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Biomedical subjects

A M Mohsen

Publications and source records attributed to A M Mohsen.

13 recordsLinked to original sources
PubMed2002

Finite element analysis in spine research.

Finite element analysis is a widely accepted tool used in many industries and research activities. It allows new designs to be thoroughly 'tested' before a prototype is even manufactured, components and systems which cannot readily be experimented upon to be examined, and 'diagnostic' investigations to be undertaken. Finite element models are already making an important contribution to our understanding of the spine and its components. Models are being used to reveal the biomechanical function of the spine and its behaviour when healthy, diseased or damaged. They are also providing support in the design and application of spinal instrumentation. The spine is a very complex structure, and many of the models are simplified and idealized because of the complexity and uncertainty in the geometry, material properties and boundary conditions of these problems. This type of modelling simplification is not peculiar to spinal modelling problems. Indeed, the idealization is often a strength when there is such uncertainty and variation between one individual and another, allowing cause-effect relationships to be isolated and fully explored, and the inherent variability of experimental tests to be eliminated. This paper reviews the development of finite element analysis in spinal modelling. It shows how modelling provides a wealth of information on our physiological performance, reduces our dependence on animal and cadaveric experiments and is an invaluable complement to clinical studies. It also leads to the conclusion that, as computing power and software capabilities increase, it is quite conceivable that in the future it will be possible to generate patient-specific models that could be used for patient assessment and even pre- and inter-operative planning.

Biomechanical Phenomena↗
PubMed2002

Patient-specific spine models. Part 1: Finite element analysis of the lumbar intervertebral disc--a material sensitivity study.

If patient-specific finite element models of the spine could be developed, they would offer enormous opportunities in the diagnosis and management of back problems. Several generic models have been developed in the past, but there has been very little detailed examination of the sensitivity of these models' characteristics to the input parameters. This relationship must be thoroughly understood if representative patient-specific models are to be realized and used with confidence. In particular, the performance of the intervertebral discs are central to any spine model and need detailed investigation first. A generic non-linear model of an intervertebral disc was developed and subjected to compressive, flexion and torsional loading regimes. The effects of both material and geometric non-linearities were investigated for the three loading schemes and the results compared with experimental data. The basic material properties of the fibres, annulus and nucleus were then varied and the effects on the stiffness, annulus bulge and annulus stresses analysed. The results showed that the non-linear geometry assumption had a significant effect on the compression characteristics, whereas the non-linear material option did not. In contrast, the material non-linearity was more important for the flexural and torsional loading schemes. Thus, the inclusion of non-linear material and geometry analysis options in finite element models of intervertebral discs is necessary to predict in vivo load-deflection characteristics accurately. When the influence of the material properties was examined in detail, it was found that the fibre properties did not have a significant effect on the compressive stiffness of the disc but did affect the flexural and torsional stiffnesses by up to +/-20 per cent. All loading modes were sensitive to the annulus properties with stiffnesses varying by up to +/-16 per cent. The model also revealed that for a particular compressive deformation or flexural or torsional rotation, the disc bulge was not sensitive to any of the material properties over the range of properties considered. The annulus stresses did differ significantly as the material properties were varied (up to 70 per cent under a compressive load and 60 per cent during disc flexion).

Compressive Strength↗
PubMed2001

Surgical trainee assessment using a VE knee arthroscopy training system (VE-KATS): experimental results.

Previous work has described the development of a Virtual Environment Knee Arthroscopy Training System (VE-KATS): a collaborative project between the Orthopaedic Department, Hull and East Yorkshire Hospitals NHS Trust, Hull, U.K., and the Department of Computer Science, University of Hull, U.K. This work describes the initial results obtained by Orthopaedic Surgical Trainees using VE-KATS. The results showed that differences between individual trainees could be measured using the scoring system incorporated within VE-KATS. There was a weak correlation with the seniority of the surgical trainees.

Arthroscopy↗
PubMed2000

Computer and robotic assisted osteotomy around the knee.

The outcome variability and failures of conventional osteotomy have been attributed to lack of preoperative planning and inaccuracy in performing the correction. We present a computer and robotic assisted surgery system that can aid in accurate surgical planning for realignment, and in precisely implementing the plan in theatre. The approach seeks to avoid the cost and risks associated with the use of CT, and the insertion of fiducial markers, which are characteristic of existing computer assisted surgical systems. The paper details the architecture of the system as a whole, placing particular emphasis on planning technique. It is anticipated that the increased accuracy possible with the system will prove particularly useful for correcting multi-plane deformities, which are more problematic with conventional techniques.

Bone Malalignment↗
PubMed1999

A portable virtual environment knee arthroscopy training system with objective scoring.

We have developed a Virtual Environment Knee Arthroscopy Training System (VE-KATS). Formative analysis indicated several features which surgical trainees indicated were necessary for a system to be useful. We have addressed this need by incorporating both rigid and deformable objects, simultaneous use of camera and surgical instrument, improved optical modeling, portability and low cost. A major advance has been the incorporation of automated objective scoring of performance. VE-KATS has now progressed to a viable training system which will be of practical benefit to trainee orthopaedic surgeons.

Arthroscopy↗
PubMed1999

A technique for very high accuracy image intensifier calibration.

Accurate characterisation of the image distortion within a fluoroscopic image intensifier is critical if it forms the vision component of an image guided surgical system. By considering non-linear dynamic distortion it is possible to greatly increase the accuracy of the image intensifier, although at the cost of some image quality.

