Mechanical Analysis of Wrist External Skeletal Fixator and The Application of Chitosan in Large Bony Defect
Date Issued
2010
Date
2010
Author(s)
Chang, Chih-Hao
Abstract
part 1
Wrist external fixator is widely used in unstable type of distal radius fracture. Although there are many studies about the mechanical analysis of external fixators, there are few papers talking about the mechanical analysis of wrist external fixators. Wrist external fixators are quite different from the external fixators used in the lower extremity. They do not need to bear the body weight. They cross the wrist joint composed of complex carpal bones and ligaments. Usually, wrist external fixators are more slender and less bulky than the ones used in the lower extremity. In most studies for external fixators, they used the mechanical model and finite element model to analyze. The data of true human specimen is deficiency. In our study, we analyzed the loading force to the pins of wrist external fixator in situation of mechanical model, cadaver model, and in vivo human model. The strains of the pins were recorded and analyzed. In the mechanical model, the strains of all pins are proportional to the loading force. The most distal 2 pins afforded compression force and the most proximal 2 pins afforded tension force. In the cadaver model and in human model, the strain of the pin located at the 2nd metacarpal base was near zero. It means this pin afforded minimal force. Loosening of this pin happened frequently. Soft tissues of the wrist joint absorbed partial force and they resulted in the reduction of the strain of all pins. The pins inserted at the radius bone are equally important. When they are assembled together within one clamp, the force will concentrate on one pin. The other pin will afford minimal strain. The mechanical model is an ideal model for analysis of external fixators either upper extremity or lower extremity. But there are some differences when external fixator applied to the real human. Soft tissues and anatomical characteristics of human specimen are the major factors. The most distal pin is very important in WEF because the second pin always loosened. The proximal two pins are the same important. Because they are assembled in one clamp, one pin afforded most force usually and the other pin is mild when the force applied. The force distribution is asymmetry. Usually, the pin near the wrist joint will afford most force. Our study helps to understand true loading condition to the pin of wrist external fixator and the fact that there are differences between 3 models.
part 2
Large bony defect is a difficult condition in orthopedics and dental field. There are many situations resulting in this condition. Large bone tumors, osteomyelitis, severe osteoporosis, and severe periodontitis are met frequently. Usually, the doctors will transplant the autogenous bone from the patient himself or take the allogenic bone from the donors to fill this defect. But there are many potential problems for these two choices. Transmitted disease and limited sources are the most problems we will meet. Recently, artificial biomaterial science developed and got a great progression and improvement for bony substitutes. Many biomaterials were mentioned, studied, and used. This is a rather new field and has a large potential development.
This project is majorly concerned with the invention of the new biomaterials based on chitosan nature polymer in combination with biomolecules for various biomedical applications. The novel technique of combining chitosan with biomolecules such as growth factors used in this project consists in chemical immobilization rather than physical method. The growth factors or other biomolecules immobilized on chitosan are expected to carry the long–term release effect rather than short-term one in the physically adsorption system. The product concept of this research is to immobilize the growth factor to the chitosan scaffold to achieve the osteo-inductive and osteo-conductive effects.
In this study, we applied the chitosan scaffold with immobilized growth factors to bone regeneration and found the positive results. The potential of surface covalently-bonded rhBMP-2 biodegradable chitosan membrane was examined for guided tissue regeneration (GTR) applications. The chitosan surface-bonded rhBMP-2 membrane has the potential as a bioactive material for GTR.
Subjects
distal radius fracture
external skeletal fixator
mechanical analysis
bone
chitosan
chitosan membrane
guided tissue regeneration (GTR)
rhBMP-2
surface modification
SDGs
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-99-D90548006-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):2700581f3a10be460d1c12a059eecbc0