Virtual Methods Applied to Human Bones and Joints Re-Construction Used for Orthopedic Systems

Abstract

In the first stage of research, real bone components were analyzed to determine the main visual geometric shapes. After that, it was used a CT or MRI device to get parallel sections of studied bone components. In the third stage, the images were transferred to a 2D CAD software like AutoCAD, where the outer and inner contours of the bone were approximated by polygonal lines composed of multiple segments. To obtain virtual bones was used a parametric CAD software that allows defining models with a high degree of difficulty. The contours were transferred to a 3D CAD software, which, step by step, each section was used to define each virtual component of bone. For some components, such as vertebrae, bones of the jaw, the skull bones, was used in a preliminary model consists of curves in parallel planes. Based on this model can be defined the main curves for the final virtual 3D solid model. Also, were defined innovative orthopedic metal components as tibia nail, plates and screws or prosthetic elements. Were defined simulations to determine the behavior of the new orthopedic models through FEA method.

An Experimental and Virtual Approach to Hip Revision Prostheses

“…For this purpose, the surfaces of the ribs, vertebrae, the two portions of the femur, and other elements that were not of interest for our study were removed. Surface decimation methods were also used as well as “finishing” operations, which are described in more detail in other papers [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ].…”

“…The following simplifying assumptions were used in the analyses of the three orthopaedic systems: Knowing that orthopaedic cement, used in these orthopaedic prostheses, provides stability and fixation of the components, it was not geometrically modelled, and its behaviour was replaced with the use of bonded elements that practically provide cohesion of the elements between themselves [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]; It is known that, during the human gait, the variation of the force occurring in the hip joint varies between values of 0 N and about 2300 N. We have considered that it is sufficient to use an equivalent force that has a linear variation between the values of 800 N (characteristic of the orthostatic position) and 2300 N (maximum value of the force during normal human gait [ 26 , 27 , 28 , 29 , 30 , 31 , 39 , 42 ]); For revision prostheses using a morcellated bone graft, the study was considered to be performed after complete osseointegration of the graft, when it acquires the appearance and properties of the trabecular bone [ 26 , 27 , 28 , 39 ]. …”

“…Knowing that orthopaedic cement, used in these orthopaedic prostheses, provides stability and fixation of the components, it was not geometrically modelled, and its behaviour was replaced with the use of bonded elements that practically provide cohesion of the elements between themselves [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ];…”

“…It is known that, during the human gait, the variation of the force occurring in the hip joint varies between values of 0 N and about 2300 N. We have considered that it is sufficient to use an equivalent force that has a linear variation between the values of 800 N (characteristic of the orthostatic position) and 2300 N (maximum value of the force during normal human gait [ 26 , 27 , 28 , 29 , 30 , 31 , 39 , 42 ]);…”

“…For revision prostheses using a morcellated bone graft, the study was considered to be performed after complete osseointegration of the graft, when it acquires the appearance and properties of the trabecular bone [ 26 , 27 , 28 , 39 ].…”