Abordaje transfibular modificado para fracturas del platillo tibial posterolateral. Serie de Casos / Modified transfibular approach for posterolateral tibial plateau fractures. Case Series

Introducción Las fracturas del platillo tibial posterolateral exigen un abordaje que permita una buena visualización de la superficie articular para su restitución anatómica, restablecimiento de la altura y un espacio adecuado para la aplicación del material de osteosíntesis y fijación estable. Hay diversos abordajes descritos en la literatura que no proporcionan la visualización deseada o conllevan múltiples limitaciones y/o complicaciones. El propósito de este estudio es describir una modificación a la técnica quirúrgica de la osteotomía de la fíbula para el manejo de las fracturas de platillo tibial posterolateral. Materiales y métodos Se presentan los resultados clínicos de una serie de casos retrospectiva de 15 pacientes con fracturas de platillo tibial posterolateral que al momento del estudio tenían un seguimiento promedio de 6 meses. Resultados Los resultados funcionales en escala de Lysholm fueron excelentes en 3 pacientes, buenos en 8 y regulares en 4. En todos los pacientes se logró una reducción satisfactoria de la superficie articular de la tibia, sin pérdida de altura de la misma, con alineación adecuada, sin síntomas de inestabilidad, todos con consolidación de la fíbula que no retrasó la rehabilitación, no hubo lesiones del nervio peroneal ni problemas con la piel; se presentó un caso de infección superficial que se manejó con antibióticos orales sin complicaciones. Discusión El abordaje descrito facilita una amplia exposición de la superficie articular, es técnicamente fácil y reproducible, permite la reducción y fijación necesaria, con menor riesgo de complicaciones, con la cual se conserva el aporte vascular de la tibia proximal, se evita el daño a la articulación tibiofibular proximal y se propicia una mayor área de consolidación de la osteotomía. Ésta técnica puede utilizarse sola o en combinación con otros abordajes, para fracturas agudas o crónicas con mala unión. Consideramos que el abordaje con la técnica descrita es una alternativa para el manejo de las fracturas posterolaterales, con resultados alentadores.

Background Fractures of the posterolateral tibial plateau require an approach that allows a good visualization of the articular surface for its anatomical restitution, restoration of height and an adequate space for the application of osteosynthesis material and stable fixation. There are several approaches described in the literature that do not provide the desired visualization or involve multiple limitations and / or complications. The purpose of this study is to describe a modification to the surgical technique of the fibula osteotomy for the management of posterolateral tibial plate fractures. Methods We present the clinical results of a retrospective case series of 15 patients with posterolateral tibial plate fractures that at the time of the study had an average follow-up of 6 months. Results Functional results in Lysholm scale were excellent in 3 patients, good in 8 and regular in 4. Good results were obtained in all patients with a reduction of the tibia articular surface, without loss of height of the same, with alignment adequate, without symptoms of instability, all with consolidation of the fibula that did not delay rehabilitation, there were no peroneal nerve injuries or problems with the skin; There was a case of superficial infection that was managed with oral antibiotics without complications. Discussion The described approach facilitates a broad exposure of the articular surface, is technically easy and reproducible, allows the necessary reduction and fixation, with a lower risk of complications, with which the vascular supply of the proximal tibia is conserved, the damage is avoided to the proximal tibiofibular joint and a greater area of consolidation of the osteotomy is favored. This technique can be used alone or in combination with other approaches, for acute or chronic fractures with poor union. We consider that the approach with the described technique is an alternative for the management of posterolateral fractures, with encouraging results.

Alterations in zebrafish development induced by simvastatin: Comprehensive morphological and physiological study, focusing on muscle.

The cholesterol synthesis inhibitor simvastatin, which is used to treat cardiovascular diseases, has severe collateral effects. We decided to comprehensively study the effects of simvastatin in zebrafish development and in myogenesis, because zebrafish has been used as a model to human diseases, due to its handling easiness, the optical clarity of its embryos, and the availability of physiological and structural methodologies. Furthermore, muscle is an important target of the drug. We used several simvastatin concentrations at different zebrafish developmental stages and studied survival rate, morphology, and physiology of the embryos. Our results show that high levels of simvastatin induce structural damage whereas low doses induce minor structural changes, impaired movements, and reduced heart beating. Morphological alterations include changes in embryo and somite size and septa shape. Physiological changes include movement reduction and slower heartbeat. These effects could be reversed by the addition of exogenous cholesterol. Moreover, we quantified the total cell number during zebrafish development and demonstrated a large reduction in cell number after statin treatment. Since we could classify the alterations induced by simvastatin in three distinct phenotypes, we speculate that simvastatin acts through more than one mechanism and could affect both cell replication and/or cell death and muscle function. Our data can contribute to the understanding of the molecular and cellular basis of the mechanisms of action of simvastatin.

Structural analysis of alterations in zebrafish muscle differentiation induced by simvastatin and their recovery with cholesterol.

In vitro studies show that cholesterol is essential to myogenesis. We have been using zebrafish to overcome the limitations of the in vitro approach and to study the sub-cellular structures and processes involved during myogenesis. We use simvastatin--a drug widely used to prevent high levels of cholesterol and cardiovascular disease--during zebrafish skeletal muscle formation. Simvastatin is an efficient inhibitor of cholesterol synthesis that has various myotoxic consequences. Here, we employed simvastatin concentrations that cause either mild or severe morphological disturbances to observe changes in the cytoskeleton (intermediate filaments and microfilaments), extracellular matrix and adhesion markers by confocal microscopy. With low-dose simvastatin treatment, laminin was almost normal, and alpha-actinin was reduced in the myofibrils. With high simvastatin doses, laminin and vinculin were reduced and appeared discontinuous along the septa, with almost no myofibrils, and small amounts of desmin accumulating close to the septa. We also analyzed sub-cellular alterations in the embryos by electron microscopy, and demonstrate changes in embryo and somite size, septa shape, and in myofibril structure. These effects could be reversed by the addition of exogenous cholesterol. These results contribute to the understanding of the mechanisms of action of simvastatin in muscle cells in particular, and in the study of myogenesis in general.

Growth hormone receptors in zebrafish (Danio rerio): adult and embryonic expression patterns.

Growth hormone receptor (GHR) is a critical regulator of growth and metabolism. Although two GHRs have been characterized in many fish species, their functional characteristics, mechanisms of regulation and roles in embryonic development remain unclear. The zebrafish (Danio rerio) is an excellent model organism to study both developmental and physiological processes. In the present work, we characterized the complete cDNA sequences of zebrafish GHRs, ghra and ghrb, and their gene structures. We studied the expression of both receptors in adult tissues, and during embryonic development and larval stages by means of RT-PCR and whole-mount in situ hybridization. We determined that both transcripts are maternal ones, with specific expression patterns during development. Both GHR transcripts are mainly expressed in the notochord, myotomes, anterior structures and in the yolk cell. Interestingly, their expression became undetectable at 96h post-fertilization. Unlike other reports in fish, ghrs expression could not be detected in brain when adult tissues were used, and we detected ghrb but not ghra transcripts in muscle. In addition, we determined alternative transcript sequences for ghra with specific domain deletions, and alternative transcripts for ghrb that generate a premature stop codon and codify for truncated isoforms. These isoforms lack intracellular regions necessary for the activation of signal transducers and activators of transcription (STAT) family transcription factors 5.