1. Abstract
Figure 1. X-Ray PLIF View With Polaxial Screws
PLIF(Posterior Lumbar Interbody Fusion) cages are one of the most important implants in medical which are using in degenerative disc disease. Therefore, many different designs have been developed about PLIF implants by many medical companies, such as Synthes, Globus, Zimmer, etc. The various tests are applied to these implants before they do not implant the patient like the biomechanical test according to ISO or ASTM standard. The purpose of this article is not to find the best design. The information obtained during this analysis will be evaluated, not the result of the analysis(partially).
2. Design
Figure 2. Traditional PLIF Cages
Nearly all traditional implants have teeth above and bottom, different types of windows on the sides, a large hole in the middle, and a sharp bit. PLIF cages also have a thread for use with instruments. Such cases affect significantly the strength of PLIF cages. Let's look at our PLIF design.
Figure 3. Designed for FEA Analysis
While designing this prototype, traditional designs were taken as reference such as dimensions of the solid in 3 dimensions. It has 10mm width, 24mm length, and 7mm height. The other dimension or design shape/geometry is not based on any articles or references design such as side slots and teeth.
3. Analysis
Finite element analysis has been made six different types such as static compression, shear, etc. for the PLIF cage according to ASTM F2077 standard. -But I'll just discuss static and dynamic compression test results in this article and upload the other analysis result-. The teeth deleted from the PLIF cage while making FE analysis. Because they make it difficult to solve the analysis and Solving time is taking many times. Likewise, the thread for the instrument was deleted from the minor diameter.
Figure 4. Removed Teeth design
3.1. Static Compression Test
The PLIF cage was placed between two iron block solid models as you can see in figure 5. Iron block material was selected X65CrMo17 Hardened&Temp Stainless Steel. The surfaces of these iron blocks in contact with the PLIF cage are anatomically shaped so that they fit partially into the PLIF cage. If test apparatus are not shaped anatomically, stress will be concentrated too small area so the PLIF cage lifetime will be decreased avoidance of doubt.
| Stress(MPa) | |
| Von Mises | |
| Shear | |
| Pricipable |
3.2 Dynamic Compression Test
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