Mechanical Strength and Stiffness of Biodegradable and Titanium Osteofixation Systems

Purpose:\ud To present relevant mechanical data to simplify the selection of an osteofixation system for situations requiring immobilization in oral and maxillofacial surgery.\ud \ud Materials and Methods:\ud Seven biodegradable and 2 titanium osteofixation systems were investigated. The plates and screws were fixed to 2 polymethylmethacrylate (PMMA) blocks to simulate bone segments. The plates and screws were subjected to tensile, side bending, and torsion tests. During tensile tests, the strength of the osteofixation system was monitored. The stiffness was calculated for the tensile, side bending, and torsion tests.\ud \ud Results:\ud The 2 titanium systems (1.5 mm and 2.0 mm) presented significantly higher tensile strength and stiffness compared with the 7 biodegradable systems (2.0 mm, 2.1 mm, and 2.5 mm). The 2.0 mm titanium system showed significantly higher side bending and torsion stiffness than the other 8 systems.\ud \ud Conclusion:\ud Based on the results of the current study, it can be concluded that the titanium osteofixation systems were (significantly) stronger and stiffer than the biodegradable systems. The BioSorb FX (Linvatec Biomaterials Ltd, Tampere, Finland), LactoSorb (Walter Lorenz Surgical Inc, Jacksonville, FL), and Inion (Inion Ltd, Tampere, Finland) 2.5 mm systems have high mechanical device strength and stiffness compared with the investigated biodegradable osteofixation systems. With the cross-sectional surface taken into account, the Biosorb FX system (with its subtle design) proves to be the far more superior system. The Resorb X (Gebrüder Martin GmbH & Co, Tuttlingen, Germany) and MacroPore (MacroPore Biosurgery Inc, Memphis, TN) systems present to be, at least from a mechanical point of view, the least strong and stiff systems in the test

Torsion strength of biodegradable and titanium screws:A comparison

Purpose: To determine 1) the differences in maximum torque between 7 biodegradable and 2 titanium screw systems, and 2) the differences of maximum torque between “hand tight” and break of the biodegradable and the titanium osteofixation screw systems. Materials and Methods: Four oral and maxillofacial surgeons inserted 8 specimens of all 9 screw systems in polymethylmethacrylate plates. The surgeons were instructed to insert the screws as they would do in the clinic (hand tight). The data were recorded by a torque measurement meter. A PhD resident inserted 8 specimens of the same set of 9 screw systems until fracture occurred. Likewise, the maximum applied torque was recorded. Results: 1) The mean maximum torque of the 2 titanium screw systems was significantly higher than that of the 7 biodegradable screw systems, and 2) the mean maximum torque for hand tight was significantly lower than for break in 2 biodegradable, and both titanium screw systems. Conclusions: Based on the results, we conclude that the 1.5 mm and 2.0 mm titanium screw systems still present the highest torque strength compared with the biodegradable screw systems. When there is an intention to use biodegradable screws, we recommend the use of 2.0 mm BioSorb FX (Linvatec Biomaterials Ltd, Tampere, Finland), 2.0 mm LactoSorb (Walter Lorenz Surgical Inc, Jacksonville, FL), or the larger 2.5 mm Inion (Inion Ltd, Tampere, Finland) screws

Biomechanical and surface physico-chemical analyses of used osteosynthesis plates and screws - Potential for reuse in developing countries?

Reprocessing of single-use devices is an upcoming issue in the Western world, but has been for many years in developing countries. In developing countries, the number of bone fractures due to traffic or industrial accidents is high. Patients often need an osteosynthesis with plates and screws, but most patients, however, cannot afford this because of the costs involved and have to rely on the application of used plates and screws. This study aims to determine whether used plates can be safely reused in another patient from a biomechanical, surface physico-chemical, and biological point-of-view. Osteosynthesis plates weakened in a predictable way during use, regardless of the history, presumably because tests were conducted under extreme conditions in the absence of clinically applied load-sharing between bone and plate. Surface physico-chemical analyses indicated that used plates and screws were more hydrophillic than new ones; had increased amounts of calcium-phosphates at their surfaces and possessed higher number of scratches. Pitting corrosion could be seen on SEM micrographs. Simple cleaning methods, as available in developing countries, including toothbrush, water, detergent and bleach yielded elemental surface compositions, and hydrophobicities similar to those of new ones, while biologically thus cleaned screws were not cytotoxic according to ISO-10993-5 and endotoxin release according to USP-27-NF-22 was within the requirements of the FDA. It is concluded that the reuse of osteosynthesis plates and screws are not necessarily unsafe, although preferably a register should be kept of all previous users to limit the number of reuses as mechanical weakening does occur. (c) 2006 Wiley Periodicals, Inc

