M. Gzik

Modeling and biomechanical analysis of craniosynostosis correction with the use of finite element method

Craniosynostosis is a skull malformation because of premature fusing of one or more cranial sutures. The most common types of craniosynostosis are scaphocephaly (with the sagittal suture fused) and trigonocephaly (with the metopic suture fused). In this paper we describe and discuss how finite element analysis and three-dimensional modeling can be used for preoperative planning of the correction of craniosynostosis and for the postoperative evaluation of the treatment results. We used the engineering software MIMICS MATERIALISE to obtain three-dimensional geometry from computed tomography scans, and applied finite element method for the sake of biomechanical analysis. These simulations help to improve the surgical treatment, making it more accurate, safer, and faster.

Air Gun Impactor—A Novel Model of Graded White Matter Spinal Cord Injury in Rodents

Understanding mechanisms of spinal cord injury and repair requires a reliable experimental model. We have developed a new device that produces a partial damage of spinal cord white matter by means of a precisely adjusted stream of air applied under high pressure. This procedure is less invasive than standard contusion or compression models and does not require surgical removal of vertebral bones. We investigated the effects of spinal cord injury made with our device in 29 adult rats, applying different experimental parameters. The rats were divided into three groups in respect to the applied force of the blast wave. Functional outcome and histopathological effects of the injury were analyzed during 12-week follow-up. The lesions were also examined by means of magnetic resonance imaging (MRI) scans. The weakest stimulus produced transient hindlimb paresis with no cyst visible in spinal cord MRI scans, whereas the strongest was associated with permanent neurological deficit accompanied by pathological changes resembling posttraumatic syringomyelia. Obtained data revealed that our apparatus provided a spinal cord injury animal model with structural changes very similar to that present in patients after moderate spinal cord trauma.

Engineering-aided treatment of chest deformities to improve the process of breathing.

In this paper, the application of new visualization technologies in correction of funnel chest is presented. Often, such defects cause problems with breathing, and therefore, to improve the cardiorespiratory efficiency, a correction is required. The virtual model of chest was formulated to determine the strains and stresses after correction of deformation with using the stabilizing plate. From biomechanical point of view, the knowledge of the load-affecting stabilizer is necessary to select optimal parameters of the plate. The force-affecting plate that was used in the correction of chest deformation by Nuss method was determined on the basis of finite element model of funnel chest. The main aim of this work was to select the optimal thickness of plate. Calculations were conducted for three alternative constraints.

The influence of frequency of visual disorders on stabilographic parameters.

PURPOSE Defining the influence of parameters of visual disorders on ability of balancing turns out to be an important process in effective diagnostics. Current diagnostic methods relating mainly to determination of the coefficient of BRUTM (Balance Rehabilitation Unit Trade Mark) depend on lots of tests carried out in a disturbed environment created by Virtual Reality Technology. The aim of this study is to determine the effect of the frequency of visual disturbances on stabilographic values in the virtual reality environment. METHODS The study was carried out involving one research group in Virtual Cave. There were induced visual disturbances with different frequencies and with the change of frequency during measuring the position of the center of pressure (COP) in the test. Before each test the reference test was performed. All tests were performed with disorders in two different sceneries: closed and open scenery. All measurements were carried out on an immobile Zebris platform which enables determination of feet pressure distribution. From the measured values of the position of the COP Short Time Fourier Transform (STFT) was calculated. RESULTS The results of calculation are shown in graphs. Their analysis showed that changing the parameters of disorder frequency in world created using Virtual Reality Technology affects stabilographic parameters. The intensity of these changes is also affected by applied research scenery. CONCLUSIONS Conditions have been set out to carry out similar studies in order to obtain reliable results. The study is the first step in a project to develop a system for diagnosis and rehabilitation of human movement using Virtual Reality Technology.

Kinematic differences in gait obtained for people with right and left paresis

The article concerns research into gait kinematics of people after stroke. The comparative analyses of angle courses and gait parameters were carried out. Results obtained for people with left and right sided paresis were compared with each other.

