Does the position of a sustentacular screw influence the stability of a plate osteosynthesis of a calcaneal fracture? A biomechanical study.

The purpose of the study was to compare the stability of the plate osteosyntheses of intra-articular calcaneal fractures using various types of a sustentacular screw insertions. A geometrical model of a calcaneal fracture was created. The fracture was fixed with a plate and screws with a uniform distribution. The individual models differed regarding the position of the sustentacular screw. The screw was inserted using three different variants: Model A: into the tip of sustentaculum tali, Model B: under the sustentaculum tali, and Model C: into the inferior peripherial rim of the sustentacular fragment. In all three variants, the screw was either locked into the plate via threads or unlocked. The model was loaded with force in the vertical direction. The stiffness of individual models was evaluated using the finite element method, which was expressed as the maximum force (Fmax) that the system was able to transmit and by determining the magnitude and distribution of reduced stress (σred) on the individual parts of the model of a fixed calcaneal fracture. The greatest stiffness of the system was observed in the Model B (Fmax = 335.8 N). The least stiffness was observed in Model C (Fmax = 296.3 N). This model also produced the greatest load on bone tissue was observed (σmaxred = 67.5 MPa). The least load on bone tissue was measured in Model B (σmaxred = 53.7 MPa). The load on the plate was similar in all three models (814.0-820.0 MPa). The analyses suggest that in a plate osteosynthesis of a calcaneal fracture, the insertion of a sustentacular screw under the tip of the sustentaculum tali is acceptable in terms of osteosynthesis stability. This sustentacular screw position reduces the risk of the screw penetrating into the talocalcaneal joint.

Comparison of Plantar Pressure Distribution During Walking After Two Different Surgical Treatments for Calcaneal Fracture.

The aim of our study was to compare gait in terms of foot loading and temporal variables after 2 different operative approaches (the extended lateral approach [ELA] and sinus tarsi approach). Twenty-two patients who sustained an intra-articular calcaneal fracture underwent plantar pressure distribution measurements 6 months after surgery. Measurements were performed while patients walked on the pedobarography platform. The values of dynamic variables were significantly lower on the operated limb in the ELA. In the sinus tarsi approach, no differences were observed between the operated and uninjured limbs (UIN) at peak pressure and at maximal vertical force. The values of temporal variables (contact time of the foot and of the heel) between the operated and UIN differed in the ELA. The hypothesis that differences in foot load between operated and UIN will be more significant in the ELA was confirmed. Our results showed that the differences in loading and temporal variables between the operated and the UIN persisted 6 months after surgery in both methods. The operated limb was less loaded, with the tendency to shift the load toward the midfoot and forefoot. After the less invasive sinus tarsi approach, the dynamic and temporal variables on the operated limb were nearly the same as those on the healthy one. The sinus tarsi surgical approach can be recommended for treatment of displaced calcaneal fractures.

Differentiation of neural stem cells into cells of oligodendroglial lineage.

We described three different conditions that induce differentiation of dissociated neural stem cells derived from mouse embryonic CNS. In the first set of experiments, where the cell differentiation was triggered by cell adhesion, removal of growth factors and serum-supplemented medium, only sporadic neuronal and astroglial cells survived longer than two weeks and the latter formed a monolayer. When differentiation was induced in serum-free medium supplemented with retinoic acid, rapid and massive cell death occurred. A prolonged survival was observed in cultivation medium supplemented with serum and growth factors EGF plus FGF-2. One third of the cells did not express cell differentiation markers and were responsible for an increase in cell numbers. The remaining cells differentiated and formed the astrocytic monolayer on which occasional neuronal cells grew. One third of the differentiated phenotypes were represented by cells of oligodendroglial lineage. Differentiation of oligodendroglial cells occurred in a stepwise mechanism because the culture contained all successive developmental stages, including oligodendrocyte progenitors, preoligodendrocytes and immature and mature oligodendrocytes. Maturing oligodendrocytes displayed immunocytochemical and morphological features characteristic of cells that undergo physiological development. The cultivation conditions that supported growth and differentiation of neural stem cells were optimal for in vitro developmental studies and the production of oligodendroglial cells.

Stem cell therapy for demyelinating disorders.

Multiple sclerosis (MS) is a progressive disease of the central nervous system (CNS) that attacks mainly young people. It leads to the progressive deterioration of the neurological status. Histopatologically, this disease is characterized by appearance of multiple foci of the demyelination in white matter of the CNS, with various grade of an axonal loss. The current treatment is targeted on moderating the inflammatory process and symptomatic therapy. In spite of all this therapy, the course of the disease often progresses. The tissue of the CNS in mammalians, including humans, is able to provide some degree of spontaneous remyelination. Unfortunatelly the extent of this process is not sufficient for the complete restoration. The support of remyelination by using the cell manipulations is the aim of many experimental studies. Theoretically, it is possible to achieve remyelination either by exogenous induction of remyelination from endogenous sources (precursor cells) or by the real transplantation of myelin-forming cells intrafocally, intracerebroventricularly or into the blood stream. In this work, we present the brief view on the recent state of this topic. We present the list of the cell types, useable for cell transplantations and the summary of the growth factors influencing the behaviour of the oligodendroglial precursors. We are considering the hampers in usage of the cell therapy of demyelinating disorders in clinics.