In vivo experiments with tracheostoma tissue connector prototypes

In cancer patients who have undergone total surgical removal of the larynx, ideally voice rehabilitation should be performed using a shunt valve (placed in a fistula of the tracheo-esophageal wall) and a tracheostoma valve (TSV) to enable hands-free tracheo-esophageal speech. A tracheostoma is created by suturing the trachea into the lower anterior part of the neck, and a TSV is a device that can be placed at the stoma. Unfortunately, many patients are unable to use a TSV, mainly due to fixation difficulties. To improve the fixation of the TSV, tracheostoma tissue connector (TS-TC) prototypes have been designed. Prototype 1 consisted of a titanium ring, inner diameter 30 mm, with a circular polypropylene mesh glued to it with silicone adhesive. Four holes had been drilled into the ring for the insertion of sub- and percutaneous screws. Prototype 2 consisted of a silicone rubber ring, inner diameter 30 mm, combined with polypropylene mesh and four titanium inserts that functioned as a base plate for the insertion of sub- and percutaneous screws. In adult female goats a tracheostoma was created and the prototypes were implanted. After 6 weeks of subcutaneous implantation, percutaneous screws were inserted. After twelve weeks, the experiment was terminated and the implants with the surrounding tissues were processed and examined histologically. The clinical appearance during weeks 7-12 varied from very poor to relatively good. Histologically, the implants showed a uniform inflammatory response. We found that all the tissue surrounding the screws showed signs of epithelial down growth. It was concluded that the two-stage implantation procedure of our prototype TS-TCs in this animal model was unsuccessful. Additional research efforts are necessary to improve tissue immobilization and to devise reliable fixation systems for TSVs

Science versus design; comparable, contrastive or conducive?

Science and design are two completely separated areas of expertise with their own specialists. Science analyses the existing world to create new knowledge, design uses existing knowledge to create a new world. This tunnel-vision mentality and narrow-minded approach is dangerous for problem solving, where a broad view on potential solutions is required to realise a high-quality answer on the defined problem. We state that design benefits from scientific methods, resulting in a more effective design process and in better products, while science benefits from a design approach, resulting in more efficient and effective results. Our philosophy is illustrated using examples from the field of biomedical engineering. Both methods can benefit tremendously from each other. By applying scientific methods, superior choices will be made in the design process. With design, more accurate, effective and efficient science will be performed.

The Saanen goat as an animal model for post-laryngectomy research:practical implications

A modem way of voice rehabilitation after total laryngectomy includes the use of shunt valves and tracheostoma valves. Problems of fixation to the surrounding tissue are a major drawback in the use of the shunt valve, heat and moisture exchange (HME) filters and, especially, the tracheostoma valve. To solve these problems different tissue connectors were developed. The main objective was to test the feasibility of these prototypes in a new animal model. Here we discuss the results, problems and complications of the selected Saanen goat model. In this prospective laboratory study, 19 healthy adult female Saanen goats (Capra hircus) were used and observed post-surgically for 12 weeks. Selection criteria such as comparable anatomy to humans and easy handling were used for animal model development. Also a literature search using the Medline and the ISI Web of Science databases was performed. The anatomy of the Saanen goat was investigated in a separate postmortem study. Surgery consisted of a laryngotracheal separation and implantation of a tracheo-oesophageal and tracheostoma tissue connector with fibrin tissue glue. Postoperative care consisted of frequent stoma care, monitoring appetite, weight, vital signs and administration of antibiotics, analgesics and mucolytic agents. All animals survived the surgical procedure. However, postoperative care was extensive, labour intensive and was accompanied by several complications. Eleven animals died spontaneously before the end of the experiment. The tracheostoma tissue connector caused signs of local infection in all cases. There was no evidence of infection around the tracheo-oesophageal tissue connector in 18 cases. It was concluded that the use of goats in this tracheostoma model was associated with major complications and should, therefore, only be used for short-term experiments with intensive care. Additional research is needed to see if clinical application of the tissue connectors is possible in the future