Statistical Analysis of Cranial Measurements - Determination of Indices for Assessing Skull Shape in Patients with Isolated Craniosynostosis

This paper presents a morphological analysis of the skull shape in infants under one year of age. Three-dimensional measurements were performed on models generated from images in Mimics software. Subsequently, a multivariate statistical analysis of the measured dimensions was performed to determine key indicators of the skull shape. Eventually it was developed the norms of skull indices for children up to one year of age. Regular values of these indices were compared with abnormal values measured in patients with isolated craniosynostosis. With the use of these indices it is possible to perform a quantitative evaluation of head deformity.

The Upper Limb Motion Deviation Index: A new comprehensive index of upper limb motion pathology

PURPOSE The aim of the research was to formulate a new index enabling assessment of the overall pathology of the upper limb movement. It defines the difference between the pathological movement and a normal movement pattern. METHODS Methodology of determining the index is based on a mathematical algorithm for calculating the Gait Deviation Index which is based on advanced methods of image comparison. To calculate the ULMDI index, one must divide the analyzed movement into cycles appropriate to the nature of the movement (similarly in gait it is the gait cycle) and then determine kinematic quantities (courses of joint angles). RESULTS A group of 23 healthy people (10 women: k1-k10 and 13 men: m1-m13) as the reference group and a group of 3 persons with mobility impairments (p1-p3) took part in the research. Time values of the angles of the joints on both upper limbs were registered and then ULMDI indexes were calculated. CONCLUSIONS It has been shown that the developed ULMDI index allows to detect the deviations from the accepted norm in the performance of movements. The results showed that both the description of the motor dysfunction of examined person based on the diagnosis of the physician, a detailed analysis of kinematic waveforms received during the tests and the calculated values provide a coherent picture of the state of a human movement. The index analysis is less time-consuming for the doctor, and the comparison of the results at various stages of therapy gives an objective picture of the rehabilitation progress.

Biomechanical analysis of injuries of rally driver with head supporting device

PURPOSE The aim of the study was to develop and verify a model of rally driver with a safety system HANS (head supporting device), which will enable biomechanical analysis of injuries in rally accident. METHODS Simulations were carried out in Madymo® software, the results of which were verified based on sled test performed in the Automotive Industry Institute (PIMOT) in Warsaw. The model being verified allowed us to perform a multivariate simulation of rally accident in terms of assessing effectiveness of protection and usefulness of HANS system. RESULTS Acceleration waveforms of the head and chest were obtained from numerical experiment and also forces and moments occurring in the upper cervical spine. The results obtained allowed driver injuries to be analyzed based on injury criteria of the head and neck: HIC15, NTE, NTF, NCE and NCF. CONCLUSIONS The analysis enabled assessment of the driver safety while using 4 and 5 point harness with HANS system. In further studies the model developed was used to identify factors affecting the safety of a rally driver.

Application of 3D modeling and modern visualization technique to neurosurgical trigonocephaly correction in children

The attempt to a new methodology creation, supported neurosurgical correction of trigonocephaly by engineers is presented in this paper. Trigonocephaly is an example of skull deformity, that wrong influence on child physical and psychological development. Conventional procedures in such cases are connected with invasive operation. Up to now neurosurgeons during pre-operation planning of bones correction, based on their own knowledge and experience. Modeling in biomechanics connected with modern visualization methods give new possibilities of engineer support for medical procedures. Three-dimensional model of deformed skull was created on the basis of CT scans with use of Mimics software. The model was transformed to FEM and used for suitable shape of forehead bone determination. Material properties of modeled bones were assumed on the basis of experimental researches. The geometrical model was presented in 3-dimensional virtual reality. It helps to better imagine about the real shape of skull hidden under head skin and take the best decision how to operate the example of trigonocephaly.

The Loads Acting on Lumbar Spine During Sitting Down and Standing Up

The paper presents an analysis of the loads acting on lumbar spine during movement of sitting down and getting up from a chair. The study was conducted on a group of 30 people (parents of disabled children) complaining about chronic low back pain. Basing on kinematics, obtained during experiment from APAS system, simulations were performed in the Anybody Modeling System environment. The use of methods, mathematical modeling and static optimization, allowed to determine the magnitude of the loads acting on musculoskeletal system. The results of reactions in the L5-sacrum joint, the muscular forces of erector spinae and the transversus abdominis are significantly correlated with the kinematics of the movement.