Calibration↗
PubMed1998

Review of orthopaedic manipulator arms.

Trajectory planning and implementation forms a substantial part of current and future orthopaedic practice. This type of surgery is governed by a basic orthopaedic principle [1] which involves the placement of a surgical tool at a specific site within a region, via a trajectory which is planned from X-ray based 2D images and governed by 3D anatomical constraints. The accuracy and safety of procedures utilising the basic orthopaedic principle depends on the surgeon's judgement, experience, ability to integrate images, utilisation of intra-operative X-ray, knowledge of anatomical-biomechanical constraints and eye hand dexterity. The surgeon must remain as the responsible medical expert in charge of the overall system. At the same time the surgeon covets the accuracy offered by Computer Assisted Surgery including a manipulator. A summary of current inadequacies of manipulators indicates that the main drivers for future work are that accuracy is critical in close contact with the environment, safety concerns dictate manipulator geometry and technological limitations are many. In any effort to develop an optimal manipulator to guide surgical instruments and tools it is an obvious first step to review and categorise current manipulators. The aim of this paper is to review all aspects of manipulator design against the five main criteria of ergonomics; safety; accuracy; sterility and measurable benefits such as reduced operative time, reduced surgical trauma and improved clinical results.

Equipment Design↗
PubMed1998

Assessment and upgrading of knowledge and attitudes among nurses and university graduates towards AIDS.

This study aimed to assess and upgrade the level of knowledge and attitudes towards AIDS among nurses and university graduates (U.G.). The study used pre-test, post-test with no control group design. It was done over a period from January 1995 to July 1996. Four hundred and thirty four nurses and 244 U.G. were subjected to baseline questionnaire and health education lecture about mean score of knowledge and attitudes were significantly improved from pre to post-lecture among both groups (p=0.0001). There were no significant differences in the levels of knowledge and attitudes pre and post-lecture between the two studied groups, or participants' sex (p>O.05). There were statistically significant differences between married and single participants with high levels among married (p=0.003). Logistic regression analysis showed that marriage was the strongest predictor variable of good knowledge score (> or =75%).

Acquired Immunodeficiency Syndrome↗
PubMed1997

A computer assisted orthopaedic surgical system for distal locking of intramedullary nails.

This paper presents a prototype system for computer assisted surgery, the purpose of which is to assist orthopaedic surgeons when performing distal locking of intramedullary nails. This system comprises three components, namely: an Intelligent Image Intensifier, a Trajectory Tactician and an Intelligent Trajectory Guide. The Intelligent Image Intensifier is an X-ray vision system that provides accurate X-ray images. Such images enable the Trajectory Tactician software to analyse the operation site and calculate the trajectory required for a screw to lock an intramedullary nail. This involves the capture of two X-ray images from which are extracted the projections of the nail's edge boundaries and its distal locking holes. Using an analytical mathematical model of the nail, the position and orientation of the nail is determined. The trajectory is then implemented by the surgeon using the Intelligent Trajectory Guide. Evaluation in the laboratory suggests that the system is capable of reliably inserting a locking screw into an intramedullary nail. The rapidity with which this computer assisted method achieves locking should benefit both patient and surgeon by reducing radiation dosage and the length of time required to lock a nail.

Bone Screws↗
PubMedDate not supplied

Monitoring of pesticide residues in human milk, soil, water, and food samples collected from Kafr El-Zayat Governorate.

Pesticide residues in human milk and environmental samples from Kafr El-Zayat Governorate in Egypt were analyzed. This governorate is located near one of the biggest pesticide factories in Egypt. Organochlorine and organophosphorus pesticides were monitored, including those that have been prohibited from use in Egypt. Human milk samples (31 samples) from Kafr El-Zayat were compared with 11 samples collected from Cairo. Data were compared with results from studies performed in 1987 and 1990. The present study showed that aldrin and dieldrin, heptachlor and heptachlor epoxide, and endrin residues have been eliminated from human milk. Estimated daily intakes (EDIs) of DDT complex and gamma-HCH by breast-fed infants in Kafr El-Zayat were 85.96 and 3.1% of the respective acceptable daily intakes (ADIs). beta-HCH residues showed an increasing pattern, especially in human milk samples from Cairo. DDT complex and HCH isomers in orange, spinach, lettuce, potatoes, and clover samples ranged from undetectable to very low concentrations. Higher levels of DDT and HCH were detected, but aldrin, dieldrin, endrin, and the heptachlors were not detected in food of animal origin. Residues in fish samples were below maximum residue limits established by some developed countries. Those in animal milk samples approached the extraneous residue limits of the Codex Committee on Pesticide Residues. HCH residues in soil were negligible, but DDT residues in soil were somewhat higher. Among water samples, groundwater samples had the highest residues of HCHs and DDTs, followed by Nile River water and then tap water. However, the organochlorine pesticide residues were found at concentrations below the maximum allowable limits set by the World Health Organization for drinking water. Among 12 organophosphorus pesticides monitored as parent compounds, dimethoate, malathion, methamidophos, and chlorpyrifos residues were detected in low concentrations in soil samples from a pesticide factory. No organophosphorus pesticide residues were found in plant samples, except for very low residues of dimethoate in an orange sample. Water samples were devoid of organophosphorus residues as parent compounds.

Animals↗