirmed the prevalence of type I collagen and the ratio of the Type I/Type II collagen ratio was found to be 2.48. The percentages of the vascularized areas were proximally higher than distally in all animals, but distal zone obtained higher rates than the central region. CONCLUSIONS: Bone transport regenerate exhibits a centripetal ossification model and a mixed pattern with predominance of intramembranous over endochondral ossification. The data obtained resemble partially to those found in models of bone lengthening applied to large animals. This study provides a detailed structural characterization of the newly formed tissue, which may help to explain the development of the regenerate of bone transport in humans. It will also serve for future mechanobiological models that may aid research on the effect of loading or distractor stiffness in clinical results.

Is cannulated-screw fixation an alternative to plate osteosynthesis in open book fractures? A biomechanical analysis.

OBJECTIVES: The current biomechanical work compares the symphyseal and sacroiliac stability obtained with two systems of bone osteosynthesis. The two methods of fixation compared were the 6-hole suprapubic non-locked plate and pubic fixation with two cannulated screws, a novel technique that can be applied percutaneously in the clinical practice. The aim of this study was to examine the validity of the use of two-cannulated-screws osteosynthesis in order to minimize the secondary effects of open fixation, especially in patients in whom an open reduction is contraindicated. MATERIALS AND METHODS: A biomechanical study was designed in 9 fresh, human pelvis specimens, simulating an AO B1.1 type injury, using both fixation systems sequentially in each specimen. In both parts of the test, the specimens were subjected to an axial load of 300N. Displacements and rotations between the different pelvic elements were studied by means of a discrete set of points. The absence of differences between the two systems has been set as the null hypothesis. RESULTS: There were significant differences in favor of the cross-cannulated screws in most of the displacements measured at the pubic symphysis and sacroiliac joint. CONCLUSIONS: Fixation of the AO B1.1 type fractures with cross cannulated screws restores the biomechanical behavior of the pubic symphysis, obtaining better stability than fixation with the 6-hole non-locked plate. To date, no comparative, biomechanical studies have been conducted with these two systems of osteosynthesis. This study demonstrates that cross-cannulated screws fixation of the pubic symphysis in AO B1.1 pelvic fractures should be considered as an alternative to the conventional plating system.