A mathematical model for the use of a Gough-Stewart platform mechanism as a fixator

One of the spatial external fixators, which can provide six degrees of freedom, three rotations and three translations, in handling extremity fractures and deformity-correction cases, is the so-called Gough-Stewart Platform Mechanism with six adjustable bars and two platforms. A mathematical model is developed for an effective deployment of the apparatus in orthopaedic processes. The model basically accepts input radiographic and clinical data and provides the bar lengths under several conditions and possibilities systematically studied, on the one hand, and predicts the behavior of the fixator assembly as to the guiding of the bone fragments in a controlled fashion determined by the treatment strategy, on the other. Numerical examples are presented to verify the model. © Springer Science + Business Media B.V. 2006

A theoretical and experimental investigation of lateral deformations in a unilateral external fixator

The objective of this work is to set up, validate, and analyze a theoretical model of an external fixator for its deformation characteristics in order to draw reliable conclusions relevant to the design and effective clinical implementation of such medical devices. External fixators are mechanical devices widely used in the treatment of fractured bones and correction of limb deformities. Lateral deformation at the fracture site is known to delay bone healing, and investigation of lateral deformation characteristics of such devices experiencing forces acting perpendicular to the bone axis is important from the standpoint of their design as well as their clinical effectiveness. A mathematical model of a three-dimensional (3D) unilateral fixator with multipin fragment attachments has been developed using Castigliano's method. The relative lateral deformations of the fragment ends at the fracture site induced by loads applied perpendicular to bone axes are calculated with the model. The model has been subjected to experimental verification for a uniplanar unilateral external fixator under comparable conditions with the theory. It has been found out that the effects of fixator size, shape, and geometry on the level of relative lateral displacement of the fracture site are similar in both the theoretical and experimental models. Stiffness is a maximum if the force is applied in the same plane as the proximal pin plane. Placing the distal pin group at a 90 deg position relative to the proximal pin plane has been observed to increase the stiffness about 10%. In loading directions perpendicular to proximal the pin plane, stiffness is minimum. The angle difference between the load direction and the resulting displacement direction follows a sinusoidal pattern with an amplitude of 10 deg for loading angles in the 0-180 deg range. Selecting the distance of proximal pins to the fracture site smaller than the distance of distal pins to the fracture site has been found to decrease relative lateral deformation. The model and the experiment have simultaneously demonstrated that lower values of effective pin lengths and higher values of pin connector lengths lead to higher stiffness. Increasing the number of pins also contributes to the higher values of fixator stiffness. Copyright © 2007 by ASME

Effects of lower extremity rotation on prognosis of flexible flatfoot in children

The aim of this study is to search the effects of tibial torsion on flexible flatfoot. For this purpose, 20 children with flexible flatfoot and external tibial torsion were determined as a study group, The control group which consisted of 10 children with flexible flatfoot without rotational problems was included in the study. Plantar flexion angle of talus, talo-1, metatarsal angle and dorsoplantar talocalcaneal angle were measured on standing foot radiographs. Tibial torsion was measured by computed tomography Plantar flexion angle of talus and dorsoplantar talocalcaneal angle were found significantly lower in the study group (p<0.005 and p<0.005 respectively), although talo-1. metatarsal angle was not significantly different between the groups (p=.2917). Naviculo-cuneiform sag was prominent in all cases of study group, In conclusion, abnormal external tibial torsion may affect the foot deformity and this can change the benign nature of the flexible flatfoot

Accidental displacement of an impacted mandibular third molar into the lateral pharyngeal space

PubMedID: 10632172[No abstract available

Necrotising enterocolitis in term neonates [Zamaninda dogan bebeklerde nekrotizan enterokolit]

Necrotising enterocolitis (NEC), an important disease of the gastrointestinal system in neonatal period, is characterised by total or partial ischemia of the intestines. Although most of the affected neonates are premature, 10% of the patients are term neonates. Here we present three term neonates who were operated due to Grade 3 NEC during their follow-up. The aim of this report is to emphasize the NEC in term neonates although it is mainly a problem of the premature neonates

Congenital anterior dislocation of the radial head: a case with radiographic findings identical to traumatic dislocation

Differentiation of congenital unilateral dislocation of the radial head from a traumatic dislocation depends mainly on the radiographic findings. Here, we report a case of congenital unilateral anterior radial head dislocation with radiographic findings identical to traumatic dislocation. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved

Iliolumbar veins have a high frequency of variations

The spectrum of individual anatomic variations of the vascular structures are broad, however, the exact incidence of variations of the lumbosacral vein is obscure. In the current study, 38 iliolumbar veins were dissected from 19 formaldehyde-preserved male cadavers. The drainage pattern of the iliolumbar vein was determined. The diameter and the length of the iliolumbar vein were measured, and the relationships of the iliolumbar vein with the lumbosacral trunk, obturator nerve, and iliolumbar artery were ascertained. Means and standard deviations were used as descriptive measures to define variations among the cases. The iliolumbar vein or veins were detected in both sides of all 19 cadavers. Five drainage patterns were seen between the iliolumbar vein and the lumbosacral major veins. In only five cadavers, symmetric drainage patterns were seen on the left and the right sides. In our study, two drainage patterns were seen that were not previously reported. Anatomic variations of the iliolumbar vein are numerous and should be considered to avoid complications when doing surgery